What’s a few billion neurons between friends?

March 14, 2012 § Leave a comment

Reading through various articles linked by Anil Seth’s piece in the Guardian that I reviewed yesterday one in particular caught my attention. The article, ‘How many neurons make a human brain? Billions fewer than we thought‘, reports on the research of Dr Suzana Herculano-Houzel that indicates that the healthy human brain contains about 86 billion neurons; this is 14 billion less than widely quoted figure of 100 billion.

Dr Herculano-Houzel’s methodology has attracted attention.  She took the brains of four adult males and reduced them to a “brain soup” then counted the number of cell nuclei belonging to neurons from a sample of the “soup”. From this she was able to estimate that the total number of neurons in the brain. The advantage of this method over taking a count of neurons from a sample of a specific brain region is that it is not affected by the differing density of neurons found in different areas of the brain.

However, it was not the methodology that I was most interested in. What surprised me is that the previous estimate of 100 billion neurons has been widely quoted despite no one seeming to know where the figure came from. It seems strange that science, a field of inquiry that should be rigorous and reliable, should accept a figure that cannot be verified. Which reminds me of a figure often repeated in relation to dieting and weight loss – but that’s for another day.

That aside how important is this research? 14 billion neurons are we are told roughly that of a baboon brain or half that of a gorilla brain. This gives some idea of the large number of neurons that the human brain contains in comparison to other primates. The human brain is typical for a primate except for the number of neurons; it would seem that for brains at least it is size that matters.


Consciousness: Eight questions science must answer (Review)

March 13, 2012 § Leave a comment

Anil Seth, who took part in a debate about the nature of consciousness at the Royal Institution last week, wrote ‘Consciousness: Eight questions science must answer‘. This is the third of the the Guardian’s series ‘Consciousness: The hard problem‘; the other two ‘Neuroscience and philosophy must work together‘ by Barry Smith and ‘Consciousness: why bother?‘ by Chris Frith were reviewed previously. Unlike the other two which are essays this article after a short introduction goes point-by-point through the eight questions.

Although the format does not allow Anil to select one or two main themes and to develop them in greater detail, it does make for a very accessible article and allows the reader to get an overview of some important issues very quickly.

The eight questions are:

  1. What are the critical brain regions for consciousness?
  2. What are the mechanisms of general anaesthesia?
  3. What is the self?
  4. What determines experiences of volition and ‘will’?
  5. What is the function of consciousness? What are experiences for?
  6. How rich is consciousness?
  7. Are other animals conscious?
  8. Are vegetative patients conscious?

Some of these questions, such as ‘what is the self?’ are probably as old as philosophy itself. However, modern science is providing some fresh insights into some of these questions and promises to provide future insights into others. For example one approach to answering the question, ‘what are the critical brain regions for consciousness?’, is to try to identify the neural basis of consciousness. Essentially, this means identifying what brain activity at a neural level correlates to specific experiences of consciousness; these are referred to the Neural Correlates of Consciousness.

The questions cover a broad range of subjects within the field of consciousness; most people with an interest in consciousness should find something of interest in this article. I thought the question ‘What is the function of consciousness’ particularly interesting. The best answer appears to be that consciousness integrates information. Conversely it might be expected that a lack of consciousness could reflect a breakdown in how the brain integrates information. Anil points to increasing evidence to suggest that disintegration of how different parts of the brain work together that underlies how anaesthesia works.

Anil has backed up each of the eight points with at least one link which enables the reader to look deeper into the subject. It also allows the reader to get a better understanding of the evidence on which Anil bases his writing.

Of the three articles I found this one to be the most interesting and useful, and Anil has highlighted several strands of research in the neuroscience of consciousness highlighted here that are worth following the progress of.

The Truth About Exercise – Synopsis (part 2)

March 9, 2012 § Leave a comment

“Exercise, I know I should do it …… but I hate it”

Like Michael Mosley 80% of us do not take regular exercise. Earlier in ‘The Truth About Exercise‘ Mosley established that taking a 90 minute walk reduced the amount of fat in blood following a fat-laden breakfast the next day by about a third. But as Mosley’s quote above makes clear, the problem isn’t that we are not aware that exercise is good for us, the problem is that for many of us keeping up regular exercise is too difficult.

It might have occurred to you that if there was an exercise regimen less onerous than the recommended 150 minutes of moderately intensive aerobic activity the chances that more people would comply with it must be greatly enhanced. If so you would be glad to know that research by Prof. Jamie Timmons among others is beginning to indicate that such a regimen is indeed possible. Prof. Timmons told Mosley about the benefits of the HIT (High Intensity Training) protocol. Under this regimen an exercise session consists of three sets of 20 seconds of very intensive activity interspersed with periods of rest. Mosley agreed to follow HIT 3 times a week for a month after which his progress would be assessed.

