Biology subjects

Koyano, K. W.

Publications and source records attributed to Koyano, K. W..

4 recordsLinked to original sources

bioRxiv2022

Cascades of neuronal plasticity in the macaque visual cortex

Primates readily learn new visual objects, with neurons in the inferior temporal cortex exhibiting diminished visual responses to familiar stimuli. The mechanisms of visual plasticity expressed within a neural population are largely unknown. Here we used chronic microwire electrodes in a face-selective cortical area in the macaque to longitudinally track cohorts of neurons across several weeks of exposure to novel faces. Neurons showed gradual adaptation in their late-phase visual responses, with cell-specific time constants ranging from two to twenty days. These time constants were governed by the number of testing days rather than by the cumulative number of stimulus exposures. This gradual buildup of altered visual responses may serve as an internal and graded mark of stimulus familiarity, a central component of visual recognition.

neuroscience↗

bioRxiv2022

Temporal continuity shapes visual responses of macaque face patch neurons

Macaque inferior temporal cortex neurons respond selectively to complex visual images, with recent work showing that they are also entrained reliably by the evolving content of natural movies. To what extent does visual continuity itself shape the responses of high-level visual neurons? We addressed this question by measuring how cells in face-selective regions of the macaque temporal cortex were affected by the manipulation of a movies temporal structure. Sampling the movie at 1s intervals, we measured neural responses to randomized, brief stimuli of different lengths, ranging from 800 ms dynamic movie snippets to 100 ms static frames. We found that the disruption of temporal continuity strongly altered neural response profiles, particularly in the early onset response period of the randomized stimulus. The results suggest that models of visual system function based on discrete and randomized visual presentations may not translate well to the brains natural modes of operation.

neuroscience↗

bioRxiv2021

Parallel functional subnetworks embedded in the macaque face patch system

During normal vision, our eyes provide the brain with a continuous stream of useful information about the world. How visually specialized areas of the cortex, such as face-selective patches, operate under natural modes of behavior is poorly understood. Here we report that, during the free viewing of videos, cohorts of face-selective neurons in the macaque cortex fractionate into distributed and parallel subnetworks that carry distinct information. We classified neurons into functional groups based on their video-driven coupling with fMRI time courses across the brain. Neurons from each group were distributed across multiple face patches but intermixed locally with other groups at each recording site. These findings challenge prevailing views about functional segregation in the cortex and underscore the importance of naturalistic paradigms for cognitive neuroscience. One-Sentence SummaryNatural visual experience reveals parallel functional subnetworks of neurons embedded within the macaque face patch system

neuroscience↗

bioRxiv2019

Delayed suppression normalizes face identity responses in the primate brain

SummaryThe primate brain is specialized for social visual perception. Previous work indicates that recognition draws upon an internal comparison between a viewed face and an internally stored average face. Here we demonstrate that this comparison takes the form of a delayed, dynamic suppression of face averageness among single neurons. In three macaque face patches, spiking responses to low-identity morphed faces met with a synchronous attenuation starting approximately 200 ms after onset. Analysis showed that a late-emerging V-shaped identity tuning was sometimes superimposed on linear ramp tuning. This pattern could not be ascribed to repetition suppression within a given session. The results indicate that the brains analysis of faces is enhanced through predictive normalization of identity, which increases sensitivity among face-selective neurons to distinctive facial features known to drive recognition.

neuroscience↗