12/21/2005

Hypnotic Lullabies

A friend asked "about the effects of vestibular stimulation on overall brain wave states (alpha, beta etc)? I'm trying to figure out if certain motions might actually help brain-wave entrainment (and particularly a reduction in brain activity). I know there are some playthings for hyperactive children that involve bouncing, swinging etc, that supposedly help the kid chill out."

It turns out to be a fascinating question.

This article by Talkowski, Redfern, Jennings and Furman in the Journal of Cognitive Neuroscience claims that the "vestibulo-ocular reflex" was "until recently ... considered automatic (i.e., free from the need for cognitive resources). However, patients with vestibular dysfunction often report mental fatigue, disorientation, and an inability to concentrate on cognitive tasks." Further they point to "clinical and empirical evidence suggesting an interaction between higher cognitive processes and the VOR and ocular motor systems. However, this interaction remains poorly understood."

One hypothesis would be that integrating sensory inputs from different modalities expends mental resources, and sure enough, even simple changes in posture can interfere with cognitive tasks: "combining standing and walking balance tasks with mental arithmetic, visuospatial tasks, reaction time (RT) tasks, word recall, and verbal response tasks" has significant effect.

So do these bouncing, swinging toys calm children through mental fatigue or sheer physical exertion?

I think there are reasons to suspect there is also a cognitive as opposed to purely physiological effect. Auditory and vestibular signals are both processed in the superior temporal gyrus. What follows is a a purely anecdotal argument: one can imagine that lullabies and a rocking cradle could stimulate the same area. In the same way, even popular depictions of hypnosis - swinging watch and all - could theoretically entrain dominant EEG's downward via vestibulo-ocular rhythms.

But such analogies are not really necessary. If you accept the connection between "mental fatigue" and lower average EEG rhythm (as in sleep) then the dots connect themselves: excess vestibular stimulation results in fatigue, which ultimately results in lower EEG rhythms overall.

3 Comments:

Anonymous Chris Tregenza said...

A very interesting question.

Vestibular / cerebellum training is a signficant part of many approaches to dyslexia and ADHD. There are also approaches such as sound and light therapy which may involve aspects of entrainment.

I wonder what research there is on brain wave activity on marthon runners. Is the trance state or 'zone' reached during excercise effected by the frequency of movements or is it purley endorphins and exhustion?

1/06/2006 03:53:00 AM  
Blogger Chris Chatham said...

Chris - The articles on your site relating rhythm and timing to dyslexia are incredibly interesting. I wasn't aware of any of this work and I find the whole "sensory integration" hypothesis fascinating.

Re: the marathon runners, I can only speculate, as a quick search on PsycInfo for combinations of the keywords entrainment/endorphins/marathon/EEG turns up relatively little that seems relevant.

I did however find an article called "Respiratory Rhythm Entrainment by Somatic Afferent Stimulation" which shows that the lateral parabrachial nucleus is necessary for respiratory rhythm entrainment through somatic input (such as running), through its action on "E2" and "Post-I" neurons. I am not very familiar with this research or these regions so honestly I am not sure what this means in the bigger picture context of our discussion. I can tell you that locomotor entrainment is an established scientific phenomenon (though of course runners have known it's real for quite some time), and according to this article is mediated by some entrainment in midbrain/brainstem regions, but it's unclear how this might or might not interact with global EEG frequency in higher cortical areas, which is probably what's behind "the zone."

Anyway, my guess would be that endorphins would actually counteract any effect that locomotion has in slowing EEG global frequency, but for all we know, the marathon "zone" could be a consequence of 40 Hz (gamma) coherence as opposed to 3-8 Hz (delta/theta) coherence. There's just no research that I could find on this particular topic.

1/06/2006 08:10:00 AM  
Anonymous Anonymous said...

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3/02/2006 08:36:00 AM  

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