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Inhibitory deficits, delay aversion and preschool AD/HD: implications for the dual pathway model.

The dual pathway model proposes the existence of separate and neurobiologically distinct cognitive (inhibitory and more general executive dysfunction) and motivational (delay aversion) developmental routes to AD/HD. The study reported in this paper explores the relation between inhibitory deficits and delay aversion and their association with AD/HD in a group of three-year-old children. Children identified as having a pre-school equivalent of AD/HD (N=19) and controls (N=19), matched for gender and IQ, completed a battery of inhibition and delay tasks. Correlational and factor analysis supported a dissociation between inhibitory deficits (go-no-go, set shifting) and delay aversion (choice delay) with delay of gratification cross-loading. Children with AD/HD displayed more inhibitory deficits and were more delay averse than controls. The data support the value of the distinction between motivational and cognitive pathways to AD/HD. Furthermore, the data suggest that such a distinction is apparent relatively early on during development.

Analysis of Variance↗

Prism adaptation can improve contralesional tactile perception in neglect.

The authors show that prismatic adaptation can reduce tactile inattention in stroke patients with unilateral neglect. Four patients with visuospatial neglect and tactile extinction underwent 10-minute application of 20 degrees right-shifting prismatic lenses during pointing. This improved contralesional tactile perception in all patients, even for a task requiring no exploration or spatial motor responses. This finding suggests a potential role for prismatic adaptation in the rehabilitation of multiple sensory modalities in patients with neglect.

Adaptation, Physiological↗

Mouse Period1 (mPER1) acts as a circadian adaptor to entrain the oscillator to environmental light/dark cycles by regulating mPER2 protein.

Mouse period1 (mPer1) and mPer2 are mammalian homologs of the Drosophila clock gene period that show robust oscillation in the suprachiasmatic nucleus, the mammalian master clock, and have been implicated as essential components of the core clock mechanism. Gene-targeting studies have demonstrated that mPer2 plays a dominant function in behavioral rhythm generation, although the role of mPer1 has not been fully clarified. Here, we report that prolongation of the lighting period (4-16 h) induces a larger-delay phase shift of the behavioral rhythm in mPer1-deficient (mPer1-/-) mice. During the light-elongation task, mPER2 protein decay in mPer1-/- mice is slower (approximately 4 h) than in wild-type mice, which thereby causes larger behavioral phase delay. mPer1-/- mice could not adapt to environmental light/dark cycles in long complete photoperiods with dim light or in long skeleton photoperiods. These photoperiodic conditions mimic natural environmental changes present at high latitudes, indicating that mPer1 could operate in the adaptation of the circadian clock of nocturnal mice to large seasonal changes of environmental light/dark cycles.

Analysis of Variance↗

The cerebral correlates of set-shifting: an fMRI study of the trail making test.

The trail making test (TMT) pertains to a family of tests that tap the ability to alternate between cognitive categories. However, the value of the TMT as a localizing instrument remains elusive. Here we report the results of a functional magnetic resonance imaging (fMRI) study of a verbal adaptation of the TMT (vTMT). The vTMT takes advantage of the set-shifting properties of the TMT and, at the same time, minimizes the visuospatial and visuomotor components of the written TMT. Whole brain BOLD fMRI was performed during the alternating execution of vTMTA and vTMTB in seven normal adults with more than 12 years of formal education. Brain activation related to the set-shifting component of vTMTB was investigated by comparing performance on vTMTB with vTMTA, a simple counting task. There was a marked asymmetry of activation in favor of the left hemisphere, most notably in dorsolateral prefrontal cortex (BA 6 lateral, 44 and 46) and supplementary motor area/cingulate sulcus (BA 6 medial and 32). The intraparietal sulcus (BA 7 and 39) was bilaterally activated. These findings are in line with clinico-anatomic and functional neuroimaging data that point to a critical role of the dorsolateral and medial prefrontal cortices as well as the intraparietal sulci in the regulation of cognitive flexibility, intention, and the covert execution of saccades/anti-saccades. Many commonly used neuropsychological paradigms, such as the Stroop, Wisconsin Card Sorting, and go - no go tasks, share some patterns of cerebral activation with the TMT.

Adult↗

Health of a team competing in the 1990 World Solar Car Challenge.

