Blunted left cingulate activation in mood disorder subjects during a response interference task (the Stroop).

Functional neuroimaging studies have found abnormal anterior cingulate activity in depressed subjects, and other studies have shown that the cingulate gyrus becomes active in healthy subjects during interference tasks. The authors hypothesized that subjects with mood disorder might show blunted cingulate activation during the standard Stroop interference task or during a modified version involving sadness-laden words. In contrast to 11 age- and sex-matched healthy control subjects who activated the left cingulate during the standard Stroop, 11 mood-disordered subjects activated the right anterior cingulate gyrus only slightly and instead showed increased activity in the left dorsolateral prefrontal and visual cortex. This study supports theories of blunted limbic and paralimbic activation and abnormal cingulate activity in depression and adds to the growing knowledge of the functional neuroanatomy of depression.

Selective attention and response competition in schizophrenic patients.

Visual distractibility was studied in schizophrenic patients. Subjects had to respond to target stimuli while they ignored the visual context, which was either congruent, neutral, or incongruent with respect to the target stimulus. Eighteen schizophrenic patients and 18 healthy subjects performed this flanker task. Schizophrenic patients did not show increased distractibility compared with healthy subjects, and both groups showed the same attenuation of visual context effects when the spatial distance between target and flanker stimuli was increased. The two groups showed the same amount of interference by incongruent visual context. Thus, schizophrenic patients did not show enhanced distractibility, spatial extension of attention, or response competition. When flanker and target stimuli were redundant, the responses of schizophrenic patients were less accelerated than those of healthy subjects.

[Schizophrenia and reverse-Stroop interference in the group version of the Stroop and reverse-Stroop test].

Previous studies showed that attentional task performance of schizophrenics was significantly inferior to that of normals. The classical Stroop Color-Word Interference Test is an example of such attentional tasks and performance on the "reverse" Stroop task is reported to discriminate schizophrenics from normals better than the regular Stroop task. These results suggest that schizophrenics are more susceptible to "reverse" Stroop interference in reading incongruent word-color combinations than normals. The group version of the Stroop and reverse-Stroop Color-Word Test, where the response is to choose a matching alternative, was used to test the hypothesis. The results virtually supported the hypothesis. In addition, interference was closely related to the patient's control of impulsiveness. It was suggested that schizophrenics have generation (or translation) deficits between different codes.

The effects of interference tasks on recency in the free recall of action events.

Lists of verbal instructions were read aloud and each was enacted either by the subject (SPTs) or by the experimenter (EPTs). In Experiment 1 free recall was made of lists of SPTs and EPTs either immediately after presentation, after an empty 20-s delay interval, or after a 20-s delay interval filled with backward counting. The recall of recency items was unaffected by the empty delay interval, but was somewhat reduced by the counting task. In Experiment 2 free recall was made of lists of SPTs and EPTs either immediately after presentation or after a delay that was filled with a single SPT or a single EPT, 20 s in length. The recency effect evident in the immediate-recall condition was virtually wiped out in the delay conditions, irrespective of whether the delay task matched those in the free-recall list or not. These results are discussed in terms of the mnemonic similarity of the two types of action event.

Visual half-field superiority for righthanders with familial sinistrality: sex differences and cognitive/motor interference in a lexical decision task.

By means of a lexical decision task in which words and nonwords were controlled for familiarity, the question whether sex and familial handedness influence right-field superiority for righthanded subjects was investigated. Analyses of unimanual reaction times and response accuracy revealed sex differences and a cognitive-motor interference for the male group. For hit rates the men, reacting with their right hands, showed a right-field superiority for words and a left-field superiority for meaningless syllables, and the men reacting with their left hands showed the reversed asymmetry. Theoretical problems associated with reaction time and hit rate asymmetry as indicators of language lateralisation are discussed.

"Reverse" Stroop effect in the performance of schizophrenics.

The hypothesis was tested that a group of 30 schizophrenic in contrast to a control group of 35 non-schizophrenic patients would demonstrate substantial and significantly more "Reverse" interference in reading incongruent word-color combinations on the Stroop Color-Word Interference Test. Results supported the hypothesis. A "reverse" interference of 19% and of 9% was observed in the groups' performances, respectively. The group performance differences were much larger on both the classical "Stroop" and "Reverse" interference tasks than on corresponding non-interference tasks. But these interactions were not statistically significant. Measures of absolute and proportional performance decrements on the interference tasks showed no correlations between "Stroop" and "Reverse" interference. Issues discussed included impaired selective attention in schizophrenics' performance, the unexpected high "Reverse" effect in control data and the psychodiagnostic applications of reverse interference.

Memory for verbal and spatial information as a function of age.

The present study investigated whether there is a differential decline with age in verbal and spatial memory, by measuring the ability of 24 young (mean age = 18.8) and 24 elderly (mean age = 69.5) subjects to remember verbal and spatial information under identical task conditions. Subjects recalled either the identities or spatial locations of seven letters arranged randomly within a 5 x 5 grid. To determine whether subjects actually encoded the verbal and spatial characteristics of the array differently, verbal and spatial interference tasks were administered during the retention interval. Results showed that the memory decrement in the elderly was not greater for the spatial aspects of the stimulus array than for its verbal aspects. Thus, there was no evidence for a greater decline with age in spatial memory than in verbal memory. Limited support was found for the utility of the selective interference paradigm to demonstrate separate and independent verbal and spatial memory codes.

Concepts, propositions, and schemata: what are the cognitive units?

In this paper I have reviewed the data and theoretical considerations that bear on the issue of whether propositions and schemata should be considered cognitive units. Assuming a certain general framework about working memory and long-term memory, the evidence tended to point toward a positive conclusion-that both can be cognitive units. Evidence for this comes from observations about all-or-none recall, heightened recall of units, associative priming, diminution of interference effects, considerations of implementation efficiency, and considerations of cognitive naturalness. This being said, I do not find the current picture so convincing that I would want to make a never-say-die commitment to the positive conclusion for cognitive units at all levels of knowledge structures. The idea seems sufficiently promising that it is worthwhile to develop a more explicit theory of what a cognitive unit would be like. So I have proposed a general notion of a cognitive unit that spanned propositions and schemata as special cases and specified the encoding and retrieval properties that such a cognitive unit would have. To be succinct, the important ideas associated with cognitive units are the following: (1) They can occur at multiple levels and enter into hierarchies. (2) If a set of working-memory elements can be put in correspondence with an existing knowledge structure, the elements can be joined in a cognitive unit by a single encoding act. (3) The elements in a cognitive unit are brought into working memory in a single retrieval act. (4) It is possible to evaluate general properties of a cognitive unit without having to expand it into its elements and inspect these. Perhaps this is done by measuring level of activation.

Effects of ambiguous and unambiguous stimulus word differences on popular responses of schizophrenics.

Tested that aspect of response interference theory that predicts that schizophrenics give fewer dominant and more competing responses for ambiguous, but not unambiguous, conditions. It was hypothesized that schizophrenics would evidence in a word association task greater gains, after treatment, in response popularity for ambiguous, but not for unambiguous, stimulus words. The prediction was assessed by administering a specially-constructed wordlist balanced for idiodynamic semantic sets (Moran, 1966). Results, from a pre- and posttest control group design, met predictions for 24 matched pairs of schizophrenics and neurotics: after 5 weeks of treatment, schizophrenics gained significantly in popular responses for ambiguous but not for unambiguous stimulus words, whereas neurotics did not gain significantly for either condition. Positive correlation for schizophrenics between ambiguous word response popularity gains in home and community adjustment as rated by a significant other coincided with expectations from response interference theory (Broen, 1968).