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M C Hepp-Reymond

Publications and source records attributed to M C Hepp-Reymond.

32 records · Page 2Linked to original sources
PubMed1981

Eye and head movements to auditory targets.

Three adult female monkeys were trained to direct their gaze toward auditory targets. When the animals were free to move their heads about the vertical axis, this was accomplished with short-latency, coordinated eye-head movements reminiscent of responses to visual targets. The similarity of response to auditory and visual targets suggests a common motor program elicited by stimuli of different modalities. Since these modalities do not share the same reference system, this implies a remapping between the two reference systems.

Animals↗
PubMed1975

Relation of activity in precentral cortical neurons to force and rate of force change during isometric contractions of finger muscles.

The activity of single neurons within the hand area of the precentral motor cortex of primates was recorded during the performance of a maintained precision grip between the thumb and forefinger. The finger opposition forces were exerted against a strain gauge which allowed force changes to be studied under near isometric conditions. Task performance required the generation of a force ramp (the dynamic phase) and thereafter the maintenance of a stable force for one second (the static phase). Intracortical stimulation through the recording electrode was used to verify that the recordings were made from the appropriate somatotopographic area of the motor cortex. From a total of 221 recorded neurons, 76 were found to be either activated or deactivated during performance of the task. Among the 51 activated neurons, most discharged at higher frequencies during the dynamic phase, than during the static phase. The discharge of some of these neurons could be related to both force (F) and rate of force change (dF-dt) whereas certain others could only be correlated with dF-dt. The change in discharge frequency for these neurons generally occurred prior to the onset of EMG activity. Eight neurons were more active during maintained force than during the force ramp. The discharge frequency could not be correlated with dF-dt and only one showed a significant positive relation to force. The change in discharge frequency for these neurons either coincided or occurred after the onset of EMG activity.

Animals↗
PubMed1975

[Retrograde degeneration of the pyramidal cells in the motor cortex of apes (Macaca fascicularis)].

In three adult macaques the retrograde degeneration of cell bodies in the motor cortex was investigated 6 months after unilateral pyramidal tract section. Large and small Betz cells of the fifth layer were identified microscopically and counted. The analysis of the data reveals that after pyramidotomy, (1) contrary to our expectations from the extent of the pyramidal lesions, a surprising percentage of undegenerated Betz cells remains in the contralateral motor cortex, (2) a greater percentage of small rather than large cell survives, and (3) the greatest loss of cells is in the foot region, the smallest in the face region. The results are discussed in relation to the role of pyramidal axon collaterals in the survival of cell bodies, and the distinction between pyramidal cells and pyramidal tract cells.

Animals↗