People Sciences

A collection of snippets and references on how we think, act, and the design of our brain.

Neuroscience

TODO: make a subpage or a pdf for notes. This is too long

• “Studies of twins have established that the concordance for schizophrenia in monozygotic twins is about 45%, but in dizygotic twins only about 15%, about the same as for other siblings.”
• Memory:
  • “Moreover, once information is stored, later recall is not an exact copy of the information originally stored. Past experiences are used in the present as clues that help the brain reconstruct a past event. During recall we use a variety of cognitive strategies, including comparison, inferences, shrewd guesses, and suppositions, to generate a consistent and coherent memory.”
  • To me it seems like long term memory are stored in neuronal connections, while short term memory is like computer RAM - stored in the temporary synapse activation arrangement, flushed after seizure (~reboot of brain) (caused by the ECT therapy). “Studies of memory loss in patients undergoing electroconvulsive therapy (ECT) for depression…” “The patients were tested before ECT and then again afterward (with a different set of television programs). Both before and after ECT recall of the programs was more correct for more recent years. After ECT, however, the patients showed a significant but transitory loss of memory for more recent programs, while their recall of older programs remained essentially the same as it was before ECT (Figure 62-11). One interpretation of these findings is that until memories have been converted to a long-term form, retrieval (recall) of recent memories is easily disrupted. Once converted to a long-term form, however, the memories are relatively stable. With time, however, both the long-term memory and the capacity to retrieve it gradually diminish, even in the absence of external trauma. Because of this susceptibility to disruption, the total set of retrievable memories changes continually with time.”
  • Short term vs long-term memory (or the condition that the movie ‘Memento’ was based off): “What H.M. now lacked, and lacked dramatically, was the ability to transfer new short-term memory into long-term memory. He was unable to retain for more than a minute information about people, places, or objects. Asked to remember a number such as 8414317, H.M. could repeat it immediately for many minutes, because of his good short-term memory. But when distracted, even briefly, he forgot the number. Thus, H.M. could not recognize people he met after surgery, even when he met them again and again. For example, for several years he saw Milner on an almost monthly basis, yet each time she entered the room H.M. reacted as though he had never seen her before. H.M. had a similarly profound difficulty with spatial orientation. It took him about a year to learn his way around a new house. H.M. is not unique. All patients with extensive bilateral lesions of the limbic association areas of the medial temporal lobe, from either surgery or disease, show similar memory deficits.”
• On sleep:
  • “Rats that are chronically deprived of sleep show an increase in preferred ambient temperature of 10°C or more. These facts suggest that sleep has cooling functions. On the other hand, rats deprived of sleep for two weeks show a significant drop in body temperature in spite of a doubling of metabolic rate, suggesting that sleep may also have a role in heat retention.”
  • My own dreams became blurrier as my eyesight got worse. As I started wearing contacts and glasses, I started seeing clearer dreams.
• Sight:
  • Recovery from blindness:
    • The first known case of published recovery from blindness is in 1728, of a blind 13-year-old boy by William Cheselden.[4] Cheselden presented the celebrated case of the boy of thirteen who gained his sight after removal of the lenses rendered opaque by cataract from birth. Despite his youth, the boy encountered profound difficulties with the simplest visual perceptions. Described by Cheselden: When he first saw, he was so far from making any judgment of distances, that he thought all object whatever touched his eyes (as he expressed it) as what he felt did his skin, and thought no object so agreeable as those which were smooth and regular, though he could form no judgment of their shape, or guess what it was in any object that was pleasing to him: he knew not the shape of anything, nor any one thing from another, however different in shape or magnitude; but upon being told what things were, whose form he knew before from feeling, he would carefully observe, that he might know them again;[5]”
    • May still has no intuitive grasp of depth perception. As people walk away from him, he perceives them as literally shrinking in size.
    • “Indeed, modification of synaptic connections is thought to be the physiological basis of learning. In the 1930s it became apparent that the common practice of removing congenital binocular cataracts between the ages of 10 and 20 resulted in permanent impairment of the ability to perceive shape and form. Even long after the cataracts were removed, patients had difficulty recognizing shapes and patterns. Similar results were obtained in more controlled studies of newborn monkeys that had been raised in the dark for the first 3-6 months of their lives. When these monkeys were later introduced to a normal visual world they could not discriminate even simple shapes. It took weeks or months of training to teach them to distinguish a circle from a square, whereas normal monkeys learn this distinction in days. “

  • “In a key experiment Hubel and Wiesel raised a monkey from birth to six months of age with one eyelid sutured shut, thus depriving the animal of vision in that eye. When the sutures were removed and the eye was exposed to light, it became clear that the animal was blind in the deprived eye. The blindness was largely cortical. The retinal ganglion cells in the deprived eye and the cells in the lateral geniculate nucleus that received input from that eye responded well to visual stimuli and had relatively normal receptive fields, but most cells in the visual cortex no longer responded to visual input to the deprived eye (Figure 56-2). The few cortical cells that were responsive were not sufficient for visual perception. Not only had the deprived eye lost its ability to drive most cortical neurons, but this loss was irreversible. Thus proper vision was necessary for the maturation or maintenance of the connections from the lateral geniculate nucleus to the visual cortex. Further analysis revealed two surprising results. First, whereas most cortical cells are driven only by the eye that remains open following monocular deprivation, many cells remain responsive to both eyes following binocular deprivation. This result suggested that appropriate connections depend not only on activity in the afferent pathways but also on a proper balance between those inputs. Second, whereas deprivation of sight in one eye for as little as one week during the first six months of life results in a nearly complete loss of vision in that eye, a much longer period of visual deprivation in an adult has little effect on cortical responsiveness or visual perception. These results led to the concept of a critical period in the maturation of the cortical connections that control visual perception.”

