Perception Study Notes PDF

PERCEPTION – STUDY DOC Lecture 1: Psychology (scientific), begins with perception Sensory perception: how matter becomes mind Lecture 2: Fechner's Law: what we subjectively perceive is the function of physical intensity perceived Plato: our senses guide us – innate reasoning Allegory of the c...

PERCEPTION – STUDY DOC Lecture 1: Psychology (scientific), begins with perception Sensory perception: how matter becomes mind Lecture 2: Fechner's Law: what we subjectively perceive is the function of physical intensity perceived Plato: our senses guide us – innate reasoning Allegory of the cave Theory of forms: - Plato: o A perfect triangle cannot exist in real life o The perfect ideas already exist in our innate reason Aristotle: form and matter are together They influence one another Rationalism: knowledge is gained through reason and logic (René Descartes) Empiricism: knowledge is gained through experience (John Locke) (David Hume) -> beliefs are caused by psychological habits Inductive reasoning: general conclusions from specific observations (generalize info) - More fragile Deductive reasoning: premises, conclusions - More logic BUT: infinite regress problem --> need to prove premises are true, by making other premises, and then proving those are true, and so on. (John Locke) - Locke’s theory of ideas:  - Info enters as “simple ideas” (today = sensations). Then those simple ideas can be assembled to form complex ideas o Example: blue and triangle --> blue triangle Immanuel Kant: critique of pure reason - Some structures need to be there before we perceive info, but those structures are empty if no sensory info enters (kinda like a circular thing) **Noumenon: the thing in itself BEFORE: we could not believe psych as a science, since there was nothing to measure WEBER Just noticeable difference (JND): the smallest weight difference that we can perceive - 1/40 (Weber’s fractions) Discriminability: how easy it is to notice a small difference in terms of physical intensity - Low Weber fraction means high discriminability Panpsychism: everything material also has a mental aspect (Fechner) --> each JND is perceptually equivalent Lecture 3: If high K value, then high discriminability K: allows to account for different slopes of logarithmic functions for different senses We use physiological methods for sensation and computational methods for perception The 3 steps of sensation and perception: *ACTION POTENTIAL: electrical signal 1. Transduction a. Physical stimulus interacts with specific receptor on peripheral sensory neuron b. Neuron fires 2. Transmission / modulation a. Mod: the brain has capacity to increase or decrease the signal activity it receives  i. Thalamus 1. Receives info and dispatch where needed b. Synapse, cranial nerves somatic nerves Stanley Smith Stevens - How much more or less intense are this compared to that (electrical shocks) - Different stimulus either log or exponential o If smaller than 1: log o If bigger than 1: exponential Absolute magnitude ratings: how intense is a percept in relation with two absolute boundaries BUT PROBLEM WITH THAT because my pain is different than your pain, which is called interindividual variability Therefore, the solution is cross-modality matching - Cross-modality matching is a method of comparing the perceived intensity of stimuli across different senses. It can be used to study how different senses interact with each other. Generalized labeled magnitude scale: personal scale built for each person’s experiences from various senses Prothetic sensation: sensory experiences that vary in intensity or magnitude - Continuous scale - Additive - Pain, loudness, weight Metathetic sensation: sensory experiences that vary in quality - Pitch, color, taste  - Easier to study scientifically (qualitative) Difference threshold = JND Detection threshold: minimum intensity of a stimulus required for a person to perceive its presence The threshold is probabilistic! (difference for which the difference is EXPECTED to be perceived 50% of the time) (difference in stimuli intensity that will be perceived 50% of the time) Therefore, we use a logistic regression to ID JND (per se) - Method of constant stimuli o Very accurate o Takes a LONG time o Some data are not information - Method of limits o Faster, but less accurate - Staircase method o Even faster o More efficient - Method of adjustment o Faster o Less accurate o (Give participants full control) Lecture 4: Signal Detection Theory: - When making a perceptual report, you are in part making a decision - Useful across a lot of domains BOTH SIGNAL AND NOISE ARE STATISTICAL CONCEPTS Signal: true sensory info coming from the external world Noise: various physiological or psychological processes influencing our perception of that external stimulus in an unpredictable manner - Caused by spontaneous activity in sensory nerves - Spontaneous fluctuations (example: being tired) Response bias: conservative vs liberal  - Conservative: o Higher criteria o Say no more easily - Liberal: o Lower criteria o Say yes more easily