Abstract
Abstract Using EEG backward averaging method there were fast negative and positive potentials found before regular short latency saccades and express-saccades. These potentials can reflect different stages of presaccadic preparation which include processes of saccadic system release of central fixation, attention disengagement from the central stimulus, decision making and activation of premotor cortical and subcortical structures. There were two schemes of visual stimulus presentation used–“step” and with a 200-ms “gap”. Analysis of parameters and spatiotemporal dynamics of potentials allowed us to assume that express-saccades appear in conditions when the previously selected motor programm and prediction of the target location coincides with the real coordinates of the target. At that optimum preparation of neuronal structure and a high level of readiness and attention are necessary. Decreasing an express-saccade latency can be the result of participation of main oculomotor areas of motor and saccadic planning in express-saccades initiation, particularly by direct signal transferring from the cortex to the saccadic brainstem generator, by-passing superior colliculus. Moreover, to successfully start initiation process and generate express-saccades, release from central fixation and attention disengagement has to begin in advance.
Highlights
To study the attention disengagement process in saccade programming in 1967 Saslow et al developed an experimental paradigm with a delay of peripheral trigger stimulus presentation after the central fixation stimulus offset (Saslow, 1967)
Saccadic latency Analysis of saccade latency period durations showed that “interstimulus interval” introduction during stimulus presentation led to saccade latency period shortening by 23-70 ms (“gap-effect”,
EEG-potentials Analysis of averaged EEG potentials, obtained by backward averaging from saccade beginning, showed that each subject had a complex of fast potentials different polarity: spike potential, N -1 (“minus one”) and -1 potentials in the saccade latency period, N -2, -2, N -3 and -3 potentials in the interstimulus interval
Summary
To study the attention disengagement process in saccade programming in 1967 Saslow et al developed an experimental paradigm with a delay of peripheral trigger stimulus presentation after the central fixation stimulus offset (Saslow, 1967). Reulen (Reulen, 1984), according to which disappearance of the fixation point initiates offsignal appearance on retina This signal can intensify or accelerate the processes of stimulus specific sensor processing, decision making and motor command. Neurophysiological studies of primates showed a reciprocal interaction of fixation and motor neurons in many oculomotor structures (Bon & Lucchetti, 1992; Munoz & Wurtz, 1993) In this connection there was a hypothesis expressed that fixation point offset in the “gap”-scheme leads to oculomotor system release from fixation and activation of specific processes in it which are connected with saccade preparation, initiation and execution The aim of the research was the analysis of spatiotemporal characteristics of human brain presaccadic potentials during fixation and target stimulus presentation with a “delay” at monocular stimulation of the right and the left eye
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