Comprehensive Physiology Wiley Online Library
For Librarians For Authors Editors About

The Pyramidal Tract

Hiroshi Asanuma

10.1002/cphy.cp010215

Source: Supplement 2: Handbook of Physiology, The Nervous System, Motor Control

Originally published: 1981

Published online: January 2011

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Organization of Projection from Cerebral Cortex to Spinal Cord
1.1 Studies by Cortical Surface Stimulation
1.2 Studies by Cortical Depth Stimulation
1.3 Microstructure of Corticospinal Projection
1.4 Projection to γ‐Motoneurons
1.5 Projections to Spinal Interneurons
1.6 Pyramidal Collaterals and Branches Within Brain
2 Afferent Inputs to Motor Cortex and Pyramidal Tract Neurons
2.1 General Problems
2.2 Inputs From Nucleus Ventralis Lateralis of Thalamus
2.3 Peripheral Inputs to Motor Cortex and Pyramidal Tract Cells
2.4 Inputs Through Association Fibers
2.5 Inputs Through Commissural Fibers
3 Function of Pyramidal Tract
4 Summary
Figure 1. Figure 1.

A: Ferrier's historic map of motor representation of monkey brain 46. 1, Opposite hindlimb is advanced as in walking. 2, Flexion with outward rotation of thigh, rotation inward of leg, with flexion of toes. 3, Tail. 4, Opposite arm is adducted, extended, and retracted; hand pronated. 5, Extension forward of opposite arm; a, b, c, d, movements of fingers and wrists. 6, Flexion and spination of forearm. 7, Retraction and elevation of angle of mouth. 8, Elevation of ala of nose and upper lip. 9 and 10, Opening of mouth with protrusion, 9, and retraction, 10, of tongue. 11, Retraction of angle of mouth. 12, Eyes open widely, pupils dilate, and head and eyes turn to opposite side. 13 and 13′, Eyes move to opposite side. 14, Pricking of opposite ear, head and eyes turn to opposite side, pupils dilate widely. B: motor representation in brain of chimpanzee. Left hemisphere viewed from side and above to obtain best configuration of sulcus centralis area. Motor area indicated by stippling. Shaded regions, marked EYES, indicate portions of cortex that yield conjugate movements of eyeballs under faradization. S.F., superior frontal sulcus; S.Pr., superior precentral sulcus; I. Pr., inferior precentral sulcus.

A from Ferrier 46; B from Sherrington 137
Figure 2. Figure 2.

Diagrammatic representation of hypothetical distribution of pyramidal tract cells for individual muscles. Cell group for each muscle has focal distribution and overlapping fringe. Each symbol represents a pyramidal tract cell. Large concentric circles are spheres of excitation. Expected contraction of muscles to cortical stimulation at different strength shown by myograms in lower portion, in which magnitude of contraction is determined by number of pyramidal tract cells involved in sphere of excitation.

From Chang et al. 33
Figure 3. Figure 3.

Pyramidal tract responses (R) to stimulation (S) of motor cortex and white matter in monkey. Recording electrode in lateral column of spinal cord at first cervical segment. Downward deflection indicates positivity at electrode in pyramidal tract. Time: 1 ms. Direct (D) and indirect (I) waves present at left, whereas only D‐wave at right.

From Patton and Amassian 123
Figure 4. Figure 4.

Amplitude change of monosynaptic excitatory postsynaptic potentials (EPSPs) recorded in radial motoneuron of baboon. Amplitude plotted against distance from best point. Large curves, stimulus 1.3 mA; small curves, stimulus 0.75 mA; membrane potential —66 mV. Dotted line, points along line at right angles to Rolandic fissure; unbroken line, points parallel to Rolandic fissure. Upper right: points of stimulation around Rolandic fissure. Large circle, best point. Arcs show farthest limits of cell populations excited by stimuli applied at points of zero synaptic action on test motoneuron.

From Landgren et al. 87
Figure 5. Figure 5.

Area of origin of pyramidal tract cells projecting to a lateral gastrocnemius motoneuron in monkey. A, B: averaged records of postsynaptic potentials evoked from indicated electrode positions by 0.4 and 0.5 mA, respectively. C, D, E: comparison of total projection areas and areas from which largest excitatory postsynaptic potentials (EPSPs) were evoked at 0.4‐mA strength for illustrated lateral gastrocnemius motoneuron and for motoneurons to synergistic muscles (MG, medial gastrocnemius; PI, plantaris) and to antagonistic muscle (DP, deep peroneal).

From Jankowska et al. 75
Figure 6. Figure 6.

Composite figurine charts of precentral and supplementary motor areas of monkey brain derived from several experiments in which left cortex was mapped by systemic punctuate electrical stimulation. C, central sulcus; area between C and C' folds down to depth of sulcus. d, Medial edge of hemisphere; area between e and e' is supplementary motor area located on medial surface of hemisphere. Except for responses from points in ipsilateral motor face area (at extreme left), muscle responses are on right side of body. Strongest and earliest movements indicated in solid, intermediate in cross‐hatching, and weakest in stippling. Symbols with crosses on ankles indicate eversion of foot; symbols with open centers on hip and ankle signify adduction and inversion; curved lines with arrows designate rotation. e, Sulcus cinguli; i, inferior precentral sulcus.

From Woolsey et al. 163
Figure 7. Figure 7.

Distribution of potentials produced by antidromic activation of pyramidal tract neurons by stimulation of medullary pyramid in cat, A, and monkey, B. Potentials are not restricted to motor cortex.

From Woolsey and Chang 162
Figure 8. Figure 8.

Threshold changes for facilitation or inhibition of 4 spinal monosynaptie reflexes during insertion of stimulating microelectrode into cortex in cat (top right inset). Ordinates, threshold currents (μa) for just‐observable facilitation (upper graph) and inhibition (lower graph). Note that graphs symmetrically reach maximum current of 20 μa bordering hatched area, which indicates no effects with stimulation of 20 μa. EDL, extensor digitorum longus; ECU, extensor carpi ulnaris; ECR, extensor carpi radialis; EDC, extensor digitorum communis.

From Asanuma and Sakata 12
Figure 9. Figure 9.

Distribution of low‐threshold points for facilitation of monosynaptic reflexes in medianus pronator nerve (pronator of wrist). A: tracks that passed low‐threshold points of less than 20 μa. Each track number corresponds to surface position shown in B. Numbers along penetrations show threshold currents.

From Asanuma and Sakata 12
Figure 10. Figure 10.

Distribution of effective spots for producing thumb movements within depth of motor cortex. Effects examined at 100‐μm steps in each penetration. A: Examined with stimulating current of 5 μa. B: examined with 10 μa; ○, thumb flexion; □, thumb extention; •, thumb adduction; □, thumb abduction; —, spots of no effect.

From Asanuma and Rosén 10
Figure 11. Figure 11.

Descending volleys evoked by repetitive intracortical stimulation in monkey. A, F: antidromic potential from pyramidal tract cell. B–D, G–J: descending volleys evoked by increasing strength of stimulation at same electrode position as in A and F, recorded from lateral funiculus at L1–L2. J: intracortical stimulation with same strength as for D and I, but 300 μm deeper. Superimposed traces at left and corresponding averaged records at right. Amplitude of stimuli shown at right, and their timing on lower traces in D and J. Arrows indicate direct responses to cortical stimulation, negativity downward.

From Jankowska et al. 74
Figure 12. Figure 12.