Response bias: sensitivity (d’) - Sensitivity: ability to distinguish between signal and noise regardless of response bias - Higher sensitivity = higher discrimination - Criterion: decision threshold Lecture 5: Sometimes noise make us feel like there is a signal even if there is not Light: electromagnetic radiation that can be conceptualized as a wave of photons - In space: waveform - Hits the retina: photon Photon: quantum of visible light In normal distribution, light we experience is unpolarized, because all angles of polarity are there. Properties of light: - Light scattering: o Interaction with particles o Light deviates - Rayleigh scattering: o The shorter wavelength gets scattered o Blue color of the sky - Mie scattering: o Affects all wavelength o All directions o White / grayish appearance - Non-selective scattering:  o The longer wavelength o Uniform white - Light absorption: o Light energy taken by material that convert it to other forms of energy o Heat - Light reflection: o Light bounces o Specular reflection:  Smooth surface  Predictable direction o Diffuse reflection:  Rough surface  Many directions Transmission: passage of light where it continues to propagate (NO ABSORB NO REFLECT) Refraction: bending of light, change speed and direction The eye: - Cornea o Outer layer o Focus light onto the retina - Anterior chamber o Fluid-filled space between cornea and iris o Contains aqueous humor o Nourishes cornea and lens - Pupil o Regulates amount of light entering the eye o Attached to the ciliary muscle via zonular fibers - Vitreous humor o Help maintain eye’s shape o Help transmit light to retina o Fill the space between lens and retina - Choroid o Provides oxygen and nutrients to outer layers of retina - Sclera o Provides structural support and protection  - Retina o Photoreceptors cells convert light into neural signals Optical infinity: 20 feet / 6 meters or more of the eyes - Emmetropia: beyond 6 meters, lens is relaxed Accommodation: when lens changes shape to focus light on the retina for clear vision at different distances Focal length (f’): distance between optical center and its focal point (F’) *where the light gets focused* - Presbyopia: o Age-related condition (40 y/o) o Lens trouble to accommodate (Lose ability to focus on nearer objects) - Hyperopia: o Distant objects appear clearer o Shorter eyeball - Myopia: o Near objects appear clearer o Longer eyeball - Astigmatism: o Irregularly shaped cornea or lens o Blurred vision at all distances o Light is focused unevenly on the retina Helmholtz: perception is unconscious inference The retina: - Fundus o Back of the eye o Interior surface of the eye - Optic disc o Where optic nerve exits the eye o No photoreceptors, so BLINDSPOT o Where the blood vessels feeding the retina enter the eye - Macula o Responsible for detailed central vision o Reading, recognizing faces o Lot of photoreceptors, not a lot of blood vessels  - Fovea o Central o Lot of cones o Sharpest visual acuity o Color vision o MOST ACCURATE VISION HERE Central vision: tasks that require high visual acuity, limited to a visual angle of 2-3 degrees Visual acuity: clarity of vision Visual angle: the angle formed by an object at the eye used to quantify how large an object appears in the field of view - Ganglion cells o Receive visual info from bipolar cells o Transmit to brain via axons - Bipolar cells o Connect photoreceptors to ganglion cells - Photoreceptors o Detect light and convert it into electrical signals o Rods: sensitive to low light levels, night vision o Cones: sensitive to bright light, color vision - Inner segment: o Cell nucleus o Synaptic terminals - Outer segment o Stack of disks packed with light sensitive pigment molecules, called photopigments --> responsible for photo transduction Phototransduction: photoreceptors convert light into electrical signals to be processed by the brain Photopigment: light-sensitive molecule composed of opsin and chromophore - Opsin: determines wavelength sensitivity, enabling color and light detection - Chromophore: light-absorbing molecule Lecture 6: Photoisomerization: when 11-cis retinal chromophore changes shape to all-trans retinal when exposed to light, which initiate phototransduction --> photoreceptors are bleached, so cannot absorb light Photopigment regeneration: converting all-trans retinal back to 11-ces retinal --> photoreceptors recover from bleaching (happens in the retinal pigment epithelium) Cones: 1. S-cones a. Responsible for our perception of blue 2. M-cones a. Responsible for our perception of green 3. L-cones a. Responsible for our perception of red The duplex retina is because the difference in light intensity between night and day is very large Photopic vision: - Under well-lit conditions - Cones - Color, higher visual acuity Scotopic vision: - Under low-light conditions - Rods - High sensitivity to light Dark adaptation: when eyes adjust to low-light conditions, increased sensitivity of rods. Can take up to 30 minutes 3 mechanisms to allow us to see dimly lit: 1- Pupil dilatation a. Entry of more light b. Fastest, but