To better understand the cortical mechanisms mediating perception and memory, we have been examining the functional areas that comprise visual association cortex in nonhuman primates and explored their interconnections by the use of neuroanatomical tracing techniques in combination with physiological recording of neural activity. Our results indicate that a multiplicity of separate visual areas lie beyond the primary visual cortex in the stream of information processing. These areas form two hierarchically organized and functionally specialized cortical pathways: an occipitotemporal pathway, or ventral stream, for the identification of objects, and an occipitoparietal pathway, or dorsal stream, for the appreciation of the spatial relationships among objects and the visual guidance of movement towards them. Whereas neurons in the areas along the pathway into the temporal lobe process the visual features objects, such as color and form, those in areas along the pathway into the parietal lobe process the visuospatial attributes of objects, such as their direction of motion. Not only are the two processing pathways anatomically and functionally distinct, but they can also be differentiated by their neurochemical profiles. Whereas the vast majority of neurons within the occipitoparietal pathway contain neurofilament protein, this is true for less than half the neurons within the occipitotemporal pathway. In an attempt to identify homologies between the human and monkey brains, we have begun investigations of human subjects using functional brain imaging and of human brain tissue using the same immunohistological staining techniques that we have used on monkey brain tissue. Thus far in our brain imaging studies, we have localized the two visual processing pathways within the human brain, investigated functional specialization of visual attributes within them, and identified their further extensions for working memory in the prefrontal cortex. Additionally, we have demonstrated that the learning and retention of simple skills, both perceptual and motor, involves neural mechanisms located at very early stages of cortical processing, namely, the primary visual and motor cortex. In our work with human brain tissue, we have successfully identified several cortical areas in the human brain that have been described in the monkey brain, including visual areas V2, V3 and MT. Future studies will pursue functional brain imaging studies of perception and memory in humans and parallel single- cell recording studies in awake, behaving monkeys. A major effort will be to determine how top- down influences of attention and memory affect perceptual processing. - visual cognition, brain imaging, cerebral cortex, perception, memory, motor learning - Human Subjects
| Tootell, Roger B H; Devaney, Kathryn J; Young, Jeremy C et al. (2008) fMRI mapping of a morphed continuum of 3D shapes within inferior temporal cortex. Proc Natl Acad Sci U S A 105:3605-9 |
| Hadj-Bouziane, Fadila; Bell, Andrew H; Knusten, Tamara A et al. (2008) Perception of emotional expressions is independent of face selectivity in monkey inferior temporal cortex. Proc Natl Acad Sci U S A 105:5591-6 |
| Heekeren, Hauke R; Marrett, Sean; Ungerleider, Leslie G (2008) The neural systems that mediate human perceptual decision making. Nat Rev Neurosci 9:467-79 |
| Ungerleider, Leslie G; Galkin, Thelma W; Desimone, Robert et al. (2008) Cortical connections of area V4 in the macaque. Cereb Cortex 18:477-99 |
| Siman-Tov, Tali; Mendelsohn, Avi; Schonberg, Tom et al. (2007) Bihemispheric leftward bias in a visuospatial attention-related network. J Neurosci 27:11271-8 |
| Rossi, Andrew F; Bichot, Narcisse P; Desimone, Robert et al. (2007) Top down attentional deficits in macaques with lesions of lateral prefrontal cortex. J Neurosci 27:11306-14 |
| Mukai, Ikuko; Kim, David; Fukunaga, Masaki et al. (2007) Activations in visual and attention-related areas predict and correlate with the degree of perceptual learning. J Neurosci 27:11401-11 |
| Pessoa, Luiz; Japee, Shruti; Sturman, David et al. (2006) Target visibility and visual awareness modulate amygdala responses to fearful faces. Cereb Cortex 16:366-75 |
| Heekeren, H R; Marrett, S; Ruff, D A et al. (2006) Involvement of human left dorsolateral prefrontal cortex in perceptual decision making is independent of response modality. Proc Natl Acad Sci U S A 103:10023-8 |
| Pessoa, Luiz; Japee, Shruti; Ungerleider, Leslie G (2005) Visual awareness and the detection of fearful faces. Emotion 5:243-7 |
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