Projects

        1. Motion integration and segmentation within and across apertures

        Work done in collaboration with Stephen Grossberg and Ennio Mingolla

        A neural model is developed of how motion integration and segmentation processes both within and across apertures compute global motion percepts. Figure-ground properties, such as occlusion, influence which motion signals determine the percept. For visible apertures, a line's extrinsic terminators do not specify true line motion. For invisible apertures, a line's intrinsic terminators create veridical feature tracking signals. Sparse feature tracking signals can be amplified by directional filtering and competition, then integrated with ambiguous motion signals from line interiors, to determine the global percept. Filtered motion signals activate directional grouping and priming cells, which compete across space to select a winning direction, then feed back to boost consistent long-range filter activities and suppress inconsistent activities. Feedback can also attentionally prime a movement direction. This feedback process is predicted to occur between cortical areas MT and MST. Computer simulations include the barberpole illusion, motion capture, the spotted barberpole, the triple barberpole, the occluded translating square illusion, motion transparency and the chopsticks illusion.
         

        2. Attention in depth: Effects of depth cues on multi-element visual tracking

        Work done in collaboration with Ennio Mingolla

        Human observers can track up to five moving targets in a display with ten identical elements (Pylyshyn and Storm, 1988; Yantis, 1992). Previous experiments manipulated element trajectories to prevent intersections of element boundaries, evidently in the belief that transient overlaps among homogeneous elements make the task too hard. We examine whether depth cues such as occlusion (T-junctions) and disparity affect performance in a tracking task when element boundaries, as projected onto the two-dimensional plane of the monitor screen, are allowed to intersect. We are also studying the effects of restricting element trajectories to surfaces, i.e., is attention automatically bound to surfaces or can top-down signals be used to overcome this attentional bias?
         

        Publications

        TECHNICAL REPORTS

        • Grossberg, S., Mingolla, E. and Viswanathan, L. (2000) Neural Dynamics of Motion Integration and Segmentation Within and Across Apertures. Technical Report CAS/CNS-2000-004.

          • Authorship in alphabetical order.
          Click here to download the PDF document (4.9M)
           
        • Viswanathan, L. and Mingolla, E. (1999) Dynamics of attention in depth: Evidence from multi-element tracking. Technical Report CAS/CNS-TR-99-010. To appear in Perception.

          • Click here to download the PDF document (195K)
           
        • Viswanathan, L. and Mingolla, E. (1998) Attention in depth: Disparity and occlusion cues facilitate multi-element visual tracking. Technical Report CAS/CNS-TR-98-012.

          • Click here to download the PDF document (105K)

        CONFERENCE PROCEEDINGS

        • Viswanathan, L., Grossberg, S. and Mingolla, E. (1999) Neural dynamics of motion grouping across apertures. Third International Conference on Cognitive and Neural Systems. [May 26-29, 1999; Boston, MA, USA]

          • Click here to download the abstract in PDF (8K)
          Click here to download the poster in PDF (282K)
          Click here to download the handout in PDF (125K)
           
        • Viswanathan, L., Grossberg, S. and Mingolla, E. (1999) Neural dynamics of motion grouping across apertures. Investigative Ophthalmology & Visual Science, 40, in press. [ARVO, May 9-14, 1999; Ft. Lauderdale, Florida, USA]

          • Click here to download the abstract in PDF (9K)
          Click here to download the poster in PDF (282K)
          Click here to download the handout in PDF (125K)
           
        • Viswanathan, L. and Mingolla, E. (1999) Attention in depth: Multi-element tracking across different depths is easier than across different colors. Cognitive Neuroscience Society abstract, in press. [Cognitive Neuroscience, April 1999; Washington DC, USA]

          • Click here for the text of the abstract
          Click here to download the poster in PDF (164K)
           
        • Viswanathan, L. and Mingolla, E. (1998) Disparity and occlusion cues facilitate multi-element visual tracking. Investigative Ophthalmology & Visual Science, 39(4), pp S634. [ARVO 1998; Ft. Lauderdale, Florida, USA]

          • Click here to download the abstract in PDF (15K)
          Click here to download the poster in PDF (118K)

        Teaching Experience

          Teaching Assistant for  CN 530 - Neural and Computational Models of Vision (Spring 1998) , a first-year graduate level course. I gave two lectures as guest lecturer:
          • Motion Perception I:       PDF document (100K)
          • Motion Perception II:      PDF document (191K)


          Guest Lecture for CN 530 - Neural and Computational Models of Vision (Spring 1999)

          • Motion Perception:      PDF document (235K)

        Computer Graphics and Image Processing work

        Advanced Computer Graphics (CS 580, Fall 1997) Programming Assignments

        •  P0: Kochanek-Bartels Spline Editor
        •  P1: Spline-based Keyframe Animation Tool
        •  P2: Physically-based Particle Animation Tool
        •  P3: Constraint-based Animation Tool
        •  P4: Procedural Texture Mapping
        •  P5: Volume Rendering (Marching Cubes Algorithm)

        Image and Video Computing (CS 585, Fall 1998) Programming Assignments

        •  P1: Binary Image Analysis (Optical Character Recognition)
        •  P2: Eigenfaces and Gaussian Pyramids
        •  P3: Active Contour Models
        •  P4: Image Mosaics

         

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