The role of crossmodal competition and dimensional overlap in crossmodal attention switching.

Crossmodal selective attention was investigated in a cued task switching paradigm using bimodal visual and auditory stimulation. A cue indicated the imperative modality. Three levels of spatial S-R associations were established following perceptual (location), structural (numerical), and conceptual (verbal) set-level compatibility. In Experiment 1, participants switched attention between the auditory and visual modality either with a spatial-location or spatial-numerical stimulus set. In the spatial-location set, participants performed a localization judgment on left vs. right presented stimuli, whereas the spatial-numerical set required a magnitude judgment about a visually or auditorily presented number word. Single-modality blocks with unimodal stimuli were included as a control condition. In Experiment 2, the spatial-numerical stimulus set was replaced by a spatial-verbal stimulus set using direction words (e.g., "left"). RT data showed modality switch costs, which were asymmetric across modalities in the spatial-numerical and spatial-verbal stimulus set (i.e., larger for auditory than for visual stimuli), and congruency effects, which were asymmetric primarily in the spatial-location stimulus set (i.e., larger for auditory than for visual stimuli). This pattern of effects suggests task-dependent visual dominance.

Emotional valence and spatial congruency differentially modulate crossmodal processing: an fMRI study.

Salient exogenous stimuli modulate attentional processes and lead to attention shifts-even across modalities and at a pre-attentive level. Stimulus properties such as hemispheric laterality and emotional valence influence processing, but their specific interaction in audio-visual attention paradigms remains ambiguous. We conducted an fMRI experiment to investigate the interaction of supramodal spatial congruency, emotional salience, and stimulus presentation side on neural processes of attention modulation. Emotionally neutral auditory deviants were presented in a dichotic listening oddball design. Simultaneously, visual target stimuli (schematic faces) were presented, which displayed either a negative or a positive emotion. These targets were presented in the left or in the right visual field and were either spatially congruent (valid) or incongruent (invalid) with the concurrent deviant auditory stimuli. According to our expectation we observed that deviant stimuli serve as attention-directing cues for visual target stimuli. Region-of-interest (ROI) analyses suggested differential effects of stimulus valence and spatial presentation on the hemodynamic response in bilateral auditory cortices. These results underline the importance of valence and presentation side for attention guidance by deviant sound events and may hint at a hemispheric specialization for valence and attention processing.

Comparison of cerebral blood flow acquired by simultaneous [15O]water positron emission tomography and arterial spin labeling magnetic resonance imaging.

Until recently, no direct comparison between [(15)O]water positron emission tomography (PET) and arterial spin labeling (ASL) for measuring cerebral blood flow (CBF) was possible. With the introduction of integrated, hybrid magnetic resonance (MR)-PET scanners, such a comparison becomes feasible. This study presents results of CBF measurements recorded simultaneously with [(15)O]water and ASL. A 3T MR-BrainPET scanner was used for the simultaneous acquisition of pseudo-continuous ASL (pCASL) magnetic resonance imaging (MRI) and [(15)O]water PET. Quantitative CBF values were compared in 10 young healthy male volunteers at baseline conditions. A statistically significant (P<0.05) correlation was observed between the two modalities; the whole-brain CBF values determined with PET and pCASL were 43.3±6.1 mL and 51.9±7.1 mL per 100 g per minute, respectively. The gray/white matter (GM/WM) ratio of CBF was 3.0 for PET and 3.4 for pCASL. A paired t-test revealed differences in regional CBF between ASL and PET with higher ASL-CBF than PET-CBF values in cortical areas. Using an integrated, hybrid MR-PET a direct simultaneous comparison between ASL and [(15)O]water PET became possible for the first time so that temporal, physiologic, and functional variations were avoided. Regional and individual differences were found despite the overall similarity between ASL and PET, requiring further detailed investigations.

Combined space and alertness related therapy of visual hemineglect: effect of therapy frequency.

