Distinct parietal sites mediate the influences of mood, arousal, and their interaction on human recognition memory

The two dimensions of emotion, mood valence and arousal, have independent effects on recognition memory. At present, however, it is not clear how those effects are reflected in the human brain. Previous research in this area has generally dealt with memory for emotionally valenced or arousing stimuli but the manner in which interacting mood and arousal states modulate responses in memory substrates remains poorly understood. We investigated memory for emotionally neutral items while independently manipulating mood valence and arousal state by means of music exposure. There were four emotional conditions: positive mood/high arousal, positive mood/low arousal, negative mood/high arousal and negative mood/low arousal. We observed distinct effects of mood valence and arousal in parietal substrates of recognition memory. Positive mood increased activity in ventral posterior parietal cortex (PPC) and orbitofrontal cortex, while arousal condition modulated activity in dorsal PPC and the posterior cingulate. An interaction between valence and arousal was observed in left ventral PPC, notably in a distinct parietal area from the main effects, with a stronger effect of mood on recognition memory responses here under conditions of relative high vs. low arousal. We interpret the PPC activations in terms of the attention to memory hypothesis: increased arousal may lead to increased top-down control of memory, and hence dorsal PPC activation, while positive mood valence may result in increased activity in ventral PPC regions associated with bottom-up attention to memory. The findings indicate that distinct parietal sites mediate the influence of mood, arousal and their interplay during recognition memory.