ATTENTIONAL MODULATION OF THE MEDIAL TEMPORAL LOBE

Abstract

Attention prioritizes information that is most relevant to current behavioral goals. This prioritization can be accomplished by amplifying neural responses to goal-relevant information and by strengthening coupling between brain regions involved in processing this information. Such modulation occurs within and between areas of visual cortex, and relates to behavioral effects of attention on perception. However, attention also has powerful effects on learning and memory behavior, suggesting that similar modulation may occur for memory systems. In fact, not much is known about how attention modulates representations in specialized memory systems, such as the medial temporal lobe (MTL). The goal of this thesis is to make progress in our understanding of how attention might help bridge between perceptual and memory systems. Across three fMRI studies, we investigated attentional effects in the MTL. We first examined how selective attention modulates interactions between visual and memory systems in the human brain. By measuring background functional connectivity between visual cortex and MTL cortical regions while participants selectively attended to one of two categories in composite images, we show that different cortical input structures in the MTL interact with visual cortex depending on which of the two visual categories is task-relevant. We then employed a statistical learning paradigm and showed that such modulations in connectivity relate to behavioral evidence of learning about visual regularities. Finally, inspired by the fundamentally relational nature of episodic memory, in a third study we investigated the role of the hippocampus in visual attention to different kinds of relations. We performed univariate and multivariate analyses of evoked activity in the MTL and found that the hippocampus differentiates between relational and item processing even during online visual perception, thus showing another way in which top-down attention can affect the MTL. Together these studies represent a focused investigation about attention in the MTL, and have the potential to advance our understanding both of memory systems as well as models of attention.