„Einfluss der elektrischen Hochfrequenzstimulation des Nucleus ...

Abstract 1
Abstract
Since the work of Ebbinghaus, memory was thought to be just one process of
acquisition, storage and transfer of association. But recently several studies
could show that memory is characterized as a multiple system, consisting of
many processes and at least two different types, conscious and unconscious
memory. It could also be demonstrated that both memory types are mediated
by different brain areas. Conscious memorization, also called as declarative
memory, is induced by hippocampus whereas unconscious memory, also
known as non-declarative or procedural memory, is mediated by caudate
nucleus. Impairment of memory, existing in various neurological diseases like
Parkinson’s disease, was treated for a long time just by drugs but since high
frequency stimulation (HFS) has become an important therapy for different
neurological and psychiatric diseases, different studies are investigating the
effects of HFS on memory deficits. In previous in vitro and in vivo studies, it
could be demonstrated that during HFS GABA outflow increased in caudate
nucleus of rats. We therefore investigated the effect of striatal HFS
application on procedural learning in rats and possible long-term effects of
HFS on several neurotransmitter systems in caudate nucleus.
In a first experiment, rats were trained in a plus maze for three days, twice a
day, to look for a reward in an alternating but marked maze arm. Therefore,
animals were divided into two groups, food deprived (FD) and food ad libitum
(AdL) rats, and subdivided in each group into stimulated (STIM) and operated
but not stimulated (SHAM) rats. After each training session, unilateral HFS of
left caudate nucleus was performed over 4 hours in alternating 20 min
periods. Nineteen hours after last HFS and immediately after a probe trial
assessing the animals’ memory strategy, the rat brain was quickly removed
and histological examination of the brain was performed to check the right
position of the stimulation electrode in the left caudate nucleus. None of the
animals showed a misplacement of the guide cannula and the electrode in
the caudate nucleus, suggesting a high reliability of surgery. There was
neither a large damage to the neuronal tissue nor an extended gliosis around