In article <4l5o23$r1d at vixen.cso.uiuc.edu>, Kevin Spencer (kspencer at s.psych.uiuc.edu) writes:
>gord at homostudy.win_uk.net (G K GRAY) writes:
>>>>>In article <4l3g00$el4 at vixen.cso.uiuc.edu>, Kevin Spencer (kspencer at s.psych.uiuc.edu) writes:
>>>Emery Carr <ecarr at infohwy.com> writes:
>>>>>>>The only info. I have found so far is that 200hz and 210hz will cause a
>>>>frequency following response of 4hz in the brain.
>>>>>>Hmm, never heard of that one before.
>>>Why should we *not* expect to find a 4hz response in the brain when those
>>who tune musical instruments have been using this "beat" phenomenon for
>>generations to perform this task, or am I misunderstanding the question?
>>The effect can be measured physically and organically.
>>The 4 Hz response Emery referred to is in the EEG. Certainly people can
>perceive auditory stimuli at 4 Hz, but it doesn't necessarily mean that the
>EEG is entrained at that frequency.
>>Reply to; gord at homostudy.win-uk.net
OK - So it appears in the EEG. As I read the original that started
this, the acoustic 200hz enters one ear, the 204hz into the other
and we get the 4hz EEG along with the original pair as
corresponding EEGs. There must be information pathways that compare
the signals coming from the 2 ears, *but this linkage is not
necessarily relevant to the beat phenomenon*, rather to the need to
determine the *source* of a sound - which is of *vital importance
to survival*. The neural circuitry that achieves this - discrepancy
detectors (in "computerese" - NAND circuits) is well understood
and the 4hz EEG is just a bonus for piano tuners. It also accounts
for our experience of the Doppler Effect.