Mind Hacks

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’.

Terry Wallis, a man who was in a coma-like minimally conscious state for 19 years after a car crash, seems to have shown brain re-growth since he recovered consciousness.

A research team led by Henning Voss scanned Wallis’ brain using a technique called diffusion tensor imaging or DTI that can pick out the white matter pathways in the brain.

An image from Wallis’ DTI scan is shown on the left, and shows the connections in the rear section of the brain.

The image is shown as if we’re looking down and from the side into the brain. Note how the structures do not match on either side – often a good indicator of brain injury.

Crucially, the researchers re-scanned Wallis’ brain after 18 months and found that the density of the white matter seemed to increase over time, suggesting that his axons were regenerating. These are the long insulated fibres that connect the brain’s neurons.

When scanned using a PET scanner, the increase in white matter also seemed to match an increase in the use of glucose, suggesting greater levels of brain activity in these areas.

In the last decade it was discovered that adults can grow limited numbers of new neurons, but the regeneration of the brain’s connections is still largely unknown, and especially not in people who have suffered such severe brain injury.

Wallis was the subject of a 2005 Bodyshock documentary called The Man Who Slept For 19 Years.

Contrary to depictions in many films (where people tend to gently open their eyes and return to normality), Wallis is still markedly disabled by his brain injury and is not able to care for himself.

Wallis’ recovery is no less remarkable, however, and highlights shortcomings in the scientific understanding of both coma-like states and the neuroscience of consciousness.

UPDATE: Pure Pedantry has a great article looking at some of the background issues to do with this case, such as the exact definitions of different coma-like states. Well worth checking out.

Link to ‘Rewired brain’ revives patient after 19 years from New Scientist.
Link to write-up from The Age (thanks Kate!)
Link to full-text of scientific study.
Link to previous Mind Hacks story on minimally conscious state.