Over the past decade, much information has been disseminated about “critical periods” – windows of plasticity, usually early in life, during which certain experiences must happen in order for certain abilities to develop. This concept has often been misapplied to suggest that only experiences early in life count, and that development and plasticity shut down after a certain point. This Network study has shown, however, that enriched experiences later in life can “re-open” windows of plasticity previously thought to be closed.
Earlier experiments have shown that young owls can effectively re-map their visual and auditory maps (including literally re-mapping the brain representations of these “maps”) when their visual input is manipulated by putting prisms over their eyes. These owls quickly learn the new relationships between auditory and visual input, and most adapt fully to the new relationship.
Adult owls, however, were largely unable to adapt to the shifted input. This study demonstrated that adding an “enriched” experience to these adult owls’ lives – in this case, hunting live mice instead of being fed dead mice – can radically increase the plasticity of these adult owls’ visual and auditory systems, allowing their brains to “re-map” and adapt effectively to the new input.
This new research challenges popular notions of plasticity and critical periods. While the brain is certainly very malleable early in life, it may never be too late for remarkable brain changes to take place, given greater “motivation” and appropriate stimulation. One interesting finding in this enrichment experiment has been that the degree of plasticity is correlated with the owls’ social dominance. Further studies will investigate how social dominance might contribute to plasticity, perhaps through greater access to resources or as a function of different levels of stress; or conversely, how greater plasticity may facilitate dominance status.
Bergan et al (2005) Hunting Increases Adaptive Auditory Map Plasticity in Adult Barn Owls. J. Neurosci. 25: 9816-9820.