Cognitive and psychological correlates of smoking abstinence, and predictors of successful cessation.

The neural circuitry implicated in addictive drug use, which appears to be down-regulated in early abstinence, corresponds closely with brain reward pathways. A literature review suggests that responses to incentive stimuli and the ability to inhibit reflexive responses, both of which have been associated with normal functioning in these pathways, might be weakened during acute abstinence from chronic drug use. In an ongoing study, 82 smokers, abstinent overnight before two separate testing occasions, have been assessed after administration of nicotine and placebo lozenges (order of sessions counterbalanced). Nicotine administration is associated with a significant reduction in anhedonia, a near-significant increase in response to financial incentive, enhanced ability to inhibit reflexive eye movements, and increased attentional bias to words with appetitive significance. Fifty-nine participants then initiated a quit attempt and 19 reported relapsing within 7 days. Comparing their performance in the two prequit lozenge assessment sessions, relapsers showed a stronger effect of nicotine on enhancing their ability to inhibit reflexive eye movements and a near-significant trend towards greater nicotine-induced increases in attentional bias toward appetitive words.

A model for environmental sex reversal in fish.

A mathematical model is presented which combines genetic XX-female/XY-male sex determination with environmental pressure for phenotypic sex reversal. This may occur when fishes are exposed to endocrine disrupters, specifically masculinization by exposure to androgens and feminization by exposure to estrogens. A generic model is derived for the sex ratio in successive generations and three special cases, with chronic and constant pressure to sex reverse, are discussed in detail. These show that, with extreme environmental pressure to masculinize, the male genotype is at risk of dying out but with less extreme pressure, masculinization will not be detectable since the proportion of phenotypic males becomes one-half. With feminization at any pressure to sex reverse, the male and female genotypes will be maintained in a stable sex ratio in which the proportion of genotypic males exceeds one-half and is close to one-half if YY offspring (eggs) are not viable. In converse, the model is also applicable to the genetic ZZ-male/ZW-female system of sex determination in fish. At present suitable data are not available with which to validate the model, but proposals are made for relevant experimental studies.

The effect of amphetamine on Kamin blocking and overshadowing.

Schizophrenic patients show deficits on stimulus salience tasks such as latent inhibition and blocking, which measure the ability to disregard irrelevant stimuli. Amphetamine-treated animals show similar deficits in analogous tasks, thereby providing a model of the stimulus-selection deficits observed in schizophrenia. In two experiments, the effect of the indirect dopamine (DA) agonist D-amphetamine sulphate (1.0 mg/kg, i.p.) on Kamin blocking and overshadowing were examined and compared, in the rat, using the conditioned lick suppression procedure. The aim was to provide some insight into the behavioural and pharmacological mechanisms underlying amphetamine effects in both paradigms. In experiment 1, it was shown that amphetamine selectively disrupted Kamin blocking, when given either at stage 2 alone, or at both stages of the task. In experiment 2, amphetamine treatment significantly abolished Kamin blocking and overshadowing, when administered prior to compound conditioning in both tasks. These data suggest that dopamine may play a critical role in mediating performance in tasks measuring stimulus salience processes. The results are discussed in the framework of the role of DA in stimulus-selection performance.

Distractor cueing effects on choice reaction time and their relationship with schizotypal personality.

BACKGROUND AND OBJECTIVES: Although usually displaying increased distractibility, schizophrenic patients sometimes show a reduced influence of distractors during selective attention tasks. This study explored whether reduced distractor processing effects can also occur in healthy individuals with high levels of schizotypal personality traits. DESIGN AND METHOD: In all, 36 healthy volunteers completed schizotypal personality scales and a choice reaction time (RT) task in which they responded to the central letter of triads (XMX, YCY), ignoring the flanking distractors. RT increases on low-probability probe trials (YMY, XCX) measured distractor processing ('the distractor cueing effect'). Correlations between schizotypy scores and distractor cueing were evaluated. RESULTS: Healthy participants with high positive schizotypy scores (i.e. those reporting more hallucination-like experiences and delusion-like beliefs) showed smaller distractor cueing effects than those with lower scores. This association was independent of the influence of other schizotypal personality traits (disorganized, negative or asocial schizotypy) and was significant only for right-hand responses. These findings closely parallel the previously reported reduced distractor cueing effect, for right-hand responses, among acute-phase schizophrenic patients. CONCLUSION: Finding reduced distractor cueing effects in healthy participants with high levels of positive schizotypy increases confidence that reduced distractor cueing is a specific feature, rather than a non-specific consequence, of acute-phase schizophrenia.

Do women get posttraumatic stress disorder as a result of childbirth? A prospective study of incidence.

BACKGROUND: Recent research suggests that a proportion of women may develop posttraumatic stress disorder after birth. Research has not yet addressed the possibility that postpartum symptoms could be a continuation of the disorder in pregnancy. This study aimed to test the idea that some women develop posttraumatic stress disorder as a result of childbirth, and to provide an estimate of the incidence using a prospective design, which controls for the disorder in pregnancy. METHOD: This prospective study assessed 289 women at three time points: 36 weeks gestation and 6 weeks and 6 months postpartum. The prevalence of posttraumatic stress disorder was assessed by questionnaire at each time point, and the incidence was examined after removing women who had severe symptoms of posttraumatic stress disorder or clinical depression in pregnancy. RESULTS: After removing women at the first time point, 2.8 percent of women fulfilled criteria for the disorder at 6 weeks postpartum and this decreased to 1.5 percent at 6 months postpartum. CONCLUSIONS: The results suggest that at least 1.5 percent of women may develop chronic posttraumatic stress disorder as a result of childbirth. It is important to increase awareness about the disorder and to give health professionals access to simple screening tools. Intervention is possible at several levels, but further research is needed to guide this intervention.

The effect of aerobic training on rehabilitation outcomes after recent severe brain injury: a randomized controlled evaluation.

OBJECTIVE: To examine the impact of fitness training with recently brain-injured inpatients on exercise capacity and functional and psychologic outcome measures. DESIGN: A randomized controlled trial of exercise versus relaxation training for 3 months. Blind assessments were conducted before and after the end of a 12-week training program, as well as at follow-up assessment 12 weeks posttraining. SETTING: Four regional neurologic inpatient rehabilitation units. PATIENTS: Of 157 patients recruited 24 +/- 14 weeks after single-incident brain injury, 142 patients were assessed at week 12, and 128 patients at follow-up. INTERVENTIONS: Patients were randomized between cycle ergometer aerobic training and a relaxation training control condition, which was theoretically inert with respect to cardiovascular fitness. MAIN OUTCOME MEASURES: Validation of exercise training (peak work rate, peak heart rate, body mass index); mobility and physical function (modified Ashworth scale, Berg balance scale, Rivermead Mobility Index, 10-m walk velocity); disability and dependency (Barthel index, FIMtrade mark instrument, Nottingham Extended Activities of Daily Living); and psychologic function (fatigue questionnaire, Hospital Anxiety and Depression Scale). RESULTS: Significant improvements in exercise capacity (p <.05) in the exercise training group (n = 70) relative to the control group (n = 72) were not matched by greater improvements in functional independence, mobility, or psychologic function, at either 12 weeks or follow-up. CONCLUSIONS: The benefits of improved cardiovascular fitness did not appear to extend to measurable change in function or psychologic state.

Personality, punishment, and procedural learning: a test of J.A. Gray's anxiety theory.

Effects of punishment and personality on a phylogenetically old form of knowledge acquisition, procedural learning, were studied to test J. A. Gray's 1970, 1987, 1991) theory of anxiety. Broad measures of personality (extraversion, E.; neuroticism, N; and psychoticism, P) and specific measures of trait anxiety (Anx) and impulsivity (Imp) were taken. Punishment led to response invigoration, reducing reaction time latency, but this was not related to personality. A negative correlation of P and learning was observed in both punishment and control conditions. In support of Gray's theory, high Anx improved learning under punishment (and impaired learning under control), and low Anx improved learning under control (and impaired learning under punishment). These data are contrasted with H.J. Eysenck's (1967) arousal theory of personality. Results point to a new behavioral tool with which researchers can explore further the interaction of reinforcement, arousal, and personality.

