Biomedical subjects

Daniel Senkowski

Publications and source records attributed to Daniel Senkowski.

5 recordsLinked to original sources

PubMed2003

Evidence for disturbed cortical signal processing and altered serotonergic neurotransmission in generalized anxiety disorder.

BACKGROUND: Current pathophysiological concepts of generalized anxiety disorder (GAD) assume a disturbed exteroceptive sensory system. Furthermore, central serotonergic neurotransmission has been shown to play an important role in anxiety disorder. Cortical signal processing as measured by auditory evoked potentials (AEPs) may reflect the integrity of the exteroceptive sensory system. Because a special aspect of AEP, the loudness dependence of the N1/P2-component (LD), has been related to central serotonergic activity, the LD may be useful for investigating serotonergic dysfunctions in GAD. METHODS: The LD was recorded in 31 medication-free patients with GAD without any psychiatric co-morbidity and in 31 matched control subjects. Dipole source analysis was performed to separate the LD of regions including the primary (LD-tangential dipole) and regions including the secondary auditory cortex (LD-radial dipole). RESULTS: A shallower LD-tangential was observed in patients with GAD as compared to healthy control subjects [F(1,60) = 6.727, p =.012; one-way analysis of variance]. The LD-radial showed no differences between groups. Severity of the anxiety symptoms was not related to the LDs. CONCLUSIONS: The results indicate an altered exteroceptive sensory system in GAD occurring at the level of the primary but not secondary auditory cortex. Because a shallow LD of the primary auditory cortex was related to a high firing rate of neurons in the dorsal raphe nucleus, the results may support evidence for an enhanced serotonergic activity in GAD.

Acoustic Stimulation↗

PubMed2002

Spatial versus object feature processing in human auditory cortex: a magnetoencephalographic study.

The human visual system is divided into two pathways specialized for the processing of either objects or spatial locations. Neuroanatomical studies in monkeys have suggested that a similar specialization may also divide auditory cortex into two such pathways. We used the identical stimulus material in two experimental sessions in which subjects had to either identify auditory objects or their location. Magnetoencephalograms were recorded and M100 dipoles were fitted into individual brain models. In the right hemisphere, the processing of auditory spatial information lead to more lateral activations within the temporal plane while object identification lead to more medial activations. These findings suggest that the human auditory system processes object features and spatial features in distinct areas.

Acoustic Stimulation↗

PubMed2002

Allelic variants of the functional promoter polymorphism of the human serotonin transporter gene is associated with auditory cortical stimulus processing.

The loudness dependence (LD) of the auditory-evoked N1/P2 component has been shown to be related to the central serotonergic neurotransmission. Allelic variants in the promoter region of the 5-hydroxytryptamine transporter (5-HTT) gene were shown to modulate serotonergic activity. It was hypothesized that the three genotypes (l/l, s/l, s/s) differ with respect to LD. Allelic variants of the 5-HTT promoter region and LD at the Cz electrode were determined in 185 healthy subjects prospectively. A significant association was found between LD and genotype (ANOVA: F=4.172, p=0.017). Individuals homozygous for the l allele exhibited a weaker LD compared to heterozygous subjects. The results are consistent with the reported association between 5-HTT genotype and serotonin transport capacity in lymphoblasts, and indicate that auditory stimulus processing is associated with genetic variants of the brain serotonergic system. The LD may serve as endophenotype in human serotonin research.

Adult↗

PubMed2002

Frontal and temporal dysfunction of auditory stimulus processing in schizophrenia.

Attention deficits have been consistently described in schizophrenia. Functional neuroimaging and electrophysiological studies have focused on anterior cingulate cortex (ACC) dysfunction as a possible mediator. However, recent basic research has suggested that the effect of attention is also observed as a relative amplification of activity in modality-associated cortical areas. In the present study, the question was addressed whether an amplification deficit is seen in the auditory cortex of schizophrenic patients during an attention-requiring choice reaction task. Twenty-one drug-free schizophrenic patients and 21 age- and sex-matched healthy controls were studied (32-channel EEG). The underlying generators of the event-related N1 component were separated in neuroanatomic space using a minimum-norm (LORETA) and a multiple dipole (BESA) approach. Both methods revealed activation in the primary auditory cortex (peak latency approximately 100 ms) and in the area of the ACC (peak latency approximately 130 ms). In addition, the adapted multiple dipole model also showed a temporal-radial source activation in nonprimary auditory areas (peak latency approximately 140 ms). In schizophrenic patients, significant activation deficits were found in the ACC as well as in the left nonprimary auditory areas that differentially correlated with negative and positive symptoms. The results suggest that (1) the source in the nonprimary auditory cortex is detected only with a multiple dipole approach and (2) that the N1 generators in the ACC and in the nonprimary auditory cortex are dysfunctional in schizophrenia. This would be in line with the notion that attention deficits in schizophrenia involve an extended cortical network.

Acoustic Stimulation↗

PubMed2002

Effects of task difficulty on evoked gamma activity and ERPs in a visual discrimination task.

OBJECTIVE: The present study examined oscillatory brain activity of the EEG gamma band and event-related potentials (ERPs) with relation to the difficulty of a visual discrimination task. METHODS: Three tasks with identical stimulus material were performed by 9 healthy subjects. The tasks comprised a passive control task, and an easy and a hard visual discrimination task, requiring discrimination of the color of circles. EEG was recorded from 26 electrodes. A wavelet transform based on Morlet wavelets was employed for the analysis of gamma activity. RESULTS: Evoked EEG gamma activity was enhanced by both discrimination tasks as compared to the passive control task. Within the two discrimination tasks, the latency of the evoked gamma peak was delayed for the harder task. Higher amplitudes of the ERP components N170 and P300 were found in both discrimination tasks as compared to the passive task. The N2b, which showed a maximum activation at about 260 ms, was increased in the hard discrimination task as compared to the easy discrimination task. CONCLUSIONS: Our results indicate that early evoked gamma activity and N2b are related to the difficulty of visual discrimination processes. A delayed gamma activity in the hard task indicated a longer duration of stimulus processing, whereas the amplitude of the N2b directly indicates the level of task difficulty.

Adult↗