The Bernstein Center for Computational Neuroscience Freiburg

Announcement for the next
Informal Seminar
Dr. Junji Ito
Unit of Statistical Neuroscience
RIKEN Brain Science Institute
Wako-Shi, Japan

First spikes in V1 are phase locked to saccade-triggered LFP oscillations

Monday, October 13th, 2008
11:00 h TIME
Library (1st floor)
Bernstein Center
Hansastr. 9a
During natural vision, primates perform frequent saccadic eye movements, interleaved with fixations of an average duration of 200ms. During this short time interval, complex scene analysis is performed in the cortex. Individual neurons, however, can contribute only with a few spikes, suggesting that visual information processing is not only based on firing rates, but also relies on the precise timing of spikes. We explored this hypothesis in recordings from V1 of monkeys freely viewing natural images. In former work we have shown that spike synchrony between V1 neurons is tightly related to the early phase of fixations (Maldonado et al, 2008). Here we explore possible underlying mechanisms, and study the relation of individual spikes to the local field potential (LFP) simultaneously measured in V1. The LFP exhibits prominent beta-band oscillations that occur locked to the onset of saccades. The visually induced spiking activity during consecutive fixations is tighly related to the phase of the LFP oscillation. In particular, the very first spikes appear locked to a specific phase of this oscillation at about 60ms after fixation onset. These saccade-triggered LFP oscillations seem to serve as a mechanism to precisely modulate the timing of visually induced spikes, thereby providing the substrate for temporal coordination of spikes.
The talk is open to the public. Guests are cordially invited!