The Journal of Neuroscience, January 15, 2001, 21(2):615-627
Precise Burst Synchrony in the Superior Colliculus of the Awake
Cat during Moving Stimulus Presentation
Quentin
Pauluis1,
Stuart N.
Baker2, and
Etienne
Olivier1
1 Laboratory of Neurophysiology, School of Medicine,
Université Catholique de Louvain, B-1200 Brussels, Belgium, and
2 Department of Anatomy, Cambridge University, Cambridge,
United Kingdom CB2 3DY
This study aimed to characterize the synchrony that occurs between
cell discharges in the superior colliculus of the awake cat. We trained
cats to perform a visual fixation in the presence of a visual moving
stimulus and then recorded 686 pairs of neighboring cells in the
superior colliculus during task performance. A new method to assess the
significance of precise discharge synchronization is described, which
permits analysis of nonstationary data. Of 181 pairs with sufficient
data for quantitative analysis, 125 showed a cross-correlation
histogram (CCH) with features assessed as significant using this
approach. CCHs frequently showed an isolated central peak (41 of 125)
or a peak flanked by one or two troughs (68 of 125), and in a few cases
an oscillatory pattern of ~65 Hz (16 of 125). This is in contrast to
the oscillation frequency reported for the visual cortex and shows that
oscillations in the superior colliculus probably arise from a
cortex-independent mechanism.
Our method also permits direct quantification of the correlation shift
predictors, assessing precise time locking of spikes to the stimulus.
Only 1 of 125 cross-correlation shift predictors had a significant
central peak, meaning that most of the CCH features were not related to
cell discharges time-locked to the stimulus presentation.
Further investigation using a burst-jittering method showed that
synchrony in the superior colliculus is attributable to precise synchronization of short bursts of spikes. Such synchrony could be
related to the network dynamics and the common inhibitory feedback from
local interneurons, which would act as temporal selectors of the cells
with greatest or fastest response.
Key words:
correlation analysis; coincident event; fast
oscillations; spike; motion-processing; stimulus-locked responses
Copyright © 2001 Society for Neuroscience 0270-6474/01/212615-13$05.00/0