Biomedical subjects

Daniel Brandeis

Publications and source records attributed to Daniel Brandeis.

At least 19 recordsLinked to original sources

PubMed2007

Electrophysiological and hemodynamic evidence for late maturation of hand power grip and force control under visual feedback.

Several human imaging studies have described the neural network involved in power grip under visual control and the subset of cortical areas within this network that are sensitive to force modulation. As there is behavioral evidence for late maturation in even simple hand motor tasks involving visual feedback, we aimed at identifying the neural correlates of these developmental changes. Subjects from three developmental age groups (9-11, 15-17, and adults) performed the same power grip task in both a functional magnetic resonance imaging and an event-related potential (ERP) session. Trials started with a visual target indicating whether to squeeze at 20%, 40%, or 75% of their maximum and online visual feedback on the actual amount of force was provided. Longer reaction times and more shallow slopes of the force curve characterized the behavior of the younger age groups, especially the children. Both neurophysiological methods detected both general as well as force modulation-specific maturational changes. General development was characterized by decreasing ERP amplitudes and increasing deactivation of an extended network, closely resembling the so-called "default" network. The most pronounced developmental changes specific for force control were observed in an ERP component and brain regions involved in feedback processing. In contrast to adult subjects, we found evidence for a stronger dependency on visual feedback information in the younger age groups. Our results also suggest that the ability to deactivate task-irrelevant networks might be a late developmental achievement.

Adolescent↗

PubMed2006

Coarse neural tuning for print peaks when children learn to read.

Adult readers exhibit increased fast N1 activity to wordlike strings in their event-related brain potential. This increase has been linked to visual expertise for print, implying a protracted monotonic development. We investigated the development of coarse neural tuning for print by studying children longitudinally before and after learning to read, and comparing them to skilled adults. The coarse N1 tuning, which had been absent in nonreading kindergarten children, emerged in less than 2 years after the same children had mastered basic reading skills in 2nd grade. The N1 became larger for words than symbol strings in every child, and this coarse tuning was stronger for faster readers. Fast brain processes thus specialize rapidly for print when children learn to read, and play an important functional role in the fluency of early reading. Comparing 2nd graders with adults revealed a further decrease of the coarse N1 tuning in adults, presumably reflecting further reading practice. This constitutes a prominent nonlinear development of coarse neurophysiological specialization for print. The maximum tuning in novice readers possibly reflects the high sensitivity of their neural network for visual aspects of print, and a more selective tuning in expert adult readers.

Adult↗

PubMed2006

Maturation of luminance- and motion-defined form perception beyond adolescence: a combined ERP and fMRI study.

Abilities to discriminate forms defined by motion continue to develop throughout childhood. To investigate late development of the visual motion system, we measured brain activity with event-related EEG potentials (ERPs) and functional magnetic resonance imaging (fMRI) in groups of adolescents (15-17 years) and adults (20-30 years) during a visual form discrimination task--with forms being either defined by motion or luminance contrast. We further explored whether possible developmental changes varied with the degree of motion coherence reflecting maturation specific to global motion processing. Both the fMRI activation patterns and ERP topographies were very similar between adolescents and adults, suggesting that the basic visual networks for processing motion and form are established by the age of 15-17. The ERP response to luminance- and motion-defined forms was dominated by a posterior negativity (N1: 120-270 ms). The N1 of the motion contrast was delayed in adolescents, whereas the N1 of the static condition did not differ between groups. Since the motion-evoked N1 is thought to arise in the middle temporal area MT/V5, our results indicate that visual motion processing in MT continues to get faster, becoming still more efficient during late development. Neither the ERP nor the fMRI results revealed maturation effects specific to motion coherence. This indicates that the specific mechanisms to process global dot motion are already mature in adolescence. The present findings support the view that static perception matures earlier than dynamic perception, and that these visual systems have different developmental courses.

Adolescent↗

PubMed2006

Preserved aspects of cortical foot control in paraplegia.

