Data from: The influence of complex and threatening environments in early life on brain size and behaviour

The ways in which challenging environments during development shape the
brain and behaviour are increasingly being addressed. To date, studies
typically consider only single variables, but the real world is more
complex. Many factors simultaneously affect the brain and behaviour, and
whether these work independently or interact remains untested. To address
this, zebrafish (Danio rerio) were reared in a two-by-two design in
housing that varied in structural complexity and / or exposure to a
stressor. Fish experiencing both complexity (enrichment objects changed
over time) and mild stress (daily net chasing) exhibited enhanced learning
and were less anxious when tested as juveniles (between 77-90 days).
Adults tested aged 1 year, were also less anxious even though fish were
kept in standard housing after 3 months of age (i.e. no chasing or
enrichment). Volumetric measures of the brain using magnetic resonance
imaging (MRI) showed that complexity alone generated fish with a larger
brain, but this increase in size was not seen in fish that experienced
both complexity and chasing, or chasing alone. The results highlight the
importance of looking at multiple variables simultaneously, and reveal
differential effects of complexity and stressful experiences during
development of the brain and behaviour.