Communicative impairment and its neural correlates in Alzheimer's disease and frontotemporal dementia.

OBJECTIVE: Communication skills can deteriorate in neurodegenerative diseases such as Alzheimer's disease (AD) and frontotemporal dementia (FTD); however, their clinical assessment and treatment in patient care can be challenging. In the present study, we aimed to quantify the distinctive communication resources and barriers reported by patients and their relatives in AD and FTD and associated these communicative characteristics with clinical parameters, such as the degree of cognitive impairment and atrophy in language-associated brain areas. METHODS: We assessed self-reported communication barriers and resources in 33 individuals with AD and FTD through an interview on daily-life communication, using the Aachener KOMPASS questionnaire. We correlated reported communication barriers and resources with atrophy from high-resolution 3T brain magnetic resonance imaging, neuropsychological assessment, and neurodegenerative markers from cerebrospinal fluid. RESULTS: Communicative impairment was higher in FTD compared to AD. Increased reported communication barriers in our whole sample were associated with the atrophy rate in the left middle temporal lobe, a critical site within the neuronal language network, and with depressive symptoms as well as the semantic word fluency from neuropsychological assessment. The best model for prediction of communicative impairment included the diagnosis (AD or FTD), semantic word fluency, and depressive symptoms. CONCLUSIONS: Our study demonstrates that communication barriers and resources can be successfully assessed via a structured interview based on self-report and report of patients' relatives in practice and are reflected in neuroimaging specific for AD and FTD as well as in further clinical parameters specific for these neurodegenerative diseases. This can potentially open new treatment options for clinical practice and patient care.

Occupational exposure to polychlorinated biphenyls: Development of neuropsychological functions over time.

Occupational exposure to polychlorinated biphenyls (PCBs) continues to affect the health of exposed individuals until today. This study aims to expand previous findings by examining the development of neuropsychological functions of occupationally exposed participants over time. Especially verbal fluency and sensorimotor processing, found to be impaired in a previous study, were thus of particular interest. A total of 116 participants, who were part of the HELPcB cohort, underwent a neuropsychological test battery covering a multitude of cognitive functions. Plasma PCB levels were determined for each participant and classified as elevated or normal based on comparative values drawn from the German general population. Two structural equation models were then used to examine the effects of elevated PCB levels on neuropsychological functions. Results suggest that participants who displayed increased PCB plasma levels continued to show impairments in verbal fluency but not in sensorimotor processing after a second examination one year after the first measurement. Specifically, low chlorinated PCBs are associated with impaired verbal fluency, as compared to high-chlorinated and dioxin-like congeners. Alteration of dopamine concentration in response to PCB exposure might be a potential explanation of this result.

Cognitive functioning in postural orthostatic tachycardia syndrome among different body positions: a prospective pilot study (POTSKog study).

PURPOSE: Approximately 96% of patients with postural orthostatic tachycardia syndrome (PoTS) report cognitive complaints. We investigated whether cognitive function is impaired during sitting and active standing in 30 patients with PoTS compared with 30 healthy controls (HCs) and whether it will improve with the counter manoeuvre of leg crossing. METHODS: In this prospective pilot study, patients with PoTS were compared to HCs matched for age, sex, and educational level. Baseline data included norepinephrine plasma levels, autonomic testing and baseline cognitive function in a seated position [the Montreal Cognitive Assessment, the Leistungsprüfsystem (LPS) subtests 1 and 2, and the Test of Attentional Performance (TAP)]. Cognitive functioning was examined in a randomized order in supine, upright and upright legs crossed position. The primary outcomes were the cognitive test scores between HCs and patients with PoTS at baseline testing, and among the different body positions. RESULTS: Patients with PoTS had impaired attention (TAP median reaction time) in the seated position and impaired executive functioning (Stroop) while standing compared with HC. Stroop was influenced by position (supine versus upright versus upright legs crossed) only in the PoTS group. Leg crossing did not result in an improvement in executive function. In patients with PoTS, there was a negative correlation of Stroop with norepinephrine plasma levels while standing. CONCLUSION: Compared with HCs, PoTS participants showed impaired cognitive attention and executive function in the upright position that did not improve in the legs crossed position. Data provide further evidence for orthostatic cognitive deterioration in patients with PoTS. TRIAL REGISTRATION INFORMATION: The study was registered at ClinicalTrials.gov (NCT03681080).

