Biomedical subjects

Andreas J Fallgatter

Publications and source records attributed to Andreas J Fallgatter.

27 records · Page 2Linked to original sources

PubMed2004

Altered response control and anterior cingulate function in attention-deficit/hyperactivity disorder boys.

OBJECTIVE: To investigate mechanisms and structures underlying prefrontal response control and inhibition in boys suffering from attention-deficit/hyperactivity disorder (ADHD). METHOD: Sixteen boys with ADHD and 19 healthy controls were investigated electrophysiologically during performance of a visual Go-Nogo task (Continuous Performance Test, CPT). An electrophysiological source localization method was employed to further analyze the data. RESULTS: The ADHD boys showed a significantly diminished central Nogo-P3, due to a lack of Nogo-related frontalization of the positive brain electrical field in this group. This two-dimensional effect was associated with a significantly reduced activation of the anterior cingulate cortex (ACC) in the ADHD boys in the Nogo condition of the CPT. Both groups did not significantly differ regarding the amplitude of the Nogo-N2. CONCLUSIONS: The results indicate deficits in prefrontal response control in unmedicated ADHD boys that do not seem to be specifically inhibitory in nature. A supposed dysfunction of the ACC in ADHD was confirmed.

Attention Deficit Disorder with Hyperactivity↗

PubMed2004

Source localization (LORETA) of the error-related-negativity (ERN/Ne) and positivity (Pe).

We investigated error processing of 39 subjects engaging the Eriksen flanker task. In all 39 subjects a pronounced negative deflection (ERN/Ne) and a later positive component (Pe) were observed after incorrect as compared to correct responses. The neural sources of both components were analyzed using LORETA source localization. For the negative component (ERN/Ne) we found significantly higher brain electrical activity in medial prefrontal areas for incorrect responses, whereas the positive component (Pe) was localized nearby but more rostral within the anterior cingulate cortex (ACC). Thus, different neural generators were found for the ERN/Ne and the Pe, which further supports the notion that both error-related components represent different aspects of error processing.

Adult↗

PubMed2004

Encephalopathy and myoclonus triggered by valproic acid.

In recent years, the use of valproic acid (VPA) as a mood-stabilizing agent has continuously increased. Although VPA usually is well tolerated, its use in combination with other psychotropic compounds might bear an elevated risk of adverse reactions. Here, we present the case of a 42-year-old male suffering from treatment-resistant psychotic depression, who was prescribed VPA additionally to lithium, clomipramine, flupentixol and risperidone. By doing so, he developed myoclonus, tremor and encephalopathy with sedation and marked EEG background slowing. Most notably, these side effects occurred in the presence of normal VPA and ammonia serum concentrations. On VPA discontinuation, all symptoms vanished and EEG normalized. We thus suggest that direct VPA-induced encephalopathy in the absence of ammonemia does exist, in this case probably facilitated by psychotropic polypharmacy.

Adult↗

PubMed2004

Allelic variation of serotonin transporter function modulates the brain electrical response for error processing.

A functional length variation in the transcriptional control region of the serotonin transporter gene (5-HTTLPR) influences brain function, personality traits, and susceptibility to psychiatric disorders. Here we measured prefrontal brain function by means of event-related potentials during an error processing paradigm. Physiologically, occurrence of an error elicits two specific electrical responses in the prefrontal cortex, the early error related negativity (Ne/ERN) and the later occurring error positivity (Pe), reflecting different components of error processing. Healthy subjects with one or two copies of the low-activity 5-HTTLPR short variant showed significantly higher amplitudes of the Ne/ERN and a trend to higher amplitudes of the Pe as compared to age- and gender-matched individuals homozygous for the long allele. Performance measures and latencies of these ERP-components did not differ between groups. These results indicate that the 5-HTTLPR short variant is associated with enhanced responsiveness of the brain and further supports the notion that prefrontal brain function is influenced by allelic variation in serotonin transporter function.

Adult↗

PubMed2004

Early-stage face processing dysfunction in patients with schizophrenia.

OBJECTIVE: Deficits in emotional processing are evident in patients with schizophrenia. Since recent studies have indicated dysfunctions in cortical areas involved in face processing, this study investigated the early processing of faces in schizophrenia patients through the use of event-related potentials. METHOD: Event-related potential responses were obtained from 24 schizophrenia patients and 28 healthy comparison subjects who were presented with pictures of faces and pictures of buildings (control stimuli). RESULTS: Schizophrenia patients displayed significantly lower differences in the face-specific N170 component between the face and building pictures than did the healthy comparison subjects. CONCLUSIONS: This finding suggests a dysfunction of early-stage visual processing of faces in patients with schizophrenia.