effects limited 2- Gain in light sensitivity of photoreceptors a. Darker environments = more regeneration b. Cones: around 5-8 minutes c. Rods: around 25 minutes d. Rod-cone break: after 7-8 minutes, vision dominated by rods  3- Lateral inhibition a. Active neurons suppress activity of neighboring neurons to enhance contrast b. General principle: subtracting and dividing by the average luminance (ganglion cells) Receptive field: stimuli influence neuron’s firing rate 1. ON-center / OFF-surround 2. OFF-center / ON-surround 2 types of bipolar cells as well. Receptive fields and lateral inhibition 1) Light hyperpolarizes 2) ON-center bipolar cells reverse the sign of the cone 3) Dark depolarizes surround cones 4) Horizontal cells activate and inhibit the cones connected to them 5) Amplifies ON bipolar cells, which amplifies retinal ganglion cell activity Hermann Grid example. Lecture 7: Methods to measure visual acuity 1. Distance (optometrists) a. 20/20 vision b. 20/15 c. 20/40 i. A person can see at 20 feet what someone with normal vision can see at 40 feet ii. When second number is over 20, vision is impaired 2. Vision scientists a. Smallest visual angle of a cycle of grating b. Visual angle: size of stimuli by how large the image appears on the retina i. Function of both its actual size and distance from the observer ii. Most people: 1/60 c. Cycle d. Better vision = smaller visual angle required to ID a grating cycle - Cones in the fovea have an average center-to-center separation of 0.5 arc minute (1/120 degree)  - We need 3 photoreceptors to have a pattern we can repeat - Distance between far left and far right in a full cycle (1/60) - In low contrasts environments: approx 7 cycles/degrees - Frequency of pattern: # of cycles within one degree o High frequency: details of visual stimuli o Low frequency: general layout - Sine waves: simplest pattern we can repeat - Square waves: can be decompose into sine waves Convergence: how many photoreceptors are connected to retinal ganglion cells - High convergence in periphery: rods synapse on diffuse bipolar cells, which synapse on parasol ganglion cells (or magnocellular / M) - Low convergence in the fovea: single cone cells synapse on single midget bipolar cells, which synapse on single midget ganglion cells (or parvocellular / P)  Low convergence = higher visual acuity  High convergence = higher sensitivity to light From the eye to the brain Optic chiasm structure: - Front of hypothalamus - Where half of optic nerve fibers from each eye go to the contralateral brain hemisphere o ***visual FIELD*** - Temporal retina: on the side of our head - Nasal retina: the one that crosses to the other side Optic tract: - Retinal projections beyond optic chiasm - Synapse in LGN 3 visual deficits: 1. Hemianopia 2. Left eye anopia  3. Tunnel vision Lateral Geniculate Nucleus (LGN): - In the thalamus - 6 layers Magnocellular layers (1 & 2): - Input from parasol retinal ganglion cells - Process peripheral vision Parvocellular layer (3-6): - Input from midget retinal ganglion cells - Process central vision Koniocellular layers: - In intralaminar regions of LGN - Color perception Optic radiations and V1: - LGN axons form optic radiations - Then they project to V1 Retinal projections to the superior colliculus - About 10% project to SC - SC: retinotopic layout *Blindsight perception: damage to V1 - Unconscious visual perception Lecture 8: Visual angle: measure size of the object in visual field regardless of its absolute distance or size Retinotopic mapping: - Spatial organization of visual field preserved in the brain, because of neighboring areas of retina and V1 mapping Central vs peripheral vision: - More cortical space in V1 for central - Higher density of ganglion cells in fovea - LGN: 2x more parvocellular layers - Cortical magnification: central 10 degrees of visual field occupies 50% of V1 surface area Retinal ganglion cells are sensitive to frequency, but not orientation Orientation of lines detected when combining info from retinal ganglion cells Tilt after-effect: - Neurons specialize in certain frequencies and orientations - Adaptation Hypercolumn: block in V1 to look after everything the visual cortex is responsible for - Contain cells responding to every possible orientation Simple cells - Respond to light more intensely when orientation matches receptive field - Tuning curves Complex cells - Detect motion in receptive fields - Selective for line orientation and movement direction Receptive fields properties: - Larger and less well-defined than simple cells - Some span a whole hemifield Specialized complex cells: - End-stopped cells o Respond to moving bars of a specific length that end within their receptive fields o Detect angles, corners, boundaries Monocular cues: - Pictorial o From static image o Occlusion: when an object partially blocks another o Accidental viewpoint: line of sight that creates an ambiguous depth interpretation o Relative size: comparison between items without knowing absolute size of either one o Familiar size: comparison when we know the absolute