S. Molotchnikoff et al., STIMULUS-DEPENDENT OSCILLATIONS IN THE CAT VISUAL-CORTEX - DIFFERENCES BETWEEN BAR AND GRATING STIMULI, Brain research, 731(1-2), 1996, pp. 91-100
We have investigated the dependence of cortical oscillations on the ty
pe of visual stimulus. Single unit recordings were performed in areas
17 and 18 of the cat visual cortex. Among 217 cortical neurons oscilla
tions in the frequency range of 22-102 Hz were found in 29 cells (13%)
. The proportion of oscillating cells was higher (16%) if both bar and
grating stimuli were used to stimulate cortical neurons. It was found
that gratings are more effective than bars in triggering oscillatory
patterns in cortical cells. Among 21 oscillating cells which were stim
ulated with both bar and grating stimuli, oscillations evoked with gra
tings were found in 17 neurons (81%) while oscillations evoked with ba
r stimuli were triggered in 7 cells (33%). The distributions of oscill
ation frequencies were statistically different for oscillations evoked
with bars and gratings. Frequencies of oscillations evoked with bars
were in the lower and higher range than frequencies of oscillations ev
oked with gratings. In 3 cells (14%), rhythmic patterns could be evoke
d with both bar and grating stimuli. However, the oscillations were of
different frequencies. No significant correlation was found between t
he strength of oscillations and firing rate of cortical neurons. Both
simple and complex cells manifested the same dependence on stimulus ty
pe. However, complex cells mostly exhibited oscillations in the lower
frequency range while simple cells did so when neurons were stimulated
with bars. The results suggest that various classes of visual stimuli
can be coded by a temporal pattern of cortical responses.