Interconnections of some cell types in cerebral cortex. Two pyramidal cells shown in laminae 3 and 5. Specific afferent fiber (spec. aff.) shown to excite stellate cell (S1), the axon of which establishes cartridge‐type synapses on apical dendrites. Specific afferent fiber also excites stellate interneurons (S3) that give inhibition to pyramidal cells in adjacent cortical columns, indicated by shadings. Sp, stellate pyramidal cells; S2, short axon inhibitory cells in lamina 2; S5, S6, interneurons with ascending and descending axons.

From Szentágothai 149
Figure 13. Figure 13.

Terminal branches of pyramidal tract axons in lumbar cord of cat. Horizontal section cut slightly obliquely (inset diagram) showing relations of lateral corticospinal terminals (f1) to proprioneurons. Terminating corticospinal elements, c, project synaptically upon lateral dendrites and somata of propriospinal neurons d and e. At arrow, terminals from two different corticospinal fibers converge on same dendrite. Propriospinal neurons d and e project axons toward midline, m, and/or lateral propriospinal bundles, p, to form secondary terminals, f2.

From Scheibel and Scheibel 134
Figure 14. Figure 14.

Distribution of terminal branches of 4 pyramidal tract neurons in spinal cord. These 4 neurons recorded simultaneously through same cortical electrode. A: likely course of axonal branches summarized in 4 representative transverse planes. Each neuron represented by different line and symbol. B: areas of passage (open symbols) and termination (filled symbols) of axon collaterals in ventral horn in relation to motor nuclei identified by antidromically evoked potentials. Continuous bars, explored parts of spinal cord; dashed bars, unexplored areas; OTHER, those sites that histological examination indicated as ventral horn, but antidromic stimulation of isolated motor nerves did not identify nuclei. FDL, flexor digitorum longus; EDB, extensor digitorum brevis; EDL, extensor digitorum longus; PER, peroneus; LG, lateral gastrocnemius; MG, medial gastrocnemius; SOL, soleus; TIB, tibialis; L6, sixth lumbar segment; L7, seventh lumbar segment; S1, first sacral segment.

From Asanuma et al. 20
Figure 15. Figure 15.

Simplified diagram showing mode of pyramidal projection from motor cortex to spinal motor nuclei (MN). Group of pyramidal tract neurons located in small area of cortex project primarily to given motor nucleus, but some send axons to another motor nucleus and some send branches to more than one motor nucleus.
Figure 16. Figure 16.

Pyramidal effects on gastrocnemius‐so‐leus, G‐S, and deep peroneal, DP, monosynaptic reflexes. Reflexes were recorded simultaneously at two different sweep speeds. Upper traces, reflex discharges in ventral root; lower traces, potentials at dorsal root entry zone. A: unconditioned test reflex. B: effect of conditioning G‐S reflex with maximal group Ia volley in DP. C, D: effect of train of 6 stimuli to motor cortex on A and B. E‐H: repetition of same series after transection of pyramidal tract shown in inset.

From Lundberg and Voorhoeve 103
Figure 17. Figure 17.

Terminal intracortical domain generated by axon of single thalamic ventrolateral neuron shown in relation to large fifth‐layer pyramidal neuron. g, Gray matter‐white matter junction. Reconstruction at lower left shows single ventrolateral fiber system projecting onto pericruciate gyrus, pc. Two of these tridimensional plexuses are shown developing from same fiber via branch point, b; young kitten cortex. c, Cruciate sulcus; m, medial; 1, lateral.

From Scheibel and Scheibel, in Asanuma et al. 19
Figure 18. Figure 18.

Example of multimodal sensory inputs from small area in periphery to cortical column in cat. A: location of penetration on pericruciate cortex. Dotted line indicates sagittal plane of section. B: diagram of sagittal section and of radial penetration in gray matter. C: photomicrograph of part of section containing penetration. Figurines show peripheral receptive fields. Adequate stimuli to deep structures shown at left and those to the superficial structure shown at right.

From Welt et al. 159
Figure 19. Figure 19.

Afferent inputs converging into cortical efferent zone for palmar muscle. Of 8 penetrations, 4 passed through palmar zone, and 17 cells could be isolated within the zone. Six of 17 cells responded to natural stimulation of skin; receptive fields shown by figurines connected to cell locations by respective lines interrupted by penetration and cell number. These 6 neurons shared common receptive field on ventral surface of paw.

From Asanuma et al. 18
Figure 20. Figure 20.

Afferent inputs converging to thumb area of monkey motor cortex. Several penetrations passed through areas, which when stimulated produced extension, flexion, adduction, or abduction of thumb. Each area marked by symbols explained at lower right. Cortical sites from which movement could not be produced are shown by small bars on electrode tracks. Locations of isolated cells are indicated by dots, and are connected to descriptions of receptive fields and adequate stimuli by dotted lines. Filled areas on figurines are superficial receptive fields. UD, undriven cells.

From Rosén and Asanuma 133
Figure 21. Figure 21.

Thalamic neurons that transfer peripheral somesthetic inputs directly to motor cortex in cat. A: sagittal section of ventral thalamus showing electrode tracks and lesions. B: reconstruction of tracks from histological preparations. Short bars on tracks show locations of neurons with no receptive fields. Long bars at right are locations of neurons activated from skin receptors. Long bars at left are those activated from deep receptors. Circles indicate lesions made during experiment. Arrows indicate neurons activated antidromically from motor cortex. C: receptive fields of neurons shown in B. Solid areas indicate receptive fields for hair bending or light touch. Circles indicate deep receptive fields such as pressure or passive joint movement. Numbers on column correspond to track numbers, and each figurine corresponds to respective long bar on the track.

From Asanuma et al. 14
Figure 22. Figure 22.

Simplified diagram of connections between motor cortex (motor Cx) and periphery. Neurons in motor cortex are connected predominantly in radial direction and are subdivided into cortical efferent zones marked by hatched and dotted areas. Fringes of these efferent zones overlap with fringes of others, constituting overlapping mosaic within cortex. These efferent zones are intercalated with silent areas where threshold for motor effect is high. Corticospinal fibers from given efferent zone project most heavily to given motor nuclei to produce contraction of a muscle, but they also project to other motor nuclei to produce subliminal fringes of excitation. Afferent inputs originated by contraction of target muscle ascend spinal cord and project to original efferent zone directly through nucleus ventralis pars oralis, constituting a closed loop between cortex and periphery. This corticoperipheral loop circuit is well developed for distal limb muscles but is less clear for proximal muscles.


Figure 1.

A: Ferrier's historic map of motor representation of monkey brain 46. 1, Opposite hindlimb is advanced as in walking. 2, Flexion with outward rotation of thigh, rotation inward of leg, with flexion of toes. 3, Tail. 4, Opposite arm is adducted, extended, and retracted; hand pronated. 5, Extension forward of opposite arm; a, b, c, d, movements of fingers and wrists. 6, Flexion and spination of forearm. 7, Retraction and elevation of angle of mouth. 8, Elevation of ala of nose and upper lip. 9 and 10, Opening of mouth with protrusion, 9, and retraction, 10, of tongue. 11, Retraction of angle of mouth. 12, Eyes open widely, pupils dilate, and head and eyes turn to opposite side. 13 and 13′, Eyes move to opposite side. 14, Pricking of opposite ear, head and eyes turn to opposite side, pupils dilate widely. B: motor representation in brain of chimpanzee. Left hemisphere viewed from side and above to obtain best configuration of sulcus centralis area. Motor area indicated by stippling. Shaded regions, marked EYES, indicate portions of cortex that yield conjugate movements of eyeballs under faradization. S.F., superior frontal sulcus; S.Pr., superior precentral sulcus; I. Pr., inferior precentral sulcus.

A from Ferrier 46; B from Sherrington 137


Figure 2.

