| Despite recent unprecedented progress in the cognitive neuroscience of emotion, a number of unsolved issues still remain. Among them, the temporal and spatial correlates of two types of emotional processing captured my attention: (1) the perception and categorization of emotional stimuli ( emotional evaluation), and (2) the memory-enhancing effect of emotion (emotional memory). Two fundamental affective dimensions are of particular interest in the study of emotion: emotional arousal and emotional valence. Arousal refers to a continuum that varies from calm to excitement, whereas valence refers to a continuum that varies from positive to negative with neutral in the middle. In the present research, issues concerning the effect of arousal and valence on the neural correlates underlying emotional evaluation and emotional episodic memory were addressed using functional neuroimaging tools that allow both temporal (event-related potentials: ERPs) and spatial (functional magnetic resonance imaging: fMRI) measurements. The present dissertation covers the results of three studies. The first two studies (one ERP and one fMRI) focused on encoding processes to identify the effect of arousal and valence on the neural correlates of emotional evaluation and successful emotional encoding. The third study used fMRI and focused on retrieval processes to identify the effect of emotion on the neural mechanisms involved during successful retrieval of consolidated emotional memories. The main findings of these studies were that, while the neural correlates of emotional evaluation were sensitive to both arousal and valence, the neural mechanisms of emotional memory (during both encoding and retrieval) were mainly sensitive to arousal. The encoding studies also found clear evidence concerning the timing (faster emotional encoding), and location (e.g., medial-temporal lobe: MTL) of the mechanisms underlying the memory-enhancing effect of emotion. The retrieval study revealed that similar MTL mechanisms were also involved during retrieval, and that activity in specific MTL subregions was sensitive to the degree of recollection associated with successful retrieval of remote emotional memories. Taken together, the present research brings novel evidence concerning the effect of emotion on the neural mechanisms underlying various aspects of emotional processing, from initial perception and evaluation to successful encoding and, later, successful retrieval of emotional memories. |
