Samenvatting

Summary - Brain and Cognition: Perception (FSWP2-040-A)

1 keer verkocht

Instelling
Erasmus Universiteit Rotterdam (EUR)

This is a summary of the 2.4 Brain and Cognition course (EUR). This summary integrates all the relevant literature, including also important information discussed during tutorial meetings.

[Meer zien]

Voorbeeld 4 van de 51 pagina's

Bekijk voorbeeld

Geupload op 27 december 2023
Aantal pagina's 51
Geschreven in 2022/2023
Type Samenvatting

brain
cognition
erasmus university
psychology
eye
ear
perception
neuro
neuropsychology
vision

Volgen

ilinaaasparuhova Lid sinds 1 jaar 14 documenten verkocht

€13,99

In winkelwagen

Op verlanglijstje

100% tevredenheidsgarantie
Direct beschikbaar na je betaling
Lees online óf als PDF
Geen vaste maandelijkse kosten

2.4: Perception
Problem 1: The Eye
The Eye
- roughly spherical with a diameter of about 24 mm
Þ optic axis – imaginary diameter from the front to the back
of the eye, passing through the centre of the lens
o each eye points in the direction defined by the optic
axis
Þ Membranes
o sclera – outer membrane à a tough protective
covering whose visible portion is the white of the eye
and the transparent cornea at the front of the eye
o choroid – middle membrane à lines the interior of the
sclera and contains most of the blood vessels that
supply the inside of the eye with oxygen and nutrients
o retina – inner membrane à made up of neurons,
including the receptors that convert the light entering
the eye into neural signals
Þ cornea – transparent membrane at the front of the eye
o light enters the eye by first passing through the cornea
which sharply refracts (bends) the light
o performs most of the focusing light on the retina process
o rigid; cannot adjust how much light passing through is refracted
Þ pupil – an opening in the middle of the iris through which light enters the eye
o diameter: 2-8mm
o when pupil gets smaller à it constricts
o when pupil gets larger à it dilates
Þ iris – coloured part of the eye with an opening in the middle (the pupil)
o pupillary reflex – controls the size of the pupil by contracting and relaxing , mainly in
response to the intensity of light entering the eye
• intense light à iris contracts àsmaller pupil à reduces the amount of light that
can enter the eye
• dim light à iris relaxes à larger pupil à increases the amount of light that can
enter the eye
Þ Chambers
o anterior chamber – the space between the cornea and the iris
• filled with aqueous humor – a clear thin fluid
o posterior chamber – the space between the iris and the lens
• filled with aqueous humor – a clear thin fluid
o vitreous chamber – the main interior portion of the eye
• filled with vitreous humor – a clear, gel-like fluid
è the aqueous & vitreous humor slightly refract light, O2 and nutrients
Þ lens – a transparent structure that further refracts the light, to ensure that light focuses
properly on the retina
o focal length – the distance from the lens at which the image of an object is in focus
when the object is far away from the lens

, • strong lens à refracts light sharply à it is relatively thick, rounded, has a short
focal length
o zonule fibres – fibres that connect the lens to the choroid; they pull on the lens to
change its shape
o ciliary muscles – tiny muscles attached to the choroid; they relax and contract to
control how the choroid pulls on the zonule fibres to change the shape of the lens à
increase the focusing power of the lens
Þ optic disk (blind spot) – location on the retina where the axons of RGCs exit the eye
through the optic disk
o axons of the RGC come together at the optic disk and exit the eye in a bundle (the optic
nerve)
Þ optic nerve – formed by the bundling together of axons of RGCs; it exits the eye through
the optic disk
Þ fovea – a region at the centre of the retina where the light from objects at the centre of our
gaze strikes the retina
o contains no rods
o very high density of cones
Þ accommodation – the adjustment of the shape of the lens to focus on objects at different
distances from the eye
o ciliary muscles: relaxed à the choroid can pull on the zonule fibres
• this stretches the lens = relatively thin, flat shape = relatively weak lens with a
relatively long focal length, appropriate for focusing light from distant objects
o ciliary muscles: contract à they oppose the pull by the choroid on the zonule fibres
• lens isn't stretched as much = thicker, more rounded shape = a stronger lens with
a shorter focal length, appropriate for focusing light from nearer objects
Anatomy of the Retina
Þ made up of several different classes of neurons – each class performs a distinct function
Þ photoreceptors – retinal neurons (rods and cones) that transduce light into neural signals;
send signals to bipolar cells; send to and receive signals from horizontal cells
o rods – provide black-and-white vision in dim light
o cones – provide high-acuity colour vision in bright light
Þ pigment epithelium – a layer of cells attached to the choroid; photoreceptors are embedded
in it
o receive nourishment from it
Þ retina à structured in layers à nuclear layers – the three main layers (outer nuclear, inner
nuclear, ganglion cell layers); because they contain the nuclei of various types of retinal
neurons
1. outer nuclear layer – consists of the photoreceptors (not including their inner and
outer segments)
2. inner nuclear layer – contains bipolar cells, horizontal cells, and amacrine cells
è form a network connecting the photoreceptors to the ganglion cell layer
3. ganglion cell layer – consists of retinal ganglion cells (RGCs)
o nuclear layers à separated by two synaptic layers – the outer and the inner synaptic
layer – where the retinal neurons make synapses with each other
1. outer synaptic layer – contains the synapses among the photoreceptors, bipolar
cells, and horizontal cells
2. inner synaptic layer – contains the synapses among the bipolar cells, amacrine
cells, and RGCs

