Depersonalization: neurobiological perspectives

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Abstract

Depersonalization remains a fascinating and obscure clinical phenomenon. In addition to earlier Jacksonian neurobiological adumbrations, and conventional psychodynamic accounts, views started to be expressed in the 1930s that depersonalization might be a vestigial form of behavior, and since the 1960s that it might be a phenomenon related to the temporal lobe. Recent advances in the neurobiology of the limbic system, and the application of Geschwind's concept of disconnection in the corticolimbic system, have opened the possibility of developing testable models. This paper includes a review of these ideas and of the clinical features of depersonalization, particularly of its emotional changes, suggesting that they are important for the neurobiological understanding of depersonalization. It also draws attention to clinical similarities between the experiential narratives produced by patients suffering from depersonalization and those with corticolimbic disconnections. On the basis of this, a new model is proposed according to which the state of increased alertness observed in depersonalization results from an activation of prefrontal attentional systems (right dorsolateral prefrontal cortex) and reciprocal inhibition of the anterior cingulate, leading to experiences of "mind emptiness" and "indifference to pain" often seen in depersonalization. On the other hand, a left-sided prefrontal mechanism would inhibit the amygdala resulting in dampened autonomic output, hypoemotionality, and lack of emotional coloring that would in turn, be reported as feelings of "unreality or detachment."

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Contributions of anterior cingulate cortex to behaviour

Orrin Devinsky, Martha J. Morrell, Brent Vogt (1995)

Assessments of anterior cingulate cortex in experimental animals and humans have led to unifying theories of its structural organization and contributions to mammalian behaviour. The anterior cingulate cortex forms a large region around the rostrum of the corpus callosum that is termed the anterior executive region. This region has numerous projections into motor systems, however, since these projections originate from different parts of anterior cingulate cortex and because functional studies have shown that it does not have a uniform contribution to brain functions, the anterior executive region is further subdivided into 'affect' and 'cognition' components. The affect division includes areas 25, 33 and rostral area 24, and has extensive connections with the amygdala and periaqueductal grey, and parts of it project to autonomic brainstem motor nuclei. In addition to regulating autonomic and endocrine functions, it is involved in conditioned emotional learning, vocalizations associated with expressing internal states, assessments of motivational content and assigning emotional valence to internal and external stimuli, and maternal-infant interactions. The cognition division includes caudal areas 24' and 32', the cingulate motor areas in the cingulate sulcus and nociceptive cortex. The cingulate motor areas project to the spinal cord and red nucleus and have premotor functions, while the nociceptive area is engaged in both response selection and cognitively demanding information processing. The cingulate epilepsy syndrome provides important support of experimental animal and human functional imaging studies for the role of anterior cingulate cortex in movement, affect and social behaviours. Excessive cingulate activity in cases with seizures confirmed in anterior cingulate cortex with subdural electrode recordings, can impair consciousness, alter affective state and expression, and influence skeletomotor and autonomic activity. Interictally, patients with anterior cingulate cortex epilepsy often display psychopathic or sociopathic behaviours. In other clinical examples of elevated anterior cingulate cortex activity it may contribute to tics, obsessive-compulsive behaviours, and aberrent social behaviour. Conversely, reduced cingulate activity following infarcts or surgery can contribute to behavioural disorders including akinetic mutism, diminished self-awareness and depression, motor neglect and impaired motor initiation, reduced responses to pain, and aberrent social behaviour. The role of anterior cingulate cortex in pain responsiveness is suggested by cingulumotomy results and functional imaging studies during noxious somatic stimulation. The affect division of anterior cingulate cortex modulates autonomic activity and internal emotional responses, while the cognition division is engaged in response selection associated with skeletomotor activity and responses to noxious stimuli. Overall, anterior cingulate cortex appears to play a crucial role in initiation, motivation, and goal-directed behaviours.(ABSTRACT TRUNCATED AT 400 WORDS)