Hippocampal activity may reflect ‘core’ schizophrenia traits

Jan 28 2014

By Eleanor McDermid, Senior medwireNews Reporter

Hippocampal function may be a useful biomarker for the response of patients with schizophrenia to medication, research suggests.

Hippocampal activity was significantly increased in schizophrenia patients relative to mentally healthy controls and was associated with impaired cognition, report Jason Tregellas (Denver VA Medical Center, Colorado, USA) and colleagues.

“The observed hyperactivity both supports models of hippocampal dysfunction in schizophrenia and increases the appeal of this measure as a potential biomarker,” they write in The American Journal of Psychiatry.

Such biomarkers of neuronal function are needed to determine whether potential therapies produce the necessary biologic effects, they explain.

The team reports that resting right hippocampal activity, measured on functional magnetic resonance imaging, was about twofold higher in 28 schizophrenia patients than in 28 age- and gender-matched mentally healthy controls. Left hippocampal activity did not differ between the groups.

Right hippocampal activity also correlated significantly and negatively with patients’ overall scores on the MATRICS (Measurement and Treatment Research to Improve Cognition in Schizophrenia) Consensus Cognitive Battery (MCCB).

Their overall scores were significantly lower than those of the controls, and this was driven by differences in the processing speed, attention/vigilance, and social cognition domains.

The verbal learning, working memory, visual learning, and reasoning/problem-solving domains were unaffected by schizophrenia status, yet scores for two of these – working memory and visual learning – fell significantly in line with increasing hippocampal activity, as did scores for the attention/vigilance domain.

These findings suggest that “these cognitive processes may be particularly affected by hippocampal dysfunction,” say Tregellas et al. “Although the mechanisms involved are not clear, it is possible that increased activity at ‘rest’ reduces the region’s ability to be recruited according to task demands, resulting in impaired performance.”

Furthermore, hippocampal activity was positively and MCCB scores negatively associated with patients’ scores on a modified version of the Scale for the Assessment of Negative Symptoms , but there was no association with positive symptoms on the Brief Psychiatric Rating Scale.

This is in line with negative symptoms being more stable over time than positive symptoms, less amenable to treatment, and more predictive of functional outcomes, says the team.

“Given that hippocampal dysfunction, cognitive impairment, and negative symptoms are often present before the first episode of psychosis, it is possible to speculate that these phenotypes may constitute core traits of the disorder that may reflect neuropathological status more accurately than do positive symptoms.”

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