Lucy info page

Notes from "The brain that changes itself" - Norman Doidge

- p. 36-37 - Barabara Arrowsmith Young “designed exercises for the brain areas most commonly weakened in those with learning disabilities” working out of the Arrowsmith School. At the time of the school’s opening “few others knew about or accepted neuroplasticity or believed that the brain might be exercised as though it were a muscle.”
- p. 40 – “we all have some weak brain functions, and such neuroplasticity- based techniques have great potential to help almost everyone.”
- P. 42 – “Barbara Arrowsmith Young’s work compels us to imagine how much good might be accomplished if every child had a brain-based assessment and, if problems were found, a tailor-made program created to strengthen essential areas in the early years, when neuroplasticity is greatest. It is far better to nip brain problems in the bud than to allow the child to wire into his brain the idea that he is “stupid,” begin to hate school and learning, and stop work in the weakened area, losing whatever strength he may have. Younger children often progress more quickly through brain exercises than do adolescents, perhaps because in an immature brain the number of connections among neurons, or synapses, is 50 percent greater than in the adult brain. When we reach adolescence, a massive “pruning back” operation begins in the brain, and synaptic connections and neurons that have not been used extensively suddenly die off – a classic case of “use it or lose it.” It is probably best to strengthen weakened areas while all this extra cortical real estate is available.”
è IMPORTANT AREA OF FUTURE RESEARCH (?) –the idea of heightened neuroplasticity in early childhood lends support to the case for early intervention, not only for clearly disabled children but children who may only have slight weaknesses in certain areas
- p. 35 – “Mark Rozenweig of the University of California at Berkley had studied rats in stimulating and nonstimulating environemts, and in post-mortem exams he found that the brains of the stimulated rats had more neurotransmitters, were heavier, and had better blood supply than those from the less stimulating environments. He was one of the first scientists to demonstrate neuroplasticity by showing that activity could produce changes in the structure of the brain.”
P. 43 – “Over the years his labs and others have shown that stimulating the brain makes it grow in almost every conceivable way. Animals raised in enriched environments – surrounded by other animals, objects to explore, toys to roll, ladders to climb, and running wheels – learn better than genetically identical animals that have been reared in impoverished environments. Acetylcholine, a brain chemical essential for learning, is higher in rats trained on different spatial problems than in rats trained on simpler problems. Mental training or life in enriched environments increases brain weight by 5 percent in the cerebral cortex of animals and up to 9 percent in areas that the training directly stimulates. Trained or stimulated neurons develop 25 percent more branches and increase their size, the number of connections per neuron, and their blood supply. These changes can occur late in life, though they do not develop as rapidly in older animals as in younger ones. Similar effects of training and enrichment on brain anatomy have been seen in all types of animals tested to date.
For people, post-mortem examinations have shown that education increases the number of branches among neurons. An increased number of branches drives the neurons further apart, leading to an increase in the volume and thickness of the brain. The idea that the brain is like a muscle that grows with exercise is not just a metaphor.”

- p. 51-52 – In the 1960s Hubel and Wiesel “discovered that the brain in very young animals is plastic. David Hubel and Torsten Wiesel were micromapping the visual cortex to learn how vision is processed. They’d inserted microelectrodes into the visual cortex of kittens and discovered that different parts of the cortex processed the lines, orientations, and movements of visually perceived objects. They also discovered that there was a “critical period,” from the third to the eighth week of life, when the newborn kitten’s brain had to receive visual stimulation in order to develop normally. In the crucial experiment Hubel and Wiesel sewed shut one eyelid of a kitten during its critical period, so the eye got no visual stimulation. When they opened the shut eye, they found that the visual areas in the brain map that normally processed input from the shut eye had failed to develop, leaving the kitten blind that eye for life. Clearly, the brains of kittens during the critical period were plastic, their structure literally shaped by experience...The part of the kitten’s brain that had been deprived of input from the shut eye did not remain idle. It had begun to process visual input from the open eye, as though the brain didn’t want to waste any “cortical real estate” and had found a way to rewire itself – another indication that the brain is plastic in the critical period.”
p. 52 – “Scientists soon showed that other brain systems required environmental stimuli to develop. It also seemed that each neural system had a different critical period, or window of time, during which it was especially plastic and sensitive to the environment, and during which it had rapid formative growth
- p. 63 – Merzenich’s experiments with neuroplasticity/changing of brain maps associated with the cutting of nerves in monkeys – “In 1949 Hebb proposed that learning linked neurons in new ways. He proposed that when two neurons fire at the same time repeatedly (or when one fires, causing another to fire), chemical changes occur in both, so that the two tend to connect more strongly. Hebb’s concept – actually proposed by Freud sixty years before – was neatly summarised by neuroscientist Carla Shatz: Neurons that fire together wire together.
