Maintenance of a somatotopic cortical map in the face of diminishing thalamocortical inputs
AUTOR(ES)
Jones, E. G.
FONTE
The National Academy of Sciences of the USA
RESUMO
This study addresses the extent of divergence in the ascending somatosensory pathways of primates. Divergence of inputs from a particular body part at each successive synaptic step in these pathways results in a potential magnification of the representation of that body part in the somatosensory cortex, so that the representation can be expanded when peripheral input from other parts is lost, as in nerve lesions or amputations. Lesions of increasing size were placed in the representation of a finger in the ventral posterior thalamic nucleus (VPL) of macaque monkeys. After a survival period of 1–5 weeks, area 3b of the somatosensory cortex ipsilateral to the lesion was mapped physiologically, and the extent of the representation of the affected and adjacent fingers was determined. Lesions affecting less than 30% of the thalamic VPL nucleus were without effect upon the cortical representation of the finger whose thalamic representation was at the center of the lesion. Lesions affecting about 35% of the VPL nucleus resulted in a shrinkage of the cortical representation of the finger whose thalamic representation was lesioned, with concomitant expansion of the representations of adjacent fingers. Beyond 35–40%, the whole cortical representation of the hand became silent. These results suggest that divergence of brainstem and thalamocortical projections, although normally not expressed, are sufficiently great to maintain a representation after a major loss of inputs from the periphery. This is likely to be one mechanism of representational plasticity in the cerebral cortex.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=23562Documentos Relacionados
- Impact of Persistent Cortical Activity (Up States) on Intracortical and Thalamocortical Synaptic Inputs
- Temporal binding via cortical coincidence detection of specific and nonspecific thalamocortical inputs: A voltage-dependent dye-imaging study in mouse brain slices
- Somatotopic organization in rat striatum: evidence for a combinational map.
- Relative numbers of cortical and brainstem inputs to the lateral geniculate nucleus
- Thalamocortical Connections of Parietal Somatosensory Cortical Fields in Macaque Monkeys are Highly Divergent and Convergent