While several recent imaging studies confirm that motor foot areas can still be activated in complete and chronic paraplegia, it remains unclear whether their functionality is also maintained or declines after years of "non-use". Force control is one of the most important and best investigated functions within the motor cortex. It has been repeatedly reported that the motor cortex is more active when higher forces have to be applied. We thus addressed the question of preserved cortical functions by comparing motor force control patterns in the event-related potentials of 10 motor complete paraplegic subjects and 10 controls after attempted (paraplegic patients)/executed (healthy controls) ballistic foot movements with three different force levels. In addition to the peak amplitudes reflecting force levels, peak latencies were also investigated to elucidate timing as another functional aspect of motor control. No significant group difference was found for the peak latencies, indicating that the timing of motor cortical activation is preserved. Concerning amplitudes, we found preserved cortical modulation of higher forces but distorted low force modulation, especially early after injury. These findings thus suggest that important aspects of cortical control over paralyzed limbs are maintained despite years of "non-use".

Adult↗

PubMed2005

Online measurement of motivational processes: introducing the Continuous Delay Aversion Test (ConDAT).

The Continuous Delay Aversion Test (ConDAT), a new computer task for online monitoring and continuously measuring delay aversion (DA), is introduced. DA is a motivational style related to a shortened delay gradient which is proposed as a major endophenotype of attention deficit hyperactivity disorder (ADHD). It is characterised by avoiding or escaping from delay-rich situations despite the prospects of a reward. In each ConDAT trial the rapidly diminishing reward/delay ratio, which tends asymptotically towards zero, is visually presented on the computer screen. The test subject is permanently confronted with the question whether to quit or to continue the trial in the face of the deteriorating reward/time ratio. An elaborated control of stimuli and responses, including the sending of trigger codes to external recording devices, makes the task useful for neurophysiological or brain imaging experiments. Compared to existing tasks, the ConDAT is more flexible and sensitive due to its asymptotic open-ended trials and the interval-scaled output measure. Pilot data give evidence for satisfactory reliability and external validity of the task.

Attention Deficit Disorder with Hyperactivity↗

PubMed2005

Response inhibition deficits in externalizing child psychiatric disorders: an ERP-study with the Stop-task.

BACKGROUND: Evidence from behavioural studies suggests that impaired motor response inhibition may be common to several externalizing child psychiatric disorders, although it has been proposed to be the core-deficit in AD/HD. Since similar overt behaviour may be accompanied by different covert brain activity, the aim of this study was to investigate both brain-electric-activity and performance measures in three groups of children with externalizing child psychiatric disorders and a group of normal controls. METHODS: A Stop-task was used to measure specific aspects of response inhibition in 10 children with attention-deficit hyperactivity disorder (AD/HD), 8 children with oppositional defiant disorder/conduct disorder (ODD/CD), 11 children with comorbid AD/HD+ODD/CD and 11 normal controls. All children were between 8 and 14 years old. Event-related potentials and behavioural responses were recorded. An initial go-signal related microstate, a subsequent Stop-signal related N200, and performance measures were analyzed using ANCOVA with age as covariate. RESULTS: Groups did not differ in accuracy or reaction time to the Go-stimuli. However, all clinical groups displayed reduced map strength in a microstate related to initial processing of the Go-stimulus compared to normal controls, whereas topography did not differ. Concerning motor response inhibition, the AD/HD-only and the ODD/CD-only groups displayed slower Stop-signal reaction times (SSRT) and Stop-failure reaction time compared to normal controls. In children with comorbid AD/HD+ODD/CD, Stop-failure reaction-time was longer than in controls, but their SSRT was not slowed. Moreover, SSRT in AD/HD+ODD/CD was faster than in AD/HD-only or ODD/CD-only. The AD/HD-only and ODD/CD-only groups displayed reduced Stop-N200 mean amplitude over right-frontal electrodes. This effect reached only a trend for comorbid AD/HD+ODD/CD. CONCLUSION: Following similar attenuations in initial processing of the Go-signal in all clinical groups compared to controls, distinct Stop-signal related deficits became evident in the clinical groups. Both children with AD/HD and ODD/CD showed deficits in behavioural response-inhibition accompanied by decreased central conflict signalling or inhibition processes. Neither behavioural nor neural markers of inhibitory deficits as found in AD/HD-only and ODD/CD-only were additive. Instead, children with comorbid AD/HD+ODD/CD showed similar or even less prominent inhibition deficits than the other clinical groups. Hence, the AD/HD+ODD/CD-group may represent a separate clinical entity.