size of one object o Relative height: for objects touching the ground, those higher in the visual field appear to be farther away  Objects that are further are seen with a wider angle relative to our body o Texture gradient: pattern that repeats o Linear perspective: parallel lines appear to converge (ancien miroir salle de bain)  Vanishing point: apparent point where parallel lines converge  Combination of relative size and height o Aerial perspective: light is scattered from the atmosphere o Shading: variations in light and shadows  Since we assume light comes from above, the circle with the bottom shaded will appear closer than the one with top shaded - Dynamic o Movement of images o Motion parallax: images closer move faster o Optic flow: apparent motion of objects in a visual scene produced by the relative motion between the observer and the scene RELATIVE HEIGHT: Relative Height: Things at a distance look like their base is higher. Lecture 9: Binocular cues: - Oculomotor depth cues o Vergence  Convergence = near objects  Divergence = distant objects o Accommodation: ciliary muscles adjust lens shape for focus o Absolute depth perception o Vergence limit (2 meters) o Accommodation limit (6 meters) - Stereopsis o Impression of depth by both eyes o Binocular disparity: the difference in images in right vs left eye o Vieth-Muller circle: imaginary circle, corresponding retinal points in both eyes = no binocular disparity o Horopter: where objects project images onto corresponding retinal points in both eyes o Panum's fusional area: slight binocular disparity can be fused by the brain to create one  Within: single  Outside: double (diplopia)  o Crossed disparity: object closer than point of fixation o Uncrossed disparity: object farther than point of fixation o *Most neurons are tuned for zero disparity, but there are neurons for all disparity* o Stereoscope: presenting one image in one eye and another in the other o Correspondence problem: which bit of the image in the left eye should be matched with which bit in the right eye  Recognize object before binocular integration  Integration is more automatic, then we recognize o Random dot stereogram: hidden object we can only see with both eyes o Binocular rivalry: competition between two eyes to have control of visual perception Lecture 9 (continued – material that was not on midterm 1): Color perception Color: mental property Qualia: how things are perceived subjectively - Hard problem of consciousness The inverted spectrum states that the colors one sees aka one’s qualia are systematically different from the colors the other person sees Mary's room thought experiment - Goal: to prove that qualia matter - Support dualism and non-physicalist views - Support the idea that she learned something subjective Lecture 10: The principle of univariance: some sets of wavelength and intensity combinations can result in the same response, which is why we need many types of photoreceptors, since one type only cannot distinguish based on the wavelength - A single photoreceptor cannot distinguish between: o A bright but less preferred wavelength o A dim but highly preferred wavelength Trichromacy: color of any light can be recomposed and defined in our visual system by the combination of red, blue, green 3 cones -> for every wavelength, there is a specific pattern Color-anomalous: term for color-blind - Deuteranope: absence of M-cones (trouble distinguish red and green) - Protanope: absence of L-cones (trouble distinguish red and green) - Tritanope: absence of S-cones (trouble distinguish blue and yellow) - Cone monochromat: only one type of cone, true color-blind Metamers: different mixtures of wavelengths that look identical Additive color mixing: creating colors by combining different wavelengths of light - Green, red, blue - Combined = white Subtracting color mixing: creating colors by removing / absorbing certain wavelengths of light - Cyan, magenta, yellow - Combined = black Nonspectral hues: can only arise from mixing wavelengths - Purple Ewald Hering’s Opponent color theory supports the opponent-process theory where colors are processed in pairs (red vs green and blue vs yellow) - Legal and illegal colors - Legal: o Bluish-green (cyan) o Reddish-yellow (orange) o Bluish-red (purple) - Illegal: o Reddish-green o Bluish-yellow Support: - Hue cancellation experiments o Participants adjust the amount of the opponent color until no trace of the original hue remains Lecture 11: guest lecture Object recognition: - Fundamental for survival and interaction with our environment - Challenges: o Variability of objects  Example: recognizing a mug that we have never seen o Context o Lighting conditions  Example: the dress Template theory: the visual system recognizes objects by matching with an internal representation in the brain - We’re able to recognize these cows because of our template of cows Exemplar theory: compare new input to past experiences Generalized context Model (GCM): metrics for computing similarity - You compare new input to stored examples and assign category based