Hebb’s theory thus argued that neuronal structure can be altered by experience. Following Hebb, Merzenich’s new theory was that neurons in brain maps develop strong connections to one another when they are activated at the same moment in time. And if maps could change, though Merzenich, then there was reason to hope that people born with problems in brain-map processing areas – people with learning problems, psychological problems, strokes or brain injuries – might be able to form new maps if he could help them form new neuronal connections, by getting their healthy neurons to fire together and wire together.
- p. 78-79 – “When we are born, our brain maps are often “rough drafts”, or sketches, lacking detail, undifferentiated. In the critical period, when the structure of our brain maps is literally getting shaped by our first wordly experiences, the rough draft becomes detailed and differentiated.
Merzenich and his team used micromapping to show how maps in newborn rats are formed in the critical period. Right after birth, at the beginning of the critical period, auditory maps were undifferentiated, with only two broad regions in the cortex. Half of the map responded to any high-frequency sound. The other half responded to any low-frequency sound.
When the animal was exposed to a particular frequency during the critical period, that simple organisation changed. If the animal was repeatedly exposed to a high C, after a while only a few neurons would turn on, becoming selective for high C. The same would happen when the animal was exposed to a D, E, F, and so on. Now the map, instead of having two broad areas, had many different areas, each responding to different notes. It was now differentiated.
What is remarkable about the cortex in the critical period is that it is so plastic that its structure can be changed just by exposing it to new stimuli. That sensitivity allows babies and very young children in the critical period of language development to pick up new sounds and words effortlessly, simply by hearing their parents speak; mere exposure causes their brain maps to wire in the changes. After the critical period older children and adults can, of course, learn languages, but they really have to work to pay attention. For Merzenich, the difference between critical-period plasticity and adult plasticity is that in the critical period the brain maps can be changed just by being exposed to the world because “the learning machinery is continuously on.”
It makes good biological sense for this “machinery” always to be on because babies can’t possibly know what will be important in life, so they pay attention to everything. Only a brain that is already somewhat organised can sort out what is worth paying attention to.”
- p. 80-81 – “BDNF [brain-derived neurotrophic factor] plays a crucial role in reinforcing plastic changes made in the brain in the critical period. According to Merzenich, it does this in four different ways.
When we perform an activity that requires specific neurons to fire together, they release BDNF. This growth factor consolidates the connections between those neurons and helps to wire them together so they fire together reliably in the future. BDNF also promotes the growth of the thin fatty coat around every neuron that speeds up the transmission of electrical signals.
During the critical period BDNF turns on the nucleus basalis, the part of our brain that allows us to focus our attention – and keeps it on, throughout the entire critical period. Once turned on, the nucleus basalis helps us not only pay attention but remember what we are experiencing. It allows map differentiation and changes to take place effortlessly...Merzenich calls the nucleus basalis and the attention system the “modulatory control system of plasticity” – the neurochemical system that, when turned on, puts the brain in an extremely plastic state.
The fourth and final service that BDNF performs – when it has completed strengthening key connections – is to help close down the critical period. Once the main neuronal connections are laid down, there is a need for stability and hence less plasticity in the system. When BDNF is released in sufficient quantities, it turns off the nucleus basalis and ends that magical epoch of effortless learning. Henceforth the nucleus can be activated only when something important, surprising, or novel occurs, or if we make the effort to pay close attention.”
- FUTURE RESEARCH POSSIBILITIES: p. 84 - “Learning in the critical period is effortless because during the critical period the nucleus basalis is always on. So Merzenich and his young colleague Michael Kilgard set up an experiment in which they artificially turned on the nucleus basalis in adult rats and gave them learning tasks where they wouldn’t have to pay attention and wouldn’t receive a reward for learning.
