Biology subjects

Shapcott, K.

Publications and source records attributed to Shapcott, K..

4 recordsLinked to original sources

bioRxiv2026

More is better: Improved visual discrimination through local feature diversity in naturalistic objects

Visual discrimination is traditionally studied with highly controlled, artificial stimuli such as gratings. Yet real-world object discrimination relies on many interacting image dimensions. Here we compared human discrimination performance of oriented gratings with that of natural object morphs, and then asked which stimulus dimensions are most important for morph discrimination. In Experiment 1, participants discriminated between two artificial gratings, two natural grating-like textures, and two natural, morphed stimuli. Morph stimuli were discriminated faster and over a larger stimulus range. In Experiment 2, we separated the contribution of distinct image features, specifically colour, texture, and shape, to the discriminability of the morph stimuli. To this end, we varied two feature dimensions at a time while keeping the third dimension constant. Discrimination was best when colour and texture varied together, resulting in steeper psychometric functions and faster responses than when shape changed. Together, these results suggest a discriminative advantage for natural-object morphs over gratings, driven primarily by local colour and texture information rather than global shape.

neuroscience↗

bioRxiv2024

Sharing the Spotlight: Uncovering common attentional dynamics across species

Sustained attention is a key underlying process to many natural behaviours that are shared by multiple species. Yet the way it is commonly studied in a lab context precludes any meaningful cross-species comparisons. Here, we engaged mice, monkeys, and humans in the exact same, natural perceptual decision task in a VR environment. We captured their behaviour into several parameters along the speed/accuracy axes along which sustained attention is classically defined, and used HMMs to infer four attentional states. We show that the dynamics of these states, both in terms of their durations as well as the transitions between them, are much more similar between the species than might have been expected. Moreover, attentional state fluctuations seem to be internally generated. The task and analyses developed here represent a new approach to compare sustained attention across species in an objective, data-driven way.

animal behavior and cognition↗

bioRxiv2023

Dynamic Fading Memory and Expectancy Effects in Monkey Primary Visual Cortex

In order to investigate the involvement of primary visual cortex (V1) in working memory (WM), parallel, multisite recordings of multiunit activity were obtained from monkey V1 while the animals performed a delayed match-to-sample (DMS) task. During the delay period, V1 population firing rate vectors maintained a lingering trace of the sample stimulus that could be reactivated by intervening impulse stimuli that enhanced neuronal firing. This fading trace of the sample did not require active engagement of the monkeys in the DMS task and likely reflects the intrinsic dynamics of recurrent cortical networks in lower visual areas. This renders an active, attention-dependent involvement of V1 in the maintenance of working memory contents unlikely. By contrast, population responses to the test stimulus depended on the probabilistic contingencies between sample and test stimuli. Responses to tests that matched expectations were reduced which agrees with concepts of predictive coding.

neuroscience↗

bioRxiv2020

Stimulus-specific plasticity of macaque V1 spike rates and gamma

When a visual stimulus is repeated, average neuronal responses typically decrease, yet they might maintain or even increase their impact through increased synchronization. Previous work has found that many repetitions of a grating lead to increasing gamma-band synchronization. Here we show in awake macaque area V1 that both, repetition-related reductions in firing rate and increases in gamma are specific to the repeated stimulus. These effects showed some persistence on the timescale of minutes. Further, gamma increases were specific to the presented stimulus location. Importantly, repetition effects on gamma and on firing rates generalized to natural images. These findings suggest that gamma-band synchronization subserves the adaptive processing of repeated stimulus encounters, both for generating efficient stimulus responses and possibly for memory formation.

neuroscience↗