Psychopharmacology of emotion processing

Some more stuff I learned about at the EPS meeting below the fold.

As before, caveats apply: this includes as-yet-upublished work, so things may not be quite as straightforward as put here; also, it’s possible for me to miss, or even misunderstand, what the speaker is saying.

Catherine Harmer and her colleagues have been looking at the effects of serotonin on fear perception, as part of ongoing investigations into its role in this area. They make a persuasive case that these effects are genuine and are independent of the subjective level of anxiety the recipient feels. That is, the drug isn’t just ‘calming you down’ and making you less jumpy: in addition, your cognitive system is oriented away from processing fear. The evidence that it influences cognition in the absence of anxiety changes comes from studies in which a single dose of a seretonergic agent is given; they found a cognitive effect of the dose even though subjective anxiety was unaltered, although interestingly the effect was that of a heightened response to fear stimuli.

In another experiment repeated sub-chronic doses were administered, and the effect reversed – fear was more poorly recognised – and was extended to other some other emotions, of which particular emphasis were given to Anger and Disgust. The most common kind of errors that were made were incorrect selections of happiness. In the talk, the findings were characterised as a decrease in negative processing; whilst I like the coherence this brings – antidepressants make you see the bad things in life more positively – I’ve been turning over an alternative hypothesis. What wasn’t discussed in the talk, but was apparent from the figures, was the effects of chronic dosage on a couple of other emotions, surprise and sadness.

Surprise is as un-valenced(neutral) as an emotion can get, to the extent that many people are dubious about it being an emotion at all. Nevertheless, the drugs lead to worse accuracy on surprise expressions. Meanwhile, sadness is clearly a negative emotion – arguably the emotional state with the closest correspondence to depressive mood (though I stress they are not the same thing) – and recognition of sad faces is not affected by the drugs. This leaves the findings open to a different interpretation, I think, being that seretonergic drugs lead to a decrease in processing of urgent stimuli. Fear, disgust, surprise and anger all triggered by a cue that needs to be responded to, whilst happiness and sadness much more enduring states that are not initiated by an urgent situation. It seems plausible, and while I suspect the explanation presented is likely to be right, this objection would need to be countered first.

For those of you fans of what is happening inside the brain, an fMRI study showed less activation of the amygdala (implicated in the processing of a number of emotions, most notably fear) in subjects taking citalopram rather than placebo, when they were subliminally presented with fearful stimuli (meaning faces showing fear, rather than images of your parents discovering your stash).

In any case, the evidence that anti-depressants have a role in mediating our experience of emotional (or potentially stressing) elements in the environment casts an interesting perspective on what may be lifting the mood of the medicant.

Links: Earlier work showing the effects of a serotonergic agent on fear perception
Also, this looks spot on, but I can’t source it in the journal, so it’s probably been miscited in some way:

Harmer CJ, Bhagwagar Z, Cowen PJ, Goodwin GW. Acute administration of citalopram in healthy volunteers facilitates recognition of happiness and fear. J Psychopharmacol 2001a; 15 Suppl: A16.

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