Tradeoff Between Spatial and Temporal Resolution

Study Overview
=================
Brief Summary
-----------------
In this study, investigators will examine how temporal rate processing might be affected when the width of neural excitation narrows. The manipulation of neural excitation width will be achieved for example by changing electrode configurations or stimulating single versus multiple electrodes simultaneously. Investigators will then measure if the extent to which rate processing is affected by spatially restricted stimulation can predict a subject's overall speech recognition and predict also whether the subject is likely to benefit from a focused electrode configuration. Lastly, investigators will introduce and test a novel current focusing strategy where current focusing is applied in a channel specific manner and quantify if this intervention improves speech recognition. The primary endpoint of the study is speech recognition, and the secondary endpoint is psychophysical sensitivity to stimulation rate change.

Official Title
-----------------
Tradeoff Between Spatial Resolution of Neural Excitation and Temporal Rate Processing

Conditions
-----------------
Deafness

Intervention / Treatment
-----------------
* Behavioral: Electrode selection/electrode configuration


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Native speakers of English Cochlear Nucleus cochlear implant users or Advanced Bionics users Postlingually deafened Has had device experience for at least one year Can be child or adult at the time of enrollment Exclusion Criteria: None

Ages Eligible for Study
-----------------
Minimum Age: 15 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Cochlear implant users with Nucleus and AB devices<br>Temporal processing acuity will be compared using electrodes or electrode configurations that create broad versus sharp spatial excitation. Speech recognition will be compared in the same group of subjects using electrode-dependent focused versus monopolar stimulation. | Behavioral: Electrode selection/electrode configuration<br>* Electrodes will be chosen based on their spatial tuning curves. Focused stimulation will be applied to electrodes with good temporal processing acuity.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Sensitivity to stimulation rate change at threshold | Subjects' psychophysical detection thresholds will be measured as a function of the rate of stimulation delivered to selected electrodes and selected electrode configuration | starting 6 months post award notice and will take up to 4 years to complete | 
| Discrimination of stimulation rate | subjects' ability to discriminate stimulation rates will be measured as a function of base stimulation rates at selected electrodes and selected electrode configuration. | starting 6 months post award notice and will take up to 4 years to complete | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Speech recognition | Speech recognition in quiet and in noise will be measured under three conditions: 1. the traditional monopolar electrode configuration; 2. using current focusing on electrodes that show good sensitivity to rate change; 3. using current focusing on all electrodes. | starting 6 months post award notice and will take up to 4 years to complete |