Topic: concept cells

The human medial temporal lobe contains neurons that respond selectively to the semantic contents of a presented stimulus. These "concept cells" may respond to very different pictures of a given person and even to their written or spoken name. Their response latency is far longer than necessary for object recognition, they follow subjective, conscious perception, and they are found in brain regions that are crucial for declarative memory formation. It has thus been hypothesized that they may represent the semantic "building blocks" of episodic memories. In this talk I will present data from

My talk will consist of three subtopics. The brain remembers episodes not in isolation but with their contextual relationships, such as spatial or temporal proximity. This is an essential feature of the brain’s memory, but the underlying mechanism is yet to be explored. Cell assemblies, or engrams, may provide neural representations for such relationships. First, I will show a class of associative memory models that encode and retrieve multiple memory contents linked by an arbitrary graph structure through experience and demonstrate the crucial role of the balance between two inhibitory subnet

Since the identification of concept cells nearly two decades ago [1], the semantic invariance of single neurons in the human medial temporal lobe has been extensively investigated [2, 3]. Such investigations typically consist of an initial screening to identify semantically-tuned neurons and a subsequent follow-up experiment which uses the identified stimulus-response pairings to address a particular question. While often examined in the service of other scientific investigations, the initial screenings have rarely been the sole focus of investigation [4]. Given the challenges endemic to human

Reinstating details of previously seen stimuli given a recall cue is a common cognitive function. Studies suggest that such recollection involves hippocampus-mediated top-down reactivation of neural ensembles active during encoding, yet the neural mechanisms of such generative retrieval remain unknown. We formulate a biologically plausible hypothesis where transient cholinergic modulation, known to enhance backpropagated action potentials and trigger recall, initiates backward signals from sparse neurons discriminatively representing the cue to cortical areas encoding the trace. These signals

Humans can infer never-experienced global relational structures (e.g., "A>D”) by observing and integrating multiple local relations (e.g., "A>B", "B>C", “C>D”). This capability for “transitive inference” (TI) depends on the medial temporal lobe (MTL). But the mechanisms by which the MTL performs TI remain poorly understood. Previous work suggested that “concept cells” (CCs), which are neurons that selectively respond to preferred concepts (e.g. “A”), might contribute to relational learning and potentially TI by widening their tuning to new concepts that co-occurred with initially r