Category: Inside the Brain

The ever-excellent Developing Intelligence has just posted about research that suggests that certain types of brain pathology may selectively improve mental performance.

The first article reports on research that suggests that children with a history of febrile seizures (seizures or ‘fits’ caused by fever) tend to do better in school than their peers.

This is initially surprising, as seizures are traditionally associated with mental impairment if they occur frequently. As the Developing Intelligence article mentions, it is worth waiting until further evidence is gathered to be sure that this is a reliable finding, as the study uses some non-standard tests.

It does suggest the idea, however, that the brain maintains a “delicate balancing act” and that some things that may confer an advantage may also confer a risk of brain disturbances.

The second article reports that deaf people have enhanced motion sensitivity in that they can detect motion over a wider area than control participants.

Motion sensitivity is known to involve the magnocellular parts of the visual pathway. Motion sensitivity and magnocellular brain function are also known to be particularly sensitive to impairment in certain developmental conditions (such as dyslexia and autism).

The authors of the study thought that this area might, therefore, be most likely to show better performance where sensory problems (i.e. deafness) meant that vision was used to a much greater degree.

They found exactly this pattern of performance, and note that this is likely further evidence for the brain’s ‘plasticity’ – where the brain reorganises through experience.

Link to article ‘Working Memory and Convulsions’.
Link to article ‘Perceptual Enhancement Among the Deaf’.

The debate about male-female differences has always been controversial owing to the link with social and political issues. Where science has previously feared to tread, researchers are now beginning to untangle the differences and similarities.

The Economist has an in-depth article where they summarise and discuss many of the most reliable male-female differences in psychology and dispel some of the myths about men and women being fundamentally different in the way they think.

The article also tackles differences in the structures of male and female brains, noting that male brains are, on average, 9% bigger than female brains, but that female brains tend to be more densely packed with grey matter – the cell bodies and dendrites of neurons where most of the cognitive ‘work’ is supposedly done.

The San Francisco Chronicle continues in this vein by discussing the work of Dr Louann Brizendine a neuropsychiatrist who has been researching male-female brain differences and has recently published a book on her findings.

She’s obviously trying to do a bit of PR for the book (“…talking activates the pleasure centers in a girl’s brain. We’re not talking about a small amount of pleasure. This is huge. It’s a major dopamine and oxytocin rush, which is the biggest, fattest neurological reward you can get outside of an orgasm”) but otherwise discusses some of the latest and most interesting developments in the field.

One of her particular interests is the role of hormones in brain function, both during the development of the fetus, and during childhood and adult life. This is becoming an increasing focus in neuroscience research.

A good place to start if you want a grounding in the scientific literature, is a recent article by Larry Cahill in Nature Reviews Neuroscience entitled ‘Why sex matters for neuroscience’.

Link to Economist article ‘The mismeasure of woman’.
Link to SF Chronicle article ‘Femme Mentale’.
Link to ‘Why sex matters for neuroscience’.

Could a wide-spread brain infection account for differences in cultures across the world? Possibly, is the surprising answer from a new research paper published in the Proceedings of the Royal Society of London.

If cognitive parasitology isn’t your thing (and it may not be, as I just made that up) the research is expertly discussed by Carl Zimmer.

The disease caused by the parasite Toxoplasma gondii is called toxoplasmosis and has been linked to ‘personality’ changes in rats and mice.

Although controversial, some suggest that this infection may also be linked to personality changes in humans, suggesting that different rates of infections in different countries may lead to differences in ‘national character’.

You’re best going to Zimmer’s write-up for a concise take on the major implications, but I’ll leave you with an intriguing point he finishes on:

“[This] raises another interesting question: what about other parasites? Do viruses, intestinal worms, and other pathogens that can linger in the body for decades have their own influence on human personality?”

Link to Zimmer’s article ‘A Nation of Neurotics? Blame the Puppet Masters?’.

