- Double dissociation:
- A term particularly used in neuropsychology when two patient groups show opposite patterns of deficit, e.g. normal STM and impaired LTM, versus normal LTM and impaired STM.
- Electroencephalogram (EEG):
- A device for recording the electrical potentials of the brain through a series of electrodes placed on the scalp.
- Event-related potentials (ERPs):
- The pattern of electroencephalograph (EEG) activity obtained by averaging the brain responses to the same stimulus (or similar stimuli) presented repeatedly.
- Long-term potentiation (LTP):
- A process whereby synaptic transmission becomes more effective following a cell’s recent activation.
- Magnetic resonance imaging (MRI):
- A method of brain imaging that relies on detecting changes induced by a powerful magnetic field.
- Magnetoencephalography (MEG):
- A system whereby the activity of neurons within the brain is detected through the tiny magnetic fields that their activity generates.
- Positron emission tomography (PET):
- A method whereby radioactively labeled substances are introduced into the bloodstream and subsequently monitored to measure physiological activation.
- Traumatic brain injury (TBI):
- Caused by a blow or jolt to the head, or by a penetrating head injury. Normal brain function is disrupted. Severity ranges from “mild” (brief change in mental status or consciousness) to “severe” (extended period of unconsciousness or amnesia after the injury).
- Mapping Memory in the Brain: A lecture by Eric R. Kandel, who probes into the mind to demonstrate how it is much more complex than just a series of processes carried out by the brain.
- BrainInfo: A portal to neuroanatomical information on the web.
- An interactive, 3-D model of the brain.
- A demonstration of what to expect when you go for an MRI scan.
- What video about what to expect when you go for a CT scan.
- A video about how Positron Emission Tomography works.
- ERP set up demo.
- Memories are Made of This: A lecture by Eric R. Kandel.
- In Search of Memory: A Scientific American interview with Eric R. Kandel.
- A Royal Institute lecture: Eleanor Maguire talking about the neuroscience of memory.
Donald Olding Hebb
Born in 1904 to two medical doctors, Donald Hebb quickly grew to stand out as a swift learner in his Canadian province of Nova Scotia. By the age of 10, he was already enrolled in the seventh grade, having benefitted from his mother’s Montessori-influenced homeschooling. Yet, he bristled at the more structured academic environment of his new school, a posture that led him to fail the eleventh grade. Still, he muddled through and went on to attend Dalhousie University after graduating secondary school with aspirations of becoming a novelist. His continued hostility towards authority was met with a lackluster record at the university, though he received a B.A. in 1925 and soon started teaching. “D.O.,” as Donald was known to his friends, soon decided his interests were elsewhere and became something of a migrant laborer, finding work where he could across Canada.
An introduction to Sigmund Freud’s work fanned the 23-year-old’s interest in psychology, though he dismissed much of Freud’s research for what he saw as a lack of rigor. Nevertheless, Hebb enrolled in a graduate course in psychology at McGill University, where he studied education and intelligence and taught on the side. Following the death of his first wife on Hebb’s twenty-ninth birthday, he left Canada to do his Ph.D. work under the supervision of Karl Lashley, a noted behaviorist remembered for his unrealized quest to pinpoint where in the brain memory traces—or engrams—were stored. Lashley soon moved from the University of Chicago to Harvard University, taking Hebb and two other students with him. There, Hebb studied the effects of sensory deprivation in rats, receiving his Ph.D. in 1936.
A year later, Hebb was remarried to the woman that would mother their two daughters and preparing to work with Wilder Penfield at the Montreal Neurological Institute, where he went on to witness the striking effects of brain damage. From there, he took a teaching position at Queen’s University, eventually moving to Florida for another opportunity to work with Lashley as Hebb began writing what would come to be his landmark book, The Organization of Behavior: A Neuropsychological Theory. Hebb returned to McGill as a professor of psychology in 1947, where he was later named chairman. Four years after the death of his second wife, Hebb married Margaret Doreen Wright. Following his retirement from McGill, Hebb went back to his alma mater in 1980 as a professor emeritus of psychology at Dalhousie University. Hebb died at the age of 81 in Nova Scotia, two years after the death of his third wife.
During his long and illustrious career, Hebb presided over the Canadian, as well as the American Psychological Association—the same organization that awarded him the Distinguished Scientific Contribution Award in 1961. Later, in 1966, Hebb was elected a Fellow of the Royal Society. The Canadian Psychological Association continues to give out a yearly award in Hebb’s name to distinguished Canadian researchers.
Hebb’s approach to studying thought and behavior centered on the neurons that give rise to them. His basic notion, often summarized as “the neurons that fire together, wire together,” continues to influence our understanding of neurophysiology, psychology, engineering, and computer science to this day. This beautifully simple idea, referred to as Hebb’s learning rule, suggests that repeated co-activations will strengthen associative bonds between the constituent elements, giving rise to cohesive processing units (“cell assemblies”) and, in turn, habits and long-term memories. Indeed, Hebb’s ideas have been borne out in the discovery of long-term potentiation (LTP), given rise to numerous neural network models, and provided a biological rationale for the errorless learning method used to facilitate memory rehabilitation in amnesic patients.
Hebb had numerous other contributions to the field, including the development of the Adult Comprehension Test and the Picture Anomaly Test, designed to measure specific aftereffects of brain surgery, rather than relying on general measures of intelligence. His work with surgical patients produced some of the first evidence that the right temporal lobe was associated with visual recognition, as well as the finding that individuals often maintained the bulk of their cognitive capacity and memory after the resection of large parts of the frontal lobe. Studying the problem solving abilities of rats across the lifespan using the Hebb-Williams maze, Hebb demonstrated lasting effects of early experience on later abilities, an important principle in developmental psychology.
Hebb’s teaching has directly influenced a great many prominent researchers in the field, including Brenda Milner, Faraneh Vargha-Khadem, Mortimer Mishkin, and James Olds, to name but a few. Moreover, his work has inspired countless others, such as Fergus Craik and Eric Kandel, to dedicate their lives to unlocking the secrets of memory in the brain.
Hebb, D. O. (1949). The organization of behavior: A neuropsychological theory. New York: Wiley.
Hebb, D. O. (1958). A textbook of psychology. Philadelphia, PA: Saunders.
Hebb, D. O. (1959). A neuropsychological theory. In S. Koch (ed.), Psychology: A study of a science: study I. conceptual and systematic: volume 1. sensory, perceptual and physiological, 622–643. New York, NY: McGraw-Hill.
Hebb, D. O., and Penfield, W. (1940). Human behaviour after extensive bilateral removal from the frontal lobes. Archives of Neurology and Psychiatry 44: 421–436.