Learning and altering behaviours by reinforcement: neurocognitive differences between children and adults.

This study examined neurocognitive differences between children and adults in the ability to learn and adapt simple stimulus-response associations through feedback. Fourteen typically developing children (mean age=10.2) and 15 healthy adults (mean age=25.5) completed a simple task in which they learned to associate visually presented stimuli with manual responses based on performance feedback (acquisition phase), and then reversed and re-learned those associations following an unexpected change in reinforcement contingencies (reversal phase). Electrophysiological activity was recorded throughout task performance. We found no group differences in learning-related changes in performance (reaction time, accuracy) or in the amplitude of event-related potentials (ERPs) associated with stimulus processing (P3 ERP) or feedback processing (feedback-related negativity; FRN) during the acquisition phase. However, children's performance was significantly more disrupted by the reversal than adults and FRN amplitudes were significantly modulated by the reversal phase in children but not adults. These findings indicate that children have specific difficulties with reinforcement learning when acquired behaviours must be altered. This may be caused by the added demands on immature executive functioning, specifically response monitoring, created by the requirement to reverse the associations, or a developmental difference in the way in which children and adults approach reinforcement learning.

Inefficient cerebral recruitment as a vulnerability marker for schizophrenia.

BACKGROUND: Patients with schizophrenia and their first-degree relatives exhibit both abnormally diminished and increased neural activation during cognitive tasks. In particular, excessive task-related activity is often observed when tasks are easy, suggesting that inefficient cerebral recruitment may be a marker of vulnerability for schizophrenia. This hypothesis might best be tested using a very easy task, thus avoiding confounding by individual differences in task difficulty. METHOD: Eighteen people with schizophrenia, 18 unaffected full siblings of patients with schizophrenia and 26 healthy controls performed an easy auditory target-detection task in a 3-T magnetic resonance imaging (MRI) scanner. Groups were matched for accuracy on the task. Blood oxygen level-dependent (BOLD) responses to non-target stimuli in participants with vulnerability for schizophrenia (siblings and patients) were compared with those of healthy controls, and those of patients with those of unaffected siblings. BOLD responses to targets were compared with baseline, across groups. RESULTS: Subjects with vulnerability for schizophrenia showed significant hyperactivation to non-targets in brain areas activated by targets in all groups, in addition to reduced deactivation to non-targets in areas suppressed by targets in all groups. Siblings showed greater activation than patients to non-targets in the medial frontal cortex. Patients exhibited significantly longer reaction times (RTs) than unaffected siblings and healthy controls. CONCLUSIONS: Inefficient cerebral recruitment is a vulnerability marker for schizophrenia, marked by reduced suppression of brain areas normally deactivated in response to task stimuli, and increased activation of areas normally activated in response to task stimuli. Moreover, siblings show additional activation in the medial frontal cortex that may be protective.

Autistic spectrum disorder traits in children with attention deficit hyperactivity disorder.

BACKGROUND: Current classification systems do not allow for comorbid diagnoses of attention deficit hyperactivity disorder (ADHD) and autistic spectrum disorder (ASD). Children with ADHD are often screened for ASD during clinical assessment and when recruited to clinical trials. We predicted that children with ADHD would have more autistic traits than controls and that certain traits would be more prevalent. METHODS: The clinically referred sample consisted of 30 children with ADHD and 30 matched controls aged 9-15 years. Children were screened for ASD traits using the Social Aptitudes Scale (SAS) and the Social Communication Questionnaire (SCQ). RESULTS: We found that ASD traits were significantly higher in children with ADHD than controls. None of the children received a diagnosis of autism or ASD. However, a large proportion (28% using the SCQ and 62% using the SAS) of children with ADHD reached screening thresholds for a predictive diagnosis of ASD. Relative to controls, children with ADHD had significantly higher levels of communication and social deficits, but not repetitive behaviours. CONCLUSION: Further work is needed to establish whether autistic-like communication and social difficulties in children with ADHD are part of the broader ASD phenotype or are specific to ADHD.

Symptoms of post-concussional syndrome are non-specifically related to mild traumatic brain injury in UK Armed Forces personnel on return from deployment in Iraq: an analysis of self-reported data.

