Gast ::
| Hauptseite > Publikationsdatenbank > Saccade Related Layer Specific Local Field Po-tential Activity in Macaque V1 during FreeViewing |
| Hauptseite > Publikationsdatenbank > Saccade Related Layer Specific Local Field Po-tential Activity in Macaque V1 during FreeViewing |
| Abstract | FZJ-2015-02184 |
; ; ; ; ;
2015
Abstract: Primates perform frequent saccadic eye movements (SEMs) to sample visual information from theirenvironment. These SEMs are accompanied in the primary visual cortex (V1) by local fieldpotential (LFP) modulations that precede the arrival of the visual input [Ito et al. (2011) CerebCortex 21:2482-97].In the present study we aim to elucidate how the SEM related LFP modulations depend on theproperties of visual input during saccades. For this purpose, we presented stationary, full-fieldgrating stimuli to an awake macaque monkey, who freely explored the stimuli with voluntarysaccadic eye movements. Eye movements were recorded with a scleral eye coil and the LFP fromV1 with a 24-channel linear electrode array. We identified SEM related LFP modulations byaveraging the LFP signal aligned to the onsets of saccades and subsequent fixations, andreconstructed the corresponding current source density (CSD) signal (Figure a and b) from the LFPvia the inverse CSD method [Pettersen et al. (2006) J Neurosci Meth 154:116–33]. For acomparison we also computed the average LFP and CSD signal aligned to the onset of the stimulusimages preceded by fixation on a central fixation spot (Figure c).The monkey preferred to perform saccades in the direction parallel to the stripes of the stimulusimage. Those parallel saccades (PSs) had a larger median amplitude, velocity and duration thanorthogonal saccades (OSs) and intermediate saccades. We found that the SEM related LFPmodulation was stronger for OSs than for PSs. The CSD signal showed a current sink in thegranular layer, that was observed for the saccade-onset and fixation-onset triggered averages but notfor the image-onset triggered averages, confirming that this sink reflected SEM related activity(Figure a and b, red frames vs. c, red frame). The OSs evoked stronger current sinks than the PSs.We observed a positive correlation between the amplitude of saccades and the magnitude of theevoked current sink. The increase of the CSD signal for larger saccades saturated more quickly forOSs than for PSs (Figure d vs. e). This SEM related current sink probably reflects an inhibitoryprocess because it was accompanied by a concurrent decrease in high-gamma band (~160 Hz)power, which has been shown to be strongly positively correlated to the firing rates of local neurons[Ray et al. (2008) J Neurosci 28:11526-36].In summary, saccades causing larger changes in the retinal image, such as those with largeramplitude and/or in directions more orthogonal to the stripes of the stimulus images, evokedstronger CSD modulations. This seems to suggest mere excitation of V1 by the retinal changescaused by saccades, but a comparison with the concurrent high-gamma power modulation rathersuggests that the CSD modulation reflects an inhibitory process. A possible implication of theseobservations would be that the CSD signal might reflect an active suppression mechanism thatmatches the amount of inhibition to the strength of the visual input during saccades.
|
The record appears in these collections: |