Sensation & Perception (part 1) Flashcards
The first 5 weeks of the course, so everything for exam 1!
What five methods to study sensation and perception does the book mention?
- Thresholds
- Scaling
- Signal Detection Theory
- Sensory neuroscience
- Neuroimaging
Psychophysics
A method to formally describe the relationship between sensation and the energy or matter that gives rise to that sensation.
Who named the psychophysics method?
Gustav Fechner
JND (abbreviation)
just noticeable difference
Panpsychism
The idea that the mind exists as a property of all matter, that all matter has consciousness.
Perception
Giving meaning or purpose to detected sensations.
Who are seen as the founders of experimental psychology?
Gustav Fechner (1801-1887) and Wilhelm Wundt (1832-1920).
Who made sense of the way in which JND changes?
Ernst Weber (1795-1878)
What are the Weber fractions concerned with?
The systematic way in which the JND changes: a constant ratio between change in stimulus and standard stimulus, which describes the threshold of the detectable change.
Weber’s law (formula)
[delta].I = K.I
Weber’s law (intuitive)
The size of the detectable difference is equal to a constant proportion of the level of stimulus.
Fechner’s law (formula)
S = k * log (R)
Fechner’s law (intuitive)
The psychological sensation is equal to a constant k times the logarithm of the physical stimulus level, so our experience of intensity increases less than the actual stimulus increases.
Absolute threshold
The minimum amount of stimulation necessary for a person to detect a stimulus 50% of the time.
What three ways os studying thresholds are discussed in the book?
- Method of constant stimuli
- Method of limits
- Method of adjustment
Method of constant stimuli
Many stimuli with different intensities are presented one at a time, to find the smallest intensity that can be detected.
Method of limits
Stimuli with different intensities. In order of increasing or decreasing intensity until first detected or not detected anymore. Average is taken as threshold.
Method of adjustment.
Method of limits where the participant adjusts the stimuli intensity herself.
Magnitude estimation
A task in which participants need to rank a number of sensations based on perceived intensity.
Steven’s power law (formula)
S = a * (I^b)
Steven’s power law (intuitive)
The magnitude of subjective sensation S is related to the stimulus intensity I by exponent b. We use constant a to correct for the units used.
Cross-modality matching
Participants have to adjust a stimulus of one kind to match the intensity of another kind of stimulus.
Qualia
The experiences when you see/hear something, the qualitative experience.
How can we deal with a non-absolute threshold?
Signal Detection Theory
What is the simplest kind of sound?
A sinus wave.
What do we call the time taken for a wavelength in sound?
a period
What do we call the height of a wave in sound?
the amplitude
What is the phase of a wave in sound?
The position relative to a fixed marker, measured in degress.
How many degrees are there across one period in sound?
360
Fourier analysis
The process of breaking down a complex sound into individual sine wave components. (or images into spatial frequencies)
What are units of spatial frequency?
cycles per degree of visual angle
Doctrine of specific nerve energies
We are only aware of the activity in our nerves, not directly of the world itself. It isn’t important how nerves are stimulated, but what nerves are stimulated.
What cranial nerves are dedicated to sensory information?
- Olfactory nerve
- Optic nerve
- Vestibulocochlear nerve
What cranial nerves are dedicated to muscles that move the eyes?
- Oculomotor nerve
- Trochlear nerve
- Abducens
Vitalism
The idea that there is a force in life that is distinct from physical entities.
Synapse
The tiny gap between the axe of one neuron and the dendrite of the next. Permits information transfer.
What happens to the speed of neural transmission at the synapses?
It decreases.
EEG
electroencepalography
ERP
event-related potential
MEG
magnetoencephalography
CT
computed tomography
MRI
magnetic resonance imaging
How does EEG work?
It measures electrical activity with electrodes on the scalp.
What are the results of an EEG?
Can roughly localize populations of neurons, but not able to pinpoint area of neural activity. Very good temporal accuracy.
What is an ERP?
A measure of electrical activity from a subpopulation of neurons in response to particular stimuli, the average waveform that results from many EEG recordings.
What results does an MEG give?
Tiny magnetic field changes, maintains timing of neuron populations and has good image of where in the brain neurons are most active.
What results does a CT give?
A 3D picture of the head.
BOLD
blood oxygen level-dependent
What results does an MRI give?
The BOLD signal is measured, slow and noisy and expensive but still good.
PET
positron emission tomography
What is PET?
An imaging technique where radioactive material goes into the bloodstream and a camera detects gamma rays.
What is the most common tracer in PET?
oxygen-15 with a half-life of +-2 minutes.
Electromagnetic radiation
Energy produced by vibrations of electrically charged material.
