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 c ontrols, 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 mediodors al thalamic nucleus, the ventro-medial part of nucleus accumbens and t he ventral pallidum in nine brains from leucotomized schizophrenics. T his number was compared with counts from control cases and chronic sch izophrenics without leucotomy. The results showed that the total numbe r of nerve cells in the mediodorsal thalamic nucleus was statistically significantly reduced from 1.08 X 10(6) in chronic schizophrenics to 0.88 x 10(6) in leucotomized schizophrenics. Total neuron number was s tatistically significantly reduced in the ventro-medial part of the nu cleus accumbens in schizophrenics without further reduction in leucoto mized schizophrenics. The total neuron number in ventral pallidum was normal. With frontal leucotomy it is possible to investigate the conse quences of disconnection of the prefrontal cortex to central regions i n the human brain. The mediodorsal nucleus of thalamus represents a ma jor efferent projection to the prefrontal cortex. The dorsal prefronta l cortex projects to nucleus caudatus and the orbital prefrontal corte x to the nucleus accumbens, a prominent region in the limbic system. I t was expected that a lesion to the prefrontal region by anterograde, retrograde degeneration may affect the mediodorsal nucleus of thalamus .