The intent of this dissertation was to reveal (by utilizing a set of cognitive tasks that are visuospatial in nature) how complex mental tasks are performed in the brain. Particular attention was devoted to the functional systems subserving the processes comprising the complex internal generation of mental images and their rotation;Utilizing Electroencephalography (more specifically, alpha power reduction), the functional system subserving the processes of mental rotation and mental image generation was identified. In this functional system, the occipital lobes are bilaterally involved in the initial encoding of visual information into a neural representation. These representations are then shunted to the parietal lobes, with the left parietal lobe specifically involved in generating the three dimensional representation of the stimuli, while actual mental rotation is mediated by left temporal lobe. All of the above subprocesses are completed under the auspices of the right frontal lobe which appears to be involved in mediating comparison and decision subcomponents of the task. In cases where stimuli need to be resampled for further analysis, the right occipital lobe played an important role;The most significant findings of this dissertation are that multiple brain locales are involved in performance of complex visuospatial tasks, and that these locales can be quite remote from one another, with some residing in left hemisphere and some in the right. It is apparent that some of the existing confusion in the literature exploring hemispheric superiority for image generation and mental rotation may be partly attributed to the mistaken expectation that one hemisphere is solely involved in performing a given spatial task. Recent advances in brain imaging technology (like the one employed here) are rapidly changing this manner of thinking.