Chapter 3: Sensation and Perception of Visual Signals

Question 1

visual field

Answer 1

The full extent of what one can see while holding the eye still, measured as degrees of angle from the point of fixation.

Question 2

horizontal meridian

Answer 2

The imaginary horizantal line that divides the visual field into upper and lower quadrants.

Question 3

visual hemifield

Answer 3

The half of the visual field represented in V1 of the one hemisphere.

Question 4

veritcal meridian

Answer 4

The imaginary vertical line that divides the visual field in half, thereby defining the boundary between the two hemifields.

Question 5

degrees of visual angle

Answer 5

When foveating an object in the environment, the surface areas of retina that that object occupies can be expressed as an angle anchored in the fovea, and whose imaginary sides project to the left and right edges of the object. The larger the object, the wider the degrees of visual angle that it occupies.

Question 6

phototransduction

Answer 6

The conversion of energy from the electromagnetic specrum (“visible light”) into neural signals.

Question 7

retinal gnaglion cells

Answer 7

The neurons in the retina that send visual signals to the thalamus.

Question 8

scotoma

Answer 8

A small area of blindness in the visual field surrounded by normal visual sensation.

Question 9

retinotopic organization -or- retinotopy

Answer 9

The property of reinstating the spatial organization of the retina in the spatial organization of visual regions of the brain, such that, for example, adjacent regions of the retina are expressed by adjacent regions of visual cortex.

Question 10

striate cortex

Answer 10

Another name for V1, so named for its striped appearance when viewed in just the right way,

Question 11

receptive field

Answer 11

The portion of the sensory-transduction surface that is represented by a neuron.

Question 12

fovea

Answer 12

Region of the retina most densely packed with photoreceptors, and thus supporting highest resolution of vision.

Question 13

extrastriate cortex

Answer 13

Cortex that is part of he visual system, but not a part of striate cortex (i.e., it is beyond the visual cortex)

Question 14

cortical magnification

Answer 14

The phenomenon hat high resolution regions of a sensory-transduction surface, or ore finely controlled muscles, are represented by larger areas of cortex.

Question 15

feature detector

Answer 15

An element in a sensory processing array whose function is to signal each time it detects the presence of the feature for which it is tuned.

Question 16

hypercolumn

Answer 16

A hypothesized functional unit of cortical columns in V1, the totality of which represents every possible feature that could be presented to a specific V1 receptive field.

Question 17

pinwheel

Answer 17

The actual physical layout, discovered with optical imaging, of the cortical columns that accomplish the function that had been proposed for the hypercolumn.

Question 18

inhibitory surround

Answer 18

A mechanism for increasing the signal-to-noise ratio of a neural representation by inhibiting activity corresponding to adjacent, but irrelevant, representations.

Question 19

dipole

Answer 19

An object with a positive charge at one end and a negative charge at the other.

Question 20

inverse problem

Answer 20

The fact that there is an infinite number of possible source solutions for any pattern of voltages distributed across the scalp.

Question 21

predictive coding

Answer 21

The idea that a core function of the bain is to construct, and constantly update, a model of what’s likely to happen in the future.