So Mosley is filmed taking away an exercise bike in readiness for his 12 minutes of exercise over the following 4 weeks. During this period Mosley took the opportunity to investigated another regimen and to introduce us to another acronym – NEAT (Non-Exercise Activity Thermogenesis)’; this is, as a rather excited Dr. James Levine tells us everything we do that is not exercise. The sedentary lifestyle is very bad for us (“the chair is a killer” says Dr. Levine). Standing up only raises the metabolism by about a third; better is walking which can double or treble the metabolic rate. Michael Mosley and two volunteers he enlisted wore special pants, ‘fidget pants’, for a day; these pants, monitor and record the subjects activity. The measurements showed that Mosley was mostly sedentary throughout the day. So he wore the fidget pant for another day, this time being more active without exercising (by walking where possible, standing instead of sitting, taking the stairs instead of the lift etc). This attempt to raise his NEAT proved very successful and Dr. Levine revealed that Mosley had used an extra 500 calories in a single day. By increasing our NEAT we can, without exercise or radically changing our lifestyle, significantly increase our calorie expenditure.

Having completed his 12 minutes of exercise Mosley returned to Prof. Timmons to find out how much benefit, if any, he had derived from the HIT protocol. First, he was told about the insulin sensitivity results which had increased by 23% (consistent with experimental findings). There is evidence to suggest that improving insulin responsiveness is associated with improving fat metabolism and weight loss. This is thought to be as a result of glycogen reserves being broken down. Mosley was very impressed and pleased with these results – his father suffered from diabetes and he is keen to not suffer the same fate.

Mosley was less please to discover that his exercise had made absolutely no difference to his aerobic fitness. He is among the 20% of the population are non-responders i.e. their aerobic fitness does not improve with exercise. On the other hand 15% of people are super-responders and their aerobic fitness in response to exercise far exceeds that of most other people. Eleven genes appear to be responsible for individuals aerobic responsiveness and how well different people will respond can be predicted from gene tests. Prof. Timmons revealed that Mosley’s test had predicted that he would be a non-responder. In future science may be able to guide people towards finding the most effective exercise for them as individuals.

Despite the disappointment of being told he was a non-responder Mosley vowed to continue following HIT for the improvements in insulin sensitivity, and NEAT for the benefits of increasing calorie expenditure.

I found ‘The Truth About Exercise’ to be both interesting and informative. The presenter Michael Mosley is personable and a good communicator. Yet a review of the considerable response from reviewers and the public alike shows that there is a great deal of misunderstanding and/or mistrust of the messages in this documentary. I found the response to be very revealing with regards to how information about health and the scientific investigation into exercise is ‘consumed’ by the public. It is for this reason I shall be revisiting this subject again.

Consciousness: why bother? (Review)

March 8, 2012 § Leave a comment

The second article in the Guardian’s series about consciousness comes from Professor Chris Frith, professor emeritus at the Wellcome Trust Centre for Neuroimaging at University College London.

Professor Frith cites some useful examples of phenomenon that clarify the relationship between mind and brain. For example, he tells us about how damage to visual areas of the brain resulting in “visual agnosia” can lead to the paradoxical situation of people who are unable to recognise an object from its shape but can nonetheless adjust their hands to grasp the object when picking it up.

Much of the article, while interesting, did not offer a great deal of insight into recent developments in our understanding of the brain. Indeed, many of the examples were strongly reminiscent of Oliver Sacks’ book ‘The Man Who Mistook His Wife for a Hat‘ that was first published in 1985.

Perhaps I was expecting too much from a professor in a neuroimaging centre, however I would have liked Professor Firth to have focused more on experiments such as those into “change blindness”. These are experiments in which the subject is unable to detect a change in stimuli, for example two similar pictures that are rapidly presented to the subject. Yet the brain scanner is able to detect distinct brain activity that indicates the change has been detected even if the subject is not aware of it.

Also interesting was Professor Firth’s own area of research into the value of sharing conscious experiences. Professor Firth’s research group found that as a result of this sharing it was possible on the experimental task for two individuals to reach more accurate results than either individual on their own.

Although not the article I was hoping for it is nonetheless very interesting and informative. It also ends with a helpful list of links for further reading.

Neuroscience and philosophy must work together (Review)

March 6, 2012 § Leave a comment

Tomorrow the Royal Institution holds a debate on the nature of consciousness entitled ‘Consciousness: The hard problem‘.  Dr Anil Seth, Professor Chris Frith and Professor Barry Smith will take part in the debate. They have also contributed thought provoking articles for the Guardian in the run up to the event.

The latest of these articles comes from Professor Barry Smith, director of the Institute of Philosophy at the School of Advanced Study, University of London. The article ‘Neuroscience and philosophy must work together‘ is a readable overview of what could be a dry and difficult area. However, I found that while he does indicate how philosophy can benefit from new evidence arising from neuroscience, the article failed to explain why he believes neuroscience and philosophy must work together. Any philosophy of consciousness must take account of  new information about what is going on in the brain which neuroscience is providing.

