Study Guide with answers - Red light, Yellow light, Green light PDF

INTRO – LEC 1 Sensation*- The detection of a stimulus by sensory receptors; not awareness; first steps in converting stimulus to neural activity (so you can perceive it) Perception* - The act of giving meaning to those sensations; refers to the later steps in the perceptual process, wher...

INTRO – LEC 1 Sensation*- The detection of a stimulus by sensory receptors; not awareness; first steps in converting stimulus to neural activity (so you can perceive it) Perception* - The act of giving meaning to those sensations; refers to the later steps in the perceptual process, whereby neural activity is used to represent objects and events so they can be identified, stored in memory, and used in thought and action. o Perception is a product of neural activity o Perception is a generative process (not passive) o Our perception is simply an interpretation of the world (impossible to say what is real) o Physical stimulus – sensory receptor – neural activity Neuron doctrine- diBerent areas of the brain process visual and auditory information – diBerent areas of the brain (or diBerent neurons) do diBerent things Cortical homunculus – diBerent parts of somatosensory cortex respond to touch on diBerent parts of body (disproportional representation) Naïve Realism – we perceive the exact copy of the external world o Illusions prove this is not entirely correct Subjective Idealism/ Mentalism – What we perceive is entirely a product of our minds o We can interact with reality Transduction – physical stimulus transformed into neural signals PSYCHOPHYSICS Psychophysics – relating physical stimulus to perception – Absolute threshold –how much stimulus does it take for a stimulus to be perceived (detection) DiJerence threshold (Just Noticeable DiBerence – JND)– how much diBerence does there have to be between two stimuli to notice a change (Discrimination) o Defines the minimum diBerence between two stimuli that allows an observer to perceive that two stimuli are diBerent – are these two stimuli diBerent? o Always comparing two stimuli – standard stimulus and comparison stimulus o Can be measured with method of adjustment or method of constant stimuli o EX: going to the eye doctor MEAURING ABSOLUTE THRESHOLD Method of Adjustment – adjust a stimulus until it is just barley noticeable – can you see it now? o Repeat several times – quick and dirty way of measuring o EX: brightness settings on video games Method of constant stimuli – select a set of stimulus levels and present in random order o Yes/ no response (yes I detected it or no I did not detect it) Staircase procedure- ask for yes/no response to a stimulus o If yes: make more diBicult  o If no: make easier o Take average value of reversals Psychophysical Scaling – can estimate and compare JNDs for diBerent stimuli as well as how changes in actual intensity relate to changes in perceived intensity o Relationship between physical intensity and perceptual intensity is diBerent for diBerent perceptual dimensions § EG: sound vs. vision o JND varies as a function of intensity § 1 and 2 pounds vs. 1001 and 1002 pounds Psychometric curve o At 50% yes responses determine threshold of detection o Threshold is linked to neural activity o Neurons fire all or none, however stimuli change the rate of firing of neurons § More firing = increased likelihood of perception Signal Detection Theory o Stimulus presented and says a “yes: - considered a hit o Stimulus presented and says “no” – considered a miss o Stimulus NOT presented and says a “yes” – considered a false alarm o Stimulus NOT presented and says a “no” – considered a correct rejection Receiver Operating Characteristic (ROC) – a chance line where participants are equally likely to report a hit or false alarm – a line that demonstrates participants performing at chance level – can compare your actual results to chance line o The further ABOVE you get from the chance line the more accurate participants are § Performing ABOVE chance Level o The further BELOW you get from the chance line the less accurate participants are § Performing BELOW chance level NEUROANATOMY Know basics of neuron and brain lobes FMRI – uses magnetic fields to measure brain activity OPTICS AND THE EYE- LEC 2 Light – the type of electromagnetic radiation that we can see Photons Wavelength- photons constantly oscillate (vibrate) and the distance they travel during one complete oscillation is their wavelength The Electromagnetic Spectrum- has a bunch of diBerent wavelengths, frequency, and energy – light is just a part of it o Some other species can see parts of the electromagnetic spectrum that we can’t (diBerent type of lights)  Four Basic Properties of Light o Light varies in Intensity o Light is composed of tiny particles called photons o Every photon has a wavelength o