Squiggly Lines- An Insight into Learning and Memory

In this episode, we were joined by Dr. Sam Cooke, a group leader and senior lecturer at King's College London, to discuss in vivo electrophysiology and its application to studying synaptic plasticity, learning and memory.

Listen to the episode here

In vivo electrophysiology is a technique used to measure electrical activity in the brain of a living organism. This method allows researchers to record the real-time functioning of neurons and neural networks, providing insights into how the brain processes information and responds to various stimuli.

Dr. Sam Cooke’s research interests have always been in learning, memory and the brain plasticity that subserves these processes. He received a PhD from the University College London (UCL), working in the laboratory of Professor Chris Yeo to reveal the locus and time-course of plasticity occurring in the cerebellum to support motor learning. Dr. Sam Cooke then moved to work with Dr. Tim Bliss at the National Institute for Medical Research (NIMR) on the role played by synaptic plasticity in the hippocampus during episodic learning and memory. From there, he moved to the US to work with Professor Mark Bear at the Massachusetts Institute of Technology (MIT), developing new assays to interrogate

neocortical processes of information storage by observing and intervening in plasticity as it

occurs in the learning animal. Dr. Cooke now head up a laboratory at King’s College London

(KCL), where he continues to pursue the biological basis of learning and memory in the

normal and disordered brain. His laboratory has developed a particular focus on plasticity in sensory systems that gives rise to its functional organization and cognitive processes such as habituation and novelty detection.

We discussed theories of synaptic plasticity, focusing on Donald Hebb's theory, first formulated in 1949, which remains the most influential theory of synaptic theory to date. Hebb proposed that synapses could be strengthened when the presynaptic activity is causally related to the postsynaptic activity, which occurs if the presynaptic neuron reliably fires prior to the postsynaptic neuron.

Drawings by Donald Hebb from his book "The Organisation of Behaviour"

Hebbian theory was followed by the experimental discovery of long-term potentiation (LTP) in 1973 by Bliss & Lomo, in which brief high-frequency stimulation of excitatory synapses produced a rapid and long-lasting increase in the strength of these synapses. We also discussed the importance of other forms of plasticity, such as homeostatic plasticity, that work together with Hebbian plasticity to maintain a stable system in the brain. You can read more about how Hebbian and homeostatic plasticity work together in this review.

Long-term potentiation following tetanic stimulation in hippocampal slices

In the episode, we also explored a major topic of Dr. Sam Cooke's research- habituation.

Habituation is a form of learning that is seen in all species. To study this, Sam has used in vivo electrophysiology to record neural activity from the visual cortex of mice as they habituate to the same visual stimulus that is repeatedly shown. This enables neural activity to be recorded in real time, which crucially allows the neural mechanisms underlying this process to be distinguished at different timescales (seconds, minutes, hours, days).

The squiggly lines in the title of the episode refer to the extracellular (local field potential, LFP) recordings that can be made from living awake mice.

Visually-evoked potential (VEPs) can be recorded from primary visual cortex as a mouse views an oriented grating (striped screen)

Here are some recent publications by Sam Cooke and colleagues:

• Electrophysiological Signatures of Visual Recognition Memory across All Layers of Mouse V1 (Hayden et al., 2023)

• Multiple Mechanistically Distinct Timescales of Neocortical Plasticity Occur During Habituation (Chaloner & Cooke, 2022)

• Stimulus-Selective Response Plasticity in Primary Visual Cortex: Progress and Puzzles (Montgomery et al., 2022)

You can also find out more about in vivo electrophysiology in this blog post in Scientifica's resource center, written by Francesca Chaloner who completed her PhD in in the Cooke lab:

https://www.scientifica.uk.com/neurowire/in-vivo-electrophysiology-benefits-weakness-and-alternative-solutions

This episode is part of a series sponsored by Scientifica, one of the leading producers of state-of-the-art electrophysiology and imaging tools. Scientifica supports researchers around the world to make advancements in neuroscience, cardiology, cancer research, and various other scientific areas. In addition to leading equipment and comprehensive support, Scientifica hosts an extensive Resource Centre dedicated to fostering the sharing of expertise, which is full of a wide range of blogs, videos, case studies, and much more! Be sure to check out their website for more information.