Descriptive Psychopathology: The Signs and Symptoms of ...

77 Chapter 3: The brain and psychopathologytemporal–parietal–occipital cortices and their linked subcortical structures. 133 Asa rule, a hallucination in a specific sensory modality indicates dysfunctionsomewhere in that sensory system. The clinical challenge is determining if thephenomenon reflects a primary or secondary behavioral disorder.Efforts to elucidate more specific relationships between perceptual disturbancesand a brain lesion or dysfunction are disappointing because of the reliance on smallsamples with poorly described psychopathology. A typical study has almost asmany authors as subjects. 134 The results from neurologic and psychiatric patientsand normal individuals have been combined for interpreting underlying mechanisms,leading to confusion. For example, on functional MRI healthy persons exhibitintermittent and substantial increased activity in the auditory cortex during silencebecause they often subvocalize. 135 This activity is similar to patterns reported forpatients while they are experiencing hallucinating voices. But if non-hallucinatingand hallucinating persons have similar brain metabolic patterns under similarcircumstances, the pattern does not explain the hallucination.Generalizing findings is also risky, as many of the proposed relationshipsbetween perceptual disturbances and brain areas come from the epilepsy literature,where stimulation of specific cortices elicits hallucinations in that modality.An endogenous excitatory focus is also proposed for the perceptual disturbancesseen in psychiatric patients, but has not been identified. The irritating focus,experimental or endogenous, may also not be linked directly to the associatedperceptual disturbance as the involved area might influence “downstream”regions that more directly produce the perceptual disturbance. 136Patients with schizophrenia are also most often recruited for study. But it isuncertain whether the biological perturbations associated with hallucinations inthese patients is specific to schizophrenia or also provides an understanding ofthe neurology of hallucinations found in other syndromes. The findings are alsoinconsistent for schizophrenia. Auditory hallucinations have been associated withreduced left temporal lobe volume in some patients, 137 but not in others. 138Reduced metabolic responses to speech in the left but not the right planumtemporale on functional imaging 139 is reported in other schizophrenics comparedto normal persons. 140 However, these and similar studies are inconsistent insources of subjects (chronically hospitalized, first-episode, post- or anti-mortem),quality of diagnosis (including or not including schizoaffective patients), andconditions under which the patients are assessed (tasked or at rest). No patternof abnormality is consistent among studies of schizophrenic patients. Further,since schizophrenics also typically have speech and language problems, abnormalbrain areas subserving language are expected. Any abnormality could be afunction of the disease or its other features as well as contributing directly tohallucinosis.