Nuggets about memory

Two areas that lie at the heart of understanding object handling are the notions of memory and association. Unfortunately, these topics seem to be at the limits (or perhaps beyond the limits) of scientific understanding of human thought. Some stuff is known and while some of that stuff is helpful, other bits of information open up new areas of unknowing.

This is all from: O’Shea, M. (2005) The Brain: A Very Short Introduction, Oxford: Oxford University Press

So, the myserious bits:
The cerebellum is a part of the hindbrain and is a structure specialised for the coordination of motor commands. It is richly supplied with sensory information about the position and movements of the body and can encode and memorise information for the execution of complex learnt skills.The cerebellum has no direct link with the cortex This said, the basal ganglia (which is part of the forebrain) serves to control and regulate voluntary movements initiated by the cerebral cortex.

Fairly straightforward so far…

Episodic memory (stored somewhere, somehow in the cortex) can be stimulated by smell. This is well known. “Exactly why this should be so is unclear, as the sense of smell is not well developed in humans and it links with primitive brain centres in the hypothalamus.” (The hypothalamus lies deep within the brain and is involved in sensory experience and emotion – it releases a number of hormones into the blood supply to be distributed around the body.

This is the mysterious bit: why do learned movements and smell – which are mediated through parts of the brain which are remote from the cerebral cortex – evoke memories so effectively in the cerebral cortex?

In the same book there are some useful bits about the basic mechanics of memory, which I think are relevant to this project.

O’Shea relates some research that has taken place on sea slugs which has clarified the mechanisms underlying learning/association. So… We have these cells called neurons, they have bits that reach out to other neurons called axons, at the end of the axon is the bit which makes contact with another neuron called a synapse. The synapse uses electro-chemical processes to stimulate the next neuron. Depending on the neurons that act of stimulation can have various consequences. In the sea slug there are simple arrangements where sensing neurons stimulate motor neurons so that if they are touched they retract from the source of the touch. The researchers found that there were different mechanisms for short- and long-term changes in behaviour. Short-term changes in behaviour were caused when the sensing neurons released chemicals that changed the rate of the synapse action. Long-term changes were caused when messenger molecules within the sensing neurons led to the creation of new synapses acting on the same motor neuron so that the reaction was strengthened.

This helps understand the basic mechanisms of memory and association but it doesn’t really clarify large scale memory storage and the way that lots of separate ideas and experiences are associated within our brains.

(O’Shea made another comment, which is worth putting down. He pointed out some of the limitations of fMRI. There is a tendency to use fMRI to see which bits of the brain are active during some process or activity and then say “that bit of the brain must be involved somehow”. O’Shea pointed out that whilst this may be true, fMRI measures blood flow activity and the dilation rate of blood vessels in the brain can be much slower than the response rate of neurons. So the link between the observation and the process must be treated with care. An academic from Durham Uni, who I spoke to a while ago, also pointed out that the spatial resolution of fMRI scans is relatively coarse and this is another cause for care.)

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About Bruce Davenport

Museum educator and researcher.
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