THE AUDITORY BRAINSTEM RESPONSE IN HEALTHY ADULTS AND ADULTS WITH ALCOHOL DEPENDENCE SYNDROME
The Auditory Brainstem Response (ABR) assesses brainstem function. This thesis explores the click and speech ABR in both healthy adults and adults with alcohol dependence syndrome (ADS). Experiment One undertook auditory-cognitive assessment including ABRs, of 60 healthy adults (30 women), aged 18-30 years. For waves III and V of the click ABR, women’s responses were earlier than men’s by 0.14ms and 0.19ms. For the speech ABR, onset and offset measures were earlier in women by at least 0.43ms. No effect for left vs. right ear was found in either case. Inter-rater reliability was found to be high (ICC2,1 ≥0.89) for the click ABR and good (ICC2,1 ≥0.75) for six of the seven peaks of the speech ABR. A comparison of ABRs to those from an older group of 12 adults aged 31-49 years (six women, matched control group for Experiment Two) found the stimulus to response lag for the speech ABR, was earlier (0.78ms) in the older women but within the expected range. Click and speech ABRs were repeated after 12 weeks and the representation of F0 for women was greater by 4.8 μV at the second recording. Experiment Two assessed the auditory-cognitive profile and ABRs of 16 adults (six women) aged 29-49 years, undergoing a treatment and rehabilitation programme for people with ADS. All participants had hearing thresholds within normal limits, but exhibited deficits in auditory-cognitive profiles compared to matched, healthy adults, including their click and speech ABRs. For the click ABR, men had significant delays in wave III (0.18ms) and wave V (0.22ms). For women there were significant delays for wave I (0.11ms) and wave V (0.22ms). For the speech ABR, men had significant delays in the onset measures of waves V (0.40ms) and A (0.36ms). Women had significant delays in waves V (0.45ms), A (0.48ms) E (0.66ms) and O (0.42ms). Testing was repeated after 12 weeks of abstinence and significant improvements in the click and speech ABR were observed. For men, average click ABR latencies improved for wave III (0.12ms) and wave V (0.22ms) and for women, wave V (0.08ms) improved. Significant improvements were also found for discrete peak and onset measures of the speech ABRs for both men and women. For men, average speech ABR latencies improved for wave A (0.23ms) and the duration of the VA complex (0.15ms). For women there were improvements in wave V (0.10ms), A (0.12ms) and E (0.33ms). These results add to the body of knowledge about the ABR and support its value as a clinical tool. They also provide new information about auditory-cognitive function in adults with ADS, for whom beneficial effects of abstinence are demonstrated. The ABR has a potential role in identifying people most at risk of alcohol related brain damage and in monitoring recovery with abstinence. Keywords Auditory Brainstem Response, Frequency Following Response, Speech ABR, Reliability, Alcohol Dependence Syndrome, Abstinence.