Sunday, January 13, 2008

Hippocampus, theta waves and movement III

A description of the following rat behaviors and accompanying rhythms appears next.

Sleep to waking:

1. Sleep: neocortex waves went from low voltage fast activity to large amplitude, irregular slow waves.

2. Startle out of sleep with a noise: rat
"would leap to its feet, startled, its head up, eyes wide open, then stand motionless."
Large slow waves of the neocortex were replaced by low voltage higher frequency record (neocortical activation) but no rhythmical waves from hippocampus, instead a pattern of irregular waves with low amplitude.

From this Vanderwolf concluded that
"the rhythmical hippocampal waves had nothing to do with arousal or alerting; they were specifically related to a class of movements that did not include the startle response."

During movement:

3. In the waking rat: sensory stimuli generally elicited hippocampal rhythmical slow activity only if they also elicited a certain type of motor activity.
".. a great variety of visual, auditory, tactile and olfactory stimuli elicited both hippocampal rhythmical slow activity and a behavioral response that included head movements, stepping and locomotion."

4. Rats hung vertically by their front paws: No hippocampal activity was recorded while they just hung there, front paws clutched over the top of a vertical board.
"Rhythmical waves always appeared, however, when a rat pulled itself up, climbing to the top of the board."

Vanderwolf concluded that rhythmical hippocampal waves accompany certain phasic movements not static muscular exertion. Furthermore, maintenance of an immobile standing posture on two legs or four, was not associated with rhythmical slow hippocampal activity.


5. Grooming: Rat sits up on hind legs and uses front paws to rub its mouth, face, eyes and whiskers, followed by nibbling of own flanks, hind legs, abdomen. Movements are vigorous, but generally not accompanied by rhythmical hippocampal waves. By contrast, while resting, even just a small movement of one forepaw was regularly accompanied by rhythmical hippocampal waves.

Conclusion: two qualitatively distinct classes of behavior: one accompanied by waves and one not.

6. Grooming: occasional bursts of clear rhythmical waves lasting a second or two at most, occurred during long grooming sessions. They were accompanied by changes in posture, transitions from the rat paying attention to/grooming one area of the body, to paying attention to/grooming another area.

Conclusion: rat grooming behavior consists of two kinds of movement, 1) stereotyped licking, biting fur, rubbing of forepaws over face, without hippocampal slow wave; 2) changes in posture, accompanied by rhythmical slow activity in the hippocampus.

7. Grooming behavior, plus startle: Two possible reactions: rat becomes immobile (freezing behavior) without hippocampal slow wave accompaniment, however, if head movements or locomotion were chosen by the rat, rhythmical waves would appear.

Eating and drinking:

8. Approach to food, snatching it, running off with it: continuous rhythmical waves were recorded.

9. During chewing and handling of food with forepaws: Rhythmical hippocampal activity was present at the onset of eating a large food pellet, but as the pellet got smaller so did the hippocampal activity.

10. Sniffing behavior: vigorous sniffs with small head movements - no associated slow rhythmical wave from hippocampus associated.

11. Approach to/retreat from water dish was accompanied by rhythmical hippocampal waves but not the act of drinking itself.

12. Rhythmical hippocampal waves were found to have no specific relation to exploratory behavior in general sense. On the other hand, changing posture of head while eating or changing posture while grooming are well-practiced and are accompanied by slow wave activity.

Next, Vanderwolf looked deeper at premotor activity.

No comments: