Traditional Strategies Flashcards
Describe SAS
Simultaneous analog sampling
All 8 electrodes are stimulated at once, firing analog waves rather than pulse widths
This is the ONLY bipolar strategy used with AB, all others are monopolar
Strategy is based on M levels; no need to measure T levels
With an enhanced bipolar array, electrode 8 would be disabled with SAS
Describe CIS
Continuous interleave sampling
Sequential stimulation; round robin pattern electrodes 1-8
Must measure T and M levels
Describe MPS
Multiple pulsatile stimulation
Paired strategy, so twice the rate of CIS
Typically have lower M levels because faster rate results in greater perception of loudness
Measure T and M levels, will typically drop by half when you select MPS
How does AB technology preserve the incoming signal in the timing domain?
High stimulation rates allow us to capture both envelope and fine structure information
Helps with prosody and intonation
With HiRes, we are sampling and stimulating at high rates
How does AB technology preserve the incoming signal in the intensity domain?
T-mic allows for natural cues about sound source and localization
AutoSound (dual loop AGC and wide, programmable IDR)
How does AB technology preserve the incoming signal in the frequency domain?
Incoming sound is divided into frequency bands from 250-8000 Hz (8 or 16 bands depending on strategy)
With current steering, the goal is to create more areas of activation within the cochlea for improved pitch perception
Why might you change the ground electrode from case band to ring band (or vice versa)?
If the patient is getting facial twitch, or there are concerns about back telemetry
What is the stochastic response theory?
In the cochlea, there are random firing patterns of neurons coming in and our of refractory. With a traditional cochlear implant, we lose some specificity because we stimulate groups of neurons at a time.
If we can stimulate at rates above 40,000 we can more closely duplicate this random firing.
What is the EDR?
Electric dynamic range; the range between T and M levels. Most strategies are based on M levels, where T is 1/10 of M. By setting T levels automatically, we are maximizing EDR.
What is the IDR?
Input dynamic range. The IDR of a normal hearing individual is approximately 100 dB; AB has the widest IDR in the industry at 80 dB.
The IDR dictates the slope of compression function. There is a kneepoint at T level and at M level. Compression begins above M level, peak clipping at 12 dB above M level.
How does the EDR work in Cochlear software?
Any sounds below T level will not be processed. Cochlear also uses a linear 1:1 slop and peak clips at C level.
Why is HiRes P the default sound processing strategy in SoundWave?
With a paired strategy, patients will have lower M levels because faster rate leads to greater loudness perception. If a clinician switches from P to S, less risk of overstimulating the patient.
Define current steering.
Two electrodes fire simultaneously, neither at 100% of their full power, and current is balance weighted between them to places of excitation between the two fixed contacts.
What is Fidelity 120?
There are 7 bandpass filters between each of the two electrode contacts, and each contact can be stimulated individually. 15 partnered electrodes across teh array x 8 equals 120 potential channels.
What are the rates for HiRes P and S, with and without Fidelity 120?
HiRes P: approximately 83,000 pulses/second
HiRes S: approximately 41,500 pulses/second
HiRes P and S w/ Fidelity 120, Optima P or S: approximately 55,000 pulses/second
(all are above the 40,000 tipping point for mimicking stochastic response)
