Behavioral and neural investigations of behaviorally relevant features of auditory stimuli

Studies of the structure and function of the human and non-human primate auditory system have led to the hypothesis that it is composed of dorsal and ventral processing streams that are respectively dedicated to spatial and non-spatial processing. Prior to neurophysiological probes of auditory processing in rhesus macaques that relied on the use of species-specific vocalizations, the first study of this thesis established that laboratory-bred subjects respond to vocalizations according to referent meaning in the wild. The second study of this thesis investigated the role of the ventrolateral prefrontal cortex (vPFC), an endpoint of the ventral processing stream, in vocalization processing. This study found that neurons in this location responded to transitions between vocalizations that represent different referent categories, but were insensitive to transitions within a referent category. A third study sought to clarify the conditions necessary for neurons in the lateral intraparietal area (area LIP), a component of the dorsal processing stream, to code the spatial location of an auditory stimulus. The results of this experiment found that neural responses to auditory stimuli are attenuated by the concurrent presentation of a task-relevant visual stimulus. To evaluate the degree to which spatial and non-spatial processing was segregated within the dorsal and ventral streams, a third set of studies analyzed neural responses in vPFC and area LIP to two acoustically separate classes of auditory stimuli presented from distinct spatial locations. The results of this experiments indicated that a significant proportion of neurons at both of these locations coded both spatial and non-spatial features of auditory stimuli.