Week 4 ALLR PDF

10/07/2024 WEEK 4 - ALLR 1 WHAT ARE CAEPs? CAEPs Cortical Auditory Evoked Potentials 40 Hz AMLR ALLR Response...

10/07/2024 WEEK 4 - ALLR 1 WHAT ARE CAEPs? CAEPs Cortical Auditory Evoked Potentials 40 Hz AMLR ALLR Response MMN P300 2 ALLR 3 1  10/07/2024 ALLR Noted in 1939 by Pauline Davis as an auditory component of the EEG. Hallowell Davis and colleagues: 1960s and into 1970s. Topographic mapping of the response in 1970. What does this mean? Resurgence interest of clinical application with computed evoked potential topography techniques and sophisticated stimulation (e.g. speech stimuli). Generated by higher regions of auditory CNS Recorded in a time period of 50-400ms after acoustic stimulation. Recorded at a slower rate 4 ALLR Auditory Evoked Potentials: Exogenous response Endogenous response ▪ Characteristics determined ▪ Characteristics influenced by external stimuli by internal cognitive E.g. Auditory Click or processes Toneburst E.g. P300 What type of response is the ALLR? 5 ALLR N1 and P2 - auditory cortex Represents dentritic neural activity rather than action potentials 6 2  10/07/2024 ALLR There are a variety of auditory late response components in the latency region of about 50 to 500ms. ALR is large in amplitude, usually within the 3 to 10 μvolt range. 7 ALLR Auditory Evoked Potentials: Obligatory Discriminative Responses to the Processing-contingent physical properties of sensory potentials (PCPs) stimuli. associated with further processing of sensory stimuli. ABR, ASSR, AMLR,ALLR MMN, P300 8 ALLR Age Handedness Attention Children: prominent P1 & N2 Alexander and Polich (1997) left handed Amplitude of N1 and P2 waves are Adults: P1, N1, P2 sequence adult subjects had: altered differentially when the Developmentally, P1 appears 1st. Shorter N1 latencies subject is paying close attention to P2 and N2 appear 2nd (3-6 Smaller P2 amplitudes the stimulus or listening for a years). Shorter N2 latencies change in some aspect of the N1 isn’t observed until after 3 stimulus. years For N1, ↑ attention to signal is Latency and amplitude values for associated with a prominent ↑ all components do not reach amplitude adult values until 16-18 years. P2 wave appears to ↓with↑ Latency ↓ and amplitude ↑ with attention. (Hall, 2007; De Chicchis, age. Carpenter, Cranford & Hymel, 2002) 9 3  10/07/2024 ALLR Auditory training Estimating hearing sensitivity ALLR as SOL tool ALR is affected by auditory training. ALLR can be time-efficient with software that Most sensitive to lesions in the superior Specific alterations noted to N1-P2 automates manual tasks such as waveform aspect of the temporal lobe (superior and complex- increase in amplitude manipulation and waveform averaging lateral surfaces of Herschl’s (Tremblay, Kraus, McGee, Ponton & Provides frequency specific information gyrus) and along the sylvian fissure. Otis, 2001) How can this test be used Compared to ABR, ALLR (Lightfoot, 2010): Sensitivity with this information in Can use longer duration TB stimuli for 70% APDs mind? better frequency specificity 73% to bitemporal lesions Is more resilient to electrophysiological 100% to superior temporal gyrus noise regions Represents a more complete picture of the (Wilson, 2009) auditory system Provides a more accurate threshold estimation Response morphology does not degrade at low frequencies Patient does not have to be asleep Disadvantages over ABR is that it can be used in adults and older children only. 10 ALLR Assessment of hearing sensitivity in adults Correlates well with perception and discrimination of auditory stimuli Indicated as a std or add test in any assessment of the function of the auditory cortex. Not indicated as a test for cortical mass lesions when MRI is affordable and available (Wilson, 2009) 11 ALLR Hearing aids and CI fittings Auditory neuropathy/dys-synchrony Rance et al (2002) showed subjects with AN/AD with ALLR responses received significantly more benefit from amplification than those with absent ALLR responses Effects of Hearing Aid Amplification on CAEPs Billings, Tremblay, Souza & Binns (2007) found that on normal hearing individuals under aided and unaided situations, amplitude increased and latencies decreased with increase in stimulus intensity as expected but no significant effect on 20dB hearing aid gain – highlights difference in hearing aid signal processing vs. stimulus intensity change Congenitally deaf, early implanted children Sharma, Dorman and Spahr (2002) found that that ALLR undergoes many changes within the first 6- 8months following implantation. P1 latency decreases more rapidly in CI users after implantation in comparison to age matched peers. 