BACKGROUND: Mild traumatic brain injury (mTBI) is being claimed as the 'signature' injury of the Iraq war, and is believed to be the cause of long-term symptomatic ill health (post-concussional syndrome; PCS) in an unknown proportion of military personnel. METHOD: We analysed cross-sectional data from a large, randomly selected cohort of UK military personnel deployed to Iraq (n=5869). Two markers of PCS were generated: 'PCS symptoms' (indicating the presence of mTBI-related symptoms: none, 1-2, 3+) and 'PCS symptom severity' (indicating the presence of mTBI-related symptoms at either a moderate or severe level of severity: none, 1-2, 3+). RESULTS: PCS symptoms and PCS symptom severity were associated with self-reported exposure to blast whilst in a combat zone. However, the same symptoms were also associated with other in-theatre exposures such as potential exposure to depleted uranium and aiding the wounded. Strong associations were apparent between having PCS symptoms and other health outcomes, in particular being a post-traumatic stress disorder or General Health Questionnaire case. CONCLUSIONS: PCS symptoms are common and some are related to exposures such as blast injury. However, this association is not specific, and the same symptom complex is also related to numerous other risk factors and exposures. Post-deployment screening for PCS and/or mTBI in the absence of contemporaneous recording of exposure is likely to be fraught with hazards.

Cognitive deficits in early-onset schizophrenia spectrum patients and their non-psychotic siblings: a comparison with ADHD.

BACKGROUND: Previous research has shown cognitive deficits in patients with schizophrenia spectrum disorders in the areas of executive function, verbal memory and attention. Subtle deficits have been shown in healthy first-degree relatives of patients, suggesting that they may be trait markers. The specificity of these markers for schizophrenia compared with another neurodevelopmental disorder, Attention Deficit Hyperactivity Disorder (ADHD) has not been reliably established. METHODS: The Rey Auditory Verbal Learning Test (RAVLT), Hayling Sentence Completion Test (HSCT), FAS Test of orthographic verbal fluency (FAS) and Continuous Performance Test-Identical Pairs (CPT-IP) were administered to adolescent schizophrenia spectrum patients (SZ; n=30), adolescent siblings of schizophrenia spectrum patients (SZ-SIB; n=36), healthy control participants (HC; n=72); a neurodevelopmental comparison group of adolescents with ADHD (n=27). RESULTS: The SZ group were impaired on all measures. The SZ-SIB group were impaired on IQ, immediate recall (RAVLT), target sensitivity (CPT-IP), response initiation (HSCT); error rates for the FAS and HSCT. There were no significant differences between the SZ-SIB and ADHD groups on individual measures of cognitive function. Principal Components Analysis revealed four factors on which further analyses were conducted. The SZ-SIB and ADHD groups showed different profiles of impairment on components related to response initiation and sustained attention/vigilance when each was compared with the HC group. CONCLUSIONS: Deficits in intellectual function, verbal memory and response initiation/inhibition were found in the SZ-SIB group indicating that these are markers of risk for schizophrenia. Subtle differences in profiles of impairment in the SZ-SIB and ADHD groups on composite measures of attention and response initiation require further investigation.

Task and postural factors are related to back pain in helicopter pilots.

BACKGROUND: A previous survey by Shear et al. revealed a high prevalence of back pain in Royal Navy helicopter aircrew, compared with controls. It was recommended that a second survey be undertaken, taking account of flying tasks and cockpit ergonomics. This was the purpose of the present investigation. METHOD: A questionnaire containing items on back pain and posture was circulated to all 246 acting pilots, with returns of 75%. The questionnaire sought information on pain in both the flying pilot and co-pilot/instructor roles. RESULTS: The 12-mo prevalence of back pain was 80%. Task-related back pain was greatest in instrument flying (72%) and least in the co-pilot and instructor roles (24%). Self-ratings of posture indicated that forward flexed trunk postures predominated in the flying roles and were most extreme in instrument flying. In non-flying roles, symmetrical, reclining postures were more often reported. No demographic or psychosocial variables were significantly related to back pain prevalence or disability. CONCLUSIONS: Much of the back pain experienced by helicopter pilots appears to be due to the posture needed to operate the cyclic and collective controls. In instrument flying, it is suggested that the visual demands of scanning the displays may exacerbate the pain by causing the pilot to lean further forward.

Optic tract syndrome secondary to metastatic breast cancer.

