Biology subjects

Samonds, J. M.

Publications and source records attributed to Samonds, J. M..

3 recordsLinked to original sources

bioRxiv2026

Parvalbumin and somatostatin inhibitory microcircuits perform distinct roles in stereo matching

We readily perceive stereoscopic depth in correlated random dot stereograms (RDS), in which every dot presented to one eye has a matching dot in the other eye. In contrast, anti-correlated RDS, in which corresponding dots have opposite contrast polarity between the two eyes, do not evoke a perception of depth. Nevertheless, anti-correlated RDS still generate local same-polarity matches within the receptive fields of individual neurons. Inhibitory circuitry has been proposed to suppress these false matches and thereby prevent the perception of illusory depth. To investigate how inhibitory circuits in visual cortex contribute to this process, we measured disparity selectivity to correlated and anti-correlated RDS in two major classes of inhibitory neurons in mice: parvalbumin-expressing (PV+) and somatostatin-expressing (SST+) neurons. We found that the disparity tuning of PV+ neurons was highly correlated with the average activity of surrounding neurons. In contrast, the disparity tuning of SST+ neurons was poorly predicted by local population activity, suggesting that PV+ and SST+ neurons integrate excitatory inputs through distinct mechanisms. Optogenetic suppression of PV+ or SST+ neurons further revealed divergent functional roles. Although both cell types contributed to sharpening selectivity for correlated RDS, only SST+ neurons reduced selectivity for anti-correlated RDS. These findings suggest that PV+ and SST+ circuits both enhance responses to correct binocular matches in correlated RDS, whereas SST+ circuits contribute to suppressing false matches in anti-correlated RDS.

neuroscience↗

bioRxiv2025

Degraded mapping of disparity tuning in visual cortex explains deficits in binocular depth perception

Sensory cortex is highly organized, but the function of this organization is contentious. We show that closing one eye during the developmental critical period in juvenile mice (monocular deprivation) caused lasting impairments in binocular depth perception and disrupted cortical maps of binocular disparity tuning. In normal mice, disparity tuning was concentrated in the central visual field, particularly with respect to azimuth and in higher visual areas (HVAs). Additionally, neurons transitioned from encoding nearer to farther stereoscopic depths from the center toward the peripheral visual field, especially along elevation and within HVAs. Monocular deprivation did not reduce overall disparity selectivity across the neuronal population, but rather weakened the retinotopic and hierarchical organization of disparity tuning and reduced trial-to-trial reliability of neuronal responses. Analysis of single-trial responses from neurons tuned to near disparities showed that this reduced response reliability is sufficient to explain the impaired depth discrimination observed in deprived mice.

neuroscience↗

bioRxiv2023

Mammals achieve common neural coverage of visual scenes using distinct sampling behaviors

Most vertebrates use head and eye movements to quickly change gaze orientation and sample different portions of the environment with periods of stable fixation. Visual information must be integrated across several fixations to construct a more complete perspective of the visual environment. In concert with this sampling strategy, neurons adapt to unchanging input to conserve energy and ensure that only novel information from each fixation is processed. We demonstrate how adaptation recovery times and saccade properties interact, and thus shape spatiotemporal tradeoffs observed in the motor and visual systems of different species. These tradeoffs predict that in order to achieve similar visual coverage over time, animals with smaller receptive field sizes require faster saccade rates. Indeed, we find comparable sampling of the visual environment by neuronal populations across mammals when integrating measurements of saccadic behavior with receptive field sizes and V1 neuronal density. We propose that these mammals share a common statistically driven strategy of maintaining coverage of their visual environment over time calibrated to their respective visual system characteristics.

neuroscience↗