Planning and spatial working memory following frontal lobe lesions in man

Twenty-six patients with unilateral or bilateral frontal lobe excisions were compared with age and IQ matched controls on a computerized battery of tests of spatial working memory and planning. A computerized test of spatial short term memory capacity revealed no significant impairment in the patients' ability to execute a given sequence of visuo-spatial moves. In contrast, a paradigm designed to assess spatial working memory capacity, revealed significant impairments in the patient group in both possible types of search errors. Furthermore, additional analysis showed that the frontal lobe patients were less efficient than controls in their usage of a strategy for improving performance on this test. Higher level planning was also investigated using a test based on the "Tower of London" problem [SHALLICE, T. Phil. Trans. R. Soc. Lond. B. 298, 199-209, 1982]. Patients with frontal lobe damage required more moves to complete the problems and a yoked motor control condition revealed that movement times were significantly increased in this group. Taking both of these factors into consideration, initial thinking (planning) time was unimpaired in the patient group although the thinking time subsequent to the first move was significantly prolonged. These data are compared to previous findings from patients with idiopathic Parkinson's disease and are discussed in terms of an impairment of higher cognitive functioning following frontal lobe damage.