Biomedical subjects

Avishai Henik

Publications and source records attributed to Avishai Henik.

26 records · Page 2Linked to original sources

PubMed2002

Attentional control and word inhibition in schizophrenia.

Previous studies have suggested that schizophrenia patients do not utilize contextual information efficiently to modulate attentional performance. The goal of the current study was to compare the utilization of context in modulating responses to irrelevant information on the Stroop task between a group of schizophrenia outpatients and matched controls. A single-trial version of the Stroop task was used to investigate performance on the Stroop task under three expectancy conditions. Eleven schizophrenia outpatients (on and off antipsychotic medication) and sixteen matched controls were tested. The schizophrenia patients showed: (1) augmented facilitation; (2) interference comparable to normals; and (3) normal ability to reduce interference under certain experimental circumstances. Schizophrenia patients were able to utilize contextual information under certain conditions and could modulate the magnitude of irrelevant word interference, although they were not able to overcome the prepotent tendency to read the word during the Stroop task as effectively as normals, which was reflected in greater Stroop facilitation. This suggests that the integrity or impairment of cognitive control functions in schizophrenia is related to the complexity of the context representation required to support that function.

Adult↗

PubMed2002

Attending to the thalamus: inhibition of return and nasal-temporal asymmetry in the pulvinar.

Inhibition of return (IOR) is a mechanism whereby the attentional system favors novel locations by inhibiting already scanned ones. An important question is what the neural structures are involved. Recently, we studied a patient with damage to the superior colliculus (SC) and concluded that the SC generates IOR. However, it is possible that IOR is generated beyond the colliculus, for example, by the pulvinar. In this paper we tested three patients with unilateral damage to the pulvinar and demonstrated that the pulvinar is not necessary for IOR generation, providing additional support to the suggestion that the SC generates IOR. In addition, since we used monocular presentation, we were able to furnish behavioral evidence for nasal-temporal asymmetrical representation of visual input in the pulvinar.

Analysis of Variance↗

PubMed2002

Implicit learning of emotional information under anesthesia.

Surgical stress activates the amygdala and secretion of norepinephrine, both involved in memory and unconscious processing of emotionally negative information. This study examined surgically induced facilitation of implicit learning of emotionally negative information. Thirty patients undergoing laparoscopic cholecystectomy under general anesthesia were tested. Between 2 and 4 h after surgery, patients provided word-associates to cues previously presented (old) or not previously presented during anesthesia (new). Half the cues were emotionally negative and half neutral. Patients took less time to provide correct associates to old emotionally negative cues than to new emotionally negative cues (p < 0.05). Spectral edge frequency (SEF) of cerebral activity during surgery converged with this finding. Implicit learning during general anesthesia may be stronger for emotionally negative information and is detected by SE.

Adult↗

PubMed2002

The development of internal representations of magnitude and their association with Arabic numerals.

Developmental aspects of number concepts were evaluated using participants from the beginning and end of first grade (6-7 years old), third and fifth grades (7-11 years old), and university (22 years old). Participants evaluated the numerical value or physical size of stimuli varying along both dimensions. The numerical distance effect appeared in all groups. In contrast, the size congruity effect started to appear only at the end of first grade. Based on our results, a model of internal representation of magnitude claiming that there are two different representations was propose. At the beginning of first grade children can automatically access only one of these representations and only from the end of first grade can they access both of these representations.

Adult↗

PubMed2002

Is an ant larger than a lion?

In order to examine the influence exerted by an irrelevant semantic variable in a comparative judgment task, we employed a Stroop-like paradigm. The stimuli were pairs of animal names that were different in their physical and semantic sizes (e.g., ant lion). Participants were asked to judge which of the two words was larger either in physical or in semantic size. Size congruity effect (i.e., faster reaction times with congruent than with incongruent stimuli) appeared in both semantic and physical judgments. The semantic distance effect (i.e., large semantic distances are processed faster than smaller ones), appeared only when the semantic dimension was relevant to the task. The findings indicate that when a word (animal name) is presented, its meaning is accessed automatically. Part of this meaning (at least with our stimuli) relates to the size of the animal in real life. Processing of meaning of the size of the words is carried out in parallel with the extraction of the physical features of the presented stimuli.

Adult↗

PubMed2002

Immediate versus sustained processing in schizophrenia.

A Stroop negative priming (NP) task was used to assess immediate selective attention and priming in schizophrenia and schizoaffective disorder. Subject groups were comprised of 12 state hospital inpatients (41.8 +/- 7.5 years of age), 11 outpatients (39.8 +/- 7.5 years of age), and 16 controls (36.4 +/- 11.7 years of age). Compared with the control group and the outpatients, inpatients failed to exhibit NP [F(2,36) = 6.09, p < .01], despite exhibiting equivalent Stroop RT interference (p > .05). Error rates did not differ significantly between the 3 groups. Although medication types and dosages were similar between the 2 patient groups, length of illness was significantly longer in the inpatients (19.8 years) than in the outpatients (12.4 years; p < .05). Positive symptom ratings were also significantly higher in the inpatients. The finding of reduced NP in the state hospital patients appears to be related to severity of symptomatology and chronicity of illness.

Adult↗

PubMed2002

Time course of inhibition and facilitation in patients with schizophrenia.

INTRODUCTION: Negative priming (NP) paradigms have been used extensively to understand the nature and time course of inhibitory deficits in patient populations. A majority of these studies have reported abnormal NP effects, with patients showing faster reaction times on NP sequences compared to the slowing displayed by controls. METHODS: A Stroop NP task was employed to measure immediate (within-trial) attentional processing as well as the sustainment (between-trial) of these processes in 12 medicated schizophrenia inpatients and 13 matched controls. Two response stimulus intervals (RSIs) were presented (500 ms and 2000 ms). Within-trial Stroop effects (interference and facilitation) and between-trial priming effects (negative and positive priming) were measured. Clinical symptomatology and duration of illness were also examined. RESULTS: At short RSIs of 500 ms, chronically ill state hospital schizophrenia patients failed to exhibit NP. In contrast, the control subjects exhibited normal NP at the short RSI but this priming faded at the long 2000 ms RSI and was no longer significant. The facilitatory priming effects remained stable across time in both groups. CONCLUSIONS: These results suggest that schizophrenia patients are better able to inhibit irrelevant stimuli that are immediate, but the sustainment of inhibition across very short time intervals (500 ms) may fade compared to controls.

Journal Article↗

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↗