Current Projects

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  • New deep brain stimulation (DBS) technologies and strategies for treating hearing disorders, including deafness, tinnitus, and hyperacusis.
elec New DBS array for an ongoing NIH-funded clinical trial to treat deafness and tinnitus: (top) 2-shank auditory midbrain implant (AMI), and (bottom) fast stimulator-processor that is fully implanted into the skull (pulse rates up to 31,500 pps and neural recording capabilities). Devices and stimulation strategies are developed with Cochlear Limited and Hannover Medical School.

Electrical stimulation of the dorsal cortex of the inferior colliculus (ICD) paired with broadband noise stimulation (PAES) induces differential amounts of suppression and facilitation of neural activity (spread) dependent on the timing of the two stimuli. Using the AMI with an electrode site near the Dacron mesh, which allows for stimulation in ICD, in conjunction with auditory stimulation may lead to tinnitus and hyperacusis suppression.

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  • Development of 3D anatomical and functional reconstruction methods for different brain regions.

 

Blueprints for brain box used to section brain: rat brain box

 

  • Functional investigation of corticofugal projections for the development of a cortical stimulator for tinnitus or hyperacusis.

spikecount

Combining auditory cortical stimulation with precisely timed broadband noise stimulation (PN-Stim) induces strong suppression of activity within the auditory midbrain that remains after PN-Stim has stopped. This type of suppressive action is not typically observed with broadband noise stimulation alone or cortical stimulation alone. PN-Stim using noninvasive TMS or direct cortical stimulation may be relevant for suppressing the auditory hyperactivity linked to tinnitus or hyperacusis.

 

  • Development of a new noninvasive neuromodulation approach (Multimodal Synchronization Therapy, mSync) that combines precisely timed activation of multimodal pathways to treat tinnitus and other brain conditions.

msync

 

  • Development and optimization of ultrasound stimulation to modulate brain and peripheral nerve circuits. These findings are compared to electrical and magnetic stimulation effects.

ultrasound

 

  • Mapping the functional organization of somatosensory projections to the auditory system.
msyncresults

Electrical stimulation of different body regions elicits the lowest threshold and/or spread of activation of specific regions within the inferior colliculus, revealing somatotopic trends within the auditory midbrain of guinea pigs. These findings can help guide the development and implementation of mSync (described above) for treating hearing disorders.

 

  • Identification of subprojection lemniscal pathways through the inferior colliculus, thalamus, and auditory cortex.

dual pathways

Schematic of systematic differences in anatomical projections (A) and physiological differences (B, our results in color) indicating that the auditory lemniscal pathway is segregated into two subprojection pathways from the midbrain to the cortex. Our results showed, for the first time, physiological property differences between regions in the ICC consistent with this segregated pathway hypothesis.

 

  • Neural coding across the inferior colliculus in response to simple and natural stimuli.
latency

Neural activity across the whole IC was recorded in response to broadband noise stimulation. Each recording was analyzed for many response properties and trends in coding were determined. One of the response properties showing a trend across the whole IC was first spike latency. Sites in the rostral and lateral regions of the IC have a faster latency than sites in the caudal and medial regions.

Different vocalizations (speech-like stimuli) recorded from guinea pigs that we then played back to them and recorded the neural patterns across the central nucleus of the inferior colliculus. Findings from these types of studies will help guide the development and implementation of stimulation strategies for the AMI (described above).

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  • Incorporating stress relaxation techniques and integrative healing with traditional neuromodulation to enable and strength plasticity.
maze Stress and anxiety have documented effects on the release of neurotransmitters and the ability to induce neural plasticity. We are currently investigating the effects of stress reduction on plasticity induction via mSync. In this study, stress relaxation techniques and integrative healing is performed on guinea pigs, and an elevated plus-maze behavioral test quantifies stress reduction compared to control animals. These results are correlated with chronic awake neural recordings to determine the link between plasticity induction and stress level.

 

  • PET imaging of loudness coding in implant and tinnitus subjects.

 

  • Neural mechanisms underlying central auditory plasticity.

 

  • Neural mechanisms underlying temporal integration within the central auditory system.

 

  • Development of a new laser based hearing aid.