Visual evoked potentials relating to imagery: words for concrete objects versus absolute concepts.
We recorded visual evoked potentials (VEPs) elicited with high or low imaginable Chinese characters (HIC or LIC), representing concrete objects or absolute concepts, respectively. A closed circle (CC) acts as control stimulus. These were displayed (at 1.6 degrees visual angle) for 35 ms on a TV monitor. Twenty-one channel VEPs (band-pas filter: 0.05-60 Hz), using balanced non-cephalic electrodes, were recorded from -100 to 924 ms for 11 right-handed male volunteers. The VEPs were analyzed by multivariate analysis of variance (MANOVA) and comparison of topographies at four remarkable peaks (P110, N160, P230 and N320). MANOVA showed significant differences (p < 0.001) for both conditions of channel and stimuli (HIC, LIC or CC). P100 for the CC-VEPs, N160 for the HIC- and LIC-VEPs, P230 for the CC-VEPs, and N320 for the HIC-VEPs were remarkable in the posterior scalp regions. Topographies at P100 and N160 showed no difference between the HIC- and LIC-stimuli. However, those at N320 showed difference between the HIC- and LIC-stimuli over the occipital and posterior temporal areas. Those results suggest that the responses at P100 and N160 might segregate Chinese characters from non Chinese characters. N320 suggested certain processes in imagery on recognizing Chinese characters over the occipital and posterior temporal areas.
Shimoyama
I
I
Department of Physiology, School of Medicine, Chiba University, Japan. ichiro@med.m.chiba-u.ac.jp
Nakajima
Y
Y
Ito
T
T
Shibata
T
T
D000328:Adult; D001931:Brain Mapping; D005074:Evoked Potentials, Visual / Q000502:physiology*; D006801:Humans; D007092:Imagination / Q000502:physiology*; D007802:Language; D008297:Male