Do resting state brain activity differ in Schizophrenia and Depression? Schiz Bulle.March.2013

23.04.2013

During goal directed activity (away from oneself), some brain regions show decreased activity. Activity in these areas spring back  while at rest or engage in self referential tasks. This brain network is the default mode network and includes superior and inferior anterior medial frontal regions, lower precuneus, and posterior lateral parietal cortices. This network plays a crucial role in self-referential processing.

Self referential tasks (tasks that involve perspective taking of intentions, beliefs and desires of others, remembering own past,planning own future ) are altered in schizophrenia and depression.  Self- outside boundaries are blurred in schizophrenia ie  fails to differentiate exogenous from endogenous stimuli. self referential (self generated)  memory is poor in schizophrenia but external source memory is intact. Medial frontal cortex is the key to self referential processing. As self referential processing is poor, hypoactivity in medial frontal cortex is expected in schizophrenia. Self focus is increased in major depression ie negative ideas are extensively attributed to self and  this manifest in rumination. As self referential processing is increased, the resting state  is likely to be hyperactive in depression.

Contrasting resting state function is expected in these two disorders. Is this supported by evidence?

Simone Kuhn and Jurgen Gallinat report the results of a meta analysis of all  f MRI /PET studies on resting state alterations in medial frontal cortex that compared patients with healthy controls. Meta-analysis include 11 studies reporting 140 foci of altogether 567 participants for schizophrenia and 11, studies with 70 foci of altogether 470 participants for depression.

Results

There is a decrease in resting-state (hypoactivity) compared with healthy controls in ventromedial prefrontal cortex (vmPFC) in schizophrenia. In contrast, hyperactivity was seen in major depression.

Conclusions

Resting state activity is reduced in schizophrenia. This could explain the reduction in self referential processing and  lack of insight. In contrast to this, resting activity is increased in depression and this goes with the idea of increased  rumination and self focus in depression.

Summary of the article:

Resting-state brain activity in schizophrenia and major depression: a quantitative meta-analysis.

Kühn S, Gallinat J.Schizophr Bull. 2013 Mar;39(2):358-65

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