Journal Article↗

PubMed2005

Evidence for developmental changes in the visual word processing network beyond adolescence.

Late development of specialization in the visual word processing system was examined using event-related potentials (ERP) and functional magnetic resonance imaging (fMRI) of word and symbol string processing in groups of adolescents (15.2-17.3 years) and adults (19.8-30.8 years). We focused our ERP analyses on fast visual activity: the occipital P1 (82-131 ms) modulated by physical stimulus characteristics and the occipito-temporal N1 (132-256 ms) reflecting visual tuning for print. Our fMRI analyses concentrated on basal occipito-temporal activations in the visual word form area VWFA. For words, the correlation of fMRI activation in the VWFA and N1 amplitude confirmed the close relationship of the electrophysiological N1 with metabolic activity in the VWFA. Further support for this relationship came from low resolution electromagnetic tomography localizing the word-specific N1 near the VWFA. Both imaging techniques revealed age-independent differences between words and symbol strings. Late development, however, was preferentially detected with ERPs. Decreases of P1 and N1 amplitudes with age were not limited to words and suggested further maturation of the underlying brain microstructure and function. Following adolescence, decreasing N1 latencies specific to words point to continued specialization of the visual word processing system. Both N1 and fMRI measures correlated with reading performance. In summary, the similarity of global fMRI activation patterns between groups suggests a fully established distribution of the reading network in adolescence, while the decreasing N1 latencies for words indicate protracted fine tuning after adolescence.

Adolescent↗

PubMed2005

Fast, visual specialization for reading in English revealed by the topography of the N170 ERP response.

BACKGROUND: N170 effects associated with visual words may be related to perceptual expertise effects that have been demonstrated for faces and other extensively studied classes of visual stimuli. Although face and other object expertise effects are typically bilateral or right-lateralized, the spatial topography of reading-related N170 effects are often left-lateralized, providing potential insights into the unique aspects of reading-related perceptual expertise. METHODS: Extending previous research in German, we use a high-density channel array to characterize the N170 topography for reading-related perceptual expertise in English, a language with inconsistent spelling-to-sound mapping. N170 effects related to overall reading-related expertise are defined by contrasting responses to visual words versus novel symbol strings. By contrasting each of these conditions to pseudowords, we examined how this reading-related N170 effect generalizes to well-ordered novel letter strings. RESULTS: A sample-by-sample permutation test computed on word versus symbol ERP topographies revealed differences during two time windows corresponding to the N170 and P300 components. Topographic centroid analysis of the word and symbol N170 demonstrated significant differences in both left-right as well as inferior-superior dimensions. Words elicited larger N170 negativities than symbols at inferior occipito-temporal channels, with the maximal effect over left inferior regions often unsampled in conventional electrode montages. Further contrasts produced inferior-superior topographic effects for the pseudoword-symbol comparison and left-lateralized topographic effects for the word-pseudoword comparison. CONCLUSION: Fast specialized perception related to reading experience produces an N170 modulation detectable across different EEG systems and different languages. Characterization of such effects may be improved by sampling with greater spatial frequency recordings that sample inferior regions. Unlike in German, reading-related expertise effects in English produced only partial generalization in N170 responses to novel pseudowords. The topographic inferior-superior N170 differences may reflect general perceptual expertise for orthographic strings, as it was found for words and pseudowords across both languages. The topographic left-right N170 difference between words and pseudowords was only found in English, and may suggest that ambiguity in pronunciating novel pseudowords due to inconsistency in spelling-to-sound mapping influences early stages of letter string processing.

Journal Article↗

PubMed2005

Neurophysiological signs of rapidly emerging visual expertise for symbol strings.