Connectivity Patterns in the Core Resting-State Networks and Their Influence on Cognition.

Introduction: Three prominent resting-state networks (rsNW) (default mode network [DMN], salience network [SN], and central executive network [CEN]) are recognized for their important role in several neuropsychiatric conditions. However, our understanding of their relevance in terms of cognition remains insufficient. Materials and Methods: In response, this study aims at investigating the patterns of different network properties (resting-state activity [RSA] and short- and long-range functional connectivity [FC]) in these three core rsNWs, as well as the dynamics of age-associated changes and their relation to cognitive performance in a sample of healthy controls (N = 74) covering a large age span (20-79 years). Using a whole-network based approach, three measures were calculated from the functional magnetic resonance imaging (fMRI) data: amplitude of low-frequency fluctuations (ALFF), regional homogeneity (ReHo), and degree of network centrality (DC). The cognitive test battery covered the following domains: memory, executive functioning, processing speed, attention, and visual perception. Results: For all three fMRI measures (ALFF, ReHo, and DC), the highest values of spontaneous brain activity (ALFF), short- and long-range connectivity (ReHo, DC) were observed in the DMN and the lowest in the SN. Significant age-associated decrease was observed in the DMN for ALFF and DC, and in the SN for ALFF and ReHo. Significant negative partial correlations were observed for working memory and ALFF in all three networks, as well as for additional cognitive parameters and ALFF in CEN. Discussion: Our results show that higher RSA in the three core rsNWs may have an unfavorable effect on cognition. Conversely, the pattern of network properties in healthy subjects included low RSA and FC in the SN. This complements previous research related to the three core rsNW and shows that the chosen approach can provide additional insight into their function. Impact statement Using a whole network-based approach, our study characterizes the normal patterns (including resting-state activity [RSA], short- and long-range functional connectivity [FC]) of three prominent resting-state networks (rsNW) within the context of age-dependent changes and explores their relevance for different cognitive domains. Our results revealed a pattern with low RSA and FC in the salience network in healthy volunteers, whereas higher RSA, particularly in the central executive network, seemed to have a negative effect on cognition. These results increase the knowledge about the three core rsNWs and the understanding about their relevance for cognition.

Adverse health effects of PCBs on fine motor performance - Analysis of a neurophysiological pathway in the HELPcB surveillance program.

Since research literature indicates neurotoxic health effects of polychlorinated biphenyls (PCBs), it is necessary to identify by which mechanism PCBs might affect the human central nervous system and human behavior. In the present study, a neurophysiological pathway is assumed to explain the negative association of PCB exposure and performance in fine motor tasks mediated by the level of the dopamine (DA) metabolite homovanillic acid (HVA). A total of 113 occupationally PCB exposed workers and their relatives from an occupational health monitoring program were examined (89.4 % men). PCBs were analyzed in plasma via human biomonitoring and HVA was assessed in urine. The motor performance series was used to measure two dimensions of fine motor skills with 5 subgroups (accuracy: steadiness, line tracking accuracy; speed: line tracking speed, aiming, tapping). The direct effects of PCBs on fine motor performance and the indirect effects of PCBs on fine motor performance via DA metabolite HVA were tested with multiple regressions. We found significant effects for the accuracy dimension, namely a negative direct effect of PCBs on line tracking accuracy mediated by HVA. Further, an indirect effect could be found for PCBs with steadiness accuracy through HVA. There were no significant effects related to fine motor performances in the speed dimension. These results provide first indications for an underlying neurochemical pathomechanism involving the dopamine system of PCB-related deterioration of fine motor performance regarding accuracy.