on similarity Prototype theory: forms an average of a category of an object General recognition theory: - Categorization based on multivariate signal detection theory - Focus on how perceptual distributions influence decision-making - If very similar features, harder to differentiate and vice-versa  - Example: o When seeing a new face, you rely on perceptual dimensions to decide Recognition by components: - Geons can make up any objects - BUT it cannot handle the variability of objects Grandmother cell theory: - One single neuron for every single concept in the world - Example: one single cell responsible for recognizing your grandmother Deep Neural Network (DNN): - Neural networks trained to recognize objects - Overtime, with feedback, those networks can recognize objects that they were not originally trained on  Retinal ganglion cells and LGN detect spots  Primary visual cortex detects edges and bars To transform those in objects and surfaces, we need: - Intermediate-level vision: group features into contours, textures and surfaces o Perception of edges and surfaces o Determine which regions should be grouped o Between low-level (PS: edges and contrasts) and high-level o Humans are more effective than computers to detect edges - High-level vision: recognizing shapes, objects and categories PS: we detect object edges because of our neurons in V1 are orientation-selective Figure-ground segregation Illusory contour: - Our minds are filling the gap Gestalt theory: the whole is greater than the sum of its parts 1. Similarity 2. Proximity a. Parallelism  b. Symmetry 3. Good continuation 4. Closure 5. Common fate (example: birds flying) 6. Figure ground 7. Common region 8. Connectedness Fun fact: camouflage is used to confuse the observer (taking advantage of Gestalt) Gestalt used for ambiguity and perceptual committees The 5 principles of intermediate vision: 1. Group what should be grouped together 2. Separate what should be separated 3. Use prior knowledge 4. Avoid accidents 5. Seek consensus and minimize ambiguity Lecture 13: guest lecture 2: The what and the where pathways Dorsal = where: - Processes locations and shapes - From the occipital lobe to parietal lobe - Spatial awareness Ventral – what: - Processes object names and functions - From occipital lobe to temporal lobe - Object recognition The lateral occipital complex: more responsible for objects - Shaped-defined objects - Figure-ground segregation The fusiform face area: - In the fusiform gyrus of the ventral temporal lobe (usually right hemisphere)  - Tuned to faces, but evidence of expert-level recognition - Damage = prosopagnosia The parahippocampal place area: - Tuned to places - Dedicated scene-processing region - Provides a functional link between vision and spatial cognition Context plays a major role in object recognition IT neurons demonstrate invariance (respond to an object regardless of its size, position, or viewpoint) which suggests that IT neurons encore more abstract representations of objects Decoding methods: - Collect many fMRI scans of participants viewing multiples known categories - Computer recognizes brain activity patterns - Test participants if they can recognize an unseen image based on pattern Encoding methods: - Collect many fMRI scans of participants viewing multiples known categories - Define a feature space - Show how each features contribute - Once trained, encoding methods can predict responses - Example: voxelwise Second order isomorphism: similar objects must have similar representations in the mind Individually unique representations: only work with objects you are familiar with The brain recognizes objects quickly Lecture 12: Sound comes from pressure fluctuations in the air – anything that moves tend to produce noise Sound pressure (Pascals): measure force Loudness: sound intensity - Measured in dB - 0 dB doesn’t mean no sound, it represents the minimum audible level Logarithmic scaling: +10dB = 10x increase in intensity Pitch: psychological aspect of sound related mainly to the fundamental frequency Frequency (Hz): number of cycles per second - Pure tones = one frequency Equal-loudness curve: how our ears hear different frequencies at different loudness levels Harmonic spectrum: spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency Fundamental frequency: lowest frequency Timbre: psychological sensation which helps us state that 2 sounds with same loudness and same pitch are different The ear: Auditory canal: directs sound waves from outer ear to eardrum Tympanic membrane (eardrum): separates the outer ear from the middle ear and transmits sound vibrations to the ossicles Ossicles: 3 small bones in middle ear (malleus, incus, stapes) and amplify and transmit vibrations to the inner ear Cochlea: fluid-filled structure in the inner ear that convey vibrations into neural signals Oval window: connects middle ear to cochlea, transmit vibrations to the ossicles Round window: in the cochlea, helps relieve pressure from sound waves traveling through cochlea fluid Cochlear (auditory) nerve: nerve carrying info from cochlea