In <email@example.com> rhall at uvi.edu (Richard Hall)
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(He wrote an excellent correction of a prior post and extension of
the discussion, which I'll snip most of, but recommend readers
read his original post in its more readable format)
Towards the end, he said the following (to which I'll add something):
>-Consider heart rate. Vagal tone has immediate effect while elevated
>sympathetic activity has long lasting effects primarily on cardiac
>contractility. Indeed, studies of heart rate variability assume that
>frequency variations reflect sympathetic activity while high frequency
>variations reflect parasympathetic activity.
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>Comparative Animal Physiologist
>Division of Sciences and Mathematics
>University of the Virgin Islands
>St. Thomas, USVI 00802
>rhall at uvi.edu>>There are some interesting and useful consequences to this precise
parasympathetic control of hear rate.
For one example, the brief slowing coordinated to respiration (called
the sinus rhythm, I believe) has been used as an index of cholinergic
tone, in studies of head injury and a few other conditions.
For another example, the cardiac deceleration response (part of
Pavlov's orienting response) has been used to study perception in human
infant and other nonverbal animals: i.e., there is a very brief slowing
when the organism detects some stimulus change (e.g. a light going on,
OR going off; a tone abruptly changing in pitch or some other quality,
etc.). I used it in an attempt to determine whether comatose patients
(whose relatives are CONVINCED understand everything said to them) can
discriminate one word from another. First reported at International
Neuropsychological Association meeting, in Veldhoven, June of 1986, I
Maybe I'll add a bit more: in contrast to GSR, which many US
investigators used as a lazy man's index of an orienting reflex, the
cardiac response can unambiguously differentiate an ORIENTING reflex
from a DEFENSIVE reflex...
Some details in my chapter in "Windows on the Brain: Neuropsychology's
Technological Frontiers", NY Academy of Sciences Annals,1991, vol. 620.
F. Frank LeFever, Ph.D.
New York Neuropsychology Group