Communication is one of the fundamental components of human and non-human animal behavior. The ventrolateral prefrontal cortex (vPFC) in rhesus monkeys has recently been identified as a cortical area that plays an important role in auditory-object and vocalization processing. This grant proposal tests the response properties of vPFC neurons in order to determine its role in auditory-object processing.
In Aim #1, we construct the spectrotemporal receptive field (STRF) of vPFC neurons to determine how the vPFC codes the features of ensembles of vocalizations and ripple noise (an artificial stimulus with properties similar to vocalizations). We test two alternative hypotheses. First, if the vPFC is involved in low-level feature extraction, as measured by our STRF model, we hypothesize that (1) a significant proportion of vPFC neurons have significant STRFs and that (2) the STRFs are accurate predictors of a neuron's response to an auditory stimulus. The second, alternative hypothesis is that if the vPFC is involved in computations related to higher-order mechanisms beyond feature extraction, such as auditory-object processing, we hypothesize that a significant proportion of vPFC neurons do not have significant or predictive STRFs.
In Aim #2, we test the selectivity of vPFC neurons for the spatial and non-spatial attributes of an auditory stimulus. Since the vPFC is thought to be part of a pathway involved in auditory-object processing, we hypothesize that vPFC neurons should be modulated preferentially by the non-spatial attributes of an auditory stimulus. We hypothesize that the ventrolateral prefrontal cortex are more selective for the non-spatial attributes of an auditory stimulus but only when monkeys attend selectively to these attributes. To test this hypothesis, we compare the selectivity of vPFC neurons to auditory stimuli when monkeys attend to changes in the spatial or non-spatial attributes of an auditory stimulus and (2) do not attend overtly to either of these attributes.
In Aim #3, we test whether vPFC neurons respond to auditory and visual communication signals that convey similar information. We hypothesize that vPFC neurons will respond preferentially to stimuli that transmit complementary information. To test this hypothesis, vPFC activity is obtained while species-specific vocalizations and the visual images of the facial expressions that typically accompany or do not accompany the production of these vocalizations are presented.
