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Susan Dorfman's Mini Project #1 Blindsight

Susan Dorfman's picture

Have you ever understood and recorded in memory quickly an emotional response to you from another person? I have. I remember traveling to another state for a surprise party I planned and executed for a relative-in-law and detecting immediately her distaste that I was there. Of course, she did not know my role in making the celebration of her life cycle event happen. It was not the words she spoke or the facial expression she adopted, but the fleeting emotion she expressed on her face as she turned to my spoken, “hello.”She recovered in an instant; milliseconds passed.  It happened another time when I also traveled out of state for another surprise party for a different relative-in-law who, upon seeing me approach, registered briefly her disgust that I was there.  In both instances, I felt that I had seen true feelings being expressed that both women, if questioned, would have denied existed.

Over the course of my life, other instances such as this have given me the confidence to trust my intuitions about people’s responses to me. I did not understand it. I found it could be troublesome in that I then reacted to negative information that the person did not know I had. It took a long time for me to learn not to be hurt by the knowledge and to exercise care in my response. I learned that the knowledge was helpful in my long term relationships with people who harbored negative feelings toward me.

These experiences are difficult to share with those who have not experienced them and consciously analyzed them. People may think me to be paranoid or insecure if I relate my experiences or reactions to these kinds of experiences, so I rarely discuss them.  I have tried to explain them to my husband and daughter.

Every summer, I look for current science articles of interest to me that I want to share with my incoming AP Biology students as a summer assignment. I assign the articles and request short essays in response to questions I pose to the students. The essays are graded for effort and thoughtfulness rather than for correctness of response. One of the articles I chose this year was, “Uncanny Sight in the Blind” by Beatrice De Gelder in Scientific American, May, 2010.

Aside from the benefit of helping my new students to gain a handle on the complexity and multilayered functioning of the brain, this article gave me a better understanding of my intuition into people. It is not that I have any great gift or that I am psychic, I have just been able mysteriously to consciously tap into the tip of the iceberg of my unconscious processing. The article explained how regions in my midbrain, are translating visual signals that occur too quickly to be perceived consciously by my visual cortex.

In her article, De Gelder reports the history of blindsight, called residual vision when it was first described in soldiers injured during World War I. In 1973 at MIT, Poppel, Held, and Frost measured eye movements in a patient. They presented stimuli that the patient could not see consciously and observed that the patient “had a slight tendency to look toward the stimuli.” Experimentation using neuroimaging provided direct evidence of those brain regions and pathways activated during blindsight experiences. People are capable of detecting unconsciously “color, simple shapes such as X and O, simple motion, and the orientation of lines or gratings. Large shapes, as well as very fine detail, seem hard to detect.”

Beatrice De Gelder has done much research into blindsight, both navigational blindsight and emotional blindsight. De Gelder and her colleagues repeated an animal study done by Weiskrantz and Humphrey in the 1970’s, but they used a patient (TN) whose primary visual cortex no longer received incoming signals following two strokes. The researchers placed obstacles in a hallway, asked their blind patient to walk down the hallway after telling him it was empty, and filmed the trial. TN successfully avoided all the obstacles. He was unaware of his maneuvers. When questioned afterward, he could not describe anything but a simple walk down an empty hallway. When told what had happened, he could not describe his actions or any of the obstacles. De Gelder explains that movement is an essential task related to animal survival, and that we should not be surprised that the brain has evolved unconscious support for the physical navigation necessary for survival.

De Gelder also states that social animals, such as humans, rely on another kind of navigation necessary for survival- that needed to understand other people, who they are and the meaning of their gestures and other signs of thought. They studied a patient who had lost visual cortex on the left side in childhood (so he was blind on the right side of his visual field). This patient (GY) could guess the facial expressions on people he could not consciously see but could not identify personal identity or gender.  De Gelder also studied emotional contagion where a person matches their own facial expression to those of others they can see.  These studies used facial electromyography with specifically placed electrodes recording nerve signals to muscles utilized for smiling or frowning. GY reacted emotionally to images presented on both sides of his visual field. In fact, the unseen fearful images produced the strongest reaction. GY’s conscious observances were weaker and slower.

Keeping in mind De Gelder’s observation that navigation and interpretation of emotions are survival tools of social animals such as humans, it is not surprising that the deeper areas of the brain involved in blindsight and blindsight of emotions evolved long before the cortex. It is a system that is non conscious but operates “in parallel with the normal, predominantly cortical, processing routes.” De Gelder suggests that the regions responsible for blindsight in the cortically blind are the superior culliculus and the amygdala, both of which are located in the midbrain. They contribute “to visually guided behavior in a way that is apparently separate from the pathways involving the cortex and entirely outside conscious visual experience.”

OK, so I don’t feel so weird now. Perhaps I just learned to compensate for my auditory processing deficiencies by focusing intently on facial expression. At some point in my development, I may have needed to learn to do this quickly to follow and understand a conversation among several people. At some mysterious point, my conscious met my unconscious.

At a previous BMC Summer Institute, I became aware of student reaction to teachers’ facial expressions and how that, as well as tone of voice and body language, could affect their learning. As educators, we have to remember that our students are responding at the unconscious level as well as the conscious level to the conversations we have and the in-class activities we use to enhance, and maybe inadvertently compromise, their learning. 

Source: Beatrice De Gelder, "Uncanny Sight in the Blind," Scientific American, May 2010, Volume 302 Number 5, pages 60-65.

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