Frontal injury: Impairments of fundamental processes lead to functional consequences

Abstract

Frontal functions, or impairments, have achieved the status of pornography: everyone knows them when they see them, but there is little agreement on their exact defining properties. Patients with frontal lobe lesions have impairments in planning, monitoring, sequencing, and inhibiting responses. They cannot organize complex behaviors. They are somehow simultaneously unaware and distractible, irritable and apathetic, violent and passive, impulsive and perseverative. They lack empathy, self-awareness, and emotional regulation. Patients often are incapacitated by frontal impairments that paradoxically are not at all obvious to most observers. To understand the effects of frontal lesions, science has sacrificed countless rats and nonhuman primates. Neuropsychology and Neurology have sanctified a few tests as the tests of frontal function, and then spent money, time, and the mental health of countless graduate students and research assistants trying to tease out of those tests some basic knowledge of frontal functions. Experimental Psychology has brought novel constructs to the problem of defining frontal functions, and modern neuroimaging has merged the traditional clinical and the novel experimental with imaging technology. (A quick PubMed search of “fMRI and frontal lobes” on October 12, 2005 retrieved 4,646 articles, the most recent, “An fMRI study of the Trail Making Test”.) Yet, confronted with a patient with a large right prefrontal lesion who cannot hold a job or even be relied upon to buy the groceries he set out to buy, we have precious few tools to define his problem and almost nothing to offer to fix it.