Processing of complex sounds in the auditory cortex

The brain is very adept in processing complex sounds yet when certain conditions such as stroke, depression, schizophrenia, and others occur, language and speech disorders result. This may include auditory hallucinations. It is very important to understand the underlying mechanism of the rain to process complex sounds. Auditory perception and cognition, including processing of communication sounds, is achieved in the cerebral cortex. Continuing neurophysiological studies on anaesthetized cats and monkeys have yielded significant data on the organization of nonprimary auditory cortex. The functional organization of auditory response properties in different auditory cortical areas will be charted. Anatomical connections between different areas will be investigated with neuroanatomical  tracers after physiological mapping.

Neural bases of speech perception in human auditory cortex

The foundation of this study is to understand more about the neural basis of speech perception. Speech perception is readily observed psychologically, yet has not been readily observed neurobiologically. The notions of hierarchical networks, processing streams, and higher-order computational maps have been used successfully in animal research on complex visual and auditory perception. Using high-field fMRI the study will not only determine the location of cortical areas activated by natural and synthetic speech sounds, as opposed to other sounds with similar complexity, but also for the first time reveal detailed organizational principles of higher-order acoustic-phonetic feature maps within human auditory and language cortex. The studies will provide a wealth of new information in the under-researched field of higher auditory pathways in humans, as well as insight into general organizational principles of functional architecture in cortical processing.

Functional imaging of tinnitus-related activity in the auditory cortex of humans and rats

Tinnitus is a condition in which there is ringing in the ears when there is no external sound source present. Tinnitus has been continually studied. The current research proposes that If patients have a selective hearing loss and experience tinnitus, then the tinnitus frequencies should be shifted towards the edge frequencies of the impaired hearing range. In a precise mapping of the tonotopic frequency representation in the auditory cortex of these tinnitus patients, an expansion of the tinnitus frequencies would be expected, which essentially fills in the gap left by the deafferentation around the hearing loss. High-resolution functional imaging of the auditory cortex in tinnitus patients will be conducted using functional MRI (fMRI) to determine tonotopic maps and their local distortions around the region of interest. In the animal model of tinnitus (hearing loss induced by sound overexposure), it is postulated that the activity of neurons within the expected range of tinnitus frequencies should be increased compared to their surround frequencies. High-resolution functional imaging of the auditory cortex in rats with experimentally induced and behaviorally verified tinnitus will be conducted using functional MRI in order to determine tonotopic maps and their local distortions around the region of greatest hearing loss. This is accompanied by electrophysiological single- and multi-unit recording in the target area identified by functional imaging.

Cortical mechanism of auditory-visual integration in the macaques

The purpose of this study is to investigate the neural processing of auditory and visual information and what cortical mechanisms exist to integrate multisensory stimuli into animal's behavior. Auditory-visual perception and cognition, including communication sound processing, is achieved in the cerebral cortex. It has been proposed that one of the major cortical zones involved in the convergences of visual and auditory signals is the anterior bank of the supratemporal sulcus, known as supratemporal polysensory area (STP). The subsets of cells in the STP area have been shown to have either visual or auditory responses but very little is known about their associative properties. The rhesus monkey is the model organism used to examine higher cortical functions. The rhesus needs to be motivated to actively participate in the experiments, not only because attentional and other "non-specific" factors can influence the responses of the neurons in higher cortical areas, but also because some of the neurons in the higher areas are only active when they are fully engaged in a cognitive task and their responses can also be context-dependent in the behavioral task.