Photons
Tiny particles that each consist of one quantum of energy, demonstrating both particle and wave properties.
How do we treat light in the book?
As being made up of waves when it moves around the world, and being made up of photons when it is absorbed.
What wavelengths of the spectrum of electromagnetic radiation is light?
Between 400 and 700 nm wavelength.
Hue
The perceptual attribute of colors.
What portions of the electromagnetic radiation spectrium have a smaller wavelength than light?
Gamma rays, X-rays and Ultraviolet.
What portions of the electromagnetic radiation spectrum have a larger wavelength than light?
Infrared, heat, microwaves, FM radio and television.
What is the speed of light?
About 186.000 miles per second = 299.792 kilometer per seconde.
What wavelength is scattered more strongly?
Short-wavelength.
Refraction
When light rays are bent, for example by windows.
Where does the light first get to in the eye?
The cornea.
What does the aqueous humor do?
Supplies oxygen and nutrients to the cornea and cleans the cornea and the lens.
Pupil
A hole in the iris, where the light passes through.
What controls the size of the pupil?
The iris.
What happens when the pupil is large?
The depth of focus is smaller and image quality poor. Used for low light.
Vitreous chamber
Located between the lens and the retina, filled with the vitreous humor.
Vitreous humor
The gel-like substance in the vitreous chamber, refracts the light for the fourth time.
Transduction
The process in the retina where the light energy is turned into electrical neural signals.
What four components of the eye refracts the incoming light?
- the cornea
- the aqueous humor
- the lens
- the vitreous humor
What do the refractive powers of the cornea, aqueous humor, lens and vitreous humor need to be matched to?
The length of the eyeball.
What component of the eye has the most refractive power?
The cornea.
What three components of the eye have a fixed refractive power?
- the cornea
- the aqueous humor
- the vitreous humor
Accomodation
The process of the lens altering the refractive power of the eye by changing shape. Lens gets fatter when gaze directed to nearer objects.
What muscle contracts in accomodation in the eye?
The ciliary muscle.
What happens when the ciliary muscle is relaxed?
The lens is flat and the zonules are stretched. For looking at distant objects.
Lens power (formula)
P = 1/f
with f = focal distance in meters.
D
diopters, a unit to measure accomodation
How does our accomodation change when we get older?
We lose about 1D every 5 years from 8 y/o to 30 y/o.
Presbyopia
Old sight, when old people can’t see at 2.5D anymore. Happens to almost everyone since lens loses elasticity, they lose accomodation.
Why is the lens transparent?
Because it consists of packed together crystallins (proteins).
Cataracts
Opacities of the lens that happen when the regularity of crystallins is disturbed.
Emmetropia
When the refractive power of the eye is perfectly matched to the length of the eyeball.
Refractive errors
When the eyeball is too long or too short relative to the refractive power of the four components, so the image of the world is not clearly focused on the retina.
Myopia
Nearsightedness: When the image is focused in front of the retina, so blur far away.
Hyperopia
Farsightedness, when the eyeball is too short and the images is focused behind the retina. Near objects seen unclearly.
Foveal vision
The central 1.5-2 degrees of the visual field.
Peripheral vision
The visual field outside of the foveal vision.
How are photoreceptor types distributed over the visual field?
Mostly cones in the fovea and mostly rods in the periphery.
How are bipolar cells distributed over the visual field?
Midget bipolar cells in the fovea and diffuse bipolar cells in the periphery.
How is convergence distributed over the visual field?
Low convergence in the fovea and high convergence in the periphery.
How is receptive field size distributed over the visual field?
Small receptive field size in the fovea and large receptive field size in the periphery.
How is acuity distributed over the visual field?
High acuity in the fovea and low acuity in the periphery.
How is light sensitivity distributed over the visual field?
Low light sensitivity in the fovea and high light sensitivity in the periphery.
Acuity
Detail
Astigmatism
When the cornea is not spherical, but more circle-like: vertical lines in front of retina and horizontal lines behind retina or vice versa.
How can astigmatism be corrected?
By lenses that have two focal points.
LASIK
laser-assisted in situ keratomileusis
What is LASIK?
An eye surgery where the cornea is reshaped to correct refractive power.
Fundus
The back part of the eye.
Optic disc
A white circle on the fundus where the arteries and veins enter the eyes and the axons of ganglion cells leave the eye via the optic nerve. Has no photoreceptors, so it’s blind.
Fovea
A spot near the center of the macula containing the highest concentration of cones and no rods. Serves as the point of fixation.
Pigment epithelium
A layer of darker cells in the retina, the layer furthest back.
