Human neural systems that mediate visual perception, attention, and memory were investigated in the intact brain with functional brain imaging. Functional magnetic resonance imaging (fMRI) was used to measure precisely localized hemodynamic changes associated with the performance of selected visual perceptual and mnemonic tasks. These hemodynamic changes are indices of local changes in neural activity. Human extrastriate visual cortex, like that of the macaque monkey, is organized into a ventral object vision stream and a dorsal spatial vision stream. The ventral object vision pathway was found to have a functional architecture that produces different patterns of response for faces and different categories of objects, such as houses, chairs, animals, and tools. These category-related patterns of response are remarkably consistent across subjects. Face perception was found to involve both the ventral temporal cortex, which is more involved in the representation of face identity, and the superior temporal sulcus, which is more involved in the representation of changeable aspects of the facial configuration that are important for social communincation, such as expression and eye gaze direction. The complete object and spatial visual processing streams, including posterior extrastriate and prefrontal projections, participate in object and spatial visual working memory. Different prefrontal areas were associated with object and spatial visual working memory. Spatial working memory activated a region in the superior frontal sulcus just anterior to the human frontal eye field. Three, anatomically and functionally distinct prefrontal regions in the middle and inferior frontal gyri were identified that participate in object working memory. Event-related fMRI was used to distinguish complementary mechanisms for tracking items in working memory - one for tracking repetitions of items to facilitate ignoring distracters and one for tracking the target of a working memory search.
| Ishai, Alumit; Haxby, James V; Ungerleider, Leslie G (2002) Visual imagery of famous faces: effects of memory and attention revealed by fMRI. Neuroimage 17:1729-41 |
