Substance use prevention program for adolescents with intellectual disabilities on special education schools: a cluster randomised control trial.

BACKGROUND: Students without intellectual disability (ID) start experimenting with tobacco and alcohol between 12 and 15 years of age. However, data for 12- to 15-year old students with ID are unavailable. Prevention programs, like 'PREPARED ON TIME' (based on the attitude-social influence-efficacy model), are successful, but their efficacy has not been studied in students with ID. The objectives of this study were (1) to undertake a cluster randomised control trial to test the efficacy of the e-learning program among 12- to 15-year old students with mild and borderline ID in secondary special-needs schools and (2) to examine the tobacco and alcohol use for this population. METHODS: Five schools, randomly selected to be part of either the experimental group or the control group, participated in this study. Passive informed consent was used in which parents and their children can refuse to participate in the study, resulting in 111 students in the experimental group and 143 students in the control group. A total of 210 students completed both baseline and follow-up questionnaires. Primary outcome variables are the knowledge and attitude towards alcohol and tobacco use. This study is registered in the ISRCTN registry with number ISRCTN95279686. RESULTS: Baseline findings showed that a large proportion of all respondents had initiated smoking (49%) and drinking (75%), well above the expected numbers based on national figures. 'PREPARED ON TIME' did not affect the behavioural determinants (i.e. attitude, subjective norm and self-efficacy), except modelling on smoking. Additionally, alcohol-related knowledge of students in the experimental group increased after the completion of the program. CONCLUSIONS: To obtain effective results on behavioural outcomes from 'PREPARED ON TIME', a greater degree of flexibility (i.e. repetition, extension of the program, role playing, etc.) is required. Furthermore, prevention needs to be implemented at a younger age, as 6% of the students tried their first cigarette and 15% of the students drank alcohol at the age of 10 years or younger.

Effect of respiratory CO(2) changes on the temporal dynamics of the hemodynamic response in functional MR imaging.

Increasing end-expiratory CO(2) levels (PETCO(2)) increases the dispersion and the time of maximum of the hemodynamic response curve in human primary visual cortex. This was demonstrated using event-related multislice functional magnetic resonance imaging (fMRI) with short repetition time and 3-s flicker light stimulation. Measurements were performed at 5 different PETCO(2) levels between 20 and 60 mmHg using hyperventilation or by adding CO(2) to the inspired air. Between 30 and 60 mmHg the full-width-at-half-maximum of the hemodynamic response curve induced by visual stimulation increased nearly linearly at 130 ms per mmHg PETCO(2). Consistent with previous studies a concomitant decrease of the signal amplitude was observed at PETCO(2) values below 40 mmHg and above 50 mmHg. The relevance of these findings for the temporal resolution of fMRI and especially of event-related methods is discussed.

Interdependence of regional and global cerebral blood flow during visual stimulation: an O-15-butanol positron emission tomography study.

The authors investigated the influence of variations in global cerebral blood flow (gCBF) on regional flow changes during visual stimulation. Global flow was varied using different end-expiratory CO2 values (PETCO2) between 20 and 70 mm Hg. Visual stimulation was performed with a red LED-array flashing at 8 Hz. Blood flow was measured with 0-15-butanol, continuous arterial blood sampling, and positron emission tomography (PET). Global flow changes surpassed the published values of O-15-H2O studies, better fitting the results of the inert gas technique (gCBF at 20, 40, and 70 mm Hg PETCO2 +/- SD was 31 +/- 4, 48 +/- 13, and 160 +/- 50 mL 100 g(-1) min(-1), respectively). The relation between PETCO2 and CBF in the current study was best described by an exponential rather than a linear function. At low PETCO2, the activation-induced flow changes are moderately damped, whereas at high PETCO2, they are nearly lost (deltaCBF (+/-SD): 52% +/- 25%, 68% +/- 22%, 16% +/- 25% at PETCO2 = 20, 40, 70 mm Hg, respectively).

Effect of graded hypo- and hypercapnia on fMRI contrast in visual cortex: quantification of T(*)(2) changes by multiecho EPI.

The sensitivity of functional magnetic resonance imaging (fMRI) in visual cortex to graded hypo- and hypercapnia was quantified in 10 normal subjects using single-shot multiecho echo-planar imaging (Turbo-PEPSI) with eight equidistant echo times (TEs) between 12 and 140 ms. Visual stimulation was combined with controlled hyperventilation and carbon dioxide inhalation to perform fMRI at six levels of end-expiratory pCO(2) (PETCO(2)) between 20 and 70 mm Hg. T(*)(2) in visual cortex during baseline conditions (light off) increased nonlinearly from 20 to 70 mm Hg, from 61.1 +/- 4.2 ms to 72.0 +/- 4.6 ms. Changes in T(*)(2) due to visual stimulation increased 2.1-fold, from 1.2 +/- 0.6 ms at 20 mm Hg to 2.5 +/- 0.7 ms at 50 mm Hg. An almost complete loss of functional contrast was measured at 70 mm Hg. The model of MR signal dephasing by Yablonskiy and Haacke (Mag Reson Med 1994;32:749-763) was used to predict changes in cerebral blood flow (CBF), which were found to be consistent with results from previous positron emission tomography (PET) studies. This study further emphasizes that global CBF changes (due to PETCO(2) changes even in the physiological range) strongly influence fMRI contrast and need to be controlled for.

