Authors:

PULVERMÜLLER, F. & Assadollahi, R.

Reference:

Year of publication:

2001

CBU number:

5182

Abstract:

What is the impact of physical and cognitive word properties on the neuromagnetic brain response? Are the physiological correlates of these properties dissociable and if so, at which latencies? A group of 15 subjects performed a memory task while brain responses were recorded using a 148 channel MEG. Four groups of written words (short/long x rare/common) were presented repeatedly. Word length and frequency influenced brain responses at overlapping but distinct intervals: Already 90-120 ms after presentation long words led to a significantly higher global field power (GFP) compared to short words. The physiological manifestation of word frequency followed immediately (120-160 ms), but only for short words. An exclusive frequency effect for long words was observed slightly later (240-290 ms). Thus, there was a differential frequency effect: word frequency influenced neurophysiological correlates of short words much earlier than that of longer words. These data indicate (I) that non-physical cognitive aspects of stimuli can have an impact on early neuromagnetic responses, and (II) that the latency of this impact may depend on physical stimulus properties. We conclude that early steps of word processing are partly cascaded: processing of visual stimulus features (physical, word length) is immediately followed by access to word forms in the mental lexicon (cognitive, word frequency).