The health of a team participating in the 1990 World Solar Car Challenge was recorded for 10 of the 11 race days. Morbidity was collected during daily consultations with the team doctor and the diagnoses were later converted to the ICPC code. Team members' self-perceived health status was also recorded daily, using the Nottingham Health Profile. Team drivers consulted the doctor more often than the support staff and the three full-time drivers had significantly more diagnoses than the support staff. The Nottingham Health Profile scores on sleep, energy and emotional reactions showed correlations between higher minimum temperatures and sleep for all team members and for the three full-time drivers, there were significant correlations between increasing maximum temperatures and emotional reaction scores. The morbidity records and perceived health scores reflect the conditions of the race. Twenty-five per cent of full-time driver consultations dealt with skin, eyelid or finger infections probably caused by the lack of washing water. The scores on sleep and emotional reactions were affected by temperature and previous research reports degradation in concentration and dual tasks with increasing temperature. This may account for the difficulty some drivers had in continuing their shifts. Close supervision of the drivers and the recording of their perceived health status helped reduce the health problems of the team.

Adult↗

Metacontrast as measured under a signal detection model.

Metacontrast is assessed both by percent accuracy and by the dichotomous sensitivity and criterion measures of a signal-detection model in a forced-choice detection task. The results showed a monotonic increase in sensitivity with increasing mask delay, and an abrupt shift of subjects' response criterion at an 80 ms interstimulus interval. The results are discussed in terms of the interpretational advantages of a signal-detection approach to metacontrast investigation.

Humans↗

Contributions of the dopaminergic system to voluntary and automatic orienting of visuospatial attention.

Visuospatial attention can be directed by voluntary or involuntary control independent of eye movement. The involvement of cortical and subcortical neural structures in this covert orienting mechanism has been studied using neuroimaging and electrophysiological techniques. This study was designed to investigate the role of the dopaminergic system in both voluntary and automatic orienting mechanisms of visuospatial attention. We recorded event-related evoked potentials (ERPs) and reaction time (RT) during a cued priming task in both patients with idiopathic Parkinson's disease (PD) and control subjects. Voluntary and automatic shifts in attention were studied by using central and peripheral cues, respectively. In the experiment using a central cue, the RT data showed that when the cue-target interval was long, PD patients' responses were delayed, and cue validity effects were reduced, whereas in the peripheral cue experiment the validity effects persisted across all trials. The ERPs demonstrated reduced sustained negativities preceding the imperative targets in both the central and peripheral cue experiments in PD patients. Furthermore, during the long cue-target interval in the central cue experiment, PD patients showed reduced attention shift-related negativities (ARNs) at the anterior scalp sites, whereas ARNs were generated widely in the peripheral cue experiment. The ERP findings were consistent with the RT data. These findings suggest that the dopaminergic system may contribute to voluntary and sustained control of visuospatial attention as well as to the neural system for response preparation, whereas automatic control of visuospatial attention is relatively independent of the dopamine system.

Aged↗

Clustering and switching strategies in verbal fluency tasks: comparison between schizophrenics and healthy adults.

Verbal fluency tasks are frequently used in clinical neuropsychology. Clustering (the production of words within semantic subcategories) and switching (the ability to shift between clusters) have been described as 2 components underlying fluency performance. We compared the use of clustering and switching in schizophrenic patients and healthy subjects. Seventy-eight schizophrenic subjects (DSM-IV criteria) and 64 control participants matched for age and educational level were recruited. Negative, disorganized, and productive clinical dimensions were evaluated using the SANS and SAPS scales. The number of words generated per semantic-phonemic cluster and the number of switches were evaluated during 2 verbal fluency tasks (phonemic and semantic). In the healthy controls switching and clustering were closely related to the total number of words generated in the verbal fluency tests. The role of the 2 components was partly dependent on the specific task. Switching was prevalent in formal fluency, while both switching and clustering contributed to semantic fluency. In comparison to the healthy controls, the overall group of schizophrenic patients showed a significant impairment of switching in the formal fluency task and of both switching and clustering in the semantic fluency task, and both the negative and disorganized dimensions correlated with verbal fluency performance, the number of swtiches during the phonemic fluency task, and the clustering during semantic fluency task.

Adult↗

Material type and attention control in dichotic listening.

