2. Mechanisms of Binaural Suppression in Rat Auditory Cortex Carolyn Cahill College of Wooster SPUR 2009 Mentor: Michael Kyweriga Wehr Lab University of Oregon Institute of Neuroscience Department of Psychology

3. What is Binaural Suppression? Sound input from both ears Binaural cues are important for sound localization High frequencies use interaural sound level differences Neurons respond well to certain binaural combinations

4. Auditory Pathway Cortex Midbrain Brainstem Outer, middle, and inner ear

5. Binaural Suppression Sound entering one ear suppresses responses to sound entering other ear Right EarLeft Ear Both Ears Right Ear

6. Synaptic Inhibition Suppression is thought to be caused by synaptic inhibition Application of Gabazine Pre Post Pre Post

7. What does binaural suppression look like? Left Ear Right Ear Both Ears

8. Research question: Where is binaural suppression computed? ? ? 1. Cortex ? 2. Brainstem ? 3. Both ?

9. How to test the hypothesis Apply gabazine to cortex 3 things might happen: same – Suppression will remain the same gone – Suppression will be gone partially gone – Suppression will be partially gone http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=107895 Both Ears

10. How to test the hypothesis 1. Find primary auditory cortex in the rat 2. Find a binaural suppression site 3. Apply gabazine to cortex and record neural responses

11. Results Before GabazineAfter Gabazine Rat A Rat B

12. Results Before GabazineAfter Gabazine 100 uM Gabazine 5 uM Gabazine

13. Summary Relief of suppression seen in 2 of 4 rats More data from multiunit recording Start single cell recording Future Directions

14. Acknowledgements Michael Kyweriga (mentor) Dr. Mike Wehr (PI) SPUR Dr. Peter O’Day Ms. Chelsie Fish Funding: NSF REU, University of Oregon/SPUR Labmates: Xiang Gao Katelyn DufourNathan MontgomeryMaddie Norman