Routes to action in reaction time tasks.
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Choice Behavior↗
Biomedical subjects
C D Frith
Publications and source records attributed to C D Frith.
Reducing persistent auditory hallucinations by wearing an ear-plug.
A case study is presented of the effects of wearing an ear-plug in a single patient with persistent auditory hallucinations. Beneficial effects were detected when the plug was in the dominant ear only.
Adult↗
Impairments in the learning and performance of a new manual skill in patients with Parkinson's disease.
Twelve patients with Parkinson's disease learned two novel skills in which they had to track a target by moving a joystick. In task 1 they had to learn to anticipate the movements of a semi predictable target. In task 2 they had to learn a novel control system in which the movements of the joystick were mirror reversed in relation to the computer screen. On each task they performed two sessions of three minutes continuous practice separated by a 10 minute rest. In both tasks the patients performed much worse than the controls, but showed clear evidence of learning, particularly after the ten minute rest. Detailed examination of their performance suggested that the skill was becoming automatic, releasing attention for aspects of the task that could not be learned. The major difference from the controls appeared during the first minute of each practice session when the controls showed a marked improvement in performance while the patients did not. We suggest that this rapid but temporary improvement in performance reflects the acquisition of a motor "set" whereby existing motor programs or skills are modified to suit the task currently in hand. We concluded that patients with Parkinson's disease have difficulty in maintaining such sets.
Adaptation, Psychological↗
Selective impairment of paired associate learning after administration of a centrally-acting adrenergic agonist (clonidine).
Eight normal volunteers had IV infusions of 200 micrograms clonidine (a centrally-acting adrenergic agonist which reduces noradrenaline release), and saline in a "double-blind" cross-over design. Clonidine reduced subjective estimates of arousal but did not affect performance on the Digit Symbol Substitution Test. Clonidine impaired paired-associate learning, but it did not affect performance on a number of measures of short and long term memory. The findings suggest either 1) that there is a specific (adrenergic) mechanism involved in the acquisition of novel associations, but not in other types of learning, or 2) that paired associate learning is more vulnerable than other learning tasks to disruption of adrenergic transmission.
Adrenergic Fibers↗
Lateral ventricular size in schizophrenia: relationship to the disease process and its clinical manifestations.
Using computed tomography, lateral ventricular size was studied in a sample of 112 institutionalized chronic schizophrenic patients (selected from 510 cases to investigate the correlates of the defect state and intellectual decline and the effects of insulin, electroconvulsive and neuroleptic treatment), and compared with matched groups of non-institutionalized schizophrenics, patients with first schizophrenic episodes, institutionalized and non-institutionalized patients with primary affective disorder, and neurotic out-patients. Age was significantly correlated (P less than 0.0002) with lateral ventricular size, but the institutionalized schizophrenic patients had significantly larger (P less than 0.025) lateral ventricles than the neurotics when age was taken into account. Ventricular enlargement was unrelated to past physical treatment (neuroleptics, insulin coma and electroconvulsive therapy). Within the group of institutionalized schizophrenic patients few correlates of ventricular enlargement were identified; thus in this population increased ventricular size was not clearly associated with the features of the defect state (negative symptoms and intellectual impairment). However, there was a curvilinear (inverted-U) relationship between intellectual function and ventricular size. Increased ventricular size was significantly related to absence of hallucinations, impairment of social behaviour, inactivity and the presence of abnormal involuntary movements. The findings confirm that structural brain changes do occur in chronic schizophrenia, but illustrate some of the difficulties in elucidating the clinical significance of ventricular enlargement. Lateral ventricular size is strongly age-related and the distribution in chronic schizophrenia is skewed and not bimodal; the relationship to particular features of the disease is complex and likely to emerge only in studies with a large sample size.
Adult↗
Institutionalisation and the outcome of functional psychoses.
The outcome in patients receiving long-term in-patient care for manic-depressive psychosis was compared with that in long-stay schizophrenic in-patients and discharged schizophrenic patients. The manic-depressive and schizophrenic in-patients differed in terms of positive and negative features and in the pattern of behaviour, but were equally cognitively impaired. The pattern of behaviour in both schizophrenic groups was the same. The results offer some support for the use of outcome as a validating criterion for the diagnosis of schizophrenia.
Aged↗
The effect of context during word perception in schizophrenic patients.