Diagrammatic representation of hypothetical distribution of pyramidal tract cells for individual muscles. Cell group for each muscle has focal distribution and overlapping fringe. Each symbol represents a pyramidal tract cell. Large concentric circles are spheres of excitation. Expected contraction of muscles to cortical stimulation at different strength shown by myograms in lower portion, in which magnitude of contraction is determined by number of pyramidal tract cells involved in sphere of excitation.

From Chang et al. 33


Figure 3.

Pyramidal tract responses (R) to stimulation (S) of motor cortex and white matter in monkey. Recording electrode in lateral column of spinal cord at first cervical segment. Downward deflection indicates positivity at electrode in pyramidal tract. Time: 1 ms. Direct (D) and indirect (I) waves present at left, whereas only D‐wave at right.

From Patton and Amassian 123


Figure 4.

Amplitude change of monosynaptic excitatory postsynaptic potentials (EPSPs) recorded in radial motoneuron of baboon. Amplitude plotted against distance from best point. Large curves, stimulus 1.3 mA; small curves, stimulus 0.75 mA; membrane potential —66 mV. Dotted line, points along line at right angles to Rolandic fissure; unbroken line, points parallel to Rolandic fissure. Upper right: points of stimulation around Rolandic fissure. Large circle, best point. Arcs show farthest limits of cell populations excited by stimuli applied at points of zero synaptic action on test motoneuron.

From Landgren et al. 87


Figure 5.

Area of origin of pyramidal tract cells projecting to a lateral gastrocnemius motoneuron in monkey. A, B: averaged records of postsynaptic potentials evoked from indicated electrode positions by 0.4 and 0.5 mA, respectively. C, D, E: comparison of total projection areas and areas from which largest excitatory postsynaptic potentials (EPSPs) were evoked at 0.4‐mA strength for illustrated lateral gastrocnemius motoneuron and for motoneurons to synergistic muscles (MG, medial gastrocnemius; PI, plantaris) and to antagonistic muscle (DP, deep peroneal).

From Jankowska et al. 75


Figure 6.

Composite figurine charts of precentral and supplementary motor areas of monkey brain derived from several experiments in which left cortex was mapped by systemic punctuate electrical stimulation. C, central sulcus; area between C and C' folds down to depth of sulcus. d, Medial edge of hemisphere; area between e and e' is supplementary motor area located on medial surface of hemisphere. Except for responses from points in ipsilateral motor face area (at extreme left), muscle responses are on right side of body. Strongest and earliest movements indicated in solid, intermediate in cross‐hatching, and weakest in stippling. Symbols with crosses on ankles indicate eversion of foot; symbols with open centers on hip and ankle signify adduction and inversion; curved lines with arrows designate rotation. e, Sulcus cinguli; i, inferior precentral sulcus.

From Woolsey et al. 163


Figure 7.

Distribution of potentials produced by antidromic activation of pyramidal tract neurons by stimulation of medullary pyramid in cat, A, and monkey, B. Potentials are not restricted to motor cortex.

From Woolsey and Chang 162


Figure 8.

Threshold changes for facilitation or inhibition of 4 spinal monosynaptie reflexes during insertion of stimulating microelectrode into cortex in cat (top right inset). Ordinates, threshold currents (μa) for just‐observable facilitation (upper graph) and inhibition (lower graph). Note that graphs symmetrically reach maximum current of 20 μa bordering hatched area, which indicates no effects with stimulation of 20 μa. EDL, extensor digitorum longus; ECU, extensor carpi ulnaris; ECR, extensor carpi radialis; EDC, extensor digitorum communis.

From Asanuma and Sakata 12


Figure 9.

Distribution of low‐threshold points for facilitation of monosynaptic reflexes in medianus pronator nerve (pronator of wrist). A: tracks that passed low‐threshold points of less than 20 μa. Each track number corresponds to surface position shown in B. Numbers along penetrations show threshold currents.

From Asanuma and Sakata 12


Figure 10.

Distribution of effective spots for producing thumb movements within depth of motor cortex. Effects examined at 100‐μm steps in each penetration. A: Examined with stimulating current of 5 μa. B: examined with 10 μa; ○, thumb flexion; □, thumb extention; •, thumb adduction; □, thumb abduction; —, spots of no effect.

From Asanuma and Rosén 10


Figure 11.

Descending volleys evoked by repetitive intracortical stimulation in monkey. A, F: antidromic potential from pyramidal tract cell. B–D, G–J: descending volleys evoked by increasing strength of stimulation at same electrode position as in A and F, recorded from lateral funiculus at L1–L2. J: intracortical stimulation with same strength as for D and I, but 300 μm deeper. Superimposed traces at left and corresponding averaged records at right. Amplitude of stimuli shown at right, and their timing on lower traces in D and J. Arrows indicate direct responses to cortical stimulation, negativity downward.

From Jankowska et al. 74


Figure 12.

Interconnections of some cell types in cerebral cortex. Two pyramidal cells shown in laminae 3 and 5. Specific afferent fiber (spec. aff.) shown to excite stellate cell (S1), the axon of which establishes cartridge‐type synapses on apical dendrites. Specific afferent fiber also excites stellate interneurons (S3) that give inhibition to pyramidal cells in adjacent cortical columns, indicated by shadings. Sp, stellate pyramidal cells; S2, short axon inhibitory cells in lamina 2; S5, S6, interneurons with ascending and descending axons.

From Szentágothai 149


Figure 13.

Terminal branches of pyramidal tract axons in lumbar cord of cat. Horizontal section cut slightly obliquely (inset diagram) showing relations of lateral corticospinal terminals (f1) to proprioneurons. Terminating corticospinal elements, c, project synaptically upon lateral dendrites and somata of propriospinal neurons d and e. At arrow, terminals from two different corticospinal fibers converge on same dendrite. Propriospinal neurons d and e project axons toward midline, m, and/or lateral propriospinal bundles, p, to form secondary terminals, f2.

From Scheibel and Scheibel 134


Figure 14.

Distribution of terminal branches of 4 pyramidal tract neurons in spinal cord. These 4 neurons recorded simultaneously through same cortical electrode. A: likely course of axonal branches summarized in 4 representative transverse planes. Each neuron represented by different line and symbol. B: areas of passage (open symbols) and termination (filled symbols) of axon collaterals in ventral horn in relation to motor nuclei identified by antidromically evoked potentials. Continuous bars, explored parts of spinal cord; dashed bars, unexplored areas; OTHER, those sites that histological examination indicated as ventral horn, but antidromic stimulation of isolated motor nerves did not identify nuclei. FDL, flexor digitorum longus; EDB, extensor digitorum brevis; EDL, extensor digitorum longus; PER, peroneus; LG, lateral gastrocnemius; MG, medial gastrocnemius; SOL, soleus; TIB, tibialis; L6, sixth lumbar segment; L7, seventh lumbar segment; S1, first sacral segment.

From Asanuma et al. 20


Figure 15.

Simplified diagram showing mode of pyramidal projection from motor cortex to spinal motor nuclei (MN). Group of pyramidal tract neurons located in small area of cortex project primarily to given motor nucleus, but some send axons to another motor nucleus and some send branches to more than one motor nucleus.



Figure 16.

Pyramidal effects on gastrocnemius‐so‐leus, G‐S, and deep peroneal, DP, monosynaptic reflexes. Reflexes were recorded simultaneously at two different sweep speeds. Upper traces, reflex discharges in ventral root; lower traces, potentials at dorsal root entry zone. A: unconditioned test reflex. B: effect of conditioning G‐S reflex with maximal group Ia volley in DP. C, D: effect of train of 6 stimuli to motor cortex on A and B. E‐H: repetition of same series after transection of pyramidal tract shown in inset.

