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We report the case of a patient with left parietal damage (MH) who is selectively impaired at both detecting and localising targets defined in terms of their orientation. Performance was relatively good in other tasks where the target was defined either by a single feature (colour) or an orientation conjunction. The results are consistent with the idea that the dorsal stream supports some aspects of basic visual perception (i.e., the discrimination and localisation of orientation-defined targets). The effect of a parietal deficit may be to stress processing via the intact ventral stream, which groups information for object recognition, making differences in orientation less salient. Consistent with this, MH performed better when localising targets at a larger display size, where elements were less likely to group into a familiar shape and where local texture-based processes can come into play. In addition, MH's ability to localise a target was more impaired than his ability to detect a target, supporting the argument that orientation discrimination precedes (or operates independently of) feature localisation. [ABSTRACT FROM AUTHOR]

We examined the relations between attention and action in a patient with Balint's syndrome following bilateral damage involving the parietal lobes. The first two experiments used prolonged stimulus exposures and showed that unlike normals, the patient GK made independent actions to bilateral stimuli, even when explicitly instructed to make coordinated reaches. In contrast, bimanual actions to a single stimulus were coordinated in time. Experiments 3 and 4 employed reduced stimulus exposures to produce visual extinction. We found comparable extinction effects in detection and action, along with improved bimanual movements when the stimuli were grouped by collinearity and surface contrast, plus better coordination with bilateral stimuli proximity. The results are discussed in relation to the common role of visual selection processes in perception and action. [ABSTRACT FROM AUTHOR]

Hanley and Kay (1997) reported the case of a patient (PS) who showed effects of imageability on tests of auditory repetition, but whose errors were phonological rather than semantic. They argued that this pattern of performance could be explained in terms of a partial impairment to both lexical and nonlexical repetition routes so long as some interaction between the two routes was allowed, consistent with Hillis and Caramazza's (1991) "summation" hypothesis. The present paper investigates the performance of a new patient (MF) who also makes a large number of phonological errors when repeating words of low imageability. MF performs at a similar level to PS on tests of picture naming, but is less impaired than PS when repeating words and nonwords. It is argued that the pattern of performance that MF demonstrates on these and on a wide range of other tests of word production and comprehension can be readily accommodated in terms of the dual-route account of impaired auditory repetition that Hanley and Kay (1997) put forward. However, we argue that it is difficult to explain these patients' performance in terms of models of auditory word repetition that do not incorporate a separate nonlexical repetition route (Dell, Schwartz, Martin, Saffran, & Gagnon, 1997; Foygel & Dell, 2000). [ABSTRACT FROM AUTHOR]

We report two sets of data on object and action selection in a patient, ES, with an impaired ability to make task-based actions to objects. In simple action tasks, ES often made familiar actions to objects rather than the action appropriate to the task rule. We show that, despite having impaired selection of action, ES was able to select the target for action (based on salient perceptual differences). Relatively good object selection occurred even when the distractor had a stronger learned response than the target. In addition we show that distractors close to the path of action to a target can compete for, but are rejected from, selection along with any concurrently activated response. Suppression of an activated response improved performance, when the response would have been inappropriate to the task. [ABSTRACT FROM AUTHOR]

Assesses the manual interferences responses of direct action from a neuropsychological evidence. Determination of interference responses by stimulus familiarity and by spatial relations of the hand to the object; Effects of effectors and spatial uncertainty on interference responses.