Harold Burton Research Abstract
Our research explores possible reorganization in human cerebral cortex in the presence of sensory aberrations. Combined in these studies are functional brain imaging and behavioral assessments in individuals with some sensory deficit compared to age matched normal controls. Prior studies with people blind from birth showed reorganization in their visual cortex that included extensive cross-modal activation to auditory and tactile stimulation and during memory and language tasks. In the blind we further discovered increased resting state functional connectivity between visual cortex and cognitive control regions in frontal and parietal cortex that possibly reflect behavioral enhancement of working memory and attention in adaption to blindness. Technically comparable studies investigated reorganized cortex in two other patient groups. Individuals with bothersome tinnitus who showed deficient attention behavior also had altered functional connectivity between cortical networks for vision and attention. Patients with cerebral palsy who showed deficits in tactile and kinesthesia abilities also had reduced cortical responses to tactile stimulation of the fingertips and disrupted functional connectivity maps throughout somatosensory cortex.
Ongoing research in individuals with adult onset unilateral deafness shows auditory cortex reorganization that involves accentuated activation to acoustic stimulation in the cortical hemisphere ipsilateral to the intact ear. These cortical changes correlate with observed deficits in sound localization and speech recognition in the presence of noise. A current study examines whether underlying a speech recognition deficit is augmented activity in frontal cortex regions involved in semantic processing when attempting to understand degraded speech heard only with one intact ear.
Another project evaluates a novel eight channel sieve electrode for peripheral nerve interface to stimulate sensory axons electrically in a forearm nerve of behaving non-human primates. A goal is to show that the monkey interprets as behaviorally relevant selective stimulation to specific regions within a peripheral nerve. We train monkeys on a multiple-alternative forced choice task where each stimulated nerve sector corresponds to a choice target. Another goal is to record from primate somatosensory cortex to compare the effect of chronic peripheral nerve stimulation on responses to electrical vs. tactile stimulation, to assess response stability (variance) to repeated stimulation of a nerve sector, and to examine somatotopography for possible plasticity in the map in the stimulated nerve region. A long-term translational objective of investigating the capabilities of the sieve electrode is for control of a prosthetic limb with embedded haptic sensors the activation of which concurrently stimulates sensory axons in a stump nerve of an amputee with an implanted electrode.