Executive function in body dysmorphic disorder.

BACKGROUND: Body dysmorphic disorder (BDD) is a poorly understood disorder that involves a preoccupation with imagined or minor bodily defects. Only a few studies of neuropsychological function have been conducted. Two previous studies have indicated executive dysfunction in BDD. The current study sought to further define these executive deficits. METHOD: Fourteen DSM-IV BDD patients and 14 age- and sex-matched control participants took part. Because of the high incidence of co-morbidity in BDD, patients with co-morbid Axis I disorders were not excluded. Control participants had no history of psychiatric illness. All participants completed the following executive function (EF) tests: Spatial Span (SS), Spatial Working Memory (SWM) and the Stockings of Cambridge (SOC) task. They also completed the Pattern Recognition (PR) test, a test of visual memory (VM). RESULTS: BDD participants made significantly more between-search errors on the SWM task, an effect that increased with task difficulty. Between-search errors are an example of poor maintenance and manipulation of information. SOC results indicated slower subsequent thinking times (i.e. the time taken to plan) in BDD participants. There were no group differences in SS or PR scores. The severity of BDD, depressive or anxiety symptoms was not correlated with performance on any of the cognitive tasks. CONCLUSIONS: The results of this study indicate that BDD patients have EF deficits in on-line manipulation, planning and organization of information. By contrast, spatial memory capacity, motor speed and visual memory were intact. Considered with evidence from lesion and neuroimaging studies, these results suggest frontal lobe dysfunction in BDD.

Identification of four highly conserved genes between breakpoint hotspots BP1 and BP2 of the Prader-Willi/Angelman syndromes deletion region that have undergone evolutionary transposition mediated by flanking duplicons.

Prader-Willi and Angelman syndromes (PWS and AS) typically result from an approximately 4-Mb deletion of human chromosome 15q11-q13, with clustered breakpoints (BP) at either of two proximal sites (BP1 and BP2) and one distal site (BP3). HERC2 and other duplicons map to these BP regions, with the 2-Mb PWS/AS imprinted domain just distal of BP2. Previously, the presence of genes and their imprinted status have not been examined between BP1 and BP2. Here, we identify two known (CYFIP1 and GCP5) and two novel (NIPA1 and NIPA2) genes in this region in human and their orthologs in mouse chromosome 7C. These genes are expressed from a broad range of tissues and are nonimprinted, as they are expressed in cells derived from normal individuals, patients with PWS or AS, and the corresponding mouse models. However, replication-timing studies in the mouse reveal that they are located in a genomic domain showing asynchronous replication, a feature typically ascribed to monoallelically expressed loci. The novel genes NIPA1 and NIPA2 each encode putative polypeptides with nine transmembrane domains, suggesting function as receptors or as transporters. Phylogenetic analyses show that NIPA1 and NIPA2 are highly conserved in vertebrate species, with ancestral members in invertebrates and plants. Intriguingly, evolutionary studies show conservation of the four-gene cassette between BP1 and BP2 in human, including NIPA1/2, CYFIP1, and GCP5, and proximity to the Herc2 gene in both mouse and Fugu. These observations support a model in which duplications of the HERC2 gene at BP3 in primates first flanked the four-gene cassette, with subsequent transposition of these four unique genes by a HERC2 duplicon-mediated process to form the BP1-BP2 region. Duplicons therefore appear to mediate genomic fluidity in both disease and evolutionary processes.

Attentional processing of colour and location cues.

The aim of the present experiment was to investigate attentional processing of colour and location cues using a detection task. Subjects were required to respond to cued corners of a line drawing of a three-dimensional cube. Both cue and target were highlighted in red or green in one corner of the cube. Cues could be valid or invalid with respect to both the colour and location of subsequent targets. Results indicated a significant main effect of location validity, but no main effect of colour validity. Results also indicated that significant colour cueing effects were evident when location cues were invalid. These data also suggested different time courses for the processing of location and colour information. Location validity effects were largest at the shortest interstimulus interval (ISI) and decreased slightly with increasing ISI. In contrast, colour validity effects were absent at the shortest ISI, but thereafter increased with increasing ISI. The results of this experiment indicate that colour cues can be effective even in an inherently spatial task, provided there is sufficient time for the processing of colour information.

Modulation of reach-to-grasp parameters: semantic category, volumetric properties and distractor interference?

In the two experiments of this study, we assessed the influence of target size and semantic category on the expression of reach-to-grasp kinematic parameters. Moreover, we investigated the influence of size and semantic category of distractors on reaches to the target. The experimental objects represented living and non-living categories and wide and narrow grasp sizes. Participants reached for and picked up mid-sagittally placed targets, which were either alone or flanked by distractors congruent or incongruent to semantic category and size of the target. In experiment 1, movement duration was faster to living objects. We could not replicate this, however, in experiment 2. Conversely, significant and reliable Category x Size interactions for grasp were obtained in experiment 1 and replicated in experiment 2. The pattern of the means in these interactions coincided with the absolute volumetric properties of the stimuli, indicating that the size of the stimuli was the main determinant of the expression of kinematic parameters. We conclude that volumetric properties such as size, rather than semantic category, are the crucial features in the programming and execution of movement to targets. As regards the category and size of the distractor, interference effects were evident: both category and size exerted a comparable influence on reaches to the target. The direction of interference, however, was not systematic. The interference effects are discussed in the context of visual search models of attention.

Interference from distractors in reach-to-grasp movements.

