Development of Mid-level form vision
The processing of simple visual forms is limited by neural resources that lie early in the visual pathway and that mature early in development. These processes execute very quickly. More complex visual tasks engage later stages of the visual pathway that develop over an extended period of time. These processes take more time to complete.
We are tracking the development of a set of tasks that vary in complexity in order to understand how development proceeds at different levels of the visual pathway.
- Brain mechanisms underlying face and text processing
- Temporal limits on simple and complex visual tasks during normal visual development
The pattern of optic flow on the retina provides us with a rich source of information about the layout of the environment and our movements through it. We are using EEG, fMRI and psychophysics to study how the brain analyses motion cues.
- Adaptive spatio-temporal integration of local and global motion cues
- Long-range motion processing
- Bi-stable motion perception and its neural bases
Stereopsis and 3-D vision
The fact that we have two laterally displaced eyes provides us with a very informative cue for depth known as horizontal disparity. Sensitivity to this cue develops under the influence of the visual environment and abnormal visual experience during early life disrupts binocularity and the perception of depth.
- Brain basis of motion-in-depth perception based on changing disparity and inter-ocular velocity differences
- Binocular cues for vergence eye movements
- Neural basis of the immersive experience in virtual environments and video display quality
Selecting the appropriate action to take among potentially conflicting alternatives involves sensory processing, selective attention, decision-making, response planning and response execution. These processes, collectively referred to as “perceptual decision” unfold over time and across many cortical areas.
- Brain bases of perceptual decisions about subtle differences in shape
- Brain bases of perceptual decisions about subtle differences in depth
- Effects of visual deprivation during childhood on decision processes
Regulation of visual/cortical excitability
The range of image variation that occurs under natural viewing conditions is very large. To cope with this variability, the visual system has evolved a set of regulatory mechanisms that optimize sensitivity for prevailing viewing conditions. This regulation process relies on a set of very elementary neural mechanisms that are arranged in a similar fashion at multiple levels of processing. Disruptions of these elementary mechanisms may occur in brain disorders, such as epilepsy and autism. Studies of sensitivity regulation may provide useful biomarkers for these disorders and failures of these regulatory processes may contribute to symptomatology.
- Visual sensitivity regulation in epilepsy
- Visual sensitivity regulation in Austism Spectrum Disorders
EEG EEG/fMRI methods development
Many labs, including ours, are pursuing methods for exploiting the temporal resolution of the EEG to study the dynamics of brain processing and the spatial resolution of fMRI to determine where in the brain these processes are situated. Our work centers on non-linear analysis methods for studying dynamics, EEG source-localization methods based on inverse modeling procedures and simultaneous EEG/fMRI integration.
- Computational methods for nonlinear analysis in the time-domain via Volterra kernels
- Application of sparse-priors and fMRI constraints for inverse modeling
- Simultaneous EEG/fMRI using frequency tagging methods