Projects of the Amelia Peabody Neural Plasticity Unit
Ongoing work in our group is directed towards three broad questions:
1) How does early postnatal experience influence functional circuit organization in the developing auditory cortex?
2) How do the intricate networks of descending feedback connections allow the cortex to modulate auditory stimulus representations at lower levels of the auditory pathway?
3) How can we design adult auditory training protocols that will bring about effective and long-lasting improvements in human perceptual acuity?
At the intersection of these three themes lies the emerging field of “applied plasticity research”, which holds that neural plasticity can be engaged and directed towards bringing about gain of function in individuals with a history of degraded sensory experience.
Theme I: Experience-Dependent Influences on Auditory Cortex Development
These studies rely heavily upon single unit recordings and tonotopic map reconstruction in the inferior colliculus, auditory thalamus and auditory cortex of animals that have been reared in altered acoustic environments or with a reversible conductive hearing loss. The goals are to understand 1) how combinatorial selectivity across spectral, temporal and binaural sound domains is expressed following normal or developmentally altered experience; 2) how these "critical periods" for experience-dependent influences are organized across development and between different levels of the central auditory hierarchy.
Binaural interation matrices in the primary auditory cortex (AI) and the central nucleus of the inferior colliculus (ICc) from a rat with normal experience (left column) are compared againt binaural interactions measured bilaterally in a rat that underwent reversible monaural deprivation
Theme II: Top-Down Control via the Corticofugal Pathways
In these studies, we manipulate genes (via transgenic models or gene electroporation) and cognitive features such as attention and learning to understand how the massive and precise network of descending corticofugal connections modify earlier stages of auditory processing.
Strucutural organization of feedforward (left) and feedback (middle) connections between the
medial geniculate body and AI are compared again the functional organization in wild type mice.
Theme III: Remediating Adult Auditory Perceptual Deficits through Sensory Training
The adult auditory cortex retains the capacity for substantial functional reorganization provided that the experienced sound explicitly and reliably predicts behaviorally meaningful consequences (i.e. reward or punishment). It is generally accepted that this plasticity underlies a robust form of learning characterized by a progressive improvement in auditory perceptual skills with extended practice. Future studies will develop interactive human training environments for studies in normal and clinical populations