“Now we are also learning more and more from neuroscience and neurobiology about how much of what we do is the result of unconscious processes and mechanisms.”

Professor Smith doesn’t explain what neuroscience has to gain from philosophy or how the two working together would be beneficial. Perhaps part of the answer is that philosophy has something to offer where science comes up short.

“… it must be the brain that gives rise to consciousness and decision-making. So how does consciousness arise in the brain? Science still has no answer.”

Maybe, but this would be to relegate philosophy to the role of to a sort of stand-in science, there as a place-holder until the real science is ready to step in.

This I would object to not least because there is one branch of moral philosophy that I believe should always have a role in any field of science – ethics. As we learn more about what make us who we are, and about the neuroscience that underpins our identity, the more important it is that a firm grasp of the ethical issues involved in investigating and using this information becomes.

More fundamentally I believe it is a mistake to view philosophy and science as two completely separate (and as seems apparent from some responses to the article – incompatible) phenomenon. Both philosophy and science are ways of knowing, in this case knowing about consciousness. Neurobiology can investigate consciousness at a biological level, whereas philosophy seeks to understand knowledge and the nature of knowledge.

Philosophy therefore has a role to play in two ways. First, philosophy of science is necessary to make sense of scientific findings. While the philosophy of science may not be made explicit it is always there, for example when scientists use inductive reasoning formulate theories  or derive conclusions  from their experiments using deductive reasoning.

Second, because philosophy operates at a higher level than the hard sciences it is able to provide a context in which findings from different fields of science can be understood. Not that I am suggesting that every multi-disciplinary team requires a philosopher to act as interpreter between scientist operating in different specialisms but rather that they are probably applying philosophy on some level even if they are not, dare I say, conscious of it. For example, doctors with observations about the behaviour of patients with different brain injuries talking with scientists who carry out brain-imaging on subjects undergoing different activities, can each benefit from the knowledge of the other. This benefit will be operating at a level of abstraction higher than discussions of lesions to specific brain regions or the actions of specific neurotransmitters.

Moreover, it is unnecessary to operate some sort of league table for the usefulness of different fields of inquiry. Philosophy has a role in investigating and explaining consciousness I am sure, however, I feel Professor Smith’s article is a missed opportunity for making this role clear. Hopefully, once the debate has taken place follow-up articles will explain more clearly how and why neuroscience and philosophy must work together.

The Truth About Exercise – Synopsis (part 1)

March 5, 2012 § Leave a comment

The main benefits of exercise is not the amount of calories that you expend directly undertaking exercise – Michael Mosley was told that to work off the calories he gain consuming a modest snack of a cappuccino, muffin and banana would require him to run for 55 minutes.

However, as Mosley discovered, there are other benefits. He is, he revealed, a TOFI (Thin Outside, Fat Inside); this means that despite appearing to be fairly lean he has a lot of internal fat around his organs (visceral fat). Visceral fat is more dangerous than subcutaneous fat (fat which resides primarily under the skin). Fat levels in Mosley’s blood were measured before and after a cooked breakfast. He then went for a 90 minute walk. The next day he had the same cooked breakfast and again fat levels were measured. This time the level of fat was found to be 30% less than the day before. Exercise has a marked impact on the way our bodies metabolise fat.

However, realistically many of us are unlikely to  undertake this level of activity regularly enough to benefit. So Mosley then investigated a less imposing exercise regimen. The protocol requires as little as 3 minutes 3 times a week on an exercise bike. In fact the amount of physical exertion is shorter than this – just three bursts of 20 seconds in each session, or 3 minutes in total over the week. This is called HIT (High Intensity Training, although many people maintain that the proper acronym is HiiT or High Intensity Interval Training). The idea is that what is really important is the intensity of the activity not the length of the activity.

After following this regimen for four weeks Mosley was tested for insulin responsiveness and for aerobic fitness. These results will be discussed in more detail in part 2.

The Truth About Exercise

March 4, 2012 § Leave a comment

Michael Mosely exercisingThe most interesting programme of the week was Horzon’s “The Truth About Exercise”. As is the case with TV documentaries these days the presenter, Michael Mosley, put himself through the trials and tribulations required to provide the programme with empirical evidence, and the viewer with voyeuristic entertainment.

As one of the more informative documentaries I have seen recently I shall devote a greater than usual level of attention to this programme starting with “The Truth About Exercise – Synopsis (part 1)“.

Of particular interest is the  HIT (High Intensity Training) and NEAT (Non-Exercise Activity Thermogenesis); both of these are explained in more detail in “The Truth About Exercise – Synopsis (part 2)“.