Polychlorinated biphenyls and depression: cross-sectional and longitudinal investigation of a dopamine-related Neurochemical path in the German HELPcB surveillance program.

BACKGROUND: Exposure to polychlorinated biphenyls (PCBs) is associated with depressive symptomatology. A cause of depressive symptoms is a disturbance in the neurotransmitter system of dopamine (DA). Animal as well as human studies report that PCBs can influence the DA system. This study examined whether PCB-related depressive symptoms are affected by DA metabolites in humans with high PCB body burden. METHODS: This study is part of the German HELPcB surveillance program (Health Effects in high Level exposure to PCB) for occupationally exposed workers and their relatives. Data was collected from 178 participants on two measurement time points (t1 and t2) with a one-year time lag in between the two time points. PCBs were analyzed in plasma via human biomonitoring and a validated questionnaire was used to identify existence and severity of depressive symptoms. As a surrogate for DA, we measured its metabolites homovanillic acid (HVA) and vanillylmandelic acid (VMA) in urine. Mediation analyses were performed to test whether the association between PCB exposure and severity of depressive symptoms is mediated by urinary concentration of DA metabolites HVA and VMA. The mediation was tested with the SPSS macro MEDIATE. RESULTS: We found a significant mediation over time for lower-chlorinated, higher-chlorinated and dioxin-like PCBs. The positive association between PCB exposure with severity of depressive symptoms was mediated by the main DA metabolite HVA. At t1 a higher exposure with PCBs was associated with lower concentration in urinary HVA. A reduced HVA concentration at t1 was correlated with increased depressive symptoms severity at t2. No meditations were found for VMA. CONCLUSIONS: This work indicates that the association of PCB exposure and an increase of depressive symptoms after one year is mediated by the DA metabolite HVA as a surrogate for DA. These are first steps towards finding an explanation for an underlying neurochemical pathomechanism of PCB-related depressive symptomatology.

Dissociated Crossed Speech Areas in a Tumour Patient.

In the past, the eloquent areas could be deliberately localised by the invasive Wada test. The very rare cases of dissociated crossed speech areas were accidentally found based on the clinical symptomatology. Today functional magnetic resonance imaging (fMRI)-based imaging can be employed to non-invasively localise the eloquent areas in brain tumour patients for therapy planning. A 41-year-old, left-handed man with a low-grade glioma in the left frontal operculum extending to the insular cortex, tension headaches, and anomic aphasia over 5 months underwent a pre-operative speech area localisation fMRI measurement, which revealed the evidence of the transhemispheric disposition, where the dominant Wernicke speech area is located on the left and the Broca's area is strongly lateralised to the right hemisphere. The outcome of the Wada test and the intraoperative cortico-subcortical stimulation mapping were congruent with this finding. After tumour removal, language area function was fully preserved. Upon the occurrence of brain tumours with a risk of impaired speech function, the rare dissociate crossed speech areas disposition may gain a clinically relevant meaning by allowing for more extended tumour removal. Hence, for its identification, diagnostics which take into account both brain hemispheres, such as fMRI, are recommended.

Effect of sleep deprivation and low arousal on eye movements and spatial attention.

Research on the neural underpinnings of attention repeatedly revealed a predominant role of the right hemisphere for alertness and visuo-spatial attention. Furthermore, previous studies demonstrated an impairment of covert attentional orienting to the left with reduced alertness or time-on-task. However, recent and preliminary evidence suggests that this arousal-dependent attentional asymmetry cannot be observed in overt orienting. Thus, in the present study we repeatedly measured eye movements in experimental paradigms with varying attentional demands repeatedly every 4h over 24h in total in healthy subjects undergoing sleep deprivation. The main focus was the effect of low arousal induced by sleep deprivation on saccadic reaction times and peak velocity to left-sided and right-sided peripheral targets. Overall, we did not find any directional effects of low arousal on horizontal eye movements. By contrast, low arousal led to a direction-unspecific effect on attentional disengagement when a subsequent saccade had to be initiated. Furthermore, a detrimental effect of reduced arousal on peak velocity of saccades was observed whereas saccadic reaction times were mainly spared. Our results point to a neural non-overlap of brain structures representing covert and overt orienting and a differential vulnerability to variations of the norepinephrine system. This also fits with the reported dissociation of stimulus- and goal-driven attentional functions in visual hemineglect.

