Mesulam's frontal lobe mystery re-examined

Purpose: Mesulam's (1986) mystery is that some patients with frontal lobe damage may show no cognitive impairment according to traditional office-based assessment procedures, yet nevertheless show marked cognitive handicap in everyday life. Mesulam suggested that "the office setting may introduce sufficient external structure to suppress some of these behavioral tendencies" (p. 322). We ask if it is indeed the office setting that is the problem, or whether it is that traditional assessments do not measure the full range of cognitive functions supported by prefrontal cortex. Method: Neuropsychological case series study and review. Results: Traditional methods for assessing cognitive deficits following frontal lobe damage typically do not measure the full range of deficits that can occur. In particular, rostral prefrontal cortex supports functions which are not routinely assessed yet are crucial to competent everyday life performance. These include meta-memory functions (e.g. context and source memory), complex behavioural co-ordination (e.g. prospective memory and multitasking), and mentalizing. Conclusions: New clinical assessment procedures are required urgently. These could be based, in principle, both on recent experimental findings from cognitive neuroscience, and observation of behaviour outside office settings. These procedures could then be administered in an office setting