Brian E. Russ

Selectivity for the Spatial and Nonspatial Attributes of Auditory Stimuli in the Ventrolateral Prefrontal Cortex

Spatial and nonspatial auditory processing is hypothesized to occur in parallel dorsal and ventral pathways, respectively. In this study, we tested the spatial and nonspatial sensitivity of auditory neurons in the ventrolateral prefrontal cortex (vPFC), a cortical area in the hypothetical nonspatial pathway. We found that vPFC neurons were modulated significantly by both the spatial and nonspatial attributes of an auditory stimulus. When comparing these responses with those in anterolateral belt region of the auditory cortex, which is hypothesized to be specialized for processing the nonspatial attributes of auditory stimuli, we found that the nonspatial sensitivity of vPFC neurons was poorer, whereas the spatial selectivity was better than anterolateral neurons. Also, the spatial and nonspatial sensitivity of vPFC neurons was comparable with that seen in the lateral intraparietal area, a cortical area that is a part of the dorsal pathway. These data suggest that substantial spatial and nonspatial processing occurs in both the dorsal and ventral pathways.

Spontaneous processing of abstract categorical information in the ventrolateral prefrontal cortex

In various aspects of linguistic analysis and human cognition, some forms of observed variation are ignored in the service of handling more abstract categories. In the absence of training, rhesus discriminate between different types of vocalizations based on the information conveyed as opposed to their acoustic morphologies. We hypothesized that neurons in the ventrolateral prefrontal cortex (vPFC), an area involved in auditory-object processing, might be involved in this spontaneous categorization. To test this hypothesis, we recorded vPFC activity while rhesus listened to vocalizations conveying information about food and non-food events. Results showed between, but not within category discrimination. That is, vPFC neurons discriminated between vocalizations associated with food versus non-food events but not within the class of food calls associated with differences in quality. These results indicate that the vPFC plays a significant role in spontaneously processing abstract categorical information.

Neural and behavioral correlates of auditory categorization

Goal-directed behavior is the essence of adaptation because it allows humans and other animals to respond dynamically to different environmental scenarios. Goal-directed behavior can be characterized as the formation of dynamic links between stimuli and actions. One important attribute of goal-directed behavior is that linkages can be formed based on how a stimulus is categorized. That is, links are formed based on the membership of a stimulus in a particular functional category. In this review, we review categorization with an emphasis on auditory categorization. We focus on the role of categorization in language and non-human vocalizations. We present behavioral data indicating that non-human primates categorize and respond to vocalizations based on differences in their putative meaning and not differences in their acoustics. Finally, we present evidence suggesting that the ventrolateral prefrontal cortex plays an important role in processing auditory objects and has a specific role in the representation of auditory categories.

Auditory processing in the posterior parietal cortex.

Goal-directed behavior can be characterized as a dynamic link between a sensory stimulus and a motor act. Neural correlates of many of the intermediate events of goal-directed behavior are found in the posterior parietal cortex. Although the parietal cortexs role in guiding visual behaviors has received considerable attention, relatively little is known about its role in mediating auditory behaviors. Here, the authors review recent studies that have focused on how neurons in the lateral intraparietal area (area LIP) differentially process auditory and visual stimuli. These studies suggest that area LIP contains a modality-dependent representation that is highly dependent on behavioral context.

TMS affects moral judgment, showing the role of DLPFC and TPJ in cognitive and emotional processing

Decision-making involves a complex interplay of emotional responses and reasoning processes. In this study, we use TMS to explore the neurobiological substrates of moral decisions in humans. To examining the effects of TMS on the outcome of a moral-decision, we compare the decision outcome of moral-personal and moral-impersonal dilemmas to each other and examine the differential effects of applying TMS over the right DLPFC or right TPJ. In this comparison, we find that the TMS-induced disruption of the DLPFC during the decision process, affects the outcome of the moral-personal judgment, while TMS-induced disruption of TPJ affects only moral-impersonal conditions. In other words, we find a double-dissociation between DLPFC and TPJ in the outcome of a moral decision. Furthermore, we find that TMS-induced disruption of the DLPFC during non-moral, moral-impersonal, and moral-personal decisions lead to lower ratings of regret about the decision. Our results are in line with the dual-process theory and suggest a role for both the emotional response and cognitive reasoning process in moral judgment. Both the emotional and cognitive processes were shown to be involved in the decision outcome.

Single-Unit Activity during Natural Vision: Diversity, Consistency, and Spatial Sensitivity among AF Face Patch Neurons

Several visual areas within the STS of the macaque brain respond strongly to faces and other biological stimuli. Determining the principles that govern neural responses in this region has proven challenging, due in part to the inherently complex stimulus domain of dynamic biological stimuli that are not captured by an easily parameterized stimulus set. Here we investigated neural responses in one fMRI-defined face patch in the anterior fundus (AF) of the STS while macaques freely view complex videos rich with natural social content. Longitudinal single-unit recordings allowed for the accumulation of each neurons responses to repeated video presentations across sessions. We found that individual neurons, while diverse in their response patterns, were consistently and deterministically driven by the video content. We used principal component analysis to compute a family of eigenneurons, which summarized 24% of the shared population activity in the first two components. We found that the most prominent component of AF activity reflected an interaction between visible body region and scene layout. Close-up shots of faces elicited the strongest neural responses, whereas far away shots of faces or close-up shots of hindquarters elicited weak or inhibitory responses. Sensitivity to the apparent proximity of faces was also observed in gamma band local field potential. This category-selective sensitivity to spatial scale, together with the known exchange of anatomical projections of this area with regions involved in visuospatial analysis, suggests that the AF face patch may be specialized in aspects of face perception that pertain to the layout of a social scene.

Responses of neurons in the lateral intraparietal area to central visual cues.

Goal-directed behavior is characterized by flexible stimulus-action mappings. The lateral intraparietal area (area LIP) contains a representation of extra-personal space that is used to guide goal-directed behavior. To examine further how area LIP contributes to these flexible stimulus-action mappings, we recorded LIP activity while rhesus monkeys participated in two different cueing tasks. In the first task, the color of a central light indicated the location of a monkey’s saccadic endpoint in the absence of any other visual stimuli. In the second task, the color of a central light indicated which of two visual targets was the saccadic goal. In both tasks, LIP activity was modulated by these non-spatial cues. These observations further suggest a role for area LIP in mediating endogenous associations that link stimuli with actions.

Human Neurophysiology: Sampling the Perceptual World

As we move our gaze through a complex scene, the retinal image is constantly shifted and overwritten. A new study using human intracranial recordings offers a fresh perspective on how the brain creates a sense of perceptual continuity through natural visual behavior.

Chapter 11.3 - Auditory categories in the nonhuman primate

Abstract Communication is one of the fundamental components of both human and nonhuman animal behavior. Whereas the benefits of language in human evolution are obvious, other communication systems have also evolved to convey information that is critical for survival. This chapter focuses on auditory communication signals, specifically species-specific vocalizations and the underlying neural processes that may support their use in guiding goal-directed behavior. We first highlight the fundamental role that species-specific vocalizations play in the socioecology of several species of nonhuman primates, with a focus on rhesus monkeys (Macaca mulatta). Finally, we discuss the role that the ventrolateral prefrontal cortex may play in the categorization of species-specific vocalizations.