Neurogenesis...

One of the great discoveries of the late 20^th century was that the brain was also capable of generating new brain cells: neurogenesis.   

Previously, it was thought that we were born with every last brain cell we would ever have, and that no more could be created. This turns out not to be the case.  Neurogenesis is the creation of new brains cells from pre-cursor cells that occur in the hippocampus, which is so important for memory.    

Although there had been some evidence of this from work done on bird brains and other animals, it was eventually identified in human brains from the tenacious work of a Swedish stem cell neuroscientist Peter Eriksson, from the Sahlgrenska University Hospital, Gothenburg.  The biochemical marker that had been used in animal experiments couldn’t, ethically, be used for human experimentation for this purpose at this time.  However, elsewhere, approved medical studies were being carried out in terminal cancer patients – where new cells are created by the cancer – this same biochemical marker was being used to try and evaluate the effectiveness of treatment, because it would flag up neurogenesis.  Eriksson’s scientific assumption was that if the brain was capable of neurogenesis, these new cells would show evidence of the same biochemical marker that was being used to identify new cancer cells.  So he asked if he could have the brains of these patients, after their death, to examine and see if there was – as he thought there may be – any evidence of neurogenesis.

This work was also being explored by the eminent neuroscientist Professor Fred Gage, at the Salk Institute for Biological Studies, California. After extensive study, and ruling out the possibility that new cells in the brain could be secondary cancer cells, the scientists finally got their ‘Eureka!’ moment in 1998.  The brain was capable of neurogenesis. 

‘All the brains had evidence of new cells exactly in the area where we had found neurogenesis in other species,’ said Gage.  ‘And we could prove through chemical analysis that they were mature neurons.  The neurons were born in the patients when they were in their fifties and seventies, and these neurons stayed alive until the people died.  That was the first evidence for neurogenesis in the adult human brain.  So now we know that in some areas of the brain, new neurons are being made all the time.  It was a surprise because we thought the brain was stagnant.  But in this region of the hippocampus, there are these little baby cells that are dividing, and over time, they mature and migrate into the circuitry and become a full-blown adult neuron with new connections.  And this is occurring throughout life.  The finding brought us an important step closer to the possibility that we have more control over our own brain capacity than we ever thought possible.’

What was also becoming clear from continuing research with mice was that voluntary exercise was as crucial to neurogenesis as environmental enrichment.  So not only did the old adage, ‘use it or lose it’, apply to neurogenesis, physical activity is crucial too.  

‘We think that voluntary exercise increases the number of neural cells that divide and give rise to new neurons in the hippocampus,’ says Gage.  ‘But we think it is environmental enrichment that supports the survival of these cells.  Usually, 50% of the new cells reaching the dentate gyrus of the hippocampus die.  But if the animal lives in an enriched environment, many fewer of the cells die.  Environmental enrichment doesn’t seem to affect cell proliferation and the generation of new neurons, but it can affect the rate and the number of cells that survive and integrate into the circuitry.’

The Whitehall ll study - what to do?

The recently published Whitehall ll study, which focused on 7,000 British civil servants over a 10 year period, showed that amongst this group mental dexterity and brain power deteriorated earlier than was once thought.

There is no doubt that here in the Western world we are, on average, living longer, which creates an associated risk of age-related decline in our mental powers – but the news is not all bad. It was once thought older people lose thousands of brain cells every day, but this has now been contradicted by more recent studies. While neurons in some areas of the brain, like the basal forebrain, do decrease in number as we age, most neurons in the cortex are retained – while the hippocampus is capable of generating new cells until the day we die, if stimulated. Cell process can change, but this fine-tuning may result in gains in wisdom and patience.

While there is a sense of ‘use it, or lose it’ there are some effects of ageing on the brain that we can’t escape, because our bodies are deteriorating too. Our sensory organs – eyes and hearing, in particular – tend to deteriorate, too and with it the inclination to expose ourselves to new stimuli. The decline of other body systems will also have a similar effect. Our digestive system, for example, becomes less efficient at absorbing the nutrients we need from the food we eat, while the endocrine system becomes less efficient at responding to hormonal messages. Brain cells are also extremely sensitive to oxygen levels and, with a degree of arteriosclerosis typical of the ageing process, a reduced blood supply to the brain reduces the oxygen supply. A low-level but continuous oxygen deficiency will lead to a decline in neurons.

