Cognitive performance in irritable bowel syndrome: evidence of a stress-related impairment in visuospatial memory.

BACKGROUND: Central nervous system (CNS) dysfunction is a prominent feature of the functional gastrointestinal (GI) disorder, irritable bowel syndrome (IBS). However, the neurobiological and cognitive consequences of key pathophysiological features of IBS, such as stress-induced changes in hypothalamic-pituitary-adrenal (HPA)-axis functioning, is unknown. Our aim was to determine whether IBS is associated with cognitive impairment, independently of psychiatric co-morbidity, and whether cognitive performance is related to HPA-axis function. METHOD: A cross-sectional sample of 39 patients with IBS, a disease control group of 18 patients with Crohn's disease (CD) in clinical remission and 40 healthy age- and IQ-matched control participants were assessed using the Paired Associates Learning (PAL), Intra-Extra Dimensional Set Shift (IED) and Spatial Working Memory (SWM) tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and a computerized Stroop test. HPA-axis function was determined by measuring the cortisol awakening response (CAR). RESULTS: IBS patients exhibited a subtle visuospatial memory deficit at the PAL six- pattern stage (p = 0.03), which remained after psychiatric co-morbidity was controlled for (p = 0.04). Morning cortisol levels were lower in IBS (p = 0.04) and significantly associated with visuospatial memory performance within IBS only (p = 0.02). CONCLUSIONS: For the first time, altered cognitive function on a hippocampal-mediated test of visuospatial memory, which was related to cortisol levels and independent of psychiatric co-morbidity, has been identified in IBS. Visuospatial memory impairment may be a common, but currently neglected, component of IBS. Further elucidation of the nature of this impairment may lead to a greater understanding of the underlying pathophysiology of IBS, and may provide novel therapeutic approaches.

Enhanced slow wave sleep and improved sleep maintenance after gaboxadol administration during seven nights of exposure to a traffic noise model of transient insomnia.

Slow wave sleep (SWS) has been reported to correlate with sleep maintenance, but whether pharmacological enhancement of SWS also leads to improved sleep maintenance is not known. Here we evaluate the time-course of the effects of gaboxadol, an extra-synaptic gamma-aminobutyric acid (GABA) agonist, on SWS, sleep maintenance, and other sleep measures in a traffic noise model of transient insomnia. After a placebo run-in, 101 healthy subjects (20-78 y) were randomized to gaboxadol (n = 50; 15 mg in subjects <65 y and 10 mg in subjects ≥65 y) or placebo (n = 51) for 7 nights (N1-N7). The model caused some disruption of sleep initiation and maintenance, with greatest effects on N1. Compared with placebo, gaboxadol increased SWS and slow wave activity throughout N1 to N7 (p < 0.05). Gaboxadol reduced latency to persistent sleep overall (N1-N7) by 4.5 min and on N1 by 11 min (both p < 0.05). Gaboxadol increased total sleep time (TST) overall by 16 min (p < 0.001) and on N1 by 38 min (p < 0.0001). Under gaboxadol, wakefulness after sleep onset was reduced by 11 min overall (p < 0.01) and by 29 min on N1 (p < 0.0001), and poly-somnographic awakenings were reduced on N1 (p < 0.05). Gaboxadol reduced self-reported sleep onset latency overall and on N1 (both p < 0.05) and increased self-reported TST overall (p < 0.05) and on N1 (p < 0.01). Subjective sleep quality improved overall (p < 0.01) and on N1 (p < 0.0001). Increases in SWS correlated with objective and subjective measures of sleep maintenance and subjective sleep quality under placebo and gaboxadol (p < 0.05). Gaboxadol enhanced SWS and reduced the disruptive effects of noise on sleep initiation and maintenance.

Effects of upper-limb immobilisation on driving safety.