to the brain for sound processing Organ of Corti: on the membrane of the cochlea, composed of hair cells and dendrites Basilar membrane: vibrates in response to sound and support hair cells Tectorial membrane: interacts with hair cells, help with transforming vibrations into electrical signals Hair cells: sensory receptors cells that transform vibrations into electrical signals and ship them to the brain via the auditory nerve Fun fact: longer wavelengths travel better (lower frequencies) Temporal coding: neurons systematically fire at a given time point in the cycle Volley principle: even if the auditory nerve can’t keep up, its team has its back Lecture 14: guest lecture: Tonal and vocal audiometry: measure how good or bad someone’s hearing is Hearing aids: - In-the-ear - Behind-the-ear - Directional microphones - Noise-cancelling algorithms Hearing implant: cochlear implants: - Shoot electricity on the nerve - Design with clear place coding Candidacy for cochlear implants: - People who only hear when higher than 60dB - People who can only repeat 60% of speech (speech recognition) If don’t qualify, then hearing aids Some people would need both --> electro-acoustic stimulation (EAS) - A mix of low frequency and high frequency Profound sensorineural hearing loss: basically, totally deaf - Cannot hear below 85dB - Qualify for cochlear implants On average, a cochlea is 35mm long, but implants are between 18-31 mm long. In the 18-24 mm electrodes user: people record more high-pitched sounds (Mickey Mouse), when just posed the implant, but after 4-8 years, they report the same number between users of 18-24 and users of 26-31 - Suggests that patients got used to the Mickey Mouse voice --> brain plasticity Anatomy-based fitting: - Improves speech recognition in BILATERAL CI USERS o In quiet AND in noise - Improves speech recognition in CI USERS WITH SINGLE-SIDED DEAFNESS o In noise o NOT in quiet - Improves speech recognition in unilateral EAS USERS o In quiet for patients newly implanted with it - Partial alleviation of hearing handicap in bilateral deaf patients using a unilateral CI o Results are mixed - Improves music perception in BILATERALLY DEAF PATIENTS USING A UNILATERAL CI o Subjective quality rating of music samples o Melodic contour identification o Familiar song appreciation Single-sided deafness = good reference point of hearing, so for them to hear well, the implant must be placed at the right place ----> PLACE CODING IMPORTANCE - Hearing handicap: o Speech recognition deficit in the ipsilesional hemifield o Speech-in-noise recognition deficit o Sound localization deficit o Listening effort (more cognitive load)  Measured with pupillometric Time coding of sound - < 1000 Hz Fine structure processing (FSP): - Fails to o Improve speech recognition o Improve melody discrimination o Localization - Enhances musical perception Sensory deafferentation: phantom limb pain Tinnitus handicap inventory (THI) Lecture 15: Color constancy: our brain discounts the illuminant by estimating the light source and adjusting our perception to maintain stable colors. - Even when lighting conditions change, we perceive objects as having the same color - We can play with the illuminant and change the illusion Movement perception - Spatiotemporal event - Essential for visually guided actions, as we interact with the world through movement  - Akinetopsia: neuropsychological disorder, no perception of motion at all o Lesions of MT/MST Apparent motion: illusory impression of smooth motion from a rapid alternation of objects, rapid succession - Distance and time Definitions of apparent motion. an optical illusion of motion produced by viewing a rapid succession of still pictures of a moving object. “the cinema relies on apparent motion” synonyms: apparent movement, motion, movement. optical illusion. Apparent motion - Definition, Meaning & Synonyms - Vocabulary.com Vocabulary.com https://www.vocabulary.com › dictionary › apparent mot... What best describes apparent motion? Apparent motion is a fascinating aspect of visual perception where our brains create the illusion of movement from static images. This phenomenon is crucial for understanding how we process visual information and interpret the world around us.Aug 20, 2024 Apparent motion | Perception Class Notes - Fiveable Motion detection circuit (Reichardt detectors): 1. M neurons would respond to 2 different changes 2. Solution: add a D neuron with incorporates delay a. Sensitive in motion direction b. Makes us sensitive to temporal info Aperture problem: difficulty to ID the direction of motion when focusing on the aperture Correspondence problem: don’t know how to match features in frame 1 and features in frame 2 To determine which direction, we can look at several local apertures, since only one option will be the right one. Types of eye movements: 1. Smooth pursuit  a. Voluntary tracking an object that is moving 2. Saccade a. Both voluntary and involuntary b. Rapid c. 3-4 times every second 3. Vergence a. Voluntary and involuntary b. 2 eyes move in opposite directions