Complex sentence: From Massachusetts General, McHugh went to the Institute of Psychiatry in London (where he studied under Sir Aubrey Lewis and was supervised by James Gibbons and Gerald Russell) then to the Division of Neuropsychiatry at Walter Reed Army Institute of Research.
Split into simpler sentences: From Massachusetts General, McHugh went to the Institute of Psychiatry in London (where he studied under Sir Aubrey Lewis and was supervised by James Gibbons and Gerald Russell). Following his year in London, McHugh went to the Division of Neuropsychiatry at Walter Reed Army Institute of Research.