New approaches to the study of amnesic patients: what can a neurofunctional philosophy and neural network methods offer?

In this paper I first consider a neurofunctional approach to the study of amnesic patients. This approach stresses the need for theorising about the processing operations of brain regions and circuits rather than for theorising about neuropsychological syndromes. A syndrome such as amnesia-may not exist, in any meaningful sense, if there is marked heterogeneity within the patients grouped together in this way. Powerful neuroimaging techniques may now allow a more useful basis for grouping patients in terms of lesion location rather than aetiology. In turn this will allow an evaluation of the information processing functions subserved by the lesioned structures. The second strand to the present paper stresses the weakness in the specification of current theories. This has made it difficult to select experimental tasks that decisively measure the key components of those theories. The paper makes the case that explicit neural network models are a useful way to try to overcome this problem. In line with these ideas, the paper begins to build a model of how the brain may achieve useful kinds of stimulus representations. Considerations of human behaviour in category learning tasks have emphasised parallel and interacting roles for both exemplar- and element-based stimulus representations. It is suggested that the hippocampus itself may encode exemplar representations, and these may provide a basis for episodic memory as well as some types of category learning. It is further suggested that the ventral striatum may encode the element-based representations. The model allows some new and detailed predictions for the performance of amnesic subjects related to lesion location.

Kamin blocking is not disrupted by amphetamine in human subjects.

The effect of oral amphetamine administration on the Kamin-blocking effect in healthy volunteer subjects was investigated. Against predictions, Kamin blocking was not disrupted by either a high or low oral dose of D-amphetamine under conditions which have, in previous studies, led to disruption of a related learning phenomenon (latent inhibition). This lack of effect of amphetamine administration upon Kamin blocking weakens hypotheses that this cognitive process is mediated by the same changes in dopaminergic activity which affect latent inhibition. Currently, the only data which show strong comparative associations between Kamin blocking and latent inhibition are when they are applied to schizophrenic populations. These results may suggest that Kamin blocking and latent inhibition may be measuring different aspects of schizophrenic cognitive dysfunction.

Use of neural networks in brain SPECT to diagnose Alzheimer's disease.

UNLABELLED: The usefulness of artificial neural networks in the classification of 99mTc-HMPAO SPECT axial brain scans was investigated in a study group of Alzheimer's disease patients and age-matched normal subjects. METHODS: The cortical circumferential profiling (CCP) technique was used to extract information regarding patterns of cortical perfusion. Traditional analysis of the CCP data, taken from slices at the level of the basal ganglia, indicated significant perfusion deficits for Alzheimer's disease patients relative to normals, particularly in the left temporo-parietal and left posterior frontal areas of the cortex. The compressed profiles were then used to train a neural-network classifier, the performance of which was compared with that of a number of more traditional statistical (discriminant function) techniques and that of two expert viewers. RESULTS: The optimal classification performance of the neural network (ROC area = 0.91) was better than that of the alternative statistical techniques (max. ROC area = 0.85) and that of the expert viewers (max. ROC area = 0.79). CONCLUSION: The CCP produces perfusion profiles which are well suited to automated classification methods, particularly those employing neural networks. The technique has the potential for wide application.

Attentional bias in obsessional compulsive disorder.