They inserted microelectrodes into the nucleus basalis and used an electric current to keep it turned on. Then they exposed the rats to a 9Hz sound frequency to see if they could effortlessly develop a brain map location for it, they was pups do during the critical period. After a week Kilgard and Merzenich found they could massively expand the brain map for that particular sound frequency. They had found an artificial way to reopen the critical period in adults.
They then used the same technique to get the brain to speed up processing time...
...This work opens up the possibility of high-speed learning later in life.”
- p. 88–89 – “Merzenich told me, “Everything that you see happen in a young brain can happen in an older brain.” The only requirement is that the person must have enough of a reward, or punishment, to keep paying attention through what might otherwise be a boring training session. If so, he says, “the changes can be every bit as great as the changes in a newborn.””

A potentially good article is "Aspects of the search for neural mechanisms of memory" by Rosenzweig
The search for neural mechanisms of memory has been under way for more than a century. The pace quickened in the 1960s when investigators found that training or differential experience leads to significant changes in brain neurochemistry, anatomy, and electrophysiology. Many steps have now been identified in the neurochemical cascade that starts with neural stimulation and ends with encoding information in long-term memory. Applications of research in this field are being made to child development, successful aging, recovery from brain damage, and animal welfare. Extensions of current research and exciting new techniques promise novel insights into mechanisms of memory in the decades ahead.
· Pp. 10 – 11:
Differential Experience Produces Cerebral Changes Throughout the Life Span, and Rather Rapidly
Further experiments revealed that relatively short periods of enriched or impoverished experience induced significant cerebral effects at any part of the life span. In contrast, Hubel & Wiesel reported that depriving an eye of light altered cortical responses only if the eye was occluded during a critical period early in life. Later, however, other investigators found that modifying sensory experience in adult animals—especially in the modalities of touch and hearing—could alter both receptive fields of cells and cortical maps, as reviewed by Kaas (1991), Weinberger (1995).
Initially we supposed that cerebral plasticity might be restricted to the early part of the life span, so we assigned animals to differential environments at weaning (about 25 days of age) and kept them there for 80 days. Later, members of our group obtained similar effects in rats assigned to the differential environments for 30 days as juveniles at 50 days of age (Zolman & Morimoto 1962) and as young adults at 105 days of age (Rosenzweig et al 1963, Bennett et al 1964a). Riege (1971) in our laboratory found that similar effects occurred in rats assigned to the differential environments at 285 days of age and kept there for periods of 30, 60, or 90 days. Two hours a day in the differential environments for a period of 30 or 54 days produced cerebral effects similar to those after 24-hr-a-day exposure for the same periods (Rosenzweig et al 1968). Four days of differential housing produced clear effects on cortical weights (Bennett et al 1970) and on dendritic branching (Kilman et al 1988);, Ferchmin & Eterovic (1986) reported that four 10-min daily sessions in EC significantly altered cortical RNA concentrations.
The fact that differential experience can cause cerebral changes throughout the life span, and relatively rapidly, was consistent with our interpretation of these effects as due to learning. Recall also that our original observation of differences in cortical neurochemistry came from experiments on formal training. Later Chang & Greenough (1982) reported that formal visual training confined to one eye of rats caused increased dendritic branching in the visual cortex contralateral to the open eye. Recently single-trial peck-avoidance training in chicks has been found to result in changes in density of dendritic spines (Lowndes & Stewart 1994).
Although the capacity for these plastic changes of the nervous system, and for learning, remain in older subjects, the cerebral effects of differential environmental experience develop somewhat more rapidly in younger than in older animals, and the magnitude of the effects is often greater in the younger animals. Also, continuing plasticity does not hold for all brain systems and types of experience. As noted above, changes in responses of cortical cells to an occluded eye are normally restricted to early development (Wiesel & Hubel 1963), but this restriction may itself be modifiable: Baer & Singer (1986) reported that plasticity of the adult visual cortex could be restored by infusing acetylcholine and noradrenaline. Further work showed that the plastic response of the young kitten brain to occlusion of one eye also depends upon glutamate transmission, because treating the striate cortex with an inhibitor of the glutamate NMDA receptor prevented the changes (Kleinschmidt et al 1987). Thus, whether the brain shows plastic changes in response to a particular kind of experience depends on the brain region, the kind of experience, and also on special circumstances or treatments that enhance or impair plasticity.
