Neurons and neural circuits in the auditory system

The general goal of our lab is to understand how information about sound is processed by the brain. The inferior colliculus (IC) is at the center of the auditory pathway. All information about sound must pass through the IC as it travels from the ear to the cerebral cortex. We are part of an international effort to unlock the secrets of this part of the brain. 

Tinnitus and hearing loss

Age-related hearing loss and other forms of hearing loss represent the fourth most common chronic illness in the world (1.2 billion people in 2015). Hearing loss is not just a disease of the ear. The central nervous system reacts to changes in the ear, and this leads to plastic changes in the central auditory system. Understanding these plastic changes is a key to providing a new therapy for hearing loss and tinnitus.

To learn about auditory function, we perform experiments that combine morphology, electrophysiology, and sometimes molecular biology. Most often, we study neurons in vivo so that we can use sound to identify their function. Experimental methods include recording responses to sound from both single neurons and entire brainstem. Our lab has a history of making important discoveries about the structure and function of the auditory system and inferior colliculus in the midbrain including the identification of neuronal cell types, micro-circuits, long pathways and synaptic function.

Our current projects focus on understanding tinnitus, the sensation of ringing in the ears when there is no sound. In other words, you hear a phantom sound. Recently, have discovered neurons in the auditory system that can fire for minutes after the offset of a long duration sound. They have a long-lasting, sound-evoked afterdischarge, so we call them LSA neurons. This is an unusual form of plasticity that may be related to tinnitus. We have received substantial funding from the Department of Defense, Congressionally Directed Medical Research Program to develop an electrophysiological test for tinnitus. We will use both drug-induced and noise-induced animal (mouse) models of tinnitus. Animals will be tested behaviorally with several methods to establish which mice have tinnitus, then they will be studied electrophysiologically. We will make deep brain 32-channel recordings in the auditory midbrain to learn how LSA neurons are changed with tinnitus. With this knowledge, we will develop an electrophysiological test using evoked potential recordings that will detect LSA from surface electrodes on the scalp in mice with and without tinnitus. Finally, we will use our electrophysiological tests on human subjects and patient from the UConn Health Surgery/Otolaryngology clinic.

Current neuroscience projects that could turn into a dissertation.

  1. We hypothesize that the neurons in the auditory midbrain with long-lasting sound-evoked afterdischarges (LSA) supply the signal to the brain that is interpreted as a phantom sound (tinnitus). Use deep brain recordings from 32-channel electrodes to discover the relationship of LSA neurons to tinnitus in both sodium salicylate and noise-induced tinnitus models.
  2. Investigate which behavioral tests to detect tinnitus in animals is the most reliable. We hypothesize that the gap-induced inhibition of acoustic startle is less reliable than a shock avoidance discrimination task.
  3. Develop a non-invasive electrophysiological test for tinnitus in human patients. Use changes in afterdischarge response measured with non-invasive techniques to diagnose the presence or absence of tinnitus in mice and humans. We will use scalp recordings of EEG activity, auditory brainstem and amplitude modulation responses to develop our tests in mice and then apply any promising method to a human patient population.