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Biomedical subjects

J Tanji

Publications and source records attributed to J Tanji.

At least 91 records · Page 5Linked to original sources
PubMed1981

Supplementary and precentral motor cortex: contrast in responsiveness to peripheral input in the hindlimb area of the unanesthetized monkey.

Single-unit recording and intracortical microstimulation techniques have been employed in unanesthetized monkeys in order to ascertain the relative responsiveness of the supplementary motor cortex (MII) and the precentral motor cortex (MI) to a controlled peripheral stimulus. The hindlimb representation was explored to facilitate comparison of MI and MII sensitivity in the same animal. Two main findings have emerged: (i) Many fewer neurons in MII respond to the peripheral stimulus and those that do have much weaker responses than neurons in MI. (ii) The hindlimb representation of MII and the tail representation of MI appear to be considerably further rostral than depicted in the classical maps. The latter finding serves to resolve a discrepancy between the classical physiological and cytoarchitectonic maps for this region of cortex.

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PubMed1981

Submodality distribution in sensorimotor cortex of the unanesthetized monkey.

1. Neuronal responses to cutaneous and noncutaneous stimulation were examined in the hindlimb representation of the precentral motor cortex (MI) and the first somatosensory cortex (SI) of unanesthetized monkeys. 2. MI can be divided into two distinct parts of the basis of its afferent input. The rostral part receives predominantly noncutaneous inputs, while the cutaneous input is primarily confined to the caudal part of MI. Thus, a differential distribution of submodality groups exists in the MI cortex. Caudal to MI, area 3a responds mainly to stimulation of noncutaneous receptors, in marked contrast to the caudal part of MI or area 3b. 3. The finding of a differential distribution of cutaneous inputs within MI is of significance a) to hypotheses concerning the role of somatosensory input to the MI cortex, b) to studies that attempt to characterize somatosensory inputs to MI by the proportion of neurons responsive to cutaneous and noncutaneous stimulation, and c) in that they confirm and extend similar findings recently reported for the forelimb representation of an anesthetized New World monkey (43).

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PubMed1981

Neuronal responses in sensorimotor cortex to ramp displacements and maintained positions imposed on hindlimb of the unanesthetized monkey.

1. Neuronal responses to passively imposed displacements of the foot were examined in area 3a, the precentral motor cortex (MI), and the first somatic sensory cortex (SI) of unanesthetized monkeys. The foot displacements, in the form of "ramps" and maintained displacements, were applied at several different velocities and achieved a number of maintained positions. The response in relation to the ramp was termed a "dynamic" response, while that in association with the maintained displacement was termed a "static" response. 2. Units in the rostral part of MI (MI/r) and in area 3a usually responded in relation both the ramps and to maintained displacements. The activity of the majority of area 3a and MI/r units was strongly modulated only during ramps of one direction. Such response properties contrast with those observed in the caudal part of MI (MI/c) and areas 3b and 1 of SI, where most units responded in relation to the ramp phase of the displacement in both of two ramp directions and not to the maintained displacements. 3. Virtually all units, including those in MI, displayed a dynamic response. However, the dynamic response amplitude of area 3a neurons greatly exceeded that of MI units for equal velocities of displacement. 4. For area 3a units, peak neuronal activity was well correlated with ramp velocity over the range examined. Such units were a minority in areas 3b and 1 of SI (excluding area 3a) and MI. 5. Most area 3a units and almost half of MI/r units displayed, in addition to a dynamic response, a static response that reflected foot position. MI units were more sensitive than area 3a units to equal degrees of maintained displacement. 6. These results demonstrate that in the unanesthetized, intact animal, responses of most neurons in area 3a and MI fall into two categories: a) mixed dynamic-static responses resembling those of muscle spindle afferents, and b) purely dynamic responses. These data are consistent with the hypothesis that afferent input concerning the velocity and position of a segment of a limb may have a role in cortically mediated regulation of movement and posture, and that both areas 3a and the MI cortex may be directly involved in this regulation. 7. The cytoarchitectonic characteristics of area 3a, as defined in single-unit studies, are discussed. It is argued that the salient characteristic of area 3a in the primate is a thinned internal granular layer (layer IV) that contrasts with the heavily granular area 3b and the agranular area 4.

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PubMed1980

Supplementary motor area: neuronal response to motor instructions.