Photons travel in straight lines unless reflected, absorbed, or refracted Refraction*- when light passes from one medium to another- it changes direction. This change is greater for shorter wavelengths (some colors refracted more than others) VISION – The Human Eye – senses light information – role of vision is to identify diJerences (such as the presence of light and the absence of light) Photoreceptors*- specialized neurons responsible for the transduction of light information into neural signals o Rods and cones o Activated by light o Send their signals via graded potentials § Not an all or nothing action potential o Release Neurotransmitter (NT) glutamate into synapse § activated more when has more light -releases more NT glutamate § less light - releases less NT glutamate o Present on the retina o Signals are sent to bipolar cells and horizontal cells Cornea o Translucent, protective layer, light passes through the cornea § Can regenerate o Has largest refractive eBect of the eye – refracts the most Sclera – the “whites of the eye o Forms outer membrane of the eye- not over Iris and pupil – that is covered by cornea Astigmatism – caused by cornea not being perfectly symmetrical; slightly malformed cornea (world looks blurry) Anterior chamber & Aqueous Humor – o fluid region immediately behind the cornea, o helps give cornea its shape o Supplied oxygen and nutrients and removes waste from cornea and crystalline lens o Too much Humor causes too much pressure which pushes on the retina which causes distortion of vision where someone is blind in the periphery in the field of view (Glaucoma) Iris and Pupil – The colored part of the eye behind the anterior chamber. o Pupil – not its own structure but more of a hole between the iris that lets light in (pupil is part of iris) o Iris – controls size of pupil (amount of light entering in eye § As pupil gets bigger allows more light to enter eye o Pupillary Reflex  § In bright light the iris contracts, which constricts the pupil (lets less light in) § In medium light, the iris contracts less, which dilates the pupil § In dim light, the iris is fully relaxed, and the pupil is fully dilated (lets most amount of light in) Crystalline Lens- Transparent structure behind pupil, it is adjustable (by the ciliary muscle) – major role is to help focus image of the environment onto the retina o Power of lenses – convex lenses of diBerent power bring light to focus at diBerent distances § thicker lens = more focus, more refractive power § thinner lens = less focus, less refractive power o Diopters- how the refractive power of a convex lens is measured Refractive Index- refers to how easily does light pass through (as light passes through it refracts) o Cornea refracts light through pupil onto lens o Emmetropia – When the optics of the eye perfectly refract light into the retina (perfect 20/20 vision) Accommodation*- helps focus the image on the retina, refractive index of lens changes with accommodation, as light changes substances it is refracted Light traveling from far away travels in perfectly parallel lines Light traveling from nearby has lines that are not traveling in perfectly parallel lines, so light is scattered and needs more refraction Ciliary body/ muscle- manipulates shape of crystalline lens to control amount of light passing through More contraction – stronger refraction power Relaxed – weaker refraction power Presbyopia- inability to accommodate due to loss of elasticity in lens, make it diBicult to see nearby objects Myopia – eye too long for optics; long distance between cornea and focal point and lens cannot accommodate enough; nearsighted- distant objects are blurry; image focus before the retina Negative perception – to push that focal point further away decrease the refractive power of the eye – has to decrease the refractive power of the eye Corrective lenses – concave lenses – refract light LESS (scatter) Hyperopia- farsighted; eye too short for optics; image focus behind the retina Must increase refractive power of the eye Nearby objects are blurry Corrective lenses – convex lenses; refract light more Vitreous chamber and humor – behind the lens large (80% of volume of eye) Transparent Can get floaters Retina*- has a bunch of photoreceptors that help with perceiving vision VISION – RETINA Photoreceptors o Contains Visual Pigment molecules o Opsin (protein) – determines what wavelength the photoreceptors will absorb o Chromosphere – will capture the photons associated with that specific wavelength, turns that specific stimulus into activity Rods* - support low-acuity night vision; sensitive to light (very low light activates it), not sensitive to colors o Larger than cones o Opsin: rhodopsin o Works better under dim conditions (scotopic); more sensitive to low levels of light (rely on rods in dim conditions to see) o A high levels