From Lundberg and Voorhoeve 103


Figure 17.

Terminal intracortical domain generated by axon of single thalamic ventrolateral neuron shown in relation to large fifth‐layer pyramidal neuron. g, Gray matter‐white matter junction. Reconstruction at lower left shows single ventrolateral fiber system projecting onto pericruciate gyrus, pc. Two of these tridimensional plexuses are shown developing from same fiber via branch point, b; young kitten cortex. c, Cruciate sulcus; m, medial; 1, lateral.

From Scheibel and Scheibel, in Asanuma et al. 19


Figure 18.

Example of multimodal sensory inputs from small area in periphery to cortical column in cat. A: location of penetration on pericruciate cortex. Dotted line indicates sagittal plane of section. B: diagram of sagittal section and of radial penetration in gray matter. C: photomicrograph of part of section containing penetration. Figurines show peripheral receptive fields. Adequate stimuli to deep structures shown at left and those to the superficial structure shown at right.

From Welt et al. 159


Figure 19.

Afferent inputs converging into cortical efferent zone for palmar muscle. Of 8 penetrations, 4 passed through palmar zone, and 17 cells could be isolated within the zone. Six of 17 cells responded to natural stimulation of skin; receptive fields shown by figurines connected to cell locations by respective lines interrupted by penetration and cell number. These 6 neurons shared common receptive field on ventral surface of paw.

From Asanuma et al. 18


Figure 20.

Afferent inputs converging to thumb area of monkey motor cortex. Several penetrations passed through areas, which when stimulated produced extension, flexion, adduction, or abduction of thumb. Each area marked by symbols explained at lower right. Cortical sites from which movement could not be produced are shown by small bars on electrode tracks. Locations of isolated cells are indicated by dots, and are connected to descriptions of receptive fields and adequate stimuli by dotted lines. Filled areas on figurines are superficial receptive fields. UD, undriven cells.

From Rosén and Asanuma 133


Figure 21.

Thalamic neurons that transfer peripheral somesthetic inputs directly to motor cortex in cat. A: sagittal section of ventral thalamus showing electrode tracks and lesions. B: reconstruction of tracks from histological preparations. Short bars on tracks show locations of neurons with no receptive fields. Long bars at right are locations of neurons activated from skin receptors. Long bars at left are those activated from deep receptors. Circles indicate lesions made during experiment. Arrows indicate neurons activated antidromically from motor cortex. C: receptive fields of neurons shown in B. Solid areas indicate receptive fields for hair bending or light touch. Circles indicate deep receptive fields such as pressure or passive joint movement. Numbers on column correspond to track numbers, and each figurine corresponds to respective long bar on the track.

From Asanuma et al. 14


Figure 22.

Simplified diagram of connections between motor cortex (motor Cx) and periphery. Neurons in motor cortex are connected predominantly in radial direction and are subdivided into cortical efferent zones marked by hatched and dotted areas. Fringes of these efferent zones overlap with fringes of others, constituting overlapping mosaic within cortex. These efferent zones are intercalated with silent areas where threshold for motor effect is high. Corticospinal fibers from given efferent zone project most heavily to given motor nuclei to produce contraction of a muscle, but they also project to other motor nuclei to produce subliminal fringes of excitation. Afferent inputs originated by contraction of target muscle ascend spinal cord and project to original efferent zone directly through nucleus ventralis pars oralis, constituting a closed loop between cortex and periphery. This corticoperipheral loop circuit is well developed for distal limb muscles but is less clear for proximal muscles.

