Please enable javascript to view this page in its intended format.

Queen's University
 

Visual Neurophysiology

A main focus of our lab is to investigate the functions of the visual system by using various animal models. Our research includes analyzing the responses of cells in the pigeon optic tectum, Nucleus Rotundus and various other visual nuclei. Using Silicon Graphics workstations (Octane) we are able to create many visual stimuli which we can move in 2D or 3D trajectories. These stimuli are presented on a tangent screen and a Spike2 program running on a Pentium4 Computer controls the presentation of stimuli. The collection of data (neuronal impulses) with millisecond resolution are recorded on the PC using Spike2. Using these procedures we have discovered neurons that are specialized for processing object motion, colour, motion of objects in 3D space, time to collision, etc. Other visual pathways have been studied which appear to be processing self-induced optic flow.


Time to Collision

 We have found neurons in the pigeon Nucleus Rotundus which are highly selective for objects which are going to collide with the animal and the cells appear to calculate the time to collision.

 

  • Wang, Y.C. and Frost, B.J. Some neurons in the nucleus rotundus of pigeon compute time to collision. Society for Neuroscience Abstract, 1991, 17, 1380. [Poster presentation in PDF]

  • Wang, Y. and Frost, B.J. "Time to collision" is signalled by neurons in the nucleus rotundus of pigeons. Nature, 1992, 356, 236-238. (Written up in Current Biology, 1992, 2, 371-372). [Abstract]
nntc
  • Wang, Y., Jiang, S. andFrost, B.J. Visual processing in pigeon nucleus rotundus: luminance, colour, motion and looming subdivisions. Visual Neuroscience, 1993, 10, 21-31. [Abstract]

  • Sun, H.-J. and Frost, B.J. Responses of time-to-collision neurons in the nucleus rotundus of pigeons to accelerating and decelerating stimuli. Society for Neuroscience Abstract, 1997, 23, 453. [Poster presentation in PDF]

  • Frost, B. J. and Sun, H.-J. Responses of looming detectors in the nucleus rotundus of pigeon. Association for Research in Vision and Ophthalmology Abstract, 1997. [Poster presentation in PDF]

  • Sun, H.-J. and Frost, B.J. Computation of different optical velocities of looming objects. Nature Neuroscience, 1998, 1(4), 296-303. [Abstract]



Objects and Holes

We are also studying the motion cues for determining figure ground relationships of objects. We have found cells that respond specifically to textured objects moving "in front" of textured backgrounds, but do not respond to "holes" or apertures in textured fields. These cells seem to be responding to moving "occlusion" edges and not disocclusion edges.

 

  • Frost, B.J., Wang, Y-C. and Jiang, S-Y. Leading edge occlusion specificity in tectal and n. isthmi cells in the pigeon. ARVO Abstracts, 30, 300, 1989. [Poster presentation in PDF]
  • Wang, Y.C. and Frost, B.J. Functional organization in the nucleus rotundus of pigeon. Society for Neuroscience Abstract, 1990, 16, 1314. [Poster presentation in PDF]
  • Frost, B.J. Subcortical Analysis of Visual Motion: Relative motion, figure-ground discrimination and self-induced optic flow. In F.A. Miles, and J. Wallman (Eds.). Visual Motion and its role in the Stabilisation of Gaze. Elsevier, Amsterdam, 1993, 159-175.
  • Frost, B.J. and Sun, H.J. Visual motion processing for figure/ground segregation, collision avoidance, and optic flow analysis in the pigeon. Chapter 5. In: M.V. Srinivasan and K. Venkatesh (eds.) From Living Eyes to Seeing Machines, Oxford University Press, London, 1997, 80-103.


    Motion Integration over long distances

    Another area of interest in our lab is on the differences between long range excitatory and inhibitory interactions between neurons which code motion. We are curently involved in examining these issues in the object motion pathway as well as the self motion pathway in the pigeon. These experiments relate to our human psychophysics experiments on motion capture and vection (see below) and also to our work on Virtual Reality.

     

    Sun, H.-J. and Frost, B.J. Motion processing in pigeon tectum: Equiluminant chromatic mechanisms. Experimental Brain Research, 1997, 116, 434-444. [Abstract]

     


     

     

    Human Vection: Ambiguous cues to vection

    We study the perception of self motion in humans using a Vection booth. An Amiga 3000 computer is used to generate animated whole field motion patterns which are projected on two adjacent corner wall-screens of a darkened cubical booth. With the presentation of appropriate visual stimuli the subjects achieve the overwhelming sensation that they are in an elevator moving up or down. We have investigated the relationship between the depth of the stimuli presented and the self motion sensations. We have also examined the effects of ambiguous vection stimuli on the phenomenon. We presented visual patterns with an equal amount of up and down motion with either no spatial separation (transparent) or within a checkerboard pattern with alternating up and down motion squares. Subjects still experienced vection despite the absence of a net motion signal. Furthermore the subjects experienced a profound kinetic depth effect which appeared to determine the direction of vection. The kinetic depth effect was bistable with the set of up dots becoming the background for a period and then the set of down dots becoming the background. With each flip of depth there was a corresponding flip in the direction of vection.

     

    • Telford, L., Spratley, J. and Frost, B.J. The role of kinetic depth cues in the production of linear vection in the central visual field. Perception, 1992, 21, 337-349. [Abstract]
    • Telford, L. and Frost, B.J. Factors affecting the onset and magnitude of linear vection. Perception and Psychophysics, 1993, 53, 682-692. [Abstract]
    • Marlin, S.G., Feldman, R. and Frost, B.J. Ambiguous foreground/background motion cues and vection. Association for Research in Vision and Ophthalmology Abstracts, 1994, 35:1276.


    Animal Vection

    We are studying the behavioural responses of animals (Pigeons and Locusts) to various speeds of whole field motion patterns. Translocational visual flow fields can produce head bobbing in pigeons and flight in tethered locusts.

     

    Pigeon Bobbing Pigeon Landing

    • Troje, N. and Frost, B.J. Head-bobbing in pigeons: How stable is the hold phase? Journal of Experimental Biology, 2000, 203:935-940. (Written up in New Scientist, 165(2227):23). [Abstract]
    • Troje, N.F. and Frost, B.J. The physiological fine structure of motion sensitive neurons in the pigeon's tectum opticum. Society for Neuroscience Abstract, 1998. [Poster presentation in PDF]

    Kingston, Ontario, Canada. K7L 3N6. 613.533.2000