CAEPs

Question 1

What is the 10-20 system?

Answer 1

• Method that describes and applies the location of scalp electrodes
• Developed to ensure standardized reproducibility so results can be compared across time
• Based on the relationship between the location of an electrode and underlying area of cerebral cortex

Question 2

What is the typical maturation in the CAEP response?

Answer 2

Children
- Most prominent components are P1 and N2

As you get older, the peaks are smaller and P1 becomes minimized

• N1 becomes more prominent
• N2 is minimal

Older people tend to have more exaggerated amplitudes for P1 and N1

Question 3

How do you analyze the CAEP response?

Answer 3

Usually look at onset, but can also look at offset
- Duration of the stimulus coincides with duration of the response

Typical waveform

• Wide range of normal latencies and amplitudes
• A difference of 30 ms is not significant

Question 4

What are the clinical applications of P1-N1-P2?

Answer 4

Inter-response correlations describe changes in morphology (timing)

Correlations in noise are poorer for LP than for NL children
- 2 groups have the same response in quiet, but in noise it breaks down

Resistance to degradation in noise relates to auditory processing
- The higher the inter-response correlation relates to higher auditory processing scores

Resistance to noise in cortical responses may underlie normal perception of speech

Question 5

What CAEPs are elicited with an oddball paradigm?

Answer 5

P300, P3a, P3b

Mismatch negativity (MMN)

Processing negativity (Nd)

N400

Question 6

What is the P300, P3a, P3b CAEP?

Answer 6

• Diffuse (multiple neural generators)
• Multimodal (auditory, visual, somatosensory)
• Stimulus differences are large, obvious

Index of:

• Gross discrimination
• Sequential information processing
• Short term memory

Question 7

What are the clinical applications of P300, P3a, P3b?

Answer 7

• Biomarker for alcoholism
• Alzheimer’s
• ADHD
• Autism
• APD
• Language disorder
• Schizophrenia (auditory hallucinations)

Question 8

What P300 results are seen in subjects with APD?

Answer 8

• Children ages 7 to 14 with reading and writing disorders
• APD tests: SSW and speech-in-noise performance tests
• Children within the later latency group had abnormal SSW and speech-in-noise test results

Question 9

What is the mismatch negativity (MMN)?

Answer 9

• Response to stimulus change, echoic memory
• Objective measure of auditory discrimination
• Elicited by minimal (just perceptible) acoustic differences
• Passively elicited, does not require a behavioral task
• Can be tested in newborn infants
• Originates in auditory thalamus and cortex, frontal cortex, non-primary pathway especially

Question 10

What are the acoustic differences which elicit a mismatch response in the MMN?

Answer 10

• Frequency
• Intensity
• Duration
• Location
• Phonetic content
• Inter-stimulus interval
• Sound patterns
• Speech
• Music

Question 11

What is the acoustic change complex (AAC) (P1-N1-P2 change complex)?

Answer 11

• Cortical auditory-evoked response
• Analogous to N1/P2
• A response to change in an ongoing acoustical stimulus
• Not elicited by an oddball paradigm

Question 12

What are the clinical applications of the P1-N1-P2 change complex?

Answer 12

Benefits of training- CIs

- Only investigational at this state

Question 13

Why don’t the late responses work for clinical purposes?

Answer 13

• Variability in responses
• Don’t need to wear a cap for a cortical response
• Cannot say that one individual response is abnormal