  • “Six different systems control the eye. Fixation keeps the fovea still on a target; saccades move the fovea from one object of interest to another; smooth pursuit keeps the fovea on a moving target; vestibular and optokinetic movements keep the eye still in space when the head moves; and vergence adjusts the individual angles of each eye to keep objects at a certain depth focused on equivalent retinal positions. In addition, movements of the head help position the fovea on a target in the visual field. Combined eye and head movements are called gaze movements.”
• Dislexia: “Most children with dyslexia have not developed phonological awareness: the ability to attend to individual sounds, particularly phonemes, in the continuous speech wave and to associate them with letters. However, they understand other communicative symbols—such as traffic signs or words—that have a unique visual appearance, such as the Coca Cola trademark. Indeed, studies in the United States have shown that some dyslexic children can learn to read English when entire words are represented by single characters rather than a sequence of characters. Another possible problem in dyslexia is an inability to process transient sensory input quickly. The normally rapid conduction in the magnocellular pathway of the visual system (Chapter 27) is below average in people with dyslexia, whereas conduction in the parvocellular pathway is normal. In particular, dyslexic patients have difficulty processing fast, high-contrast, visual stimuli. A plausible anatomical correlate of this disorder is seen in some dyslexic patients examined at autopsy: the cells in the magnocellular layers of the lateral geniculate nucleus are abnormally small compared to parvocellular layers and compared to magnocellular layers in control subjects. A similar defect is sometimes evident in the fast-conducting component of the auditory pathways (Chapter 30).”
• How brain handles information overload: “The brain resolves the conflict between information overload from a huge number of receptors and the need for resolution of spatial detail by having a higher density of receptors in regions of the body where high resolution of detail is behaviorally important and using progressively lower numbers of receptors in surrounding regions.”
• Language:
  • “Intensive scientific investigation by linguists and psycholinguists in the past 40 years has revealed that all languages are based on remarkably similar design principles and that language emerges spontaneously in all normal children in all societies. Language thus appears to be a species-wide adaptation and, as we shall see, is supported by neural circuitry of considerable complexity.”
• Development:
  • “The first compelling evidence that early social interactions with other humans is essential for normal social development came in the 1940s from the work of the psychoanalyst René Spitz. Spitz compared the development of infants raised in a foundling home with the development of infants raised in a nursing home attached to a women’s prison. Both institutions were clean and both provided adequate food and medical care. The babies in the prison nursing home were all cared for by their mothers, who, although in prison and away from their families, tended to shower affection on their infants in the limited time allotted to them each day. In contrast, infants in the foundling home were cared for by nurses, each of whom was responsible for several babies. As a result, children in the foundling home had much less contact with other humans than those in the prison’s nursing home. The two institutions also differed in another respect. In the prison nursing home the cribs were open, so that the infants could readily watch other activities in the ward; they could see other babies play and observe their mothers and the staff go about their business. In the foundling home the bars of the cribs were covered by sheets that prevented the infants from seeing outside. This dramatically reduced the infants’ environment. In effect, the babies in the foundling home lived under conditions of sensory and social deprivation. Groups of newborn infants at the two institutions were followed throughout their early years. At the end of the first four months the infants in the foundling home fared better on several developmental tests than those in the prison nursing home. However, by the end of the first year the motor and intellectual performance of the children in the foundling home had fallen far below that of children in the prison nursing home. Many of the children in the foundling home had developed a syndrome that Spitz called hospitalism (now often called anaclitic depression). These children were withdrawn and showed little curiosity or gaiety. Remarkably, they were also prone to infection. By their second and third years children in the prison nursing home were similar to children raised in normal families at home: They walked well and talked actively. In contrast, the development of the children in the foundling home was still delayed. Very few children in the foundling home were able to walk and speak; those who could speak said only a few words. Normal children at this age are agile, have a vocabulary of hundreds of words, and speak in sentences. This work was carried one important step further in the 1960s when two psychologists, Harry and Margaret Harlow, studied monkeys reared in isolation. They found that newborn monkeys isolated for 6-12 months were physically healthy but behaviorally devastated. These monkeys crouched in a corner of their cage and rocked back and forth like autistic children. They did not interact with other monkeys, nor did they fight, play, or show any sexual interest. Thus a 6-month period of social isolation during the first 18 months of life produced persistent and serious disturbances in behavior. By comparison, isolation of an older animal for a comparable period lacked such drastic consequences. It is plausible that the devastating consequences of early social deprivation are caused by structural defects in brain development, much as early visual deprivation results in changes in the organization of the visual cortex.”
• Perception of self:
  • ““I”—is achieved through the connection of independent circuits, each with its own sense of awareness, that carry out separate operations in our two cerebral hemispheres. The remarkable discovery that even consciousness is not a unitary process was made by Roger Sperry and Michael Gazzaniga in the course of studying epileptic patients in whom the corpus callosum—the major tract connecting the two hemispheres—was severed as a treatment for epilepsy. Sperry and Gazzaniga found that each hemisphere had a consciousness that was able to function independently of the other. The right hemisphere, which cannot speak, also cannot understand language that is well-understood by the isolated left hemisphere. As a result, opposing commands can be issued by each hemisphere—each hemisphere has a mind of its own! While one patient was holding a favorite book in his left hand, the right hemisphere, which controls the left hand but cannot read, found that simply looking at the book was boring. The right hemisphere commanded the left hand to put the book down! Another patient would put on his clothes with the left hand, while taking them off with the other.”
• “Neurons fire with a safety factor to account for variance. So the muscle action potential is lower than the potential produced by the neurons.”
• “up to 100 million ions may pass through a single channel per second.”

Learning how to learn (notes pdf)

Nudge book and intuition on fast/slow thinking