Evaluation of attentional processing impairment in Obstructive Sleep ApneaSyndrome by the means of a dichotic listening task

The present research explored the attentional impairments in OSAS patients through a dichotic listening task with attention forced to one ear. This ra tionale was adopted to clarify the conflicting data obtained with usual neu ropsychological tests which seemed not well suited to explore attentional i mpairments (Telakivi et al., 1993). OSAS patients, with an Index of Apneas per Hour (IAH) higher than ten, Snorers (LAH < 10) and a control group of y ounger students had to detect auditory verbal targets presented dichoticall y with verbal distracters. The distractors differed from the target either by an acoustic or a semantic feature. Attention was oriented toward the tar get either by a peripheral (exogenous orienting) or by a central cue (endog enous orienting). The main concern of this study was to specify the compone nts which could be preserved or altered in OSAS cognitive performance. Resu lts showed that the verbal reaction times to detect a target in the attende d ear were slower in the apneic patients than in the matched snorers and co ntrol students. This lengthening (160 ms on average) was observed when the detection of the target involves either controlled processing (i.e., a fema le voice for target and distracters; voluntary orienting of the attention t owards the attended ear) or an automatic processing (i.e., a female voice f or target and a male voice for distracters; automatic capturing of the atte ntion by a lateralized tone cue). Although this pattern of results was not entirely predicted, it clearly revealed that OSAS presented attentional imp airments: Namely, a difficulty to select an auditory verbal target presente d with a verbal distracter. We discussed several. hypotheses about the natu re (auditory or attentional), the locus (cochlear, brainstem, and central) and the cause (nocturnal hypoxemia or fragmented sleep) of this dysfunction ing.