,Þ horizontal cells – receive signals from photoreceptors; if signal: strong, then the horizontal
cells inhibit it and send a weaker version of it

Þ bipolar cells – receive signals from photoreceptors
o send signals to amacrine cells and RGCs
Þ amacrine cells – receive signals from and send signals to bipolar cells and other amacrine
cells
o send signals to retinal ganglion cells

photoreceptors à horizontal cells à bipolar cells à (amacrine cells) à ganglion à optic
nerve à brain
Neural Processing – not that important
- neural circuits – groups of interconnected neurons
Þ convergence – the synapsing of more than one neuron onto a single neuron
o stimulating more receptors increases the amount of excitatory transmitter released
Þ receptive field (of a neuron) – the area on the receptors that influences the firing rate of
the neuron à enables us to specify a neuron’s response
o indicates the location on the receptor surface (retina) that causes a neuron to respond
and the size/shape of the stimulus that causes the best response
Light: Eye
Light reflected from objects in the environment enters the eye through the pupil à
focused by the cornea and lens to form sharp images of the objects on the retina
Þ visual receptors – rods and cones
o contain light-sensitive chemicals à visual pigments that react to light and trigger
electrical signals
• these signals flow through the network of neurons that make up the retina
• the signals then emerge from the back of the eye in the optic nerve, which conducts
signals toward the brain
Þ cornea – accounts for about 80% of the eye’s focusing power
o fixed in place
o can’t adjust its focus
Þ lens – accounts for 20% of the eye’s focusing power
o can change its shape to adjust the eye’s focus for stimuli located at different distance

, object: far; eye: relaxed
o object: more than 20ft away, the light rays that reach the eye are
essentially parallel and they are brought to a focus on the retina (A)
object: near; eye: relaxed
o object: closer to the eye, the light rays reflected from the object enter the
eye at more of an angle, which pushes the focus point back (B) à image:
blurred
object: near; accommodation
o object: closer to eye; the ciliary muscles at the front of the eye tighten
and increase the curvature of the lens so that it gets thicker; pull the focus
back to A to create a sharp image on the retina

Þ near point – the distance at which your lens can no longer adjust to bring close objects into
focus
o presbyopia – the distance of the near point increases as one gets older
• the lens hardens with age and the ciliary muscles become weaker
o around the age of 45 the ability to accommodate begins to decrease rapidly and the
near point moves beyond a comfortable reading distance
Þ myopia (near-sightedness) – the inability to see distant objects clearly à the myopic eye
brings parallel rays of light into focus at a point in the front of the retina do that the image
reaching the retina is blurred
o refractive myopia – the cornea and/or the lens bends the light too much
o axial myopia – the eyeball is too long
Þ far point – the distance at which the spot of light becomes focused on the retina
Þ hyperopia (far-sightedness) – the inability to see nearby objects
o the focus point for parallel rays of light is located behind the retina (usually because
the eyeball is too short)
o constant need to accommodate is required to return the focus point to the retina
Pigments and Perception
Þ distribution of rods and cones
o fovea – contains only cones
o peripheral retina – both rods and cones
Þ macular degeneration – most common in older people – destroys the cone-rich fovea
and a small area that surrounds it => a blind spot in the central vision
Þ retinitis pigmentosa – degeneration of the retina that is passed from one generation to the
next à poor vision in the peripheral visual field
Þ optic nerve damage – glaucoma; fluid in the eyeball = pressure level
o in glaucoma = fluid cannot drain à pressure increases à blood supply gets shut off
à optic nerve starts to degenerate à can cause blindness
Þ astigmatism – asymmetrical lenses/cornea à harder to adjust/accommodate
Þ blind spot – no receptors
Þ dark adaptation – a process which causes the eye to increase its sensitivity in the dark
o dark adaptation curve – a plot of how visual sensitivity changes in the dark
o 2 stages:
• initial rapid stage à due to adaptation of cone receptors
• later, slower stage à due to adaptation of rod receptors
o light: extinguished à sensitivity of both the cones and the rods begins increasing

Dit zijn jouw voordelen als je samenvattingen koopt bij Stuvia:

Bewezen kwaliteit door reviews

Studenten hebben al meer dan 850.000 samenvattingen beoordeeld. Zo weet jij zeker dat je de beste keuze maakt!

In een paar klikken geregeld

Geen gedoe — betaal gewoon eenmalig met iDeal, creditcard of je Stuvia-tegoed en je bent klaar. Geen abonnement nodig.

Direct to-the-point

Studenten maken samenvattingen voor studenten. Dat betekent: actuele inhoud waar jij écht wat aan hebt. Geen overbodige details!

Veelgestelde vragen

Wat krijg ik als ik dit document koop?

Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.

Tevredenheidsgarantie: hoe werkt dat?

Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.

Van wie koop ik deze samenvatting?

Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper ilinaaasparuhova. Stuvia faciliteert de betaling aan de verkoper.

Zit ik meteen vast aan een abonnement?

Nee, je koopt alleen deze samenvatting voor €13,99. Je zit daarna nergens aan vast.

Is Stuvia te vertrouwen?

4,6 sterren op Google & Trustpilot (+1000 reviews)

Afgelopen 30 dagen zijn er 68175 samenvattingen verkocht

Opgericht in 2010, al 15 jaar dé plek om samenvattingen te kopen

Begin nu gratis

Samenvatting

Summary - Brain and Cognition: Perception (FSWP2-040-A)

Document informatie

Onderwerpen

Geschreven voor

Verkoper

Ontvangen beoordelingen

Voorbeeld van de inhoud