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Prof. Milner was the former Chair of the ³ÉÈËVRÊÓƵ’s Psychology Department, and a recipient of the Gold Medal for Distinguished Lifetime contributions to Canadian Psychology.

A re-enactment of the discovery of self-stimulation in 1954. Left to right: Seth Sharpless, Peter Milner, Jim Olds. The rat is being placed in a box with a runway to test its tendency to return to the place where it previously received stimulation.

Peter M. Milner, a British-trained electrical engineer who worked on radar and atomic energy during WW2 and later trained as a neuroscientist at ³ÉÈËVRÊÓƵ and then taught and did research there for many years, has died at the age of 99. He was best known as the co-discoverer of electrical self-stimulation of the brain, together with the late James Olds. The phenomenon they discovered was one of the first demonstrations of direct control over behavior by artificial activation of specific parts of the brain that came to be known as ‘pleasure centers’. The publication of their finding in 1954 created much interest in the investigation of the neural basis of behavior. The phenomenon was studied by scientists all over the world, resulting in thousands of publications. Many students were attracted to this area of study by the demonstration of self-stimulation and became working neuroscientists who have made numerous contributions to all areas of neuroscience. This work has advanced our understanding of how behavior is controlled by its consequences and provided an important foundation for the study of drug addiction.

As described by Milner, he and Olds were using rats to study the effects of electrical stimulation of the reticular formation, a structure at the back of the brain thought to be important for arousal (or vigilance or wakefulness). Due to an error in the process of inserting the electrode into the brain of the first rat they tested, the electrode actually stimulated a structure towards the front of the brain called the lateral septal area. Milner and Olds observed that the rat repeatedly returned to the area of the test cage where it had received stimulation, and then showed that the rat would avidly press a lever to obtain short bursts of stimulation. Following this discovery, Olds mapped the entire brain showing which areas produced reward and which produced aversion when stimulated.

Peter Marshall Milner was born in 1919 in Silkstone Common and grew up in Barnsley, in south Yorkshire, England. His father was David William Milner, a research chemist; his mother was Edith Anne Marshall, an ex-schoolteacher. A family story had it that one of his father’s ancestors was Joseph Priestly, the discoverer of oxygen and carbon dioxide. Both his parents were trained teachers, so he received much of his early education from them at home, learning to read and write well before these skills were taught at school. Milner’s father was interested in electricity and built radio sets, so Milner was exposed to these things at a very early age. He studied science at Barnsley grammar school and, upon graduation, was accepted into the probationary apprenticeship program at Metropolitan-Vickers, a large engineering firm with a interest in radio communications. After a year in various departments at this company, he entered the Electrical Engineering program at Leeds University.

Milner graduated from Leeds with a degree in electrical engineering in 1941, and was immediately given a position at the Air Defense Research and Development Establishment, an institution on the south coast of England that was developing a radar system that could be used to detect flying objects and accurately aim anti-aircraft guns at them. He was assigned to work on the method of displaying the array of aircraft flying in the vicinity to the operators. In this task he was helped by ‘a young Cambridge psychology graduate called Brenda Langford’ who was in charge of testing the various versions of the display and controls on the operators. In the fall of 1944, with the war winding down, Milner was asked if he was interested in going to Canada for two years to work on atomic energy. By this time, he and Brenda had ‘become close’, and they decided to marry so that she could accompany him to Canada.

The authorities had decided to build a nuclear reactor in Chalk River, Ontario which, at the time, was a watering stop for steam locomotives on the trans-Canada railroad. Milner worked there on methods for detecting the corrosion of water pipes used to cool the reactor, and on a method for measuring the effect on construction materials of the intense neutron flux that would be produced by the reactor. However, his two year assignment was over before the reactor was operational, so he left before any of his contributions could be tested.

Brenda remained in Montreal during this time, teaching a course at the University of Montreal. In 1945, Robert MacLeod, a well known researcher in psychology, came to ³ÉÈËVRÊÓƵ and Brenda arranged to take a graduate course he offered. In 1947, MacLeod left ³ÉÈËVRÊÓƵ for Cornell, and D.O. Hebb became chair of the Department of Psychology. Neither Peter nor Brenda was anxious to return to England, were life remained difficult due to the aftereffects of the war, and both of them were very interested in pursuing Hebb’s ideas about the relationship of the brain to behavior. Brenda became Hebb’s graduate student. Peter had been reading the material from Brenda’s courses, including the manuscript of a book Hebb had written. This book would later be published as ‘The Organization of Behavior’, and is now famous for making the case that behavior can be explained by understanding the functions of the brain in general and of neurons in particular. Milner was fascinated by these ideas, and he decided that studying them would be a more interesting way to spend his life than designing electrical components. Accordingly, he asked Hebb to supervise him as a graduate student. Hebb agreed provided Peter took a year of undergraduate psychology courses first. As it happened, ³ÉÈËVRÊÓƵ was setting up its research cyclotron at that time and, due to his experience at Chalk River, Milner was able to get a part-time job constructing instruments for them. He completed his qualifying year and became a graduate student. It was during his graduate student years that he and Olds collaborated on the discovery of self-stimulation.