of illumination to get bleached out, rhodopsin is “bleached out” § EX: Someone turning on your light in a pitch-dark room § Takes about 30 minutes to regenerate fully § When bleached out only cones function in this condition If going from an extremely light room to complete darkness need around 10 minutes to come back and start using rods and 30 minutes for your rods to fully come back and then you start using your rods more than cones in dark conditions, can’t see well using the cones though so for first 30 minutes you are bumbling around in the dark until your rods adjust o Located primarily in the periphery of the retina § No rods in the center o Have many more rods than we have cones § But only one type of rods Cones*- support high-acuity daylight vision; not as sensitive as rods, but sensitive to diBerent colors o Concentrated primarily in the center of the retina – smaller than rods (find detail) o Required greater illumination (photopic) § Why we need reading light – need more light to activate our cone receptor- cones have more acuity than rods (processes more detailed information) o Better for determining fine details, which is why most cones are at the center of the eye – fovea (because we tend to put the most important things at the center of our vision) o Located primarily in the center for the retina (very few in periphery) o Three types of cones (each respond to diBerent wavelengths – diBerent colors) § S-Cones – sensitive to short wavelengths § M-Cones – sensitive to medium wavelengths § L-Cones – sensitive to long wavelengths o Fovea – where all those densely packed cones are located Optic Disc (blind spot) – hole at back of retina where optic nerves sent signals to brain and where blood vessels lead to and come out of o It is the blind spot in each of our eyes because of the optic disc, our brain fills in the blind spot Horizontal Cells – photoreceptors pass their information through these o Run horizontal to photoreceptors (which are vertical) o Receive their input from multiple receptors § Plays a role in region that defines where light is and dark is § Photoreceptors just say if there is light there yes/no o Like a referee § Determines the boundary between light and dark Bipolar Cells – receive input from rods OR cones (not both); two types of bipolar cells o DiJuse bipolar cells - receive input from rods (LARGE receptive fields) § Many rods project to a single bipolar cell § Increase sensitivity to detecting light but not great resolution § like sampling most people in the room trying to find which one likes feet – going to be able to find that there are but not their specific location o Midget bipolar cells- receive input from cones (SMALLER receptive fields than DiBuse) § Only around 1-3 cones project to each bipolar cell Only a few cones per Midget § Maintain fine details without as much sensitivity to light § Like only sampling a few people in the room but from specific locations to find out who is into feet Less likelihood of finding that person but if you do then you have much more specific area where they could be § Each cone projects to two DIFFERENT bipolar cells On bipolar cells: increased firing rate when light is present OB bipolar cells: Increased firing rate when light is absent Amacrine Cells – finding where is light and dark (similar to horizontal cells) o Comparing diBerences between light with horizontal cells across space o Information passes from cones to bipolar cell o Sends signal to bipolar, amacrine and ganglion cells Retinal Ganglion Cells*- connects to optic nerve that leads to brain o Parasol Ganglion Cells – receives input from diBuse BP § 8-10% ganglion cells- need less cause can have LOTs of rods per parasol § Project to the Magnocellular layer of LGN (magno = large) o Midget Ganglion Cells- Input from midget BP cells § 70% ganglion cells – need more because can only have a few cones per midget § Project to the Parvocellular layer of LGN (parvo = small) Convergence – more convergence means increased sensitivity; based on how many photoreceptors are projecting to each ganglion cell o Many photoreceptors to one ganglion cell – higher convergence  § Higher sensitivity – lower acuity (lower resolution) Does not need as much light to activate § Rod based o Less photoreceptors to one ganglion cell – lower convergence § Lower sensitivity – higher acuity (higher resolution Needs more light to activate § Cone based (cones located in fovea) Receptive Field – DETECTS CONTRAST; the region of a sensory surface that when stimulated, causes a change in the firing rate of a neuron o let’s us know where the light is coming from and where light is not coming from; § let us know how big that light is and how big that dark is; § able to detect diBerences between light and dark o Lightness Constancy – contrast is diBerent under diBerent lighting conditions