Hospitalized chronic and acute schizophrenics were compared with age- and social-status-matched controls on word perception tests to measure the effect of context on recognition thresholds. In Experiment 1 the method of J. Morton (1964, British Journal of Psychology, 55, 165-180) was adopted to see how related and unrelated contexts influenced word recognition thresholds when both context and stimulus word were presented visually. Experiment 2 was an auditory analog of Experiment 1 and in addition the chronic schizophrenics were selected on the basis of a presence or absence of auditory hallucinations. The influence of context on perceptual thresholds was quite normal in all schizophrenics. However, analysis of the incorrect responses elicited showed that some schizophrenic subjects do produce bizarre or irrelevant responses or perseveration to a greater extent than their controls. These results are explained in terms of automatic and strategic modes of information processing. The automatic processes responsible for the adjustment of perceptual thresholds operate normally in schizophrenics but response production which demands strategic selection and editing of responses is prone to malfunction which results in the observed deviations in the normal use of language.
Adult↗
The effects of intravenous diazepam and hyoscine upon recognition memory.
Diazepam and hyoscine are known to have amnesic effects when administered intravenously. Nevertheless, they achieve these effects by entirely different neurochemical mechanisms, and so the question arises whether they can be differentiated in terms of their effects upon different categories of encoding operations. Sixteen normal volunteers received intravenous administrations of diazepam, hyoscine, and saline following a double-blind procedure. Both drugs completely eliminated the subjects' ability to discriminate between successive lists of words in a test of recognition memory. Moreover, both drugs also impaired the subjects' ability to reject homophones or synonyms of presented words. Thus, both diazepam and hyoscine appeared to impair the use of list tags, phonemic coding, and semantic coding in storing individual stimulus items in long-term memory.
Adult↗
Schizophrenia, memory, and anticholinergic drugs.
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Humans↗
The effects of intravenous diazepam and hyoscine upon human memory.
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Adult↗
Initiation and execution of predictable and unpredictable movements in Parkinson's disease.
Nine patients with Parkinson's disease were compared with aged-matched normal controls on a tracking and a reaction time task. In the tracking task, subjects had to follow a target moving either predictably or unpredictably at various frequencies. There were no differences between the groups on this task. Both groups were able to use the predictable target movements to eliminate the lag between the target movements and their own movements, indicating that they could emit preprogrammed responses which did not depend on visual feedback. The reaction time task also contrasted predictable and unpredictable movements since the subjects were sometimes told in advance which finger they would have to lift in response to the imperative signal. The patients were significantly less able than controls to use this predictability to reduce their reaction times. It is concluded that parkinsonian patients can use prior information to control the form of a preprogrammed movement, but cannot use this information to help initiate such a movement.
Adult↗
The skin conductance orienting response as an index of attention.
In Experiment I 41 subjects performed one of three tasks while also hearing irrelevant tones tones. The three tasks were forewarned reaction time, vigilance and mental arithmetic and each was divided into discrete trials. The irrelevant tones either occurred during task performance (i.e., within a trial) or outside task performance (i.e., between trials). There was no difference in skin conductance OR magnitude to tones across the three tasks. Heart rate changes in contrast showed clear differences between tasks with a marked deceleration occurring during forewarned reaction time and a marked acceleration occurring during mental arithmetic. Skin conductance OR magnitude was significantly greater to tones occurring during task performance than to tones occurring outside task performance. This was interpreted as reflecting changes in the level of attention (higher during task performance) rather than direction of attention (away from tones during task performance). In Experiment II 39 subjects heard a series of irrelevant tones either while performing a forewarned reaction time task as in Experiment I or while performing no concomitant task. Rate of habituation was significantly faster for the subjects performing the concomitant task. This was interpreted as reflecting direction of attention which should be away from the tones when the subject was performing a concomitant task. Thus while rate of habituation to a class of stimuli may reflect direction of attention, short-term changes in OR amplitude probably reflect level of attention.
Acoustic Stimulation↗
Adverse effects of anticholinergic medication on positive schizophrenic symptoms.
In a series of 36 patients with acute schizophrenia flupenthixol dosage was blindly adjusted to give a fixed level of sedation. Patients were than randomly allocated to procyclidine or placebo. The patients receiving procyclidine experienced more positive schizophrenic symptoms and less severe extrapyramidal features by comparison with placebo patients. Blood levels of prolactin and flupenthixol estimated by radioimmunoassay were not significantly changed by the addition of procyclidine. Flupenthixol dosage and levels and prolactin levels were significantly related. There was no significant association between clinical and laboratory measures, with the exception that a curvilinear (inverted U) relationship was demonstrated between flupenthixol levels and antipsychotic and extrapyramidal effects. This relationship may be due to the fact that, in a study of this design, patients resistant to the effects of neuroleptic medication are likely to be given the highest doses. The findings support earlier claims that anticholinergic medication has adverse effects on schizophrenic symptoms.