Without continuous external stimulation, new brain cell production slows down and with it brain plasticity because, as research has shown, it is the plasticity of the new brain cells that helps old brain cells function better. Neuroplasticity refers to the continued changes that can occur in the brain as the result of exposure to new experiences and learning opportunities, referred to by neurologists as ‘experience-dependent plasticity’. This was seen to occur after injury to the brain, where plasticity allowed new functional and structural changes to take place to compensate for the damaged area. This is what makes rehabilitation so important, and creates the possibility for regaining some, if not all, previously damaged function.

It was previously thought that the adult brain was hard-wired and no longer capable of new development. It had been thought that after critical periods of development, there would be no more change and that the sensory pathways were fixed, even while areas like the hippocampus – concerned with processing memory – continued to produce new neurons. Exposed to enough opportunities, it seems, we go on learning, process what we learn, and apply that learnt experience – all of which encourages the formation of new neurons in the hippocampus.

As we age, we tend to be exposed less to new experiences, become less active, and become less sociable so our opportunities, unless actively sought, for brain stimulation quite naturally decline. We are just less likely to try new things, so overall our opportunities for external stimuli decrease. But when older people are given tests that depend on vocabulary, general information and well-practised activities, they show negligible age-related deterioration. So while both low response times and short-term memory impairment contribute to lower scores on standard tests of intelligence for the elderly, removing this difference equals this out.

The Whitehall study shows that reasoning, memory and verbal fluency were the three main areas of cognitive ability affected. But when I read the following from India Knight’s piece in the Sunday Times on January 8^th 2012, describing what she was trying to do all at the same time, one could perhaps see why: “How can we be expected to remember anything at all, when we are multi-tasking to such an insane degree?” she wrote. “As well as wondering what to write about, I was also thinking about my elder son’s university offers; my younger son being late for school; how to re-hang the door of a kitchen cabinet that has come off its hinges; where to collect my daughter from… what to make for supper… I was also on Twitter, having six conversations at once and reading hundreds more, and the doorbell rang twice…” and so she goes on.

Six things that might help:

· stop multi-tasking, focus on one thing at a time

· eat nutritiously 3 times a day, sit down and relax while eating

· exercise – even a daily, 20 minute walk in natural daylight will help

· anxiety & depression create additional stress hormones that are neurotoxic: so address the worries in your life & learn to let go

· maintain good relationships with people you actually see & talk to

· sleep – good restful sleep is restorative, make it a priority every night

http://www.guardian.co.uk/science/2012/jan/06/memory-loss-begins-at-45-says-study

Take a walk... and boost your brain...

What goes on inside your brain when you exercise? That question has preoccupied a growing number of scientists in recent years, as well as many of us who exercise. In the late 1990s, Dr. Fred Gage and his colleagues at the Laboratory of Genetics at the Salk Institute in San Diego elegantly proved that human and animal brains produce new brain cells (a process called neurogenesis) and that exercise increases neurogenesis. The brains of mice and rats that were allowed to run on wheels pulsed with vigorous, newly born neurons, and those animals then breezed through mazes and other tests of rodent I.Q., showing that neurogenesis improves thinking.

http://well.blogs.nytimes.com/2010/07/07/your-brain-on-exercise/?apage=2

Practice makes perfect..

Well, maybe not perfect, but any of us can reach a level of excellence and expertise through practice. It's opportunity not genetic inclination that creates excellence, that old 10,000 hours again...

Sure, a great footballer has exceptional perceptual awareness and complex spatial skills, but there's a very relevant argument that says this comes primarily from practice, not from genes.

Think about it. Learning to speak is a complicated process, but we all master it. In fact, the process of learning to speak actually creates the neural pathways in the brain that makes us expert at it. The same with learning to read. Or learning to walk. Jump. Hop. Extend this to any complex physical or mental task and it comes back to the same thing... repetition of doing something over and over again, call it practice is you like, makes it possible to do it better.

Takes this a stage further and practice, practice, practice - purposeful practice as the experts term it - and you actually change the anatomy of the brain. For example, taxi drivers learning "the knowledge" so that they can navigate the 659 square miles of the 33 boroughs of London, show a larger than averaged size hippocampus - the area of the brain which houses memory.

And this facility for change is life long. Neurogenesis - the creation of new brain cells and neural pathways, and neuroplasticity - the flexibility of the brain, is life long. We may be less inclined or motivated in some activities than others, but success or failure hinges more on our beliefs than our ability, it seems. The motivation to clock up the hours of practice is born in our brain, not our genes.

Read more about this, and see how you can apply it to the art of concentration, in Matthew Syed's book Bounce: How Champions are Made