What do human hippocampal neurons code?

What do human hippocampal neurons code? 
Theme: Cognition and behaviour

Sunday 23rd April, 16:20 – 18:00
Session convened by the British Association of Cognitive Neuroscience

The hippocampus is an essential hub for the flexible association of concepts. This flexibility makes the hippocampus crucial for a variety of tasks, such as episodic memory, learning, and language processing. However, an important question remains unanswered: how do single neurons in the hippocampus code information? Two different sub-types of human hippocampal neurons have been identified in the literature. (A) Concept Neurons show consistent responses to specific persons and concepts independent of context (e.g. a neuron coding for Jennifer Aniston responds to completely different pictures of her and in different situations). Recently Dijksterhuis and colleagues have shown that Concept Neurons are even more adaptable than we have previously thought. Concept Neurons are activated when a pronoun refers to the concept the neuron is tuned to (e.g., “she” when it refers to Jennifer Aniston). According to Quiroga the concurrent activity of multiple of these Concept Neurons code for the diverse elements that make up an episodic memory (i.e., one set of Concept Neurons for Jennifer Aniston, one for your favourite café, one for the music playing in the background). (B) Kolibius and colleagues showed that the various elements within an episode are bound to a unique neuron assembly, termed Episode Specific Neurons. In contrast to Concept Neurons this conjunctive code represents the entire experience (i.e., one set of Episode Specific Neurons that codes for the memory when you had a coffee with Jennifer Aniston in your favourite café and music was playing in the background). Alternatively, these hippocampal neurons might be a product of a general clustering learning mechanism in the human hippocampus. Mok and colleagues report exciting new work supporting this idea based on computational models.

  • Luca Kolibius, University of Glasgow, UK: Hippocampal neurons code individual episodic memories in humans (co-chair)
  • Rodrigo Quian Quiroga, University of Leicester, UK: Concept neurons as the building blocks of declarative memory (co-chair)
  • Doris Dijksterhuis, Netherlands Institute for Neuroscience, UK: Pronouns reactive concept cells in the human medial temporal lobe
  • Robert Mok, University of Cambridge, UK: How the hippocampus encodes concept and spatial representations: a multi-level account from behaviour to neurons

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