47 pages • 1 hour read
V. S. RamachandranThe Tell-Tale Brain
V. S. RamachandranNonfiction | Book | Adult | Published in 2011A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Chapters 2-3Chapter Summaries & Analyses
Chapter 2 Summary: “Seeing and Knowing”
In Chapter 2, Ramachandran explores how the brain processes visual information and what makes human visual processing unique compared with other primates. First, the brain sees thousands of different shades via three types of cones in our eyes that sense red, blue, and green light. Humans are one of the few mammals with three cones. Most other mammals only have two.
Second, while many organisms have eyes and vision, perception is unique to humans. The brain builds a model of what a person is seeing based on information streaming into the brain from the eye. However, this model is not literally based on what our eyes see, since there is a blind spot where the retina and optic nerve connect. Humans do not perceive this blind spot, because the brain takes shortcuts filling in the missing information. Humans are not seeing the original image but a recreated image that may or may not be correct. Canonical nerves located in the frontal lobe help the brain process visual information. They fire at both a specific action (e.g., grabbing an apple) and at the site of perceived action (e.g., the site of an apple which leads to the abstract notion of graspability). Ramachandran emphasizes that “the goal of vision is not to get things perfectly right all the time, but to get it right often enough and quickly enough to survive as long as possible to leave behind as many babies as you can” (54).
Third, large portions of both human and ape brains are devoted to visual information processing. These visual areas are specialized for different aspects of vision, such as recognizing faces, color vision, and seeing shapes. Researchers do not understand the origin of these areas. The exact function these areas play in visual information processing, aside from the middle temporary (MT) and V4 areas (both located in the cortex), remains a scientific mystery.
Fourth, visual information enters the cortex through two pathways. The first is the so-called old pathway (also known as the “how” stream). It is concerned with where an object is or spatial aspects of vision. This pathway enables organisms to orient towards objects and track them with our head and eyes. Damage to this pathway causes tunnel vision. The second pathway is called the new pathway (also known as the “what” stream). This pathway allows the brain to process and recognize complex objects and scenes. Ramachandran adds a third pathway (the “so what” stream), which he believes causes humans to have emotional responses to objects. This pathway enables humans to process visual information more quickly by sending the information straight to the amygdala, located in the medial temporal lobe. The amygdala represents the body’s core fear system. Being able to process information more quickly likely conferred survival benefits on our ancestors.
To support his assertion that vision occurs in the brain rather than the eyes, Ramachandran explores several clinical examples of how damage to parts of the brain known for visual information processing impacts peoples’ perception and visual experiences.
Chapter 3 Summary: “Loud Colors and Hot Babes: Synesthesia”
Ramachandran focuses on synesthesia, a perceptual experience where two senses become blended, in Chapter 3. People experience synesthesia in different ways, including tasting color, hearing shapes, seeing sounds, and touching emotions, although the most common type of synesthesia is experiencing color when individuals see numbers. He discusses four aspects related to this phenomenon.
First, Ramachandran demonstrates that synesthesia is real. Synesthesia is not universally accepted by the scientific community as a legitimate phenomenon. Some scientists believe patients are lying about or exaggerating their unique experiences. Ramachandran reminds readers of an important human limitation: We will never truly know if another person’s experiences, including related to color, are like our own. This limitation makes studying other people’s perceptions tricky. Ramachandran designed several different experiments on two women who claimed to be synesthetes, Francesca and Mirabelle, to determine whether this was a legitimate condition. His findings provided proof that synesthesia was real.
Second, Ramachandran proposes a theory to explain what is going on in the brains of synesthetes. He suggests that cross-wiring or cross activation of neurons might partly explain the cause. The brain assigns different jobs to different parts of the brain. Color information and numerical computation occur in adjacent areas. Neural cross-wiring between these two areas could theoretically lead to number-color synesthesia.
Third, Ramachandran focuses on why this cross-wiring occurs. He suggests it is due to a mutant gene. All brain regions are connected to one another in a fetal brain, resulting in gross excess and redundancy of connections. Between the ages of two and ten, the brain undergoes synaptic pruning, removing unnecessary connections and synapses. The mutant gene might lead to incomplete pruning in areas close to one another, resulting in cross-wiring. Ramachandran and other colleagues used brain imaging to demonstrate the veracity of the cross-wiring hypothesis.
Finally, Ramachandran explores why evolution has not removed this perceptual experience from the human population. He believes evolution has kept this gene mutation in the gene pool because it confers survival advantages upon humankind.
Ramachandran ends by suggesting that humans might be able to better understand our consciousness and our higher intelligence compared with other species by developing ways to activate or silence particular neurons. He believes this ability will occur within our lifetimes.
Chapters 2-3 Analysis
Ramachandran continues to bust fallacies and myths in this section. “Homunculus fallacy” related to vision represents one example. At a dinner party, Ramachandran struck up a conversation with a creationist who believed that the exact image of something is streamed into the eye. This image, however, is upside down, and must be right-sided before the brain sees it (and thus you see it). Ramachandran calls this a homunculus theory because there would have to be an infinite number of people (a homunculus) trying to interpret images, without the problem of perception ever being solved. Ramachandran emphasizes that vision does not occur in the eyes but the brain. What humans see is a symbolic representation of the object and not the object’s actual self.
Ramachandran also refutes the commonly-held belief that synesthetes were lying about their perceptual experiences, reflecting one aspect of The Impact of Neurological Disorders. One physician even diagnosed his patient with schizophrenia rather than synesthesia, prescribing her antipsychotic medications. His work shows that this is a true condition. Ramachandran also uses opportunities like this to emphasize two key points. First, scientists and doctors need to listen to their patients. He notes most patients are describing their experiences accurately and physicians and researchers can use these details as a jumping-off point to build experiments that will help them understand what is happening to the person and their brain. Second, researchers need to use multiple lines of evidence to provide support for a theory. While Ramachandran believed his patients were synesthetes, he still conducted different experiments with them (e.g., measuring their facial expressions and galvanic skin responses). By using multiple lines of evidence, he could show without a doubt that synesthesia was a real condition.
As part of his popular science writing style, Ramachandran also reprints optical illusions to help readers understand the difference between perception and visualization. These two concepts can sometimes be used synonymously or confuse non-specialists. Ramachandran provides explicit instructions for how to view each of the optical illusions so readers can see the points he is trying to make. These optical illusions help demystify two complex subjects, making the knowledge contained within the section more approachable to a lay audience.
Ramachandran also deploys stories about several of his patients in this section, which is another popular science writing method. One example is David, who lost the ability to emotionally respond to familiar faces (called Capgras syndrome). He believed his mother was an imposter, yet could talk to her on the phone. Ramachandran uses stories like this one to show the true impact these disorders have on the human experience.
Finally, Ramachandran also continues to build on his theory that evolution is key to understanding how the brain works, reflecting the theme of Evolution and Brain Development. For example, humans are especially good at grouping and segregating similar features. Ramachandran suggests that one evolutionary explanation for this ability is that our ancestors needed to discover hidden objects, especially those that were dangerous. For instance, if a lion is hiding behind green foliage, the image that enters the eye includes only shades of green broken up by yellow spots. The brain knits together this image, assuming a low probability that the yellow spots are truly independent of one another. It sends this information to the amygdala, igniting a person’s fight-or-flight instinct. Doing so ensures that a person survives to pass on their genes.
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