OR-Live is a website that carries videos of surgical procedures, including a section where you can watch neurosurgery in action.

A brain clipping and coiling procedure to repair an aneurysm will be broadcast live today, and if that doesn’t take your fancy, there’s plenty more in the archive.

One of my favorites is a temporal lobectomy (removal of part of the temporal lobe) that was completed to remove the source of untreatable epileptic seizures.

It has a winning combination of a fascinating surgical procedure and a slightly uncomfortable professor of neurosurgery looking a bit awkward in front of the camera.

The site is a little confusing in that you need to use the ‘Watch Live Webcast’ link to launch an archive recording as well as see a live broadcast.

Link to neurosurgery at OR-Live (via Neurocontrarian).

There’s a thought-provoking piece in the latest issue of open-access medical journal PLoS Medicine on whether antidepressants ‘correct’ a problem in the brain, or just create an altered state that may be useful for people with low-mood problems.

It is notable that the way psychiatric drugs are described is usually because of marketing. For example, SSRIs are classed as ‘antidepressants’, dopamine agonists and ‘antipsychotics’ and drugs like sodium valproate as ‘mood stabilizers’.

These terms have been promoted by drug companies in an effort to establish a market for particular compounds and imply that they directly affected these conditions. Often, they have been invented to replace previous labels which were no longer useful in marketing the drug.

The authors of the PLoS Medicine paper argue that trials have shown that, for example, opiates and amphetamine-like drugs can have beneficial effects in depressed patients but are not considered ‘antidepressants’.

The paper also tackles the idea that depression is ’caused by low serotonin’ in the brain and that antidepressants ‘correct’ this problem.

The low serotonin theory of depression must rank as one of the most widely known and least supported scientific theories, as there is comparatively little evidence that backs this explanation.

The authors argue that instead of trying to explain the action of a drug in terms of a disease it is meant to ‘correct’, it is more accurate to describe the drug in terms of its general actions in the brain which could be coincidentally useful in treating certain conditions.

I suspect, this is what inevitably happens anyway, owing to the needs of marketing.

Typically, when a drug is discovered, it is targeted at a condition which is likely to be profitable (depression being the classic example). At this point, it is usually marketed as an anti-something-or-other.

Later, when the profits begin to come in, the pharmaceutical company looks to widen the market and tests it on other, less prevalent, but hopefully still profitable conditions (e.g. social phobia).

For example, SSRI drugs (such as Prozac) are now indicated for depression, PTSD, obsessive-compulsive disorder, eating disorders and panic disorder to name but a few.

The marketing then begins to place less emphasis on its original label, so it is seen as more wide acting.

Have a look at the archives of the front page of the Seroquel website before and after it gained approval for the treatment of bipolar disorder and notice how the term ‘antipsychotic’ is suddenly not so prominent.

Perhaps to put the paper in context, psychiatrist Dr Joanna Moncrieff, one of the authors of the PLoS Medicine paper, is co-chair of the Critical Psychiatry Network – a group of psychiatrists who dispute the predominance of biological models of mental disorder and campaign for a less coercive psychiatry.

Link to PLoS Medicine article ‘Do Antidepressants Cure or Create Abnormal Brain States?’

There have been some critical commentaries recently that suggest that the hype over mirror neurons has become unbearable and a backlash is about to begin.

Mirror neurons are cells in the brain that are active both when a person is performing an action, or when they see someone else perform an action, and have been hypothesised to be involved in perceiving and comprehending others’ actions.

Worryingly, this system has been proposed as the basis of everything from empathy to appreciation of art, with very little supporting evidence.

Both Mixing Memory and Neurotopia have sceptical commentaries on mirror neurons and doubt whether they have been consistently demonstrated in humans in anything other than correlational brain scanning experiments.

This is probably a little unfair, as evidence for ‘mirror neurons’ in humans has been found using subdural (brain surface) electrodes, transcranial magnetic stimulation, fMRI, magnetoencephalography, EEG and when studying patients with action production and recognition problems after brain injury.

