Challenging Populations Flashcards
Describe the ABR waveform for ANSD.
- Flat line
- Typically absent of abnormal
Describe the recording parameters for a typical waveform.
- Amplitude: 1-10 uV
- Spectrum: 0.1-30 Hz
- Number of averages needed: 100
Describe hearing levels for ANSD.
- Can range from normal to profound (continuum from no auditory complaints to total lack of sound awareness)
- HL can fluctuate
Describe ANSD and speech understanding.
- May be okay in Q but definitely poor in N
- Delayed N1 latency (associated with worse speech perception in noise)
Compare CAEPs between AN and NH listeners.
- Poor CAEP morphology, reduced peak amplitude, and delayed latencies compared to NH CAEPs
- As SNR worsens, AN cortical potentials have delayed latencies/reduced amplitudes much faster than NH cortical potentials
Describe P1 latency is a biomarker for speech perception development.
- Normal P1 latencies associated with normal P1 latency
- Earlier intervention is associated with normal P1 latency
- Children fitted earlier with HAs, the more normal the brain was able to normalize P1 latencies as a result of amplification
Why would there be a cortical response when ABR is absent?
- ABR reflects highly synchronous discharges with precision on the order of fraction of ms
- Synchrony is necessary for speech perception in noise
- Cortex is able to make use of varied and limited input
How do cochlear implants provide the opportunity to study central auditory pathways?
- Maturation
- Relationships with speech perception
- Relationship with speech production
- Sensitive time periods/cortical reorganization
What is the sensitive period for cochlear implantation?
- 3.5 years, during which implantation occurs in a highly plastic central auditory system
- Implantation after 7;0 occurs in an already re-organized central auditory system
How rapidly does the auditory pathway change following the onset of stimulation of early implanted children?
- Approx. 8 months
- P1 latencies decrease more rapidly post-implantation in children implanted under 3;0 than in children implanted over 7;0
What is the relationship between development of central auditory pathways and development of speech perception skills?
-Lower performance on LNT associated with exaggerated/abnormal P1 latency
What is the relationship between development of central auditory pathways and development of early communicative behavior?
- Examined the link between babbling and auditory pathway development following implantation
- Is there a relationship between the rate of change in the auditory system and early communication in young CI recipient?
Describe cross-modal cortical reorganization.
- Same sound, different brain (same sound/implant but different outcome)
- The variable: what the brain does with the sound
- Brain activation with sound:
a. NH: auditory cortex
b. Early implanted: auditory and parietal cortices
c. Late implanted: parietal cortex - Differences in structure/connectivity determine how the brain responds to sound stimulation through the CI
- MEG activity in response to vibrotactile stimulation shows the cortical re-organization underlies the end of the sensitive period
Why would a clinician want to incorporate evoked potentials in a hearing aid fitting?
- Can be used for evaluation of aided functioning
- Objective hearing aid evaluation for: young infants, difficult-to-test people
Describe the automatic detection of cortical responses.
- Desirable characteristics:
- No reliance on a template
- Able to use information from contributing portions of waveforms
- Able to discount non-contributing portions of waveforms
-Recorded to three speech sounds: /m, g, t/