Time-of-day variation of visuo-spatial attention.

Time-of-day variation of visuo-spatial attention in relation to body temperature and subjective arousal was assessed. At five different times of day, alertness, covert, and overt orienting of attention were assessed in fifteen healthy subjects. Based on previous studies reporting a tight coupling of alerting and orienting the present study investigates potential attentional asymmetries induced by diurnal variations of arousal. Both covert and overt orienting of attention improved in the course of the day. However, no asymmetries between left and right visual hemifields could be detected. Covert orienting additionally covaried with body temperature, indicating a quite close relation between the attentional arousal and orienting system. Conversely, overt orienting only improved due to repeated testing but did not correlate with body temperature suggesting a partial independence of both modes of attentional orienting. It can be assumed that due to limited diurnal variations of arousal in the participants and practice effects caused by repeated testing, no attentional asymmetries could be provoked.

Add-on Effects of Repetitive Transcranial Magnetic Stimulation on Subacute Aphasia Therapy: Enhanced Improvement of Functional Communication and Basic Linguistic Skills. A Randomized Controlled Study.

OBJECTIVE: To determine to what extent repetitive transcranial magnetic stimulation (rTMS) combined with speech and language therapy improves functional communication and basic linguistic skills of individuals with subacute aphasia. DESIGN: Randomized, blinded, and sham-controlled study. SETTING: Neurologic rehabilitation hospital. PARTICIPANTS: Participants (N=30) with subacute aphasia after stroke. INTERVENTIONS: During a 2-week treatment period, half of the participants received 10 sessions of 20-minute inhibitory 1-Hz rTMS over the right inferior frontal gyrus (Brodmann area 45), and the other half received sham stimulation. Directly thereafter, all the participants underwent 45 minutes of speech and language therapy. MAIN OUTCOME MEASURES: Aachen Aphasia Test, Amsterdam-Nijmegen Everyday Language Test (ANELT), a naming screening, and subscales of the FIM, all assessed the day before and the day after treatment period. RESULTS: The participants who received real rTMS significantly improved with respect to all 10 measures of basic linguistic skills and functional communication, whereas sham-treated participants significantly improved in only 6 of 10 measures (paired t tests, P<.05). There was a significant difference in the gains made by the 2 groups on 5 of 10 measures including functional communication (ANELT) (repeated-measures analysis of variance, P≤.05). CONCLUSIONS: For the first time, this study has demonstrated that basic linguistic skills as well as functional communication are bolstered by combining rTMS and behavioral language therapy in patients with subacute aphasia.

Differential Effects of Lowered Arousal on Covert and Overt Shifts of Attention.

Based on previous studies demonstrating detrimental effects of reduced alertness on attentional orienting our study seeks to examine covert and overt attentional orienting in different arousal states. We hypothesized an attentional asymmetry with increasing reaction times to stimuli presented to the left visual field in a state of maximally reduced arousal. Eleven healthy participants underwent sleep deprivation and were examined repeatedly every 4 hr over 28 hr in total with two tasks measuring covert and overt orienting of attention. Contrary to our hypothesis, a reduction of arousal did not induce any asymmetry of overt orienting. Even in participants with profound and significant attentional asymmetries in covert orienting no substantial reaction time differences between left- and right-sided targets in the overt orienting task could be observed. This result is not in agreement with assumptions of a tight coupling of covert and overt attentional processes. In conclusion, we found differential effects of lowered arousal induced by sleep deprivation on covert and overt orienting of attention. This pattern of results points to a neuronal non-overlap of brain structures subserving these functions and a differential influence of the norepinephrine system on these modes of spatial attention.

