Optical imaging of intrinsic signals in ferret auditory cortex: responses to narrowband sound stimuli.
This paper describes optical imaging of the auditory cortex in the anesthetized ferret, particularly addressing optimization of narrowband stimuli. The types of sound stimuli used were tone-pip trains and sinusoidal frequency and amplitude modulated (SFM and SAM) tones. By employing short illumination wavelengths (546 nm), we have successfully characterized the tonotopic arrangement, in agreement with the well-established electrophysiological tonotopic maps of the ferret auditory primary field (AI). The magnitude of the optical signal increased with sound level, was maximal for a modulation frequency (MF) of 2-4 Hz, and was larger for tone-pip trains and SFM sounds than for SAM sounds. Accordingly, an optimal narrowband stimulus was defined. Thus optical imaging can be used successfully to obtain frequency maps in auditory cortex by an appropriate choice of stimulus parameters. In addition, background noise consisting of 0.1-Hz oscillations could be reduced by introduction of blood pressure enhancing drugs. The optical maps were largely independent of 1) the type of narrowband stimulus, 2) the sound level, and 3) the MF. This stability of the optical maps was not predicted from the electrophysiological literature.
University Laboratory of Physiology, University of Oxford, Oxford OX1 3PT, United Kingdom. huibv@mbfys.kun.nl
Huib
H
Versnel
Jennifer E
JE
Mossop
Thomas D
TD
Mrsic-Flogel
Bashir
B
Ahmed
David R
DR
Moore
D000161:Acoustic Stimulation / Q000379:methods; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D016477:Artifacts; D001303:Auditory Cortex / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D005289:Ferrets; D008297:Male; D055095:Optics and Photonics; D009991:Oscillometry; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014666:Vasomotor System / Q000187:drug effects / Q000502:physiology
D014662:Vasoconstrictor Agents; D000804:Angiotensin II