Graham, K, Downing, P and Mundy, M (2011-2016). Differentiating the contributions of domain-specific regions within the medial temporal lobe and extrastriate cortex to perception. BBSRC. £1,008,401 (Cardiff Funding: £496,909)
Specialist Summary
A major goal of cognitive neuroscience is to understand how the human brain stores and retrieves information critical to social interaction and navigation in our environment. A significant body of work has used functional neuroimaging techniques to identify areas in extrastriate cortex that show evidence of domain-specificity (e.g., greater activation for a particular category of stimuli, such as faces, compared to another category, say scenes). Notably, however, little attention has been drawn to the fact that other areas in the brain, in particular medial temporal lobe (MTL) structures, also show evidence of domain-specificity. A key psychological division between these brain areas is thought to be between perception (extrastriate) and memory (MTL). Notably, however, regions within the MTL do not just show domain-specific properties on memory tasks, but also on simple discrimination tasks (same/different judgements) more akin to those used to measure perception. There is an urgent need, therefore, for a body of work aimed at bridging the gap between these separate strands of cognitive neuroscience research, with a particular focus on identifying what types of perceptual representations are stored within these different brain regions. This project addresses this issue by drawing together experts in perception, learning and memory to develop an overarching theoretical model of how the brain represents particular types of visual stimuli. Functional neuroimaging will be used to ask (a) how do MTL and extrastriate areas differ in their degree of domain-selectivity across categories, and across exemplars within these categories and (b) is 'feature ambiguity' or visual similarity a key factor influencing recruitment of MTL, but not extrastriate, areas in perception (across categories). This programme will resolve current controversies in perception and memory research, and establish a new area of research likely to result in novel theoretical findings.
Non-Specialist Summary
Perception of, and memory for, faces, scenes and objects is necessary for successful social interaction and navigation in our environment. Understanding how we tell apart and remember these different categories of stimuli, therefore, is a key question in cognitive and social neuroscience. This project contributes to this question by using functional neuroimaging to identify brain areas that are selective in their response to particular categories of visual stimuli. The proposed experiments then ask how these different regions support our ability to distinguish items both across and within these visual categories. For example, three brain regions in humans - the occipital face area, fusiform face area and perirhinal cortex - show particularly strong responses to faces, compared to scenes and objects. Damage or disruption to these brain regions results in difficulties in telling apart different faces, but less so scenes and objects. Processing of faces, therefore, is clearly dependent upon a number of special brain areas distributed throughout the human brain. As yet, however, we know little about how these three face regions contribute to perceiving and identifying faces, including understanding what type of facial information is stored in each region, and whether these representations are unique to faces across these regions. We also do not know whether these areas are recruited separately (or together) during tasks in which one is required to tell apart faces, and whether this differs depending upon factors such as visual similarity. Extending these questions beyond face stimuli, there are outstanding issues regarding whether the information we learn from our experiments on faces can be generalised to domain-specific regions specialised for processing other visual categories, such as scenes and objects. This is an important, and novel, part of our proposal, as evidence of generalisation would highlight fundamental neural principles about how the human brain acquires, stores and uses information about visual categories, as opposed to just face stimuli.
To address these important questions, the proposed project aims to use functional neuroimaging to ask which brain areas are sensitive to distinct categories (e.g., faces, scenes and objects) and how these regions help support perception for items that comprise these categories. The planned experiments will identify similarities and differences in how these regions store different categories of stimuli (e.g., by visual features comprising these items or as whole items) and help identify the contribution made by these brain areas to perception.
The programme of research is novel in that it aims to integrate methods from two psychological disciplines (perception and memory) that are typically researched independently, including investigating how regions thought to be uniquely specialised for memory processing may also contribute to perception. It also aims to look for commonalities (and differences) across visual categories and across brain areas; this approach is rare in cognitive neuroscience research, but ensures, here, that our planned experiments will result in significant advances in our understanding of how the brain represents and remembers categories of stimuli key to successful interactions with people, and the environment.