Descriptions of interference effects from non-relevant stimuli are extensive in visual target detection and identification paradigms. To explore the influence of features of non-relevant objects on reach-to-grasp movements, we instructed healthy normal controls to reach for and pick up a cylinder (target) placed midsagittally 30 cm from the starting position of the hand. In Experiment 1, the target was presented alone, or accompanied by a narrower, wider, or same-size distractor positioned to the left or right of the target. In Experiment 2, the target was presented alone or accompanied by a distractor, which was slanted at a different orientation to the target. Reflective markers were placed on the wrist, thumb, and index finger of the right hand, and infra-red light-detecting cameras recorded their displacement through a calibrated 3-dimensional working space. Kinematic parameters were derived and analysed. Consistent changes in the expression of peak velocity, acceleration, and deceleration were evident when the distractor was narrower or wider than the target. The impact of the orientation of the distractor, conversely, was not marked. We discuss the results in the context of physiological findings and models of selective attention.

Ventilatory instability during sleep onset in individuals with high peripheral chemosensitivity.

Previous work has shown that the magnitude of state-related ventilatory fluctuations is amplified over the sleep-onset period and that this amplification is partly due to peripheral chemoreceptor activity, because it is reduced by hyperoxia (J. Dunai, M. Wilkinson, and J. Trinder. J. Appl. Physiol. 81: 2235-2243, 1996). These data also indicated considerable intersubject variability in the magnitude of amplification. A possible source of this variability is individual differences in peripheral chemoreceptor drive (PCD). We tested this hypothesis by measuring state-related ventilatory fluctuations throughout sleep onset under normoxic and hyperoxic conditions in subjects with high and low PCD. Results demonstrated that high-PCD subjects experienced significantly greater amplification of state-related ventilatory fluctuations than did low-PCD subjects. In addition, hyperoxia significantly reduced the amplification effect in high-PCD subjects but had little effect in low-PCD subjects. These results indicate that individuals with high PCD are likely to experience greater sleep-related ventilatory instability and suggest that peripheral chemoreceptor activity can contribute to sleep-disordered breathing.

Modulation of unilateral neglect as a function of direction of object motion.

Unilateral neglect is a disorder involving difficulty in attending to the side of space contralesional to brain injury. Two recent experiments have shown that task-irrelevant background motion reduces neglect on line bisection tasks; however, task-relevant motion has not been assessed. We investigated the effect of task-relevant object motion on left neglect using a moving cube presented on a computer screen. Subjects responded to cued corners of the cube as it moved across the screen. Direction of cube motion had a significant impact on the magnitude of neglect. Responses to left hemispace targets appearing on a leftward moving cube were equal to patients' fastest responses. In contrast, responses to left hemispace targets appearing on a rightward moving cube were the slowest of all responses. These results demonstrate that contralesional object motion is capable of normalising neglect patients' detection of contralesional targets.

Gender differences in airway resistance during sleep.

At the onset of non-rapid-eye-movement (NREM) sleep there is a fall in ventilation and an increase in upper airway resistance (UAR). In healthy men there is a progressive increase in UAR as NREM sleep deepens. This study compared the pattern of change in UAR and ventilation in 14 men and 14 women (aged 18-25 yr) both during sleep onset and over the NREM phase of a sleep cycle (from wakefulness to slow-wave sleep). During sleep onset, fluctuations between electroencephalographic alpha and theta activity were associated with mean alterations in inspiratory minute ventilation and UAR of between 1 and 4.5 l/min and between 0.70 and 5.0 cmH2O . l-1 . s, respectively, with no significant effect of gender on either change (P > 0.05). During NREM sleep, however, the increment in UAR was larger in men than in women (P < 0.01), such that the mean levels of UAR at peak flow reached during slow-wave sleep were approximately 25 and 10 cmH2O . l-1 . s in men and women, respectively. We speculate that the greater increase in UAR in healthy young men may represent a gender-related susceptibility to sleep-disordered breathing that, in conjunction with other predisposing factors, may contribute to the development of obstructive sleep apnea.

Interaction of chemical and state effects on ventilation during sleep onset.

Ventilation varies as a function of state, being higher during wakefulness (as indicated by alpha electroencephalogram activity) than during sleep (theta activity). A recent experiment observed a progressive increase in the magnitude of these state-related fluctuations in ventilation over the sleep-onset period (28). The aim of the present experiment was to test the hypothesis that this effect resulted from chemical (feedback-related) amplification of state effects on ventilation. A hyperoxic condition was used to eliminate peripheral chemoreceptor activity. It was hypothesized that hyperoxia would reduce the amplification of changes in ventilation associated with electroencephalogram state transitions. Ventilation was measured over the sleep-onset period under both hyperoxic and normoxic conditions in 10 young healthy male subjects. Sleep onsets were divided into three phases. Phase 1 corresponded to presleep wakefulness; and phases 2 and 3 corresponded to early and late sleep onset, respectively. The magnitudes of state-related changes in ventilation during phases 2 and 3, and under hyperoxic and normoxic conditions were compared using a phase by condition analysis of variance. Results revealed a significant phase by condition interaction, confirming that hyperoxia reduced the amplification of state-related changes in ventilation by selectively decreasing the magnitude of phase 3 state changes in ventilation. However, some degree of amplification was evident during hyperoxia, thus the results demonstrated that peripheral chemoreceptor activity contributed to the amplification of state-related changes in ventilation but that additional factors may also be involved.