The combined efficacy of space- and alertness related training in chronic hemineglect was tested behaviorally and in a longitudinal fMRI study. Earlier results had shown that both space as well as alertness related training as single intervention methods lead to short term improvement which, however, is not stable for longer time periods. The neurobiological data obtained in these studies revealed differential cortical reorganization patterns for the two training approaches thereby leading to the hypothesis that a combination of both trainings might result in stronger and longer lasting effects. The results of our current study, however, - at least at first glance - do not clearly corroborate this hypothesis, because neither alertness training alone nor the combination with OKS on the group level led to significant behavioral improvement, although four of the six patients after alertness and even more after combined training showed a higher percentage of behavioral improvement than during baseline. Despite the lack of clearcut behavioral training induced improvement we found right parietal or fronto-parietal increase of activation in the imaging data immediately after combined training and at follow-up 3 weeks later. The study design had called for splitting up training time between the two training approaches in order to match total training time with our earlier single training studies. The results of our current study are discussed as a possible consequence of reduced training time and intensity of both training measures under the combined training situation.

Does valence in the visual domain influence the spatial attention after auditory deviants? Exploratory data.

The auditory mismatch responses are elicited in absence of directed attention but are thought to reflect attention modulating effects. Little is known however, if the deviants in a stream of standards are specifically directing attention across modalities and how they interact with other attention directing signals such as emotions. We applied the well-established paradigm of left- or right-lateralized deviant syllables within a dichotic listening design. In a simple target detection paradigm with lateralized visual stimuli, we hypothesized that responses to visual stimuli would be speeded after ignored auditory deviants on the same side. Moreover, stimuli with negative valence in the visual domain could be expected to reduce this effect due to attention capture for this emotion, resulting in speeded responses to visual stimuli even when attention was directed to the opposite side by the auditory deviant beforehand. Reaction times of 17 subjects confirmed the speeding of responses after deviant events. However, reduced facilitation was observed for positive targets at the left after incongruent deviants, i.e., at the right ear. In particular, significant interactions of valence and visual field and of valence and spatial congruency emerged. Pre-attentive auditory processing may modulate attention in a spatially selective way. However, negative valence processing in the right hemisphere may override this effect. Resource allocation such as spatial attention is regulated dynamically by multimodal and emotion information processing.

Comparison of fMRI activation patterns for test and training procedures of alertness and focused attention.

PURPOSE: Behavioural studies of attention training after brain damage have shown that only training procedures specifically related to the impaired attention function lead to significant improvements in the respective attention domain when using psychometric tests addressing these functions. The main objective of this fMRI study was to investigate specific as well as common neural correlates of alertness and focused attention and to assess the degree of neural overlap for two different tasks of the same attention function. METHODS: To investigate how different attention functions are processed, we tested 32 healthy participants using fMRI. Each participant was randomly assigned to the alertness (n = 16) or the focused attention (n = 16) group, where participants underwent two different attention tasks, one being a diagnostic computerized test procedure and the other being a computer-game like training procedure. RESULTS: The present results show similar activation patterns when assessing the same attention function with two different tasks. Activation overlap for test and training tasks of the same attention function was more clear-cut than the activation overlap for two different attention functions. CONCLUSIONS: Clinically validated diagnostic test paradigms and computer game-like training paradigms for both alertness and focused attention activated common brain systems processing the respective attention function. These findings may help to explain the beneficial effect of specifically designed attentional training procedures and the validity of related psychometric tests in detecting specific changes in performance after training of the same attention functions.

Surveillance program for former PCB-exposed workers of a transformer and capacitor recycling company, family members, employees of surrounding companies, and area residents--executive summary.

In a German company polychlorinated biphenyls (PCB)-containing transformers and capacitors were recycled on a large scale. Human biomonitoring revealed a high PCB body burden in workers of the recycling company, in surrounding locations of this plant, in companies in the neighborhood of this plant, and in family members of these employees. In order to clarify whether possible adverse health effects occurred or may occur in the future, a prospective surveillance program was initiated. After an extensive literature search, an interdisciplinary group of experts developed a surveillance program based on current knowledge with respect to possible adverse health effects that might occur in the recycling process of transformers and capacitors. Exposure to various hazardous substances (PCB, polychlorinated dibenzo-p-dioxins and dibenzo-furans [PCDD/F], metals, solvents) was considered. Criteria derived from human biomonitoring results of PCB were used for admission to the program. Participants in the surveillance program are first informed about risks and aims of the program. Subsequently, physicians started a detailed documentation of participants' general and occupational history, with their complaints, diseases, and nutritional habits, as well as information regarding their living areas, by means of a standardized questionnaire. In addition, separate examinations were performed to detect possible neurological, immunological, (neuro)psychological, hormonal, and skin effects. Moreover, DNA exposure as assessed by the comet assay and antioxidative status were determined. The program will be offered at yearly intervals for 3 years, and then at 5 and 10 years after program onset. Until now the program has proved to be feasible, and acceptance among workers and their families has been high. Based on the results, criteria will be developed to define adverse health effects that might be attributable to a hazardous substance exposure.