Adolescent↗

PubMed2003

Reduced response-inhibition in obsessive-compulsive disorder measured with topographic evoked potential mapping.

Recent neuroimaging studies have suggested that a hyperactivity of the frontal-striate neuronal circuits, including the orbitofrontal cortex and the basal ganglia, mediates the symptomatology of obsessive-compulsive disorder (OCD). However, there is also some evidence that the superior frontal cortex is less activated in OCD, and this local hypoactivity has been shown to be negatively associated with the symptomatology. As the superior frontal cortex is believed to be involved in inhibitory control, this study investigated the brain electrical activity during response inhibition in OCD. Twelve patients with OCD and 12 healthy controls performed a cued Go-NoGo task (continuous performance test), while event-related potentials were registered with 21 electrodes. Patients reacted significantly faster than controls, but did not differ from controls regarding the error rate. As a main result, we found a reduced frontal activity during the NoGo condition in OCD, which was condensed in a reduced anteriorisation of the brain electrical field. We suggest that this inhibitory deficit in OCD has a major contribution to the pathophysiology of OCD, which is underscored by the fact that the anteriorisation during the NoGo condition (NGA) was negatively correlated with the symptomatology as measured by the Yale-Brown Obsessive-Compulsive Scale.

Adult↗

PubMed2003

Brain electrical dysfunction of the anterior cingulate in schizophrenic patients.

The anterior cingulate cortex (ACC) is a key region within the human prefrontal cortex that has been shown to be dysfunctional in schizophrenic patients. Supporting evidence for this notion has been collected with neuroimaging methods during various cognitive activation tasks. Recently, electrophysiological ACC activity has been demonstrated by means of a three-dimensional source location with low resolution electromagnetic tomography (LORETA) in the event-related potentials elicited during the NoGo condition of the Continuous Performance Test (CPT) as compared to its Go condition. Thirty-one schizophrenic patients and 31 age- and gender-matched healthy volunteers were investigated with this newly developed electrophysiological method. LORETA analysis revealed a significantly diminished brain electrical activity in the ACC of schizophrenic patients as compared to controls during the NoGo condition of the CPT. This result supports the assumption of a functional deficit of the ACC during this cognitive task as a central feature in schizophrenias and, thereby, specifies the general concept of hypofrontality. Moreover, this investigation underscores the value of sophisticated electrophysiological methods in combination with unambiguously designed mental tasks for the evaluation of the pathophysiological processes underlying schizophrenic diseases.

Adolescent↗

PubMed2002

Face-specific event-related potential in humans is independent from facial expression.

A face-specific brain EEG potential at approximately 160 ms after stimulus presentation has recently been described by various research groups. Most of these studies analysed this face-specific brain potential using smiling faces as stimuli. In electrophysiological studies, however, differences in amplitude due to the emotional valence of the stimuli were described as early as 100 ms after stimulus presentation. In order to investigate the effect of facial expressions with different emotional content on face-specific brain EEG potentials, event-related potentials (ERPs) to faces with sad, happy and neutral expressions were compared to ERPs elicited with buildings in 16 healthy subjects. A face-specific potential at vertex approximately 160 ms after stimulus presentation has been verified in the present study. No significant differences in latency or amplitude of this component were found for different facial expressions.

Adult↗

PubMed2002

Electrophysiological indication for a link between serotonergic neurotransmission and personality in alcoholism.

The serotonergic neurotransmission seems to be involved in the neuropsychobiology of alcoholism. The intensity dependence of the N1/P2 component of auditory-evoked potentials is discussed as an indicator of the central serotonergic neurotransmission in healthy subjects. The aim of this study was to verify this correlation between intensity dependence and serotonergic neurotransmission, as indicated by the personality trait "harm avoidance" (HA) within the Temperament and Character Inventory (TCI) in alcohol-dependent patients. The intensity dependence was measured in 25 alcohol-dependent patients, 10 and 40 days after detoxification. The personality trait HA was assessed, which is supposed to reflect the serotonergic neurotransmission. The intensity dependence was negatively correlated with the temperament trait HA of the TCI (r = - .55, P<.01) at Day 40, but neither on Day 10 nor with the other personality dimensions. We conclude, that the intensity dependence reflects the serotonergic neurotransmission in withdrawn alcohol-dependent patients.

Acoustic Stimulation↗