12 4  10/07/2024 ALLR 13 ALLR 14 ALLR 15 5  10/07/2024 ALLR For SOL testing ▪ Original and at least 1 repeat waveform for each ear e.g. R70,R70,L70,L70 ▪ Amplitude 2-3 X larger than the prestimulus interval For threshold testing ▪ Similar to threshold ABR-decrease intensity until no response and then increase intensity until response is present ▪ Last latency at which response is evident is threshold ▪ Amplitude is 2-3X larger than prestimulus interval 16 ALLR Sequential peaks labeled by N (negative voltage) or P (positive voltage), including P1, N1, P2 and N2 as recorded with a vertex electrode. Major components occur within 75 to 200ms after a moderate stimulus level. 17 ALLR Normal Variations Morphology is variable ▪ Changes or subtle variation can be markedly influenced by subject state & signal ▪ Latency and amplitude may vary Abnormal Patterns ▪ Reduced amplitudes ▪ Prolonged latencies ▪ Polarity reversal for selected components ▪ Total absence of one/more components 18 6  10/07/2024 ALLR P1~ 50-90ms N1~ 90-150ms- also called N100, obligatory component of N100 P2 ~ 160-200ms N2~ 180-250ms 19 ALLR SOL: Original and repeated waveform for each Morphology is variable: subject state & ear. signal Assessment of hearing sensitivity in adults: Latency & amplitude variable Ampl 2-3 X larger than the prestimulus Reduced amplitudes interval. Prolonged latencies Threshold: Similar to threshold ABR-decrease, Polarity reversal for some components Last latency at which response is evident is Absence of components threshold – correlate well with perception and Not indicated as a test for cortical mass discrimination of auditory stimuli. lesions when MRI is affordable and available Indicated as a std or add test in any (Wilson, 2009) assessment of the function of the auditory cortex. 20 REFERENCES ▪Billings, C.J.,Tremblay, K.L.,., Souza, P.E., & Binns, M.A. (2007). Effects of Hearing Aid Amplification and Stimulus Intensity on Cortical Auditory Evoked Potentials. Audiol Neurotol, 12:234-246. ▪De Chicchis,A.R., Carpenter, M., Cranford, J.L., Hymel, M.R. (2002). Electrophysiologic Correlates of Attentionversus Distraction in Young and ElderlyListeners. Journal of American Academy of Audiology, 13:383-391. ▪Hall, J.W. (2007). New Handbook of Auditory Evoked Responses. Boston: Pearson Education Inc. ▪Lightfoot, G. (2010).The N1-P2 Cortical Auditory Evoked Potential in threshold estimation. Insights in Practice for Clinical Audiology. Retrieved from http://www.otometrics.com/~/media/DownloadLibrary/Otometrics/PDFs/ICS%20Chartr%20EP%20200/Insights_Feb_2010_std.pdf individualised and ▪Lightfoot, G., & Kennedy,V. (2006). Cortical Electrical Response Audiometry Hearing Threshold Estimation: Accuracy, Speed and deficit-specific the Effects of Stimulus Presentation Features. Ear and Hearing, 443-456. (diagnosis drives ▪Plourde, G. (2006). Auditory Evoked Potentials. Best Practice & Research Clinical Anaesthesiology, 20(1). treatment) ▪Rance, G., Cone-Wesson, B., Wunderlich, J. & Dowell, R. (2002). Speech perception and cortical event related potentials in children with auditory neuropathy. Ear and Hearing, 23(3), 239-253. ▪Sharma, A., Dorman, M.F., Spahr, A.J. (2002). Rapid development of cortical auditory evoked ▪potentials after early cochlear implantation. NeuroReport, 13(10): 1365-1368 ▪Tremblay, K.L., & Kraus, N. (2002) Auditory training induces asymmetrical changes in cortical neural activity. Journal of Speech and Language Hearing Research, 45, 564-572. ▪Tremblay, K., Kraus, N., McGee,T., Ponton, C., & Otis, B. (2001). Central Auditory Plasticity: Changes in the N1-P2 Complex after Speech-Sound Training. Ear and Hearing, 79:90 ▪Wunderlich, J.L., Cone-Wesson, B.K., & Shepherd, R. (2006). Maturation of the cortical auditory evoked potential in infants and young children. Hearing Research, 212: 185-202 21 7