Doctors are frequently asked by patients whether it is safe to drive with an upper limb immobilised in a cast. In the literature there are no objective measurements of the effects of upper-limb immobilisation upon driving performance. Eight healthy volunteers performed four 20-min driving circuits in a driving simulator (STISIM 400W), circuits 1 and 4 without immobilisation and circuits 2 and 3 with immobilisation. Immobilisation involved a lightweight below-elbow cast with the thumb left free. Volunteers were randomised to right or left immobilisation for circuit 2, and the contralateral wrist was immobilised for circuit 3. Circuits included urban and rural environments and specific hazards (pedestrians crossing, vehicles emerging from a concealed entrance, traffic lights changing suddenly, avoidance of an oncoming vehicle in the driver's carriageway). Limb immobilisation led to more cautious rural and urban driving, with less adjustment of speed and lateral road position than when unrestricted. However when responding to hazards immobilisation caused less safe driving, with higher speeds, a greater proximity to the hazard before action was taken and less steering adjustment. The effects of restriction upon performance were more prevalent and severe with right-arm immobilisation. Upper-limb immobilisation appears to have little effect on the ability to drive a car unchallenged, but to adversely affect responses to routine hazards. Advice on ability to drive safely should be cautious, as the impact of immobilisation appears to be more subtle and wide ranging than previously thought.

Serial memory for sound-specified locations: effects of spatial uncertainty and motor suppression.

According to Parmentier and Jones (2000), serial recall of locations that are specified by a sequence of sounds is prone to temporal error and is unaffected by motor suppression during retention. Experiments are reported here that show that with increased spatial uncertainty at recall (Experiment 1) and presentation (Experiment 2), spatial rather than temporal errors predominate. This is also the case when serial recall of sound-specified locations is subject to interference from a motor suppression task (Experiment 3). Contrary to Parmentier and Jones's (2000) original report, these results suggest that the memory representation for location is not necessarily amodal but is influenced by the representational requirements of the task being performed. This is consistent with recent findings that provide evidence for a distinct spatial working memory.

Anticipating the content and circumstances of skill transfer: unrealistic expectations of driver training and graduated licensing?

There is substantial evidence that driving skills improve during driver training, but the long-term safety benefit of such formal training remains unproven. Restricting the exposure of newly licensed drivers to more hazardous driving circumstances, as in graduated driver licensing (GDL) regimes, demonstrably reduces crash risk, but drivers remain at risk after the restrictions are eased. GDL and most other licensing regimes advocate increased basic training and practice, but thereafter require neither advanced training nor systematic increase in exposure to risk. This assumes that basic skills acquired during formal training will transfer positively to new and more demanding traffic circumstances. This paper reviews the theoretical basis for these assumptions and offers a way of systematically identifying the extent of transfer desired. It is concluded that there is little theoretical or empirical foundation for the supposition that what is learned during or after training will have a safety benefit in later driving.

Youthfulness, inexperience, and sleep loss: the problems young drivers face and those they pose for us.

Young inexperienced drivers are more likely to be involved in road traffic crashes than drivers who are older and more experienced. This paper argues that neither age nor inexperience are, in and of themselves, sufficient explanations of the association between age, experience, and casualty rates. The aim here is to consider what it is about inexperienced young drivers in particular that may increase crash risk. Evidence is reviewed showing differential sleep loss among different teenage groups, which may relate to recently presented evidence that young teenagers are more crash involved than drivers in their early twenties. Potential acute and chronic effects of sleep loss among teenagers and young adults are described.

Attention-memory interactions in scene perception.

The perception of natural scenes relies on the integration of pre-existing knowledge with the immediate results of attentional processing, and what can be remembered from a scene depends in turn on how that scene is perceived and understood. However, there are conflicting results in the literature as to whether people are more likely to remember those objects that are consistent with the scene or those that are not. Moreover, whether any discrepancy between the likelihood of remembering schema-consistent or schema-inconsistent objects should be attributed to the schematic effects on attention or on memory remains unclear. To address this issue, the current study attempted to directly manipulate attention allocation by requiring participants to look at (i) schema-consistent objects, (ii) schema-inconsistent objects, or (iii) to share attention equally across both. Regardless of the differential allocation of attention or object fixation, schema-consistent objects were better recalled whereas recognition was independent of schema-consistency, but depended on task instruction. These results suggest that attention is important both for remembering low-level object properties, and information whose retrieval is not supported by the currently active schema. Specific knowledge of the scenes being viewed can result in the recall of non-fixated objects, but without such knowledge attention is required to encode sufficient detail for subsequent recognition. Our results demonstrate therefore that attention is not critical for the retrieval of objects that are consistent with a scene's schematic content.