· Pp.12 – 13:
Experiments with several strains of rats showed similar effects of EC vs. IC experience on both brain values and problem-solving behavior, as reviewed by Renner & Rosenzweig (1987, pp. 53–54). Similar effects on brain measures have been found in several species of mammals—mice, gerbils, ground squirrels, cats, and monkeys (reviewed by Renner & Rosenzweig 1987, pp. 54–59), and effects of training on brain values of birds have also been found. Thus the cerebral effects of experience that were surprising when first found in rats have now been generalized to several mammalian and avian species. Anatomical effects of training or differential experience have been measured in specific brain regions of
Drosophila (Davis 1993, Heisenberg et al 1995). Synaptic changes with training have also been found in the nervous systems of the molluscs Aplysia and Hermissenda, as reviewed by Krasne & Glanzman (1995). In Aplysia, long-term habituation led to decreased numbers of synaptic sites, whereas long-term sensitization led to an increase (Bailey & Chen 1983); this is a case where either a decrease or an increase in synaptic numbers stores memory. Thus, as noted by Greenough et al (1990, p. 164), “experience-dependent synaptic plasticity is more widely reported, in terms of species, than any other putative memory mechanisms.”
Experience May Be Necessary for Full Growth of Brain and of Behavioral Potential
Sufficiently rich experience may be necessary for full growth of species-specific brain characteristics and behavioral potential. This is seen in recent research on differential experience conducted with different species of the crow family. Species that cache food in a variety of locations for future use are found to have significantly larger hippocampal formations than related species that do not cache food (Krebs et al 1989, Sherry et al 1989). But the difference in hippocampal size is not found in young birds still in the nest; it appears only after food storing has started, a few weeks after the birds have left the nest (Healy & Krebs 1993). Even more interesting is the finding that this species-typical difference in hippocampal size depends on experience; it does not appear in birds that have not had the opportunity to cache food (Clayton & Krebs 1994). Different groups of hand-raised birds were given experience in storing food at three different ages: either 35–59 days posthatch, 60–83 days, or 115–138 days. Experience at each of these periods led to increased hippocampal size, much as we had found for measures of occipital cortex in the rat. Thus, both birds and rats appear to retain considerable potential for experience-induced brain growth if it does not occur at the usual early age.
· Pp. 22 – 26:
Animal research on the effects of experience on brain plasticity and learning is being applied to several areas of human behavior and in other cases has been used as converging or supporting evidence. Thus it is being used to promote child development, successful aging, and recovery from brain damage; it is also being applied to benefit animals in laboratories, zoos, and farms. Let us consider a few of these kinds of application or influence briefly below.
Applications to Child Development
The findings on the effects of differential experience in animals have influenced research on child development or at least have been offered as supporting evidence in favor of giving children adequate experience. An indication of the importance of this approach comes from a major report, “Starting points: Meeting the needs of our youngest children” (1994), issued by the Carnegie Task Force on Meeting the Needs of Young Children. The tenor of the findings is indicated by this quotation:
Beginning in the 1960s, scientists began to demonstrate that the quality and variety of the environment have direct impact on brain development. Today, researchers around the world are amassing evidence that the role of the environment is even more important than earlier studies had suggested. For example, histological and brain scan studies of animals show changes in brain structure and function as a result of variations in early experience.
These findings are consistent with research in child development that has shown the first eighteen months of life to be an important period of development. Studies of children raised in poor environments—both in this country and elsewhere—show that they have cognitive deficits of substantial magnitude by eighteen months of age and that full reversal of these deficits may not be possible. These studies are based on observational and cognitive assessments; researchers say that neurobiologists using brain scan technologies are on the verge of confirming these findings.
In the meantime, more conventional studies of child development—using cognitive and observational measures—continue to show short- and long-term benefits of an enriched early environment (p. 8).
This is one of the latest contributions to a back-and-forth debate between those who hold that child development proceeds mainly from innate factors with only a small influence of the environment and those who hold that environment can make a major contribution. Gall and Spurzheim differed on this question early in the 19th century.