The present study investigated the effects of semantic and emotional content on laterality effects found in focused attention dichotic listening tasks. A total of 80 right-handed participants completed one of four conditions. They were presented either with dichotic pairs of consonant-vowel (CV) syllables (ba, da, ga, ka, pa, or ta) or words (bower, dower, power, or tower), pronounced in either a neutral tone or one of four emotional tones (happy, sad, angry, neutral). In all conditions, participants were instructed to circle the stimulus presented to the attended ear on each trial. The attended ear was randomised between blocks of trials for each participant. A significant condition by ear attended by ear of presentation interaction emerged. The typical right ear advantage (REA) was found in the neutral conditions, regardless of ear attended. In contrast, the emotional conditions revealed an REA when participants focused on the right ear, whereas a left ear advantage was found when they focused on the left ear. These findings suggest that the emotional component resulted in a shift in ear advantage coinciding with instructions possibly because of the influence of this component on attention and task difficulty. The role of semantic processing in words versus syllables is also discussed.

Adolescent↗

[Studies on the combined effects of shift work and noise on permanent hearing loss].

Combined exposure to shiftwork and noise was investigated with respect to its aural damaging effect. The investigations were carried out on 347 male and female noise-exposed textile workers working in single-shift and three-shift systems. The average hearing loss for the PTS at 3 kHz, 4 kHz, the total hearing loss at 0.5, 1, 2, 4, 6, 8 kHz and percentage of hearing loss according to Fowler/Sabine served as indicators. To fulfil this task an epidemiological cross-sectional study was performed. The results of the present study show lower average hearing loss values in the case of three-shift workers as compared with single-shift workers.

Adult↗

The functional and structural significance of the frontal shift in the old/new ERP effect.

There is a lack of studies mapping electrophysiological event-related potentials (ERPs) to structural neuroanatomical characteristics. The aim of the present study was to integrate electrophysiological memory-related activity with cortical and hippocampal volume, as well as psychometric memory performance, in a life-span sample. More specifically, we wanted to investigate the functional significance of the often-observed frontal shift of ERP amplitude with increasing age and whether neuroanatomical characteristics can explain this shift. Sixty six healthy participants (20-78 years) went through a neuropsychological examination, MRI scans, and a visual recognition ERP task with verbal stimuli. The results showed that ERPs elicited in the recognition memory task (the old/new effect) correlated significantly with cortical volume, but not with hippocampal volume. Large cortex predicted more differentiated ERP activity and not just larger amplitude in general, implying more distinct and efficient retrieval. Furthermore, ERP amplitude, cortical volume, and hippocampal volume all predicted scores on a composite memory scale. All these relationship were dependent upon the common influence of age. Finally, the participants with the most anterior distribution of activity showed the poorest recognition memory performance. Neither cortical nor hippocampal volume were related to this frontal shift. It is concluded that the distribution of activity along the anterior-posterior axis in a memory paradigm may have functional but not neuroanatomical volumetric correlates. The functional correlates need not be restricted to the older age groups.

Adult↗

The effects of practice on the functional anatomy of task performance.

The effects of practice on the functional anatomy observed in two different tasks, a verbal and a motor task, are reviewed in this paper. In the first, people practiced a verbal production task, generating an appropriate verb in response to a visually presented noun. Both practiced and unpracticed conditions utilized common regions such as visual and motor cortex. However, there was a set of regions that was affected by practice. Practice produced a shift in activity from left frontal, anterior cingulate, and right cerebellar hemisphere to activity in Sylvian-insular cortex. Similar changes were also observed in the second task, a task in a very different domain, namely the tracing of a maze. Some areas were significantly more activated during initial unskilled performance (right premotor and parietal cortex and left cerebellar hemisphere); a different region (medial frontal cortex, "supplementary motor area") showed greater activity during skilled performance conditions. Activations were also found in regions that most likely control movement execution irrespective of skill level (e.g., primary motor cortex was related to velocity of movement). One way of interpreting these results is in a "scaffolding-storage" framework. For unskilled, effortful performance, a scaffolding set of regions is used to cope with novel task demands. Following practice, a different set of regions is used, possibly representing storage of particular associations or capabilities that allow for skilled performance. The specific regions used for scaffolding and storage appear to be task dependent.

Brain↗

Response inhibition initiates cardiac deceleration: evidence from a sensory-motor compatibility paradigm.