i. Convergence = inward ii. Divergence = outward 4. Reflexive eye movements a. Automatic and involuntary 5. Microsaccade a. Involuntary b. Small jerklike c. Functions: i. Prevent visual fading ii. Allow us to see behind blood vessels iii. Improve visibility of sharp details iv. Compensate for the sudden loss of acuity a few minutes outside the fovea Seeing is not passive!!! Saccadic suppression: temporary reduction of visual sensitivity to prevent motion blur and maintain visual stability Visual fading: complete loss of the environment before your very eyes - Someone tested it on themselves by injecting something to stop the eye movement Lecture 16: Cochlear nucleus: first to receive auditory signals from cochlea Superior olive: compare timing and intensity between ears Inferior colliculus: plays a role in reflexive responses to sound Medial geniculate nucleus (MGN): relay station, transmits to primary auditory cortex Primary auditory cortex: process and interpret sound info, in temporal lobe Tonotopy: spatial organization Belt region: secondary auditory, process more complex sounds Parabelt region: higher-order, complex sounds as well (loke speech) The where pathway = dorsal – location and movement The what pathway = ventral – ID Sound localization: Azimuth: angle - Interaural time difference: difference in time between each ear o Coincidence detector neurons - Interaural level difference: difference in intensity HOWEVER: cannot tell us how far an object is Inverse square law Auditory distance perception: - Cue 1: spectral composition of sounds o Propagation of sound = distal sounds vs direct energy Cones of confusion: sounds can come from 2 places on the cone - Solution 1: move head - Solution 2: shape of pinna Auditory stream segregation - Frequency / pitch - Time - Timber - Onset Continuity effect: even with interruptions, can hear a continuous sound if gap is filled with noise Restoration effect: even with interruptions, can hear a sentence if gaps filled with noise Lecture 17: Phoneme: unit of sound Speech production: 1. Respiration: a. Diaphragm pushes air out of lungs through trachea until the larynx 2. Phonation: a. Process where vocal folds vibrate in the larynx 3. Articulation: a. Act of producing speech using vocal tract Humans can change the shape of their vocal tract = articulation - Peaks in speech spectrum = formants Coarticulation: (anticipation of next letter) - Fast speech production: 10-15 vowels and consonants per second Mcgurk effect: - Motor theory of speech perception: kinda lip reading - What someone sees affect what they hear Infants filter irrelevant acoustics long before they start to make speech sounds Wernicke's area: - Aphasia: o Lose language comprehension Broca's area: - Aphasia: o Cannot produce speech Sound qualities: Tone height: correspond to level of speech, relate to frequency Tone chroma: shared by tones having same octave interval Octave: interval between 2 sounds frequencies having a ratio of 2:1 - 10 octaves within audible range - Piano: 7 octaves Consonance: combination sounds pleasant - When frequency = simple ratio Dissonance: combination sounds unpleasant - When frequency = complex ration Scale: particular subset of the notes in an octave - Major scales sound happy – PARTY DU JOUR DE L’AN - Minor scales sound sad – FAVE DEPRESS Key: subset of notes from the scale Melody: sequence of notes perceived as single coherent structure - Contours: pattern of rises and declines in pitch o Recognizing a melody is like recognizing a face Music is mostly processed in the right auditory cortex Congenital amusia: - Born with difficulties perceiving music - (slide 28) o Amusics have normal ERANs (-) but have no P600 (+) - Anomalies in right frontotemporal network involving inferior frontal gyrus and superior temporal gyrus Absolute pitch: - Very rare - Ability to accurately name notes without comparison to other notes - Ability to perfectly name any musical note - Genetic component (monozygotic twins even better than dizygotic twins) Lecture 18: René Descartes: passion of the soul, immaterial souls The somatosensory cortex is close to the motor cortex Proprioception: sense of body position, sense of balance Kinesthesia: perception of movement Tactile perception: touch, exteroceptive sense (outside the body) Thermoalgesia: temperature and pain, interoception (inside the body) Nerve fibers: - Touch = larger - Pain = smaller Tactile perception: touch, exteroceptive sense (outside the body) - SA I (Merkel) o Small receptive field, slow adaptation rate o Reading brail o Texture perception - SA II (Ruffini) o Larger receptive field, slow adaptation rate o Only in hands – finger position o Can perceive skin deformation - FA I (Meissner) o Small receptive field, fast adaptation rate o Holding grip onto objects (stable grasp, climbing) o Surface of skin - FA II (Pacinian) o Large receptive field, fast adaptation rate o Sensitive to high frequency vibrations o Fine texture perception (writing with a pencil, control pencil with high precision) All touch fibers group together into a nerve entering the