HIGHLY STIMULATED EINSTEINIAN RATS WITH BIG BRAINS

THIS WAS PRETTY STARTLING IN ITSELF, BUT NOTHING

COM-pared to what the researchers stumbled onto next. The way AChE was measured was as enzymatic activity per unit of tissue weight. "Fortunately," recalls Rosenzweig, "we had to record the weights of our brain samples in order to measure chemical activity per unit of tissue weight. After about two years of contemplating the chemical effects, it finally dawned on us that the weights of the brain samples also changed."²⁶⁷ What they discovered was so astonishing that even the re-searchers, after checking and rechecking their figures found it almost incredible: the cortex of the enriched-environment rats was much heavier than the cortex of the other rats! Somehow, stimulating experiences had caused the rats' brains to grow.

28

GETTING SMART: BRAIN EXPANSION THROUGH STIMULATION

"The changes in brain weights were even more astonishing at that time than were the neurochemical changes," says Ro-senzweig, "because it had become a dogma by the start of the present century that brain weight remains stable in the faces of challenges that affect many other bodily measures." So aston-ishing, in fact, that many scientists claimed the results were impossible. According to Rosenzweig, "skepticism or frank disbelief were the initial reactions to our reports that signifi-cant changes in the brain were caused by relatively simple and benign exposure of animals to differential environmental ex-perience."²⁸¹

The revolutionary findings and the doubts of their peers triggered a new series of studies by the Berkeley group. With the collaboration of neuroanatomist Marian Diamond, they set about to find out what was happening anatomically to make the cortex of the enriched rats heavier. These studies resulted in a succession of discoveries which were even more amazing.

In all cases, the rats raised in the enriched environment showed:

- increased thickness of the cerebral cortex or "gray mat-ter,"

- a 15 percent increase in the actual size of individual neurons in the cortex,

- increases in protein in the brain paralleling the increases in cortical weight,'proving that the growth effect was on tissue and not just on fluid content of the brain,

- an increase in the amount of dendritic branching (den-drites are the hairy branching fibers which project in large numbers from the body of each neuron, and which receive inputs from other neurons and conduct them to the cell body;

thus, an increase in branching means a greater number of po-tential inputs, and a greater amount of popo-tential information available to each neuron),

- an increased number of dendritic spines per unit length of dendrite (spines are the small projections that cover the surface of dendrites by the thousands, each one marking the site of a synapse, the point where another neuron makes a junction with this neuron; thus increased numbers of spines

29

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stimuli, and a variety of challengers. This was called an enriched environment.

After certain periods ranging from days to a number of months, the brains of the rats were removed and analyzed.

The researchers discovered that rats raised in the enriched en-vironment showed higher levels of AChE activity in then-brain cortex than did rats raised in the standard and impover-ished environments. (The cerebral cortex is a layer of nerve cells forming a convoluted outer shell over the brain, the

"thinking cap" or "gray matter" atop the brain, in which much of the thinking or higher intellectual activity of the brain takes place.) Says Rosenzweig, "Rather than cortical AChE activity being a fixed individual characteristic, as we had supposed, it could apparently be altered by experience!"²⁸¹

Since AChE activity was related to learning ability, that is, the ability to process information, this meant that the rats in the enriched environment had more learning ability - were

"smarter" - than the other rats, despite the fact that they had all started out as equals. Somehow, experiences had altered intelligence.

HIGHLY STIMULATED EINSTEINIAN RATS WITH BIG BRAINS

THIS WAS PRETTY STARTLING IN ITSELF, BUT NOTHING

COM-pared to what the researchers stumbled onto next. The way AChE was measured was as enzymatic activity per unit of tissue weight. "Fortunately," recalls Rosenzweig, "we had to record the weights of our brain samples in order to measure chemical activity per unit of tissue weight. After about two years of contemplating the chemical effects, it finally dawned on us that the weights of the brain samples also changed."²⁶⁷ What they discovered was so astonishing that even the re-searchers, after checking and rechecking their figures found it almost incredible: the cortex of the enriched-environment rats was much heavier than the cortex of the other rats! Somehow, stimulating experiences had caused the rats' brains to grow.

28

GETTING SMART: BRAIN EXPANSION THROUGH STIMULATION

"The changes in brain weights were even more astonishing at that time than were the neurochemical changes," says Ro-senzweig, "because it had become a dogma by the start of the present century that brain weight remains stable in the faces of challenges that affect many other bodily measures." So aston-ishing, in fact, that many scientists claimed the results were impossible. According to Rosenzweig, "skepticism or frank disbelief were the initial reactions to our reports that signifi-cant changes in the brain were caused by relatively simple and benign exposure of animals to differential environmental ex-perience."²⁸¹

The revolutionary findings and the doubts of their peers triggered a new series of studies by the Berkeley group. With the collaboration of neuroanatomist Marian Diamond, they set about to find out what was happening anatomically to make the cortex of the enriched rats heavier. These studies resulted in a succession of discoveries which were even more amazing.

