Award details

Investigating scene processing in the human brain

Reference	BB/V003887/1
Principal Investigator / Supervisor	Dr Edward Silson
Co-Investigators / Co-Supervisors
Institution	University of Edinburgh
Department	Sch of Philosophy Psychology & Language
Funding type	Research
Value (£)	405,224
Status	Current
Type	Research Grant
Start date	01/12/2021
End date	30/11/2024
Duration	36 months

Abstract

Retinotopy - the spatial mapping of the retina across the cortical surface - and category-selectivity - the maximal response of brain regions to particular stimulus categories - are two fundamental organising principles of human visual cortex. Until relatively recently these principles were considered largely independently but are now known to be co-localised in the brain. One such area, the Occipital Place Area (OPA) not only exhibits scene-selectivity, but also, spatially overlaps at least five separate visual field maps. The role that each visual field map plays in the pattern of responses evidenced at the level of the OPA remains unknown but raises the possibility that they each contribute a set of unique, yet complementary computations. Such a proposition was confirmed recently by our team, with respect to two visual field maps (LO1 and LO2) and the processing of orientation and shape, respectively. The demonstration that individual visual field maps contribute unique computations provides a novel framework for understanding complex visual processing, namely, that different visual features are computed in parallel by discrete regions that map the visual field. It is this framework that we aim to exploit in order to probe the functional properties of the visual field map divisions of OPA. We will capitalise on the spatial resolution of fMRI, the temporal resolution of MEG and the causal nature of TMS to provide a comprehensive account of the roles played by OPA visual field maps in complex visual processing. First, fMRI will be used to define both OPA and its visual field map divisions using cutting-edge visual field mapping techniques. Second, we will measure and evaluate what visual features these regions respond to and when such processing occurs, through a combination of fMRI, MEG, eye-tracking and behavioural experiments. Finally, we will test the causal role these visual field maps play in scene perception through retinotopically-guided TMS.

Summary

Every day, we make sense of complex visual environments to carry out simple, yet essential behaviours. These behaviours, which together are referred to as navigational affordances, include identifying our surroundings (e.g. inside a kitchen), selecting appropriate paths for navigation (e.g. the route through your lounge and into your hallway), recognising objects to interact with (e.g. light switches) and avoiding obstacles (e.g. the coffee table). Despite the importance and ease at which we perform these behaviours, we know relatively little about how the brain, and the visual cortex in particular is organised to accomplish this. One potential reason for this knowledge gap is that ideas about the organisation of visual cortex have been shaped historically by two different perspectives that were largely independent. The first perspective focused on the importance of positions in the visual field and was grounded in the fact that early stages of visual cortex contains spatial maps of the visual field called visual field maps. In contrast, the second perspective proposed that the brain contains special areas selective to certain categories, such as faces and scenes. These category-selective areas, located at later stages of visual cortex, were thought to be insensitive to positions in the visual field and independent from these early visual field maps. However, recent evidence has identified visual field maps throughout the brain, spreading far beyond the early stages of visual cortex. Moreover, several category-selective areas have been shown to spatially overlap multiple maps. This spatial overlap suggests an interaction between these two principles and raises a fundamental and as yet unanswered question: What role do these visual field maps play in visual perception? It is this question that we aim to answer with respect to a scene-selective area of the brain, referred to as the Occipital Place Area (OPA) and the visual field maps it overlaps. OPA responds morestrongly to images of scenes than to other categories and may play a role in our ability to navigate effectively. Intriguingly, recent research by our team identified at least five separate visual field maps overlapping OPA. This finding is surprising given the long-held idea that category-selective areas are insensitive to visual field position. It also raises the possibility that each of these maps performs different, yet complementary functions. We aim to test this possibility by capitalising on the strengths of different techniques. First, we will use functional magnetic resonance imaging (fMRI) to identify both OPA and the visual field map it overlaps in individual participants. Once identified, we will measure the activity in these maps during the processing of different types of scenes using fMRI. FMRI allows one to measure the activity of very small (~2mm) areas of the brain albeit relatively slowly (e.g. every 2 s). We will overcome the relative sluggishness of fMRI by using a technique that measures brain activity every millisecond - magnetoencephalography (MEG). This will provide measures of when in time aspects of scene processing occur, such as when deciding on the route to take through a room. Finally, we will test the causal nature of processing in these brain areas using a technique called transcranial magnetic stimulation (TMS). During TMS, a rapidly changing magnetic field is delivered to a small part of the head. This magnetic field temporarily and painlessly disrupts the normal activity of the stimulated brain region. Unlike both fMRI and MEG, which provide indirect measurements of brain activity, TMS can provide causal evidence of the contribution of individual areas to a particular task. Through a series of novel and ambitious projects we aim to establish the role that OPA visual field maps play in complex visual processes such as those involved in navigational affordances.

Committee	Research Committee A (Animal disease, health and welfare)
Research Topics	Neuroscience and Behaviour
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

Associated awards:

BB/V003917/1 Investigating scene processing in the human brain

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