Neurophysiological distinction of action words in the fronto-central cortex - PubMed (original) (raw)
Neurophysiological distinction of action words in the fronto-central cortex
Olaf Hauk et al. Hum Brain Mapp. 2004 Mar.
Abstract
It has been suggested that the processing of action words referring to leg, arm, and face movements (e.g., to kick, to pick, to lick) leads to distinct patterns of neurophysiological activity. We addressed this issue using multi-channel EEG and beam-former estimates of distributed current sources within the head. The categories of leg-, arm-, and face-related words were carefully matched for important psycholinguistic factors, including word frequency, imageability, valence, and arousal, and evaluated in a behavioral study for their semantic associations. EEG was recorded from 64 scalp electrodes while stimuli were presented visually in a reading task. We applied a linear beam-former technique to obtain optimal estimates of the sources underlying the word-evoked potentials. These suggested differential activation in frontal areas of the cortex, including primary motor, pre-motor, and pre-frontal sites. Leg words activated dorsal fronto-parietal areas more strongly than face- or arm-related words, whereas face-words produced more activity at left inferior-frontal sites. In the right hemisphere, arm-words activated lateral-frontal areas. We interpret the findings in the framework of a neurobiological model of language and discuss the possible role of mirror neurons in the premotor cortex in language processing.
Copyright 2004 Wiley-Liss, Inc.
Figures
Figure 1
Illustration of our hypothesis: Action words are represented by cell assemblies comprising neurons in the core language areas and additional neurons in motor areas in the frontal cortex controlling movements carried out with the corresponding body parts.
Figure 2
Mean rating scores for the dimensions arm‐, face‐, and leg‐relatedness (with standard deviations) obtained in a word rating experiment. Ratings were given on a scale from 1 to 7.
Figure 3
**Top:**Current estimates of grand‐mean data for selected time points illustrate the activity flow within the first few hundred milliseconds after stimulus onset. Activity in fronto‐central brain areas is visible only in the time range around 220 msec. Data in the time window 210–230 msec were, therefore, submitted to a more detailed topographical analysis. Bottom: The overall signal strength (RMS) over time.
Figure 4
Time courses of grand‐mean current estimates for three selected dipole locations where differential activity between word categories is prominent. The time point 220 ms is indicated by a vertical line.
Figure 5
Difference of grand‐mean source current intensity maps for mean topographies within the time range 210–230 ms. Red colour indicates larger values at corresponding sites for subtractant, blue colour larger values for subtractor (see labels). Maps are normalized to their respective extrema, and are presented in top view (top is front, left is left) and left view (front is left, top is up).
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