What does the light need to pass through before making contact with the photoreceptors?
The ganglion, horizontal and amacrine cells.
Why are the photoreceptors in their specific location?
The need to be next to the pigment epithelium for nutrition and recycling, as well as next to the other neurons in order to pass along their signals.
How many rods and cones does a human have per eye?
About 90 milion rods and 4-5 million cones.
Retinal eccentricity
Distance from the fovea.
Duplex retina
A retina that consists of both rods and cones.
What happens if we look directly at an object whose image is smaller than one degree?
The image will land on a region of the retina that has only cones.
For what vision stuff do we use the fovea?
To identify objects, read and inspect fine detail.
For what vision stuff do we use the periphery?
When detecting and localizing stimuli that we aren’t looking at directly.
What photoreceptor type picks up on color?
The cones
Photic sneeze reflex
Sneezing in response to being exposed to bright lights.
In what four ways does the visual system adjust to changes in illumination?
- Pupil size
- Photopigment regeneration
- The duplex retina
- Neural circuitry
How does the pupil size adjust to changes in illumination?
The diameter can vary by a factor of about 4. Size determines the amount of light that enters the eye. Takes a few seconds to change, but many minutes in dark adaptation.
How does photopigment regeneration adjust to changes in illumination?
With low light, there is many photopigment and rods & cones respond to as many photons as possible. Photopigment is bleached when photon is detected and needs to be regenerated. With a lot of light: many photons, photopigment molecules cannot be regenerated fast enough.
How does the duplex retina adjust with changes in illumination?
Rods are used when light is low and cones take over when there is too much light for the rods to function well.
How does neural circuitry adjust with change in illumination?
Ganglion cells are most sensitive to light differences in their center & surround of receptive fields, not so affected by average intensity of light. Encode patterns of light & dark areas in retinal image.
Receptive field
Region on the retina where visual stimuli influence neuron’s firing rate.
AMD
age-related macular degeneration
What happens in age-related macular degeneration (AMD)?
The macula is affected and gradually destroys sharp central vision.
RP
retinitis pigmentosa
What happens in retinitis pigmentosa?
There’s a progressive degeneration of the retina that affects night vision and peripheral vision.
What are the 5 classes of neurons in the retina?
- Photoreceptors
- Horizontal cells
- Bipolar cells
- Amacrine cells
- Ganglion cells
Photoreceptors
Neurons that produce chemical changes that start a neural events chain. Sends signals by synaptic terminals.
What do photoreceptors consist of?
An outer segment, inner segment and synaptic terminal.
What does the inner segment in a photoreceptor do?
It makes visual pigments.
What does the outer segment in a photoreceptor do?
It stores the visual pigments that the inner segment made.
What does a visual pigment molecule consist of?
Protein (opsin) and cromophore.
Cromophore
Captures light signals, retinal.
Rhodopsin
A visual pigment in rods
Melanopsin
A photopigment that is sensitive to ambient light. Specifically found in a photosensitive ganglion cell in the retina.
Lateral inhibition
Antagonistic neural interaction between adjacent regions of the retina. Enables signals to be based on differences in activation between nearby photoreceptors.
What is the role of bipolar cells?
Determine info that is passed from phootreceptors to ganglion cells. Are small, have a specific amount of neurotransmitter release and all the same rate of response.
Describe the response pattern of diffuse bipolar cells
Respond to a single point of bright light at the same rate as to several sports of dim light.
Midget bipolar cells
what do they do + where?
Pass info from single cones to single ganglion cells and exist only in the fovea.
What is the location of the amacrine cells?
Part of the lateral pathway, they’re in the inner layers of the retina.
What is the role of amacrine cells?
Receive inputs from bipolar cells and other amacrine cells and send signals to bipolar, amacrine,and retinal ganglion cells.
Serve as a switch between rod and cone system.
Where are the ganglion cells
The final layer of the retina, can be P or M ganglion cells.
Where from do P ganglion cells receive + what do they feed?
Receive from the bipolar cells and feed the parvocellullar layer of the LGN
M ganglion cells
Receive from the diffuse bipolar cells and feed the magnocellular layer of the LGN.
LGN
lateral geniculate nucleus
Photoactivation
Bleaching: the process where a photon is absorbed by a molecule of rhodopsin in the outer segment of a rod and transfers its energy to the chromophore portion of the visual pigment molecule.
Hyperpolarization
A change in membrane potential such that the inner membrane surface becomes more negative than the outer membrane surface.
S-cones
short-wavelength sensitive cones
What do we mean with ‘the foveal centre is dichromatic’?
It has only two color-sensitive cone types.
