How does the human brain decide what information to attend to and what information to ignore?
Relevance detection refers to neural processes determining the salience of a stimulus.
According to the Appraisal Theory of Emotion, relevance detection is mainly modulated by three variables:
1) Novelty (in terms of familiarity and/or predictability)
2) Pleasantness (in terms of neutral, positive or negative valence)
3) Goal / Need Relevance (in terms of social versus nonsocial or communicative relevance, etc.)
In a number of research projects, I tried to disentangle the effects of these three variables on brain activity, both on a temporal (EEG) as well as a functional anatomical (fMRI) level. Main region of interest was the amygdala (see references by Sander, Ousdal, as well as Pessoa and Adolphs). I was also interested in individual differences influencing such processes.
Social versus Emotional Relevance
In one study published in Frontiers in Human Neuroscience (2013), we investigated the neural substrates of social versus emotional relevance. In order to do so, we presented images to healthy adult participants that could either have a social or nonsocial content, and be of either positive, negative or “neutral” valence.
We found that in several brain areas, comprising the bilateral amygdala, fusiform gyrus, anterior superior temporal gyrus and medial orbitofrontal cortex, brain activity reflected interactive processing of social content and valence. Firstly, activity was always higher to emotional versus neutral images. Second, activity was always higher to social versus nonsocial images. And third, activity to social images did not significantly differ as a function of positive versus negative valence, whereas for nonsocial images, activity was higher for negative versus positive images (see Figure above illustrating such pattern in bilateral amygdala).
Our findings suggest that the human brain, or at least the regions mentioned above, attribute(s) stronger relevance to social (versus nonsocial) information, regardless of valence. This reflects the notion that social information is highly salient for human behavior per se. In turn, probably because of the higher biological salience in terms of survival, nonsocial negative (versus positive) information is preferentially processed, allowing for a fast detection of potential threats.
Emotional versus Social Relevance versus Novelty
In another study published in Emotion (2013), we examined brain responses to dynamic emotional facial expressions and comparable nonsocial stimuli (“lottery game”) as a function of stimulus novelty and valence. Novelty was conveyed by the presence versus absence of surprise, while novelty was reflected by positive versus negative versus neutral valence. We were especially interested in how the amygdala processes such different kinds of stimulus relevance.
Our findings revealed an intriguing activation pattern, for both social and nonsocial stimulus processing. The amygdala did not seem to differentiate between valence and novelty as such, but was more strongly activated to dynamic information containing positive versus negative surprise. According to the available literature, and particularly a previous study by Yacubian et al. (2006), such findings suggest that the human amygdala – at least under conditions of uncertainty involving surprise – (i) encodes a negative expected value (anticipation of a negative outcome), and subsequently (ii) updates such expectation by means of a negative expected value prediction error if a positive outcome occurs instead.
Our data propose that relevance processing in the human amygdala may not only be modulated by the static versus dynamic nature of stimulus presentation, but also depend on the degree of uncertainty / predictability of information.
For more detailed information regarding my research on relevance detection, please refer to the Publications page or contact me with any questions.