Ten experiments examined the interactions between vision and audition in stimulusdriven spatial attention orienting and inhibition of return (IOR). IOR is the demonstration that subjects are slower to respond to stimuli that are presented at a previously stimulated location. In each experiment, subjects made go/no-go responses to peripheral targets but not to central targets. On every trial, a target was preceded by a sensory event, called a "cue," either in the same modality (intramodal conditions) or in a different modality (crossmodal conditions). The cue did not predict the location of the target stimulus in any experiment. In some experiments, the cue and target modalities were fixed and different. Under these conditions, response times to a visual target were shorter when it appeared at the same location as an auditory cue than when it appeared on the opposite side of fixation, particularly at short (100 ms) cue-target stimulus onset asynchronies (Experiments 1A and IB). Similarly, response times to an auditory target were shorter when it appeared at the same location as a visual cue than when it appeared at a location on the opposite side of fixation (Experiments 2A and 2B). These crossmodal effects indicate that stimulus-driven spatial attention orienting might arise from a single supramodal brain mechanism. IOR was not observed in either crossmodal experiment indicating that it might arise from modality specific mechanisms. However, for many subjects, IOR did occur between auditory cues and visual targets (Experiments 3A and 3B) and between visual cues and auditory targets (Experiment 4A and 4B) when the target could appear in the same modality as the cue on half of the trials. Finally, the crossmodal effects of stimulus-driven spatial attention orienting on auditory and visual event-related brain potentials (ERPs) were examined in the final two experiments. Auditory cues modulated the ERPs to visual targets and visual cues modulated the ERPs to auditory targets, demonstrating that the mechanisms for spatial attention orienting cannot be completely modality specific. However, these crossmodal ERP effects were very different from each other indicating that the mechanisms for spatial attention orienting cannot be completely shared. / Arts, Faculty of / Psychology, Department of / Graduate

The motivation to eat is influenced by both internal physiological demands and by external stimuli with positive or negative associations. A conditioned stimulus (CS) associated with food can potentiate eating in sated subjects, whereas a CS associated with a negative affect can suppress eating in hungry subjects. Although the amygdala has been implicated in these behaviors, the neural mechanisms that underlie this type of non-homeostatic eating are poorly understood. To investigate the role of BLA neurons in CS+ potentiated eating and CS- lick suppression, we developed a behavioral paradigm in mice in which eating behavior could be assessed in conditions of low or high satiety and in relation to CS presentations while recording neural activity using freely-moving endoscopic calcium imaging. We found that satiety partially decreases responses to the CS+, and the neural representation of the CS+ becomes more similar to the CS-. Additionally, we tested the hypothesis that CS-evoked activity is casually involved in CS+ induced licking or CS- lick suppression by using optogenetics during this task. Silencing of BLA glutamatergic neurons labelled by NL189 prevents CS- lick suppression during low satiety and does not affect licking during the CS+. The combination of cellular imaging and optogenetics results indicates that BLA neuronal activity evoked by the CS- is critical for lick suppression, whereas CS+ activity might facilitate appetitive behavior, but this activity is not critical for cue-induced eating.