Research

Rapid Task-Related Plasticity of spectrotemporal receptive fields in primary auditory cortex
The view of the cortex as a static processor of sensory information has been giving way to the notion of a malleable system that slowly adapts to a changing environment during development, injury, or stimulation. This view is now evolving again in light of recent studies in primates and ferrets that reveal nearly instantaneous changes that occur in the cortex when animals are engaged in various tasks. For instance, we have recently demonstrated that in an auditory detection task, in which a ferret is trained to detect the presence of a target tone against a background of broadband noise, STRFs undergo rapid facilitation that is often specific to the target frequency, and can be short-lived or alternatively persist for many hours, leading to long-lasting receptive field changes, a form of sensory memory. Furthermore, this rapid plasticity is absent or weak in naive animals, or in non-behaving and poorly behaving trained animals. Recent results also demonstrate that STRF changes are dependent on the exact nature of the behavioral task and target stimuli involved, but consistent with the goal of optimizing the animal performance under different conditions. The insights provided by these findings, coupled with the powerful tools developed for on-line measurements of the STRFs, provide a strong impetus for pursuing more elaborate experimental designs to explore the underlying mechanisms, computational implications, and optimality principles that govern cortical plasticity.

Rapid Task-Related Plasticity of spectrotemporal receptive fields in primary auditory cortex
The view of the cortex as a static processor of sensory information has been giving way to the notion of a malleable system that slowly adapts to a changing environment during development, injury, or stimulation. This view is now evolving again in light of recent studies in primates and ferrets that reveal nearly instantaneous changes that occur in the cortex when animals are engaged in various tasks. For instance, we have recently demonstrated that in an auditory detection task, in which a ferret is trained to detect the presence of a target tone against a background of broadband noise, STRFs undergo rapid facilitation that is often specific to the target frequency, and can be short-lived or alternatively persist for many hours, leading to long-lasting receptive field changes, a form of sensory memory. Furthermore, this rapid plasticity is absent or weak in naive animals, or in non-behaving and poorly behaving trained animals. Recent results also demonstrate that STRF changes are dependent on the exact nature of the behavioral task and target stimuli involved, but consistent with the goal of optimizing the animal performance under different conditions. The insights provided by these findings, coupled with the powerful tools developed for on-line measurements of the STRFs, provide a strong impetus for pursuing more elaborate experimental designs to explore the underlying mechanisms, computational implications, and optimality principles that govern cortical plasticity.

Physiological and Computational Basis of Auditory Streaming in Auditory Cortex
Humans can effortlessly perceive and navigate their acoustic surroundings despite the multiplicity of simultaneous sound sources, and often in noisy and reverberant environments. A critical perceptual phenomenon underlying these remarkable abilities is auditory streaming - the ability to parse different sources into segregated “streams”, and hence to attend to one or another. This innate capability utilizes a wide range of acoustic cues and perceptual attributes (location, pitch, loudness, timbre), and is closely related to other complex phenomena such as the “continuity illusion”. The physiological underpinnings of auditory streaming remain barely explored, hampered by the lack of animal models, by the difficulties of reliably interpreting human imaging data in these tasks, and by the absence of comprehensive computational models of this phenomenon to facilitate the experimental work. Ongoing research in our laboratory aims to integrate these three different strands (computational models, physiology, and psychoacoustics) into a coherent study of auditory streaming. Specifically, we have been developing and testing computational models of cortical function suitable for analysis and validation of data from psychoacoustic data on streaming. Behavioral experiments are also underway to determine whether our animal model (ferret) exhibits reactions consistent with perception of auditory streams. These behavioral paradigms have been adapted for use in pilot physiological experiments to record cortical responses to the same acoustic stimuli.