M Cell

(See Ganglion Cell).

 

M Cones

Medium wavelength sensitive cones (green). Are most sensitive to a wavelength of approximately 531nm. (See also L Cones and S Cones).

 

Mach Bands

(Mach 1865)

Bright and dark lines that appear near the brighter and darker borders of a blurred edge between two uniform regions of different luminance. Luminance ramps which are too steep or too shallow do not create mach bands.

Macula Lutea

The cone rich area of the human eye that contains the fovea

 

Magnification Factor

Magnocellular Pathway

Pathway that begins with the parasol (magno) ganglion cells in the retina and terminates within the magnocellular layer of the LGN. Has a high contrast gain than Parvocellular Pathway. (See also Parvocellular Pathway and Ganglion Cell).

 

McCullough Effect

Melanin

Black pigment in the pigment epithelium cells that absorbs light not captured by the retina preventing it from being reflected off the back of the eye.

(See also Pigment Epithelium).

 

Membranous Discs

Located in outer segments of photoreceptors

 

Mesopic

Intensities of light under which both rods and cones operate. (See also Photopic and Scotopic).

 

Metameric Stimuli

Two stimuli which despite their physical differences are perceptually indistinguishable.

 

Microspectrophotometry (MSP)

A procedure that involves the passage of a narrow measuring beam through the outer segments of individual photoreceptors to measure absorbance spectra in excised retinas.

Middle Temporal Area

(See Appendix I: Cortical Areas).

 

Midget Ganglion Cell

(See Ganglion Cell).

 

Modal

Perceptually salient, having a real phenomenological presence. (As opposed to Amodal).

 

Modulation Transfer Function

A plot of the ratio of image contrast to target contrast at different spacial frequencies

 

Mondrian Stimulus

Consists of a Mosaic of rectangular shapes of (usually) black, grey and white.

 

Monochromat

An individual with only one spectral channel (i.e. retina receptors have the same spectral sensitivity).

Monocular Depth Cues

Relative size, texture gradients, perspective, shadow, height of retina image, interposition, motion parallax.

 

Monocular Zone

The areas of the visual field from which light projects only to one of the eyes. (See also Binocular Zone).

 

Monoptic Stimulation

When only one eye views an image (the other eye being closed or occluded). (See also Binoptic Stimulation and Dichoptic Stimulation).

 

Morphology (of a neuron)

The form and structure of a neuron including its dendritic field, cell body and axonal projections.

 

Motion Capture

Occurs when features (such as random dot patterns) with no net motion of their own appear to move in sychrony with other salient moving features.

 

Motion Parallax

Movement of the image of an object over the retina. The rate of movement depends upon the velocity of the object relative to the eye and its distance from the eye.

 

Motor Fusion

Changing the vergence of the two eyes so that images that fall on different points in the two retinas come to fall upon corresponding places in the central retinas. (As opposed to Sensory Fusion).

 

Movement Agnosia

A selective loss of motion perception without loss of any other perceptual capability. Occurs after bilateral damage in the cortex of MT or MST.

 

MST

(See Appendix I: Cortical Areas).

 

MT

(See

Appendix I: Cortical Areas).

 

Muller-Lyer Illusion

Two lines of equal length appear to unequal.

Munker-White Illusion

Myopia

An eye is myopic when the "far point"; a point at which light from an object is focussed on the retina, is located at a finite distance in front of the eye. Myopia can be due to either an eye which is too long relative to the optical power of the eye (axial myopia), or because the optical power of the eye is too high relative to the length of the standard eye (refractive myopia). The focus is correctly adjusted with a "minus" power lens, or concave lens. Myopia is often referred to as "short-sightedness" or "near-sighted". (See also Hyperopia and Emmetropia).  (More Information)