Behavioural and electrophysiological measures of auditory attention in right hemisphere brain damage

Abstract

Background: The right hemisphere (RH) has been found to play a major role in attention. However, most research has focused on the RH's role in visual attention associated with arousal, orienting, vigilance, and sustained and selective attention, and especially on the subsequent visuospatial deficits observed after RH brain damage. The RH's contribution to auditory attention and processing as well as the auditory abilities of the RH after brain damage has been explored to a lesser degree. Investigations using psychoacoustics and electrophysiology to examine the auditory processing abilities of non‐brain‐damaged and aphasic adults have been numerous and have revealed the influence of several variables on their findings including age, lesion site, lesion size, type of stimuli, etc. Investigations using these approaches to examine the auditory attention abilities of individuals with RH brain damage have been minimal. Furthermore, it is unclear whether both testing methods are examining similar components of auditory attention. Aims: The purpose of this investigation was to determine if electrophysiological testing provided additional information not available from behavioural central auditory processing evaluation for three patients with RH brain damage as the result of a stroke. Another purpose was to investigate whether electrophysiological findings were consistent with those obtained from the behavioural evaluation. Methods & Procedures: Participants were three males, aged 69, 71, and 78, all having suffered right hemisphere cerebro‐vascular accidents, resulting in mild cognitive‐communicative impairments. Experimental testing included: speech‐language evaluation through administration of the Western Aphasia Battery and the Token Test; hearing evaluation using routine pure tone audiometry, speech audiometry, and middle ear measurements; behavioural CAP assessment using the auditory attention measures of Pitch Pattern Sequence and Dichotic Digits; and electrophysiological testing, consisting of evaluation of late auditory evoked potentials (N100, P200, P300) with and without distraction using an oddball paradigm. Outcomes & Results: All three participants showed a consistent right ear advantage, with abnormal scores for the left ear on the behavioural central auditory attention tests. Electrophysiological testing revealed greater amplitudes for the right ear than the left ear for all three late auditory evoked potentials for the three participants. Furthermore, when auditory competition was introduced, the expected decrease in amplitude was observed for all three late auditory evoked potentials only for the right ear; all three participants exhibited this pattern. Conclusions: Thus, the electrophysiological findings were congruent with the behavioural central auditory processing results for the three participants, revealing a consistent right ear advantage for auditory attention. Based on these findings, it is evident that the direct relationship between behavioural central auditory attention skills and electrophysiology requires further investigation with other patients with right hemisphere brain damage.