Frequency-Following Response & APD Assessment Flashcards
What is the biological basis of auditory processing disorders?
- Some children with language-based learning difficulties may have deficits in auditory processing
- Older adults have difficulty processing the temporal aspects of speech
- Excessive noise or trauma may lead to auditory processing deficits in the presence of normal audiometric thresholds
What is the FFR?
- ABR to complex sounds (CABR)
- May use ecologically valid acoustic complex sounds (i.e. speech, music)
- Brainstem response should mirror the eliciting stimulus (has same periodicity, hence called the FREQUENCY-following response)
Describe the fidelity of the FFR.
- Benefit of FFR: fidelity in the time domain
- Just like ABR, 0.2-0.3 ms difference between ears can be alarming
- Reliability across time is an important factor in clinical assessments
Of what does ABR provide presentations of neural encoding?
1) TIMING: on/offest, temporal envelope
2) PITCH: encoding of F0
3) TIMBRE: FFT encoding of H2+
-Done through cycle-by-cycle neural phase-locking
Why record ABRs to speech?
- Can measure both onset and offset of response in cABR
- May be helpful in studying age-related processing deficits
- A clear FFR is only generated with stimuli that are presented at levels of at least moderate intensity (50-60 dB SPL)
Describe FFR recording.
- Filtered from 70-2000 Hz to isolate contributions of the brainstem
- Need to present thousands of times to see above noise floor
- Can obtain response with as few as 3 electrodes
Describe FFR analysis in the time domain.
- Timing & amplitude of any given peak
- RMS amplitude of a given range
- STR
- Correlation of responses across different conditions (i.e Q vs. N)
Describe FFR analysis in the frequency domain (FFT).
- F0
- Harmonics
Describe FFR analysis in the time-frequency domain.
- Pitch tracking
- Phase locking
What is pitch tracking?
- How well the brainstem tracks the frequency of the stimulus
- Tracks changing pitch contour
- May be meaningful in tonal languages
What is phase-locking?
-Robustness of signal encoding
What are the principal symptoms of children with APD?
- Reduced speech-in-noise performance
- Dyslexia
What effect does noise have on the FFR?
-Increased peak latencies and decreased peak amplitudes
What did Anderson et al. (2010) find?
- Greater timing delays (peak latencies) in poor SIN group compared to better SIN group in quiet vs. noise
- Degree of shift decreases until you reach the steady-state portion of the vowel
Describe FFR and reading disorders.
- Poor readers exhibited delayed peak latencies for onset trough, onset, and offset
- Less robust representation of speech stimulus (reduced sound mapping abilities in cortex?)
Describe the FFR and APD/SLI.
- Latency delays in children with SLI/APD are more pronounced with SLI
- Delays may be caused by not-robust representations of speech/stimuli in the brain
Can the FFR be used to predict later language/reading skills in children?
- Early ID/treatment of HL leads to better language outcomes if before 0;6
- Auditory processing deficits are associated with language/literacy deficits (shown in both behavioral and electrophysiological studies)
- In toddlers aged 3-4 years, FFR measures of speech encoding in noise related to measures of phonological processing at the time of test (also correlation between FFR in noise/pre-reading)
- Higher phonological processing score at 2;0 correlated with lower consonants-in-noise scores measured at 1;0
- A discriminant function analysis correctly classified 69% of children based on LD diagnosis
Can we obtain reliable FFRs to speech in infants?
- YES, it is possible
- Amplitude of Angela’s response was higher following stimulus onset
- Can see 100-Hz peaks repeated in response waveform
- Good correspondence between reps
- Van Dyke et al. (2017) found good representations of stimulus envelope and TFS in infants
Can the FFR predict later language development?
- Communication Development Inventory (CDI) questionnaire mailed out to parent at 1;6
- Infants with lower MCDI scores have lower periodicity
- Response peaks don’t repeat as nicely in at-risk group (also degraded response until SS)
What deficits are exhibited by children with ASD?
- Production and perception of prosody
- Neural encoding of speech
- Neural encoding of pitch change over time
Describe pitch tracking in children with ASD.
- Children with ASD have disrupted pitch tracking
- Response doesn’t follow the stimulus at all until the brain realizes that something meaningful is presented (looks like noise)
Describe Anderson et al. (2011).
- Older participants were assigned to top and bottom SIN groups based on HINT results
- Grouped matched on age, IQ, sex, and hearing
- Recorded responses to 170 ms /da/ presented in quiet and 6-talker babble
- Top SIN: larger amplitudes, larger F0
- Greater effects of noise in bottom SIN group (TR region)
- Change in morphology related to SIN
How can we study neural processing and speech-in-noise performance in older adults?
1) Animal models of aging
2) Distinguishing chronological age vs. biological age
What are some animal models of aging?
- Synaptopathy: Cunningham & Tucci (2015)
- Auditory nerve degeneration: Kujawa & Liberman (2006)
- Delayed neural recovery (midbrain): Walton et al. (1996)
- Latency increase (cortex): Hughes et al. (2010)
Describe chronological age vs. biological age.
- Does the FFR reflect biological aging?
- Audiogram may be matched for younger and older adults up to 4 kHz (similar to click ABR responses)
- FFR for older adults demonstrated smaller amplitudes and weaker synchrony
Describe Gordon-Salant et al. (2008).
- Older adults need longer silence duration (gaps)
- STR correlations are higher in younger than older adults in Ditch but not Dish (no gap)
- Phase locking robust in YNH vs. ONH groups and relates to 50% crossover for Dish/Ditch
Describe Presacco et al. (2016).
- Neural encoding of speech-in-noise
- Noise effects on response amplitude are greater in younger than in older adults
- However, despite greater reduction in response amplitude in noise, there are less effects of noise on overall morphology in younger adults
