The goal of the Section on Neurocircuitry has long been devoted to establishing the links between neural structure and cognitive function, especially in the visual modality. Most of Dr. Ungerleider’s early work was devoted to anatomical tracing techniques in macaque monkeys in order to delineate the areas that comprise visual association cortex and their interconnections. The mappings of the monkey extrastriate visual cortex in the mid-1990’s outlined some of the major functional systems. With the advent of functional brain imaging in humans, Dr. Ungerleider re-channeled her resources towards studies of human cortex, first using PET and then fMRI. Her monkey work has guided many of her hypotheses in human imaging studies.
Dr. Ungerleider’s work on visual attention and perception has shown that in a typical scene many different objects compete for neural representation due to the limited processing capacity of the visual system. The competition among multiple objects can be biased by both bottom-up sensory-driven mechanisms and top-down influences, such as selective attention. Although the competition among stimuli for representation is ultimately resolved within visual cortex, the source of top-down biasing signals likely derives from a distributed network of areas in frontal and parietal cortex. This biased competition model of attention suggests that once attentional resources are depleted, no further processing is possible. Dr. Ungerleider's recent work has shown that, similar to the processing of other stimulus categories, the processing of stimuli with emotional valence is under top-down control, requiring attentional resources.