That’s quite a lot of converging evidence for the existence of an equivalent human system.

What is a little misleading is that the original studies measured the responses of single neurons in monkeys, whereby the human studies have all been using techniques that measured activation from a group of neurons.

This, and the fact that the recognition and generation of actions also relies on other brain areas, has led some to use the more accurate term ‘mirror system’ in preference to ‘mirror neuron’.

What most of the recent articles seem to be criticising, however, is that the concept is being used as a convenient ‘just so’ story for explaining almost any sort of complex human behaviour, usually by people with a fairly poor grasp of the existing evidence.

It’s easy to see why the idea is attractive. A system that is both involved in producing our own movements and becomes active when we see others moving leads some to infer (perhaps falsely) that we encode others’ behaviour into our brains in quite a direct way.

Even worse, in some retellings of the story, behaviour can include almost anything you care to think of.

As noted by Frontal Cortex, this concept, although flawed, is easy to grasp and user-friendly, making almost anyone an instant ‘expert’ on how the brain supports human interaction.

The reality will probably turn out to have too many qualifications to allow the media obsession with mirror neurons to continue forever, but in the mean time, don’t get put off by the hype.

The findings are fascinating and the mirror system will surely play an important role in our future understanding of human neuropsychology, even if this won’t exactly match how the media portrays it the moment.

Link to Mixing Memory article.
Link to Neurotopia article.

This week’s ABC Radio All in the Mind had an edition on auditory hallucinations that discusses the experience of ‘hearing voices’ as well as the neuroscience that might explain them.

Hallucinatory voices are still largely mysterious to science. Originally they were linked to psychotic mental illness and particularly schizophrenia, but it later became known that only about 30% of people who hear voices ever become psychiatric patients.

Furthermore, for some people who hear voices, they can seem to exist as separate conscious entities with their own personalities. Someone may experience a number of voices each with a distinct age, sex and accent.

Research has suggested some explanations for why voices occur (it is know that the auditory cortex is activated with hallucinated voices are heard, suggesting that they may be internal thoughts experienced as sound) but many of these other issues are still unresolved.

The programme discusses the current state of research, as well as talking to two voice hearers about the experience itself, including campaigner Ron Coleman who has been particularly active within the Hearing Voices Network.

The network has taken an alternative view to the medical model, which assumes that voices are a symptom of mental disturbance, and encourages hearers to understand their voices in whatever way best promotes successful living.

Link to ABC Radio All in the Mind on hearing voices.
Link to Wikipedia article on hearing voices movement.

There’s a thought-provoking piece over at Brain Ethics about the role of genetics in violence, and particularly the role of a gene that codes for a type of monoamine oxidase enzyme involved in the breakdown of certain neurotransmitters in the brain.

The post reports on recent research led by neuroscientist Andreas Meyer-Lindenberg that found that variants of the MAOA gene predicted amygdala size, and both the response of the amygdala and cingulate cortex.

Both the amygdala and the cingulate cortex have been strongly linked to emotion recognition, and the cingulate cortex to empathy and anticipation.

It may be that differences in these structures may make someone more likely to react violently in certain situations.

The full story is a little more nuanced that this, however, and you’re best visiting Brain Ethics for more comprehensive coverage and analysis.

Link to article ‘MAOA and the risk for impulsivity and violence’.

An article in last month’s American Scientist offered an interesting theory of why some people are driven to find knowledge – because of the kick of natural opioids in the brain.

Sadly, the article is not freely available online, but the theory is outlined by neuroscientist Professor Irving Biederman in a pdf file he’s put online, and in a summary from Eureka Alert.

The idea is that the moment of finally understanding something causes a release of natural endorphins in the brain, providing a response to knowledge acquisition that conditions us to want more.

In other words, intellectual curiosity may be driven by an addiction to an opioid high.

