Consciousness Enters the Lab

Consciousness Enters the Lab is the First chapter discussed in “Consciousness and the Brain”  Deciphering How the Brain Codes our Thoughts,” which is an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.  As was discussed in the previous post, although consciousness is an extremely important concept, it has been difficult to bring it into the lab and conduct meaningful experiments regarding it.  This first chapter discusses the new methodology.

This first chapter focuses on the issue of conscious access, the question being why some of our sensations turn into concept perceptions, while others remain unconscious.  The methodology builds upon one of the oldest in psychophysics, the identification of thresholds.  This involved presenting a stimulus and asking the respondent if it can be perceived.  Brain imaging is then added to this technology to see what parts of the brain are responding.  The signature of consciousness is found in those parts of the brain that respond when the individual indicates the presence of the stimulus.  Parts of the brain will also be responding when the individual does not indicate the presence of the stimulus.  These are the parts of the brain that, although they are activated, do not result in conscious perception.  Remember that most of the brain’s activity is unconscious.  Conscious activity represents only a very small percentage of the brain’s activity, but the parts of the brain that do respond with the individual’s indication that the stimulus is perceived, are those parts that are conscious.  This procedure was invented/discovered  by the late Nobel Prize winner Francis Crick and the neurobiologist Christof Koch.

The procedure is not as simple as it appears.  The identification of a reliable threshold requires multiple trials.  This procedure is also done with multiple participants.  So there are many brain images over many participants.  But when done properly, reliable signatures of conscious activity are identified for the relevant parts of the brain.  Thus, consciousness becomes  a meaningful measure for scientific study.

Scientists have often referred to consciousness as “wakefulness” or “vigilance..”  But wakefulness refers primarily to the sleep-wake cycle. And vigilance refers to the level of excitement in the cortical and thalamic networks that support conscious states.  However, both concepts differ sharply from conscious access.  Wakefulness, vigilance, and attention are enabling conditions for conscious access.  Selective attention and conscious access are also distinct processes.  In many cases attention operates sub rosa, covertly amplifying or squashing incoming information even though the final outcome never makes it into our awareness.

Of course, scientists are creative and there are variants on the above technique.  But the primary point has been made.  We are remain unaware of the vast majority of the activity in the brain.  However, signatures can be developed to identify parts of the brain that reflect conscious activity.


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