Human Brain (01:57)
The human brain, a three pound, Jell-O-like mass, is the most complex thing scientists have discovered in the entire universe. The brain interprets information and transforms it into a multi-sensory reality.
What is Reality? (02:00)
Passersby examine an optical illusion, finding that the brain attempts to understand color in surprising ways. A cast shadow on a checkerboard pattern skews color perceptions, but the brain recognizes the shadow.
Stuff of Reality (02:48)
The brain is located inside the skull, inside the head, which is a sealed chamber isolated from all light and sound. In order to perceive light, sound, and much more, electrochemical signals are fired off in the brain constantly. Through millions of years of evolution, the brain combs through information, distinguishes patterns, and assembles a reality.
Cornea Transplant (02:57)
Doctors performed a cornea transplant using cutting edge stem cell research on a man who had been blinded at age three. The result was medically successful, but for the patient, overwhelming and confusing, as his brain did not have any semblance of facial recognition or depth perception.
Construction of a Visual Reality (02:18)
Ten years after his cornea transplant, Mike still relies on a guide dog to navigate around and is unable to identify facial expressions, demonstrating the complexity of the brain's visual processes. Despite receiving a pair of perfectly functioning new eyes, his vision was still severely impaired because his brain reprogrammed the visual areas of the brain, utilizing those areas for other sensory purposes.
Visual Experiments (03:31)
Neuroscientist Alyssa Brewer of the University of California is conducting a study involving goggles that flip subjects' visual world via prisms. Dr. Eagleman demonstrates the experience of wearing these goggles, showing how tricky it is to relearn reality with a skewed visual perception.
Constructing a New Reality (02:36)
Test subject Brian, who has been wearing the visual reality goggles for a week, and Eagleman attempt a maze, showing that Brian's entire visual reality is reshaping in alignment with the goggles. Brewer explains that after one week, subjects usually begin behaving normally while wearing the goggles, and that it usually takes a day for normal behavior patterns to return after cessation of the goggles.
Humans begin learning how to see as infants, and touching things is crucial to this learning. Sensory information taken in by the eyes is only useful to the brain when it is cross-referenced and contrasted with other senses, like touch and hearing.
Information Processing (03:36)
It takes time between hearing a loud sound, such as a gunshot, to the brain processing the information and then reacting to it. Eagleman displays this with an experiment at a race track, as racers do not begin to move the moment the gun fires, but 2/10th of a second prior. Racers react even slower to a light in place of a noise, despite light traveling faster than sound. Involving nearly one third of the brain, the visual system is more complicated.
Conjuring Reality (02:54)
Because the brain takes time to understand events, there is a distinct and unalterable gap between an event happening and the brain's interpretation of it— about half of a second. Dr. Eagleman suggests understanding the brain and its functions by way of comparison to a city, with the entire brain working together to produce a functioning network of data.
Sensory Deprivation (03:07)
In the mid-1900s, when Alcatraz Island was a prison, prisoners were sometimes confined to an isolation cell known as "the Hole" where no sight, sound, or human interaction was present. One prisoner, Robert Luke, describes the hallucinations he experienced while in the Hole for 29 days. Prisoners in other confinements report similar memories.
Internal Model (03:58)
Lots of information from the eyes passes through the thalamus before heading to the visual cortex, but six times the amount of data flows in the opposite direction which indicates that seeing depends more on information that already dwells inside the brain than light that is coursing through the eyes. The brain's internal model deduces information and makes assumptions, allowing guesswork to take the place of constant assessment.
Brain Tricks (02:11)
The brain's internal model is chiefly considered with navigation. Though the human eyes move about four times a second, their purpose is not to record, but to capture data.
Brain Mapping (03:39)
A painting called The Unexpected Visitor was used in the 1960s by a Russian psychologist in order to discern what the brain deems is important enough to remember when viewing a scene. This experiment is recreated. Color as humans perceive it does not really exist, but the brain comprehends wavelengths in the form of colors.
Electromagnetic Spectrum (02:42)
Specialized biological receptors allow the brain to interpret color in the electromagnetic spectrum, but other rays are undetectable without tools. This is not limited to sight, but to all senses. Other species have other specialties, such as the dog's incredible sense of smell.
Personal Reality (02:55)
Neurological phenomenon, such as synesthesia, indicate that not everyone's reality is identical. A person with synesthesia describes the associations her brain makes with letters and colors. This condition can differ from color associations to time, space, or other variations.
Psychotic disorders can warp the brains of sufferers, confusing reality with dream states. Professor Elyn Saks describes schizophrenic episodes. Through medication and counseling, Saks has been able to teach at the University of Southern California despite the disorder.
To understand why the brain sometimes perceives time as unusually slow, Eagleman uses falling as an example. Professional wingsuit flyer Jeb Corliss describes a near-fatal fall he had in which time felt drastically slowed down.
When the body and brain are in survival mode, such as during the aftermath of Corliss' accident, the amygdala starts operating at a more intense level than usual, forcing the entire brain to focus on the immediate situation. Memories are vivid and carefully constructed, available for later use if need be. However, the memories are distorted, appearing to have taken a longer time than possible.
Credits: What is Reality? Part 1: The Brain with David Eagleman (01:54)
Credits: What is Reality? Part 1: The Brain with David Eagleman
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