Abstract

In this talk I will present two strands of studies where we investigated two prominent mechanisms suggested to underlie human episodic memory. First, Hebbian learning (i.e “fire-together, wire together”) or Spike-Timing-Dependent-Plasticity (STDP), which posits that the firing of neurons in close temporal proximity is crucial for laying down a memory trace. Recording the co-firing of single-neuron in epilepsy patients in the medial-temporal-lobe during a memory task we found results that are consistent with STDP . I will also show results from rhythmic stimulation studies demonstrating that the manipulation of temporal patterns in the range of milliseconds modulates episodic memory formation. A second idea that has influenced memory research is the “Indexing Theory” which posits that the human hippocampus stores episodic memories via an Index – an agnostic conjunctive type of code that points to the different elements that belong to the episode. I will present recent evidence from human single neuron recordings where we found neurons that are consistent with such an indexing function. I will also present unpublished results from an ultra-highfield fMRI at 7T which support these human single unit findings and suggest that the Index is predominantly located in the hippocampal subfield CA3 . I will close the talk by presenting a recent theoretical framework where we integrate these findings with Concept Cells (so-called Jennifer Anniston cells) and the Engram Allocation Theory. At the end I will speculate how results from both streams could lead to the development of novel treatment for patients with memory problems.

Host: Denes Szucs (ds377@cam.ac.uk)

This talk will be recorded and uploaded to the Zangwill Club Youtube channel in due course.