Spatial Vision: From Spots to Stripes. LGN Flashcards
Contrast
The difference in luminance between an object and the background or between lighter and darker parts of same object.
Acuity
Smallest spatial detail that can be resolved.
Cycle
For a grating, a pair consisting of one dark bar and one bright bar.
Visual Angle
The angle subtended by an object at the retina.
Sine Wave Grating
A grating with a sinusoidal luminance profile.
Aliasing
Misperception of a grating due to undersampling.
Spatial Frequency
The number of grating cycles in a given unit of space.
Cycles per degree
The number of pairs of dark and bright bars per degree of visual angle.
Contrast Sensitivity Function (CSF)
A function describing how the sensitivity to contrast (defined as the reciprocal of the contrast threshold) depends on the spatial frequency (size) of the stimulus.
Contrat Threshold
The smallest amount of contrast required to detect a pattern.
Phase
The relative position of a grating.
Lateral geniculate nucleus (LGN)
A structure in thalamus, part of mid brain, that receives input from the retinal ganglion cells and has input and output connections to the visual cortex.
Magnocellular Layer
Either of the bottom two neuron-containing layers of the lateral geniculate nucleus, the cells of which are physically larger than those in top 4 layers.
Parvocellular layer
ANy of the top 4 neuron-containing layers of the LGN, the cells of which are smaller than those in bottom two layers.
Konicellular Cell
A neuron located between m and p celllar layers of LGN
Contralateral
Opposite side of body or brain
Ipsilateral
Same side
Tomographical mapping
Orderly mapping of the world in the LGN and V cortex.
V1
Area of cortex that receives direct inputs from the LGN as well as feedback from other brain areas, responsible for processing visual information.
Cortical magnification
AMT of cortical area devoted to specific region in visual field.
Visual Crowding
The deleterious effect of clutter on peripheral object recognition.
Orientation Tuning
Tendency of neurons in V1 to respond optimally to certain orientations and less to others.
Ocular dominance
Property of receptive fields of V1 neurons by which they demonstrate a preference, responding somewhat more rapidly when a stimulus is presented in one eye than when it is presented in the other.
Simple cell
a cortical neuron with clearly defined excitatory and inhibitory regions
complex cell
a neuron whose receptive field characteristics cannot be easily predicted by mapping with spots of light.
End stopping
The process by which a cell in the cortex first increases its firing rate as the bar length increases to fill up its receptive field, and then decreases its firing rate as the bar is lengthened further.
Column
Vertical arrangement of neurons.
cytochrome oxidase (CO)
An enzyme used to reveal the regular array of CO blocks.
Adaptation
A reduction in response caused by prior or continuing stimulation.
Ambylopia (Lazy eye)
A developmental disorder characterized by reduces spatial vision in an otherwise healthy eye, even with proper correction for refractive error.
Strabismus
A misalignment of two eyes such that a single object in space is imaged on the fovea of one eye, and on the nonfoveal area of the other.
Anisometropia
A condition in which the two eyes have different refractive errors.