Two experiments tested the hypothesis that response selection processes alter the timing of the shift between anticipatory cardiac deceleration and acceleratory recovery. Experiment 1 compared changes in cardiac interbeat interval induced by the manipulation of sensory-motor compatibility in a four choice reaction time task. A direct spatial mapping between a linear array of light-emitting diodes (LEDs) was compared to randomly assigned, indirect (non-compatible) mappings. Experiment 2 repeated these two tasks and added a two choice condition with direct spatial mapping, a task frequently employed to examine heart rate deceleration. Fifteen college aged males participated in Experiment 1; 18 college aged males participated in Experiment 2. In both experiments anticipatory cardiac deceleration either reached a plateau or shifted to acceleration by the interbeat interval in which the stimulus occurred. In contrast to previous reports, a secondary deceleration, rather than cardiac acceleration, often followed the stimulus. The secondary deceleration was greater with non-compatible mapping, slow response speeds, and short intertrial intervals. The findings suggested that the motoric inhibition required during response selection induces a phasic cardiac deceleration.

Adolescent↗

Improving daytime sleep with temazepam as a countermeasure for shift lag.

BACKGROUND: Working night shift (reverse cycle) presents problems to personnel due to the difficulty in maintaining alertness during the nighttime hours. When the shift must be worked several consecutive nights, a cumulative sleep debt is created. Appropriate countermeasures are required to help personnel obtain as much sleep as possible so they may perform their duties effectively. HYPOTHESIS: The objectives were to determine whether a hypnotic taken before daytime sleep would improve sleep quality, and to determine whether improved daytime sleep would increase alertness, reduce fatigue, and mitigate the usual performance decrements which occur on night shift. METHODS: Sixteen UH-60 Army aviators were randomly assigned to either a temazepam or a placebo group. Test sessions, consisting of vigilance assessments, flight simulation, and mood state questionnaires were administered during baseline, three nights of reverse cycle, and three days following a return to day shift. Temazepam (30 mg) was administered before daytime sleep to one group while another group received a lactose-filled capsule. RESULTS: Subjects who received temazepam slept longer and with less fragmentation than those who received placebo. Generally, the subjects in the temazepam group indicated more subjective alertness and less fatigue than those in the placebo group. Flight performance was not unequivocally improved by better daytime sleep, but the temazepam group performed better on the Psychomotor Vigilance Task than the placebo group. CONCLUSIONS: Temazepam is helpful in prolonging daytime sleep, with some attenuation of performance decrements during the night shift. However, physicians should be careful when administering this substance to ensure the aviator has a minimum of 8 h in which to sleep.

Administration, Oral↗

Attentional shifting and the role of the dorsal pathway in visual word recognition.

A substantial amount of evidence has been collected to propose an exclusive role for the dorsal visual pathway in the control of guided visual search mechanisms, specifically in the preattentive direction of spatial selection [Vidyasagar, T. R. (1999). A neuronal model of attentional spotlight: Parietal guiding the temporal. Brain Research and Reviews, 30, 66-76; Vidyasagar, T. R. (2001). From attentional gating in macaque primary visual cortex to dyslexia in humans. Progress in Brain Research, 134, 297-312]. Moreover, it has been suggested recently that the dorsal visual pathway is specifically involved in the spatial selection and sequencing required for orthographic processing in visual word recognition. In this experiment we manipulate the demands for spatial processing in a word recognition, lexical decision task by presenting target words in a normal spatial configuration, or where the constituent letters of each word are spatially shifted relative to each other. Accurate word recognition in the Shifted-words condition should demand higher spatial encoding requirements, thereby making greater demands on the dorsal visual stream. Magnetoencephalographic (MEG) neuroimaging revealed a high frequency (35-40Hz) right posterior parietal activation consistent with dorsal stream involvement occurring between 100 and 300ms post-stimulus onset, and then again at 200-400ms. Moreover, this signal was stronger in the shifted word condition, compared to the normal word condition. This result provides neurophysiological evidence that the dorsal visual stream may play an important role in visual word recognition and reading. These results further provide a plausible link between early stage theories of reading, and the magnocellular-deficit theory of dyslexia, which characterises many types of reading difficulty.

Attention↗

Discrimination of rippled-spectrum noise from flat-spectrum noise by chinchillas: evidence for a spectral dominance region.

