Motor-Incompatibility of Facial Reactions : The influence of valence and stimulus content on voluntary facial reactions

Emotional cues facilitate motor responses that are associated with approach or avoidance. Previous research has shown that evaluative processing of positive and negative facial expression stimuli is also linked to motor schemata of facial muscles. To further investigate the influence of different types of emotional stimuli on facial reactions, we conducted a study with pictures of emotional facial expressions (KDEF) and scenes (IAPS). Healthy participants were asked to respond to the positive or negative facial expressions (KDEF) and scenes (IAPS) with specific facial muscles in a valence-congruent (stimulus valence matches muscle related valence) or a valence-incongruent condition (stimulus valence is contrary to muscle related valence). Additionally, they were asked to rate pictures in terms of valence and arousal. Muscular response latencies were recorded by an electromyogram. Overall, response latencies were shorter in response to facial expressions than to complex pictures of scenes. For both stimulus categories, response latencies with valence-compatible muscles were shorter compared to reactions with incompatible muscles. Moreover, correlations between picture ratings and facial muscle reactions for happy facial expressions as well as positive scenes reflect a direct relationship between perceived intensity of the subjective emotional experience and physiological responding. Results replicate and extend previous research, indicating that incompatibility effects are reliable across different stimulus types and are not limited to facial mimicry

Inhibition of return in fear of spiders: Discrepant eye movement and reaction time data

Inhibition of return (IOR) refers to a bias against returning the attention to a previously attended location. As a foraging facilitator it is thought to facilitate systematic visual search. With respect to neutral stimuli, this is generally thought to be adaptive, but when threatening stimuli appear in our environment, such a bias may be maladaptive. This experiment investigated the influence of phobia-related stimuli on the IOR effect using a discrimination task. A sample of 50 students (25 high, 25 low in spider fear) completed an IOR task including schematic representations of spiders or butterflies as targets. Eye movements were recorded and to assess discrimination among targets, participants indicated with button presses if targets were spiders or butterflies. Reaction time data did not reveal a significant IOR effect but a significant interaction of group and target; spider fearful participants were faster to respond to spider targets than to butterflies. Furthermore, eye-tracking data showed a robust IOR effect independent of stimulus category. These results offer a more comprehensive assessment of the motor and oculomotor factors involved in the IOR effect

Brain Activations to Emotional Pictures are Differentially Associated with Valence and Arousal Ratings

Several studies have investigated the neural responses triggered by emotional pictures, but the specificity of the involved structures such as the amygdala or the ventral striatum is still under debate. Furthermore, only few studies examined the association of stimuli's valence and arousal and the underlying brain responses. Therefore, we investigated brain responses with functional magnetic resonance imaging of 17 healthy participants to pleasant and unpleasant affective pictures and afterwards assessed ratings of valence and arousal. As expected, unpleasant pictures strongly activated the right and left amygdala, the right hippocampus, and the medial occipital lobe, whereas pleasant pictures elicited significant activations in left occipital regions, and in parts of the medial temporal lobe. The direct comparison of unpleasant and pleasant pictures, which were comparable in arousal clearly indicated stronger amygdala activation in response to the unpleasant pictures. Most important, correlational analyses revealed on the one hand that the arousal of unpleasant pictures was significantly associated with activations in the right amygdala and the left caudate body. On the other hand, valence of pleasant pictures was significantly correlated with activations in the right caudate head, extending to the nucleus accumbens (NAcc) and the left dorsolateral prefrontal cortex. These findings support the notion that the amygdala is primarily involved in processing of unpleasant stimuli, particularly to more arousing unpleasant stimuli. Reward-related structures like the caudate and NAcc primarily respond to pleasant stimuli, the stronger the more positive the valence of these stimuli is