Saccades and Blinks have been studied for a long time and of specific interest is the fact that both are not consciously perceived. This is especially surprising when considering the strong perceptual impact of comparable external events such as a camera video quickly sweeping from one point to another or a brief flicker of electric light during a short power drop. Absence of these perceptual impacts are attributed to suppression mechanisms at different levels of the hierarchical visual processing chain. I will use the term suppression to describe the attenuated sen- sory responses and omission to describe the (conscious) perceptual suppression of these events. Both phenomena have been studied in great detail mainly in the case of saccades. Here, saccadic suppression is thought to be mainly driven by visual phenomena such as visual masking at the early visual processing stages while mo- tor signals, generally called corollary discharge, are integrated at higher cortical ar- eas. Both visual and motor components combined are then causing the omission of saccades from conscious perception. A series of recent publications has described a potential mechanism causing saccadic visual masking based on the interaction of cone and bipolar cells and described a similarity of these dynamics with the dynamics for saccadic omission in human psychophysics experiments, suggesting that visual masking in the retina is the main driving factor of saccadic omission. Another publication recently found that non-visual inputs from the pulvinar al- low for distinction between internally and externally caused saccadic-like motion at the level of mouse primary visual cortex (V1), showing that motor signals are in- corporated into the saccade response earlier than previously thought. We are still lacking a description of what is happening during saccades and blinks at the level of the retina in the awake in-vivo condition. Previous studies have indicated that retinal ganglion cell (RGC) activity in-vivo can differ significantly from what has been described ex-vivo. In this thesis I am describing the direct impacts of saccades and blinks on the activ- ity of mouse RGCs in-vivo. I found that saccade responses have similar dynamics regardless of the visual context, be it different forms of direct visual stimulation or passive contexts such as saccades crossing high-contrast edges in the visual scene. Furthermore many RGCs exhibited a strong selectivity regarding the direction of saccades that is not explained by visual direction selectivity to stimuli of moving gratings. The responses to saccades differed significantly from externally simu- lated saccades (pseudo-saccades). These findings suggest that there are non-visual factors driving saccade responses in RGCs in the awake mouse. In comparison I found that blink responses match the expected behavior of RGCs responding to a transient OFF stimulus. Blinks but not saccades thus cause responses that can be explained by the visual properties of RGCs. My results pose the question if motor-related signals influence the visual response already at the level of RGCs and suggest that RGCs can distinguish between internally and externally generated mo- tion in-vivo. Our experimental paradigm also lets us shine light on the question of saccadic suppression at the level of the retina: Unless visual masking is completely independent of the initial response to saccades, visual context-independence of sac- cade responses suggest that retinal saccadic suppression can not be fully described by visual responses alone.

Description of visual and non-visual components of saccade and blink responses of retinal ganglion cells in awake mice / Wiessalla, Tristan. - (2024 Sep 18).

Description of visual and non-visual components of saccade and blink responses of retinal ganglion cells in awake mice

WIESSALLA, TRISTAN
18/09/2024

Abstract

Saccades and Blinks have been studied for a long time and of specific interest is the fact that both are not consciously perceived. This is especially surprising when considering the strong perceptual impact of comparable external events such as a camera video quickly sweeping from one point to another or a brief flicker of electric light during a short power drop. Absence of these perceptual impacts are attributed to suppression mechanisms at different levels of the hierarchical visual processing chain. I will use the term suppression to describe the attenuated sen- sory responses and omission to describe the (conscious) perceptual suppression of these events. Both phenomena have been studied in great detail mainly in the case of saccades. Here, saccadic suppression is thought to be mainly driven by visual phenomena such as visual masking at the early visual processing stages while mo- tor signals, generally called corollary discharge, are integrated at higher cortical ar- eas. Both visual and motor components combined are then causing the omission of saccades from conscious perception. A series of recent publications has described a potential mechanism causing saccadic visual masking based on the interaction of cone and bipolar cells and described a similarity of these dynamics with the dynamics for saccadic omission in human psychophysics experiments, suggesting that visual masking in the retina is the main driving factor of saccadic omission. Another publication recently found that non-visual inputs from the pulvinar al- low for distinction between internally and externally caused saccadic-like motion at the level of mouse primary visual cortex (V1), showing that motor signals are in- corporated into the saccade response earlier than previously thought. We are still lacking a description of what is happening during saccades and blinks at the level of the retina in the awake in-vivo condition. Previous studies have indicated that retinal ganglion cell (RGC) activity in-vivo can differ significantly from what has been described ex-vivo. In this thesis I am describing the direct impacts of saccades and blinks on the activ- ity of mouse RGCs in-vivo. I found that saccade responses have similar dynamics regardless of the visual context, be it different forms of direct visual stimulation or passive contexts such as saccades crossing high-contrast edges in the visual scene. Furthermore many RGCs exhibited a strong selectivity regarding the direction of saccades that is not explained by visual direction selectivity to stimuli of moving gratings. The responses to saccades differed significantly from externally simu- lated saccades (pseudo-saccades). These findings suggest that there are non-visual factors driving saccade responses in RGCs in the awake mouse. In comparison I found that blink responses match the expected behavior of RGCs responding to a transient OFF stimulus. Blinks but not saccades thus cause responses that can be explained by the visual properties of RGCs. My results pose the question if motor-related signals influence the visual response already at the level of RGCs and suggest that RGCs can distinguish between internally and externally generated mo- tion in-vivo. Our experimental paradigm also lets us shine light on the question of saccadic suppression at the level of the retina: Unless visual masking is completely independent of the initial response to saccades, visual context-independence of sac- cade responses suggest that retinal saccadic suppression can not be fully described by visual responses alone.
18-set-2024
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1720116
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