PURPOSE: To report a patient who was initially examined with optic tract syndrome caused by a focal metastasis to the lateral geniculate body and optic tract. METHOD: Case report. RESULTS: A 44-year-old woman with metastatic breast cancer was initially examined with normal central visual acuity, afferent pupillary defect, homonymous hemianopia, and optic atrophy. CONCLUSION: This case demonstrates that an isolated optic tract syndrome may occur as a result of metastatic lesions to the lateral geniculate body and optic tract.

Allee effects limit population viability of an annual plant.

Allee effects may be experienced by plants when populations are too small or isolated to receive sufficient pollinator services to replace themselves. This article reports experimental data from an annual herb, Clarkia concinna, documenting that small patches suffered reproductive failure due to lack of effective pollination when critical thresholds of isolation were exceeded. In contrast, sufficiently large patches attracted pollinators regardless of their degree of isolation. These data accord with data on patch extinctions showing that small and isolated patches have a higher extinction rate than do large patches and with observations showing chronically low reproductive success in such patches prior to extinction. While not conclusively demonstrating that Allee effects cause extinction in small and isolated patches, the data are suggestive. Although threshold effects have been postulated in several mathematical models of population viability, this is the first report of data from natural populations that display the occurrence of such thresholds. These results have implications for the management of endangered plants, which often are restricted to isolated, small populations, as well as suggesting a potential limit to spatial spread in plant populations dependent on animal vectors for reproduction.

Optic neuropathy in familial dysautonomia.

Optic atrophy, which is indicative of a CNS disorder, is a rarely described manifestation of familial dysautonomia (Riley-Day syndrome). As these patients are now living longer, the prevalence of optic neuropathy also may be increasing. We present a man with familial dysautonomia and visual loss resulting from optic atrophy and visual field defect suggestive of chiasmal pathology.

The chorioallantoic membrane in irritation testing.

The chorioallantoic membrane (CAM) of the chick embryo is a fusion membrane with a blood vessel complex. It was examined as a possible means of predicting the irritant potential of chemicals for the conjunctiva, as observed in the Draize eye test. Nine chemicals of known irritancy potential for the eye in vivo were selected from published data, and each was tested at four different concentrations. The treated CAMs were examined macroscopically at 4, 24 and 48 hr after treatment, and were then prepared for histological examination. A dose response was observed for each chemical. In only four of the nine chemicals could the response in the CAM be considered to predict the in vivo activity. In another two, the correlation was poor. Three chemicals, glycerine, polyethylene glycol and Tween 80, all reported to be harmless to the eye, were embryotoxic at more than one concentration. Histological changes were degeneration or necrosis at the treated site without the chemical features of heterophil (chicken neutrophil) infiltration or significant macrophage infiltration. It is concluded that the CAM is not a suitable tissue for predicting in vivo irritant potential of substances for the conjunctiva, and that it provides no more information than could be obtained from cell cultures.

The effect and mode of action of zinc pyrithione on cell growth. II. In vivo studies.

The effect of topical application of the anti-dandruff agent zinc pyrithione (ZnPTO) on epidermal DNA synthesis in normal and hexadecane-stimulated rat skin was investigated. Autoradiography was used to determine the percentage of epidermal cells labelled with [3H]thymidine (labelling index). ZnPTO at 1% in shampoo base caused a slight increase in the labelling index in normal skin, similar to the effect of the shampoo base alone. No effect of 1% ZnPTO as an aqueous dispersion was observed. ZnPTO at 1% in shampoo base did not reduce the large increase in labelling index produced by hexadecane, nor did shampoo base alone or 1% ZnPTO in water. The shampoo base with or without 1% ZnPTO had only a very slight effect on the histopathology of normal and hexadecane-treated skin, and 1% ZnPTO in water had no effect. It is concluded that the in vitro potential of ZnPTO to cause growth inhibition is not achieved in vivo, presumably because of low percutaneous absorption. This evidence does not support a cytostatic mode of action in clearing dandruff.

The conformation of fibrinogen and fibrin: an electron microscopy study.

A mica adsorption technique was used to prepare fibrinogen and early fibrin polymers for examination in the transmission electron microscope. Globular particles 10 +/- 3 nm in diameter were observed and a model for the process of aggregation of these globules into fibrous units is proposed. A comparison is made between the results obtained by the mica adsorption technique and those obtained by conventional preparation techniques involving fixation and staining.