| dc.description.abstract | The present work gives overview and insight into three different areas of cognitive neuroscience, representing exemplary aspects of the diverse spectrum of research areas: Memory, attention and consciousness.
Research on memory processes distinguishes between working memory (WM) and long term memory (LTM). According to the classical view, the LTM encoding relies on structures in the MTL including the hippocampus and WM processes rely on the prefrontal and parietal cortices. In contrast to this simple dichotomy, however, recent studies have shown that some WM tasks, e.g. those involving novel stimuli, also activate MTL structures. In the first part the question of whether the maintenance of several items in WM, which activates the MTL, influences the encoding of items into LTM is addressed. It is demonstrated that a simultaneous WM/LTM task results in an interference, which affects memory processing capacities in the MTL and leads to a decrease in the LTM performance when accompanied by a high WM load. Furthermore the parahippocampal cortex (PHC) is revealed as a locus of a memory processing interference between WM and LTM for the first time.
Successful information processing requires focusing attention on a certain stimulus property and suppressing irrelevant information. An important paradigm for investigating attentional top-down control in case of interfering stimulus properties is Stroop’s interference task (Stroop, 1935). The second part the neural correlates of a newly developed auditory Stroop task are investigated. Using an event-related functional magnetic resonance imaging (fMRI) design, sound files in a tone-pitch interference task were presented, that required subjects to focus on one stimulus property (pitch or meaning of a spoken word) while ignoring the other one. In contrast to visual Stroop tasks a very posterior part of the anterior cingulate cortex (ACC) was found activated in incongruent phonetic trials (as compared to the incongruent semantic trials), together with common regions such as the pre-supplementary motor area (preSMA) and the dorsolateral prefrontal cortex (DLPFC), areas associated with attentional control. In addition, the integration of these regions into a conflict processing network using functional connectivity was shown.
In the context of a theoretical excursus the third part shows within the broad field of consciousness research, how new methods in recoding and analyzing electro-encephalography (EEG) data can lead to a different understanding of the origination of different states of consciousness. The starting point of consideration were recent findings revealing unusual and remarkable alterations in the EEG in meditation experts. Today meditation is considered to be a valuable source deepening our understanding of the neural correlates of consciousness, since meditation experts are usually trained for decades to reach altered states of consciousness. It is suggested that different forms of meditation have similar steps of development, which should be related to similar neurophysiological correlates. Some electrophysiological alterations can be observed on the beginner/student level, which are closely related to non-meditative processes. Others appear to correspond to an advanced/expert level, and seem to be unique for meditation related states of consciousness. Meditation is one possibility of specializing brain/mind functions within the confines of the brain’s neural plasticity. This plasticity is likely supported by certain meditation related EEG patterns, for instance, synchronized gamma oscillations. While it has been formerly postulated that meditation comprises mainly passive relaxation states, recent EEG findings suggest that meditation is associated with active states involving cognitive restructuring and learning. | |