Milner’s PhD thesis, ‘Effects of Intracranial Stimulation on Rat Behavior’, examined the effects of electrical stimulation of the reticular formation of rats on time estimation. After completing the thesis Milner was given a post-doctoral position that included some teaching. One of his first contributions during this period was a paper, ‘The Cell-Assembly: Mark II’, which proposed a modification of the theory of the neural control of behavior Hebb had presented in his book. Hebb had postulated the ‘cell assembly’ a connected network of neurons that represented a Ìýperception. These assemblies were created by recursive neural activity which recruited new neurons and strengthened the synaptic connections between them. Milner saw a parallel between this process and the atomic chain reactions he had been working on at Chalk River. An unrestrained chain reaction was a positive feedback system that resulted in an atomic explosion. One of the main problems in designing a reactor for peaceful purposes was to restrain the growth of the reaction. Milner saw that Hebb’s proposal would result in similar unrestrained growth of cell-assemblies and proposed an inhibitory process that would limit their growth.

The ideas in Hebb’s book also interested a group of computer scientists at the IBM laboratories in Poughkeepsie, NY, where the first work on computers and what they could do was getting underway. Milner was hired as a consultant in on the basis of his paper and a recommendation from Hebb, in the field that would become known as artificial intelligence.

In 1956, Milner was appointed as an Assistant Professor in the ³ÉÈËVRÊÓƵ Psychology Department, with a full load of teaching and research supervision responsibilities. His major course was called Physiological Psychology, and he began creating small booklets of notes explaining the topics covered. Milner was a shy man who did not take to lecturing naturally. During his lectures he often addressed the blackboard while writing key words and concepts or creating simple diagrams to illustrate the results of experiments. In fact, it was often difficult for his students to follow what he was trying to say. Several of them, who were particularly interested in the subject, spent time in the library after each of his lectures reading the papers he had discussed and trying to understand them. So, inadvertently perhaps, those students got an excellent education in what was then called Physiological Psychology.

In 1970, the various notes that Milner had provided to his classes were combined and published as a textbook, ‘Physiological Psychology’. It was an unusual book because it did not simply recite facts, but attempted to present a consistent theoretical view of the subject. It was very highly regarded and dominated the market for several years. The book was translated into several languages. Naturally, it soon became out of date, but no further editions were published.

Among other papers, in 1974 Milner published ‘A Model for Visual Shape Recognition’ in which the problem of stimulus equivalence was explained on the basis of convergence and recursive feedback among the cell-assemblies representing visual perceptions. ‘Brain-Stimulation Reward – a Review, was published in 1991, and ‘The Psychobiology of Reinforcers’ (with N. White) was published in 1992.

Milner’s last major publication (1999) was a short monograph, ‘The Autonomous Brain’. In it, he reverted to his original interest in the field, using up-to-date information about the brain to understand the problems of perception, motivation and learning, in which his interest had initially been aroused by reading Hebb’s The Organization of Behavior. It can be argued that he takes an engineering approach to understanding the neural representation of psychological processes, pointing out what will and will not work based on knowledge of the morphology and connections of the neurons that perform these functions. Milner posits that the main impetus for behaviour is not external stimulation (the ‘reflex model’) but the internal activity of the brain and its plans for action, often based on internal needs. This activity influences both the sensory systems to select percepts pertinent to a plan, and the motor system to select actions required to carry out the plan.

During his career at ³ÉÈËVRÊÓƵ, Milner trained a number of graduate students and post-doctoral fellows who went on to make their own contributions to various areas of neuroscience. These include John Pinel (UBC), W. Mac Burnham (Toronto), Ronald J. Racine (McMaster), Richard J. Beninger (Queens), Graham Goddard (Dalhousie, Otago), Shinshu Nakajima (Dalhousie), Michael Corcoran (Saskatchewan), Aaron Ettenburg (Santa Barbara), Patrick Mason (US Air Force Science and Technology), Imre Szabo (Pecs), Dale Corbett (Memorial), and Keith Franklin (³ÉÈËVRÊÓƵ).

In 2005 Milner received the Gold Medal for Distinguished Lifetime Contributions to Canadian Psychology from the Canadian Psychological Association. The award recognized both his major influence on the development of the field now known as Behavioural Neuroscience, and his exceptional contribution of ideas to the understanding of basic psychological processes.

Norman White
Emeritus Professor
Department of Psychology
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of Prof. MilnerÌýpublished by the Society for Neuroscience in 2014ÌýinÌýThe History of Neuroscience in Autobiography.

Selected References Highlighting Prof. Milner's Research:

Olds, J. L., & Milner, P. M. (1954). Positive reinforcement produced by electrical stimulation of septal area and other regions of rat brain. Journal of Comparative & Physiological Psychology, 47, 419–427.

Milner, P. M. (1957). The cell assembly: Mark II. Psychological Review, 64(4), 242–252.

Milner, P. M., & White, N. M. (1987). What is physiological psychology? Psychobiology, 15, 2–6.

Milner, P. M. (1991). Brain stimulation reward: a review . Canadian Journal of Psychology, 45, 1–36.

Milner, P. M. (1989). The discovery of self-stimulation and other stories. Neuroscience & Biobehavioral Reviews, 13, 61–67.

Milner, P. M. (1999). The Autonomous Brain: A Neural Theory of Attention and Learning. Mahwah, NJ: Lawrence Earlbaum Associates.