Psychophysiologische Korrelate der Sprachverarbeitung im menschlichen Gehirn

Abstract

Cells that fire together, wire together. Donald Hebb introduced this learning principle in 1949 (Hebb, 1949). He named ensembles of neurons connected by this principle Cell Assemblies . Using the psychophysiological method of magnetoencephalography (MEG), the present work scrutinised linguistic aspects of single words on the background of Hebb s principle. Features under investigation were the orthographic word length, the familiarity of a word, its meaning, some of its syntactic features and its phonetic transcription. With the help of topography and timing of the word evoked brain responses it can be speculated about a time-line of word-processing: First, from 60ms after stimulus-onset on visual features of words are analyzed. Signatures of semantic processes can be measured from 80ms on whereas word frequency gains influence on the brain response from 120ms. Finally, syntactic processes become evident from 140ms. The reported processing cascade indicates that the brain can work on words very early after stimulus onset. Based on these findings, architectural implications and applications on other linguistic aspects are proposed in the (intentionally highly speculative) introduction. As experimental paradigms we used a active memory task, a passive reading task and a Mismatch Negativity (MMN, or, more precisely, its magnetic equivalent MMNm). Data analysis methods used in this work comprised the analysis of averaged raw data, its Minimum Norm Estimate (MNE) and the wavelet convolution of the continuous MNE. Statistical analysis was performed either on the global field power (GFP) or on regions of interest (ROI) of channels (raw data) or assumed dipoles (MNE).