General References
 1. Asanuma, H. Recent developments in the study of the columnar arrangement of neurons within the motor cortex. Physiol. Rev. 55: 143–156, 1975.
 2. Brooks, V. B., and S. D. Stoney, Jr. Motor mechanisms: the role of the pyramidal system in motor control. Annu. Rev. Physiol. 33: 337–392, 1971.
 3. Henneman, E. Motor functions of the cerebral cortex. In: Medical Physiology (14th ed.), edited by V. B. Mountcastle. St. Louis: Mosby, 1980, vol. 1, pt. VII, p. 859–889.
 4. Patton, H. D., and V. E. Amassian. The pyramidal tract: its excitation and functions. In: Handbook of Physiology. Neurophysiology, edited by J. Field. Washington, DC: Am. Physiol. Soc., 1960, sect. I, vol. 2, p. 837–861.
 5. Phillips, C. G., and R. Porter. Corticospinal Neurons: Their Role in Movement. London: Academic, 1977.
 6. Wiesendanger, M. The pyramidal tract: recent investigations on its morphology and function. Ergeb. Physiol. 61: 73–135, 1969.
References
 1. Adrian, E. D., and G. Moruzzi. Impulses in the pyramidal tract. J. Physiol. London 97: 153–199, 1939.
 2. Albe‐Fessard, D., J. M. Besson, and M. Abdelmounene. Action of anesthetics on somatic evoked activities. In: Anesthesia and Neurophysiology, edited by H. Yamamura. Boston: Little, Brown, 1970, p. 129–158.
 3. Amassian, V. E. The use of contact placing in analytical and synthetic studies of the higher sensorimotor control system. In: Integration in the Nervous System, edited by H. Asanuma and V. J. Wilson. Tokyo: Igaku Shoin, 1979, p. 279–304.
 4. Amassian, V. E., and L. Berlin. Early cortical projection or group 1 afferents in the forelimb muscle nerves of cat. J. Physiol. London 143: 61, 1958.
 5. Amassian, V. E., and H. Weiner. Monosynaptic and polysynaptic activation of pyramidal tract neurons by thalamic stimulation. In: The Thalamus, edited by D. P. Purpura and M. D. Yahr. New York: Columbia Univ. Press, 1966, p. 255–282.
 6. Andersen, P., J. C. Eccles, and T. A. Sears. Cortically evoked depolarization of primary afferent fibers in the spinal cord. J. Neurophysiol. 27: 62–77, 1964.
 7. Andersen, P., P. J. Hagan, C. G. Phillips, and T. P. S. Powell. Mapping by microstimulation of overlapping projections from area 4 to motor units of the baboon's hand. Proc. R. Soc. London Ser. B 188: 31–60, 1975.
 8. Asanuma, H., and A. P. Arnold. Noxious effects of excessive currents used for intracortical microstimulation. Brain Res. 96: 103–107, 1975.
 9. Asanuma, H., and O. Okuda. Effects of transcallosal volleys on pyramidal tract cell activity of cat. J. Neurophysiol. 25: 198–208, 1962.
 10. Asanuma, H., and I. Rosén. Topographical organization of cortical efferent zones projecting to distal forelimb muscles in the monkey. Exp. Brain Res. 14: 243–256, 1972.
 11. Asanuma, H., and I. Rosen. Spread of mono‐ and polysynaptic connections within cat's motor cortex. Exp. Brain Res. 16: 507–520, 1973.
 12. Asanuma, H., and H. Sakata. Functional organization of a cortical efferent system examined with focal depth stimulation in cats. J. Neurophysiol. 30: 35–54, 1967.
 13. Asanuma, H., A. Arnold, and P. Zarzecki. Further study on the excitation of pyramidal tract cells by intracortical microstimulation. Exp. Brain Res. 26: 443–461, 1976.
 14. Asanuma, H., K. D. Larsen, and H. Yumiya. Somatosensory inputs from the thalamus to the motor cortex in the cat. Brain Res. 172: 217–228, 1979.
 15. Asanuma, H., K. D. Larsen, and H. Yumiya. Direct sensory pathways to the motor cortex in the monkey: a basis of cortical reflexes. In: Integration in the Nervous System, edited by H. Asanuma and V. J. Wilson. Tokyo: Igaku Shoin, 1979, p. 223–238.
 16. Asanuma, H., K. D. Larsen, and H. Yumiya. Peripheral input pathways to the monkey motor cortex. Exp. Brain Res. 38: 349–355, 1980.
 17. Asanuma, H., K. D. Larsen, and P. Zarzecki. Peripheral input pathways projecting to the motor cortex in the cat. Brain Res. 172: 197–208, 1979.
 18. Asanuma, H., S. D. Stoney, Jr., and C. Abzug. Relationship between afferent input and motor outflow in cat motorsensory cortex. J. Neurophysiol. 31: 670–681, 1968.
 19. Asanuma, H., J. Fernandes, M. E. Scheibel, and A. B. Scheibel. Characteristics of projections from the nucleus ventralis lateralis to the motor cortex in the cats: an anatomical and physiological study. Exp. Brain Res. 20: 315–330, 1974.
 20. Asanuma, H., P. Zarzecki, E. Jankowska, T. Hongo, and S. Marcus. Projection of individual pyramidal tract neurons to lumbar motoneuron pools of the monkey. Exp. Brain Res. 34: 73–89, 1979.
 21. Bard, P. Studies on the cortical representation of somatic sensibility. Bull. NY Acad. Med. 14: 585–607, 1938.
 22. Bernard, C. G., and E. Bohm. Cortical representation and functional significance of the corticomotoneuronal system. Arch. Neurol. Psychiatry 72: 473–502, 1954.
 23. Blum, B., L. M. Halpern, and A. A. Ward, Jr. Microelectrode studies of the afferent connections and efferent projections of neurons in the sensorimotor cortex of the cat. Exp. Neurol. 20: 156–173, 1968.
 24. Brinkman, J., B. M. Bush, and R. Porter. Deficient influences of peripheral stimuli on precentral neurons in monkeys with dorsal column lesions. J. Physiol. London 276: 27–48, 1978.
 25. Brodal, A. Neurological Anatomy (2nd ed.). London: Oxford Univ. Press, 1969.
 26. Brooks, V. B., and H. Asanuma. Recurrent effects following stimulation of medullary pyramid. Arch. Hal. Biol. 103: 247–278, 1965.
 27. Brooks, V. B., P. Rudomin, and C. L. Slayman. Sensory activation of neurons in the cat's cerebral cortex. J. Neurophysiol. 24: 286–301, 1961.
 28. Brooks, V. B., P. Rudomin, and C. L. Slayman. Peripheral receptive fields of neurons in the cat's cerebral cortex. J. Neurophysiol. 24: 302–325, 1961.
 29. Brown, M. C., I. Engberg, and P. B. C. Mathews. The relative sensitivity to vibration of muscle receptors in the cat. J. Physiol. London 192: 773–800, 1967.
 30. Bucy, P. C., R. Ladpli, and A. Ehrlich. Destruction of the pyramidal tract in the monkey. The effects of bilateral section of the cerebral peduncles. J. Neurosurg. 25: 1–23, 1966.
 31. Burke, R. E., P. L. Strick, K. Kanda, C. C. Kin, and B. Walmsley. Anatomy of medial gastrocnemius and soleus motor nuclei in cat spinal cord. J. Neurophysiol. 40: 667–680, 1977.
 32. Buser, P., and M. Imbert. Sensory projections to the motor cortex in cats. In: Sensory Communication, edited by W. A. Rosenblith. New York: Wiley, 1961, p. 607–626.
 33. Chang, H‐T., T. C. Ruch, and A. A. Ward, Jr. Topographical representation of muscles in motor cortex of monkeys. J. Neurophysiol. 10: 39–56, 1947.
 34. Clough, J. F. M., C. G. Phillips, and J. D. Sheridan. The short latency projection from the baboon's motor cortex to fusimotor neurons of the forearm and hand. J. Physiol. London 216: 257–279, 1971.
 35. Colonnier, M. L. The structural design of the neocortex. In: Brain and Conscious Experience, edited by J. C. Eccles. New York: Springer‐Verlag, 1966, p. 1–23.
 36. Coulter, J. D., L. Ewing, and C. Carter. Origin of primary sensorimotor cortical projection to lumbar spinal cord of cat and monkey. Brain Res. 103: 366–372, 1976.
 37. Denny‐Brown, D. The Cerebral Control of Movement. Springfield, IL: Thomas, 1966.
 38. Eklund, G., and K‐E. Hagbarth. Normal variability of tonic vibration reflexes in man. Exp. Neurol. 16: 80–92, 1966.