Mood modulates auditory laterality of hemodynamic mismatch responses during dichotic listening.

Hemodynamic mismatch responses can be elicited by deviant stimuli in a sequence of standard stimuli even during cognitive demanding tasks. Emotional context is known to modulate lateralized processing. Right-hemispheric negative emotion processing may bias attention to the right and enhance processing of right-ear stimuli. The present study examined the influence of induced mood on lateralized pre-attentive auditory processing of dichotic stimuli using functional magnetic resonance imaging (fMRI). Faces expressing emotions (sad/happy/neutral) were presented in a blocked design while a dichotic oddball sequence with consonant-vowel (CV) syllables in an event-related design was simultaneously administered. Twenty healthy participants were instructed to feel the emotion perceived on the images and to ignore the syllables. Deviant sounds reliably activated bilateral auditory cortices and confirmed attention effects by modulation of visual activity. Sad mood induction activated visual, limbic and right prefrontal areas. A lateralization effect of emotion-attention interaction was reflected in a stronger response to right-ear deviants in the right auditory cortex during sad mood. This imbalance of resources may be a neurophysiological correlate of laterality in sad mood and depression. Conceivably, the compensatory right-hemispheric enhancement of resources elicits increased ipsilateral processing.

Neural mechanisms underlying freedom to choose an object.

Previous brain imaging studies identified the neural networks underlying free choice of self-initiated actions. In contrast, the neural mechanisms underlying free choice of external objects remain to be elucidated. In this event-related functional magnetic resonance imaging study, participants had to choose one out of two different single-colored target squares presented at two of three possible locations. In 50% of the trials the choice was either free or specified, which was indicated by a preceding cue. In order to disentangle processes associated with object choice from those related to motor responses, object-response mapping was orthogonally varied. Processes related to the freedom of choice were isolated by means of an adaptive algorithm: based on the subjects individual choices in the free trials, specified trials were continuously generated in a way that matched the free trials in all aspects but the freedom to choose the object. Comparing free and specified trials revealed enhanced neural activity of a bilateral symmetrical network including the dorsolateral prefrontal, medial frontal, and medial parietal cortex. This network overlaps with that shown previously to be associated with free motor selection. It includes the pre-supplementary motor area (pre-SMA), suggesting that this area is rather associated with a supramodal function of initiating choice than with a specific motor function. Neural activity specifically associated with the freedom to choose an object was found bilaterally in the lateral superior parietal cortex. A psychophysiological interaction (PPI) analysis showed increased functional connectivity of this area with bilateral areas of the extrastriate visual cortex.

Staying responsive to the world: modality-specific and -nonspecific contributions to speeded auditory, tactile, and visual stimulus detection.

Sustained responsiveness to external stimulation is fundamental to many time-critical interactions with the outside world. We used functional magnetic resonance imaging during speeded stimulus detection to identify convergent and divergent neural correlates of maintaining the readiness to respond to auditory, tactile, and visual stimuli. In addition, using a multimodal condition, we investigated the effect of making stimulus modality unpredictable. Relative to sensorimotor control tasks, all three unimodal detection tasks elicited stronger activity in the right temporo-parietal junction, inferior frontal cortex, anterior insula, dorsal premotor cortex, and anterior cingulate cortex as well as bilateral mid-cingulum, midbrain, brainstem, and medial cerebellum. The multimodal detection condition additionally activated left dorsal premotor cortex and bilateral precuneus. Modality-specific modulations were confined to respective sensory areas: we found activity increases in relevant, and decreases in irrelevant sensory cortices. Our findings corroborate the modality independence of a predominantly right-lateralized core network for maintaining an alert (i.e., highly responsive) state and extend previous results to the somatosensory modality. Monitoring multiple sensory channels appears to induce additional processing, possibly related to stimulus-driven shifts of intermodal attention. The results further suggest that directing attention to a given sensory modality selectively enhances and suppresses sensory processing-even in simple detection tasks, which do not require inter- or intra-modal selection.