To date, studies of information processing in anxiety disorders have suggested that the latter are characterised by vigilance for threatening stimuli, possibly specific to personally relevant threat content. The present study represents an attempt to establish whether patients suffering from Obsessional Compulsive Disorder (OCD), generally classified as an anxiety disorder, show a similar cognitive bias. Thus, a replication of MacLeod, Mathews and Tata's (1986) study [Journal of Abnormal Psychology, 95, 15-20] is reported, employing modified materials of direct concern to the OCD subjects i.e. Contamination-related words. The results did indeed reveal content specific vigilance, whereby the OCD group were more vigilant for contamination content than mood-matched High Trait Anxious (HTA) controls, but the reverse was true for Social Anxiety words. Additionally, while a general threat interference effect was identified for both OCD and HTA subjects this was not content specific. A second experiment employing Low Trait Anxious subjects revealed no vigilance for threat nor any threat interference in this sample. The clinical implications and possible mechanism underlying these results are discussed.

Sexual maturity modifies the responsiveness of the pituitary-interrenal axis to stress in male rainbow trout.

A significant reduction in stress-induced plasma cortisol levels is apparent in mature male rainbow trout compared to immature fish of both sexes and of the same age and strain. Mean plasma cortisol levels in groups of immature fish subjected to a standard 1-hr confinement stress were consistently higher (range 93.9 +/- 4.9-114.8 +/- 4.1 ng ml-1) than mean levels in mature males exposed to the same procedure (range 47.0 +/- 4.3-71.7 +/- 5.7 ng ml-1), throughout the 4-month period around spawning (P < 0.001). Body weight was not found to be a significant determinant of poststress cortisol level. The dissimilarity in plasma cortisol levels between mature and immature fish following confinement does not stem from differences in the dynamics of the response; during a 24-hr period of confinement the rate of elevation of plasma cortisol levels was similar for both mature male and immature fish, but mature male fish attained a significantly lower peak cortisol level (51.6 +/- 5.2 ng ml-1) than immature fish (89.5 +/- 7.7 ng ml-1), a disparity which was maintained throughout the period of stress (P < 0.05-P < 0.001). The reduced responsiveness of the interrenal tissue of mature male fish during stress appears to be modulated by the hypothalamus/pituitary. Plasma ACTH levels in mature male trout (44 +/- 9 pg ml-1) are significantly lower than those in immature fish (71 +/- 9 pg ml-1, P < 0.01) within 30 min of the onset of confinement and remain so during a 3-hr period of confinement. These data suggest that the cortisol/ACTH feedback equilibrium has been modified in mature fish to a lower "set point." Furthermore, although stress caused a significant decline of plasma alpha-MSH levels in both immature fish and mature males, N-acetyl-beta-endorphin levels were reduced only in mature male fish during confinement stress.

'Cognitive inhibition' and positive symptomatology in schizotypy.

The negative priming paradigm (Tipper, 1985) was used to investigate the relationship between 'cognitive inhibition' and symptoms of reality distortion in schizotypy, after previous findings that the negative priming effect is reduced in both acute schizophrenics and high schizotypes (Beech, Powell, McWilliam & Claridge, 1989; Beech, Baylis, Smithson & Claridge, 1989). Following Frith's (1979) model, which suggests that the positive symptoms of schizophrenia are due to a failure of the inhibitory processes which normally limit the contents of consciousness, it was predicted that negative priming would be inversely correlated with levels of positive symptomatology, as measured by the CSTQ (Bentall, Claridge & Slade, 1989). The results supported the hypothesis, which confirms the usefulness of a symptom-oriented approach as well as providing some validation for the concept of schizotypy. It was concluded that high schizotypes, similarly to acute schizophrenics, show a reduction in 'cognitive inhibition', as was predicted by Frith's (1979) model.

The effects of confinement stress on circulating prolactin levels in rainbow trout (Oncorhynchus mykiss) in fresh water.

Rainbow trout were confined for 48 hr, during which time water quality either was allowed to deteriorate (resulting in elevated NH3, elevated free CO2, and reduced dissolved O2) or was maintained at preconfinement levels. Fish were removed and blood samples taken at 0, 2, 4, 8, 24, and 48 hr after the onset of confinement from both stressed (confined) and unstressed (unconfined) fish. Plasma cortisol and plasma prolactin (PRL) levels were determined using specific RIAs. Chronic confinement of rainbow trout, accompanied by a decline in water quality, resulted in significant elevation of plasma cortisol, maintained for the period of confinement. Plasma PRL levels were significantly lower in stressed fish, by up to 60% relative to control fish, during the first 24 hr of confinement. The stress of confinement alone, in the absence of deterioration in water quality, produced similar results, with the change in prolactin levels being less rapid but more prolonged under these conditions.

