Leucotomized schizophrenics lose neurons in the mediodorsal thalamic nucleus

It has previously been shown that chronic schizophrenic patients have a 40–50% reduction in the total number of nerve and glia cells in the mediodorsal thalamic nucleus and the nucleus accumbens compared with controls, while the total neuron and glia number is the same in the two groups in the ventral pallidum. Using new stereological cell counting methods, neuron and glia cell numbers were estimated in the mediodorsal thalamic nucleus, the ventro-medial part of nucleus accumbens and the ventral pallidum in nine brains from leucotomized schizophrenics. This number was compared with counts from control cases and chronic schizophrenics without leucotomy. The results showed that the total number of nerve cells in the mediodorsal thalamic nucleus was statistically significantly reduced from 1.08 × 10⁶ in chronic schizophrenics to 0.88 × 10⁶ in leucotomized schizophrenics. Total neuron number was statistically significantly reduced in the ventro-medial part of the nucleus accumbens in schizophrenics without further reduction in leucotomized schizophrenics. The total neuron number in ventral pallidum was normal. With frontal leucotomy it is possible to investigate the consequences of disconnection of the prefrontal cortex to central regions in the human brain. The mediodorsal nucleus of thalamus represents a major efferent projection to the prefrontal cortex. The dorsal prefrontal cortex projects to nucleus caudatus and the orbital prefrontal cortex to the nucleus accumbens, a prominent region in the limbic system. It was expected that a lesion to the prefrontal region by anterograde, retrograde degeneration may affect the mediodorsal nucleus of thalamus.