Hippocampal integrity and neurocognition in first-episode schizophrenia: a multidimensional study

OBJECTIVES

Impairments in memory and executive function are key components of schizophrenia. These disturbances have been linked to several subcortical and cortical networks. For example, anatomical and functional changes in the hippocampus have been linked to deficits in these cognitive domains. However, the association between hippocampal morphometry, neurochemistry and function is controversial. Therefore, we aimed to investigate the relationship between hippocampal anomalies and their functional relevance.

METHODS

Fifty-seven first-episode schizophrenia patients (FE-SZ) and 61 healthy control subjects (HC) participated in this study. Hippocampal volumes were investigated using structural magnetic resonance imaging (sMRI) and hippocampal neurochemistry was determined using proton magnetic resonance spectroscopy (1H MRS). Verbal memory was used as a hippocampus-dependent cognitive task whereas working memory and cognitive flexibility assessed frontal lobe function.

RESULTS

FE-SZ presented smaller volumes of the left hippocampus, with a significant correlation between left hippocampal volume and verbal memory performance (immediate recall). There was also an inverse correlation between neurochemical ratios (NAA/Cho and Cho/Cr) and verbal memory (delayed recognition). Tests of cognitive flexibility and working memory were not correlated with MRI and 1H MRS values. Compared to HC, FE-SZ demonstrated reduced performance in all of the assessed neurocognitive domains.

CONCLUSIONS

These results point to a relationship between verbal memory and hippocampal integrity in schizophrenia patients which might be independent from deficits in other memory domains. Disturbed verbal memory functions in FE-SZ might be linked specifically to hippocampal function.

[The effect of thyroid function on the increase of plasma cyclic AMP following glucagon injection (author's transl)]

The increase in plasma cyclic adenosine-3':5'-monophosphate (cAMP) was measured after intravenous injection of 1 mg of glucagon in 26 normal subjects, 36 patients with hyperthyroidism, 35 patients with hypothyroidism and 24 patients with euthyroid goitre. While patients with euthyroid goitre responded normally, the plasma cyclic AMP response in patients with hyperthyroidism was considerably increased and in those with hypothyroidism decreased. 4 patients with cirrhosis of the liver had reduced responses and 1 patient with extrahepatic obstructive jaundice an enhanced response. This test seems to be a valuable additional parameter for the description of the thyroid-dependent metabolic situation. However, because of its unspecificity it cannot replace the measurement of serum T3, T4 and thyrotropin (TSH) response to thyroliberin (TRH).