Effects of Music

Richard Hall rhall at uvi.edu
Sun Jan 26 00:18:24 EST 1997


lkh wrote:
>It is the biological clock basis of the CORE Technology intelligent
>processing technique in wave computation. It is within the range of
>Crick-Llinas 33-80hz frequencies.
>
>Input receptors take samples twice a second. A 60 hz rate means 30:1
>to input. With input being correlational oppostion that is 2x 30:1 or
>120 bmp.

rlh inquires:

I am still perplexed by the 60-120 hz number for brain computation cycles.
Is the CORE Technology intelligent processing technique using a fourier
type of analysis on brain waves?  I do not understand how a preferred
musical frequency of 60-100 beats per minute (1-1.4 hz) relates to a either
central processing cycle of 60-120 hz or the Crick-Llinas 33-80 hz
frequencies.

While trying to resolve this I have been slowly considering the behavior of
several sensory and central systems.  The numbers do not seem consistent
with high frequency through put.

Granted the auditory system has unusual properties capable of resolving
frequencies up to 50,000 hz in some bats. If sampling theory dictates 2
sampling intervals to resolve one event,the poor bat would need a brain
cycling at 100,000 hz to differentiate frequencies. Human speech employs
optimal sound frequencies between 200-4,500 hz and we can discriminate up
to 15,000 hz, but no one argues that bats are more intelligent than humans.


Why would higher processing speeds be needed?  Auditory receptor cells lack
generator potentials and reception is first integrated by spiral (auditory)
neurons projecting into the cochlear nucleus which maps frequency
topographically. Integration typically has a longer time course since most
neuron-neuron inputs are characteristically subthreshold and rely on
summation to elicit postsynaptic responses.   Since axons cannot sustain ap
much faster than 300 hz, our inputs must be indexed to frequency rather
than mimic stimulus frequency. Indeed, human auditory nerves typically max
out at 100 hz even when representing sound frequencies in excess of 10,000
hz (Lieberman, 1978.)

Spike trains can have high frequencies.  The absolute refractory periods of
neurons are typically 3-5 ms thus axons may have action potentials (ap) at
frequencies of up to 200 or 300 hz.  Still these ap are usually grouped in
short bursts. Post synaptic responses have longer time courses which can
further modulate high frequency input. Recordings of thalmocortical
responses to tactile stimulation show ap bursts that may exceed 60 hz. If
cortical processing is between 60 and 120 hz, a slight phase shift could
miss most of that information and create a false signal at a weird
frequency a process known as aliasing.  I would wager the cortex cycles
slower than the frequency of inputs and thus avoids aliasing errors by
integrating inputs over time.  Again the brain indexes reality as a complex
pattern as might be expected by the massive volume of cerebrum dedicated to
association cortices.

Graded synaptic transmissions are much more common in the brain cortex than
spike driven transmission (as you have pointed out several times) and
graded potentials typically decay within 30-300 ms, again resulting in 3-33
hz as the maximium rate for discriminated signal transmission.  Beta waves
fall somewhere in the 13-25 hz range and correlate with an active brain.
Graded transmission with long duration and lack of refractory periods is
perfect for rapidly turning high frequency inputs in to proportionate
release of neurotransmitter.  Since brain waves are based on graded
potential changes these time constraints appear consistent with a brain
processing model operating at 30 hz tops.

The human preference for ritual music with a 1.4 hz beat over something
"faster" may reflect something besides tuning curves of cochlear neurons or
the cycles the brain flops information per second. I still like the
correlation with heart rate, which incidently is influenced by brainstem
activity just as is arousal of the sleepy brain.

My point is that 60-120 hz seems to be a high estimate of central
processing clocks based on the properties of individual synapses and fairly
complex isolated neural preparations regardless of input frequency. The
massively parallel solution that has evolved in vertebrates may tolerate or
thrive at much slower sampling rates, eg. 1-30 hz.  Actually, slower
sampling rates would make massively parallel darn near essential.

Why then are the Crick-Llinas 33-80hz frequencies considered central to
information processing?  From my arm chair, the CORE Technology intelligent
processing technique seems simply empirical.

Incidently, I have been exploring your web sight at my accustomed
processing rate of 1 hz ;-).

rlh

"Anyone interested in publishing my life story will first need to pay off
my master card account."

Richard Hall
Comparative Animal Physiologist
Division of Sciences and Mathematics
University of the Virgin Islands
St. Thomas, USVI  00802

809-693-1386
rhall at uvi.edu





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