Clinical Assessment of Prefrontal Lobe Functions.

PURPOSE OF REVIEW: Whereas it was previously thought that there was a single overarching frontal lobe syndrome, it is now clear that several distinct cognitive and behavioral processes are mediated by the frontal lobes. This article reviews these processes and the underlying neuroanatomy and provides an approach to the assessment of prefrontal lobe functions at the bedside.

RECENT FINDINGS: Cognitive and behavioral frontal lobe functions are mediated by the prefrontal regions rather than the frontal lobes as a whole. At least five separate prefrontal functions have been defined: energization, task setting, monitoring, behavioral/emotional regulation, and metacognition. Energization is mediated by the superior medial prefrontal cortices bilaterally, task setting by the left lateral frontal cortex, monitoring by the right lateral prefrontal cortex, behavioral/emotional regulation by the orbitofrontal cortex, and metacognition by the frontal poles. Only task setting and monitoring are considered executive functions.

SUMMARY: Distinct cognitive and behavioral processes are mediated by different parts of the frontal lobe. Lesions in these areas result in characteristic clinical deficits that are discussed in this article. Key messages are that prefrontal regions mediate the higher cortical functions (as opposed to the frontal lobes in general) and that prefrontal functions are not equivalent to executive functions.