NEONATAL INSULT TO THE HIPPOCAMPAL REGION AND SCHIZOPHRENIA - A REVIEW AND A PUTATIVE ANIMAL-MODEL

Objective: To review the mounting evidence implicating early hippocamp al dysfunction in the pathogenesis and the pathophysiology of schizoph renia. An account is made of recent neurodevelopmental hypotheses indi cating how an early dysfunction of the hippocampal region disrupts mat urational events in brain systems connected to that structure, thus in ducing dysfunctional connectional development Finally, an animal model is presented. Method: Socioemotional behaviour of monkeys (Macaca mul atta) with selective neonatal hippocampal lesions was assessed by anal yzing their interactions with their age-matched controls at 2 months, 6 months, and 5 to 8 years of age and by comparing the social interact ions at each age with those of normal controls paired together. Result s: At 2 months of age, monkeys with neonatal hippocampal lesions prese nted minor disturbances in initiation of social interactions. These su btle changes of behaviour were less evident at 6 months, although by t hat age, the operated monkeys displayed more withdrawals in response t o an increase in aggressive responses from their unoperated peers. In adulthood, the amount of time spent by the hippocampectomized monkeys in social contacts with their normal peers decreased markedly. In addi tion, operated monkeys exhibited more locomotor stereotypies than norm al controls. Conclusion: These experimental findings indicate that the rime-course and nature of the behavioural disturbances resulting from early trauma to the hippocampal region have some similarities with th e clinical symptoms of schizophrenic patients and the typical time-cou rse of the disease.