Time and space (Pierre Divenyi )

Subject: Time and space
From:    Pierre Divenyi  <marva4!EarLab!pierre(at)UCDAVIS.EDU>
Date:    Fri, 6 Jun 1997 11:55:15 GMT

Dear Neil, Indeed, it would be nice if the state-of-the-brain were as you describe it: low-level time and frequency analysis represented orthogonally in the cortex. While it is true that Gerald Langner has found single units in his animals, and that the human MEG data look at least consistent, he would be the first to say loud that your generalization of the data are scarcely more than wishful thinking. In particular, the time ranges some of us have been talking about during the present exchange of views go down to very-very low frequencies (=periods as long as 100-200 ms) which, as far as I know, have not been found to be well represented at the CN or the IC -- but correct me if I am wrong. Furthermore, even if all you say about auditory time/frequency analysis in the cortex, there is still the phenomenon Al and I were referring to to explain: temporal (i.e., envelope-) patterns marked by signals in different frequency bands tend to divide into two streams and suffer a loss of discriminability. Having done lots of experiments on the latter, and having tried to model the situation, the phenomenon in question looks as if what we hear (=the perceived temporal patterns) were mediated by an extra stage whenever the markers do not activatte the same pool of neurons. Again, I would not object to the view that this extra stage is also located at a subcortical level, but you must admit that the data are not there to support the view (at least I haven't seen them in the time range we are talking about). Thus, a more parsimonious explanation, to my mind at least, would be to make the cortex responsible for keeping track of envelope timing information altogether. Pierre

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Electrical Engineering Dept., Columbia University