Biederman’s theory was inspired by the well-known discovery that opioid receptors increase along the ventral visual pathway in the brain – the one that is most strongly associated with recognition and meaning.

At the moment, the theory is still largely speculative, although remains an interesting take on why humans are naturally curious.

Link to summary from Eureka Alert.
pdf of talk by Biederman outlining his theory.
Link to summary of Biederman’s American Scientist article.

There’s a funny and insightful article in Time Magazine by writer Michael Kinsley on the difficulty of selecting the right words to mark the point when you become conscious after brain surgery.

Kinsley wrote the piece before having surgery to implant a deep brain stimulation device to help alleviate the symptoms of Parkinson’s disease.

To much comic effect, the article discusses his dilemma over choosing something to say to make sure he seems cooly blasé, while not sounding like the surgery has affected his faculties.

Apparently, his surgery went fine but you’ll have to read the end of the article to find out what his first words upon awakening actually were.

Link to Time article ‘Yes, It Really Is Brain Surgery’.

Neurology has an interesting report on the use of low doses of the hallucinogenic drugs LSD and psilocybin to treat cluster headaches.

Cluster headaches are incredibly painful and tend to occur frequently, making them particularly distressing for sufferers.

There were anecdotal reports that LSD and psilocybin (the main active ingredient in ‘magic mushrooms’) helped relieve these headaches and researchers have started to investigate more fully.

The Neurology study interviewed 53 cluster headache patients who had used psilocybin or LSD to treat their condition and found a significant number had their condition improved.

As cluster headaches are associated with the abnormal release of serotonin in the brain, and LSD and psilocybin largely work on the serotonin system, there is some theoretical basis for how the drugs might work.

However, this is a complex and poorly understood area so further controlled trials are now being planned to see whether the improvement is anything more than the placebo effect.

Interestingly, the study thanks drugs information site Erowid, as the site was involved in data collection and recruiting participants.

Research into LSD treatment for headaches was discussed in a recent edition of BBC All in the Mind.

Link to full text of paper.

While wandering through a bookshop the other day I picked up a new book by pharmacologist Professor Leslie Iversen called Speed, Ecstasy, Ritalin: The Science of Amphetamines and have been thoroughly hooked [insert your own joke here] ever since.

It covers the history, chemistry, culture, safety and neuropsychology of a huge range of amphetamines and related compounds.

Included are the common ‘street’ amphetamines like speed and meth, pharmaceutical amphetamines like Ritalin and dexamphetamine, and the substituted amphetamines of the ecstasy family.

Oxford Unversity Press are usually good at putting excerpts of their books online (usually the introduction or first chapter) but sadly, there doesn’t seem to be anything similar online for this publication (OUP if you’re listening, now’s the time!)

You won’t find a more comprehensive guide to these fascinating drugs, and the book has the advantage of being written at a engaging pace without skipping over any of the in-depth science. It is not intended to be a ‘popular science’ book but is much more accessible than the majority of academic texts, even for non-specialists.

Even today, over-the-counter inhalers containing amphetamine-like drugs are still available as decongestants, although the compounds now used are ones that act solely on the norepinephrine system in the peripheral sympathetic nervous system and are devoid of psychostimulant properties or abuse potential.

A little known fact is that the popular ‘Vick inhaler’ contains 50mg of methamphetamine (described on the label by the synonym deoxyephedrine) in free base oil form; however, it is not the psychoactive D-isomer of the drug but L-methamphetamine [or levmetamfetamine], which has no psychostimulant properties but retains some sympathomimetic activity. Innocent users of the Vick inhaler to treat the symptoms of the common cold can get into trouble with the law if subjected to a drugs test, as this will indicate the presence of methamphetamine unless the test is sufficiently sophisticated to tell the difference between the L- and D-isomers of the drug! [p31]

Link to details of book Speed, Ecstasy, Ritalin.

There’s a short article from this month’s Scientific American available online where sleep specialist Professor Ernest Hartmann attempts to answer the question “Why do we dream?”.

