Yip, H. M. K. | Search bioRxiv

bioRxiv2026

Sensory origin of oculomotor variability revealed by MT population activity

Motor outputs vary even in response to identical sensory inputs, yet the origin of this variability within the sensorimotor pathway remains unresolved. Here, we evaluate how variability in sensory representations can explain behavioural fluctuations in a reflexive oculomotor task. We used Neuropixels probes to record neuronal activity in area MT of marmosets during ocular following responses and applied partial least squares regression to extract the shared variance between population activity and eye movements. Stimulus-evoked activity reliably predicted trial-by-trial variability in open-loop eye velocity. Additionally, closed-loop analyses revealed trial-by-trial correspondence between eye movements and subsequent neural responses. These results demonstrate that variability in sensory neural populations contributes to motor variability, supporting the claim that sensory noise is propagated through the sensorimotor pathway. Surprisingly, however, traditional models trained to only capture neural variability across trials poorly predicted behavioural variations, suggesting that only a subset of sensory representations is accessible to the motor system.

neuroscience↗

bioRxiv2023

Ocular following responses of the marmoset monkey are dependent on post-saccadic delay, spatiotemporal frequency and saccade direction

Ocular following is a short-latency, reflexive eye movement that tracks wide-field visual motion. It has been studied extensively in humans and macaques and is an appealing behaviour for studying sensory-motor transformations in the brain due to its rapidity and rigidity. We explored ocular following in the marmoset, an emerging model in neuroscience because their lissencephalic brain allows direct access to most cortical areas for imaging and electrophysiological recordings. In three experiments, we tested ocular following responses in three adult marmosets. First, we varied the gap between saccade end and stimulus motion onset (post-saccadic delay), from 10 to 300 ms. As in other species, tracking had shorter onset latencies and higher eye speeds with shorter post-saccadic delays. Second, using sine-wave grating stimuli we explored the dependence of eye speed on spatiotemporal frequency. The highest eye speed was evoked at [~]16 Hz and [~]0.16 cycles per degree (cpd), however, the highest gain was elicited at [~]1.6 Hz and [~]1.2 cpd. The highest eye speed for each spatial frequency was observed at a different temporal frequency, but this interdependence was not consistent with complete speed tuning of the ocular following response. Finally, we found the highest eye speeds when saccade and stimulus motion directions were congruent, although latencies were unaffected by direction congruence. Our results showed comparable ocular following in marmosets, humans and macaques, despite over an order of magnitude variation in body and eye size across species. This characterization will help future studies examining the neural basis of sensory-motor transformations. New & NoteworthyPrevious ocular following studies focused on humans and macaques. We examined the properties of ocular following responses in marmosets in three experiments, in which post-saccadic delay, spatial-temporal frequency of stimuli and congruency of saccade and motion directions were manipulated. We have demonstrated short-latency ocular following in marmosets, and discuss the similarities across three species that vary markedly in eye and head size. Our findings will help future studies examining the neural mechanism of sensory-motor transformations.

neuroscience↗

bioRxiv2020

The Effect of Task on Object Processing revealed by EEG decoding

Recent studies showed that task demand affects object representations in higher-level visual areas and beyond, but not so much in earlier areas. There are, however, limitations in those studies including the relatively weak manipulation of task due to the use of familiar real-life objects, the low temporal resolution in fMRI, and the emphasis on the amount and not the source of information carried by brain activations. In the current study, observers categorized images of artificial objects in one of two orthogonal dimensions, shape and texture, while their brain activity was recorded with electroencephalogram (EEG). Results showed that object processing along the texture dimension was affected by task demand starting from a relatively late time (320-370ms time window) after image onset. The findings are consistent with the view that task exerts an effect on the later phases of object processing.

neuroscience↗