Perhaps you should try some spelling variations:
"chains asymmetric" » "chains symmetric", "chain symmetric", "channels asymmetric"
"brain asymmetric" » "brain asymmetries", "green asymmetric", "plan asymmetric"
"brain asymmetry" » "brain symmetry"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("brain asymmetry") OR ((("brain asymmetric") OR ("chains asymmetric")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"brain asymmetry\") or (((\"brain asymmetric\") OR (\"chains asymmetric\"))))".
• Removing quotes may allow a broader search: (( brain asymmetry ) or ((( brain asymmetric ) OR ( chains asymmetric )))).
• Adding a wildcard symbol may retrieve word variants: (("brain asymmetry") or ((("brain asymmetric") OR ("chains asymmetric"))))*.