Exploring the content of human medial temporal lobe representations and their contributions to cognition

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Memory is a central part of everyday life and plays a critical role in shaping our personal identity. It is an essential goal of neuroscience, therefore, to understand how the brain processes memories and why our memories can fail. One long-standing theory is that a group of brain structures, collectively named the medial temporal lobe (MTL), are responsible for processing long-term memory only, effectively serving as a dedicated ‘long-term memory system'. Recent research has, however, challenged this idea, and demonstrated that, in some circumstances, the MTL is also involved in other cognitive domains, including perception, short-term memory, imagination, and decision-making. The current research proposal aims to take account of these findings and develop a theoretical framework by which the MTL's seemingly wide range of functions can be understood. Specifically, this work will build on a representational view of the MTL, which suggests that it is best to understand the MTL according to the type of information that it represents rather than the type of processes that it is responsible for. One suggestion is that different MTL structures are responsible for representing different types of information such as spatial scenes and objects, and that these representations are called upon whenever we make use of this information, irrespective of the cognitive process such as memory, perception, or imagination. Using a combination of behavioural and functional neuroimaging studies in neurologically healthy participants and individuals with memory problems due to MTL damage, this proposal will develop the representational view by: (1) Providing new insight into the content of MTL representations – what object and scene information is contained in MTL representations and can we examine what these representations look like?; (2) Revealing how MTL representations contribute to memory, in particular, their role in resolving memory interference – how do MTL representations help us to differentiate similar memories?; (3) Understanding how information about time is incorporated into MTL representations – how do MTL representations enable us to remember when and for how long a past event happened?; and finally (4) Shedding light on the role of MTL representations in imagination – how do MTL representations contribute to our imagination? The findings from this work will revise traditional conceptions of what the MTL does and in doing so, change our understanding of memory processing in the brain, and the interaction between memory and other cognitive processes. This knowledge will have an impact on research that is interested in the relationship between the brain and cognition in Canada and internationally, and in the long-term, may also speak to medical conditions in which memory impairment is a symptom.