Lm. Schmid et al., VISUOTOPIC REORGANIZATION IN THE PRIMARY VISUAL-CORTEX OF ADULT CATS FOLLOWING MONOCULAR AND BINOCULAR RETINAL LESIONS, Cerebral cortex, 6(3), 1996, pp. 388-405
The effect of discrete monocular retinal lesions on the representation
of the visual field in the primary visual area (V1) was investigated
in adult cats. Lesions were created using argon lasers, 8 d to 41/2, m
onths prior to electrophysiological recording. This produced lesion pr
ojection zones (LPZs) in V1, 1.6-9.5 mm wide, that were deprived of th
eir normal input from one eye, but that received a normal input from t
he other eye, Nevertheless, at the majority of recording sites within
these zones neuronal responses were elicited by stimulation of the les
ioned eye, with receptive fields being displaced onto regions of retin
a surrounding the lesion, while receptive fields determined through st
imulation of the normal eye followed the normal visuotopic organizatio
n of V1. However, neuronal responses to stimulation of the lesioned ey
e within the LPZs were characterized by rapid habituation and unusuall
y low firing rates in comparison with responses to stimulation of the
normal eye, Stimulation of the normal eye temporarily masked the respo
nsiveness of neurons within the LPZ to stimulation of the lesioned eye
, The proportion of neurons responsive to stimulation of the lesioned
eye was higher just inside the borders of the LPZs than at the centers
of these zones. However, neurons responsive to stimulation of the tes
t eye were found up to 3.6 mm from the perimeter of the LPZs, and ther
efore the shifts in the visuotopic map caused by retinal lesions canno
t he explained solely on the basis of the normal scatter of receptive
fields and point-image size in V1. The proportion of cells responsive
to stimulation of the lesioned eye was highest in the infragranular la
yers, and lowest in the supragranular layers, By combining a restricte
d lesion of one eye with laser photocoagulation of the optic disc of t
he other eye, the effects of deactivation of the normal eye on the les
ion-induced visuotopic reorganization were also investigated. Neither
chronic nor acute deactivation produced any discernible further change
s in visuotopy or in the characteristics of neuronal responses to stim
ulation of the eye with the discrete lesions. Our findings show that t
he representations of the two eyes in adult visual cortex are capable
of independent reorganization, These findings parallel those of work i
n auditory cortex, suggesting that topographic reorganization in prima
ry sensory areas of adult cortex may be governed by similar mechanisms
.