Rising Stars in Systems Neuroscience: 2022

Editorial

14 May 2024

Editorial: Rising stars in systems neuroscience: 2022

Mazyar Fallah

Juhee Haam

and

Ada Ledonne

1,730 views

0 citations

Editors

Ada Ledonne

University of Rome Tor Vergata

Mazyar Fallah

University of Guelph

Juhee Haam

Louisiana State University

Impact

The distractor-saccade onset asynchrony (SDOA) paradigm. (A) Task procedure schematic. Targets are displayed at some random interval before the distractor (stimulus onset asynchrony). Participants elicit target-directed saccades sometime after distractor onset (distractor processing time). (B) Putative neural underpinnings. Depicted is the hypothetical activation of visuomotor neurons elicited when the target (red line) or distractor (blue line) are in the motorfield of the cell. Activation is plotted as a function of time relative to the saccade. The onset of the saccade is indicated by the black vertical line and black “X”s. In the perisaccadic interval immediately prior to the saccade (gray shaded region), the incipient motor plan for target-directed saccades may become biased by unresolved distractor activation. The target is displayed sometime prior to the saccade (red “X”s). In this contrived example, the saccadic reaction time is constant. The target onset elicits a visual onset burst time-locked to stimulus onset and a motor burst time-locked to the saccade. The distractor onset (blue “X”s) is stochastic and can occur at any time relative to the saccade. The distractor onset elicits a visual onset burst time-locked to stimulus onset. In this example, we systematically increase the distractor processing time (i.e., the duration of time between distractor onset and subsequent saccade), illustrated by the blue line with arrowhead. As such, the distractor-related visual onset burst sweeps through the perisaccadic interval. Right insets depict hypothetical saccades elicited by the distractor visual onset burst given its position in time relative to the perisaccadic interval. (C) The results across iterations of the SDOA paradigm. Saccade curvature (vector biasing) is plotted as a function of distractor processing time for all examined distractor features: static-gratings (blue), motion-gratings (red) (Kehoe et al., 2023); luminance-modulated Gabors (green), color-modulated Gabors (magenta) (Kehoe and Fallah, 2017); and complex pseudo-alphanumeric characters during discrimination (yellow) (Kehoe et al., 2021). We highlight notable effects with text-labeled arrows: (1) for simple gratings, vector biasing onsets after just 25 ms of distractor processing time; (2) features begin to differentiate after approximately 50 ms of distractor processing time; (3) the maximum vector biasing occurs after approximately 100 ms of distractor processing time; and (4) discriminated complex objects elicit vector biasing very late, after approximately 110 ms. Note that these data from prior publications have been replotted onto a common figure.

Hypothesis and Theory

12 October 2023

Oculomotor feature discrimination is cortically mediated

Devin H. Kehoe

and

Mazyar Fallah

Eye movements are often directed toward stimuli with specific features. Decades of neurophysiological research has determined that this behavior is subserved by a feature-reweighting of the neural activation encoding potential eye movements. Despite the considerable body of research examining feature-based target selection, no comprehensive theoretical account of the feature-reweighting mechanism has yet been proposed. Given that such a theory is fundamental to our understanding of the nature of oculomotor processing, we propose an oculomotor feature-reweighting mechanism here. We first summarize the considerable anatomical and functional evidence suggesting that oculomotor substrates that encode potential eye movements rely on the visual cortices for feature information. Next, we highlight the results from our recent behavioral experiments demonstrating that feature information manifests in the oculomotor system in order of featural complexity, regardless of whether the feature information is task-relevant. Based on the available evidence, we propose an oculomotor feature-reweighting mechanism whereby (1) visual information is projected into the oculomotor system only after a visual representation manifests in the highest stage of the cortical visual processing hierarchy necessary to represent the relevant features and (2) these dynamically recruited cortical module(s) then perform feature discrimination via shifting neural feature representations, while also maintaining parity between the feature representations in cortical and oculomotor substrates by dynamically reweighting oculomotor vectors. Finally, we discuss how our behavioral experiments may extend to other areas in vision science and its possible clinical applications.

18,246 views

2 citations

Review

16 August 2023

The perceptual consequences and neurophysiology of eye blinks

Shawn M. Willett

, 1 more and

J. Patrick Mayo

A hand passing in front of a camera produces a large and obvious disruption of a video. Yet the closure of the eyelid during a blink, which lasts for hundreds of milliseconds and occurs thousands of times per day, typically goes unnoticed. What are the neural mechanisms that mediate our uninterrupted visual experience despite frequent occlusion of the eyes? Here, we review the existing literature on the neurophysiology, perceptual consequences, and behavioral dynamics of blinks. We begin by detailing the kinematics of the eyelid that define a blink. We next discuss the ways in which blinks alter visual function by occluding the pupil, decreasing visual sensitivity, and moving the eyes. Then, to anchor our understanding, we review the similarities between blinks and other actions that lead to reductions in visual sensitivity, such as saccadic eye movements. The similarity between these two actions has led to suggestions that they share a common neural substrate. We consider the extent of overlap in their neural circuits and go on to explain how recent findings regarding saccade suppression cast doubt on the strong version of the shared mechanism hypothesis. We also evaluate alternative explanations of how blink-related processes modulate neural activity to maintain visual stability: a reverberating corticothalamic loop to maintain information in the face of lid closure; and a suppression of visual transients related to lid closure. Next, we survey the many areas throughout the brain that contribute to the execution of, regulation of, or response to blinks. Regardless of the underlying mechanisms, blinks drastically attenuate our visual abilities, yet these perturbations fail to reach awareness. We conclude by outlining opportunities for future work to better understand how the brain maintains visual perception in the face of eye blinks. Future work will likely benefit from incorporating theories of perceptual stability, neurophysiology, and novel behavior paradigms to address issues central to our understanding of natural visual behavior and for the clinical rehabilitation of active vision.

10,540 views

8 citations