Revealing the functional neuroanatomy of intrinsic alertness using fMRI: methodological peculiarities.

Clinical observations and neuroimaging data revealed a right-hemisphere fronto-parietal-thalamic-brainstem network for intrinsic alertness, and additional left fronto-parietal activity during phasic alertness. The primary objective of this fMRI study was to map the functional neuroanatomy of intrinsic alertness as precisely as possible in healthy participants, using a novel assessment paradigm already employed in clinical settings. Both the paradigm and the experimental design were optimized to specifically assess intrinsic alertness, while at the same time controlling for sensory-motor processing. The present results suggest that the processing of intrinsic alertness is accompanied by increased activity within the brainstem, thalamus, anterior cingulate gyrus, right insula, and right parietal cortex. Additionally, we found increased activation in the left hemisphere around the middle frontal gyrus (BA 9), the insula, the supplementary motor area, and the cerebellum. Our results further suggest that rather minute aspects of the experimental design may induce aspects of phasic alertness, which in turn might lead to additional brain activation in left-frontal areas not normally involved in intrinsic alertness. Accordingly, left BA 9 activation may be related to co-activation of the phasic alertness network due to the switch between rest and task conditions functioning as an external warning cue triggering the phasic alertness network. Furthermore, activation of the intrinsic alertness network during fixation blocks due to enhanced expectancy shortly before the switch to the task block might, when subtracted from the task block, lead to diminished activation in the typical right hemisphere intrinsic alertness network. Thus, we cautiously suggest that--as a methodological artifact--left frontal activations might show up due to phasic alertness involvement and intrinsic alertness activations might be weakened due to contrasting with fixation blocks, when assessing the functional neuroanatomy of intrinsic alertness with a block design in fMRI studies.

Common networks for selective auditory attention for sounds and words? An fMRI study with implications for attention rehabilitation.

PURPOSE: In an fMRI study the functional networks involved in auditory selective attention for sounds and words were investigated. METHODS: 24 healthy volunteers (12 male, 12 female) had to respond to a category of targets (animal sounds vs. musical instruments, spoken names of instruments vs. animals; 6 targets, 12 nontargets) presented via headphones. RESULTS: Under both the sound and word condition besides left superior and middle temporal lobe activation there was bilateral activity in the superior frontal (including the anterior cingulate cortex ACC), middle and inferior frontal and inferior parietal lobes. Under both conditions we also found cerebellar activity. In general there was a high overlap of the related attention networks for both conditions. CONCLUSIONS: The activation patterns revealed a high overlap across stimulus conditions with only slight modulation caused by the quality of the auditory material. For rehabilitation of attention deficits after brain damage this implicates that a single training procedure might address a common network for selective attention deficits under different stimulus conditions.

Alertness and visuospatial attention in clinical depression.

BACKGROUND: Cognitive deficits are a substantial burden in clinical depression. The present study considered dysfunction in the right-hemispheric attention network in depression, examining alertness and visuospatial attention. METHODS: Three computerized visuospatial attention tests and an alertness test were administered to 16 depressive patients and 16 matched healthy controls. RESULTS: Although no significant group effect was observed, alertness predicted reduced visuospatial performance in the left hemifield. Furthermore, sad mood showed a trend towards predicting left visual field omissions. CONCLUSIONS: Decreased alertness may lead to lower left hemifield visuospatial attention; this mechanism may be responsible for a spatial bias to the right side in depression, even though treatment of depression and anxiety may reduce this cognitive deficit.

Modality-specific perceptual expectations selectively modulate baseline activity in auditory, somatosensory, and visual cortices.

