Sensory Input Modulates Microsaccades during Heading Perception.

Milena Raffi,Monica Perazzolo,Alessandro Piras,Aurelio Trofè,Andrea Meoni

doi:10.3390/ijerph18062865

Milena Raffi, Monica Perazzolo + Show 3 more

Open Access

https://doi.org/10.3390/ijerph18062865

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Abstract

Microsaccades are small eye movements produced during attempted fixation. During locomotion, the eyes scan the environment; the gaze is not always directed to the focus of expansion of the optic flow field. We sought to investigate whether the microsaccadic activity was modulated by eye position during the view of radial optic flow stimuli, and if the presence or lack of a proprioceptive input signal may influence the microsaccade characteristics during self-motion perception. We recorded the oculomotor activity when subjects were either standing or sitting in front of a screen during the view of optic flow stimuli that simulated specific heading directions with different gaze positions. We recorded five trials of each stimulus. Results showed that microsaccade duration, peak velocity, and rate were significantly modulated by optic flow stimuli and trial sequence. We found that the microsaccade rate increased in each condition from trial 1 to trial 5. Microsaccade peak velocity and duration were significantly different across trials. The analysis of the microsaccade directions showed that the different combinations of optic flow and eye position evoked non-uniform directions of microsaccades in standing condition with mean vectors in the upper-left quadrant of the visual field, uncorrelated with optic flow directions and eye positions. In sitting conditions, all stimuli evoked uniform directions of microsaccades. Present results indicate that the proprioceptive signals when the subjects stand up creates a different input that could alter the eye-movement characteristics during heading perceptions.

Highlights

The optic flow fields projected on the retina allow the observer to create a neural representation of the extrapersonal space and to move into the environment
We sought to investigate whether the microsaccadic activity was modulated by eye position during the view of radial optic flow stimuli and if the view of different optic flow stimuli changes the microsaccade characteristics and directions
To verify the identity of the eye movements, to avoid including potential nystagmu we plotted velocity (Figure 2) and position (Figure 3) waveforms of exemplary microsa cades for both conditions in each stimulus

Summary

Introduction

The optic flow fields projected on the retina allow the observer to create a neural representation of the extrapersonal space and to move into the environment. The first studies on the role of optic flow in self-motion perception started in the 1950s with J. Many studies have investigated, both on animal and human models, the cortical and subcortical mechanisms responsible for heading perception. Several studies have shown that specific optic flow stimuli are important for guiding locomotion [17,18,19,20] and for the postural control [21,22,23,24,25]. The picture arising from those studies is that the analysis of the optic flow stimuli is a predominantly cortical process preparatory for specific motor actions

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