Biomedical subjects

Sharon Morein-Zamir

Publications and source records attributed to Sharon Morein-Zamir.

11 recordsLinked to original sources

PubMed2006

Fixation offset and stop signal intensity effects on saccadic countermanding: a crossmodal investigation.

Two experiments utilized the stop signal paradigm to examine whether fixation offset and stop signal intensity influenced saccadic inhibition. There was a robust fixation offset effect on saccadic latencies. However, contrary to expectations, fixation offset did not influence saccadic inhibition latencies. Importantly, saccadic inhibition latencies were found to be influenced by stop signal salience, with a more intense signal leading to faster stopping. This pattern of results was observed whether the stop signal was presented in the visual or auditory modality. The results provide new insights into the mechanisms of inhibition and help resolve previous inconsistencies in the literature.

Acoustic Stimulation↗

PubMed2006

Compatibility effects in stopping and response initiation in a continuous tracking task.

Two experiments explored stopping performance using a new stimulus-response compatibility effect spanning action initiation and stopping. Participants tracked a sometimes-moving, sometimes-stationary target by controlling the speed of a response marker via a force sensor. In the compatible condition, participants pressed the sensor in response to the target moving and stopped pressing in response to the target stopping. In the incompatible condition, participants stopped pressing in response to the target moving and initiated pressing in response to the target stopping. Response initiation and stopping were found to be faster under compatible than under incompatible conditions, regardless of whether compatible and incompatible trials were blocked or mixed. These findings indicate that stopping, like response initiation, is influenced by stimulus-response properties such as compatibility. This in turn suggests that stopping is governed by constraints similar to those of other behaviours.

Adolescent↗

PubMed2005

On audiovisual spatial synergy: the fragility of the phenomenon.

Recent literature has highlighted the importance and ubiquity of cross-modal links in spatial attention, whereby shifts in attention in one modality often induce corresponding shifts in other modalities. We attempted to provide further evidence for the case of audiovisual links during sustained endogenous attention by addressing several potential methodological confounds in previous demonstrations. However, we failed repeatedly to reproduce the phenomenon of spatial synergies between auditory and visual attention, found by Driver and Spence (1994) and frequently cited to support the automatic nature of cross-modal attention links. We discuss the results in light of recent evidence about cross-modal spatial links during sustained attention and support the idea that such links can weaken or even disappear under certain circumstances, such as during periods of sustained attention. The implication is that individuals can select inputs from different modalities from different locations more easily than previously had been thought.

Adult↗

PubMed2004

Differential processing of word and color in unilateral spatial neglect.

The aim of the present study was to investigate mechanisms underlying processing of contralesional visual stimuli in brain-damaged patients with unilateral spatial neglect (USN). Nine right-hemisphere-damaged stroke patients with left-sided neglect and nine controls performed a reaction-time task involving manual response to a central color patch (target stimulus) flanked to the left or right by a Stroop stimulus they had to ignore. While the word dimension of the flanker affected patients' responses considerably and equally when presented to either side, the color dimension of the flanker had no effect when presented to the left, but had a large effect when presented to the right. Four of the patients performed a control task requiring same/different judgments between either of the two flanker dimensions (color and word) and the central target. Their performance indicated that they were able to process color information from the contralesional field, despite their results in the first experiment. These findings demonstrate a dissociation between how the patients processed different dimensions of the same stimuli and imply that the extent of processing in the contralesional hemifield depends both on task requirements and on the exact features of the stimuli. The implications of these results on normal attentional mechanisms is also discussed.

Adult↗

PubMed2004

Executive functioning in boys with ADHD: primarily an inhibition deficit?

This study was aimed at: (1) testing whether boys with Attention Deficit/Hyperactivity Disorder (ADHD) demonstrate a deficit in response inhibition and deficits in other executive functions (EF), or alternatively, demonstrate a deficit in only response inhibition; (2) investigating which role associated factors, such as IQ, age, and performance on non-EF tasks play in EF in ADHD; (3) studying the association between the three different forms of inhibition studied here. Boys with ADHD were compared with normal control (NC) boys on five domains of executive functioning: inhibition (inhibition of a prepotent response, inhibition of an ongoing response, and interference control), planning, set-shifting, working memory, and verbal fluency. Boys with ADHD demonstrated deficits in interference control, inhibition of an ongoing response, planning, and letter fluency. After controlling for age, IQ, and non-EF measures, none of the EF deficits in ADHD remained. Finally, correlations between different inhibition measures were generally low, and correlations within domains of inhibition were not higher than correlations between domains of inhibition. This calls into question the distinctiveness of the different forms of response inhibition.

Age Factors↗

PubMed2004

Inhibiting prepared and ongoing responses: is there more than one kind of stopping?

