You’ll feel better in the morning: Sleep deprivation disconnects the emotional brain January 27, 2008Posted by Johan in Emotion, Neuroscience, Sleep.
Disturbed sleep patterns feature in a range of psychiatric disorders, many of which fall under the DSM’s mood disorder category. A recent paper by Yoo et al (2007) suggests that sleep deprivation itself can produce abnormal affective processing. In other words, sleep disturbances may be a cause as well as a symptom in conditions such as depression.
Yoo et al (2007) approached this issue with fMRI. Brain scans were taken of one participant group who had been sleep deprived for 35 hours, and one group who had slept normally. The participants viewed emotional pictures from a standardised set (the international affective picture system), which varied gradually in valence from neutral to aversive.
Yoo et al approached the imaging analysis with a few theoretical notions, which formed the basis of the brain areas that they investigated more closely. First, the amygdala is believed to mediate the emotional response to the aversive pictures, and secondly, it is argued that responding in the amygdala is mediated by an inhibitory projection from medial prefrontal cortex (a frequently invoked projection – see this related post).
To address the first issue, Yoo et al compared the amygdala response to the aversive pictures in the two groups. The amygdala was more activated bilaterally in the sleep-deprived group, and furthermore, a larger volume of amygdala was activated in this group as the figure at the top of this post shows. Note that the neutral pictures elicited no greater amygdala responses in the sleep-deprived group, so this is a case of greater amygdala re-activity, rather than an increase in baseline responding.
The role of medial prefrontal cortex in mediating the amygdala reactivity was investigated by measuring the regions that showed functional connectivity with the amygdala during the task. The method isn’t straightforward, but essentially it’s based on taking the activity in the amygdala voxels, and assessing which other brain regions show responses that covary. The results are given as a contrast between the two groups.
As the yellow bits in the figure show, the sleep control group displayed stronger amygdala-prefrontal connectivity than the sleep-deprived group. Conversely, the amygdala had stronger connectivity with various regions of the brainstem in the sleep deprived group compared to the sleep control group.
So to re-cap: sleep-deprived participants showed larger amygdala responses, and their amygdalas showed weaker functional connectivity with medial prefrontal cortex. This finding does not prove that the greater amygdala response in the sleep-deprived group was caused by the weakened connectivity with medial prefrontal cortex, but it is certainly consistent with that notion. Yoo et al suggest that sleep acts as a kind of reset of brain reactivity, to ensure that emotional challenges can be met appropriately. But why is such a reset necessary in the first place? Why is the regulatory influence of medial prefrontal cortex weakened by sleep deprivation? The role of sleep in affect is only beginning to be understood.
Yoo, S-S., Gujar, N., Hu, P., Jolesz, F.A., & Walker, M.P. (2007). The human emotional brain without sleep – a prefrontal amygdala disconnect. Current Biology, 17, 877-878.
In Defense of Electroconvulsive Therapy October 30, 2007Posted by Johan in Abnormal Psychology, Applied, Emotion.
The TED talks website contains material for a hundred posts, but a video posted earlier today hits particularly close to home. In this talk, Sherwin Nuland, a surgeon turned writer, gives an authoritative and unexpectedly personal account of the history of electroconvulsive therapy (ECT), sometimes known as electric shock therapy. The talk is only about 20 minutes, and gets very interesting around the 7 minute mark where Nuland describes how ECT once saved his life, as he puts it.
If the general public could be accused of placing too much trust in antidepressant medication, the reverse is certainly true of ECT. Ask anyone about electric shock therapy, and they’ll conjure up horror stories, and associations with frontal lobotomy. This is unfair, since there is some evidence that ECT actually works for depression.
The research on this issue has produced mixed results and plenty of controversy, as reviews by Challiner and Griffiths (2000) and by the UK ECT Review Group (2003) outline. However, there is no shortage of positive findings, and this in itself is rather remarkable, when you consider the patients that receive it. Since ECT is considered rather drastic, it is only really considered for patients who are severely depressed, and who have failed to respond to antidepressants. In other words, ECT is usually only considered in cases with the worst possible prognosis, so the fact that it does seem to help at times is quite powerful in itself, given the probability of spontaneous recovery from such conditions. That being said, a read of the ECT literature is unsatisfying. Because ECT is viewed as such a dramatic intervention (even in the absence of evidence that it causes long-term harm), it has rarely been tested on “normal” depressives in random control trials.
As Challiner and Griffiths (2000) outline, a lot of the popular conceptions of ECT are untrue. It doesn’t cause massive spasms – muscle relaxants are administered. It is not going to be a traumatic experience, because you will be put under a general anaesthetic. Although bilateral administration of ECT has been associated with memory loss, this does not appear to happen with unilateral administration, where both electrodes are kept on one side of the head (as shown in the picture at the top).
There is another issue with ECT, which I think bothers practitioners than clients. In the case of antidepressants, we at least know how they work, although it is far from clear why boosting synaptic Serotonin levels should work, given the weak evidence for a lack of Serotonin in depression. With ECT, there are no convincing explanations for either the how or the why. Psychiatrists stumbled upon ECT in the happy days of wild experimentation that preceded Ethics Committees, without much of a theory. It is quite embarrassing that even to this day, we can say so little about what this treatment does, or indeed if it even does anything at all – a pertinent question given the claim on Wikipedia that 1 million people receive ECT each year worldwide.
If I ever developed a severe depression, I would try ECT before antidepressants. Unlike antidepressants, the effects of ECT can be instantaneous, and there are no long-term side-effects, nor any withdrawal symptoms when the treatment ends. Since the treatment is extremely safe when administered properly, there is really very little to lose.
Challiner, V., and Griffiths, L. (2000). Electroconvulsive therapy: a review of the literature. Journal of Psychiatric and Mental Health Nursing, 7, 191-198.
The UK ECT Review Group. (2003). Efficacy and safety of electroconvulsive therapy in depressive disorders: a systemic review and meta-analysis. Lancet, 361, 799-808.
AI detection of facial expressions September 7, 2007Posted by Johan in AI, Applied, Emotion, Face Perception.
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I’ve written previously about how algorithms that detect faces in images are appearing everywhere, including Google Images and many recent digital cameras, where they are used to ensure that focus is on the face (presumably, no one who buys a Cybershot is interested in the aesthetic effects of not having the face in focus).
This technology is being expanded into the realm of specific facial expressions by OMRON (among others), a company that just released software that promises to measure the smile factor of faces in a picture. The smile factor as OMRON conceives of it goes from 0 to 100 %, and will presumably serve to shift the blame nicely when you want people to smile more in a picture (“look, I think the picture is fine, but the camera thinks you should be smiling more”). It is only a matter of time before this makes it into digital cameras, soon followed by a spinach-on-the-teeth detector.
Other proposed applications for OMRON’s software include human-computer interactions, and as an objective measure of liking in food tasting studies. I imagine the software would also be useful for more theoretical investigations into emotional expressivity. As it stands, scoring the magnitude or kind of expression manually is quite tricky.
It never ceases to amaze me how object recognition software is steadily advancing along the ventral visual stream.