Integrating electrophysiology and neuroimaging of spatial selective attention to simple isolated visual stimuli.

Visual-spatial attention involves modulations of activity in human visual cortex as indexed by electrophysiological and functional neuroimaging measures. Prior studies investigating the time course and functional anatomy of spatial attention mechanisms in visual cortex have used higher-order discrimination tasks with complex stimuli (e.g. symbol matching in bilateral stimulus arrays, or letter discrimination), or simple detection tasks but in the presence of complex distracting information (e.g. luminance detection with superimposed symbols as distractors). Here we tested the hypothesis that short-latency modulations of incoming sensory signals in extrastriate visual cortex reflect an early spatially specific attentional mechanism. We sought evidence of attentional modulations of sensory input processing for simple, isolated stimuli requiring only an elementary discrimination (i.e. size discrimination). As in prior studies using complex symbols, we observed attention-related changes in regional cerebral blood flow in extrastriate visual cortex that were associated with changes in event-related potentials at a specific latency range. These findings support the idea that early in cortical processing, spatially-specific attentional selection mechanisms can modulate incoming sensory signals based on their spatial location and perhaps independently of higher-order stimulus form.

Modulation of the neuronal circuitry subserving working memory in healthy human subjects by repetitive transcranial magnetic stimulation.

We studied the effect of repetitive transcranial magnetic stimulation (rTMS) on changes in regional cerebral blood flow (rCBF) as revealed by positron emission tomography (PET) while subjects performed a 2-back verbal working memory (WM) task. rTMS to the right or left dorsolateral prefrontal cortex (DLPFC), but not to the midline frontal cortex, significantly worsened performance in the WM task while inducing significant reductions in rCBF at the stimulation site and in distant brain regions. These results for the first time demonstrate the ability of rTMS to produce temporary functional lesions in elements of a neuronal network thus changing its distributed activations and resulting in behavioral consequences.

Functional imaging of the visual cortex with bold-contrast MRI: hyperventilation decreases signal response.

Hypocapnia due to hyperventilation reduces cerebral blood flow and volume. To investigate the effects of hyperventilation on the regional signal response to visual activation using blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI), six volunteers were investigated during visual stimulation under normocapnia and hypocapnia conditions. Hyperventilation significantly decreased in visual cortex the BOLD MRI response to visual stimulation (3.97+/-0.5% [mean ( SD) in normocapnia vs. 0.77+/-0.7% in hypocapnia, P < 0.01]. In three of six subjects, functional signal changes were reduced to noise level. The reduced stimulus response during hyperventilation is probably due to a decreased overshoot in the blood oxygenation response. These results indicate that BOLD-contrast functional MRI is highly sensitive to pCO2 changes.

Iodine-123 alpha-methyl tyrosine single-photon emission tomography of cerebral gliomas: standardised evaluation of tumour uptake and extent.

Single-photon emission tomography (SPET) with the amino acid analogue l-3-[123I]iodo-alpha-methyl tyrosine (IMT) is helpful in the diagnosis and monitoring of cerebral gliomas. Radiolabelled amino acids seem to reflect tumour infiltration more specifically than conventional methods like magnetic resonance imaging and computed tomography. Automatic tumour delineation based on maximal tumour uptake may cause an overestimation of mean tumour uptake and an underestimation of tumour extension in tumours with circumscribed peaks. The aim of this study was to develop a program for tumour delineation and calculation of mean tumour uptake which takes into account the mean background activity and is thus optimised to the problem of tumour definition in IMT SPET. Using the frequency distribution of pixel intensities of the tomograms a program was developed which automatically detects a reference brain region and draws an isocontour region around the tumour taking into account mean brain radioactivity. Tumour area and tumour/brain ratios were calculated. A three-compartment phantom was simulated to test the program. The program was applied to IMT SPET studies of 20 patients with cerebral gliomas and was compared to the results of manual analysis by three different investigators. Activity ratios and chamber extension of the phantom were correctly calculated by the automatic analysis. A method based on image maxima alone failed to determine chamber extension correctly. Manual region of interest analysis in patient studies resulted in a mean inter-observer standard deviation of 8.7% +/ -6.1% (range 2.7% -25.0%). The mean value of the results of the manual analysis showed a significant correlation to the results of the automatic analysis (r = 0.91, P<0. 0001 for the uptake ratio; r = 0.87, P<0.0001 for the tumour area). We conclude that the algorithm proposed simplifies the calculation of uptake ratios and may be used for observer-independent evaluation of IMT SPET studies. Three-dimensional tumour recognition and transfer to co-registered morphological images based on this program may be useful for the planning of surgical and radiation treatment.