Abolition of latent inhibition by a single 5 mg dose of d-amphetamine in man.

The performance of healthy volunteer subjects on an auditory latent inhibition (LI) paradigm was assessed following administration of a single oral dose of d-amphetamine or placebo. It was predicted that a low (5 mg), but not a high (10 mg), dose of d-amphetamine would disrupt LI. The prediction was supported with left ear presentation of the preexposed stimulus only. When the preexposed stimulus was presented to the right ear the predicted pattern of findings was not obtained. It is concluded that the dopaminergic system is involved in the mediation of LI in man and it is speculated that the interaction between amphetamine dose and ear of presentation of the preexposed stimulus may reflect normally occurring dopaminergic hemisphere asymmetry.

The effect of starvation on growth and plasma growth hormone concentrations of rainbow trout, Oncorhynchus mykiss.

Two experiments, one using 0+ the other 1+ rainbow trout, were conducted to investigate the effect of prolonged starvation on plasma growth hormone levels. The results from both experiments were essentially the same. As expected, starvation resulted in cessation of growth and in a lower coefficient of condition, whereas fed fish continued to grow and remained in good condition. Starvation had relatively little effect on the plasma cortisol level; in one experiment levels were elevated temporarily in starved fish, although by the end of the experiment there was no longer any difference between starved and fed fish, and in the other experiment plasma cortisol levels remained very low throughout the course of the experiment in both starved and fed fish. In contrast, in both experiments starvation had a pronounced effect on the plasma growth hormone level, which rose steadily during both experiments, such that it was six times higher after 1 month of starvation in 0+ fish, and five times higher after 6 weeks of starvation in 1+ fish. Thus, paradoxically, fed fish had very low plasma growth hormone levels and grew rapidly, whereas starved fish had elevated plasma growth hormone levels but did not grow. In both experiments a strong negative correlation was observed between the plasma growth hormone level and the coefficient of condition of the fish. The results are discussed with regard to the well-established metabolic changes that occur during starvation, and it is suggested that a major role of growth hormone during starvation is to aid in the mobilisation of fatty acids and glycerol from adipose stores.

Effects of acute and chronic stress on the levels of circulating growth hormone in the rainbow trout, Oncorhynchus mykiss.

The acute stress of handling followed by confinement for a period of 1 or 24 hr caused a typical stress response in rainbow trout (elevation of plasma ACTH and cortisol) and a significant reduction in the concentration of circulating growth hormone. The chronic stress of low oxygen levels in both crowded and uncrowded tanks of fish caused a significant elevation of circulating GH levels, an effect which was abolished by the provision of additional aeration to the rearing tanks. This chronic elevation of GH levels was closely correlated with an elevation of plasma cortisol in the same fish. These findings are discussed in relation to stress-induced growth suppression and to the links between the hypothalamic-pituitary-interrenal axis and somatotrope activity.

Indirect measures of memory in a duration-judgement task are normal in amnesic patients.

Nine amnesic patients of mixed aetiology were studied in a duration-judgement task that allowed three measures of memory to be obtained. On each trial of the task, subjects attempted to read a briefly flashed word and to estimate the duration of the flash. Both word identification and duration estimation differed as a function of prior study. Words that were previously studied were identified more often and were estimated to have been flashed for a longer duration than were words not previously studied. These priming effects were found in young subjects in Experiment 1 and in amnesic patients and age-matched control subjects in Experiment 2. Priming effects were normal in the amnesic patients, whereas these patients were severely impaired at recognizing the same words. Previous results have also shown that amnesic patients can perform normally on certain memory tests, including priming of word identification. These results show that priming of duration judgements can also be included in the category of indirect measures of memory that are spared in amnesia.