2.4 compleet 3

Optic Axis

Optic Axis

imaginary diameter line from front to back of eye, passes through lens centre: passes through centre of lens

Sclera

Cornea-forms the outer membrane, protective covering that is the white of the eye- transparent cornea at front of eye

Cloroid/vaatvlies

middle membrane, lining the interior of the sclera: contains most blood vessels supplying inside of eye with oxygen and nutrients

Retina

inner membrane, made up of neurons (including receptors converting light entering, into neural signals

Pupillary reflex

the automatic process which causes the following: Intense light= constricts- pupil smaller, less light enters, dim light= dilates- pupil larger, more light enters

Anterior Chamber

space between cornea and iris

Posterior Chamber

space between iris and lens

Aqueous humor

the clear, thin, fluid filling the space in the front of the eyeball between the lens and the cornea.

Vitreous chamber

main interior portion of the eye

Vitreous humor

the transparent jellylike fluid filling the eyeball behind the lens.

Intraocular pressure

pressure of the fluids in the three chambers of the eye

Focal length

the distance from a lens at which the image of an object is infects when the object is far away from the lens

Lens

transparent structure near the front of the eye that refracts the light passing through the pupil so light focuses properly on the retina

Diopters

Units used to express the power of a lens; diopters= 1/focal length

Zonule fibers

Fibers that connect the lens to the choroid, they pull on the lens to change its shape

Ciliary muscles

Tiny muscles attached to choroid; relax and contract to control how choroid pulls on zone fibres to change shape of the lens

Accommodation

Adjustment of shape of the lens so light from objects at different distances focuses correctly on the retina

Retinal image

A clear image on the retina of the optic array

Nuclear Layers

The three main layers of the retina, including the outer nuclear layer, inner nuclear layer, and ganglion cell layer

Synaptic layers

In the retina, two layers separating the three nuclear layers

Photoreceptors

Retinal neurons that transduce light into neural signals

Rods and Cones

The two classes of photoreceptors, named for their distinctive shape

Pigment epithelium

A layer of cells attached to the choroid; photoreceptors are embedded in it

Outer nuclear layer

Layer of retina consisting of photoreceptors (not including inner and outer segments)

Inner nuclear layer

Layer of retina that contains bipolar cells, horizontal cells, and amacrine cells

Bipolar cells

Neurons in the inner nuclear layer of the retina

Horizontal and amacrine cells

neurons in the inner nuclear layer of the retina

ganglion cell layer

the layer of the retina that contains retinal ganglion cells

Retinal ganglion cells

Neurons in the ganglion cell layer of the retina

Outer synaptic layer

layer of the retina that contains the synapses among photoreceptors, bipolar cells, and horizontal cells

Inner synaptic layer

Layer of retina that contains the synapses among bipolar cells, amacrine cells, and RCGs

Optic disk (blink spot)

Location of the retina that contains the synapses among photoreceptors, bipolar cells, and horizontal cells

Optic nerve

Nerve formed by the bundling together of the axons of RGCs; it exits the eye through the optic disk

Fovea

A region in the centre of the retina where the light from objects at the centre of our gaze strikes the retina; contains no rods and a high density of cones

Luminance contrast

A difference in the intensity of illumination at adjacent retinal locations

Selective rearing

if an animal is reared in an environment that contains only certain types of stimuli, then neurons that respond to these stimuli will become more prevalent

Orientation columns

Cortex is organised so neurons along same perpendicular track have preference for stimuli with same orientations

Ocular dominance

Preferential response int he cortex to one eye

Ocular dominance columns

neurons with the same ocular dominance are organised in this way

Hypercolumn

Combo of all three types of columns into this larger unit

cortical magnification factor

an area close to the fovea is allotted more cortical space to than area further away

Acromatopsia

cortical colour blindness

ablation

destruction/removal of tissue in the nervous system

visual agnosia

pathway to temporal lobes is responsible for object identification

object discrimination problem

removal of temporal lobes made object discrimination after ablation difficult

landmark discrimination problem

removal of parietal lobes made location discrimination after ablation difficult

optic ataxia

pathway to parietal lobes is responsible for object localization

psychophysics

Study of the relationship between physical stimuli in the world and the sensations that we experience

Problem of detection

Measuring the minimum intensity of a stimulus that we can perceive

Problem of discrimination

Measure how different two stimuli must be before they appear the same

Problem of scaling

Describe the relationship between the intensity of the stimulus and the intensity of our sensation

Absolute threshold

Minimum amount of energy change from zero

Adaptive testing

keeping the test stimuli "hovering around" the threshold by adapting the sequence of stimulus presentations to the observer's responses

