Behavioral–Neuroanatomical Correlates

Behavioral–Neuroanatomical Correlates

Disrupted neurobehavioral functioning in a number of psychi-atric and neurological disorders has revealed several interesting aspects of the role of the frontal lobes in behavior. Studies involv-ing dementias of the frontal lobe type, particularly Pick’s dis-ease, have provided some information concerning the role of the frontal lobes. Pick’s disease is quite distinguishable from the bet-ter known Alzheimer’s type in that in the former basic memory functions are relatively spared early in the disease course. The initial presentation of Pick’s disease largely involves the presence of striking changes in personality and social appropriateness. Memory dysfunction, if apparent, is secondary to motivational or attentional factors rather than faulty learning. Patients with Pick’s disease consistently perform poorly on a wide variety of tests sensitive to frontal lobe dysfunction.

Many of the studies involving the association of affective disorders and frontal lobe functioning have emerged from the litera-ture on stroke. Starkstein and associates (1987) have found that the left frontal opercular region is the area most frequently damaged in patients suffering from poststroke depression. Similarly, using com-puted tomography, Robinson and Szetela (1981) have demonstrated that the closer the lesion is to the frontal pole, the more severe the en-suing depression. After reviewing the relationship between frontal lobe impairment and affective dysfunction in poststroke depression, Baxter and colleagues (1989) concluded that left prefrontal hypome-tabolism was the most consistent and severe finding in major de-pression, bipolar depression and obsessive–compulsive disorders.

A surge in the study of schizophrenia has provided a wealth of knowledge concerning the functioning of the prefrontal cortex. It is generally agreed that cognitive abnormalities associated with schizophrenia often involve difficulties in executive processing. Some of the earliest and best known studies involving neuroimaging techniques in the assessment of cognitive abilities in this population were carried out by Weinberger and colleagues. Many other studies employing rCBF (Buchsbaum et al., 1984; Weinberger et al., 1988; Sagawa et al., 1990) and functional brain imaging (Buchsbaum et al., 1990) have found evidence to support the “hypofrontality” hy-pothesis in schizophrenia. However, not all studies have found fron-tal hypometabolism in patients with schizophrenia (Gur et al., 1985; Berman et al., 1988). The heterogeneous nature of schizophrenia probably accounts for these contradictory findings. A number of researchers including Volkow and colleagues (1987) and Andreasen and associates (1992) have found that hypofrontal-ity was most related to patients with a predominance of negative symptoms.