Summary

• This review addresses some of the primary reasons why the sex of participants is an important factor that should be considered in studies at all levels of neuroscience.
• There are widespread misconceptions about brain sex differences in the field.
• Sex differences exist in every major part of the brain.
• New methods are revealing previously unsuspected sex differences.
• Many regions of the brain that are responsible for cognitive processes, such as the hippocampus, amygdala and neocortex, are sexually dimorphic.
• A consideration of sex influences can help to reconcile seemingly contradictory findings in neuroscientific research.
• Active investigation of sex influences is mandatory to fully understand and treat a host of brain disorders with sex differences in the incidence and/or nature.
• Sex matters for understanding brain function much more than has been widely assumed in neuroscience, and perhaps much more than we yet recognize.