Automatic orienting of visuospatial attention in Parkinson's disease.

The basal ganglia are involved in not only motor behavior, but also other more cognitive processes, such as attention. We tested Parkinson's disease (PD) patients in a task that measures reflexive orienting of spatial attention. Seven patients with idiopathic PD and eight control subjects performed a covert orienting task where spatial attention was directed by means of exogenous cues (luminance increments) with no predictive validity for target position. The subjects' task was to make a speeded saccade to a visual target, which appeared a variable time after onset of the cue either in the cued or an uncued spatial position. There was no overall difference between PD patients and control subjects in terms of the initial facilitation following reflexive cues, and later inhibition of return (IOR). However, PD patients differed from control subjects in two important respects. First, they were significantly faster than were control subjects on this reflexive visual-orienting task. Second, disease severity correlated with attentional performance; more advanced patients showed less initial facilitation but greater IOR. Thus PD patients show better performance on a reflexive saccade task and, for more advanced patients, greater IOR than control subjects. These findings are consistent with the possibility that reflexive attentional processes in PD patients may be more active.

Schizotypal traits, attention and eye movements.

1. Subjects demonstrating high, average, or low schizotypal traits participated in saccade tasks of eye movements and attention including: a simple saccade task, an antisaccade task, and/or a cued saccade task measuring both facilitatory effects of cuing and inhibition of return (IOR). 2. Subjects were recruited based on their scores on the Rust Inventory of Schizotypal Cognitions (RISC) and then were given Raine's Schizotypal Personality Questionnaire (SPQ) (1991). 3. Subjects scoring high in schizotypy demonstrated increased errors on the voluntary eye movement task (antisaccade task) (p<0.05). Performance on the reflexive saccade task was not impaired in high compared to low schizotypals, but may have been enhanced as demonstrated by a negative correlation between scores on the SPQ and performance on this task. For the cued saccade task, there were no overall differences in cueing effects between schizotypal groups, however there was a laterality difference between low versus high scoring schizotypal subjects. 4. These results indicate distinct differences in tasks of overt orienting (saccade and antisaccade tasks) and covert orienting tasks (cued saccade task). The patterns of performance by our schizotypy subjects, including impaired voluntary saccade, enhanced reflexive saccade, and lateralized performance on the cued saccade task, are consistent with the performance of schizophrenic patient populations. Thus, our study supports the previous findings of a physiological relationship between schizotypal personality and schizophrenia.

Inhibition of return in manual and saccadic response systems.

When nonpredictive exogenous visual cues are used to reflexively orient covert visual spatial attention, the initial early facilitation for detecting stimuli at cued versus uncued spatial locations develops into inhibition by 300 msec following the cue, a pattern referred to as inhibition of return (IOR). Experiments were carried out comparing the magnitude and time course for development of IOR effects when manual versus saccadic responses were required. The results showed that both manual and saccadic responses result in equivalent amounts of facilitation following initial exposure to a spatial cue. However, IOR developed more quickly for saccadic responses, such that, at certain cue-target SOAs, saccadic responses to targets were inhibited, whereas manual responses were still facilitated. The findings are interpreted in terms of a premotor theory of visual attention.

Control of voluntary and reflexive saccades in Parkinson's disease.

Eight patients with idiopathic Parkinson's disease (PD) were compared with a group of age-matched controls on both reflexive saccade and antisaccade tasks. While reflexive, visually guided saccades led to equivalent performance in both groups, PD patients were slower, made more errors, and showed reduced gain on antisaccades (AS). This is consistent with previous results showing that PD patients have no difficulty with reflexive saccades but show deficiencies in a number of voluntary saccade paradigms. Moreover, visual information in the form of landmarks improves AS performance more for PD patients than controls, a finding analogous to results seen with other motor acts such as target-directed pointing. Results are discussed in terms of a two-process model of attention and eye movements.

Selective attention to global and local structure of objects: alternative measures of nontarget processing.

When individuals are asked to report either the global or the local level of structure in a stimulus pattern located inside a relevant object, distractors located within an irrelevant object will interfere only if they are at the same level of structure as that of the target item (Briand, 1993; Paquet & Merikle, 1988). The basis of this level-specific filtering is unclear, as is the true level of semantic analysis for the ignored items. In the present series of experiments, multiple measures of nontarget processing were used to assess concurrent interference, negative priming, and a category effect supposedly reflecting a more abstract level of semantic analysis. These different indicants were assessed in three experiments in which form, color, or a spatial precue was used to direct attention to the relevant stimulus pattern. Overall, cuing by form produced poorer spatial selectivity, whereas spatial precues and color led to better selectivity. However, the three measures of nontarget processing were not equally affected by these manipulations, with global information showing more evidence for semantic analysis than for local analysis regardless of the type of selection cue used. The results suggest that inhibition is not the basis of target selection when ignored items are local, but that it may be used when global items are ignored.

Is Posner's "beam" the same as Treisman's "glue"?: On the relation between visual orienting and feature integration theory.

In the present study we investigated whether the visually allocated "beam" studied by Posner and others is the same visual attentional resource that performs the role of feature integration in Treisman's model. Subjects were cued to attend to a certain spatial location by a visual cue, and performance at expected and unexpected stimulus locations was compared. Subjects searched for a target letter (R) with distractor letters that either could give rise to illusory conjunctions (PQ) or could not (PB). Results from three separate experiments showed that orienting attention in response to central cues (endogenous orienting) showed similar effects for both conjunction and feature search. However, when attention was oriented with peripheral visual cues (exogenous orienting), conjunction search showed larger effects of attention than did feature search. It is suggested that the attentional systems that are oriented in response to central and peripheral cues may not be the same and that only the latter performs a role in feature integration. Possibilities for future research are discussed.