Biomedical subjects

Roland Kalb

Publications and source records attributed to Roland Kalb.

5 recordsLinked to original sources

PubMed2005

Opposite effects of depression and antidepressants on processing speed and error rate.

Depressions increase reaction times and antidepressant treatment decreases them. Is it possible to get information, how these two conditions affect the stimulus-response pathway? Therefore, auditory and visual, left-hand and right-hand, simple and choice reaction times were measured in 38 patients with depression and 30 healthy control subjects. From these data, the minimal reaction times and the error rates were calculated. In the first study, the reaction times and error rates of patients with depression were correlated with the antidepressant doses. In the second study, the differences between medicated, depressive patients and healthy control subjects were investigated. The result of the first study was that antidepressant doses correlated negatively with reaction times but positively with error rates. In the second study, the patients with depression showed increased reaction times but reduced error rates compared to healthy control subjects. The auditory tasks were more affected than the visual tasks and the minimal reaction times more than the median reaction times. Therefore, we concluded that depression and antidepressant treatment had opposite effects on reaction times and error rates. The findings in minimal reaction times and auditory tasks suggest a special involvement of early cortical auditory processing in depression and antidepressant treatment.

Acoustic Stimulation↗

PubMed2004

Sex differences in simple reaction tasks.

Many anatomical and brain mapping studies show a higher bilateral symmetry of female brains and a higher asymmetry of male brains so correlations between simple visual and auditory, left- and right-hand reaction times were examined for such sex differences. 20 healthy women and 20 men were tested in two sessions. For women all six response times correlated with each other significantly in Session A, but in Session B there were only two significant interhemispheric correlations. This represented different changes in visual and auditory reaction times between Sessions A and B. Men showed the same pattern in both sessions: a significant correlation between the interhemispheric visual reaction times and one between auditory reaction times. Women showed a total correlation pattern in Session A and an interhemispheric correlation pattern in Session B. This was interpreted as a transition between a holistic information-processing strategy in Session A and an analytic strategy in Session B. Men showed an analytic strategy in both sessions.

Adult↗

PubMed2003

Improvement in response times for simple and complex tasks after electroconvulsive therapy.

BACKGROUND: Electroconvulsive therapy (ECT) has gone through fundamental changes since its introduction in 1938 and has developed from a frightening and distrusted procedure into an effective and safe treatment for people with severe psychiatric disorders. This study suggests that ECT has an effect on the response times of simple and complex tasks. METHODS: We had two groups. The first group consisted of eight patients suffering from severe therapy-resistant depression. They were treated with ECT. The second group consisted of eight sex- and age-matched persons who were treated conventionally with antidepressive medication. The authors measured auditory and visual response times of both simple and complex tasks in run A and run B on two different days. In the ECT group, the first measurement took place 1 day before a session of ECT, the second 3 h following a session of ECT. In the depressive control group, the two measurements were performed on two different days but at most within 4 days. RESULTS: The response times of the depressive subjects treated with ECT are prolonged in both run A and run B compared to those of the depressive control group. The response times in run B are reduced compared to run A on the whole. However the reduction is stronger in the ECT group than the one taking place in the depressive control group between the two runs. CONCLUSIONS: The considerable decrease of the response times from run A to run B in the ECT group compared to the depressive control group gives further evidence that ECT has a positive effect on important information processing parameters.

Adult↗

PubMed2003

Symmetry reversal in schizophrenia.

Schizophrenia is associated with cortical asymmetries concentrated in the left fronto-temporal hemisphere. In order to look for functional asymmetries between the two hemispheres, the stimulus-response times of patients were split into smaller periods and the interhemispheric and intrahemispheric correlations between these periods were investigated. Three groups were compared to each other: 22 patients with schizophrenia (Diagnostic and Statistical Manual of Mental Disorders, 4th edn; DSM-IV) treated with neuroleptics; 24 psychiatric neuroleptic-treated patients without schizophrenia; and 30 healthy subjects. All subjects were investigated by simple (one stimulus-one response) and complex (two stimuli-two responses), auditory and visual, right-hemispheric and left-hemispheric stimulus-response tasks. There were no intrahemispheric but significant interhemispheric correlations between the two auditory and between the two visual time fragments in both the healthy and the neuroleptic control group. In contrast there was a significant intrahemispheric correlation between the auditory and visual time fragment in the left hemisphere of patients with schizophrenia and no interhemispheric correlation between the auditory times. The reduction of the interhemispheric auditory correlation is interpreted as an auditory disintegration, the appearance of the left-hemispheric audiovisual correlation as an audiovisual 'hyperintegration' in patients with schizophrenia. It is questionable as to whether these findings are due to schizophrenia or to the neuroleptic treatment.

Acoustic Stimulation↗

PubMed2002

Cuticular hydrocarbons of Tetramorium ants from central Europe: analysis of GC-MS data with self-organizing maps (SOM) and implications for systematics.

Cuticular hydrocarbons were extracted from workers of 63 different nests of five species of Tetramorium ants (Hymenoptera: Formicidae) from Austria, Hungary, and Spain. The GC-MS data were classified (data mining) by self-organizing maps (SOM). SOM neurons derived from primary neuron separation were subjected to hierarchical SOM (HSOM) and were grouped to neuron areas on the basis of vicinity in the hexagonal output grid. While primary neuron separation and HSOM resulted in classifications on a level more sensitive than species differences, neuron areas resulted in chemical phenotypes apparently of the order of species. These chemical phenotypes have implications for systematics: while the chemical phenotypes for T. ferox and T. moravicum correspond to morphological determination, in T. caespitum and T. impurum a total of six chemical phenotypes is found. Three hypotheses are discussed to explain this disparity between morphological and chemical classifications, including in particular the possibility of hybridization and the existence of cryptic species. Overall, the GC-MS profiles classified by SOM prove to be a practical alternative to morphological determination (T. ferox, T. moravicum) and indicate the need to revisit systematics (T. caespitum, T. impurum).

Animals↗