Iterated rippled noise having infinite iterations is generated when a flat-spectrum wideband noise is delayed T ms and the delayed version is added to the undelayed noise through positive feedback. The resulting signal has a rippled spectrum, and the perceived pitch of this iterated rippled noise by human listeners corresponds to a frequency of 1/T. We have previously demonstrated that chinchillas can discriminate the rippled-spectrum noise from the flat-spectrum noise. In the present study, chinchillas discriminated a bandpass filtered rippled-spectrum noise from a bandpass flat-spectrum noise in a psychophysical task. The passbands were set to be one octave wide. Psychometric functions were obtained for 5 chinchillas and performance was measured as d'. The best behavioral performance was obtained when the center frequency of the bandpass filter generally corresponded to the 3rd 5th harmonic peak of the rippled noise (i.e., at 3/T to 5/T), but the precise location of the dominant region varied with the delay of the rippled noise such that the dominance region tended to shift to lower harmonics as 1/T increased. These results indicate that not all spectral regions are weighted equally in the discrimination task. The spectral dominance region found in chinchillas is similar to that described for human pitch perception.

Acoustic Stimulation↗

Finding time, stopping the frenzy.

While the deleterious consequences of long hours of work for individuals, families and communities have previously been documented, the assumption that long hours are necessary to get the work done, especially in a world where speed is becoming increasingly critical to corporate success, has prompted little challenge. So Leslie Perlow, an assistant professor of business at the University of Michigan, Ann Arbor, set out to explore the necessity for the seemingly endless workdays that so many postindustrial settings require. Her study of a group of software engineers at a Fortune 500 company--identified only as the Ditto Corp--is detailed in her book, Finding Time: How Corporations, Individuals, and Families Can Benefit from New Work Practices (Cornell University Press, 1997). Perlow's research reveals a "sad and all too common tale" of workers harried by competing demands, frequent interruptions and shifting deadlines. To meet the firm's expectations, the engineers she studied sacrificed home life, focused on individual tasks to the detriment of group goals and, in many cases, eventually lost any enthusiasm they'd had for working for the company. There has been some recognition that stress and burnout may be bad for a corporation as employees become less committed, decide to leave or get fired and that this kind of turnover can hurt the firm in the longer term. But Perlow documented the additional, and quite significant, shorter-term costs to the corporation of the current way of using time at work. What she found was a "vicious time cycle:" Time pressures led to a crisis mentality, which led to "individual heroics." That is, I'll do whatever it takes to do my job--even if it means interrupting you while you try to do yours. For the engineers Perlow studied, the lack of helping, the constant interruptions and the perpetual crises--clearly illustrated by the daily log that appears on page 34--made it harder to develop products. Ultimately, they worked long hours to complete tasks they'd been too busy to do earlier because of the constant interruptions. Worse, because everyone was busy responding to crises, no one had time to prevent future crises, thus perpetuating the cycle. But as dire as the situation sometimes seemed, change was possible. The "quiet time" phase of the author's nine-month study indicated that productivity could be enhanced by structuring work time to allow the engineers intervals to work alone, uninterrupted. After this first phase, about two out of three of the 17 people involved said their productivity during quiet time was above average. Nearly as many said overall productivity was above average as well. This implies that the costs of the current way of using time exceed the benefits. The data further show that change must be collective, addressing all elements of the vicious cycle. The promising implication is that collective change could benefit everyone--corporations, individuals and families. The work process could be made more efficient and effective. At the same time, individuals could succeed at work and still have time for responsibilities outside of work; people might not have to choose so definitively between their work and their home lives. To make the necessary changes, however, will require a shift from a system that rewards individuals heroics and long hours to one that rewards individuals' contributions to their teams--without the accompanying emphasis on visible work hours. That is, there must be a shift in emphasis from individual to collective achievement. And there must be a sharing of the resulting gains in efficiency between employees and employers. In the following excerpt from her book, Perlow describes what is needed to turn a vicious time cycle into a "virtuous" one:

Burnout, Professional↗

Brain regions involved in spatial frequency discrimination: evidence from fMRI.

The cortical areas underlying successive spatial-frequency discrimination were explored using functional magnetic resonance imaging (fMRI). In a steady-state, block-design paradigm, 12 subjects viewed a single fixation cross during a rest period, followed by an activation period consisting of the presentation of horizontal (distractors) and vertical (targets) sinewave gratings. Two tasks were performed: in the control task, subjects pressed a button after the second vertical grating was presented within each trial; in the discrimination task, subjects decided which target grating had the higher spatial frequency. Post-processing consisted of off-line image registration to correct for head motion, spatial and temporal smoothing, and cross-correlation between each voxel time course and a phase-shifted stimulus time profile. The results indicate that striate, extrastriate, parietal, and prefrontal areas show significant BOLD (blood oxygen level dependent) effects during both discrimination and control tasks, with consistently higher activity levels in the discrimination task.

Discrimination, Psychological↗