Monday, 19 April 2010

Why does sleep deprivation alleviate symptoms of depression?

Here's a link to an interesting article in the New York Times about depression and sleep that surprised me. A couple of months ago the neighbours upstairs had a new baby. He cries a lot, day and night, and you would think that the sleepless nights his crying causes could easily make anyone depressed. Indeed, postpartum depression can be remarkably common, affecting anything between 5-25% of new mothers in the first few months after giving birth. But if anything, according to this article by Terry Sejnowski, a renowned computational neurobiologist, an entire night without sleep can actually lift symptoms of depression in such afflicted women. Unfortunately, this is no miracle cure. You cannot escape the lack of concentration, irritability and memory loss inevitable after a night without sleep, and even the shortest nap can break the spell. Exactly how sleep deprivation alleviates symptoms of depression is still a still largely unknown, but one avenue of research scientists are currently exploring focuses on general sleep patterns with a particular focus on the rapid eye-movement (REM) stages of sleep. A link between REM sleep and depression has already been made: a common antidepressants blocks REM sleep and people with a genetic predisposition for entering REM sleep very early on in their sleep cycle are at a larger risk of becoming depressed. Thus, while staying awake for one night may not actually, at least not in a longer term, cure or even treat depression effectively, the alleviating effects of staying awake may give scientists an interesting direction for research into depression.

Friday, 16 April 2010

Freud's full circle?

While Freud's theories have had an enormous impact on psychiatry - psychoanalysis today still uses similar methods to the ones Freud developed in the beginning of the 20th century - they have long been engulfed in controversy. Freud's psychoanalytical thinking focused on the understanding of human behaviour by gaining access into the unconscious mind. In a typical session on Freud's sofa you might talk about your dreams and fantasies, letting your mind wander and speak without controlling your thoughts. Freud would listen to you, absorbing your thoughts and interpreting them, unravelling the unconscious conflicts that caused the symptoms for which you came to this session. Unveiling and subsequently dealing with these unconscious conflicts would cure the original symptoms of your mental instability.

One of the major criticisms of Freud lies in the lack of experimental scrutiny that surrounds his methods of baring the unconscious. Such lack of experimental evidence was, and still is, seen as unscientific. In the 1960s and 70s however, the idea of the presence of the unconscious re-emerged and became of particular interest for neuropsychologists who were trying to gain understanding in seemingly unconscious processes in split-brain patients and in disorders such as Alien Hand Syndrome. In split-brain patients, all the connecting fibres between the two sides of the brain were surgically cut to alleviate severe symptoms of epilepsy such that there are no direct routes for communication between the two halves of the brain any more. While this undoubtedly helped reduced the severity of symptoms, this procedure also had some other interesting effects. In a series of experiments that went on to gain him a Nobel Prize, Roger Sperry showed that each hemisphere could seemingly have simultaneous systems of volition. For instance, when he showed a split-brain patient a picture on the left side of a computer screen, which will be processed by the right side of the brain, the side that usually does not contain the language areas, they would tell him they had not seen anything. However, when he then asked them to select an object from several alternatives with their left hand (the one controlled by the right hemisphere), they would choose the object that was presented to them just a second ago even though they could not express why they had picked that exact object.

While complete sections of the corpus callosum tend no longer to be performed, similar bizarre “unconscious” desires also manifest themselves in patients with particular brain damage that affects this region. For instance, in patients with Alien Hand Syndrome one hand does something completely different and independent from the other. Perhaps the most famous example was Dr. Strangelove, who had to keep one hand in control with the other. Another compelling example is that of a woman who was determined to smoke a cigarette, but whenever her one hand had put the cigarette in her mouth, the other would grab it and throw it away.

In fact, as Emeritus Professor of Neuropsychology at Oxford Larry Weiskrantz has pointed out, a curious facet of many clinical syndromes caused by brain damage is that, while these patients may lose particular conscious faculties such as being able to recall past events or identify people by their faces, they still retain “unconscious” abilities to do exactly these things. A patient with prosopagnosia may not consciously be able to recognise faces as a result of damage to the temporal lobe, a region in the lower part of the brain particularly important for memory, but will still able to show changes in arousal when seeing someone familiar.