1. Single-unit recordings were obtained from the supplementary motor area of the cerebral cortex of two monkeys during execution of learned movements 2. Monkeys were required to push or pull a cast attached to the right forelimb in response to a sudden perturbation delivered via the cast. An instruction as to the direction of the monkey's movement was delivered 2.5--5 s prior to the occurrence of the perturbation and correct performance, therefore, required the animal to develop a preparatory state prior to the perturbation. 3. Of many hundreds of neurons recorded, 201 exhibited instruction-induced changes of activity during the period intervening between the instruction and the perturbation-triggered movement. 4. In 94 neurons, effects of the instruction were differential depending on which of the two instructions was given, whereas in 107 neurons, effects were nondifferential. The latencies of the differential responses appeared to be shorter (starting as early as 140 ms after the instruction). 5. The magnitude of the instruction effects varied in parallel with development of enhanced motor skill as the monkeys gained more experience in responding to the triggering stimulus. 6. These observations substantiate the hypothesis that the supplementary motor area plays a part in modifying a sensory-triggered motor output.

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PubMed1979

Neuronal activity in the cortical supplementary motor area related with distal and proximal forelimb movements.

Monkeys were trained to perform two different motor acts, one involving muscle activity in distal forelimb muscles and the other in proximal forelimb and shoulder girdle muscles. After confirming spatial and temporal dissociation of muscle activity in the two motor acts, single unit activity in the supplementary motor area (SMA) was recorded. SMA neurons related with the distal and proximal forelimb movements were found to be arranged rostrocaudally with a considerable overlap. In the overlapping region, neurons related with the distal movement were located more deeply.

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PubMed1978

Does the supplementary motor area play a part in modifying motor cortex reflexes?

Neuronal activity in the supplementary motor area was recorded from a monkey performing a trained motor task that required readiness for proper usage of sensory inputs. Thirty-two neurons exhibited activity changes, which supports the hypothesis that the SMA is part of the system involved in modulating responsiveness of the motor cortex to sensory inputs in association with learned movements.

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PubMed1976

Anticipatory activity of motor cortex neurons in relation to direction of an intended movement.

1. Monkeys were trained to 1) hold a handle in a central zone midway between "push" and "pull" while awaiting 2) an instruction telling them how to respond to a subsequent 3) perturbation, which triggered the instructed movement and was followed by 4) a reward if the movement was correct. 2. There were two sorts of instructions: push and pull. When the pull instruction had preceded the perturbation, the monkey responded to the perturbation by pulling, whereas after a push instruction, the monkey responded to the perturbation by pushing. 3. Recordings in pre- and postcentral sensorimotor cortex revealed instruction-induced changes of neuronal activity during the period intervening between the instruction and the perturbation-triggered movement. Effects of the instruction were differential depending on which of the two instructions was given, such differential responses to the instruction being detected in 61% of precentral pyramidal tract neurons (PTNs), 44% of precentral non-PTNs, and 11% of postcentral neurons. 4. Since motor cortex PTN axons end on alpha and gamma motoneurons and on interneurons of the spinal cord, changes of PTN activity with "intention" or "motor set" provide a mechanism for suprasegmental control and presetting of spinal cord reflex excitability specific to the nature of an impending movement.

Animals↗
PubMed1976

Reflex and intended responses in motor cortex pyramidal tract neurons of monkey.

1. Monkeys were trained to react to an arm perturbation according to an instruction delivered prior to the perturbation. There were two possible instructions (push or pull), and monkeys learned to respond accordingly regardless of the direction (push or pull) of the triggering perturbation. 2. Pyramidal tract neurons (PTNs) in contralateral motor cortex arm area responded to the triggering perturbation with two dissociable components: 1) a relatively short-latency (20-25 ms) reflex component which depended on the direction of the perturbation, and 2) a longer latency (40-50 ms) intended component which depended on the prior instruction. 3. Intended PTN discharge could occur in arm area with latencies of 50 ms even following arm perturbations whose initial reflex effects on the PTN were inhibitory. 4. Intended PTN responses triggered by perturbations of the appropriate body part occur at shorter latencies than intended PTN responses triggered by auditory or visual stimuli. These short-latency intended PTN responses may play a role in thsshort-latency but volitionally controlled limb movements occurring in response to limb perturbations.

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