Catch trials

No stimulus is presented into the series of trials om te kijken of participanten gokken

Difference threshold

threshold for perception fo difference between the standard and the other stimuli

Negative time error

stimulus presented first (usually the standard) is judged to be less intense than the later stimulus

Weber's law

The relation between the size of the difference threshold and the magnitude of the standard

Weber's fraction

delta I/I

Simple reaction time

pressing or releasing a button immediately on detecting a stimulus

Choice reaction time

making one of several different responses depending on the stimulus presented

S-cone (blue)

Short cone, preferentially sensitive to short wavelengths

M-cone (green)

Cone that is preferentially sensitive to middle wavelengths

L-cone (red)

Cone that is preferentially sensitive to long wavelengths

Spectral sensitivity

Referring to the sensitivity of a cell or device to different wavelengths on the electromagnetic spectrum

Photopic

Light intensities that are bright enough to stimulate the cone receptors and bright enough to "saturate" the rod receptors

Scotopic

Light intensities that are bright enough to stimulate the rod receptors but too dim to stimulate the cone receptors

Principle of univariance

an infinite set of different wavelength-intensity combinations can elicit exactly the same response from a single type of photoreceptor: one photoreceptor type cannot make colour discriminations based on wavelength

Trichromacy (Young-Helmholtz Theory)

theory that the colour of any light is defined in our visual system by the relationships of three receptor types, know as the three cones

Metamers

Different mixtures of wavelengths that look identical: any pair of stimuli that are perceived as identical despite physical differences

Additive colour mixture

a mixture of lights- if light A and light B are both reflected from a surface to the eye, in the perception of colour the effects of those two lights add together

Subtractive colour mixture

A mixture of pigments. If pigments A and B mix, some of the light shining on the surface will be subtracted by A, and some by B. Only the remainder contributes to the perception of colour

Lateral geniculate nucleus

Structure in the thalamus, part of the midbrain that receives input from the retinal ganglion cells and has input and output connections to the visual cortex

Cone-opponent cell

cell type (in retina, LGN, & visual cortex) that subtracts one type of cone input from another

Koniocellular

Referring to cells in the koniocellular layer of the LGN of the thalamus

Parvocellular

Referring to cells in the parvocellular layers of the lateral geniculate nucleus of the thalamus

Circadian

Biological cycle that recurs approximately every 24 hours, even in the absence of cues to time of day

melanopsin

A photopigment, found in a class of photoreceptive retinal ganglion cells

Colour space

3D space, established because colour perception is based on the outputs of 3 cone types, that describes the set of all colours

Opponent colour theory

Theory that perception of colour is based on output from three mechanisms, each of them resulting from opponent between two colours: red-green, blue-yellow, and black-white

Unique hue

any of 4 colours that can be described with only a single colour term (red, yellow, green, blue). Other colours can be described as compounds

Double opponent cells

Cell type found in visual cortex, where one region is excited by one cone type, combination of cones, or colour, and inhibited by the opponent cones or colour. Adjacent region would be inhibited by 1st input and excited by 2nd

Achromatopsia

Inability to perceive colours caused by damage to CNS

Deuteranope

Individual who suffers from colour blindness, due to absence of M-cones

Protanope

individual who suffers from colour blindness due to absence of l-cones

Tritanope

Individual who suffers colour blindness due to absence of s-cones

Colour-anomalous

Colour-blind

Cone monochromat

Individual with only one cone type: truly colour blind

rod monochromat

individual with no cones of any type, additional to being truly-colour blind, also badly visually impaired in bright lights

Agnosia

Failure to recognise objects despite ability to see them (due to brain damage)

Anomia

Failure to name objects despite ability to see and recognise them (due to brain damage)

Colour contract

Colour perception effect where colour of one region indices opponent colour in neighbouring region

Colour assimilation

colour perception effect in which two colours bleed into each other, each taking on some of the chromatic quality of the other

Negative afterimage

An afterimage whose polarity is the opposite of the original stimulus. Light stimuli produce dark negative afterimages. Colour are complementary

Adapting stimulus

Stimulus whose removal produces a change in visual perception of sensitivity

Neutral point

point at which opponent colour mechanism is generating no signal. If red-green and blue-yellow mechanisms at neutral points, a stimulus will appear achromatic

Amplitude or intensity

The magnitude of displacement (increase or decrease) of a sound pressure wave. Amplitude is perceived as loudness.

Frequency

For sound, the number of times per second that a pattern of pressure change repeats: perceived as pitch

Hertz

the unit of frequency, equal to one cycle per second

Sine Wave

Waveform for which variation as a function of time is a sine function

Spectrum

Representation of the relative energy (intensity) present at each frequency