(Scientific Session) Blast from the Past: Auditory Conditioning as Traumatic Brain Injury Prophylaxis

Background and/or Objectives: Many military personnel develop blast-induced traumatic brain injury and secondary symptoms of tinnitus and depression. The current experiment hypothesizes that auditory conditioning is effective as a prophylactic treatment to prevent blast-induced tinnitus and depression.

Design: Double blinded, randomized, controlled study

Setting: Institutional Animal Vivarium

Participants: Mice: 28 control, 32 blast control, 18 biofeedback therapy

Interventions: Treatment group received auditory conditioning (20 ms Broad-Band Noise at 90 dB repeated ever 50 ms for 1 hour) daily 5 days a week for 10 weeks prior to blast-pressure wave exposure.

Main Outcome Measures: Percent of animals that developed tinnitus or depression after blast pressure wave exposure. Tinnitus was measured via acoustic startle testing. Depression was measured with forced swim tests.

Results: No significant difference was observed between control and treatment animals in the development of tinnitus. However, a significant decrease was observed in signs of depression in the treatment group (p < 0.0001).

Conclusions: Auditory conditioning treatment significantly decreased the incidence of depression in mice with blast exposure but had no influence on the development of tinnitus. This may be because the blast-pressure wave induction of tinnitus is caused by physical damage, while depression symptoms are caused by an imbalance of excitation in limbic brain circuits. Our experiments show that auditory conditioning may be a viable method of prophylaxis to decrease the types and severity of some symptoms associated with blast-induced traumatic brain injury.