Neuroscience 2004 Abstract
| Presentation Number: | 987.6 |
|---|---|
| Abstract Title: | Tuning to natural stimulus dynamics in primary auditory cortex. |
| Authors: |
Schnupp, J. W. H.*1
; Garcia-Lazaro, J. A.1
; Ahmed, B.1
1Lab. of Physiology, Oxford Univ., Oxford, United Kingdom |
| Primary Theme and Topics |
Sensory Systems - Auditory -- Auditory cortex: Neural processing and binauaral interaction |
| Secondary Theme and Topics | Sensory Systems<br />- Auditory<br />-- Auditory cortex: Perception, cognition, and action |
| Session: |
987. Auditory Cortex V Poster |
| Presentation Time: | Wednesday, October 27, 2004 2:00 PM-3:00 PM |
| Location: | San Diego Convention Center - Hall A-H, Board # EE15 |
| Keywords: | NEURAL CODING, SENSORY NEURONS |
In the 1970s, reports emerged that many aspects of “natural” sounds (e.g. envelope or pitch changes) exhibit “1/F” spectra (Voss & Clarke, 1975, Nature 258:317). Human listeners reportedly prefer “random melodies” where the pitch varies according to a 1/F spectrum to melodies with faster (1/F0) or slower (1/F²) dynamics (Voss & Clarke 1978, JASA 63:258). It therefore seems natural to conjecture that neurons in the central auditory system may exhibit some preference for 1/F dynamics, particularly as Yu et al reported 1/F tuning in primary visual cortex (SfN abstr. 2003 338.2).
To test whether neurons in primary auditory cortex (A1) exhibit tuning to 1/F dynamics we generated random tone complexes with frequency components at 1/2 octave intervals from 0.5 to 24 kHz, in which the fundamental frequency and the envelope fluctuated as a function of independent 1/Fx random walks”, with exponent x set to values between 0.25 (rapid fluctuations) to 4 (slow fluctuations). We recorded responses to 30 s segments of these dynamic complexes from several hundred single units in anaesthetized (domitor+ketamine) ferret A1 . Stimuli with different exponents were randomly interleaved. About half the units showed clear evidence of tuning, responding with higher firing rates to stimuli with exponents around x=1 to 1.5. Response rates of these tuned cells dropped off rapidly for faster (x<1) fluctuations, but declined only slowly for x>1.5, often reaching a plateau. 1/Fx tuned units appeared to occur in anatomical clusters, as some vertical electrode penetrations yielded large numbers of tuned cells while others yielded few or none. It was also noticeable that 1/F tuned neurons respond more reliably to stimuli with 1/F dynamics, in that the spike patterns evoked by repeated presentations of identical 1/Fx stimuli were a lot less variable if x took a value near 1.
To test whether neurons in primary auditory cortex (A1) exhibit tuning to 1/F dynamics we generated random tone complexes with frequency components at 1/2 octave intervals from 0.5 to 24 kHz, in which the fundamental frequency and the envelope fluctuated as a function of independent 1/Fx random walks”, with exponent x set to values between 0.25 (rapid fluctuations) to 4 (slow fluctuations). We recorded responses to 30 s segments of these dynamic complexes from several hundred single units in anaesthetized (domitor+ketamine) ferret A1 . Stimuli with different exponents were randomly interleaved. About half the units showed clear evidence of tuning, responding with higher firing rates to stimuli with exponents around x=1 to 1.5. Response rates of these tuned cells dropped off rapidly for faster (x<1) fluctuations, but declined only slowly for x>1.5, often reaching a plateau. 1/Fx tuned units appeared to occur in anatomical clusters, as some vertical electrode penetrations yielded large numbers of tuned cells while others yielded few or none. It was also noticeable that 1/F tuned neurons respond more reliably to stimuli with 1/F dynamics, in that the spike patterns evoked by repeated presentations of identical 1/Fx stimuli were a lot less variable if x took a value near 1.
Supported by BBSRC (UK) grant 43/S1959, a CONACYT scholarship to JAGL. Michigan probes from CNCT / NIH/NCRR grant P41 RR09754
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2004 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2004. Online.
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