Sound frequency representation in cat auditory cortex.
Using the intrinsic signal optical recording technique, we reconstructed the two-dimensional pattern of stimulus-evoked neuronal activities in the auditory cortex of anesthetized and paralyzed cats. The average magnitude of intrinsic signal in response to a pure tone stimulus increased steadily as the sound pressure level increased. A detailed analysis demonstrated that the evoked signals at early frames were scaled by the sound pressure level, which in turn indicated the presence of a minimum level of sound pressure beyond which stimulus-related intrinsic signal can be generated. Intrinsic signals evoked significantly by pure tone stimuli of different frequencies were localized and arranged in an orderly manner in the middle ectosylvian gyrus, which indicates that the primary auditory field (AI) is tonotopically organized. The arrangement of optimal frequencies obtained from optical recordings of the same auditory cortex, which were conducted on different days, was highly reproducible. Furthermore, other auditory fields surrounding AI in the recorded area were allocated based on the observed tonotopicity. We also conducted unit recordings on the cats used for optical recording with the same set of acoustic stimuli. The gross feature of the arrangement of optimal frequencies determined by unit recordings agreed with the tonotopic arrangement determined by the optical recording, although the precise agreement was not obtained.
Tsytsarev
Vassiliy
V
Laboratory for Visual Neurocomputing, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.
Yamazaki
Tadashi
T
Ribot
Jérôme
J
Tanaka
Shigeru
S
D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000502:physiology*; D001306:Auditory Pathways / Q000502:physiology; D001309:Auditory Threshold / Q000502:physiology; D001931:Brain Mapping; D002415:Cats; D005072:Evoked Potentials, Auditory / Q000502:physiology; D006179:Gyrus Cinguli / Q000502:physiology; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008144:Loudness Perception / Q000502:physiology; D009474:Neurons / Q000502:physiology; D010898:Pitch Perception / Q000502:physiology*; D013017:Sound Localization / Q000502:physiology; D013018:Sound Spectrography; D041623:Tomography, Optical Coherence; D014741:Video Recording