It is disheartening to note that despite demonstrations over 30 years that lack of adequate intellectual stimulation can cause mental retardation and that appropriate stimulation can foster normal development, few sustained attempts have been made to apply these findings. Hunt (1979), for example, in a chapter in the
Annual Review of Psychology//, presented evidence for the importance of early experience to children's intellectual development. He reviewed several studies showing substantial effects of specific kinds of environmental interventions on particular aspects of child development. One was his own study (Hunt et al 1976) demonstrating the importance of specific caretaking to assure language development of infants in a Teheran orphanage. Hunt also reviewed animal research on effects of differential experience on problem-solving, neuroanatomy, and neurochemistry—research whose inspiration he attributed to Hebb's 1949 book, and which included some of the experiments of the 1960s–1970s described above.
Several factors have complicated attempts to apply research on environmental enrichment to improve the cognitive status of children raised in poor environments. One is that some proponents have overestimated the potential effects of relatively short periods of enrichment and then have been disappointed that the effects were not larger. This has been one of the problems confronting the Head Start program which began in 1963 in the United States (Zigler & Muenchow 1992). Although this and related programs have proved beneficial and cost effective, they were unable to bring participating children up to the scholastic levels of children living in better environments. Another problem is that the human programs involve a variety of interventions, so it is difficult to determine whether the positive effects are attributable to enriched experience and training or to other causes such as improved nutrition and health care. In the words of a recent review of the effects of nutrition on child development, however, “Adequacy of the social and educational environment is as significant as nutrition for mental development (or possibly more significant)” (Sigman 1995, p. 54).
The authors of a new series of studies (Drews et al 1995, Murphy et al 1995, Yeargin-Allsopp et al 1995) conclude that the principal causes of mild retardation (IQ scores between 50 and 70) in an American city appear to be poverty and lack of education of mothers (fewer than 12 years of education). These researchers claim that many cases of mild retardation are preventable and/or treatable by appropriate early training and experience. David Satcher, the Director for the Centers for Disease Control and Prevention, which supported these studies, announced that the Centers will start a demonstration program in 1996 “aimed at promoting the cognitive, communicative, and behavioral development, as well as the health, of children born to women with fewer than 12 years of education” (Satcher 1995, p. 305). Satcher cited the report of the Carnegie Corporation, mentioned above: “[It] goes beyond questions of intellectual function and underscores the importance of early (birth to 3 years) experiential and social factors in brain development. The report emphasizes long-lasting effects of early environmental experience on both brain structure and cognitive function” (Satcher 1995, p. 305).
The problems of finding exactly which factors are most important in enhancing cognitive development should not overshadow the benefits of programs that provide environmental enrichment to children in need of it. I believe that current programs should be expanded to include more children and to retain them for longer periods. Unfortunately, in the United States such programs appear to be in jeopardy in the present political climate.
Enriched Experience Aids “Successful Aging”
Enriched experience, beginning early in life, also helps to ensure maintenance of ability into old age. Thus, infantile handling or later enriched experience helps prevent hippocampal damage caused by stress in rats. Meaney et al (1988, 1991) handled some neonatal rat pups during each of their first 21 days and left other pups unhandled. They examined cognitive function of the rats at different ages from 3 months to 24 months and also measured basal and stress levels of glucocorticoids, numbers of hippocampal neurons, and numbers of glucocorticoid receptors. Chronic excess of glucocorticoids is toxic to neurons, particularly those of the hippocampus, and aged rats are particularly vulnerable (Sapolsky 1992). Handled rats showed improved spatial memory, higher numbers of hippocampal corticoid receptors, and a more rapid return of corticosterone to basal levels after response to a stressful situation. In old age, the handled animals had lower basal levels of corticosterone and lost fewer hippocampal neurons than the unhandled ones.
Young adult rats given 30 days of EC experience beginning at 50 days of age, like rats given infantile handling, showed higher expression of the gene encoding glucocorticoid receptors in the hippocampus, and they also showed induction of genes for nerve growth factors in the hippocampus (Mohammed et al 1993, Olsson et al 1994). The investigators suggest that enriched experience in adulthood, like infantile handling, may protect the aging hippocampus from glucocorticoid neurotoxicity.
