Stimulus-dependent central processing of auditory stimuli - A PET study

Positron emission tomography (PET) was used to investigate the neural syste ms involved in the central processing of different auditory stimuli. Noise, pure tone and pure-tone pulses, music and speech were presented monaurally . O-15-water PET scans were obtained in relation to these stimulations pres ented to five normal hearing and healthy subjects. All stimuli were related to a basic scan in silence. Processing of simple auditory stimuli, such as pure tones and noise, predominantly activate the left transverse temporal gyrus (Brodmann area [BA] 41), whereas sounds with discontinued acoustic pa tterns, such as pure-tone pulse trains, activated parts of the auditory ass ociation area in the superior temporal gyri (BA 42) in both hemispheres. Mo reover, sounds with complex spectral, intensity, and temporal structures (w ords, speech, music) activated spatially even more extensive associative au ditory areas in both hemispheres (BA 21, 22). PET has revealed a remarkable potential to investigate early central auditory processing, and has provid ed evidence of the coexistence of functionally linked, but individually act ive parallel and serial auditory networks.