Posts Tagged ‘hallucinations’

Visiting the Clinic

September 8, 2018

The title of this post is the same as the title of a section in Michael Gazzaniga’s outstanding book, “The Consciousness Instinct: The first patient suffers from the most common type of dementia, Alzheimer’s disease. When Dr. Gazzaniga shakes his hand, the patient returns the shake in acknowledgment, but is confused as to who he is. He doesn’t remember meeting him a couple of days before. The disease results in the slow destruction of the brain, commencing with the loss of neurons in the entorhinal cortex and the hippocampus resulting in the failure to store new memories. The disease can become so debilitating that it can completely reshape personality, transforming from a lively and caring person into a listless shell of his former self. Although he does not recognize Dr. Gazzaniga, he is still cognizant of social niceties and shakes his hand. He may wander off, but he will still feel fear when confused and lost, and anger when frustrated. His conscious experience of the world is brought to him through whatever operational neural circuitry continues to function, and as he loses function, it becomes more restricted. The contents of that conscious experience most likely are odd, very different from those of the normal brain or his past self. As a result, odd behavior follows. For example, the listless version of the formerly jovial grandfather, may still describe himself as his earlier “life of the party” version. Caretakers and family members often attribute a patient’s incongruent self-identify to the disorienting nature of the disease. Still, when friends and family describe the premorbid personality of a loved one, it is strikingly similar to the self-description provided by the individual in the disease state. This suggests that his false beliefs about his current personality traits are likely due to an inability to update those beliefs. A functioning hippocampus is required to update those beliefs. So dementia has left him with an outdated self-image. As long as his heart continues to beat, consciousness, albeit with a checkerboard of altered contents, will survive the carnage of his degenerating brain.

The next patient is known as Mr. B. He has a different kind of problem. He believes he is of special interest to the FBI, which monitors him every single moment of the day. Not only that, the FBI agents film and broadcast his life to the public as “The Mr. B Show.” Disturbed by this, Mr. B. attempts to avoid embarrassing situations by adjusting his behavior, He wears a bathing suit every time he showers, and he changes his clothes under the cover of bed sheets. He avoids social situations, knowing that everyone he encounters is an actor trying to elicit drama to make “The Mr. B Show” more intriguing. It’s hard to imagine what it would be like to live in Mr. B’s world. Yet, when carefully analyzed, Mr. B’s case may reveal that a totally rational and normal cortex is trying to make sense out of some abnormalities going on in another region of the brain, the sub cortex.

Mr. B suffers from chronic schizophrenia. His factors for the disease include a genetic vulnerability and gene-environmental interactions. Environmental factors that increase the risk include growing up in urbanized areas, being an immigrant, especially when socially isolated—such as living in an area with few others of the same group—and exposure to cannabis. No matter what evidence is provided to combat Mr. B’s false beliefs, he is profoundly convinced that he is constantly being viewed by millions of people. A first-rank symptom of schizophrenia is the perception that particular stimuli, ranked unimportant when in a non-delusional state, are extremely and personally significant: the guy who glances up from his newspaper is deliberately looking at you; the rock on the road was deliberately placed to harm you. This alteration in salience, who is important and draws one’s attention, is such a classic feature of schizophrenia spectrum disorders that there is a growing movement pushing for the tag “schizophrenia” be abandoned and the disorder reclassified as a “salience syndrome.”

A sensory input becomes more salient when the neural signal that it elicits is enhanced over others, which draws attention to it. Shitij Kapur, a psychiatrist, neuroscientist, and professor at King’s College London, distinguishes for us the difference between hallucinations and delusions: “hallucinations reflect a direct experience of the aberrant salience of internal representations,” whereas delusions (false beliefs) are the result of “a cognitive effort by the patient to make sense of these aberrantly salient experiences. In the brain, the amount of the neurotransmitter dopamine affects the process of salience acquisition and expression. During an acute psychotic episode, schizophrenia is associated with an increase in dopamine synthesis, dopamine release, causing abnormal firing of the dopamine system, leading to the aberrant levels of the neurotransmitter and, thus, aberrant assignment of motivational salience to objects, people, and actions. With this in mind, the behavior that results from his cognitive conclusion seems somewhat more rational. Despite suffering the altered brain function, Mr. B continues to be conscious and aware of his existence.

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Predict the Future

January 12, 2017

HM works from his iPAD.  This is the print title of an article by Diana Kwon in the October 1 issue of the New Scientist.  The healthy memory blog has stressed the importance of the unconscious mind and provided suggestions as to how to make use of your unconscious mind.  This blog post taken from this issue of the New Scientist elaborates on this idea.

Every moment the brain takes in an enormous amount of information, more than it can process on the fly.  To cope effectively with this enormous amount of information, the brain constantly makes predictions that it tests by comparing incoming data against information.  And most of this is done via unconscious processing.

Just imagining the future is enough to put the brain in motion.  Imaging studies have shown that when a sound or image begin to appear, the brain generates an anticipatory signal in the sensory cortex.

The brain is continuously predicting the sounds, words, and meanings that we are trying to produce or communicate..

Moreover, the senses are used to inform each other.  When a recording of speech is degraded so that it is nearly unintelligible, the words sound clearer if you have previously read the same words in subtitles.  Matt Davis at the MRC Cognition and Brain Sciences Unit in Cambridge, says that “the sensory parts of the brain are comparing the speech we’ve heard to the speech we’ve predicted.”

Our brains also make predictions on the basis of emotional signals coming from our bodies.  Moshe Bar, a neuroscientist at Bar-Han University in Israel, suggests that we only consciously recognize an object once our unconscious mind has calculated its importance based on what our senses and emotional reactions our saying.  For example, the conscious fear of a snake on a hiking trail comes after the brain has processed the shape and initiated jumping out of the way.

There are downsides to making predictions. Incorrect inferences reinforced by repetition can be hard to reverse.  Stereotyping is an even more troublesome example of the same thing.  When it comes to human interactions it can lead to negative biases and discrimination.  Bar says that “stereotypes and prejudices are predictions working as they do with everything else, but in a way that is not desirable.”  Some neuroscientists also believe that the hallucinations experienced in psychosis are the result of expectations gone awry.  Despite its flaws predictions are necessary.  Otherwise our species never would have survived.