The current study examined whether the repeated visual presentation of novel, meaningless symbol strings triggers rapid changes in event related potentials (ERP). Adult participants performed three versions of a word and symbol string repetition detection task in the same experimental session. Analyses focussed on the occipito-temporal N1 (approximately 150 ms) known to reflect early word-specific processing and stimulus categorisation. While the N1 to words did not change, the occipito-temporal negativity to symbol strings increased over runs and converged with the word N1. Later (approximately 220 ms) more positive occipito-temporal amplitudes to repeated words in the third compared to the first run implied a repetition priming effect. This suggests that symbol string processing changed over time due to visual learning and increased perceptual expertise.

Adult↗

PubMed2005

Electrophysiological evidence for cortical plasticity with movement repetition.

The role of movement repetition and practice has been extensively studied as an aspect of motor skill learning but has rarely been investigated in its own right. As practice is considered a prerequisite for motor learning we expected that even the repetitive execution of a simple movement would rapidly induce changes in neural activations without changing performance. We used 64-channel event-related potential mapping to investigate these effects of movement repetition on corresponding brain activity in humans. Ten healthy right-handed young adults performed a power grip task under visual force control to ensure constant behaviour during the experimental session. The session consisted of two parts intersected by a break. For analysis each part was subdivided into two runs to control for potential attention or fatigue effects, which would be expected to disappear during the break. Microstate analysis revealed that distinct topographies and source configurations during movement preparation, movement execution and feedback integration are responsive to repetition. The observed patterns of changes differed for the three microstates, suggesting that different, repetition-sensitive neural mechanisms are involved. Moreover, this study clearly confirms that movement repetition, in the absence of skill learning, is capable of inducing changes in neural networks.

Adult↗

PubMed2005

The course of neuropsychological functions in children with attention deficit hyperactivity disorder from late childhood to early adolescence.

OBJECTIVE: The aim of this follow-up study was to investigate the course of performance in attentional tasks in children with ADHD and normal controls in late childhood and preadolescence over short periods of time. The development of two dimensions of attention was compared: alertness/arousal and inhibitory control. METHOD: Children with ADHD (N=28) and normal controls (N=25) were examined at three times: at baseline (age mean=10.8 years, SD=1.5), after one year (age mean=12.0 years, SD=1.6), and after 2.6 years (age mean=13.3 years, SD=1.6). They performed two tasks of a computerized battery for attentional performance: Alertness--a test of simple reaction time to visual stimuli contrasting a condition with and without auditory warning signal, and Incompatibility--a test of spatial interference/inhibitory control. Clinical diagnosis according to DSM-III-R criteria was established at time 1 and time 3 by structured diagnostic interviews. RESULTS: In the Alertness task significant group differences regarding increased reaction time variability in ADHD, but not for reaction time itself, were found at time 1 and more pronounced at time 2. At time 3 group differences had disappeared. In the Incompatibility task group differences in number of errors were not observed at time 1, whereas children with ADHD made significantly more errors at time 2 and less pronounced at time 3. The degree of clinical symptom remission after 2.6 years was not related to changes in neuropsychological performance. CONCLUSION: When measuring attentional functions, the selection of an appropriate time window seems to be essential for the detection of group differences between ADHD children and controls, because group differences are most pronounced before adolescence. The different developmental course of selective components of attention should be taken into account.

Adolescent↗

PubMed2005

Emerging neurophysiological specialization for letter strings.

In adult readers, printed words and other letter strings activate specialized visual functions within 200 msec, as evident from neurophysiological recordings of brain activity. These fast, specialized responses to letter strings are thought to develop through plastic changes in the visual system. However, it is unknown whether this specialization emerges only with the onset of word reading, or represents a precursor of literacy. We compared 6-year-old kindergarten children who could not yet read words to adult readers. Both age groups detected immediate repetitions of visually presented words, pseudowords, symbol strings, and pictures during event-related potential (ERP) mapping. Maps from seven corresponding ERP segments in children and adults were analyzed regarding fast (<250 msec) and slow (>300 msec) specialization for letter strings. Adults reliably differentiated words through increased fast (<150 msec) occipito-temporal N1 activity from symbols. Children showed a later, more mid-occipital N1 with marginal word-symbol differences, which were absent in those children with low letter knowledge. Children with high letter knowledge showed some fast sensitivity to letter strings, which was confined to right occipito-temporal sites, unlike the stronger adult N1 specialization. This suggests that a critical degree of early literacy induces some immature, but fast, specialization for letter strings before word reading becomes possible. Children also differentiated words from symbols in later segments through increased right occipito-temporal negativity for words. This slow specialization for letter strings was not modulated by letter knowledge and was absent in adults, possibly reflecting a visual precursor of literacy due to visual familiarity with letter strings.

