Abstract
The ability to use prior information to enhance the processing of visual stimuli at a specific location is critical for quickly sorting through the myriad of incoming stimuli and making decisions regarding future actions. This selection process, known as visual attention, appears to be fundamental to our ability to navigate and interact with the environment, and accordingly has been the focus of innumerable psychological and neurobiological studies (Pashler, 1998). While the overall framework and principles underlying the neurobiology of attention are fairly consistent for humans and monkeys, the lack of a direct means of comparing the human fMRI and macaque electrophysiology data has left many uncertainties about the processes underlying visual attention in the two species. Two macaques monitored one of two peripheral rapid serial visual presentation (RSVP) streams for the appearance of a specific target object in a stream of difficult-to-discriminate distracter objects. By using functional magnetic resonance imaging (fMRI) blood oxygen level dependent (BOLD) signals, we assessed the level of neural activity across the entire cortex. To measure attentional modulations of stimulus-evoked activity in the whole brain we compared BOLD signals to one stream of stimuli when it was attended as compared to when it was unattended. The results of this study define the distributed network of visual processing areas involved in visuospatial attention. Additionally, the magnitude of the activity in the visual processing areas was modulated by the locus of attention. Modulation of the BOLD signals by attention matched those observed in previous human and macaque studies; furthermore, the differences in these magnitudes across the network of areas may indicate differences in the roles each of these areas play in visual attention. Lastly, we found support for potential differences between humans and macaques in the effect of attention on early visual areas; therefore, caution is needed in applying macaque data to human models of visual attention.
