SHIMOJO Implicit Brain Function


Research Director: Dr. Shinsuke Shimojo
(Professor, Division of Biology and Biological Engineering, California Institute of Technology)
Research Term: 2004-2009


The brains of humans are usually described as comprising basically two parts, or aspects: the physical brain and consciousness, also called mind. Psychiatrists starting with Freud and Jung also spoke of the subconscious mind, referring to mental activities within the brain that are carried out completely unaware by the conscious mind. Implicit thinking. Of these three phenomena, the physical brain has been the most easily researched and understood, since it is more directly accessible by chemistry, physics and physiology. However, mind along with its conscious and subconscious aspects has been far more elusive to investigations by the biophysics of neurons, neuro systems, and neural-nets. People are often interested in mind when deciding to be professionals in brain science, though the vast majority forget this when doing research.

Perhaps this is about to change. Owing to a wide variety of new investigative tools it is becoming ever more possible to relate activities within specific parts of the brain with various phenomena, including vision, hearing, memory, decision making, and emotions. It is becoming increasingly possible to actually watch animals, including humans, carry out mental activities in real time, and to see the interconnections of these activities that are distributed over wide areas of the brain.

Shinsuke Shimojo was educated in the field of experimental psychology and psychophysics, while emphasizing vision, perception and cognition. This included experiments involving the eye viewing something and how this is analyzed and understood in the brain and becomes a part of consciousness. It has long been considered that the eyes are “windows to the brain”. This is not only because the eye system is in fact like a window where light passes through the pupil and then stimulates a cascade of electrophysiological/neurochemical activities all the way from the rods and cones of the retina to many areas of the brain, but also because the eyes directly reflect brain activity. They can act as a feedback system where one can actually obtain information about somebody else’s brain activity by watching their eyes. Shimojo has been particularly interested in situations involving the interaction of motion and location, detection of changes and binding of features by attention, etc.

In the early 2000s this line of research led to an understanding that there is a significant amount of processing of visual information by the subconscious brain, before it appears in consciousness, where it is judged and acted on. In short, this approach seemed to give a very good way to analyze the subconscious brain and how it works using new and powerful tools as well as traditional ones. Shimojo’s classic experiment involved showing someone photos of two faces of the opposite sex, and then asking which is more attractive. The person chooses. When asked why, a story is conjured up at a conscious cognitive level. It was possible, however, to show that before the person made a conscious decision, the subject’s eyes started showing a statistical bias towards one picture. Thus implicit type orienting response, as a somatic precursor of conscious preference decision, involves a “gaze cascade” effect. This phenomenon was observed not just for faces, but also for jewelry and other objects, sometimes several seconds before conscious understanding. Something appears to be happening in the orienting mechanism, preceding to a conscious emotional decision. It is thus necessary to figure out what is happening between the implicit and explicit aspects of the brain. This is basic science.

Further, though, a deeper understanding of this type of implicit-explicit interactions might lead to better strategies for brain-machine interface, for instance. Or prosthetics, but unlike artificial limbs, neural prosthetics. One can also consider Internet shopping with interactive facilities that can help customer to narrow down choices by a system that records and utilizes subconscious preference. By comparing fMRI with eye scans and behavioral decision, it might be possible to find correlations. Perhaps it is even possible to manipulate the preferences of people by manipulating their gaze, before conscious recognition. A longer gaze seems to produce a feedback of desire. A gaze fix experiment has shown that it is not just total time of exposure, but spontaneous engagement with gaze that matters. Via this dynamical interplay between orienting and internal processing, familiarity and novelty interact. The same themes appear concerning such subjects as music and addiction.


Outline of Research

The Shimojo Implicit Bain Functions project is trying to understand implicit, or subconscious brain functions underlying emotional decision-making. Based on the assumption that somatic processes, in particular orienting and its neuro correlate, precedes conscious emotional decision, the scientific goal is to identify the neuro precursors as well a behavioral principles that determine emotional decision, such as preference. This will provide significant seeds for bioengineering applications, including BMI (Brain Machine Interface), neural feedback, clinical and educational training device, entertainment and games. Thus, as a whole, this project tries to open up a new field of emotional neural interface. Five major themes are being investigated:

Psychophysics is being used to understand behavioral principles that govern preference decision making, and to identify somatic precursors to it.

The concept of implicit sensorimotor coordination is being pursued while aiming to understand the mechanisms underlying quick and autonomous neural programming from arm reaching and saccadic eye movements.

By recording the human brain it should be possible to identify neural activity signals that are correlated with, and preceding, subjective cognitive judgment such as preference, employing a variety of techniques, including EEG, MEG, fMRI, and TMS.

An animal neurophysiology approach aims to identify neural pathways and neuronal activity there that are correlated with decision-making processes preceding preference. It is also desired to understand neuropharmacological mechanisms responsible for both normal preferential, and abnormal addictive behavior.

Various applications are also being pursued, while aiming to apply the psychophysical and neuroscientific findings to a variety of bioengineering situations, such as BMI, neural feedback, clinical and educational training, entertainment and games.


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