P. Konig et al., SQUINT AFFECTS SYNCHRONIZATION OF OSCILLATORY RESPONSES IN CAT VISUAL-CORTEX, European journal of neuroscience, 5(5), 1993, pp. 501-508
As shown previously, neurons in various areas of the cat's visual cort
ex respond to appropriate visual stimuli with oscillatory activity in
the frequency range of 30-70 Hz. It has been suggested that synchroniz
ation of such responses serves to define assemblies of coherently acti
ve cells which represent individual visual objects. In this study, we
have investigated this putative binding mechanism in the visual cortex
of strabismic cats. We used six adult cats in which divergent squint
had been induced surgically at the age of 3 weeks. Multiunit activity
was recorded from area 17 with arrays of four or five closely spaced m
icroelectrodes. Subsequently, auto- and cross-correlation functions we
re computed for all spike trains. To quantify the oscillatory nature o
f the responses and the strength of synchronization between spatially
remote sites, damped sine wave functions were fitted to the correlogra
ms. Analysis of responses obtained from 202 recording sites showed tha
t the vast majority of cells had become monocular. Auto-correlation an
alysis revealed that the proportion of oscillatory firing patterns was
similar to that observed in normal cats. However, cross-correlation a
nalysis of 153 response pairs demonstrated that synchronization was re
duced significantly between cells dominated by different eyes while it
was as frequent and strong as in normal cats between cells dominated
by the same eye. These findings indicate that strabismus not only caus
es a reorganization of afferent inputs but also affects intracortical
interactions. Since strabismic cats lack tangential intracortical conn
ections between territories connected to different eyes and are unable
to combine signals conveyed by the two eyes these results support the
notion that response synchronization is achieved by cortico-cortical
connections and serves as a mechanism for feature binding.