Monday, January 21, 2008

Hippocampus, theta waves and movement V

In 1957 a paper appeared (Scoville and Milner) "claiming that hoppocampal lesions produced amnesia." In a paper two years later, Vanderwolf says:
"Grastyan and his colleagues reported that hippocampal rhythmical slow waves were characteristic of the early stages of learning when the cats displayed prominent orientating reactions (the what-is-it reactions of Pavlov) but that both the orienting responses and the associated rhythmical slow waves disappeared when the learned behavior had become well seemed to me that a different interpretation was more probable. Early in training, extensive exploratory movements such as walking, rearing, and head movement are likely to occur but later when the learned behavior is well-established, unnecessary motor activity tends to disappear."

It seemed researchers were trying to link hippocampus with learning and memory. Vanderwolf didn't buy this. He had already noted the sorts of movements that were associated with hippocampal slow wave formation, and reasoned that
"if one were to compare the electromyographic activity of somatic muscles during spontaneous behavior before and after training, extensive changes would, no doubt, be observed but this would not mean that muscles are directly involved in learning and memory. Similarly, training-induced changes in hippocampal activity may be a consequence of a role played by the hippocampus in control of motor activity."

Vanderwolf devised a way to test his hunch, providing data that showed hippocampal slow wave present during continuous running or walking. If the animal stopped moving the hippocampal rhythmical waves were always interrupted. Long-continued practice didn't necessarily result in disappearance or even any change at all in the rhythmical slow waves of the hippocampus. His data re-confirmed that hippocampal slow wave activity was present during "varying untrained spontaneous motor acts".

More about this to follow.

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