 39. Elger, C. E., E.‐J. Speckman, H. Caspers, and R. W. C. Janzen. Cortico‐spinal connections in the rat. I. Monosynaptic and polysynaptic responses of cervical motoneurons to epicortical stimulation. Exp. Brain Res. 28: 385–404, 1977.
 40. Endo, K., T. Araki, and N. Yagi. The distribution and pattern of axon branching of pyramidal tract cells. Brain Res. 57: 484–491, 1973.
 41. Evarts, E. V. Representation of movements and muscles by pyramidal tract neurons of the precentral motor cortex. In: Neurophysical Basis of Normal and Abnormal Motor Activities, edited by D. P. Purpura and M. D. Yahr. Hewlett, NY: Raven, 1967, p. 215–251.
 42. Evarts, E. V. Motor cortex reflexes associated with learned movements. Science 179: 501–503, 1973.
 43. Evarts, E. V. Activity of thalamic and cortical neurons in relation to learned movement in the monkey. Int. J. Neurol. 8: 321–326, 1971.
 44. Evarts, E. V., and J. Tanji. Gating of motor cortex reflexes by prior instruction. Brain Res. 71: 479–494, 1974.
 45. Ferrier, D. Experiments on the brain of monkeys. Proc. R. Soc. London 23: 409–430, 1875.
 46. Ferrier, D. The Functions of the Brain. London: Smith, Elder, 1876.
 47. Fetz, E. E. Pyramidal tract effects on interneurons in the cat lumbar dorsal horn. J. Neurophysiol. 31: 69–80, 1968.
 48. Fetz, E. E., and P. D. Cheney. Muscle fields of primate corticomotoneuronal cells. J. Physiol. Paris 74: 239–245, 1978.
 49. Fetz, E. E., P. D. Cheney, and D. C. German. Corticomotoneuronal connections of precentral cells detected by post‐spike averaging of EMG activity in behaving monkeys. Brain Res. 114: 505–510, 1976.
 50. Fidone, S. J., and J. B. Preston. Patterns of motor cortex control of flexor extensor cat fusimotor neurons. J. Neurophysiol. 32: 103–115, 1969.
 51. Foerster, O. Schlaffe und spastische Lämung. In: Handbuch der Normalen und Pathologishen Physiologic edited by A. Bethe, G. V. Bergman, G. Embden, and A. Ellinger. Berlin: Springer‐Verlag, 1927, p. 900–901.
 52. Forssberg, H., S. Grillner, and A. Sjöström. Tactile placing reactions in chronic spinal kittens. Acta Physiol. Scand. 92: 114–120, 1974.
 53. Fritsch, G., and E. Hitzig. Ueber die elektrische Erregbarkeit des Grosshirns. Arch. Anat. Physiol. Wiss. Med. 37: 300–332, 1870.
 54. Futami, T., Y. Shinoda, and J. Yokota. Spinal axon collaterals of corticospinal neurons identified by intracellular injection of horseradish peroxidase. Brain Res. 164: 279–284, 1979.
 55. Gatter, K. C., and T. P. S. Powell. The intrinsic connections of the cortex of area 4 of the monkey. Brain 101: 513–541, 1978.
 56. Ghez, C., and Y. Shinoda. Spinal mechanisms of the functional stretch reflex. Exp. Brain Res. 32: 55–68, 1978.
 57. Gordon, G., and R. Miller. Identification of cortical cells projecting to the dorsal column nuclei of the cat. Q. J. Exp. Physiol. 54: 85–98, 1969.
 58. Grant, G., S. Landgren, and H. Silfvenius. Columnar distribution of U‐fibers from the postcruciate cerebral projection area of the cat's group I muscle afferents. Exp. Brain Res. 24: 57–74, 1975.
 59. Grigg, P., and J. B. Preston. Baboon flexor and extensor fusimotor neurons and their modulation by motor cortex. J. Neurophysiol. 34: 428–436, 1971.
 60. Groos, W. P., L. K. Ewing, C. M. Carter, and J. D. Coulter. Organization of corticospinal neurons in the cat. Brain Res. 143: 393–419, 1978.
 61. Hammond, P. H. The influence of prior instruction to the subject on an apparently involuntary neuromuscular response. J. Physiol. London 132: 17, 1956.
 62. Hammond, P. H. Experimental study of servo action in human muscular control. Proc. HI Int. Congr. Med. Elect. London. 1960, p. 190–191. (Inst. Electr. Eng.).
 63. Hassler, R., and K. Muhs‐Clement. Architektonisher Aufbau der sensomotorischen und parietalen Cortex der Katze. J. Hirnforsch. 6: 377–420, 1964.
 64. Hepp‐Reymond, M.‐C., and M. Wiesendanger. Unilateral pyramidotomy in monkeys; effect on force and speed of a conditioned precision grip. Brain Res. 36: 117–131, 1972.
 65. Hepp‐Reymond, M.C., E. Trouche, and M. Wiesendanger. Effects of unilateral and bilateral pyramidotomy on a conditioned rapid precision grip in monkeys (Macaca fasci‐cularis). Exp. Brain Res. 21: 519–527, 1974.
 66. Hern, J. E. C., S. Landgren, C. G. Phillips, and R. Porter. Selective excitation of corticofugal neurones by surface‐anodal stimulation of the baboon's motor cortex. J. Physiol. London 161: 73–90, 1962.
 67. Hern, J. E. C., C. G. Phillips, and R. Porter. Electrical thresholds of unimpaled corticospinal cells in the cat. Q. J. Exp. Physiol. 47: 134–140, 1962.
 68. Hess, R., K. Negishi, and O. Creutzfeldt. The horizontal spread of intracortical inhibition in the visual cortex. Exp. Brain Res. 22: 415–419, 1975.
 69. Hines, M. Significance of the precentral motor cortex. In: The Precentral Motor Cortex, edited by P. C. Bucy. Urbana: Univ. of Illinois Press, 1944, p. 461–494.
 70. Hubel, D. H., and T. N. Wiesel. Shape and arrangement of columns in cat's striate cortex. J. Physiol. London 165: 559–568, 1963.
 71. Humphrey, D. R., and W. S. Corrie. Properties of pyramidal tract neuron system within a functionally defined subregion of primate motor cortex. J. Neurophysiol. 41: 216–243, 1978.
 72. Humphrey, D. R., and R. R. Rietz. Cells of origin of corti‐corubral projections from the arm area of the primate motor cortex and their synaptic actions in the red nucleus. Brain Res. 110: 162–169, 1976.
 73. Jabbur, S. J., and A. L. Towe. Cortical excitation of neurons in dorsal column nuclei of cat, including an analysis of pathways. J. Neurophysiol. 24: 499–509, 1961.
 74. Jankowska, E., Y. Padel, and Y. Tanaka. The mode of activation of pyramidal cells by intracortical stimuli. J. Physiol. London 249: 617–636, 1975.
 75. Jankowska, E., Y. Padel, and R. Tanaka. Projections of pyramidal tract cells to α‐motoneurons innervating hindlimb muscles in the monkey. J. Physiol. London 249: 637–669, 1975.
 76. Jones, E. G., J. D. Coulter, and H. Burton. Cells of origin and terminal distribution of corticostriatal fibers arising in the sensory‐motor cortex of monkeys. J. Comp. Neurol. 173: 53–80, 1977.
 77. Jones, E. G., J. D. Coulter, and S. H. C. Hendry. Intracortical connectivity of architechtonic fields in the somatic sensory, motor, and parietal cortex of monkeys. J. Comp. Neurol. 181: 291–348, 1978.
 78. Jones, E. G., and T. P. S. Powell. The ipsilateral cortical connections of the somatic sensory area in the cat. Brain Res. 9: 71–94, 1968.
 79. Jones, E. G., and T. P. S. Powell. The commisural connections of the somatic sensory cortex in the cat. J. Anat. 103: 433–455, 1968.
 80. Jones, E. G., and T. P. S. Powell. Connections of the somatic sensory cortex of the rhesus monkey. I. Ipsilateral cortical connections. Brain 92: 477–502, 1969.
 81. Kitai, S. T., J. D. K'ocsis, and J. Wood. Origin and characteristics of the cortico‐caudate afferents: an anatomical and electrophysiological study. Brain Res. 118: 137–141, 1976.
 82. Knapp H. E., E. Taub, and A. J. Berman. Movements in monkeys with deafferented forelimbs. Exp. Neurol. 7: 305–315, 1963.
 83. Koeze, T. H., C. G. Phillips, and J. D. Sheridan. Thresholds of cortical activation of muscle spindles and motoneurons of the baboon's hand. J. Physiol. London 195: 419–449, 1968.