In all cases, the rats raised in the enriched environment showed:

- increased thickness of the cerebral cortex or "gray mat-ter,"

- a 15 percent increase in the actual size of individual neurons in the cortex,

- increases in protein in the brain paralleling the increases in cortical weight,'proving that the growth effect was on tissue and not just on fluid content of the brain,

- an increase in the amount of dendritic branching (den-drites are the hairy branching fibers which project in large numbers from the body of each neuron, and which receive inputs from other neurons and conduct them to the cell body;

thus, an increase in branching means a greater number of po-tential inputs, and a greater amount of popo-tential information available to each neuron),

- an increased number of dendritic spines per unit length of dendrite (spines are the small projections that cover the surface of dendrites by the thousands, each one marking the site of a synapse, the point where another neuron makes a junction with this neuron; thus increased numbers of spines

29

MEGABRA1N

indicates a potential for a greater richness of interconnection between neurons),

- increases in the number of synapses and in the size of synaptic contact areas (synapses are the spots where different neurons are connected and by means of which communication among neurons takes place; thus, the increase in their number and size means increased richness of communications in the cortex),

- an increase in the ratio between the weight of the cortex and the weight of the rest of the brain (thus the enriched envi-ronment does not simply stimulate and trigger generalized growth throughout the entire brain, but is specifically benefi-cial to that area of the brain devoted to thinking, learning, and memory),

- a 15 percent increase in the number of glial cells, the

"glue" cells that are the most numerous cells in the brain, and which hold together, support, and nourish the brain neurons, act as guides for neural growth, assist in learning, and seem to form some mysterious communicating network of their

O w n *88, 281

*Many have recently come to suspect that one key to intellectual ability is the ratio between glia and neurons in the cortex, a ratio which is about ten to one in humans.

The human brain is about five times as large as that of a chimpanzee, yet contains only about 30 to 50 percent more neurons - the intellectual abyss dividing man from chimps seems to come from the larger numbers of glial cells in the human brain. As a result of newly developed research technology, scientists have been able to detect a variety of hitherto unsuspected activities in the glial cells. Research by neurophysio-logist Gary Lynch of UC at Irvine has shown that "in the period before there is any J axon sprouting, before any axon growth, the glial cells go crazy in terms of activity.

The glial cells divide and they move through the intact tissue of the brain. They migrate through big sections of the brain to get to the active site. And the ones that are already there undergo incredible reactions. They send out branches that become very large. All this is going on before there is any axonal growth. None of these J findings have been incorporated in textbooks y e t . . . . It's a strange, bizarre system,"

he says. "You know, the thought of these things crawling through your head, it gives you a different vision of the brain."⁶⁵ There is also evidence that the glia are electri-cally sensitive, and some believe they may act much like semiconductors, picking up faint electrical charges from the nervous system or surrounding electrical fields and amplifying them just as transistors amplify electrical signals. A recent study by Brian MacVicar of the University of Calgary in Alberta shows that under certain i conditions the glial cells become electrically excitable and behave like neurons. He has detected the occurrence in glial cells of action potentials, the self-propagating

3 0

GETTING SMART: BRAIN EXPANSION THROUGH STIMULATION

As Diamond continued her autopsies with rats exposed to enriched environments for various periods, she made the fur-ther discovery that brain changes could take place with star-tling speed - she soon learned they could bring about changes in the chemistry and structure of the cortex in only four days.

Studies later lowered that estimate to forty-five minutes, and now have proved that significant structural changes in re-sponse to stimulation take place almost instantaneously.¹⁰¹-¹⁰² Study has followed study, with results that have been replaced or advanced by work in other laboratories, not only with rats, but with gerbils, squirrels, and monkeys. These studies, while trying different approaches and examining different variables, have consistently supported one conclusion: in some way an enriched environment, that is, increased brain stimulation, not only produces a growth in size and weight of the cortex, but completely alters and enriches the quality of the entire cerebral cortex.

electrical changes characteristic of nerve, muscle, and endocrine cells. "A new function may be added to the postulated actions of glial cells," says MacVicar. "It may be possible for glial cells to cause widespread excitation of neurons."² Thus, a system which is as yet little understood. However, it's clear that the increase in number of glial cells resulting from mental stimulation, which means an increase in number of glial cells nourishing and supporting each neuron, somehow assists in higher mental functioning. In fact, as this is written, word arrives from Marian Diamond that a high ratio of glial cells to neurons may play a part in the intellectual superiority of certain geniuses, like Albert Einstein. Diamond obtained samples of Einstein's brain from the pathologist who performed the autopsy on Einstein in 1955 and examined sections of the neocortex to determine the ratio of glial cells to neurons. Since her work shows that animals in environments that stimulate mental activity have more glial cells per neuron, says Diamond, "we hypothesized that if Einstein's brain was more active in some areas, we would find more glial cells there." She found that indeed Einstein's brain contained more glial cells per neuron in all four of the brain areas studied, compared with samples from the brains of eleven normal males ranging in age from forty-seven to eighty. "We don't know if Einstein was born with this or developed it later," Diamond points out, "but it tells us that in one of the highest evolved areas of the brain, there is evidence that he had greater intellectual processing."²²⁵

