Measuring for sound thought frequencies?

[alt_f13]

Think it is possible to test for frequencies being emitted by the brain for internal processing of sound?

 

For example, if I was thinking a sin wave at middle C (261.63 Hz) would it be possible for someone to look for that specific frequency within the brain to find out along what path, or in which general area it is being carried?

 

It seems to me that such a low frequency should stick out like a sore thumb amongst the brain's usual high frequency activity.

 

I also don't see how it is possible for me not to be producing that frenquency somehow when thinking/generating middle c in my brain, so why has this not been tested (or if it has... why aren't I carrying mp3s of the symphonies I generate on a nightly basis in my ipod?)

 

This would be a pretty sweet tool... no need for synthesizers any more.

[ashennell]

Think it is possible to test for frequencies being emitted by the brain for internal processing of sound?

 

Frequencies of what? I assume you mean firing rates or frequencies recorded from EEG's rather than actual sound waves.

 

For example, if I was thinking a sin wave at middle C (261.63 Hz) would it be possible for someone to look for that specific frequency within the brain to find out along what path, or in which general area it is being carried?

 

The cochlea (in the inner ear) recodes incoming soundwaves in a way not too dissimilar from applying a fourier transform to the input. this means that input arriving at the brain is essentially spead out across the neural inputs as a mapping based on the frequencies contained in the input signal - a spectrum. One subpopulation would code around 260 Hz and another would code slightly higher, etc., etc.

 

Given this, a single C note would be signalled by activity in a population of neurons, but the activity of these neurons does not need to be at 261.63 Hz, instead the peak (or local average) of activity would be at the neurons that represented this frequency in the spectrum.

 

There could be some extra phase locked activity but I really don't remember.

Somebody else may be able to provide a more accurate description of what occurs but I think this is basically correct.

 

The short answer : internal representations of stimuli do not have to have properties of the stimuli that create them.

[ashennell]

In addition ,

 

The maximal firing rate for a neuron is less than 1KHz which means that any soun dwith a frequeny greater than this cannot be encoded by firing frequency. I think the upper limit on human perception of sound is approx. 20000KHz.

 

Also, the lower frequencies, like middle C, would not stick out because these are the kind of frequencies that neuron opperate at.