This project seeks to explore the functional organization of multiple representations in the auditory cortex of rhesus monkeys using physiological, anatomical, and behavioral techniques. Neurons in the rostral area (R) of the supratemporal plane respond preferentially to low-frequency tones, whereas neurons in the caudo-medial area (CM) of the supratemporal plane prefer high frequencies. A combination of lesioning and tracer injections into matched frequency representations have revealed different inputs from the medial geniculate nucleus (MGN) of the thalamus into areas R and CM, with CM depending more than R on input from primary auditory cortex (AI), which lies between the two. In the lateral belt areas of auditory cortex, which receive input from both R and AI, most neurons do not respond well to pure tones. Instead, units in this region can be driven briskly by bandpass-filtered noise (BPN) pulses. Using this new type of stimulus, cochleotopic maps can be revealed along the antero-posterior axis in three lateral areas, which we have termed AL, ML, and CL. Neurons are tuned to a best center frequency of the BPN bursts, a dimension that is represented along the rostro-caudal axis. They are also tuned to a best bandwidth of these bursts, which is represented orthogonally to best center frequency, i.e. along the medio- lateral axis. Neurons in the lateral belt areas also respond well to frequency-modulated (FM) sounds and show selectivity for the rate and direction of FM stimuli. Noisy pulses and FM sounds are essential components of many species-specific communication calls, and neurons in the lateral belt areas often respond selectively to such calls as well. Filtering the communication sounds in specific ways has revealed the existence of combination-sensitive neurons. Finally, we have successfully trained monkeys on an auditory recognition memory task; this development will permit us to study auditory perception and memory electrophysiologically in behaving monkeys and, through lesion analysis, the cortical regions involved in these two different auditory functions.
| Munoz, Monica; Mishkin, Mortimer; Saunders, Richard C (2009) Resection of the medial temporal lobe disconnects the rostral superior temporal gyrus from some of its projection targets in the frontal lobe and thalamus. Cereb Cortex 19:2114-30 |
| Poremba, Amy; Mishkin, Mortimer (2007) Exploring the extent and function of higher-order auditory cortex in rhesus monkeys. Hear Res 229:14-23 |
| Fritz, Jonathan; Mishkin, Mortimer; Saunders, Richard C (2005) In search of an auditory engram. Proc Natl Acad Sci U S A 102:9359-64 |
| Poremba, Amy; Saunders, Richard C; Crane, Alison M et al. (2003) Functional mapping of the primate auditory system. Science 299:568-72 |
| Elman, I; Sokoloff, L; Adler, C M et al. (1999) The effects of pharmacological doses of 2-deoxyglucose on cerebral blood flow in healthy volunteers. Brain Res 815:243-9 |
