Cortical responses to promontorial stimulation in postlingual deafness

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Neuroimaging

Background:

• Electrical stimulation via transtympanic electrodes enables auditory tasks in hearing and deaf individuals.
• Previous studies identified the right posterior temporal lobe's role in duration discrimination for normally hearing subjects.

Purpose of the Study:

• To investigate if postlingually deaf individuals recruit the right posterior temporal lobe for temporal discrimination.
• To test the hypothesis that this brain region is crucial for subtle temporal discriminations in deafened ears.

Main Methods:

• Positron emission tomography (PET) with 15-O-labelled water uptake was used to record cerebral activity.
• Fourteen postlingually deaf cochlear implant candidates underwent electrical stimulation in the ear designated for implantation.
• Subjects performed gap detection and temporal difference limen (TDL) tasks.

Main Results:

• All subjects showed bilateral activity near the primary auditory cortex upon stimulation.
• Good TDL performers exhibited right-lateralized fronto-temporal and left-lateralized temporal activity for TDL and gap detection, respectively.
• Poor performers (<200 ms TDL) showed only frontal and occipital activation, lacking temporal lobe engagement.

Conclusions:

• The right posterior temporal region's involvement is critical for accurate duration discrimination.
• This neurophysiological ability can be evaluated pre-operatively in cochlear implant candidates.