Hearing and the Brain:

David K. Ryugo, Ph.D.Curran Foundation Chair of NeuroscienceGarvan InstituteDarlinghurst 2089, NSWAustralia

Conjoint ProfessorSchool of Medical SciencesUniversity of New South Wales

Professor EmeritusJohns Hopkins UniversityBaltimore MD, 21205USA

Making Sense of Sound, Hearing Loss,and Brain Plasticity

Supported by grants from the NIH, NHMRC, GP&PW Memorial Foundation, and NSW Office for Science and Medical Research

All sounds are made by combinations of frequencies

Sound has Energy or Loudness

OSHA permissible levels: 85 dB for 8 hrs; 100 dB for 2 hrs; 110 dB for 0.5 hrs

Sound has important timing features(onset, offset, duration, change)

dot dot dot dash dash dash dot dot dot

American English Australian Englishah-seet-l-koh-leen ah-suh-teel-koh-leen

IHCs

OHCs

Recovery of hearing sensitivity in quiet after exposure to damaging noise

Acoustic overexposure: the traumatic stimulus was 100 dB SPL for 2 hours.

Invisible damage from noise exposures

Kujawa and Liberman, 2009

With moderate hearing loss, thresholds in quiet are normal.

The problem is when there is noise in the background.

Why is this?

Modified from Spoendlin, 1973

0.1 mm

Time (seconds)

“Testing . . . one, two, three”

Now What?Best remedy: Protect your hearing

Future Research1. Develop methods to block cell death pathways2. Improve signal-noise ratio in amplification methods involving hearing aids and cochlear implants3. Design effective transgenic or stem cell approaches4. Training and psychological strategies to improve cognitive skills.