Hartmann is a psychiatrist and the director of the Sleep Disorders Center at Newton Wellesley Hospital in Boston, but notes that the exact function of dreaming is still largely a mystery, but summarises his recent popular scientific theory of its purpose.

Therefore I will try to explain a current view of dreaming and its possible functions, developed by myself and many collaborators, which we call the Contemporary Theory of Dreaming. The basic idea is as follows: activation patterns are shifting and connections are being made and unmade constantly in our brains, forming the physical basis for our minds. There is a whole continuum in the making of connections that we subsequently experience as mental functioning. At one end of the continuum is focused waking activity, such as when we are doing an arithmetic problem or chasing down a fly ball in the outfield. Here our mental functioning is focused, linear and well-bounded. When we move from focused waking to looser waking thought–reverie, daydreaming and finally dreaming–mental activity becomes less focused, looser, more global and more imagistic. Dreaming is the far end of this continuum: the state in which we make connections most loosely.

Link to Scientific American article ‘Why do we dream?’.

The curious condition of prosopagnosia (something referred to – somewhat incorrectly – as ‘face blindness’) is featured in a short article in Time.

Prosopagnosia is a term used to refer to quite a broad range of neuropsychological difficulties that impair people from recognising others by their face, despite the fact that they may recognise them by other features (such as by voice, or even by a distinctive tatoo) and have little trouble with recognising non-face objects.

The article focuses on recent findings that prosopagnosia can result from inheriting genetic traits, rather than only from brain injury, as was previously thought.

For years, prosopagnosia was associated with damage to the fusiform gyrus and was considered quite rare owing to the fact that this brain structure is quite protected from most sorts of head injury.

The inherited version of the recognition disorder seems much more common, although, perhaps, is less severe is many cases.

The Time article reports on the experiences of some people with the disorder, and some of the recent research on the inherited condition.

We previously featured an interview with Dr Thomas Grueter, one of the researchers mentioned in the article. Interestingly, he has prosopagnosia himself.

Link to Time article ‘Do I Know You?’.

There’s a fascinating study in the journal Neuroimage that reports that people who have had a limb amputated show reduction in the volume of grey matter in the thalamus – a complex deep brain structure.

The study, led by neuroscientist Dr Bogdan Draganski, scanned the brains of 28 patients whose limbs had been surgically removed.

The reduction in grey matter volume was typically found on the opposite side of the thalamus to the amputated limb.

As movement-related brain structures are largely involved with actions on the opposite side of the body, this suggests that the absence of the limb is affecting an area directly involved in its coordination and control.

Crucially, the amount of grey matter reduction was correlated with the time since the limb was amputated, suggesting that the brains of the patients were continuously reorganising in light of the serious change in action, sensation and body image.

These findings are likely to have significant implications for the field of neuroprosthetics that aims to interface prosthetic replacements for damaged body parts directly with the nervous system.

Knowing how the nervous system changes over time in response to injury will enable neuroprosthetic devices to make best use of the remaining function.

Link to abstract of study.

The New York Times has published an extensive article on the effect of drinking on the teenage brain.

Increasing research is now being conducted on the effect of teenage substance use on the brain, as it has recently been discovered that adolescents do not just have ‘young adult’ brains in all respects.

It now seems that the brain may be particularly sensitive during the teenage years, and significant substance abuse may have more of an impact during this time than later in adult life.

While much research has been conducted on cannabis use during adolesence, owing to its effect of increasing the risk of psychosis, attention is increasing being focused on alchohol.

Mounting research suggests that alcohol causes more damage to the developing brains of teenagers than was previously thought, injuring them significantly more than it does adult brains. The findings, though preliminary, have demolished the assumption that people can drink heavily for years before causing themselves significant neurological injury. And the research even suggests that early heavy drinking may undermine the precise neurological capacities needed to protect oneself from alcoholism.

Link to NYT article ‘The Grim Neurology of Teenage Drinking’.