Biomedical subjects

Klemens Gutbrod

Publications and source records attributed to Klemens Gutbrod.

2 recordsLinked to original sources

PubMed2003

Thalamic stimulation for tremor. Subtle changes in episodic memory are related to stimulation per se and not to a microthalamotomy effect.

The aim of this study was to investigate the impact of unilateral deep brain stimulation (DBS) of the ventrointermediate (Vim) thalamic nucleus on neuropsychological functioning comparing stimulation-on with stimulation-off conditions. Nine patients [five patients with Parkinson's Disease (PD), two patients with essential tremor (ET) and 2 patients with multiple sclerosis (MS)] underwent comprehensive neuropsychological testing for cognitive functions, including general mental impairment, aphasia, agnosia, executive and constructional abilities, learning, memory, cognitive processing speed and attention as well as depression. The neuropsychological assessments were performed at least 6 months postoperatively (mean 9 months). Testing in the stimulation-on and stimulation-off condition was obtained within a period of 3 to 4 weeks. Unilateral DBS resulted in improvement of tremor in all patients. There were no significant differences between the stimulation-on and the stimulation-off condition with the exception of a decrement of word-recall in the short delay free-recall subtest of the Rey Auditory-Verbal Learning Test (RAVLT). Subgroup analysis indicated that the impairment in word-recall was related to left-sided thalamic stimulation. Our study confirms that chronic unilateral DBS is a safe method with regard to cognitive function. The subtle changes in episodic memory are related to stimulation per se and not to a microthalamotomy effect.

Aged↗

PubMed2003

Does excessive memory load attenuate activation in the prefrontal cortex? Load-dependent processing in single and dual tasks: functional magnetic resonance imaging study.

Functional magnetic resonance imaging was used to investigate the relationship between cortical activation and memory load in dual tasks. An n-back task at four levels of difficulty was used with auditory-verbal and visual-nonverbal material, performed separately as single tasks and simultaneously as dual tasks. With reference to single tasks, activation in the prefrontal cortex (PFC) commonly increases with incremental memory load, whereas for dual tasks it has been hypothesized previously that activity in the PFC decreases in the face of excessive processing demands, i.e., if the capacity of the working memory's central executive system is exceeded. However, our results show that during both single and dual tasks, prefrontal activation increases continuously as a function of memory load. An increase of prefrontal activation was observed in the dual tasks even though processing demands were excessive in the case of the most difficult condition, as indicated by behavioral accuracy measures. The hypothesis concerning the decrease in prefrontal activation could not be supported and was discussed in terms of motivation factors. Similar changes in load-dependent activation were observed in two other regions outside the PFC, namely in the precentral gyrus and the superior parietal lobule. The results suggest that excessive processing demands in dual tasks are not necessarily accompanied by a diminution in cortical activity.

Adult↗