Summary
Perception and cognition require the integration of feed-forward sensory information with feedback signals. Feed-forward and feedback signals have been associated with specific cortical laminae and specific oscillatory frequencies. We used stimuli of different sizes to isolate spectral signatures of feedforward and feedback signals, and their effect on communication between layers in primary visual cortex of male macaque monkeys. Small stimuli, centered on the neurons’ receptive fields elicited broad band gamma frequency oscillations predominantly in the superficial layers. These Granger causal originated in upper layer 4 and lower supragranular layers, in line with existing feed-forward models of oscillatory responses. However, large stimuli extending into the far surround of neurons’ receptive fields, generated strong narrow band gamma oscillatory activity across cortical layers. They Granger causal arose in layer 5, were conveyed through layer 6 to superficial layers, and violated existing models of feedback spectral signatures. Equally surprising, with large stimuli, alpha band oscillatory activity arose predominantly in granular and supragranular layers, and communicated in a feed-forward direction. This shows that oscillations in specific frequency bands can be dynamically modulated to serve feedback and feed-forward communication and are not restricted to specific cortical layers in V1
Competing Interest Statement
The authors have declared no competing interest.
