Re: Cochlear implants and pitch. (Bob Carlyon )

Subject: Re: Cochlear implants and pitch.
From:    Bob Carlyon  <bob.carlyon(at)MRC-CBU.CAM.AC.UK>
Date:    Tue, 27 Nov 2001 17:56:42 +0000

hi folks, There is some evidence at least that subjects hear a single pitch (Townshend et al, 1987, JASA 82, p106-115). When pulsatile stimulation is used, with pulses on the two electrodes nearly simultaneous (differing by 0.4 ms), then, provided the electrodes are quite close (<3 mm) one can vary the pitch monotonically by varying the relative current on the two electrodes (McDermott & McKay, 1994,JASA 96 p155-162) I suspect that at very wide electrode separations this would break down. Certainly, the temporal pitch pattern that listeners hear as a result of two interleaved patterns of stimulation on 2 electrode pairs, differs as a function of the electrode separation (at small separations they hear the "composite" pattern; at wide separations they do not; McKay & McDermott, 1996, JASA 100 p1081-1092) I'd also think that a better analogy in normal hearing would be two narrow bands of noise (or bandpass filtered pulse trains) with different centre frequencies cheers bob

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