Descriptive Psychopathology: The Signs and Symptoms of ...

79 Chapter 3: The brain and psychopathologyfrom a complex neuronal network involving frontal and temporal cortex. 148 Howthey occur, however, remains unclear.Excitatory or ictal hallucinations are usually brief (few seconds), stereotypic,poorly formed, and typically not lateralized. Associated alteration of consciousnessoccurs before or immediately after the hallucinations. Hallucinations thatappear to be release phenomena are typically fully formed, lateralized to the sideof the lesion, and occur without any alteration in consciousness. 149Electrical brain stimulation of the temporal cortex in either cerebral hemispheretypically elicits auditory hallucinations. Spontaneous auditory hallucinations arecommonly reported in patients with temporal lobe epilepsy. Complex auditoryhallucinations (e.g. phonemes, music) are associated with temporal cortex stimulationor irritation. Elementary or simple auditory hallucinations (e.g. buzzing,mechanical humming, and unidentifiable sounds) are reported with lesions orstimulation of subcortical structures within the auditory pathways. 150 Auditoryhallucinations occur across a range of non-illness and disease states, particularlythose with reduced arousal, drug intoxication, delirium, and psychosis.Dysfunction of the brain areas responsible for speech is associated withauditory hallucinations. The dysfunction is not always structural. Psychiatricpatients often describe auditory hallucinations as either inside or outside thehead. These two phenomena may originate from different brain areas. Whenthe left planum temporale (the extension of Wernicke’s area on the roof ofthe temporal lobe) is involved, hallucinated voices are perceived as external to theindividual. 151Verbal hallucinations are reported when there is activation in the primaryauditory cortex, Heschel’s gyrus, on the left. Functional imaging also findsdecreased metabolism in the left temporal gyrus and disruption of frontal–temporal connectivity. 152 When musical hallucinations are experienced, no suchactivity is seen in either the left or the right Heschel’s gyrus, indicating thatfor musical hallucinations to occur the primary sensory cortex need not beactivated. Spontaneous activity in the auditory neuronal circuit (network) otherthan primary sensory cortex is responsible for perceiving and processing musicalstimuli. 153 The different brain areas subserving language and music are anexplanation for why some aphasic patients who cannot speak fluently can stillsing fluently.Olfactory and tactile hallucinationsThe neurobiological literature about tactile and olfactory hallucinations is scantand clinically unhelpful. Stimulation of temporal–limbic areas 154 in epilepticpatients elicits these hallucinations. The brain areas responsible for olfactionand touch may also be involved. 155 Olfactory hallucinations have been reported