| | Principal Investigators
| David A. Leopold, Ph.D. |
 |
 |
Dr.
Leopold attained a B.S. in biomedical engineering from
Duke University in 1991. He subsequently received his
Ph.D. from Baylor College of Medicine in 1997, where he
studied neurophysiological mechanisms of multistable perception
in the laboratory of Nikos Logothetis. He then joined
the new laboratory of Prof. Logothetis at the Max Planck
Institute for Biological Cybernetics in Tübingen,
Germany, where he worked as a Research Scientist on topics
related to subjective perception and face recognition.
There he also conducted investigations in the resting
brain using combined fMRI and electrophysiological techniques.
Dr. Leopold arrived at the NIH in the beginning of 2004
to establish the Unit on Cognitive
Neurophysiology and Imaging and to head the Primate
Imaging Core Facility. |
| Research Interests |
| Our visual impression of the world arises as the brain registers and interprets images falling on the retinae. Dr. Leopold’s lab is interested in the large-scale organization of brain activity related to the establishment and maintenance of a visual percept. It is well known that neurons in different cortical areas respond to simple and complex visual features, and it is thought that the neural analysis of a stimulus proceeds in a hierarchical fashion. Yet, these notions provide little insight into the nature of perception, which has simultaneous access to simple features (e.g. color and brightness), intermediate ones (e.g. shape and geometric arrangement), and semantic qualities (e.g. identity and meaning), suggesting that it cannot be easily localized. In previous work, they demonstrated that the responses of a subset of cortical neurons were modulated according to the subjective appearance of ambiguous patterns. Studies from other groups have provided additional clues about the nature of this modulation, with some evidence pointing to recurrent activation within the visual cortex, and other evidence suggesting intervention by external structures. Based on these and other observations, they hypothesize that the neural expression of a visual percept is intimately linked to dynamic, interactive processes among diverse brain areas, and that this is only partially reflected in the responses of feature-selective sensory neurons. Present research aims to investigate the nature of this interplay using combined neurophysiological and functional MRI techniques. |
| Representative Selected Recent Publications: |
- Leopold DA, Rhodes G, Mueller K-M, Jeffrey L:
The dynamics of visual adaptation to faces.
Proceedings of the Royal Society, Series B, 272: 897-904, 2005. (View PDF)
- Wilke, M., Logothetis, N.K., and Leopold, D.A.: Generalized
flash suppression of salient visual targets Neuron,
39, 1043-1052, 2003. (View PDF)
- Leopold, D.A., Murayama, Y. and Logothetis, N.K.: Very slow activity
fluctuations in monkey visual cortex: implications
for functional imaging. Cerebral Cortex 13(4), 422-33, 2003. (View PDF)
- Leopold, D.A., Wilke, M., Maier, A., and Logothetis, N.K.:
Stable perception of visually ambiguous patterns.
Nature Neuroscience 5, 605-609, 2002. (View PDF)
- Leopold, D.A., O’Toole, A.J., Vetter T., and Blanz, V.:
Prototype-referenced shape encoding revealed by high-level aftereffects.
Nature Neuroscience, 4: 89-94, 2001. (View PDF)
- Leopold DA, Logothetis NK:
Multistable phenomena: changing views in perception.
Trends in Cognitive Sciences, 3: 254-264, 1999. (View PDF)
|
|
|
|
|