 84. Kuypers, H. G. J. M. Central cortical projections to motor and somatosensory cell groups. Brain 83: 161–184, 1960.
 85. Kuypers, H., and J. Brinkman. Precentral projections to different parts of the spinal intermediate zone in the rhesus monkey. Brain Res. 24: 29–48, 1970.
 86. Kwan, H. C., W. A. MacKay, J. T. Murphy, and Y. C. Wong. Spatial organization of precentral cortex in awake primates. II. Motor outputs. J. Neurophysiol. 41: 1120–1131, 1978.
 87. Landgren, S., C. G. Phillips, and R. Porter. Cortical fields of origin of the monosynaptic pyramidal pathways to some alpha motoneurons of the baboon's hand and forearm. J. Physiol. London 161: 112–125, 1962.
 88. Larsen, K. D., and H. Asanuma. Thalamic projections to the feline motor cortex studied with horseradish peroxidase. Brain Res. 172: 209–215, 1979.
 89. Lassek, A. M. The pyramidal tract: basic considerations of corticospinal neurons. Res. Publ. Assoc. Res. Nerv. Ment. Dis. 27: 106–128, 1948.
 90. Laursen, A. M. Selective increase in choice latency after transsection of a pyramidal tract in monkeys. Brain Res. 24: 544–545, 1970.
 91. Laursen, A. M., and M. Wiesendanger. Motor deficit after transection of a bulbar pyramid in the cat. Acta Physiol. Scand. 68: 118–126, 1966.
 92. Lawrence, D. G., and H. G. J. M. Kuypers. The functional organization of the motor system in the monkey. I. The effects of bilateral pyramidal lesions. Brain 91: 1–14, 1968.
 93. Lemon, R. N., and R. Porter. Afferent input to movement‐related precentral neurons in conscious monkeys. Proc. R. Soc. London Ser. B 194: 313–339, 1976.
 94. Lemon, R. N., and J. Van Der Burg. Short‐latency peripheral inputs to thalamic neurons projecting to the motor cortex in the monkey. Exp. Brain Res. 36: 445–462, 1979.
 95. Lemon, R. N., J. A. Hanby, and R. Porter. Relationship between the activity of precentral neurons during active and passive movements in conscious monkeys. Proc. R. Soc. London. Ser. B 194: 341–373, 1976.
 96. Liddell, E. G. T., and C. G. Phillips. Pyramidal section in the cat. Brain 67: 1–100, 1944.
 97. L'iu, C. N., and W. W. Chambers. An experimental study of the corticospinal system in the monkey (Macaca mulatto): the spinal pathways and preterminal distribution of degenerating fibers following discrete lesions of the pre‐ and postcentral gyri and bulbar pyramid. J. Comp. Neurol. 123: 257–284, 1964.
 98. Lloyd, D. P. C. The spinal mechanism of the pyramidal system in cats. J. Neurophysiol. 4: 525–546, 1941.
 99. Lorente de Nó, R. Cerebral cortex: architecture, intercortical connections, motor projection. In: Physiology of the Nervous System (3rd ed.), edited by J. F. Fulton. New York: Oxford Univ. Press, 1949, p. 274–298.
 100. Lundberg, A. Integration in a propriospinal motor center controlling the forelimb in the cat. In: Integration in the Nervous System, edited by H. Asanuma and V. J. Wilson. Tokyo: Igaku Shoin, 1979, p. 47–64.
 101. Lundberg, A. Control of spinal mechanisms from the brain. In: The Nervous System, edited by D. B. Tower. New York: Raven, 1975, vol. 1, p. 253–265.
 102. Lungberg, A., U. Norrsell, and P. Voorhoeve. Pyramidal effects on lumbo‐sacral interneurons activated by somatic afferents. Acta Physiol. Scand. 56: 220–229, 1962.
 103. Lundberg, A., and P. Voorhoeve. Effects from the pyramidal tract on spinal reflex arcs. Acta Physiol. Scand. 56: 201–219, 1962.
 104. Malis, L. I., K. H. Pribram, and L. Kruger. Action potentials in “motor” cortex evoked by peripheral nerve stimulation. J. Neurophysiol. 16: 161–167, 1953.
 105. Marsden, C. D., P. A. Merton, and H. B. Morton. Servo action in human voluntary movement. Nature London 238: 140–143, 1972.
 106. Massion, J., and P. A. Albe‐Fessard. Activités évoquées chez le chat dans la région du nucleus ventralis lateralis par diverses stimulations sensorielles. I. Etude macrophysiologique. Electroencephalogr. Clin. Neurophysiol. 19: 433–451, 1965.
 107. Massion, J., and P. A. Albe‐Fessard. Activités évoquées chez le chat dans la région du nucleus ventralis lateralis par diverses stimulations sensorielles. II. Etude microphysiologique. Electroencephalogr. Clin. Neurophysiol. 19: 452–469, 1965.
 108. Massion, J., and L. Rispal‐Padel. Differential control of motor cortex and sensory areas on ventrolateral nucleus of the thalamus. In: Corticothalamic Projections and Sensory‐Motor Activities, edited by T. L. Frigyesi, E. Rinvic, and M. D. Yahr. New York: Raven, 1973, p. 357–374.
 109. Melvil‐Jones, G., and D. G. D. Watt. Observations on the control of stepping and hopping movements in man. J. Physiol. London 219: 709–727, 1971.
 110. Merton, P. A. Human position sense and sense of effort. Symp. Soc. Exp. Biol. 18: 387–400, 1964.
 111. Mortimer, E. M., and K. Akert. Cortical control and representation of fusimotor neurons. Am. J. Phys. Med. 40: 228–248, 1961.
 112. Mott, F. W., and C. S. Sherrington. Experiments upon the influence of sensory nerves upon movement and nutrition of the limb. Proc. R. Soc. London 57: 481–488, 1895.
 113. Mountcastle, V. B., P. W. Davies, and A. L. Berman. Response properties of neurons of cat's somatic sensory cortex to peripheral stimuli. J. Neurophysiol. 20: 374–407, 1957.
 114. Mountcastle, V. B., J. C. Lynch, A. Georgopoulos, H. Sakata, and C. Acuna. Posterior parietal association cortex of the monkey: command functions for operations within ex‐trapersonal space. J. Neurophysiol. 38: 871–908, 1975.
 115. Murphy, J. T., H. C. Kwan, W. A. MacKay, and Y. C. Wong. Spatial organization of precentral cortex in awake primates. III. Input‐output coupling. J. Neurophysiol. 41: 1132–1139, 1978.
 116. Murphy, J. T., Y. C. Wong, and H. C. Kwan. Distributed feedback systems for muscle control. Brain Res. 71: 495–505, 1974.
 117. Murphy, J. T., Y. C. Wong, and H. C. Kwan. Afferent‐efferent linkages in motor cortex for single forelimb muscles. J. Neurophysiol. 38: 990–1014, 1975.
 118. Nauta, W. H. J., and P. A. Gygax. Silver impregnation of degenerating axons in the central nervous system: a modified technique. Stain Tech. 29: 91–93, 1954.
 119. Nyberg‐Hansen, R., and A. Brodal. Sites of termination of corticospinal fibers in the cat. J. Comp. Neurol. 120: 369–391, 1963.
 120. Olszewski, J. The thalamus of the Macaca mulatta. Basel: Karger, 1952.
 121. Oscarsson, O., and I. Rosén. Projection to cerebral cortex of large muscle‐spindle afferents in forelimb nerves of the cat. J. Physiol. London 169: 924–945, 1963.
 122. Pandia, D. N., D. Gold, and T. Berger. Interhemispheric connections of the precentral motor cortex in the rhesus monkey. Brain Res. 15: 594–596, 1969.
 123. Patton, H. D., and V. E. Amassian. Single‐ and multiple‐unit analysis of cortical stage of pyramidal tract activation. J. Neurophysiol. 17: 345–363, 1954.
 124. Patton, H. D., and V. E. Amassian. The pyramidal tract: its excitation and functions. In: Handbook of Physiology. Neurophysiology, edited by H. W. Magoun. Washington, DC: Am. Physiol. Soc, 1960, sect. 1, vol. II, chapt. 34, p. 837–861.
 125. Penfield, W. The excitable cortex in conscious man. Liverpool: Liverpool Univ. Press, 1958.
 126. Phillips, C. G. Actions of antidromic pyramidal volleys on single Betz cells in the cat. Q. J. Exp. Physiol. 44: 1–25, 1959.
