1/2. Two types of auditory neglect.Auditory neglect, defined as inattention to stimuli within the left hemispace, is mostly reported in association with left ear extinction in dichotic listening. However, it remains disputed as to how far dichotic extinction reflects a primary attentional deficit and is thus appropriate for the diagnosis of auditory neglect. We report here on four patients who presented left ear extinction in dichotic listening following right unilateral hemispheric lesions. Auditory spatial attention was assessed with two additional tasks: (i) diotic test by means of interaural time differences (ITDs), simulating bilateral simultaneous spatial presentation of the dichotic tasks without the inconvenience of interaural intensity or content difference; and (ii) sound localization. A hemispatial asymmetry on the ITD diotic test or a spatial bias on sound localization were found to be part of auditory neglect. Two patients (J.C.N. and M.B.) presented a marked hemispatial asymmetry favouring the ipsilesional hemispace in the ITD diotic test, but did not show any spatial bias in sound localization. Two other patients (A.J. and E.S.) had the reverse profile: no hemispatial asymmetry in the ITD diotic test, but a severe spatial bias directed to the ipsilesional side in sound localization. J.C.N. and M.B. had mainly subcortical lesions affecting the basal ganglia. A.J. and E.S. had cortical lesions in the prefrontal, superior temporal and inferior parietal areas. Thus, there are two behaviourally and anatomically distinct types of auditory neglect characterized by: (i) deficit in allocation of auditory spatial attention following lesions centred on basal ganglia; or (ii) distortion of auditory spatial representation following frontotemporoparietal lesions.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |
2/2. Rule-abstraction deficits following a basal ganglia lesion.The cognitive profile of a patient, PM, who had damage to the right basal ganglia as the result of a stroke was investigated. Whilst most cognitive functions were intact, she showed specific neuropsychological deficits, most notably a difficulty in developing, through abstraction of the relevant information, a higher-level rule by which to guide behaviour. The types of rule affected were those based upon an attentional set (attending to a particular dimension of stimulus features, such as 'shape') or a response strategy (continuing to apply a previously successful pattern of responses). The learning of lower-level rules based on stimulus-reward values was spared, as was the ability to apply an instructed rule and to discontinue use of rules which were no longer appropriate. These data provide evidence for the dissociability of cognitive functions within the basal ganglia.- - - - - - - - - - ranking = 1keywords = behaviour (Clic here for more details about this article) |