The dynamics of feature binding and retrieval in the visual brain

BBSRC strategic theme: Biosciences for an integrated understanding of health

Visual perception refers to the system of processes by which the brain organises and interprets visual information. Under the efficient coding hypothesis, the neural system for binding of visual features (e.g., colour and orientation) should be efficiently configured and optimised according to frequencies of patterns in the environment (i.e., natural statistics).

The first research line will centre on systematic explorations of feature binding dynamics induced by manipulated natural statistics (e.g., coupling colours with orientations). Moreover, individual feature spaces will be also investigated in relation to altered natural statistics distributions. For these objectives, extended reality with binocular video passthrough will be used alongside traditional psychophysical methods.

The second research line will focus on visual working memory (VWM), a flexible neural system enabling to store and retrieve internal representations of visual information over short time. The binding dynamics will be studied within the cued recall paradigm where participants encode a set of objects with unique feature values (e.g., colours and orientations).

After a brief interval, the target item is cued by one of its features (e.g., colour) and another one must be reported (e.g., location). As such, the retrieval process can be broadly divided into cue-to-item matching and report feature readout. These stages will be explored in relation to trial-level dynamics across feature spaces, for example, testing the potential parallel nature of VWM retrieval and retrieval time components in relation to response errors.

Importantly, previous computational work drew a parallel between VWM retrieval and visual decision making through the accumulation-to-bound principle where sensory information is continuously integrated towards decision bounds. Using the cued recall task, this project will further investigate the potential similarities building on robust findings in perceptual decision making, such as the effects of time pressure and task difficulty.

Additionally, the trial-level dynamics will be examined through changes of mind, representing adaptive real-time decision updating. Follow-up experiments will extend the main findings to altered feature characteristics and dimensionality, targeting binding dynamics from the VWM retrieval perspective. The final experiments will strive to identify dynamics across trials and feature domains, for example, testing potential shifts in cue feature dominance within VWM retrieval by manipulating natural statistics of stimuli features.

To extend behavioural analyses, the binding dynamics mechanism and VWM retrieval will be investigated using computational models within the accumulation-to-bound and population coding frameworks.

In general, to advance our understanding of the dynamics of feature binding and retrieval in the visual brain, the project will utilise rigorous experimental manipulations in a multi-paradigm approach, focused on both visual perception and VWM. Whereas visual perception is typically framed as the encoding stage only preceding VWM storage, these cognitive and neural faculties might dynamically interact to navigate even through the most basic tasks.

This work will initially attempt to map the key dynamics in each faculty to subsequently test their mutual dynamics, synthesised into testable computational models. Crucially, these fundamental principles may provide foundations for developments of diagnostic measures, sufficiently sensitive to detect emerging feature binding deficits, for example, in early stages of Alzheimer's disease.