Thomas Kaulisch

Electrodynamic headphones and woofers for application in magnetic resonance imaging scanners

Electrodynamic speakers compatible with (functional) magnetic resonance imaging (MRI) are described. The speakers magnets are removed, their function is replaced by the scanners magnetic field, resulting in an uncommon but efficient operation. The method can be used with headphones as well as woofers. Functional MRI is not associated with any known biological risks, but as a method for visualization of task-specific activation of brain regions it is undesirably noisy. Thus, it requires both noise protection and efficient sound transmission systems for delivering acoustic stimuli to subjects. Woofers could possibly be used in active noise-control systems. The speakers described in this paper can be used for either task.

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 emotionalmotor 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.

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.

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 ≈ 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 ≈ 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 ≈ 15% of the entire neocortical surface area throughout development.