Kajikawa Lab

The goal of the Auditory Neurophysiology Laboratory (ANL) is to understand the neural mechanisms of sound perception. In primates including humans, auditory cortex is composed of areas grouped in regions at 3+ levels in a hierarchical order: core-belt-parabelt. Each hierarchical level is subdivided into multiple areas. Auditory information processing proceeds through levels and through areas within every level. Information in the belt and parabelt regions diverges into parietal (dorsal) and temporal lobe (ventral), as well as different regions of prefrontal cortex. Growing evidence indicates that the representation of auditory information becomes more complex and abstract as the processing advances. Several psychiatric disorders (e.g. autism) entail communication problems that implicate superior temporal gyrus (STG) or higher level of auditory cortex. Understanding of the basic properties of STG (parabelt areas in the case of monkeys) is essential for understanding these, as well as more basic sensory impairments. 

The ANL focuses on the properties of the parabelt (PB) region on the superior temporal gyrus (STG) in nonhuman primates (NHP) for two reasons. First, PB is fairly well defined anatomically in NHPs (e.g. it divides into caudal and rostral areas, CPB and RPB, respectively). Because detailed anatomical studies (architecture, intrinsic connectivity) have not been conducted in humans, characterization of the PB region in NHPs will help to better define the human PB. Second, while human STG has been implicated in various functions particularly related to perception of communication signals like speech, the physiological properties of the PB in other primate species have not been systematically studied. Thus, the detailed auditory physiology of the macaque PB holds some of the key information missing in our understanding of the organization and functioning of the primate auditory cortex. Our BROAD OBJECTIVE is to characterize the physiological properties, functions, and organization of the PB areas in primates. As PB areas are widely regarded as task-sensitive, we record PB activity only in subjects performing sensory tasks that entail active discrimination of the test stimuli.

Ongoing Projects

1) Systematic description of acoustic preferences (e.g. spectral and temporal tuning) of PB neurons through examination of their responsiveness to a battery of auditory stimuli.

2) Characterization of communication signal processing in PB. We examine neural responses to conspecific vocalization while manipulating their sensory modality or spectral/temporal domains and relate these responses to behavioral performance.

3) Investigation of the network architecture of PB by exploring the connection patterns of PB anatomically and neurophysiologically.