L-cones
long wavelength sensitive cones
M-cones
medium-wavelength sensitive cones
Photopic
Light intensities that are bright enough to stimulate the cone receptors and saturate the rod receptors (drive them to max response)
scotopic
Light intensities that are bright enough to stimulate the rod receptors but too dim to stimulate the cone receptors.
What type of cones misses from the center of the fovea?
S-cones
What cells form a lateral pathway in the retina?
Horizontal and amacrine cells
What cells form a vertical pathway in the retina?
Photoreceptors, bipolar cells and ganglion cells.
ON-center bipolar cell
Increases firing rate when light in center of RF, decreasing firing rate when light in surround. Depolarizes in response to increase in light.
OFF-center bipolar cell
Hyperpolarizes in response to increase in light. Responds to light in the surround, not in the center.
RGC
retinal ganglion cell
RF
receptive field
When does a ganglion cell fire the fastest?
When the spot of light is the same size as the excitatory centre. (just the right size, less when larger or smaller).
Center-surround antagonism
lateral inhibition
What is the effect of a high degree of convergence in the retinal periphery?
High sensitivity to light, but poor acuity.
What is the effect of the low degree of convergence in the fovea?
High acuity, but poor sensitivity to light.
Why are images seen more clearly when they fall on the fovea?
Only there there are one-to-one pathways between cones and ganglions.
What are our senses?
- Vision
- Hearing
- Taste
- Smell
- Touch
What is the fancier word for the hearing sense?
Audition.
What is the fancier word for the taste sense?
Gustation
What is the fancier word for the smell sense?
Olfaction
What is the fancier word for the touch sense?
Somatosensation
What is the sixth sense according to Harvey?
Balance
What is the fancier word for balance?
Vestibular
Which of the senses is our primary sense?
Vision (/sight)
Sensation
The translation of the external physical environment into a pattern of neural activity (by a sensory organ).
What is the method in perceptual threshold detection called where you change the difficulty of the next trial depending on the answer on the previous trial?
The adaptive method.
What are the three types of brain activity discussed in lecture 1?
- Spiking activity
- Synaptic activity
- Metabolic activity
Spike activity
Brain activity: spikes are action potentials of individual neuron. Can be measured directly from the neuron (ethical issues).
What is + how do you measure synaptic activity
Synaptic potentials, can be measured with scans by putting a detector in between two cells and measure results of them firing.
What is metabolic activity?
Oxygen and glucose consumption.
Describe the cycle of interaction between excitatory and inhibitory neurons:
When excitaroy pool becomes active, it activates the inhibitory pool. The inhibitory pool becomes activated then and inhibits the excitatory pool so that its activity goes down. The excitatory pool stops exciting the inhibitory pool, and thus the injibitory pool stops inhibiting the excitatory pool which then gives rise to activity in the excitatory pool, and back to the start.
LFP
Local field potential.
What is the influence of the LFP on perception?
When the local field potential is high, you’re more likely to perceive than when it is low.
How does the measurement of fMRI work?
The human body is mainly water. All the atoms point the same way when in a permanent static magnetic field. But if pushed in another field in a different direction, and that second field is removed, the atoms bounce back in their position and release activity. Now you can measure water density.
Where does the translation from photons to electrical signals happen?
In the photoreceptors.
How are photons translated to neural signals?
Cross-membrane proteins in the photoreceptors change structure if they catch a photon and then their membrane opens. Potassium can come out then.
What type of photoreceptor do we see colors with?
Cones
Rhodopsin
The protein in a rod photoreceptor.
Horizontal cell (role in chain)
Get input from photoreceptors and output inhibition.
Where are they + what do they do? Postreceptoral layers of the retina
In the eyeball, translate the raw light array captured by the photoreceptors into the patterns of spots surrounded by darkness detected by ganglion cells.
What do ganglion cells in the retina respond well to?
Spots of light
What do neurons in the cerebral cortex respond well to?
Lines, edges and stripes.
Contrast
Difference in illuminaton.
Wat is a cycle when talking about grating vision?
One repetition of a black and white stripe.
Visual angle
The angle that would be formed by lines going from top/bottom or left/right of a cycle on the page, passing through the center of the lens and ending on the retina.
How many degrees is one centimeter?
1
How many arc minutes is one centimeter/one degree?
60
Why is visual acuity poorer in the periphery compared to the fovea?
Rods and cones are less tightly packed together and less receptors converge on each ganglion cell.
Horizontal and vertical assymetry
The visual acuity in the peripheral vision is not uniform, it degrades more rapidly along the vertical midline of the visual field.
Vertical meridian assymetry
We have a better acuity a fixed distance below the midline of the visual field than above.
