An examination of right dorsolateral prefrontal lobe function in self-directed attention by use of repetitive transcranial magnetic stimulation, electroencephalograph, and visual evoked potentials.

摘要

The capacity for self-awareness has been tested in humans, chimpanzees, and orangutans by use of the mirror self-recognition test (MSR; Gallup, 1970). While numerous researchers have speculated that this ability is predominantly located in the right hemisphere (e.g., Siegal, Carrington. & Radel, 1996), especially in the frontal lobes (e.g., Stuss & Benson, 1986), a thorough investigation of the cortical correlates of self-awareness has yet to be completed. To investigate the cortical correlates of self-awareness, the original mirror test was modified for use in psychophysical and cortical investigations. Subjects were exposed to pictures of self and others (e.g., friend, stranger, famous people) under varying conditions. These conditions of self and non-self were employed to determine if (1) There is an advantage in reaction time and accuracy in identifying the self, (2) There is a localizable region of cortical change in the cortex associated with subjects' engagement in self-related tasks, (3) Localized cortical stimulation alters the performance of self-related activities. It was found that self-faces were identified more rapidly than non-self faces when subjects responded with their left hand. Subjects were also more likely to identify a picture as their own face when responding with their left hand under several face morphing paradigms. Evoked potential data indicated that the right frontal lobe is preferentially activated when subjects attend to self-images. Repetitive transcranial magnetic stimulation (rTMS) delivered at 1 Hz to a localized region of the right frontal cortex enhanced self-identification. These results indicate that self-recognition is correlated with neural activity in the right prefrontal cortex, particularly in the dorsolateral region (Area 46). The implications of these data for modular processing of self-awareness are discussed.