Objective: There is increasing concern that the course of psychiatric
disorders may be affected by parameters such as the duration and inten
sity of symptoms of initial episodes of illness. As this indicates tha
t abnormal function produces long-term changes within the brain, a rev
iew of the neuroscience literature regarding neuroplasticity is warran
ted. Method: This article is a selective review, focusing in particula
r on results obtained from physiological experiments assessing plastic
ity within the mammalian neocortex. The possible relevance of results
to psychiatry is discussed. Results: While the most dramatic examples
of neuroplasticity occur during a critical period of neural developmen
t, neuroplasticity can also occur in adult neocortex. Neuroplasticity
appears to be activity-dependent: synaptic pathways that are intensive
ly used may become strengthened, and conversely, there may be depressi
on of transmission in infrequently used pathways. Conclusions: Results
from neurophysiological experiments fend support to the clinical obse
rvation that the intensity and duration of a psychiatric disorder may
adversely alter its long-term course. Rapid aggressive treatment may p
revent this from occurring. While pharmacotherapy may reduce the durat
ion and severity of symptoms, it may also have an independent, as yet
unknown, effect on neuroplasticity.