Biomedical subjects

Thomas Kaulisch

Publications and source records attributed to Thomas Kaulisch.

5 recordsLinked to original sources

PubMed2007

Working memory specific activity in auditory cortex: potential correlates of sequential processing and maintenance.

Working memory (WM) tasks involve several interrelated processes during which past information must be transiently maintained, recalled, and compared with test items according to previously instructed rules. It is not clear whether the rule-specific comparisons of perceptual with memorized items are only performed in previously identified frontal and parietal WM areas or whether these areas orchestrate such comparisons by feedback to sensory cortex. We tested the latter hypothesis by focusing on auditory cortex (AC) areas with low-noise functional magnetic resonance imaging in a 2-back WM task involving frequency-modulated (FM) tones. The control condition was a 0-back task on the same stimuli. Analysis of the group data identified an area on right planum temporale equally activated by both tasks and an area on the left planum temporale specifically involved in the 2-back task. A region of interest analysis in each individual revealed that activation on the left planum temporale in the 2-back task positively correlated with the task performance of the subjects. This strongly suggests a prominent role of the AC in 2-back WM tasks. In conjunction with previous findings on FM processing, the left lateralized effect presumably reflects the complex sequential processing demand of the 2-back matching to sample task.

Adult↗

PubMed2004

Orbitofrontal cortical dysfunction in akinetic catatonia: a functional magnetic resonance imaging study during negative emotional stimulation.

Catatonia is a psychomotor syndrome characterized by concurrent emotional, behavioral, and motor anomalies. Pathophysiological mechanisms of psychomotor disturbances may be related to abnormal emotional-motor processing in prefrontal cortical networks. We therefore investigated prefrontal cortical activation and connectivity patterns during emotional-motor stimulation using functional magnetic resonance imaging (FMRI). We investigated 10 akinetic catatonic patients in a postacute state and compared them with 10 noncatatonic postacute psychiatric controls (age-, sex-, diagnosis-, and medication-matched) and 10 healthy controls. Positive and negative pictures from the International Affective Picture System were used for emotional stimulation. FMRI measurements covered the whole frontal lobe, activation signals in various frontal cortical regions were obtained, and functional connectivity between the different prefrontal cortical regions was investigated using structural equation modeling. Catatonic patients showed alterations in the orbitofrontal cortical activation pattern and in functional connectivity to the premotor cortex in negative and positive emotions compared to psychiatric and healthy controls. Catatonic behavioral and affective symptoms correlated significantly with orbitofrontal activity, whereas catatonic motor symptoms were rather related to medial prefrontal activity. It is concluded that catatonic symptoms may be closely related to dysfunction in the orbitofrontal cortex and consequent alteration in the prefrontal cortical network during emotional processing. Because we investigated postacute patients, orbitofrontal cortical alterations may be interpreted as a trait marker predisposing for development of catatonic syndrome in schizophrenic or affective psychosis.

Acute Disease↗

PubMed2003

The growth of cat cerebral cortex in postnatal life: a magnetic resonance imaging study.

To follow up the development of an individual brain over time and to measure its growth we have analysed the brains of individual cats from postnatal day 12 to adulthood using magnetic resonance imaging. From the anatomical images, four parameters were calculated: anteroposterior extent of the telencephalon, brain volume, neocortical surface area and neocortical volume. The development of the anteroposterior extent was similar in all cats. It increased between the 3rd and 6th postnatal week from 33 to 37.5 mm ending up approximately 40 mm in adulthood. The brain volume showed greater variability. On average, the volume increased from 11.5 to 16.5 cm3 in the same period. Adult values were approximately 19 cm3. Considerable interindividual variability was observed in neocortical surface area. In one cat, it expanded from 12.5 to 26 cm2 between days 14 and 41. In another cat, this area expanded from 16 to 24.5 cm2 between days 12 and 40. On average, the surface area expanded by 34% between the 3rd and 6th week. Adult values ranged from 27 to 30 cm2. Neocortical volume increased from 2.9 to 4.1 cm3 between the 3rd and 6th postnatal week and to 4.5-5.2 cm3 in adulthood. The asymmetry between the hemispheres in both neocortical surface area and volume was < 3% in all animals for most of the observation period. Comparison of the neocortical surface measurements with data on postnatal growth of cat primary visual cortex obtained by 2-deoxyglucose autoradiography indicates that the primary visual cortex grows at the same speed and amounts to approximately 15% of the entire neocortical surface area throughout development.

Aging↗

PubMed2003

Noncontact mapping of ventricular tachycardia in a closed-chest animal model of chronic myocardial infarction.

Treatment of ventricular tachyarrhythmias in the setting of chronic myocardial infarction requires accurate characterization of the arrhythmia substrate. New mapping technologies have been developed that facilitate identification and ablation of critical areas even in rapid, hemodynamically unstable ventricular tachycardia. A noncontact mapping system was used to analyze induced ventricular tachycardia in a closed-chest sheep model of chronic myocardial infarction. Twelve sheep were studied 96 +/- 10 days after experimental myocardial infarction. During programmed stimulation, 15 different ventricular tachycardias were induced in nine animals. Induced ventricular tachycardia had a mean cycle length of 190 +/- 30 ms. In 12 ventricular tachycardias, earliest endocardial activity was recorded from virtual electrodes, preceding the surface QRS onset by 30 +/- 7 ms. Noncontact mapping identified diastolic activity in ten ventricular tachycardias. Diastolic potentials were recorded over a variable zone, spanning more than 30 mm. Timing of diastolic potentials varied from early to late diastole and could be traced back to the endocardial exit site. Entrainment with overdrive pacing was attempted in nine ventricular tachycardias, with concealed entrainment observed in seven. Abnormal endocardium in the area of chronic myocardial infarction identified by unipolar peak voltage mapping was confirmed by magnetic resonance imaging. These data suggest that induced ventricular tachycardia in the late phase of myocardial infarction in the sheep model is due to macroreentry involving the infarct borderzone. The combination of this animal model with noncontact mapping technology will allow testing of new strategies to cure and prevent ventricular tachycardia in the setting of chronic myocardial infarction.

Animals↗

PubMed2002

GABA-ergic modulation of prefrontal spatio-temporal activation pattern during emotional processing: a combined fMRI/MEG study with placebo and lorazepam.

Various prefrontal cortical regions have been shown to be activated during emotional stimulation, whereas neurochemical mechanisms underlying emotional processing in the prefrontal cortex remain unclear. We therefore investigated the influence of the GABA-A potentiator lorazepam on prefrontal cortical emotional-motor spatio-temporal activation pattern in a combined functional magnetic resonance imaging/magnetoencephalography study. Lorazepam led to the reversal in orbito-frontal activation pattern, a shift of the early magnetic field dipole from the orbito-frontal to medial prefrontal cortex, and alterations in premotor/motor cortical function during negative and positive emotional stimulation. It is concluded that negative emotional processing in the orbito-frontal cortex may be modulated either directly or indirectly by GABA-A receptors. Such a modulation of orbito-frontal cortical emotional function by lorazepam has to be distinguished from its effects on cortical motor function as being independent from the kind of processing either emotional or nonemotional.

Adult↗