Adult↗

PubMed2005

The P3 in 'ecstasy' polydrug users during response inhibition and execution.

Substance abuse and associated externalizing disorders are characterized by behavioural disinhibition and low impulse control, with reduced neural inhibition postulated to be the common underlying brain mechanism. The P3 component of event-related potentials (ERPs) is a widely used neurophysiological measure thought to reflect inhibitory brain processes, but as yet has not been assessed in ecstasy users. We recorded ERPs evoked by a Continuous Performance Test (CPT) in 16 current ecstasy polydrug users and 17 controls. The CPT included conditions where a prepared motor response had to be executed (Go) or inhibited (NoGo). Both controls and ecstasy users showed normal, robust patterns of P3 anteriorization and delay in the NoGo compared to the Go condition. Ecstasy users had lower P3 amplitudes at midline electrodes and a less anterior location of NoGo P3 peaks. These effects became weaker after statistically controlling for age, educational level and lifetime cannabis use. While lower P3 amplitudes are consistent with higher levels of neural disinhibition in ecstasy polydrug users, the normal switch pattern between response execution and inhibition, and the less anterior location of the NoGo P3, do not indicate disturbed inhibitory brain mechanisms.

Adult↗

PubMed2003

Altered responses to tone and phoneme mismatch in kindergartners at familial dyslexia risk.

Differences in automatic auditory processing between kindergartners with (n = 31) and without (n = 29) familial dyslexia risk were investigated using frequency and phoneme mismatch negativity (MMN) paradigms with small deviance and short intervals. During an early mismatch response segment children at risk tended to have more mid-frontal positivity than controls, especially to phoneme deviance. Significant group differences were found in the late MMN segment, where the mismatch response of children at risk was attenuated to frequency deviance and less left lateralised to phoneme deviance. This indicates deviant automatic processing of phoneme and simple tone deviance in children at risk. These differences might be just related to the dyslexia risk or more specifically to future reading difficulties and thus be useful for early recognition of dyslexia.

Acoustic Stimulation↗

PubMed2003

Development of the automatic mismatch response: from frontal positivity in kindergarten children to the mismatch negativity.

OBJECTIVE: The automatic event-related potential (ERP) response to auditory deviance typically consists of a frontocentral mismatch negativity (MMN), which has been shown to be quite stable during development. Whereas in some infant studies, positive frontal mismatch responses have been reported instead of a MMN; to date, such positivities have not been reported for older children. METHODS: Oddball sequences with small frequency and phoneme deviance (standard: 1000 Hz, 'ba'; larger deviance: 1060 Hz, 'ta'; smaller deviance: 1030 Hz, 'da') and short intervals (every 0.38 s) were presented to 6-7-year-old children and adults during 43-channel ERP recordings. RESULTS: Children showed a consistent frontal positive mismatch response with posterior negativity (179-207 ms), and adults a frontocentral MMN with mastoid positivity (129-199 ms). This map polarity reversal was reflected by significantly different 3D centroid distributions. Low-resolution electromagnetic tomography (LORETA) revealed temporal mismatch response sources for both age groups and conditions. CONCLUSIONS: Major developmental changes characterise the automatic mismatch response for the small deviances and short intervals used. Source localisation suggests that children's and adults' mismatch responses originated from superior temporal plane generators with similar localisation but opposite polarity. This indicates qualitatively different neurophysiological functioning of the automatic bi-temporal auditory change detectors in children and adults.

Acoustic Stimulation↗

PubMed2003

Clinical course of attention-deficit/hyperactivity disorder from childhood toward early adolescence.

