Recovery from brain injury in animals: relative efficacy of environmental enrichment, physical exercise or formal training (1990-2002).

In the 1960s, it was shown for the first time that enriched housing enhances functional recovery after brain damage. During the 1970s and 1980s, many findings similar to this initial one have been reported, enlarging greatly its generality. Over the last 13 years, many different kinds of brain damage were modelled in animals or even directly studied in humans. Overall, these recent studies corroborated earlier findings, although occasional exceptions were reported. Other critical data, obtained mainly in intact animals, showed that enriched housing increases neurogenesis in the adult hippocampus. Recent evidence that this neurogenesis is involved in hippocampal-dependent learning supports the original interpretation of the enrichment effects as being the result of an accumulation of informal learning experiences (e.g., [. Heredity, environment, brain biochemistry, and learning. In: Current Trends in Psychological Theory. University of Pittsburgh Press, Pittsburgh, pp. 87-110;. Brain changes in response to experience. Sci. Am. 226, 22-29]). Other components of enriched environment, such as physical exercise, may have additive effects with those of training. The comparison of the relative effectiveness of enriched experience, of physical exercise and of training on structural and/or functional assessments of recovery, shows that training/learning is generally more effective than physical exercise and that enriched experience is a more potent therapy than either of these two other treatments. The combination of enriched experience with some other neurosurgical and/or neuropharmacological treatments may further improve its therapeutic effectiveness. Finally, other recent reports emphasize that the treatment parameters may be changed in order to approximate clinical/rehabilitation conditions and, nevertheless, remain effective. Copyright 2004 Elsevier Ltd.