Author: vaughanbell

Open-access science journal PLoS Biology reports that high strength magnetic pulses, targetted at a specific area of the brain, can make areas of the body more sensitive to touch.

The use of focused magnetic pulses to stimulate the brain, a technique known as transcranial magnetic stimulation or TMS, is now becoming commonplace in neuroscience research.

It allows researchers to slightly alter the function of a brain area using a hand held magnetic coil. The resulting changes can hopefully be detectable using behavioural or psychological measures.

Like most neuroscience studies, research projects using this technique start by wondering whether a particular brain area is necessary for a particular type of mental activity or behaviour.

Unlike other techniques, such as brain scanning – that typically only find correlates of thought or behaviour – TMS allows researchers to make causal inferences. In other words, they can judge whether the area they are targetting is involved in causing the thought or action to occur.

Traditionally, TMS is used in research to safely inhibit or disrupt function in a brain area for a short period of time. More recently, it has been found that TMS (particularly when given in ‘trains’ or repetitive bursts) can be reliably used to increase activation in brain areas, over longer time periods.

The PloS Biology study targetted an area of the brain involved in somatosensory functions (mainly touch and body image) and found that they could increase skin sensitivity on the finger, when they aimed for the brain area that holds the ‘finger map’.

Link to PLoS Biology summary.
Link to story from nature.com.
Link to PLoS Biology full text paper.

The New York Times has an insightful article on the utility of brain scans for helping and treating people with mental illness.

Mental illness is diagnosed on the basis of a clinical interview, where the clinician interviews the patient and encourages them to explain aspects of their first-person experience.

This means that the criteria for diagnosis, although internationally agreed upon, are subjective – in that it is the clinician who decides whether they are present or not.

For example, the DSM criteria for clinical depression include items such as depressed mood, loss of pleasure, feelings of guilt and low self-esteem. None of these can be measured objectively.

When brain scans arrived, particularly those that measured brain function, it was hoped that there would finally be an objective test for many mental disorders based on the biology of the brain.

There has been some success in finding biological differences between the brains of healthy and diagnosed individuals. The problem is that these differences are not reliably diagnostic.

For example, when a group of people with depression and without depression are compared, reliable differences in brain function can be found. However, this only reflects the fact that individuals with the diagnosis are more likely to show the difference, but there are also individuals with the diagnosis who do not have the same differences.

This also ignores the fact that the diagnosis and definition of mental illness are often culturally influenced. The fact that homosexuality was classified as a mental disorder by the American Psychiatric Association until 1973 is a notorious example.

Another complication is that there is often an element of subjective decision making in analysing brain scans – to produce the familiar ‘brain images’ we are used to seeing.

The media often miss many of these subtleties, portraying brain scans as more impressive than many scientists give them credit for.

The New York Times article, therefore, does an admirable job of tackling some of these issues and outlining the promises and pitfalls of the neuroscience of mental disorder.

This comes at a time when psychiatry is looking beyond the current diagnostic manuals as the sole definition of mental disorder, and considering the concept of the ‘endophenotype‘ – measurable aspects of biology thought to be the key underlying components that increase risk for mental disorder.

Link to New York Times article ‘Can Brain Scans See Depression?.
Link to academic paper on the ‘endophenotype’ concept.

Mind Hacks radio favourite All in the Mind has an edition on confabulation, the brain injury-related condition where patients produce sometimes bizarre false memories.

Although patients obviously report untruths when asked a question, confabulation is not considered lying, as patients do not seem to be deliberately deceiving the listener.

Some confabulations are fairly mundane. For example, I met one paralysed patient who explained that he spent the morning walking in the park when asked how his day had been.

Others can be quite fantastical. Another gentleman claimed he had received ‘splinters’ in the head from a machine gun malfunction when fighting aliens.

It is thought that confabulation occurs because the areas of the brain involved in controlling recollection and evaluating the resulting memories (particularly the the frontal lobes) are damaged.

Confabulations are thought to be different from delusions, as they are usually not fixed, with some patients reporting different things when asked the same question again.

The study of confabulation is also interesting because it inspired one of the only neuropsychological studies to use a qualitative approach (i.e. not converting behaviour into numeric measurements).

Neuropsychologists Paul Burgess and Tim Shallice asked friends to recall life events, such as a recent holiday, and <a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8817460&query_hl=2
“>examined transcripts of their discussions to see how people verified their memories (e.g. “It must have been in June, because it was just after my brother’s birthday…”).

From this they generated a model of normal memory verification and proposed how it could break down after brain injury.

All in the Mind discusses this intriguing condition, with the recently moved-to-Australia Martha Turner, and London based researcher Katerina Fotopoulou.

mp3 or realaudio of programme.
Link to programme transcript.
Link to short article about confabulation.

Researchers have identified a gene that seems to be involved in the amount of deep or ‘slow wave’ sleep a person gets during the night.

Slow wave sleep, typically characterised by EEG readings of less than 5 cycles per second, is thought to be important for allowing the brain to change its structure.

This process of reorganisation is known as ‘plasticity’ and is thought to be particularly important for the consolidation and filtering of memories.

Led by sleep researcher Julia Rétey, the team from the University of Zurich found that different versions of the gene related to the breakdown of the neurotransmitter adenosine were present in people who differed in their duration of slow wave sleep.

Interestingly, caffeine’s sleep fighting properties are thought to be due to the fact that it blocks adenosine receptors, suggesting that the adenosine system may be a crucial piece in understanding how and why we sleep.

Link to article on study from Science website.
Link to study abstract.
Link to excellent Wikipedia article on sleep.