Cognitive neuropsychophysiology of thought imagery versus imagination imagery

The present study was designed to measure patterns of cortical activation during two types of mental imagery: "thought imagery" and "imagination imagery." Topographic cortical power spectrum (CPS) analyses were conducted for 10 subjects during four experimental conditions. EEG was recorded from right and left hemispheres at frontal, temporal, parietal, and occipital leads. Subjects gave rating of visual vividness and quasisensory subjective experience after each imagery condition. Examination of subjects' ratings revealed that they reported significantly greater visual vividness and quasisensory experiences during the imagination imagery condition, as compared to the thought imagery condition. Topographic CPS analyses showed significant individual differences in patterns of brain activation, which were reliable across conditions. Individual differences in lateralization of brain activity were found in terms of an anterior-posterior gradient. Within-subject analyses showed CPS changes as a function of condition. Three major patterns of CPS changes across condition were delineated.