Microsaccade production during saccade cancelation in a stop-signal task

Abstract

We obtained behavioral data to evaluate two alternative hypotheses about the neural mechanisms of gaze control. The “fixation” hypothesis states that neurons in rostral superior colliculus (SC) enforce fixation of gaze. The “microsaccade” hypothesis states that neurons in rostral SC encode microsaccades rather than fixation per se. Previously reported neuronal activity in monkey SC during the saccade stop-signal task leads to specific, dissociable behavioral predictions of these two hypotheses. When subjects are required to cancel partially-prepared saccades, imbalanced activity spreads across rostral and caudal SC with a reliable temporal profile. The microsaccade hypothesis predicts that this imbalance will lead to elevated microsaccade production biased toward the target location, while the fixation hypothesis predicts reduced microsaccade production. We tested these predictions by analyzing the microsaccades produced by 4 monkeys while they voluntarily canceled partially prepared eye movements in response to explicit stop signals. Consistent with the fixation hypothesis and contradicting the microsaccade hypothesis, we found that each subject produced significantly fewer microsaccades when normal saccades were successfully canceled. The few microsaccades escaping this inhibition tended to be directed toward the target location. We additionally investigated interactions between initiating microsaccades and inhibiting normal saccades. Reaction times were longer when microsaccades immediately preceded target presentation. However, pre-target microsaccade production did not affect stop-signal reaction time or alter the probability of canceling saccades following stop signals. These findings demonstrate that imbalanced activity within SC does not necessarily produce microsaccades and add to evidence that saccade preparation and cancelation are separate processes.

Deep learning can be used to train naïve, nonprofessional observers to detect diagnostic visual patterns of certain cancers in mammograms: a proof-of-principle study

“…As alluded to above, we focused on microsaccades, because they represent fixational eye movements that result when the viewer is actively scrutinizing a region of the image that is of interest to the viewer (see Refs. 70 – 74 ). Moreover, our preliminary results in a related previous experiment had suggested that the number of microsaccades decreases as the subjects get better at the cancer detection task.…”

Distinct population codes for attention in the absence and presence of visual stimulation

“…Even recognizing that the timing of statistical significance varies due to assumed significance level and other factors, such a slow time course of attention effects presents a conundrum because the neural effects of attention must strictly precede the behavioral benefits. Moreover, the saccadic response time is undoubtedly an overestimate of the subjects’ true decision times: monkeys’ stop-signal reaction times (an estimate of internal decision processes) have been measured to be about 110 ms in a task where the average saccadic reaction times are greater than 250 ms 31 , 32 .

Fig.

…”

A stop-signal task for sheep: introduction and validation of a direct measure for the stop-signal reaction time

“…The SST paradigm has been studied in rhesus and bonnet macaque monkeys (e.g., Godlove et al 2011 , Godlove and Schall 2016 , Middelbrooks and Schall 2014 ), primarily to explore the neural signature of response inhibition (e.g., Emeric et al 2008 ). Our study shows that sheep have the ability to stop an initiated action in response to an operant cue, in a way that is comparable to established paradigms in humans and monkeys measured using established paradigms.…”