Valid expectations are known to improve target detection, but the preparatory attentional mechanisms underlying this perceptual facilitation remain an open issue. Using functional magnetic resonance imaging, we show here that expecting auditory, tactile, or visual targets, in the absence of stimulation, selectively increased baseline activity in corresponding sensory cortices and decreased activity in irrelevant ones. Regardless of sensory modality, expectancy activated bilateral premotor and posterior parietal areas, supplementary motor area as well as right anterior insula and right middle frontal gyrus. The bilateral putamen was sensitive to the modality specificity of expectations during the unexpected omission of targets. Thus, across modalities, detection improvement arising from selectively directing attention to a sensory modality appears mediated through transient changes in pretarget activity. This flexible advance modulation of baseline activity in sensory cortices resolves ambiguities among previous studies unable to discriminate modality-specific preparatory activity from attentional modulation of stimulus processing. Our results agree with predictive-coding models, which suggest that these expectancy-related changes reflect top-down biases--presumably originating from the observed supramodal frontoparietal network--that modulate signal-detection sensitivity by differentially modifying background activity (i.e., noise level) in different input channels. The putamen appears to code omission-related Bayesian "surprise" that depends on the specificity of predictions.

Efficacy of alertness training in a case of brainstem encephalitis: clinical and theoretical implications.

Although attention functions are often impaired after stroke, traumatic brain injury or inflammatory diseases, little is known about the time course and the long-term efficacy of training-induced improvement. The present single case study evaluates the time course and longitudinal stability of attention improvement after alertness training by repeatedly testing the subject between individual training sessions as well as one and seven months after the end of the training. The outpatient (M.P.) trained developed severe alertness deficits following brainstem encephalitis in 2003 without signs of cortical damage, and since then had not achieved full recovery. In 2008, M.P. participated in 15 treatment sessions on 15 separate working days over a period of three weeks. In each session a 45-minute alertness training task was administered, using the CogniPlus ALERT computer training program. Attention performance was assessed by neuropsychological tests four years, one year, and immediately before the therapy after every third training session and three times after the termination of therapy. Furthermore, a self-report questionnaire measured subjective experience of attention in everyday life situations. In order to compare the performance between training sessions, a procedure specialised for psychometric single-case diagnosis was used to analyse the data. Surprisingly, even after three consecutive training sessions, M.P. showed immense improvement in alertness. Furthermore, after two weeks she felt more energetic and more able to concentrate. Six months after the end of the training the improvement remained stable. The unexpectedly fast time course of recovery induced by the training, as well as the stable long-term effects, probably depend on intact cortical structures. In M.P. it appeared that top-down control of the alertness network on impaired brainstem arousal structures had been re-activated by the training procedure and had remained stable across a long time period.

Dynamic changes in functional cerebral connectivity of spatial cognition during the menstrual cycle.

Functional cerebral asymmetries (FCAs) in women have been shown to vary with changing levels of sex hormones during the menstrual cycle. Previous studies have suggested that interhemispheric interaction forms a key component in generating FCAs and it has been shown behaviorally and by functional imaging that interhemispheric interaction changes during the menstrual cycle, at least for a left hemisphere dominant task. We used functional MRI and an analysis of functional connectivity to examine whether changes in right hemisphere advantage for a figure comparison task as found in behavioral studies, are based on comparable mechanisms like those identified for the verbal task. Women were examined three times during the menstrual cycle, during the menstrual, follicular and luteal phases. The behavioral data confirmed the right hemisphere advantage for the figure comparison task as well as changes of the right hemisphere advantage during the menstrual cycle. Imaging data showed cycle phase-related changes in lateralized brain activation within the task-dominant hemisphere and changes in connectivity between nonhomotopic areas of both hemispheres, suggesting that changes in functional brain organization in women during the menstrual cycle are not only restricted to hormone-related changes of interhemispheric inhibition between homotopic areas, as has been proposed earlier, but might additionally apply to changes of neuronal processes within the hemispheres which seem to be modulated by heterotopic functional connectivity between hemispheres.

Evaluation of spatial processing in virtual reality using functional magnetic resonance imaging (FMRI).