Evidence of the sensitivity of the MoCA alternate forms in monitoring cognitive change in early Alzheimer's disease.

BACKGROUND/AIMS: There is an increasing interest in using the Montreal Cognitive Assessment (MoCA) test as a monitoring tool in Alzheimer's disease (AD) in both research and clinical settings. Our aim was to investigate the utility of alternate forms of the MoCA in detecting cognitive deterioration in a sample of early AD patients followed longitudinally in an outpatient memory clinic. METHOD: Twenty-five patients with early-stage AD (prodromal or mild dementia) were administered the original version and one of two previously validated alternate forms of the MoCA within an interval of about 1 year. The decline over time and the rate of change of the MoCA were compared to the total score of a standardized neuropsychological assessment battery (Consortium to Establish a Registry of Alzheimer's Disease; CERAD-Plus). Responsiveness to change was determined by calculating standard response means and the respective effect sizes. RESULTS: Sixty percent of the sample showed a clinical decline on the clinical dementia rating (CDR) scale. There was significant deterioration in the MoCA and CERAD total scores. CONCLUSION: The results demonstrate that the MoCA is capable of detecting change over time and seems to be a valid tool with small to moderate sensitivity for monitoring cognitive change in early AD.

Cognitive effects of deep brain stimulation for essential tremor: evaluation at 1 and 6 years.

Only a few studies have explored cognitive changes with deep brain stimulation (DBS) in patients with essential tremor (ET). Furthermore, the cognitive effects after years of electrical stimulation are unknown. Assessing the impact of stereotactic electrode implantation and the actual electrical stimulation on cognition in patients with ET in the short and long term is of interest, because DBS is increasingly applied and can offer deeper insight into human brain functions. We examined nine ET patients before surgery (PRE-SURGERY), and 1 and 6 years thereafter with DBS switched on (DBS-ON) and off (DBS-OFF). Standardized neuropsychological tests and reaction time tests were applied. There were no differences in tasks of verbal fluency, memory, and executive and intellectual functions comparing PRE-SURGERY, DBS-ON, and DBS-OFF at 1 and 6 years post-surgery. Imaging data revealed that the dorsolateral prefrontal cortex and mamillo-thalamic tracts crucial for cognitive functioning were spared by electrode implantation. Additionally, with electrodes targeting the thalamus and adjacent subthalamic area, the actual electrical stimulation did not affect neuropsychological functioning. However, lesions caused by electrode implantation led to an increase in simple reaction time, while the actual electrical stimulation restored impaired reaction time. This is the second largest study of neuropsychological functioning in patients with ET treated with DBS, and the first covering a neuropsychological long-term follow-up over 6 years. Neither stereotactic surgery nor electrical stimulation affected higher cognitive processes. This study proposes that cerebello-thalamo-cortical pathways in humans are involved in tasks of simple reaction time.

Fine motor skills in adult Tourette patients are task-dependent.

BACKGROUND: Tourette syndrome is a neuropsychiatric disorder characterized by motor and phonic tics. Deficient motor inhibition underlying tics is one of the main hypotheses in its pathophysiology. Therefore the question arises whether this supposed deficient motor inhibition affects also voluntary movements. Despite severe motor tics, different personalities who suffer from Tourette perform successfully as neurosurgeon, pilot or professional basketball player. METHODS: For the investigation of fine motor skills we conducted a motor performance test battery in an adult Tourette sample and an age matched group of healthy controls. RESULTS: The Tourette patients showed a significant lower performance in the categories steadiness of both hands and aiming of the right hand in comparison to the healthy controls. A comparison of patients' subgroup without comorbidities or medication and healthy controls revealed a significant difference in the category steadiness of the right hand. CONCLUSIONS: Our results show that steadiness and visuomotor integration of fine motor skills are altered in our adult sample but not precision and speed of movements. This alteration pattern might be the clinical vignette of complex adaptations in the excitability of the motor system on the basis of altered cortical and subcortical components. The structurally and functionally altered neuronal components could encompass orbitofrontal, ventrolateral prefrontal and parietal cortices, the anterior cingulate, amygdala, primary motor and sensorimotor areas including altered corticospinal projections, the corpus callosum and the basal ganglia.

