Mechanisms of Memory

You will have seen a lot of cover on the science of education recently. Certainly that topic has been taking a lot of my time. However the other module I am enrolled in this semester is the ‘biological foundations of memory’.

I’ve been studying today the encoding of memories; specifically the electroencephalogram (EEP) readings for the encoding of memories. In this domain, the encoding of memories can be identified by a simple test. One presents images during a study phase, and then presents those images again, along with some novel ones, and asks participants if they have seen the said images before. By subtracting the brain waves recorded during the encoding phase (discriminated by the results of the test phase) of images subsequently recognised from those forgotten, one can measure the brain activity at given locations that represent memory encoding. Differences are discovered, as you might expect, but there’s more to it than that.

Another comparison, carried out by Yovel and Paller (2004) compared difference waves between familiar items, and recalled items, compared to items forgotten of the respective categories. Familiar items represent semantic memory (of meaning), whereas recalled items represent episodic memory. This is because as items are recalled, the participant remembers memorising them in the test phase. Indeed, as you can see below, there are some unique patterns for each category.

Yovel & Paller (2004)

Yovel & Paller (2004)

As far as our class goes, it is now mine to judge whether this represents a general unspecific mechanism or a number of specialised mechanisms.

Topographically, the recollection brain activity (which indicates episodic memory) completely encompasses the familiarity brain activity. Certainly the components of any episodic memory contain semantic components, so it is entirely logical that the components to process the episodic memories will activate semantic areas.

I don’t see any dissociations, however at the same time, these topographies span the entire brain, which is a bit big for one general mechanism. Based on that, I think the system breaks down into specific components which are actively connected during the episodic encoding experience.

So that is my synthesis. I don’t know what the most groundbreaking research might be saying about these concepts. It is likely that further experiments might be able to break this down and dissociate things further, however our lecturer is an active researcher in the field, so I imagine things are largely up to date. However I am going to leave matters at this conclusion for now.

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A Word on Evolution

Evolution is a popular word within science these days, and psychology is no exception. It seems that just about everything, whether it be neuropsychology or developmental psychology, can link theories back to our so called evolutionary past.

And it does kind of fit. The regions of our brains that carry out more elemental (similar to animal) roles are all centred around the medulla, which becomes the spinal cord. The further you come from the medulla, the more executive functions are performed, which might suggest from the evolutionary standpoint that new bits were built around the older parts.

Today I was reading on vision, and it astounded me just how spectacular the visual system is. Now the notion of evolutionary psychology suggests that the elements of the visual system for the transduction of colour came later on, that certain parts of the visual system are colour blind, and that through additional pathways the colour information is sent, to make a picture in our ‘minds’.

I just cannot grasp how such a system could uniformly form across an entire species by chance. The scientific primary colours, which according to theory, out of mere chance have constructed into the cones of the visual system, them selves through accidental genetic mutation, I honestly believe to be impossible. With no complete set of systematic steps, something has made itself out of genes that once upon a time had no trace of colour information.

Many a scientist now do look at the spectacularity of nature and of the human body, and feel conviction that a power of deity is having a bigger role than science would be comfortable accepting. I myself am a firm believer in Jesus Christ, belonging to the Church of Jesus Christ of Latter-day Saints. Information and ideas such as what I refer to here play no part in my conversion to that faith – empirical evidence for such does not exist, but I do marvel at the hand of my creator in such a spectacular organism as the human brain.

How we got Split-Brain Studies

One more cringe worthy surgery to contemplate might be Split-Brain surgery. A process by which neurosurgeons cut the corpus callosum, that then stops nerve fibres carrying messages from one side of the brain to the other. In epileptic people, quickened activity between both sides of the brain causes epileptic fits, and therefore, separating them, reduces the rate of epileptic seizures. (Calson, 2010)

The first research in this field was done by Bykov in the early 1900’s, where he worked in animals in Pavlov’s laboratory. By 1924 he had discovered that sectioning the corpus callosum in dogs prevented the contralateral skin related conditioning of salivary reflexes. (Glickstein & Sperry, 1960)

Corpus Callosum

The Corpus Callosum. Source: Psych Web

The first human case was reported in 1940 by Van Wagenen and Heeren, when the callosum was split as an attempt to cure epilepsy. The procedure was successful both in controlling epilepsy, and in finding new research on the corpus callosum. (North Dakota State University)

Years later, scientist Roger Sperry, and colleagues, performed further research in to split brained patients. They found that, although in day to day life, their behaviour seemed practically normal, that the cut off communication meant that the two half brains were actually operating independently of one another. Their work on animals showed that each half of the brain could be taught contradictory activities, with no perceivable mental conflict (Sperry, 1975).

The same behaviour is exhibited in humans. Post split-brain surgery patients have reported that their left hand seems to have a mind of its own. They may find themselves interestedly reading a book, yet then spontaneously, and through no conscious choice of their own, put it down. (Calson, 2010)

The different experiments performed, assessing responses to stimuli, opened up a whole new dimension of research, examining the brain in a new, not previously obtainable situation. The studies revealed where both sides of the brain are specialised. Sperry was awarded the Nobel Prize in Physiology or Medicine in 1981 (Horowitz, 1981).

What impresses me here is how a potentially controversial operation endured through the ages, to be not only acceptable, but also incredibly useful both in controlling epilepsy and understanding mind. If the idea were suggested today, ethical alarm bells might ring, yet through a century long research process, we now have scientifically grounded theories on the callosum and the two sides of the brain.

Is this a game that we have to play in order for research to gain widespread favour? Is that the way it should be? How much control do we have over what science achieves for humanity? It’s as if science itself is alive and kicking, an intelligence in its own right, with whom we work, that we might progress.

References:

Carlson, N. R., (2010), Introduction. In N. R. Carlson, Physiology of Behaviour (pp. 2-27). Boston, MA: Allyn & Bacon.