OBJECTIVE: To study the course of attention-deficit/hyperactivity disorder (ADHD) in late childhood to adolescence using a multi-informant and multi-assessment procedure. METHOD: Subjects were 35 children with ADHD and 35 matched controls with a mean age of 10 years at first assessment. DSM-III-R-based structured diagnostic interviews and behavioral questionnaires based on parents, teachers, and youth informants were used. Cross-informant behavioral syndromes were obtained by use of the Child Behavior Checklist, the Teacher's Report Form, and the Youth Self-Report. Subjects were reassessed after 1.5 and 2.6 years. RESULTS: Behavioral differences between the two groups were significant for the majority of scales for all three informants at all three times. Diagnostic interviews revealed a persistence rate of 46% over 2.6 years. However, there were only few significant behavioral differences across informants between the nonpersistent and the persistent groups. The fit between interview-derived syndrome scores reflecting subtypes of ADHD and both parents and youth questionnaire data was good, whereas for the teacher ratings it was poor. A high rate of 89% correct classification of the outcome diagnoses was possible based on behavioral data at time 1. CONCLUSIONS: The study of the course of ADHD should be based both on interview and questionnaire data and should include several informants. Operationally defined diagnoses alone may lead to an underestimation of persistent behavioral problems.

Adolescent↗

PubMed2003

Association of ADHD and conduct disorder--brain electrical evidence for the existence of a distinct subtype.

BACKGROUND: To evaluate the impact of psychopathological comorbidity with oppositional defiant/conduct disorder (ODD/CD) on brain electrical correlates in children with attention deficit hyperactivity disorder (ADHD) and to study the pathophysiological background of comorbidity of ADHD+ODD/CD. METHOD: Event-related potentials (ERPs) were recorded during a cued continuous performance test (CPT-A-X) in children (aged 8 to 14 years) with ICD-10 diagnoses of either hyperkinetic disorder (HD; n = 15), hyperkinetic conduct disorder (HCD; n = 16), or ODD/CD (n = 15) and normal children (n = 18). HD/HCD diagnoses in all children were fully concordant with the DSM-IV diagnosis of ADHD-combined type. ERP-microstates, i.e., time segments with stable brain electrical map topography were identified by adaptive segmentation. Their characteristic parameters and behavioral measures were further analyzed. RESULTS: Children with HD but not comorbid children showed slower and more variable reaction times compared to control children. Children with HD and ODD/CD-only but not comorbid children displayed reduced P3a amplitudes to cues and certain distractors (distractor-X) linked to attentional orienting. Correspondingly, global field power of the cue-CNV microstate related to anticipation and preparation was reduced in HD but not in HCD. Topographical alterations of the HD occurred already in the cue-P2/N2 microstate. In sum, the comorbid group was less deviant than both the HD-group and the ODD/CD-group. CONCLUSIONS: The findings suggest that HD children (ADHD-combined type without ODD/CD) suffer from a more general deficit (e.g., suboptimal energetical state regulation) including deficits of attentional orienting and response preparation than just a responseinhibitory deficit, backing the hypothesis of an involvement of a dysregulation of the central noradrenergic networks. The results contradict the hypothesis that ADHD+ODD/CD represents an additive co-occurrence of ADHD and ODD/CD and strongly suggest that it represents a separate pathological entity as considered in the ICD-10 classification system, which differs from both HD and ODD/CD-only.

Adolescent↗

PubMed2002

Correspondence of event-related potential tomography and functional magnetic resonance imaging during language processing.

Combining event-related potentials (ERP) and functional magnetic resonance imaging (fMRI) may provide sufficient temporal and spatial resolution to clarify the functional connectivity of neural processes, provided both methods represent the same neural networks. The current study investigates the statistical correspondence of ERP tomography and fMRI within the common activity volume and time range in a complex visual language task. The results demonstrate that both methods represent similar neural networks within the bilateral occipital gyrus, lingual gyrus, precuneus and middle frontal gyrus, and the left inferior and superior parietal lobe, middle and superior temporal gyrus, cingulate gyrus, superior frontal gyrus and precentral gyrus. The mean correspondence of both methods over subjects was significant. On an individual basis, only half of the subjects showed significantly corresponding activity patterns, suggesting that a one-to-one correspondence between individual fMRI activation patterns and ERP source tomographies integrated over microstates cannot be assumed in all cases.

Adult↗