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.

Alternate-form reliability of the Montreal cognitive assessment screening test in a clinical setting.

AIMS: The Montreal Cognitive Assessment (MoCA) has gained recognition for its validity in detecting cognitive impairment in several clinical populations. For serial assessments, alternate forms are needed to overcome possible practice effects. Our objective was to investigate the reliability of two German MoCA alternate forms for longitudinal assessment applications. METHODS: The original and one of two alternate forms of the MoCA were administered within a 60-min interval of a clinical interview in a counterbalanced order to 100 healthy elderly controls, 30 patients with mild cognitive impairment (MCI) and 30 patients with Alzheimer's disease (AD). The diagnosis of the majority of patients was supported by in vivo AD pathology biomarkers. RESULTS: There was a strong correlation between the alternate forms and the original MoCA in all groups, but particularly in the clinical samples. Total mean scores did not differ significantly between the MoCA versions, even taking into account the presentation order. As in previous studies, age and education influenced performance in the MoCA. The same pattern of group differences (controls > MCI > AD) was observed for each of the versions. CONCLUSION: All three forms can be reliably and interchangeably used in serial cognitive assessment, confirming the MoCA's applicability in research and clinical longitudinal approaches.

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.

Horizontal and vertical pseudoneglect in peri- and extrapersonal space.

The present study investigates the influence of depth on pseudoneglect in healthy young participants (n=18) within three-dimensional virtual space, by presenting a variation of the greyscales task and a landmark task, which were specifically matched for stimulus-response compatibility, as well as perceptual factors within and across the tasks. Tasks were presented in different depth locations (peripersonal, extrapersonal) and different orientations (horizontal, vertical) within three-dimensional virtual space, using virtual reality technique. A horizontal leftward bias (pseudoneglect) for both tasks was found, which was stronger in peripersonal than in extrapersonal space. For the vertical condition, an upward bias was observed in the greyscales task, but not in the landmark task. These results support the hypotheses of right hemispheric dominance for visual spatial attention and our study is the first to examine horizontal and vertical orienting biases with the greyscales task in peri- and extrapersonal space. Furthermore, the differences in attentional asymmetries with respect to depth suggest dissociable neural mechanisms for visual attentional processing in near and far space and the lack of significant correlations implies independence of horizontal and vertical stimulus processing.

Predictive validity of attentional functions in differentiating children with and without ADHD: a componential analysis.

AIM: The objective of this study was to investigate which attentional components are of predictive utility in differentiating children with attention-deficit-hyperactivity disorder, combined type (ADHD-C) from their peers without ADHD. METHODS: Thirty-four children participated in the study: 17 males with ADHD-C (mean age 10y 4mo, SD 1y 9mo) and 17 comparison children (12 males, 5 females; mean age 10y 8mo, SD 1.7y). Attentional functions were assessed using a computer-administered, child-friendly test series in German (i.e. Testbatterie zur Aufmerksamkeitsprüfung für Kinder; KITAP). The KITAP measures several attentional components, including alertness and executive attention (inhibition, divided attention, flexibility). RESULTS: The variable best able to discriminate between children with and without ADHD-C was found to be response time variability in a go/no go task, followed by, in order, number of errors in a divided attention task and response time variability in an alertness task. However, group discrimination was not facilitated by differences in either response latency or accuracy of response in visuospatial attention and attentional flexibility tasks. INTERPRETATION: The assessment of attentional functions proved to be a powerful instrument for discriminating between children with and without ADHD-C. Notably, the discriminative power of executive attention was found to be task dependent and dependent on processing demands.