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BME Seminars - Daniel Guitton


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On Wednesday the 30th of April 2014, the BME seminars "Open Your Mind" will host a conference of Daniel Guitton from the Institut Neurologique de Montréal (Université McGill, Montréal, Québec, Canada). His conference is entitled “Spatio-temporal mechanisms of pre-saccadic receptive field remapping in monkey visual area V4”

 

The conference will take place on Wednesday 30th of april at Arts et Métiers ParisTech, 151 boulevard de l’Hôpital, 75013 Paris (Amphi Esquillan), from 13h30 to 15h00.

 

Abstract:

Visual neurons have spatial receptive fields (RFs) that are sensitive to visual stimuli in a circumscribed area of visual space relative to the fovea. Because foveate animals execute frequent saccadic eye movements, this position information in retinal coordinates is constantly changing with each saccade, even when the visual world is stationary. Interestingly, visual RFs in many brain regions have been found to exhibit changes in their position even before the saccade occurs. Indeed, neurons transiently respond to stimuli flashed prior to the saccade, at the location where their RF will be after the saccade (called the future RF = FF); a shift parallel to the impending saccade vector. This has been called predictive RF remapping and has been studied in many brain areas. Here we report on this phenomenon in the higher order visual area V4, known to be strongly modulated by attention and object salience. We recorded V4 neurons in alert monkeys using 10x10 electrode arrays, with which we could measure spikes and local field potentials at many locations simultaneously. RESULTS: 1) The RFs, defined on the basis of spike discharges, showed for most neurons a classical pre-saccadic shift parallel to the saccade vector. 2) In a minority of neurons such a shift was accompanied by a subsequent shift towards the saccade target as in Tolias et al (2001).  3) By comparison, the LFPs on all viable electrodes (~90) showed RFs that shifted parallel to the saccade and then towards the saccade target, as in the latter category of neurons.  4) For neurons that had preferred features the remapping signal did not encode such a preference. 5) When the flashed probe was replaced with the static probe, used by Tolias et al (2001), both the spike and LFP RFs shrunk and shifted towards the saccade target.  The manifestation of predictive remapping is therefore paradigm-dependent. 6) Finally we studied gamma activity at electrodes that recorded from the RF, FF and saccade target locations, respectively. We found a shifting enhanced coherence time-locked to saccade end: first between recording electrodes encoding RF and FF locations followed by that between electrodes encoding RF and saccade target locations. CONCLUSION: the remapping observations are compatible with shifts of attentional loci.  


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