What type of vision is slower: central or peripheral?
Central vision is slower: foveal cones have longer axons which transmit slow signals better.
What does 20/15 vision mean?
THa you’re worse than average, because you need to stand at 15m instead of 20m to read the letters.
Amblyopia
A developmental disorder with reduced spatial vision in a healthy eye, even with proper correction for refractive error. = Lazy eye
List the different forms of acuity:
- Minimum visible
- Minimum resolvable
- Minimum recognizeable
- Minimum discriminable
Minimum visible acuity
The smallest object that one can detect. Limited by our ability to discriminate intensity relative to background.
Minimum resolvable acuity
THe smallest angular separation between neighboring objects that one can resolve. Limited by spacing of photoreceptors in retina (foveal vision).
Minimum recognizable acuity
The angular size of the smallest feature that one can resolve.
Minimum discriminable acuity
The angular size of the smallest change in a feature that one can discriminate.
Vernier acuity
The smallest misalignment one can reliably discern when looking at two lines that are aligned.
Spatial frequency
The number of times a pattern repeats in a given unit of space.
CSF
contrast sensitivity function.
Michelson definition of the CSF
C = (Lmax - Lmin) / (Lmax + Lmin)
with L = luminance
Geniculate
‘bent’
What spatial frequency does an ON-center ganglion cell respond well to?
Medium spatial frequency
Why does an ON-center cell responds well to medium frequency?
With a low SF, the bright bar of gratings lands in the inhibitory surround and with a high SF, both dark and bright bars fall within the receptive field center.
How many layers does the LGN consist of?
6
What are the bottom two layers of the LGN called?
Magnocellular layers
Why are the bottom two layers of the LGN called ‘magnocellular layers’?
Because there are larger neurons there than in the top four layers.
Magnocellular layers
Receive input from M ganglion cells in the retina. Responds to large, fast-moving objects.
What are the top four layers of the LGN called?
Parvocellular layers
Parvocellular layers
The top four layers in the LGN, have smaller neurons than the magnocellular layers. Receive input from P ganglion cells. Responsible for processing details of stationary targets.
What do the layers in-between the layers in the LGN consist of?
Koniocellullar cells
Contralateral
Left eye
What layers of the LGN receive contralateral input?
1, 4 and 6
Ipsilateral
Right eye
What layers of the LGN receive ipsilateral input?
Layers 2, 3 and 5.
From what eye does the right LGN receive input?
Left eye
Topographical mapping
The orderly mapping of the world in the lateral geniculate nucleus and the visual cortex.
What is written about the connections between the LGN and the visual cortex? (direction, ratio)
There are more feedback connections from the visual cortex to the LGN than feed-forward from LGN to visual cortex.
What part of the brain is inhibited while sleeping?
the thalamus (LGN is part of thalamus, so no vision while sleeping)
Inion
A bump at the back of your head, below which is the primary visual cortex.
V1
Primary visual cortex
Area 17
Prmary visual cortex
How is the striate cortex built up?
Six layers, some having sublayers.
What layer of the striate cortex does the LGN project to?
Mostly to layer 4.
Where do the magnocellular axons go in the striate cortex?
The upper part of layer 4C, called 4Calpha
What part of the striate cortex do the parvocellular axons connect to?
The lower part of layer 4C, called 4Cbeta
Name two important features of the visual cortex:
- Topograhpy
- Magnification
Cerebral cortex
Primary visual cortex
Cortical magnification
The process that objects on the fovea get much more processing space in the cortex than objects in the periphery.
->Cortical representation of fovea is magnified compared to that of peripheral vision.
Visual crowding
A phenomenon in the periphery when objects are not recognized as well because they appear combined with surroundings.
Ocular dominance
The property of striate receptive fields that they have a preference for a stimulus in one eye versus the other eye.
Simple cell
The ‘line detector’. An edge detector in V1 that has clear ON and OFF regions, is orientation selective and gets input from LGN cells.
Edge detector
The three types of cells in V1. Have large receptive fields and are the basis of simple object recognition.
Stripe detector
The simple cell. Excited when a line of light with a particular width is surrounded by darkness.
Complex cells
The ‘motion detector’. No clear ON and OFF regions. Respond best to a moving edge with a particular orientation and direction. Get input from simple cells.
End stopping
A property of some cells in the striate cortex. Happens in hypercomplex cells: response rate increases when filling up RF, but decreases as bar extends beyond RF.
Perpendicular
Loodrecht op
Hypercolumn
A column of 2 sets of columns: each set has one left dominant & one right dominant column that both have every possible orientation. Responsible for all processing of a small part of the visual field.