31

MEGABRA1N

indicates a potential for a greater richness of interconnection between neurons),

- increases in the number of synapses and in the size of synaptic contact areas (synapses are the spots where different neurons are connected and by means of which communication among neurons takes place; thus, the increase in their number and size means increased richness of communications in the cortex),

- an increase in the ratio between the weight of the cortex and the weight of the rest of the brain (thus the enriched envi-ronment does not simply stimulate and trigger generalized growth throughout the entire brain, but is specifically benefi-cial to that area of the brain devoted to thinking, learning, and memory),

- a 15 percent increase in the number of glial cells, the

"glue" cells that are the most numerous cells in the brain, and which hold together, support, and nourish the brain neurons, act as guides for neural growth, assist in learning, and seem to form some mysterious communicating network of their

O w n *88, 281

*Many have recently come to suspect that one key to intellectual ability is the ratio between glia and neurons in the cortex, a ratio which is about ten to one in humans.

The human brain is about five times as large as that of a chimpanzee, yet contains only about 30 to 50 percent more neurons - the intellectual abyss dividing man from chimps seems to come from the larger numbers of glial cells in the human brain. As a result of newly developed research technology, scientists have been able to detect a variety of hitherto unsuspected activities in the glial cells. Research by neurophysio-logist Gary Lynch of UC at Irvine has shown that "in the period before there is any J axon sprouting, before any axon growth, the glial cells go crazy in terms of activity.

The glial cells divide and they move through the intact tissue of the brain. They migrate through big sections of the brain to get to the active site. And the ones that are already there undergo incredible reactions. They send out branches that become very large. All this is going on before there is any axonal growth. None of these J findings have been incorporated in textbooks y e t . . . . It's a strange, bizarre system,"

he says. "You know, the thought of these things crawling through your head, it gives you a different vision of the brain."⁶⁵ There is also evidence that the glia are electri-cally sensitive, and some believe they may act much like semiconductors, picking up faint electrical charges from the nervous system or surrounding electrical fields and amplifying them just as transistors amplify electrical signals. A recent study by Brian MacVicar of the University of Calgary in Alberta shows that under certain i conditions the glial cells become electrically excitable and behave like neurons. He has detected the occurrence in glial cells of action potentials, the self-propagating

3 0

GETTING SMART: BRAIN EXPANSION THROUGH STIMULATION

As Diamond continued her autopsies with rats exposed to enriched environments for various periods, she made the fur-ther discovery that brain changes could take place with star-tling speed - she soon learned they could bring about changes in the chemistry and structure of the cortex in only four days.

Studies later lowered that estimate to forty-five minutes, and now have proved that significant structural changes in re-sponse to stimulation take place almost instantaneously.¹⁰¹-¹⁰² Study has followed study, with results that have been replaced or advanced by work in other laboratories, not only with rats, but with gerbils, squirrels, and monkeys. These studies, while trying different approaches and examining different variables, have consistently supported one conclusion: in some way an enriched environment, that is, increased brain stimulation, not only produces a growth in size and weight of the cortex, but completely alters and enriches the quality of the entire cerebral cortex.

electrical changes characteristic of nerve, muscle, and endocrine cells. "A new function may be added to the postulated actions of glial cells," says MacVicar. "It may be possible for glial cells to cause widespread excitation of neurons."² Thus, a system which is as yet little understood. However, it's clear that the increase in number of glial cells resulting from mental stimulation, which means an increase in number of glial cells nourishing and supporting each neuron, somehow assists in higher mental functioning. In fact, as this is written, word arrives from Marian Diamond that a high ratio of glial cells to neurons may play a part in the intellectual superiority of certain geniuses, like Albert Einstein. Diamond obtained samples of Einstein's brain from the pathologist who performed the autopsy on Einstein in 1955 and examined sections of the neocortex to determine the ratio of glial cells to neurons. Since her work shows that animals in environments that stimulate mental activity have more glial cells per neuron, says Diamond, "we hypothesized that if Einstein's brain was more active in some areas, we would find more glial cells there." She found that indeed Einstein's brain contained more glial cells per neuron in all four of the brain areas studied, compared with samples from the brains of eleven normal males ranging in age from forty-seven to eighty. "We don't know if Einstein was born with this or developed it later," Diamond points out, "but it tells us that in one of the highest evolved areas of the brain, there is evidence that he had greater intellectual processing."²²⁵

31

MEGABRA1N