Increased volume of the nucleus accumbens in schizophrenia

The nucleus accumbens, an integral and important part of limbic and prefrontal cortico-striato-pallidal-thalamic circuits, is involved in several cognitive, emotional and psychomotor functions altered in schizophrenia. In animal models, developmental disturbances within the entorhinal cortex and the hippocampus induce a dysregulation of inputs to the nucleus accumbens resulting in behavioral abnormalities which point to psychotic psychopathology. Nonetheless, due to the complex neuroanatomy of the human ventral striatum hardly any morphometric data on the nucleus accumbens are available. A postmortem stereological investigation of the nucleus accumbens was performed in complete brains of 9 male schizophrenics and 9 male controls between the ages of 46 and 64. Complete serial coronal slices of both hemispheres were stained with a modified Nissl-technique. Tissue shrinkage after staining and embedding was corrected for both individual and regional shrinkage. Based on recent precise delimitations of the human ventral striatum, in vivo hemisphere-adjusted volumes of the nucleus accumbens (volume densities) and absolute accumbal volumes were calculated applying the Cavalieri-estimator. In schizophrenics, mean hemisphere-adjusted volumes of the nucleus accumbens were significantly increased on both sides (right accumbens: p = 0,005**; left accumbens: p = 0,016*). Hemispherical volumes and volumes of the nucleus accumbens were significantly correlated in both groups (p = 0,02*). Most likely, this increase in volume of the ventral striatum reflects a decrease in naturally occuring cell death following prenatal cortical neurodevelopmental disturbances.