Date: Mar 20, 2019 3:00pm-4:30pm
Location: Dunton Tower: Room 2203
Speaker: Anna Blumenthal
Title: Object processing in the medial temporal lobes: influences of object domain
Abstract:
We live in a rich visual world, surrounded by many different types of objects. The domain to which an object belongs, for example whether it is animate or inanimate, matters for how we perceive and interact with that object. This is reflected in an object domain based neural organization of our visual system. While this domain level organization has been well characterized in posterior aspects (e.g., a tripartite schema of the ventral visual stream), it has not been systematically explored across anterior medial temporal lobe (MTL) structures. This is surprising, given these structures are important for object perception and memory, and according to some theories can be considered the apex of the ventral visual stream.
In my talk, I will present two projects that explore the role of object domain in the MTL. In the first project, we used fMRI to explore whether object evoked responses in three MTL structures, namely, perirhinal cortex, parahippocampus, and hippocampus, were organized by animacy, and/or real-world size for inanimate objects. We found domain-level organization in all three MTL structures, with a distinct pattern of domain organization in each structure.
In the second project, we characterized a unique contribution of the hippocampus to object concepts, specific to the nonliving domain. We tested two individuals, HC, who has selective hippocampal damage that occurred early in life, and NB, who has MTL damage sparing the hippocampus, on two tasks that tap into feature knowledge of object concepts. We found that HC has less extrinsic feature knowledge of objects, in other words, knowledge external to, but associated with the object (e.g., “pound nails” is an extrinsic feature of a hammer). Additionally, HC made abnormal feature-based judgements specific to non-living object concepts, concepts which rely on extrinsic feature knowledge. NB did not differ from controls on either task. These results suggest that the hippocampus may play an important role in the development of non-living object concepts, potentially through the same relational binding mechanism that links objects and context in episodic memory.
Taken together, these findings suggest that understanding the role of object domain across MTL structures may be a useful approach for gaining a deeper understanding of the similarities and differences between MTL structures, and how they contribute more broadly to our perception and memory of the world.