Ma. Macneil et al., REWIRING OF TRANSCORTICAL PROJECTIONS TO MIDDLE SUPRASYLVIAN CORTEX FOLLOWING EARLY REMOVAL OF CAT AREA-17 AND AREA-18, Cerebral cortex, 6(3), 1996, pp. 362-376
Retrograde tracers were injected into middle suprasylvian (MS) cortex
of two groups of experimental adult cats that had incurred removal of
visual areas 17 and 18 on either the day of birth (P1), or at 1 month
of age (P28). Tracers were also injected into the same region of intac
t and adult ablated control cats. The locations and numbers of labeled
neurons in the experimental and control groups were compared. Followi
ng lesions on P1, but at no other age, increased numbers of neurons pr
ojected to MS cortex. Virtually all of the additional neurons were loc
ated in the superficial layers of the ventral posterior suprasylvian (
VPS) cortex. These results demonstrated that (1) neurons with ipsilate
ral transcortical axons have the potential to reconfigure their projec
tions after early, localized cortical damage elsewhere in the cortex o
f the same hemisphere; (2) this reconfiguration involves expansion of
specific projections and is not a generalized capacity of all cortical
neurons; (3) the expansion is modality specific; and, finally, (4) th
e ability of cortical neurons to reorganize projections is limited in
time. The expanded projection from vPS to MS cortex may contribute to
neuronal compensations and the sparing of visually guided behaviors pr
eviously demonstrated in cats with neonatal visual cortex damage, and
is a testament to the latent capacities immature cerebral cortical neu
rons possess to establish new projections following restricted damage
to the cerebral cortex early in life.