Adult↗
Stereotyped responding by schizophrenic patients on a two-choice guessing task.
On each of a sequence of trials subjects had to guess whether a cross would appear on the left or the right side of a computer screen. The sequence of cross positions was random. Normal controls, manic-depressive patients and patients with senile dementia produced relatively random sequences of responses, as did acute schizophrenic patients with positive symptoms. Acute schizophrenic patients with negative symptoms and chronic patients produced more stereotyped sequences with many response alternations (LRLR). Chronic schizophrenic patients with negative symptoms and intellectual deterioration (defect state) produced very stereotyped sequences with many preservations (LLLL). This severe restriction of response sequences is similar to that shown by animals after treatment with amphetamine. It is suggested that it is due to an impairment of a higher order control process which normally inhibits the repetition of sequences of behaviour when these have proved inappropriate.
Adolescent↗
Integration of schematic faces and other complex objects in schizophrenia.
Twenty-one acute schizophrenic patients and 26 neurotic patients sorted each of six sets of 15 objects into three groups. A set consisted either of schematic faces, nonsense objects, or histoforms, each composed of five independently varying features. For the faces and nonsense objects these features could be integrated into a whole, whereas for the histoforms they could not. The distribution of four of the features was such that a set could be divided into three groups. The fifth feature either remained constant and had no effect on sorting performance or it varied randomly and acted as a distractor. Performance was assessed from the variance in common between the grouping actually present in a set and the grouping produced by the subject. For the control patients faces were sorted much better than histoforms if no distractor was present. However, performance with faces was massively impaired by a distractor while performance with histoforms was not. For the schizophrenic patients faces were not sorted better than histoforms and the effect of distraction was similar for every type of material. The performance of the controls suggest that the gestalt quality of the faces dominated over their constituent details. This enabled more features to be handled at once, thus achieving better sorting with faces than histoforms. However, it also made it more difficult for subjects to ignore a distracting component in the faces. The performance of the schizophrenics suggests that for them the integrated gestalt of the face was not dominant over its components.
Attention↗
Stimulus integration in schizophrenia.
Twenty-four chronic institutionalized schizophrenics and 11 acute non-institutionalized schizophrenics were compared with 20 controls (matched for age, sex and socio-economic status) on a task normally eliciting stimulus integration (Garner, 1974). The subjects had to classify the widths of a sequence of rectangles into one of four categories while ignoring their height. Each response was timed. Although all the patients performed the task more slowly than their appropriate control group, the results showed that schizophrenic patients integrated these simple stimuli just as do normal subjects. Thus failure of simple stimulus integration is not a feature of schizophrenia.
Acute Disease↗
Selective retrieval and free emission of category exemplars in schizophrenia.
In a free emission task, normals, chronic schizophrenics with only positive and those with only negative symptoms generated as many exemplars from natural language categories as they could in three minutes. While the overall output level of both schizophrenic groups was lower than that of the normals, neither showed intrusions of unrelated words, and the temporal distribution of the output was marked by a clustering pattern inconsistent with a selective attention deficit hypothesis. The schizophrenics with negative symptoms tended to produce consistently smaller clusters than the normals and the schizophrenics with positive symptoms, implicating a specific retrieval constriction. The relationship of this to the major negative symptom poverty of speech is discussed.
Adult↗
Effects of ECT and depression on various aspects of memory.
Seventy severely depressed patients randomly assigned to receive 8 real or sham ECT were further subdivided on the basis of degree of recovery from depression afterwards. In comparison to a non-depressed control group the depressed patients were impaired on a wide range of tests of memory and concentration prior to treatment, but afterwards performance on most of the tests had improved. Real ECT induced impairments of concentration, short-term memory and learning, but significantly facilitated access to remote memories. At 6 months follow-up all differences between real and sham ECT groups had disappeared. On the majority of tests the previously depressed patients now performed at the same level as the control group. There was some evidence that a subgroup of treatment-resistant patients (poor outcome after real ECT) were significantly more likely to complain of memory problems 6 months later.
Adult↗