Month: June 2005

Open-access science journal PLoS Biology reports on research looking at how the brain handles object recognition among the clutter of the everyday visual world.

Researchers, led by neuroscientist Zoe Kourtzi, asked participants to detect objects hidden in various background images, whilst being scanned in an fMRI scanner.

“The authors found that subjects demonstrated an increased number of correct responses for shapes they encountered during the training sessions, regardless of the type of background the shapes were presented on. By contrast, the fMRI responses differed dramatically, depending on whether the surroundings made the shapes easy or difficult to detect.”

“These results demonstrate that the ability to learn to detect novel shapes is independent of the degree of difficulty, but suggest that the brain employs different mechanisms of perceptual learning depending on whether the objects stand out from their surroundings, or are obscured by them.”

Link to summary of study.
Link to full-text of study.

This week’s edition of the science journal Nature reports that single brain cells may be specialised for recognising specific faces.

This is an interesting finding, as it provides support for a derided hypothesis known as the ‘grandmother cell‘ theory, that was thought up to ridicule attempts to reduce human experience down to smaller and smaller components of the brain.

Neuroscience often develops by trying to understanding how smaller parts of the brain support larger processes. Bologist Jerry Lettvin argued that we can’t expect everything to reduce down to the smallest level, as some things will be distributed across the brain.

It is unlikely, he argued, that there is a single brain cell to represent each person we know, a neuron that is active when we see our grandmother, for example.

This has since been used as an argument against any theory that is seen as over-simplifying how things are represented in the brain.

But now, a team led by neuroscientist Rodrigo Quian Quiroga has identified neurons which do seem to be active for individual faces.

He implanted harmless electrodes into the temporal lobes of volunteers undergoing surgery for epilepsy.

Quiroga then showed the participants pictures of famous faces, and discovered some cells were only active for individual faces in the set – Halle Berry, or even members of The Simpsons.

Of course, it’s impossible to say whether these cells are truly selective for an individual face out of all the ones a person may know, but this level of selectivity is a great surprise for those who thought individual cells would be active for very general features of the visual world.

Link to write-up from nature.com
Link to study abstract.

Finally, someone has done a neuroimaging study of the female orgasm.

Although the paper from this study has not been published yet, if the conference reports are anything to go by, it may be the first functional neuroimaging study of orgasm in healthy human females.

My only caveat is the rather random way this story is being reported (e.g. ‘Brain scans detect fake orgasms’) and the seemingly odd quotes from the researcher involved (from a BBC News story):

Professor Holstege said: “Women can imitate orgasm quite well. But with genuine orgasm”, he said: “What we see is an extreme deactivation of large portions of the brain hippocampus and especially the emotional parts involved with fear… And if you are fearful, it is very hard to have sex. It’s very hard to let go.” He said this was useful for men to know. “When you want to make love to a woman, you must give her the feeling of being protected.”

If reported correctly, Prof Holstege seems to have gone from a discovery about a reduction in brain activity (possibly based on a weak clich√© that the amygdala circuit is the ‘fear’ part of the brain) to advice on ‘how to make love to a woman’.

Come again ?

Link to story from newscientist.com
Link to story from BBC News.

The Arizona Daily Star is reporting that doctors are being warned that some general anaesthetics are associated with sexual dreams which some people may remember as real.

Although it is almost impossible to verify how often sexual hallucinations occur, some studies indicate it happens in 1 percent to 3 percent of anesthetized patients, Strickland said. With some anesthetic drugs – such as ketamine or propofol – the incidence is up to 5 percent.

Just why it happens is not well understood. But the risk is higher under lighter, sedating anesthesia than under deep anesthesia, doctors have found.

Link to article from Arizona Daily Star (via BoingBoing)
Links one and two to cases on PubMed.

Numenware is a recently re-launched blog that covers the developing world of neurotheology – the neuroscience of spiritual experience and belief.

The site is authored by Bob Myers, who manages to approach the subject in a critical but non-dogmatic way and avoids scoring easy points on complex topics.

Some of my favourites include a post musing about a neurological basis of average age of enlightenment, one on developmental neurotheology, and note on the possible adaptive value of near-death experiences.

Link to numenware.com

A study published online by the British Medical Journal suggests that people with epilepsy or a family history of epilepsy may be more likely to develop schizophrenia or psychotic symptoms.

Researchers from the University of Aarhus analysed the records of 2.27 million Danish people, and found the risk of schizophrenia-like psychosis slightly raised in people with epilepsy, or those with family members who have epilepsy.

The absolute risk still remains small however, as only 1.5% of the people with epilepsy went on to develop psychosis.

The significance of these findings are in the suggestion that epilepsy and psychosis may have some common genetic influences. This influence is likely to be complex however, as demonstrated by a curious interaction.

The study found that people with epilepsy were more likely to develop psychosis if there was no family history of psychosis or schizophrenia.

Link to story from Yahoo News.
Link to study abstract.

UPDATE: The BMJ have just published a ‘rapid response‘ I submitted about the article’s findings.

A research team has announced that they have developed a brain imaging technique to detect the early stages of Alzheimer’s disease with a claimed accuracy of 78%.

The technique, named HipMask and developed by neuroscientist Lisa Mosconi and her team, uses a brain scanning technique called PET. This involves injecting weakly radioactive glucose into the blood and measuring where it accumulates in the brain.

Glucose is used as ‘fuel’ by the brain, so brain activity in a particular location can be inferred from measuring the levels of radioactivity.

Mosconi’s team have discovered that poor levels of activity in a brain area called the hippocampus, a crucial memory area, predict the onset of Alzheimer’s disease up to 9 years before standard diagnosis.

Because the hippocampus is small and hidden deep within the brain, measuring its activity has been traditionally considered quite hard, as it produces a relatively weak signal.

Mosconi’s team overcame this problem by also using an MRI scan of the brain, which gives a more accurate internal picture, to complement the PET scan, which gives a clearer measure of hippocampal function.

Link to write-up of study from from Eureka Alert.
Link to story from Yahoo News.
Link to study abstract.

Jack El-Hai, the biographer of surgeon and early lobotomy enthusiast Walter Freeman is interviewed on ABC Radio’s In Conversation.

El-Hai has written The Lobotomist: a maverick medical genius and his tragic quest to rid the world of mental illness, that follows Freeman’s life, and the history of psychosurgery – the use of brain surgery to attempt to treat mental disorder.

Freeman is now a controversial character, and many see his enthusiasm for doing literally hundreds of lobotomies as verging on abuse of vulnerable patients, whereas Freeman himself argued that his was an effective treatment for otherwise untreatable people.

One of Freeman’s most notable lobotomy patients was Rosemary Kennedy, sister of JFK – an episode El-Hai describes as “one of the worst” in Freeman’s career.

Realaudio or webpage of In Conversation on Walter Freeman.
Link to New Statesman review of El-Hai’s book.
Link to the book’s website with first chapter online.