Today, with the ability to look inside the human brain while someone is ‘thinking’, we can observe the processes that go on inside, even the unconscious ones. With such brain imaging techniques neuroeconomists have already started to gain insight into unconscious thought processing by showing that when we make economic decisions, for instance buying something on eBay, we tend to depend much less on our conscious, rational deliberation and much more on subconscious gut feeling and emotion. Perhaps Professor John-Dylan Haynes at the Bernstein Center for Computational Neuroscience in Berlin made an even more intriguing discovery: he was able to predict, by looking at someone’s pattern of brain activity with functional neuroimaging, what a person is going to do and when they will do it nearly 10 seconds before he or she actually does it.

In an article published in Brain this week, Robin Carhart-Harris and Karl Friston argue that with the aid of these brain-imaging techniques, Freudian concepts might now be tested experimentally. Until recently, one of the most common ways to analyse brain imaging data was to directly compare networks of brain activation during a specific task to networks of activation during periods where the brain was assumed to be at rest. However, over the past ten years, research pioneered by Marcus Raichle started looking into what was actually going on in the brain during these periods of rest. Surprisingly, he and his colleagues noticed that the patterns of activity during rest periods were remarkably consistent, which lead him and other researchers to suggest the existence of a “default” network. According to Carhart-Harris and Friston this default network might represent intrinsic internal thought remarkably consistent with the unconscious thought processes in Freud’s later theories. Many of the key principles of Freud's theory they argue, such as 'the ego' (our conscious self) and 'the id' (our unconscious self), echo our current knowledge of how the brain functions on a global level (i.e. a different set of areas in the brain that is active during conscious processing from the set that is active during unconscious processing).

Could it be that, after his initial success and subsequent fall from grace, Freud has now come full circle? Appropriately, it turns out that even Freud himself had originally attempted a not dissimilar scientific approach in the Project of Scientific Psychology published in 1895. In his neurophysiological theory he suggested that the transfer of energy between neurons in the brain caused unconscious processes, but in the years to come he decided that neuronal processing as understood at the time seemed much too complex for such an interpretation. Instead, as a result of his analyses of dreams, he proposed that the unconscious was a result of highly condensed, symbolic thoughts – the primary processes – and the conscious a highly rational and logical way of thinking – the secondary processes. That neuroscientists are, consciously or unconsciously, currently returning to these ideas would likely have amused Freud.

This post also appeared on Cherwell's Matter Scientific

Thursday, 8 April 2010

A day at the museum ...

Much to my shame I have to admit that it has taken me well over two years of living in Oxford to visit the Pitt Rivers Museum and the History of Science Museum. Now that I finally have, I want to spread the word and urge everyone to go. 

In 1884, Augustus Henry Lane Fox Pitt Rivers gave his collection of nearly 20,000 objects collected from many different cultures all over the world to the University of Oxford. As Pitt Rivers wanted it, the collection, spanning two floors in the beautiful open plan building behind the Natural History Museum (in itself worth a visit - don't forget to look up to see the amazing glass roof!), is grouped according to how the objects were made and what they were used for rather than on the basis of their age and cultural origin. This makes it easy to compare objects both through the ages and between cultures. The museum displays an excellent selection of medical tools through the ages and, in one of the many drawers you're allowed to open, you can find a collection of pendants, dead frogs, mole feet, and even a 20-year-old hot cross bun, all used to cure diseases. Or move on to one of the most macabre things I've ever seen on display in a museum: the shrunken heads. The heads belonged to the less fortunate in battle and were hung around the neck of conqueror.

Once you’ve had your fill of the Pitt Rivers’ gothic charms, you can turn your attention to the relics of past scientific endeavours down the road at the History of Science Museum. To gain entrance to the 17th century building which houses the collection, you have to pass by four imposing “emperor's heads” and climb a grandiose set of steps, but once inside, it is the small scale and beauty that strikes you. Throughout, you can find an amazing collection of scientific instruments, from the first camera to the largest collection of ancient astrolabes in the UK. Perhaps the most famous object in the museum is the blackboard with Einstein's notes from a 1931 lecture given in Oxford dealing with some of the fundamental questions in cosmology. Rivalling some of the gruesome fascination of the Pitt Rivers’ shrunken heads is the display of medical instruments through the ages. As I stood in front of the display, I couldn’t help but imagine the sheer brutality of the procedures and the pain people in the Middle Ages must have gone through to have their limbs amputated. The museum also features special exhibitions alongside their permanent collection. In Steampunk, both the name of the exhibition and an art form, they wonderfully displayed the marriage between science and art showing objects (scroll down for some images of the objects) with futuristic ideas that are at the same time reminiscent of the past in the intricacy of their construction.

It is nice to know that one does not have to travel all the way to London to have your imagination transported and see the way in which human ingenuity, engineering and superstition have all played a role in our scientific progress.