Figure 4 Several views of somatosensory evoked response recorded with MEG. (a) A depiction of the evoked response waveforms recorded over the surface of the head. Waveforms are positioned according to the polar projection of the corresponding sensor locations. (b) An envelope or "butterfly" plot of the stacked waveforms reveals the balanced polarity of MEG responses, allowing appreciation of temporal relationships between waveform features. (c) Contour plots of the field maps observed at two latencies of the evoked response. Field maps are plotted in polar coordinates. The left panel suggests a simple activation pattern early in the response. The right panel suggests the presence of an additional source in the contralateral hemisphere. (d) Equivalent current dipole sources estimated from early latencies localize to the posterior bank of the central sulcus.
lexical class of stimulus. A spoken sentence might be presented in which the final word either completes a reasonable semantic construct or renders the sentence nonsensical. Such paradigms can tap the mechanisms by which we comprehend language.
Was this article helpful?