Monkeys were trained on an auditory version of delayed matching-to- sample with randomly varying delays of 2-50 sec and then retested after being given different types of bilateral temporal lobe lesions. Monkeys that received complete medial temporal removals were severely impaired even at the shortest delays, whereas those given lesions limited to the rhinal (i.e. perirhinal/entorhinal) cortex, which are known to produce severe impairment in both visual and tactile recognition, were unaffected even at the longest delays. The finding points to an unexpected difference in the substrates for stimulus memory in the different exteroceptive modalities; a search for these substrates in audition is currently underway. Selective responses of neurons in the auditory lateral belt areas, which receive input from the primary auditory areas, seem to be due mainly to temporal and spectral integration across frequencies. To examine this notion further, we tested lateral-belt neurons with a standard set of monkey vocalizations and their components and found some neurons that display temporal combination sensitivity (in which the response to the whole monkey call is greater than the sum of the responses to individual components), others that show temporal suppression (in which the response to one component of the call is reduced when it is preceded or followed by another component of the call), and still others that show both types of nonlinear interaction. The proportion of neurons showing these complex selectivities is greater in the lateral belt than in the primary auditory areas, supporting the existence of an auditory processing hierarchy within the superior temporal gyrus. Extension of these studies to a newly described medial-belt area revealed neurons with properties comparable to those found in neurons of the lateral belt. Although much of the cerebral tissue involved in auditory processing in the monkey has been identified, its full extent had not previously been delineated. This was achieved by applying the [14C]2- deoxyglucose (2-DG) method in order to compare glucose utilization during auditory stimulation in intact hemispheres with that of hemispheres deafferented from auditory input. The results revealed that the cortical auditory processing stream includes the entire dorsal and lateral extent of the superior temporal gyrus (STG) as far rostrally as the dorsal part of the temporal pole. They also revealed points of contact with other cortical and subcortical systems, such as the lateral nucleus of the amygdala in the limbic system. Interestingly, the pattern of 2-DG uptake in the anterior third of the STG resembled columns, or bands, of activation suggestive of higher-order processing. These activity maps will help guide our other endeavors including the a - monkeys, auditory recognition, monkey vocalizations, rhinal cortex, auditory cortex, neuronal responses, glucose utilization
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