Using a computerized task designed to be frustrating, Chiappelli and colleagues discovered that stress induces an increase in salivary levels of kynurenic acid, an endogenous neuromodulator with nicotinic and N-methyl-D-aspartate antagonist properties. Patients with schizophrenia who were unable to tolerate the task and quit early exhibited unusually elevated levels of salivary kynurenic acid, implicating the kynurenine pathway in the pathophysiological mechanism of stress in schizophrenia.
Mathew and colleagues used high-resolution structural magnetic resonance imaging to quantify hippocampal subfield volumes across the psychosis spectrum. They reported reduced subfield volume most pronounced in the cornu ammonis 2+3, subiculum, and dentate gyrus among patients diagnosed as having schizophrenia, schizoaffective, or psychotic bipolar disorder. Furthermore, these subfield volumes correlated with positive symptoms as well as declarative memory, suggesting that hippocampus-related cognitive deficits may underlie the pathophysiology of psychosis.
Using data from an epidemiological cohort study followed up since birth, Holz and colleagues reported that prenatal nicotine exposure resulted in weaker activation in the anterior cingulate cortex and the inferior frontal gyrus during inhibitory control as well as in decreased volume in the inferior frontal gyrus, despite controlling for various confounders. Activity was inversely related to lifetime attention-deficit/hyperactivity disorder in the inferior frontal gyrus and novelty seeking in the anterior cingulate cortex.
Kühn and colleagues showed neuroplasticity deficits in the hippocampal subfields cornu ammonis (CA) 2+3 of patients dependent on alcohol but not in healthy control individuals when comparing high-resolution structural magnetic resonance images acquired after withdrawal and 2 weeks later. The volume of cornu ammonis 2+3 in patients directly after withdrawal was negatively associated with years of regular alcohol consumption and more severe alcohol withdrawal symptoms.
Kohno and colleagues examined the relationship between resting-state functional connectivity within the mesocorticolimbic system and sensitivity of regional activation to levels of risk during risky decision making in methamphetamine-dependent and healthy individuals. The groups differed in midbrain functional connectivity and sensitivity of activation in the dorsolateral prefrontal cortex and striatum during risky decision making.
Highlights. JAMA Psychiatry. 2014;71(7):727. doi:10.1001/jamapsychiatry.2013.2739