Brain Correlates of Visual Processing of Emotional Scenes in ACTion and EMOtional Judgments During Normal VIeillissement

It is accepted that emotional events engage more attention and are detected and identified faster than neutral. The same is true for negative events compared to positive events. On the cerebral level, this facilitation results in greater activation of brain regions involved in visual and emotional processing. In normal aging, the preference for the negative stimuli (named negativity bias) tends to disappear and, sometimes, to shifts towards a preference for positive stimuli compared to both the negative and neutral stimuli (positivity bias), which could be mainly related to a decrease with age in processing of negative stimuli and in attention to this type of information. Only a few studies rather suggest an improvement in processing of positive stimuli with age. On the cerebral level, various fMRI studies mainly highlight an age effect on processing of negative stimuli in several brain regions involved in emotional processing such as amygdalae and prefrontal cortex (respectively a lower and higher activity in older adults compared to young adults). This age effect also induces a higher level of well-being and less frequent negative emotional feelings in the elderly than in younger people. Most studies have assessed the age effect on emotional processing using tasks which require the identification of a personal emotional experience or the emotions of others. Although many studies suggest a strong link between emotion and action, relatively little is known about the age effect on emotional processing when the task requires the identification of a tendency-to-action (i.e. preparation of the individual to react and direction of action - example: fear prepares to avoid danger). Team's works on this research question show the negativity bias with age is preserved in a tendency-to-action appraisal task while it disappears with age in an emotional appraisal task, suggesting a dissociation between emotion and tendency to action. In addition, a pilot fMRI study by our team in young people show the tendency-to-action appraisal task compared to emotional appraisal task induces higher activation in brain regions involved in visual and emotional processing. To our knowledge, no study has yet investigated the evolution with aging of neural circuitry involved in emotional processing during a tendency-to-action appraisal task compared to an emotional apparaisal task. Studying this evolution could allow to better understand the observed dissociation with increasing age between emotional and tendency-to-action tasks and more generally to better understand the evolution of the interactions between emotional and action processes with aging.

ACTEMOVI project aims to identify the brain bases and neural networks involved in the processing of emotional visual information in normal aging when performing emotional appraisal and action-oriented tasks, through a functional MRI study and using an original mathematical modeling of functional connectivity based on the Graph theroy developed in the team. Findings will be used to develop a first neural network mapping model involved in visual perception of emotional scenes during emotional and tendency-to-action appraisals during normal aging.

The experiment will be conducted in two age groups (20-35 and 60-85 years old) of 50 healthy participants each (number based on currently requirements in terms of size of effects for the envisaged connectivity analyzes), and carried out using a whole-body 3-T Philips scanner (Philips Medical Systems, Best, NL).

Participants will perform two appraisal tasks during viewing a succession of emotional scenes, one emotional based on the appraisal of personal emotional experience (pleasant, unpleasant or neutral), and the other based on the appraisal of the tendency-to-action (approach, avoidance or no action). Two characteristics of stimuli will be manipulated in the study : valence and arousal.The age effect is modulated by these two characteristics.

For each task, stimuli will be organized into two blocks: "High" block containing pleasant and unpleasant stimuli of high activation and neutral stimuli, and "Low" block including unpleasant and pleasant stimuli of low activation and neutral stimuli. The tendency-to-action induced by stimuli will be congruent with the valence of stimuli (i.e. pleasant/approach, unpleasant/avoidance and neutral/no action). The emotional stimuli in each block will be displayed according to a block fMRI paradigm.

In total, each participant will successively perform four experimental blocks. Two blocks will involve an emotional task (for the high and low blocks) and the other two will involve a tendency-to-action task (for the high and low blocks).The order of tasks and images within a task will be counterbalanced between the participants

For fMRI analyses, the protocol will aso include an anatomical MRI, a Diffusion Tension Imaging (DTI) and a resting-state measure in order to take into account the anatomical and functional differences between age groups. fMRI data (MRI signal of the BOLD type - Blood Oxygen Level Dependent) will be analyzed using standard neuroimaging analysis software (e.g. SPM, FSL). Analysis will perform on whole-body and in regions of interest (ROIs, e.g. amygdala). Regions of interest (ROIs) associated with emotional processing will be functionally identified and delimited for each participant using a separate functional localizer experiment adapted from Vuilleumier et al. (2003). These regions will also be used for Resting-State network analysis.