Sleep quantity, sleep difficulties and their perceived consequences in a representative sample of some 2000 British adults.

Sleep problems and sleep restriction are popular topics of discussion, but few representative data are available. We document Britain's sleep based on a nationally representative sample of 1997, 16-93 year olds, who participated in face-to-face interviews. Fifty-eight per cent of respondents reported sleep problems on one or more nights the previous week and 18% reported that the sleep they obtained was insufficient on the majority of nights. Sleep durations were longest in the youngest participants (16-24 years), who slept on average 1 h longer than the 7.04 (SD 1.55) sample average. Sleep duration showed no appreciable change beyond middle age. Men and women reported sleeping similar amounts but women reported more sleep problems. Men reported sleeping less when there were more children in their household. Workers (i.e. employees) reported sleeping less on workdays than on non-workdays, but those based at home and those not employed did not. Inability to switch off from work was related to sleep duration on non-workdays. Across all participants average sleep duration exhibited a non-monotonic association with quality of life (i.e. contribution of sleep to energy, satisfaction and success in work, home and leisure activities). Quality of life was positively associated with sleep duration, for durations up to 9 h, but negatively associated with quality of life beyond this. Comparison of our data with the US national sleep poll revealed that Britain sleeps as little or less, whereas a comparison with data reported 40 years ago revealed no statistically reliable reductions. Although we may not sleep less than four decades ago, when we report sleeping less we also tend to associate that lack of sleep with poor performance and quality of life.

Working-memory and auditory localization: demand for central resources impairs performance.

Four experiments explored possible roles for working memory in sound localization. In each experiment, the angular error of localization was assessed when performed alone, or concurrently with a working-memory task. The role of the phonological slave systems in auditory localization was ruled out by Experiments 1 and 2, while an engagement of central resources was suggested by the results of Experiment 3. Experiment 4 examined the involvement of visuo-spatial systems in auditory localization and revealed impairment of localization by the concurrent spatial working-memory task. A comparison of dual-task decrement across all four studies suggests that localization places greater demand on central than on spatial resources.

Assessing one's own and others' driving ability: influences of sex, age, and experience.

Observational studies of drivers' involvements in dangerous situations suggest that young males drive differently from other road users. Studies of drivers' assessments of their own ability appear to show that they believe they drive better than their peers and that, while young males equate their ability with that of older male drivers, the latter group see themselves as superior to their younger counterparts but of equivalent ability to peers. It is unclear from previous studies what the influence of driving experience is on such assessments and, indeed, what female drivers feel about their ability. The present studies suggest that the widely reported tendency for people to overestimate their ability may be largely artifactual, that males and females describe their performance similarly, and that previously reported age differences disappear when driving experience is controlled. Among the differences that remain is the reported greater "recklessness" and comparative lack of "smoothness" of young males' driving. The implications of these findings for our understanding of risk assessment and acceptance are discussed.

Evidence of unconscious semantic processing from a forced error situation.

A study was carried out to determine whether subjects extracted information from words presented below their recognition and awareness thresholds. A series of target words was used to generate the word matrix, which was a set of 24 words related to the target in specified ways. Following subthreshold exposure of a target word, subjects chose the word they thought had been shown from the word matrix for that particular target. It was held that the alternative chosen was a function of the type of processing the target was receiving. Results showed that structural analysis of the target predominated below recognition threshold, whereas semantic analysis predominated below awareness threshold.