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How the Brain Encodes Reward

Okihide Hikosaka: May 7, 2009; Running Time: 0:51:02

About the Lecture

About the Lecture

As Ann Graybiel puts it, “basal ganglia were dark basement structures” until Okihide Hikosaka began his classic 1980s research demonstrating how these neuronal clusters influenced eye movements. Hikosaka has deepened and broadened his work in this once neglected area of the brain, and brings a McGovern audience up to date on his latest discoveries.

Hikosaka briefly sketches what is known about the basic pathways leading in, around and out of the basal ganglia, circuits that have been associated with stress, pain, mood, memory and arousal. This specialized cluster of neurons seems especially attuned to the neurotransmitter dopamine, and Hikosaka has been investigating “a number of unsolved questions,” including how dopamine neurons form circuits for movement control, whether such neurons encode “motivational values,” and what other parts of the brain guide them.

Hikosaka describes research demonstrating that certain dopamine neurons become excited if a visual cue indicates a future reward, and become inhibited with a visual cue indicating no reward. Dopamine also increases after an action delivers a reward and decreases when an action produces no reward. Research began to explore whether dopamine neurons “encode motivational values, including reward and punishment.” After others’ studies yielded contradictory or uncertain conclusions, Hikosaka designed a set of studies on monkeys involving classical Pavlovian conditioning, with juice rewards and air puffs as aversive stimuli.

Among Hikosaka’s findings: some dopamine neurons were excited primarily by positive, reward-predicting stimuli, others inhibited by air puff-predicting stimuli. But he also found another group of dopamine neurons excited both by positive and negative reward-predicting stimuli (as well as the stimuli themselves). Hikosaka posited two types of neurons that react in very different ways to motivational signals, which he described as value-coding and salience-coding. He also determined that the lateral habenula, a part of the brain sitting at one end of the thalamus, seems to regulate dopamine pathways involved in some motivational responses. By sending a weak electric pulse through the lateral habenula, Hikosaka saw a very strong inhibition of the dopamine neurons that “encode mostly motivational values.”

Lecture Details

Location: 46-3002

“We know there are many brain areas that project to dopamine neuron areas, but which are critical for providing dopamine neurons with reward or motivation value signals?”

Okihide Hikosaka

About the Speaker

Okihide Hikosaka

Senior Investigator, Laboratory of Sensorimotor Research
National Eye Institute
National Institute of Health

Okihide Hikosaka researches the control of eye movements, functions of the basal ganglia, neural mechanisms of motivation, neural mechanisms of procedural learning, and mechanisms of spatial attention.

Hikosaka earned a graduate degree at the University of Tokyo in 1978, and became a Lecturer at Toho University School of Medicine. From 1979-1982, he was a visiting scientist at the National Eye Institute. In 1983, he was named Associate Professor at Toho University School of Medicine. In 1988, he became a Professor at the National Institute of Physiological Sciences in Okazaki, and from 1993-2002, he was a Professor at Juntendo University School of Medicine. He joined the Laboratory of Sensorimotor Research, National Eye Institute at NIH in 2002.

Okihide Hikosaka

Hikosaka's NEI page

About the Host

About the Host

McGovern Institute for Brain Research at MIT

The McGovern Institute for Brain Research at MIT is led by a team of world-renowned, neuroscientists committed to meeting two great challenges of modern science: understanding how the brain works and discovering new ways to prevent or treat brain disorders. The McGovern Institute was established in 2000 by Patrick J. McGovern and Lore Harp McGovern, who are committed to improving human welfare, communication and understanding through their support for neuroscience research.