Some kinds of learning and performance decline with age after middle adulthood, but other kinds of learning and memory do not. People who continue to learn actively can maintain high levels of performance. For example, professors in their 60s perform as well as professors in their 30s on many tests of learning and memory (Shimamura et al 1995).
Beyond the age of retirement, stimulation and activity continue to contribute to health and mental status. This claim is borne out in a longitudinal study that has assessed the mental abilities of more than 5000 adults, having followed some for as long as 35 years (Schaie 1994). Among the eight variables found to reduce the risk of cognitive decline in old age, three are particularly relevant here: 1. Living in favorable environmental circumstances, as would be the case for persons of high socioeconomic status. Such circumstances include above-average education, histories of occupational pursuits that involve high complexity and low routine, above-average income, and the maintenance of intact families. 2. Substantial involvement in activities typically available in complex and intellectually stimulating environments. Such activities include extensive reading habits, travel, attendance at cultural events, pursuit of continuing education activities, and participation in clubs and professional associations. 3. Being married to a spouse with high cognitive status. Our studies of cognitive similarity in married couples suggest that the spouse who scores less well on tests of cognitive ability at the beginning of marriage tends to maintain or increase his or her scores vis-à-vis the spouse who originally scored higher (Schaie 1994, p. 312).
Terry et al (1995) report that loss of synapses correlates strongly with the severity of symptoms in Alzheimer's disease. Enriched experience produces richer neural networks in the brains of all species so far studied. If similar effects occur in humans, as seems likely, the resulting reserves of connections may protect intellectual function from the effects of Alzheimer's disease.
In adulthood and old age, is use of the nervous system better characterized by the phrase “wear and tear” or by the phrase “use it or lose it” (Swaab 1991)? The research reviewed here, along with many comments on Swaab's paper, mainly support the characterization “use it or lose it.” But enriched experience and use of the cognitive faculites are especially effective early in life and set the basis for later use and maintenance of the brain and of mental ability.
Applications to Recovery from or Compensation for Brain Damage
In all parts of the life span, training and enriched experience help in recovery from or compensation for effects of brain damage. We showed this in experiments with rats in the 1970s (Will et al 1977), and research along this line continues. To what degree does experience actually aid in recovery, and to what degree does it only help to compensate for the effects of brain injury? At a minimum, psychological interventions can improve the quality of life of people with injuries of the brain or of the spinal cord. Beyond this, various combinations of physiological and behavioral interventions may combine to bring improvement.
In attempts to promote recovery from brain damage, some neuroscientists are transplanting fetal brain cells into the region of a brain lesion. Psychologists are taking part in this research. Sometimes such neural transplants or implants help to restore function, but often, for reasons that are not yet fully understood, they do not.
A few years ago, investigators started to study the separate and the combined effects of enriched environment and neural transplants (Kelche et al 1988). Under some conditions, neither the enriched experience nor the transplant alone had a beneficial effect but the combination of the two treatments yielded significant improvement in learning. Further work indicates that formal training of rats may be more effective than enriched environment in promoting the effects of brain cell grafts on recovery of learning ability (Kelche et al 1995). The results of such animal research may someday benefit human patients. At present the attempts to help patients with Parkinson's disease by implanting fetal brain cells are garnering mixed results. Perhaps the differences among clinics in success of cell grafts reflect the kinds and amounts of training and stimulation given their patients; such behavioral factors may well interact with the skill of the neurosurgeon. The combination of brain tissue implantation with cognitive training and stimulation may help researchers to elucidate further the neural bases of learning and memory.
Research on Enriched Environments Is Benefiting Animals in Laboratories, Zoos, and Farms
Animals not only contribute to research on mechanisms of memory and effects of environmental enrichment, but they also benefit from such research, as I have described in somewhat more detail elsewhere (Rosenzweig 1984). Newer standards for housing animals in laboratories reflect findings that animals benefit in development of brain and behavior from adequate space and facilities for species-specific activities like running, investigating, and so forth. Zoos are also providing more natural settings and apparatus that permit animals to engage in species-specific activities. Two of my former students who worked with rats in enriched laboratory environments have since worked to improve settings for zoo animals. Some farms have found that animals thrive better in more natural settings.