John O'Keefe receiving his Nobel Prize from His Majesty King Carl XVI Gustaf of Sweden at the Stockholm Concert Hall, 10 December 2014. Copyright © Nobel Media AB 2014
Photo: Alexander Mahmoud

John O'Keefe after receiving his Nobel Prize at the Stockholm Concert Hall, 10 December 2014. Copyright © Nobel Media AB 2014
Photo: Alexander Mahmoud

John O'Keefe receiving his Nobel Prize from His Majesty King Carl XVI Gustaf of Sweden.

© Nobel Media AB 2014. Photo: Niklas Elmehed

Nobel Laureates at the Nobel Prize Award Ceremony. From left: Physics Laureates Isamu Akasaki, Hiroshi Amano and Shuji Nakamura; Chemistry Laureates Eric Betzig, Stefan W. Hell and William E. Moerner; Medicine Laureates John O'Keefe and May-Britt Moser. Copyright © Nobel Media AB 2014
Photo: Niklas Elmehed

John O'Keefe receiving his Nobel Prize. Overview from Nobel Prize Award Ceremony at the Stockholm Concert Hall, 10 December 2014. Copyright © Nobel Media AB 2014
Photo: Alexander Mahmoud

John O'Keefe with his wife, Mrs Eileen O'Keefe, on stage after the Nobel Prize Award Ceremony. Copyright © Nobel Media AB 2014
Photo: Alexander Mahmoud

John O'Keefe with family and relatives on stage after the Nobel Prize Award Ceremony at the Stockholm Concert Hall, 10 December 2014. Copyright © Nobel Media AB 2014
Photo: Alexander Mahmoud

John O'Keefe arrives at the Nobel Banquet together with his wife, Professor Eileen O'Keefe, 10 December 2014.

© Nobel Media AB 2014. Photo: Helena Paulin-Strömberg

Dr Na Ji, spouse of Nobel Laureate Eric Betzig, and John O'Keefe at the table of honour at the Nobel Banquet. Copyright © Nobel Media AB 2014
Photo: Niklas Elmehed

John O'Keefe delivering his banquet speech after the dinner. Copyright © Nobel Media AB 2014
Photo: Niklas Elmehed

John O'Keefe delivering his banquet speech.

© Nobel Media AB 2014. Photo: Helena Paulin-Strömberg

Members of the Swedish Royal Family receive the Laureates and their significant others in the Prince's Gallery after the Nobel Banquet. From left to right: John O'Keefe, May-Britt Moser, Her Majesty Queen Silvia, King Carl XVI Gustaf, Edvard I. Moser and and Professor Eileen O'Keefe.

© Nobel Media AB 2014. Photo: Niklas Elmehed

John O'Keefe surrounded by relatives during the Nobel Foundation reception at the Nordic Museum in Stockholm, 9 December 2014. Copyright © Nobel Media AB 2014
Photo: Alex Ljungdahl

John O'Keefe delivering his Nobel Lecture at Aula Medica, Karolinska Institutet in Stockholm, on 7 December 2014.

Copyright © Nobel Media AB 2014

All three Medicine Laureates assembled at the stage of the Aula Medica, Karolinska Institutet in Stockholm, on 7 December 2014.

Copyright © Nobel Media AB 2014

Like many Nobel Laureates before him, John O'Keefe autographs a chair at Bistro Nobel at the Nobel Museum in Stockholm, 6 December 2014.

Photo: Janerik Henriksson/TT

John O'Keefe at the Nobel Museum in Stockholm, Sweden, on 6 December 2014. Copyright © Nobel Media AB 2014
Photo: Niklas Elmehed

John O'Keefe arriving at the Nobel Museum in Stockholm, Sweden, for the 2014 Nobel Laureates' Get together on 6 December 2014. Copyright © Nobel Media AB 2014
Photo: Niklas Elmehed

Portrait of John O'Keefe.

Photo: Adam Smith. Copyright © Nobel Media AB 2014