[CTN] CTN seminar: Dr. Ian Bruce (McMaster University), Sept. 10, 3.30pm in PAS 2464

[Matthijs van der Meer]

Dear all,

Please join us for the first CTN seminar of the 2013-2014 series, next
Tuesday, Sept 10: Dr. Ian Bruce, from McMaster University. Title and
abstract follow below.

Time and place are the usual, 3.30pm on Tuesday in PAS 2464.

If you would like to meet with Dr. Bruce, and/or come to dinner, please
let me know.

As always, feel free to forward this invitation to interested students
and colleagues. The CTN webpage (ctn.uwaterloo.ca) has the link to sign
up to the mailing list. Students are encouraged to also subscribe to the
ctn-student list
(http://ctnsrv.uwaterloo.ca/mailman/listinfo/ctn-students) for lunch and
other announcements.

Hope to see you there,

- Matt


When things go bad with cortical plasticity: modeling the central
effects of hearing loss

Ian C. Bruce, Ph.D., P.Eng.
McMaster University

http://www.ece.mcmaster.ca/~ibruce/

The mammalian auditory periphery performs a highly-sophisticated
nonlinear, time-varying, context-dependent time-frequency analysis of
acoustic signals. On top of this, plasticity in the primary auditory
cortex allows its neurons to develop a multiplicity of receptive fields
that it can switch between, depending on the acoustic environment or
perceptual task the listener is engaged in. When damage or disease in
the auditory sensory epithelium gives rise to “hearing loss”, the
resulting distortions to the neural representation of acoustic signals
cause substantial difficulty in many listening situations, even with the
use of hearing aids. Further compounding these peripheral impairments
are subsequent changes in the central auditory system that give rise to
perceptual problems such as loudness recruitment (an abnormally-steep
growth of loudness with acoustic intensity) and tinnitus (a phantom
auditory percept in the absence of any external acoustic stimulus).

In this talk, I will describe a physiologically-accurate model of the
mammalian auditory periphery, including the effects of hearing loss,
that has been developed in my lab, as well as a model of primary
auditory cortex developed with colleagues at McMaster. Using the
combined models, we have investigated how impaired peripheral
representations may induce maladaptive plastic changes in the neural
circuits of the auditory cortex. The models are able to replicate a wide
range of data from animal neurophysiological experiments. Simulation
results indicate that homeostatic plasticity (HSP) and
spike-timing-dependent plasticity (STDP) may each contribute to
different aspects of the aberrant response properties of cortical
neurons following peripheral hearing loss. HSP appears to generate
abnormally-high levels of spontaneous activity and synchrony, which are
likely neural correlates of tinnitus, while STDP can lead to cortical
frequency map reorganization if the hearing loss is severe enough.

[This work was funded by NSERC and CIHR.]