2020-22 HMRF: Calcium wide-field imaging as a tool for evaluating cochlear implant stimulation strategies in the auditory cortex

Grant title: Calcium wide-field imaging as a tool for evaluating cochlear implant stimulation strategies in the auditory cortex.

Principal (co-)investigators: Jan SchnuppNicole Rosskothen-Kuhl (Freiburg)

Grant scheme: Health and Medical Research Fund project Nr 07181406 (9211221)

Funding amount: HK$ 1,191,638

Grant duration: 1-9-2020 - 31-12-2022


Studies of neural responses to cochlear implant (CI) stimulation can inform better treatment strategies, but large electrical
artifacts created by CIs hamper electrophysiological approaches. We propose to use calcium (Ca++) imaging of auditory
cortex (AC) to evaluate different cochlear implant strategies.
1) Discriminability of cortical response patterns will depend on CI pulse rates.
2) Interaural timing of binaural CI pulses can give rise to binaural unmasking of a modulated envelope signal.
Design and Subjects:
Anesthetised Wistar rats will be implanted with CIs, and cortical responses to multi-electrode stimulus patterns delivered to
the implants will be recorded using activity dependent Ca++ indicator dye Oregon Green Bapta (OGB).
Outcome measures and data analysis:
Movie sequences of cortical responses will be acquired at 100 frames/s using marcoscope imaging of OGB fluorescence.
The movies will be processed using established dimensionality reduction and denoising techniques (SVD and DSS), and the
discriminability of neural response time-series obtained will be quantified using standard classifier algorithms. This will
allow us to measure how the reliability of cortical evoked responses to neuroprosthetic stimuli depends on the tested
stimulation parameters.
Expected Results:
1) the discriminability of CI stimulus patterns will depend on electrode pulse rates, with maximal mutual information
between prosthetic stimulus and cortical response expected at pulse rates near 300 Hz / s.
2) Signals in the presence of background noise will be more detectable if the cochlear channel carrying the signal has a
different ITD than the noise.