The soma distribution of thalamic neurons projecting to a small circumscribed zone (diameter = 0.5-1.0 mm) strictly within cortical area 3a (in region of hand representation) filled out a "territory" traversing the dorsal half of the cytoarchitectonically defined thalamic nucleus, VPLc (abbreviations as in Olszewski [ 1952] The Thalamus of the Macaca mulatta.
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The responses of cortical neurons evoked by cutaneous stimulation were investigated in the hand representation of cortical area 3a in adult owl monkeys that had been trained in a tactile frequency discrimination task. This study demonstrates that there is a reorganization of the cutaneous and "deep" representation of hand in cortical area 3a, with the main change being an emergence of a large cutaneous representation and the parallel disappearance of a large part of the normal deep representation in this field. These changes are discussed in light of the possible functional roles of cortical area 3a..
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These findings suggest that muscle afferent information, thought to be important in a closed-loop mode of function, may reach primary motor cortex directly from cortical area 3a..
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The distributions of thalamic neurons projecting to the motor cortex and cortical area 3a were studied in cat by means of the retrograde double-labeling technique using Nuclear Yellow (NY) and Fast Blue (FB) as tracers.
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Neurons were recorded within forelimb and vestibular projection regions of cortical area 3a.
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For comparison, neurones of the primary receiving area for low-threshold muscle afferents, cortical area 3a, were also included in this study.
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Experiments in anaesthetized monkeys revealed that signals from stretch afferents reach neurons of the motor cortex, possibly via a relay in the cortical area 3a.
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