While the ecological validity of virtual reality (VR) applications is usually assessed by behavioral data or interrogation, an alternative approach on a neuronal level is offered by brain imaging methods. Because it is yet unclear if 3D space in virtual environments is processed analogically to the real world, we conducted a study investigating virtual spatial processing in the brain using functional magnetic resonance imaging (fMRI). Results show differences in VR spatial brain processing as compared to known brain activations in reality. Identifying differences and commonalities of brain processing in VR reveals limitations and holds important implications for VR therapy and training tools. When VR therapy aims at the rehabilitation of brain function and activity, differences in brain processing have to be taken into account for designing effective VR training tools. Furthermore, for an evaluation of possible restoration effects caused by VR training, it is necessary to integrate information about the brain activation networks elicited by the training. The present study provides an example for demonstrating the benefit of fMRI as an evaluation tool for the mental processes involved in virtual environments.

First nationwide study on driving under the influence of drugs in Switzerland.

In Switzerland, a two-tier system based on impairment by any psychoactive substances which affect the capacity to drive safely and zero tolerance for certain illicit drugs came into force on 1 January 2005. According to the new legislation, the offender is sanctioned if Delta(9)-tetrahydrocannabinol THC is >or=1.5ng/ml or amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyethylamphetamine (MDEA), cocaine, free morphine are >or=15ng/ml in whole blood (confidence interval+/-30%). For all other psychoactive substances, impairment must be proven in applying the so-called "three pillars expertise". At the same time the legal blood alcohol concentration (BAC) limit for driving was lowered from 0.80 to 0.50g/kg. The purpose of this study was to analyze the prevalence of drugs in the first year after the introduction of the revision of the Swiss Traffic Law in the population of drivers suspected of driving under the influence of drugs (DUID). A database was developed to collect the data from all DUID cases submitted by the police or the Justice to the eight Swiss authorized laboratories between January and December 2005. Data collected were anonymous and included the age, gender, date and time of the event, the type of vehicle, the circumstances, the sampling time and the results of all the performed toxicological analyses. The focus was explicitly on DUID; cases of drivers who were suspected to be under the influence of ethanol only were not considered. The final study population included 4794 DUID offenders (4243 males, 543 females). The mean age of all drivers was 31+/-12 years (range 14-92 years). One or more psychoactive drugs were detected in 89% of all analyzed blood samples. In 11% (N=530) of the samples, neither alcohol nor drugs were present. The most frequently encountered drugs in whole blood were cannabinoids (48% of total number of cases), ethanol (35%), cocaine (25%), opiates (10%), amphetamines (7%), benzodiazepines (6%) and methadone (5%). Other medicinal drugs such as antidepressants and benzodiazepine-like were detected less frequently. Poly-drug use was prevalent but it may be underestimated because the laboratories do not always analyze all drugs in a blood sample. This first Swiss study points out that DUID is a serious problem on the roads in Switzerland. Further investigations will show if this situation has changed in the following years.

Energetic effects of stimulus intensity on prolonged simple reaction-time performance.

The efficiency of cognition is modulated by energetic factors like effort, fatigue or circadian variation, which affect even the most basic cognitive operations. For instance, speeded detection in simple reaction-time (SRT) tasks usually slows down over time. The literature suggests that either mindlessness due to routinization or mental fatigue due to attentional resource depletion might underlie this decrement. We tested these assumptions in three 25-min visual SRT tasks using easy-to-detect high-intensity and hard-to-detect low-intensity stimuli presented in both blocked and mixed fashion. Mindlessness theory predicts that less monotonous stimulation (i.e. the mixed presentation) would mitigate the time-related decrement for high- and low-intensity stimuli alike, whereas resource-depletion theory predicts opposite effects of mixed presentation on high- versus low-intensity stimuli. Indeed, stimulus intensity and presentation mode cross-interacted significantly, indicating that the performance decline was steeper for high-intensity stimuli but less steep for low-intensity stimuli during mixed compared to blocked presentation, respectively. These results strongly suggest that the time-related efficiency decrement during prolonged SRT performance is related to accumulating mental fatigue. A conjecture is put forward that explains both resource depletion and mindlessness from the perspective of self-regulation. Our study underscores the need to incorporate energetic factors into models of cognition to facilitate their translation into real-world applications.