 127. Phillips, C. G. Cortical motor threshold and the thresholds and distribution of excited Betz cells in the cat. Q. J. Exp. Physiol. 41: 70–84, 1956.
 128. Phillips, C. G. Motor apparatus of the baboon's hand. Proc. R. Soc. London Ser. B 173: 141–174, 1969.
 129. Phillips, C. G., T. P. S. Powell, and M. Wiesendanger. Projection from low‐threshold muscle afferents of hand and forearm to area 3a of baboon's cortex. J. Physiol London 217: 419–446, 1971.
 130. Powell, T. P. S., and V. B. Mountcastle. Some aspects of the functional organization of the cortex of the postcentral gyrus of the monkey: a correlation of findings obtained in a single‐unit analysis with cvtoarchitecture. Johns Hopkins Hosp. Bull. 105: 133–162, 1959.
 131. Preston, J. B., M. C. Shende, and K. Uemura. The motor cortex‐pyramidal system: patterns of facilitation and inhibition on motoneurons innervation limb musculature of cat and baboon and their adaptive significance. In: Neurophysiological Basis of Normal and Abnormal Motor Activities, edited by D. H. Purpura and M. D. Yahr. Hewlett, NY: Raven, 1967, p. 61–72.
 132. Rexed, B. A cytoarchitectonic atlas of the spinal cord in the cat. J. Comp. Neurol. 100: 297–380, 1954.
 133. Romanes, G. J. The motor cell columns of the lumbo‐sacral spinal cord of the cat. J. Comp. Neurol. 94: 313–364, 1951.
 134. Rosén, I., and H. Asanuma. Peripheral afferent inputs to the forelimb area of the monkey motor cortex: input‐output relations. Exp. Brain Res. 14: 257–273, 1972.
 135. Scheibel, M. E., and A. B. Scheibel. Terminal axonal patterns in cat spinal cord. I. The lateral corticospinal tract. Brain Res. 2: 333–350, 1966.
 136. Sherrington, C. S. On secondary and tertiary degenerations in the spinal cord of the dog. J. Physiol. London 6: 177–191, 1885.
 137. Sherrington, C. S. On nerve‐tracts degenerating secondarily to lesions of the cortex cerebri. J. Physiol. London 10: 429–432, 1889.
 138. Sherrington, C. S. The Integrative Action of the Nervous System. New Haven, CT: Yale Univ. Press, 1906. Reprinted in 1947.
 139. Shinoda, Y., A. P. Arnold, and H. Asanuma. Spinal branching of corticospinal axons in the cat. Exp. Brain Res. 26: 215–234, 1976.
 140. Shinoda, Y., P. Zarzecki, and H. Asanuma. Spinal branching of pyramidal tract neurons in the monkey. Exp. Brain Res. 34: 59–72, 1979.
 141. Stephanis, C., and H. Jasper. Recurrent collateral inhibition in pyramidal tract neurons. J. Neurophysiol. 27: 855–877, 1964.
 142. Stoney, S. D. Jr., W. D. Thompson, and H. Asanuma. Excitation of pyramidal tract cells by intracortical micro‐stimulation: effective extent of stimulating current. J. Neurophysiol. 31: 659–669, 1968.
 143. Strick, P. L. Light microscopic analysis of the cortical projection of the thalmic ventrolateral nucleus in the cat. Brain Res. 55: 1–24, 1973.
 144. Strick, P. L. Anatomical analysis of ventrolateral thalamic input to primate motor cortex. J. Neurophysiol. 39: 1020–1031, 1976.
 145. Strick, P. L. Activity of ventrolateral thalamic neurons during arm movement. J. Neurophysiol. 39: 1032–1044, 1976.
 146. Strick, P. L., R. E. Burke, K. Kanda, C. C. Kim, and B. Walmsley. Differences between alpha and gamma motoneurons labeled with horseradish peroxidase by retrograde transport. Brain Res. 113: 582–588, 1976.
 147. Strick, P. L., and C. C. Kim. Input to primate motor cortex from posterior parietal cortex (area 5). I. Demonstration by retrograde transport. Brain Res. 157: 325–330, 1978.
 148. Strick, P. L., and J. B. Preston. Multiple representation in the primate motor cortex. Brain Res. 154: 366–370, 1978.
 149. Strick, P. L., and P. Sterling. Synaptic termination of the ventrolateral nucleus of the thalamus in the cat motor cortex. A light and electron microscope study. J. Comp. Neurol. 153: 77–106, 1974.
 150. Szentágothai, J. Architecture of the cerebral cortex. In: Basic Mechanisms of the Epilepsies, edited by H. Jasper, A. Ward, and A. Pope. Boston: Little, Brown, 1969.
 151. Takahashi, K., K. Kubota, and M. Uno. Recurrent facilitation in cat pyramidal cells. J. Neurophysiol. 30: 22–34, 1967.
 152. Tatton, E. G., S. D. Forner, G. L. Gerstein, W. W. Chambers, and C M. Liu. The effect of postcentral cortical lesions on motor responses to sudden upper limb displacements in monkeys. Brain Res. 96: 108–113, 1975.
 153. Thompson, E. D., S. D. Stoney, Jr., and H. Asanuma. Characteristics of projections from primary sensory cortex to motor‐sensory cortex in cats. Brain Res. 22: 15–27, 1970.
 154. Towe, A. L., H. D. Patton, and T. T. Kennedy. Response properties of neurons in the pericruciate cortex of the cat following electrical stimulation of the appendages. Exp. Neurol. 10: 325–344, 1964.
 155. Tower, S. S. Pyramidal lesion in the monkey. Brain 63: 36–90, 1940.
 156. Tsukahara, N., D. R. G. Fuller, and V. B. Brooks. Collateral pyramidal influences on the corticorubrospinal system. J. Neurophysiol. 31: 467–484, 1968.
 157. Vogt, V. A., and D. N. Pandya. Cortico‐cortical connections of somatic sensory cortex (areas 3, 1, and 2) in the rhesus monkey. J. Comp. Neurol. 177: 179–192, 1978.
 158. Walker, A. E. Internal structure and afferent‐efferent relations of thalamus. In: The Thalamus, edited by D. P. Purpura and M. D. Yahr. New York: Columbia Univ. Press, 1966, p. 1–12.
 159. Walshe, F. M. R. The mode of representation of movements in the motor cortex, with special reference to “convolusions beginning unilaterally.” Brain 66: 104–139, 1943.
 160. Welt, C., J. Aschoff, K. Kameda, and V. B. Brooks. Intracortical organization of cat's sensory motor neurons. In: Symposium on Neurophysiological Basis of Normal and Abnormal Motor Activities, edited by D. P. Purpura and M. D. Yahr. Hewlett, NY: Raven, 1967, p. 255–293.
 161. Wiesendanger, M. Input from muscle and cutaneous nerves of the hand and forearm to neurones of the precentral gyrus of baboons and monkeys. J. Physiol. London 228: 203–219, 1973.
 162. Woolsey, C. N. Organization of somatic sensory and motor areas of the cerebral cortex. In: Biological and Biochemical Bases of Behavior, edited by H. R. Harlow and C. N. Woolsey. Madison: Univ. of Wisconsin Press, 1958, p. 63–82.
 163. Woolsey, C. N., and H‐T. Chang. Activation of the cerebral cortex by antidromic volleys in the pyramidal tract. Res. Publ. Assoc. Res. Nerv. Ment. Dis. 27: 146–161, 1948.
 164. Woolsey, C. N., P. H. Settlage, D. R. Meyer, W. Sencer, T. P. Hamuy, and A. M. Travis. Pattern of localization in precentral and ‘supplementary' motor area and their relation to the concept of a premotor area. Res. Publ. Assoc. Res. Nerv. Ment. Dis. 30: 238–264, 1952.
 165. Zarzecki, P., Y. Shinoda, and H. Asanuma. Projection from area 3a to the motor cortex by neurons activated from group I muscle afferents. Exp. Brain Res. 33: 269–282, 1978.
 166. Zarzecki, P., P. L. Strick, and H. Asanuma. Input to primate motor cortex from posterior parietal cortex (area 5). II. Identification by antidromic activation. Brain Res. 157: 331–335, 1978.

Contact Editor

Submit a note to the editor about this article by filling in the form below.

* Required Field

Article Title: The Pyramidal Tract
 

How to Cite

Hiroshi Asanuma. The Pyramidal Tract. Compr Physiol 2011, Supplement 2: Handbook of Physiology, The Nervous System, Motor Control: 703-733. First published in print 1981. doi: 10.1002/cphy.cp010215