All emotions can be evaluated with fair accuracy on the basis of their position on unpleasantness-pleasantness, or valence, dimension. Valence has been considered to be a linear continuum both on experiential and neural level, ranging from very unpleasant to very pleasant. However, using such a model it is difficult to explain complex emotional states, in which we can simultaneously experience unpleasantness and pleasantness, like during a rollercoaster ride or a horror film. Also experiments with rats, where experimenters have been able to cause simultaneous approach and withdrawal behavior, suggest that pleasantness and unpleasantness may be encoded by different mechanisms. In this thesis, the neural mechanisms of emotional valence were investigated in four different experiments with three different valence models: a traditional linear model, a quadratic model, and a model, in which negative valence and positive valence are represented as separate components. Whereas no study gave any support for the validity of the linear model, all four experiments provided evidence of quadratic valence dependency, and two of the experiments found additionally brain regions specifically sensitive to pleasantness and/or unpleasantness. In particular, these regions included bilaterally the dorsal and ventral prefrontal cortex and insula. Brain activity was measured with functional magnetic resonance imaging. Non-linear dependency between valence and brain activity was found for emotional pictures and sounds, observation of others' facial expressions as well as subjective emotional experience. The results demonstrate that valence processing does not occur in the brain simply in linear bipolar fashion, but the phenomenon is non-linear and multifaceted.
|Translated title of the contribution||Emotionaalisen valenssin edustus ihmisaivoissa|
|Publication status||Published - 2012|
|MoE publication type||G5 Doctoral dissertation (article)|
- human brain