Evidence and Open Questions on Hippocampus–Cortex Dialogue

In this episode, we talk to Dr Daniel Bendor from University College London. Daniel's work focuses on rodent studies of place cells in the hippocampus. 

We discuss the phenomena of memory replay in which place cell activity mimics  patterns of activity that occurred while the rodent was performing a task in wake.  We also discuss how this process can be manipulated using targeted memory reactivation (TMR). 

From this we discuss how the TMR instead of triggering a reactivation of a memory could instead be biasing the brain to replay the memory which is cued. 

We go on to talk about the relationship between the cortex and hippocampus and discuss theories on the hippocampus training the cortex in putting together components  of memories and how this dialogue may take place. 

Throughout the episode, we discuss rodents as sleep models and the positives and limitations of using them compared to human/primate models.

Finally, we discuss links between TMR and brain washing and the possible worries this may cause. 

If you'd like to find out more about Daniel's work you can find a link to his university research profile.  Some key studies referenced in this episode below:

• Replay and TMR: https://www.sciencedirect.com/science/article/pii/S0960982219310358
• Enhance, Delete and Incept: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4058530/
• Biasing hippocampal replay: https://pubmed.ncbi.nlm.nih.gov/22941111/
• Mapping the future: https://www.sciencedirect.com/science/article/abs/pii/S1364661316000218

Glossary of terms from the podcast

Targeted Memory Reactivation (TMR) = the process of pairing sensory cues with learnt information to improve memory consolidation during sleep

Place cells = neurons in the hippocampus which fire when an animal is in a specific location, known as a place field.

Ground Truth = is empirical evidence or information collected from direct observation

Pattern Separation  = The differentiation of similar, overlapping neuronal activity into distinct, non-overlapping groups

Sharp Wave Ripples = waves seen in the hippocampus during sleep and rest

Engram =  a neuronal representation for the existence of  a memory

Type 1 error = known as a false positive , when a true hypothesis is rejected

Type 2 error = known as a false negative, when a false hypothesis is accepted

Spike-timing Dependent Plasticity  = the effect where the timing of neuronal spikes modifies a synapse in terms of magnitude and direction

Optogenetics = the process of modifying neurons so they can be activated and controlled directly by light



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Produced by Sophie Smith 

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