That work led to a postdoctoral fellowship in Cardiology, funded by the Ontario Heart Foundation at Toronto General Hospital, and supervised by the unit's Chief, E. Douglas Wigle.

In 1980 he founded the highly respected Computer Vision Group at the University of Toronto, which he led for 20 years.

At York, he was awarded the NSERC Tier I Canada Research Chair[17] in Computational Vision which he has held for three consecutive terms (2003-2024).

[19] He co-edited a 2005 comprehensive reference book titled Neurobiology of Attention[20] with Laurent Itti and Geraint Rees.

On May 12, 2018, Konstantinos Derpanis, Gregory Dudek and Michael Jenkin organized a day-long Verbal Festschrift to celebrate his 65th birthday.

John is a 4th-degree grandson of the composer Nikolaos Chalikiopoulos Mantzaros[25] and his wife Countess Marianna Giustiniani of the noble family of Komnenos Ioustinianos of Genoa.

[26] Mantzaros, born in Corfu, founded the Ionian School of music and is notably the composer of the National Anthem of Greece.

Iakovos, the father of Nikolaos, held a Doctorate of Law from the University of Padua and served as President of the Primary Council and Advocate General of the Ionian Islands.