Brain activation induced by the perceptual maze test: a PET study of cognitive performance

We investigated with PET the cerebral activation pattern elicited by the perceptual maze test (PMT), a neuropsychological test used to evaluate organic brain injury. The PMT examines visuospatial skill, general intelligence, visually guided motor planning, and the ability to obey rules. Eight right-handed volunteers were examined with PET using the tracer [15O]butanol. Three paradigms containing the PMT, a motor control (SHAM), and a rest condition were examined twice in a randomized order. Solving the PMT caused extensive bilateral activations in the occipital lobe extending rostrally into the parietal lobe and caudally to the posterior part of the temporal lobe. Bilateral activations were also seen in the prefrontal, medial premotor, and the anterior cingulate cortex (ACC). The premotor and primary sensory motor cortices contralateral to the performing hand were also activated. Marked activations were noted in the visual system, including areas pertaining to visuospatial decoding. The previously defined functional network (ACC, prefrontal and posterior parietal cortex) for the maintenance of visuospatial attention was activated during the PMT. Extensive bilateral deactivations were seen in frontomedial, temporal, parietal, and posterior cingulate regions. This pattern may represent relatively decreased blood flow in cortical areas pertaining to sensory modalities that were not activated in the PMT. The decreased activity in these regions could also express diminished cognitive processing in neuronal systems that might interfere with the task-related performance.