Takeo Watanabe Ph.D, a renowned professor from Brown University, gave a talk on Friday entitled “Roles of Reward in Perceptual Learning and Plasticity”. He shared his work over the years on unlocking the secrets of our brain and its incredible ability to constantly change and adapt. Throughout our lives, our brain is constantly forming new connections between cells and pruning off unnecessary parts to adapt to various situations. This process is known as brain plasticity. The brain’s ability to change is certainly impressive, but if it changed anytime it was exposed to new information, we might lose important knowledge as new neural pathways formed. Watanabe reasoned that there must be some balance between too much and too little plasticity. Watanabe seeks to find what exactly controlled this balance.
To arrive at an answer, Watanabe conducted groundbreaking research in the field of visual perception and has discovered new insight into the plasticity of the brain. Prior to his work, it was believed that the only way that the brain could learn, at least from visual information, was to have persistent attention as well as a particular task, such as picking out a number from a string of letters. However, in 2001 Watanabe found that participants in an experiment who were asked to remember numbers from a series of flashing letters learned more effectively when a number of dots moved in the background in a mostly random fashion. According to the commonly held belief, this background motion was task-irrelevant, and should not have affected performance.
Following these results, Watanabe conducted several experiments over the years and came to a number of surprising conclusions. For one, he found that even subliminal background movement could significantly enhance visual perceptual learning, though the participants were not actually aware of the motion. Furthermore, fMRI studies showed that the brain could actually be “trained” with this subliminal motion. Watanabe and his team paired a specific target image with a subliminal background motion. There were four images in all, and only one target image. By subtly rewarding the participant each time the target image and motion appeared, Watanabe actually noticed a re-wiring of the brain in response to this image. The brain could in effect be re-programmed to a small extent with a combination of task-irrelevant motion that the participant was not aware of and a reinforcement, such as a reward.
Further fMRI studies revealed that there were two areas of the brain that seemed to be involved in visual perceptual learning and may play a part in controlling the plasticity of the brain: MT+ (middle temporal) and LPFC (lateral prefrontal cortex). Using all these observations, Watanabe created his theory of perceptual learning, the Modified Model of Perceptual Learning. This theory holds promise in explaining a number of brain phenomena. In essence, it states that perceptual learning requires two things: a reinforcement (or reward) and information from the senses. The learned information can be either task-relevant, as in what we pay attention to, or task-irrelevant, such as background motion we ignore. Such information is reinforced by some kind of reward, and the brain learns, changing its circuitry. In addition, irrelevant information must be subliminal or inconspicuous to be learned.
Interfacing through the subliminal, “irrelevant” information that we are not aware of could have important evolutionary origins. Watanabe said, “When a tiger shows up, all I can do it pay attention to its movement. If I am lucky to escape, I learn features about the tiger and next time I can identify it more easily”. Watanabe provided an example of perceptual learning by attention, something we all do consciously every day. However, say you spot a tiger from far away. Your focus is on the tiger, but at the same time your brain learns “irrelevant” information such as the tiger’s environment, although you are not aware of it. This information is learned subliminally, and could help you avoid such environments, and tigers, in the future. Although there are many more mysteries of our brain to be unraveled, Watanabe’s research sheds new light on the way we learn and our brain’s incredible ability to adapt.