Inhibiting movements has been investigated widely using the countermanding (stop signal) paradigm. Although it has been assumed that response inhibition, as measured by the countermanding task, generalizes to all forms of stopping, this has never been tested. In the present study, stopping performance in the countermanding paradigm was compared with stopping performance in a new paradigm in which a continuous-tracking task was used. Although stimulus presentations were matched across paradigms, the two tasks differed in the type of stopping required. In the countermanding paradigm, response inhibition latency was measured prior to response execution-this is, it was inferred from the successful withholding of a go response. In the new paradigm, response inhibition was carried out after response execution-that is, it was measured as the time to begin stopping a continuous tracking response. Results indicated that stopping latencies between the two paradigms were highly correlated, providing strong evidence that stopping an unexecuted response engages the same mechanisms as stopping an ongoing response.

Adult↗

PubMed2003

Auditory capture of vision: examining temporal ventriloquism.

Four experiments investigated whether irrelevant sounds can influence the perception of lights in a visual temporal order judgment task, where participants judged which of two lights appeared first. In Experiment 1, presenting a sound before the first light and after the second light improved performance relative to baseline (sounds appearing simultaneously with the lights), as if the sounds pulled the perception of lights further apart in time. Experiment 2 ruled out an alerting explanation for this effect and indicated that the performance improvement resulted from the second sound trailing the second light. Experiment 3 excluded the possibility that leading or simultaneous sounds were interfering with performance and revealed that only the second sound had an effect within the temporal window known to support multisensory integration. Experiment 4 demonstrated that sounds intervening between the two lights led to a decline in performance, as if the sounds pulled the lights closer together. The results suggest a 'temporal ventriloquism' phenomenon analogous to spatial ventriloquism.

Acoustic Stimulation↗

PubMed2003

The effect of methylphenidate on three forms of response inhibition in boys with AD/HD.

The current study was aimed at (a) investigating the effect of three doses methylphenidate (MPH) and placebo on inhibition of a prepotent response, inhibition of an ongoing response, and interference control in Attention Deficit/Hyperactivity Disorder (AD/HD), and (b) studying dose-response relations for the three forms of response inhibition. To meet these aims, the following tasks were selected: two versions of the Stop Paradigm for inhibition of a prepotent response, a Circle Tracing Task and a recently developed Follow Task for inhibition of an ongoing response, and the Stroop Color-Word Test and an Eriksen Flanker Task for interference control. These tasks were administered to 23 boys with AD/HD during four treatment conditions: 5 mg MPH, 10 mg MPH, 20 mg MPH, and placebo. A pseudorandomized, multiple-blind, placebo-controlled, within-subject design was used. As hypothesized, inhibitory control in children with AD/HD improved under MPH compared to placebo. However, this effect was only significant for inhibition of a prepotent response and inhibition of an ongoing response (as measured by the Follow Task), but not for interference control. The relation between treatment condition and response was linear. However, this linear relation was due to improved inhibitory control under MPH compared to placebo, because no effects of MPH dose were observed for any of the response inhibition measures.

Attention↗

PubMed2003

Individual stopping times and cognitive control: converging evidence for the stop signal task from a continuous tracking paradigm.

The present study introduces a continuous tracking procedure to investigate cognitive stopping in individual trials. Our measure of stopping performance had a mean similar to mean stopping times estimated in the stop signal paradigm, suggesting a common underlying process. Additional findings indicate that stopping performance and tracking performance were dissociable. First, while stopping times were primarily affected by stop signal modality, tracking performance was primarily affected by tracking difficulty. Second, tracking performance influenced tracking but not stopping in immediately following trials. Stopping influenced neither tracking performance nor stopping in immediately following trials. Finally, there was no correlation between tracking performance and stopping performance, or any dependency between them as found in the conditional means.

Adult↗

PubMed2002

Orienting attention in aging and Parkinson's disease: distinguishing modes of control.

Past research on attentional orienting and Parkinson's disease (PD) has been compromised because the experimental paradigms tended to confound different forms of orienting. We sought to overcome this by examining the attentional orienting of three distinct groups (PD-patients, age-matched controls, and young controls) on five different tasks, four of which isolated pure forms of orienting. On two covert orienting tasks PD patients oriented volitional (Experiment 1) and reflexive (Experiment 2) covert attention in a healthy and normal manner for their age. On two overt orienting tasks, PD patients were found to execute volitional eye movements that were prone to undershoot their target goal (Experiment 3), and reflexive eye movements that were unusually fast (Experiment 4). When required to perform an antisaccade task (Experiment 5), which combines reflexive and volitional modes of overt orienting, PD patients performed normally. This indicates that using a task which combines different modes of orienting creates a situation that is more than the sum of its parts. Together our study supports the thesis that it is crucial to isolate and investigate different modes of attentional control.

Aged↗

PubMed2002

The importance of irrelevant-dimension variability in the stroop flanker task.

Two experiments in which the Stroop flanker task was used were conducted in order to examine the influence of irrelevant dimension invariance on congruency effects. Participants responded manually to a central color patch flanked by a Stroop stimulus. In Experiment 1, invariance in flanker location was found to have no influence on word and color congruency effects. In contrast, invariance of flanker identity led to the disappearance of congruency effects. Experiment 2 indicated that the elimination of a congruency effect was restricted to the dimension that remained constant and did not influence the congruency effect of the other dimension that was presented at the same location. Results suggest that variance is a prerequisite to congruity effects, determining the activation of irrelevant dimensions.

Attention↗