NEW APPROACHES TO PREFRONTAL LOBE TESTING

This chapter addresses the assessment of functions related to the prefrontal region within frontal lobes. It is proposed in this chapter that the neuropsychological assessment of the prefrontal region of the brain can be divided into four functional categories: (1) executive cognitive, (2) behavioral/emotional self-regulatory, (3) activation regulating, and (4) metacognitive processes. The general frontal regions relating to these four are depicted in Figure 1. Insert Figure 1 about here Several clarifications establish the limits of this review. The reader is first cautioned on the interpretation of the term " categories. " It does not designate a functional module, in the Fodorian sense. It reflects a grouping of similar behaviours, all of which have a higher order, more central, relationship to other functions in the brain. These categories are domain general. Second, although the term " frontal lobes " may be used in the review for sake of simplicity, the emphasis is on the prefrontal cortex, and little mention will be made of the motor or premotor regions and effects of damage there. Third, there is no attempt to make a direct connection to " executive function " , or the " dysexecutive syndrome. " These terms are not easily operationalized, and there is inconsistency amongst authors in the application of these terms. Moreover, executive function is a psychological construct, with no necessary relation to anatomical structure. Tests purported to measure executive function may be impaired after diffuse brain damage (e.g., traumatic brain injury), inefficient integrative functioning (such as may occur in confusional states), and after damage to many different nonfrontal brain regions (the latter is likely secondary to impairment in the myriad additional functions required to perform the multi-faceted tests often used to test " executive functions. " It is also possible that executive dysfunction after damage in nonfrontal brain regions may be due to impairment in network connectivity.) Consequently, deficits on an " executive function " test cannot be automatically interpreted as damage to the frontal lobes (an important concept for those who do research in aging, and use the tests to infer the integrity or non-integrity of the frontal lobes). It is nevertheless accepted that executive functions may be best instantiated in the frontal lobes, and in " frontal systems " – those areas with direct connections to the frontal lobes. Because the comparative evidence on how each node in a system is functionally similar or dissimilar …