Descriptive Psychopathology: The Signs and Symptoms of ...

59 Chapter 3: The brain and psychopathologyCapgras and other misidentification delusions suggests structural non-dominantcerebral hemisphere disease that may resolve best without antipsychotic drugs. 30The frontal lobes and psychopathology 31Many characteristically human behaviors (e.g. personality, emotional expression,thinking and reasoning, expressive language, and the generation of ideas andvoluntary movement) represent frontal lobe functioning. The frontal lobes subserveexecutive functioning, and guide the utilization of perceptions and memory.Executive functions include the recognition and solving of problems, the initiationof solutions, monitoring and self-correction of unfolding solutions, and theending of solving actions when successfully completed.Executive functioning deficits are common in patients with neuropsychiatricdisease. Many symptoms of mania and melancholia represent poor executive andother frontal lobe dysfunction (e.g. the characteristic abnormal movements ofmania and depressive illness, inappropriate social behaviors, and loss of efficiencyin daily activities). The intrusive thoughts and repetitive behaviors of patientswith obsessive–compulsive disorder reflect executive failure to regulate thoughtand action. Catatonia is the classic syndrome of motor dysregulation. The failureto recognize the unreality of hallucinations and the falseness of delusions is anexecutive function error.However, the frontal lobes are not homogeneous structures. In addition to Broca’sarea and the supplementary motor areas, the frontal lobes are divided into prefrontallateral and medial regions. Five parallel and anatomically separate circuitsin each frontal region align roughly parasagitally and consist of a cortical areaprojecting to circuit-specific nuclei in the basal ganglia (striatum, globus pallidus,substantia nigra), which in turn project to circuit-specific nuclei in the thalamus,which send feedback projections back to the originating cortical area (Figure 3.1).The five circuits are motor, oculomotor, 32 dorsolateral, orbitofrontal (ventrolateraland medial), and anterior cingulate, and each circuit has its signature features whendysfunctional. A lesion anywhere along a circuit compromises its function. Circumscribedsyndromes are associated with discrete lesions within a circuit, as seen insmall strokes. Complex syndromes are seen when the disease process involves morethan one circuit as seen in traumatic brain injury and frontal lobe dementias. 33The dorsolateral circuitDysfunction in this circuit is associated with impaired executive function,reasoning and problem solving, new learning, recall, cognitive flexibility, ideageneration, and using motor skills. When severe, diminished self-care is seen.Dysfunction in the circuit is associated with melancholic depressive states, schizophrenia,frontal lobe dementias, and an apathetic/avolitional syndrome (Table 3.2).