Experience-dependent neuronal plasticity in the pathogenesis and therapy of mental disorders

Whereas the basic wiring of the mammalian central nervous system is genetic ally predefined, its fine tuning throughout different phases of infancy, ch ildhood, and adulthood are highly experience-dependent. There is growing ev idence from a variety of experimental data that juvenile experience and lea rning events modulate the functional maturation of the brain, thereby shapi ng the neuronal substrate for the development of intellectual and socioemot ional capacities. Since early experiences occur during phases of elevated n euronal and synaptic plasticity, they induce an "imprinting" of synaptic co nnectivity and neural circuitry in the infant brain. Results From experimen tal research support the hypothesis that impoverished intellectual stimulat ion and traumatic socioemotional experience during early childhood may impa ir the formation of functional brain pathways, in particular of the limbic circuits, which play a major role in emotional behavior and learning. Such defective systems, representing functional "scars" in the brain, may be the neuronal basis of a variety of mental disorders and clinical symptoms caus ed by early stressful psychosocial environments. A basic thesis of this pap er is that mechanisms involved in neuronal learning and memory are not only used and reused in structuring the CNS during the initial establishment of connections in the immature brain but also can be employed in molding pers onality and behavior during psychotherapy in adulthood.