Phantom contours: A new class of visual patterns that selectively activates the magnocellular pathway in man

The visual system of primates has two anatomical pathways: magno (M) and parvo (P). Here we report a novel technique for selectively stimulating the magnocellular pathway in man. The stimulus was a texture border between black spots and white spots displayed on a uniform gray field. This stimulus (Frame 1) was followed by Frame 2, in which all the black spots were replaced with white spots and all the white spots with black. The procedure was repeated in a continuous cycle; that is, spots reversed polarity without changing positions. At high temporal frequencies (20 Hz), subjects could not see the difference between the flickering spots, but could see a phantom contour separating the two indiscriminable regions. The difference between the spots themselves could be discriminated only at about 17 Hz. Since the M pathway can follow high flicker rates but is insensitive to the sign of the border, we suggest that the phantom border is seen exclusively by the M system. The P system, on the other hand, can report the sign of the border, but only at low flicker rates. Phantom contours provide a psychophysical scalpel for producing a temporary “lesion” in the par-vocellular pathway of intact human subjects. One could therefore repeat all of classical psychophysics and physiology using phantom contours to determine whether or not a given visual process receives an M input. Also, these stimuli might provide a simple diagnostic test for revealing the loss of M-cell function that occurs in early glaucoma.

[1]  D. C. Essen,et al.  Visual areas of the mammalian cerebral cortex. , 1979 .

[2]  Nikos K Logothetis,et al.  The color-opponent and broad-band channels of the primate visual system , 1990, Trends in Neurosciences.

[3]  S. Zeki.  Functional specialisation in the visual cortex of the rhesus monkey , 1978, Nature.

[4]  Vilayanur S. Ramachandran,et al.  Theories of Perception. , 1951 .

[5]  V. Ramachandran,et al.  Apparent movement with subjective contours. , 1973, Vision research.

[6]  P. Gouras,et al.  Spatial summation, response pattern and conduction velocity of ganglion cells of the rhesus monkey retina , 1976, Vision Research.

[7]  V. S. RAMACHANDRAN,et al.  Does colour provide an input to human motion perception? , 1978, Nature.

[8]  P. Gouras.  Identification of cone mechanisms in monkey ganglion cells , 1968, The Journal of physiology.

[9]  P. Lennie,et al.  Spatial and temporal contrast sensitivities of neurones in lateral geniculate nucleus of macaque. , 1984, The Journal of physiology.

[10]  D. Hubel,et al.  Spatial and chromatic interactions in the lateral geniculate body of the rhesus monkey. , 1966, Journal of neurophysiology.

[11]  R. W. Rodieck,et al.  Identification, classification and anatomical segregation of cells with X‐like and Y‐like properties in the lateral geniculate nucleus of old‐world primates. , 1976, The Journal of physiology.

[12]  William H. Merigan,et al.  Spatio-temporal vision of macaques with severe loss of Pβ retinal ganglion cells , 1986, Vision Research.

[13]  O. Braddick.  A short-range process in apparent motion. , 1974, Vision research.

[14]  R. M. Boynton.  Human color vision , 1979 .

[15]  V S Ramachandran,et al.  Perceiving shape from shading. , 1988, Scientific American.

[16]  C. Blakemore,et al.  Lateral Inhibition between Orientation Detectors in the Human Visual System , 1970, Nature.

[17]  P. Cavanagh,et al.  Perception of Motion in Equiluminous Kinematograms , 1985, Perception.

[18]  W. Green,et al.  Optic nerve damage in human glaucoma. III. Quantitative correlation of nerve fiber loss and visual field defect in glaucoma, ischemic neuropathy, papilledema, and toxic neuropathy. , 1982, Archives of ophthalmology.

[19]  T. Troscianko,et al.  AI and the eye , 1990 .

[20]  DH Hubel,et al.  Psychophysical evidence for separate channels for the perception of form, color, movement, and depth , 1987, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[21]  J Allman,et al.  Direction- and Velocity-Specific Responses from beyond the Classical Receptive Field in the Middle Temporal Visual Area (MT) , 1985, Perception.

[22]  2-D or not 2-D-that is the question , 1989 .