o Edge enhancement – the contrast of edges between light intensity are enhanced o Center Surround Receptive Fields § ON- center ganglion cell – shows highest amount of response (fires more) if there is light present in the CENTER of the receptive field and NOT in the surrounding If there is light in the surround and not in the center, it will fire less If light in surrounding and not in center – ganglion says there is not light here, it is inhibited, and it will inhibit its firing rate (lower response than baseline) If darkness in the center will inhibit If light in the center and surround the two eBects will cancel each other and will stay in baseline firing rate o Because has no contrast- no diBerence in center and surround because looking for boundaries and if there are no boundaries between center and surround will not respond § OJ-center ganglion cell – gives complimentary information to on-center cell; if there is light present in SURROUNDING of the receptive field and NOT in the center will fire more (be activated) If there is light in the center and not in the surround will fire less If darkness in surround will fire less Happens at the same time in diBerent cells and the cells can overlap in the same location (both on-center and oB-center in same location) o Baseline firing rate- neurons are always firing at a base rate; when gets activated fires more than baseline, when gets inhibited fires less than baseline PATHWAYS TO THE BRAIN – LEC 3 Left Visual Field – goes to right side of brain Right Visual Field – goes to right side of brain Nasal – near the nose (medial) o Receives input from Ipsilateral Visual Field (Same side as visual field) § Left Nasal à Left Visual Field § Right Nasal à Right Visual Field Temporal – near the side (lateral) o Recieves input from contralateral Visual field § Left temporal à Right visual field § Right temporal – Left visual field Contralateral – on the opposite side of space (relative to brain) o Visual information is always processed in the contralateral hemisphere § Relative to visual field not eye Ipsilateral – same side of space (relative to the brain) o Nasal is ipsilateral Optic chiasm – where some fibers cross the brain o Nasal section – that is why it is ipsiateral Lateral Geniculate Nucleus (LGN) -Ganglion cells project to structure in thalamus and has 6 distinct layers; all have center-surround receptive fields similar to rential ganglion cells o Magnocellular Layers – higher sensitivity; highly sensitive to motion; receives input from parasol ganglion cells § Layers 1-2 o Parvocellular Layers -higher resolution, acuity; color pattern, texture, and depth § Layers 3-6 § Receives input from Midget ganglion cells o Information from LGN projects to primary visual cortex § Travels via optic radiations o Koniocellular Layer – 6 layers; involved in processing color information; receive input from the last remaining ganglion cell type o The specific layers get their information from diBerent eyes § Layers 1, 4, 6 get info from contralateral eye § Layers 2, 3, 5 get info from ipsilateral eye Primary visual cortex (striate cortex or V1) – o located in the back of the occipital lobe o Organized topographically o Receptive Field in Striate Cortex § Responds more or less to diBerent orientation § Also responds to spatial frequency (how thick the line is) How thick is the pattern between dark and light § Many respond most strongly to moving lines, bands, or edges Some may only fire if motion is occurring in one direction Line has to present in same region of space in both eyes (binocular)  § Can be broken down to simple, complex and hypercomplex Simple Cells – respond most strongly to a bar of light with a particular orientation in a particular location (receptive field) – the more the line deviates from preferred orientation the less the cell will fire o As soon as it moves outside receptive field the cell turns oB o These cells have a preferred orientation that they respond to o Simple cells fires strongly if all LGN cells in retina are activated in a particular orientation § Fires more weakly if only some LGN cells are fired because light is landing in a specific location o EX: § Simple cell A responds maximally to lines at 90 degrees – as the line starts tilting away from 90 degrees starts firing less and less § DiBerent simple cells can respond to same line but will respond more or less and each have optimal orientation to fire maximally o Simple cells are: § ABected by contrast and orientation. ( a lot of simple cells respond maximally only to lines of a specific length – hypercomplex simple cells) If line is more transparent – fires less than when line is more bold § Combination of orientation and contrast causes simple cells to fire more or less Population Code*- a consistent diBerence in the patterning for the relative responses of a population of diBerent tuned neurons; responds to a wider area than simple cells o EX: One cell responds maximally at 90 degrees and one at 75 degrees § If look at both cells simultaneously both cells have a diBerent firing rate – that relative diBerence between them is consistent to a specific orientation no matter the contrast § The relative diBerence between the population of neurons is going to provide a code for individual features Multiple cells operate for individual features Complex Cells- will respond to a region of space, will respond anywhere within the receptive field; has a larger range of when it will fire o Will respond to a negative image (so a white dot on a black background) because less specific Hypercomplex cells – Will fire maximally if at a particular orientation and at a particular length (length and orientation matter) o If line is shorter or longer than that will increase or decrease their fire rate o Helps build complex shapes, tells you if a line stops at a particular locatio o A subclass of simple and complex cells (not its own thing) § Both complex and simple cells can be hypercomplex PATTERNS AND CONTRAST Spatial Frequency – number of cycles in a region of space Contrast – intensity of change in cycle  o 100% contrast = 100% black à 100% white Contrast Sensitivity Function (CSF) – combination of contrast sensitivity and spatial frequency to measure the absolute threshold of the smallest amount of pattern you can see o Can find what patterns we are most sensitive to o Find that sweet spot where we are able to detect diBerences between light/dark Tilt-after eJect – fatigue cells that are most sensitive to a certain orientation o Overwhelming them so they stop firing because they get tired) so you stop being able to see that line for some time (pattern type) until the cell o Demonstrate selectivity of cells in V1 to orientation Spatial-Frequency Channels – brain takes the patters on light made up of diBerent spatial frequency information that your brain puts together to make complex information (like faces) Patterns – alternating patterns of dark/ light can vary among a number of dimensions o Frequency o Orientation o Contrast Retinotopic mapping – creates a map of that area of space, organization of space in the way that cells organize themselves OBJECT RECOGNITION – LEC 4 Problems of Object Recognition 3 computational problems of object recognition: o How do we determine that something is an object (identification) § Stimulus (Pattern) on the receptor (retina) is ambiguous § Perception is subjective, and some stimuli is more ambiguous than others Brain wants to solve ambiguity Brain has to decide which one is more likely – latch onto interpretation o How do we tell that something is an X (chair, face, etc.) despite huge changes in appearances (recognition) § Pattern varies as a function of position/lighting – can be in many diBerent positions o How do we tell things apart despite similarity in visual image? (discrimination) § Relevant patterns must be distinguished from irrelevant ones (scenes are cluttered) Inverse projection problem – an infinite number of stimuli can combine to make the 2-D image that projects onto the retina o How to interpret the correct “one”  Feedforward/ bottom-up – process that happens starting with stimulus and moves forward- without influence from higher levels (past experience, memories) Feedback/ top-down – process at early stages is influenced by processing at later/ higher stages - using past experiences and memory to influence perception of objects Perceptual Organization- Steps As we go from early to later stages of processing, we fill in more and more, the image becomes more sophisticated and we create more details 1. Edge Detection – cells in V1/striate cortex respond to edges (lines) of a specific orientation which can define the boundaries of an object o Edge detectors – edge detection not perfect, when background and figure similar- or no diBerence in amount of lightness/ darkness between background and figure 2. Figure/ground segregation – have to figure out which is figure (object) and which is background (which regions belong to either o Surroundedness – the thing that is surrounded is more likely to be the figure o Size – smaller images are more likely to be the figure o Symmetry – symmetrical region is more likely to be the figure o Parallelism – regions with parallel counters are more likely to be the figure o Border ownership – V1 detects borders BUT V2 assigns borders to figure/object 3. Group together similar regions -Texture Segmentation/grouping – parsing information about textures into separate aspects of the image Gestalt Laws – grouping aided by Gestalt laws (wholes is greater than sum of parts) o Law of similarity- similar features are likely to be part of the same object o Law of proximity – nearby features are likely to be a part of shared object o Law of good continuation 4. Fill in missing edges and stimuli o Edge Completion -the visual system extracts where edges are likely to be, even when they are not physically present o Can perceive the presence of edges even if they do not exist in the image because cells V2 Cells – does a lot of the things V1 does but assigns borders to figure/object o Responds diBerently depending on the light/dark part is part of the object or if its part of the background § Helps identify if the dark part if part of a figure or ground o V2 CELLS FILL IN GAPS ( if line has good continuation) OBJECT RECOGNITION V4 Neurons o Greatest responses can be to straight or curved lines o Preferred orientation but can relate to the counter of the line  o Preferred location, but much larger receptive fields (covers a larger region of space) Grandmother Cell Theory – we have one cell dedicated to recognizing each object (we have a cell specific to recognizing our grandma) o Problems with theory: § Computationally demanding – using too many cells § Inflexible – seeing a picture of grandma when she was younger, but cell only recognizes your grandmother now § Not robust – what if grandma cell dies? – can’t recognize grandma o Cells can be tuned to very specific stimuli § Cells that respond primarily to humans and similar things to human faces § Might be cells that respond very strongly only to specific individuals Brain is separated into two diBerent streams (rods vs. cones) - paths stay separated and go to diBerent areas in cortex - Dorsal Pathway – “where/how”, go dorsally into parietal cortex in parietal lobe Ventral Pathway – “what” pathway, goes into inferotemporal cortex in temporal lobe Ungerleider and Mishkin (1982) o Lesioned diBerent cortex’s o Monkeys performed Landmark task where they have to find food in a bin close to a landmark § Monkeys with Lesion in parietal cortex could not perform task o Monkey performed food IN bin under square object and not in triangle (Have to know “What” is a square and “What” is a triangle to find food) § Monkeys with lesion in inferotemporal cortex could not perform this task Milner & Google (1991) o Patient could not recognize object but could reach out and pick them up just fine (only visual was aBected not touch) § Had to hold up letter in same orientation of the slot § Patient D.F could not hold up the letter at the right orientation But when told to just put in the slot could do it just fine (Dorsal Stream not damaged) § D.F’s Lateral Occipital Area was damaged – which is part of the Ventral Stream – so unable to recognize the “what” visually Lateral Occipital Area/ Complex – damage to this region results in visual agnosia o Part of the ventral stream o Has very large receptive fields (position invariance) o Cue/feature invariance o Visual Agnosia – inability to perceive objects § Can interact with the world because dorsal stream is intact  Fusiform Face Area – responds primarily to images of faces o When damaged people cannot recognize individual faces (prosopagnosia o Region specialized for processing faces § Something special about face recognition – Evidence for modular coding o Face processing is diBerent from other types of object processing o Face inversion eBect – only exists for faces § When faces are inverted cannot recognize them as well – recognize faces as other types of objects Modular Coding/ Modularity – representation of an object (or concept) is coded by a module, a region of the brain specialized for representing specific objects Distributed coding – representation of object occurs through regions of brain (no specialized area) Greebles – o Presented participants with novel stimuli – creatures called Greebles that all have similarish features but just diBer a bit § Got people to become greeble experts o After people were trained to become greeble experts there was activation in the FFA § Compared to Greeble Novices which had no activiation in FFA o Implies FFA might be important for fine detail processing and not specific faces, just things we are extremely recodnized with § Maybe it’s a Fusiform Expertise Area and not Fusiform Face Area Face Recognition o Face Recognition § Recognize faces “holistically” as a whole Not true of other objects § When Fusiform Face Area is inhibited can no longer process faces holistically § Could also be specialized for expertise FFA activation is experts for things they are an expert in: o Birdwatchers with birds o Car experts in cars Dairy farmers with proponasignia have trouble recognizing their cows faces LGN (center-surround receptive field, detect diBerences between light and dark àV1 (respond to lines, turn the diBerences in light and dark into edges – has small receptive field à V2 (respond to lines and expected lines – has small receptive field à V3 (not important à V4