spinal cord Dermatoma: Dermatomes are areas of skin that connect to a specific nerve root on your spine Two-point discrimination threshold:  - Larger number = poor discrimination Pain: unpleasant sensory and emotional experience associated with actual or potential tissue damage - QUALIA Nociception: neural process of encoding nociceptive stimuli Nociceptive stimulus: actual or potential tissue-damaging event encoded by nociceptors - A-delta fibers o Myelinated o Sharp, rapid pain - C fibers: o Non-myelinated o Throbbing sensation Intensity (1) vs specificity (2): (1) Excessive sensory stimulation No specific neural system to perceive pain Use same systems as other senses (2) Certain neurons will respond to pain Local anesthetics: prevent NA+ to enter in NA+ channel, to block propagation of action potential. Need to block at least 3 nodes of Ranvier in myelinated fiber Congenital insensitivity to pain: - Don’t feel pain at all - Problematic because pain is there to protect us from injury o They don’t know where to stop, so hurt themselves Lecture 19: Limbic touch: kinda opposite of pain - Emotional response - Associated with C fibers 1st relay: dorsal horn of the spinal cord  - Spinothalamic pathway Commented [LC1]: 2 pathways to primary somatosensory cortex: Spinal projection neurons: Poorly localized information such as pain and temperature crosses over the midline in spinal cord, and 1. Nociceptive specific access the thalamus via spinothalamic tract. a. Respond to noxious stimuli Highly localized information such as fine touch uses the dorsal column of the spinal cord (stay on same side). 2. Wide dynamic range (more of them) From the medulla, crosses over to reach the thalamus. a. Respond to both innocuous and noxious stimuli Intensity (1) vs specificity (2): Periphery: seems to be specificity Spinal cord: seems to be a mix of specificity and intensity (things more complicated in spinal cord) - Pattern theory: o Specific pattern of activity across neurons o Not a specific cell that causes pain but rather a specific pattern of activity - Gate control theory: a pattern theory) o If struck the part where you’re injured, the pain slows down o T transmission neuron more activated by nociceptive C fibers than by tactile A fibers o T transmission neuron more activated when A & C fibers are active at the same time than when only A fibers o Associated with wide dynamic range neurons Transcutaneous electrical nerve stimulation (TENS): administer low intensity electrical current that will mask the pain Opioids: all kinds of drugs that can activate opioids receptors (like morphine) - Good at blocking the transmission of nociception at the level of the spinal cord (activation) Pre-synaptic neuron: prevents calcium from entering synaptic terminal, which reduce release of neurotransmitters into synaptic cleft Post-synaptic neuron: leaving potassium out, which hyperpolarizes the membrane, therefore difficult to depolarize --> nociceptive signal blocked in spinal cord Referred pain: when nociceptive signals from internal organ but don’t feel pain in that said organ - Example: heart attack Spinothalamic pathway = pain-nociceptive info Dorsal column pathway = tactile-touch info Brown-séquard syndrome: - Damage of one side of spinal cord, so unique pattern of deficits - Example: damage of right side o Loss of tactile sensation on same side of lesion BUT pain-temperature sensations remain Conditioned pain modulation --> pain inhibits pain Fibromyalgia: chronic pain disorder - Increase sensitivity to pain - Thought to result from abnormal pain processing within the central nervous system Increasing session vs decreasing session: - Less pain in fingertips in decreasing session because descending symptom is activated by full arm, and we have more inhibition - SAME RESULTS WITH FIBROMYALGIA Effects of emotions on pain: - Nociceptive flexion reflex (NFR):  o Involuntary spinal reflex o Triggered by potential harmful stimuli o Effects stronger when seeing unpleasant picture Lecture 20: 2 dimensions of pleasure: 1. Wanting a. Dopamine in frontal lobe b. Pleasure short-lived 2. Liking a. Opioids Motivation-decision model: everything that is more important will inhibit the sensation of pain Flow: state of intense focus Video games study: - Playing video games was more efficient to reduce pain compared to the 2-back task (working memory task), because of FLOW The pain matrix: - Affective dimension: o Anterior cingulate cortex o Unpleasantness of pain - Sensory dimension: o Somatosensory cortices Primary somatosensory cortex lesion: - Right side injured - Cannot perceive when administering painful thermal pain in left part of body - BUT: they sense vague unpleasantness coming from left side (able to report emotional sensation of pain) Phantom limb pain:  - 60%-80% of patients experience this - First days/weeks, tends to decrease over time - Almost completely absent in young infants - Proportional to degree of functional reorganization - FUN FACT: adjacent body parts invade part of the cortex used to be assigned to amputated region To counter it: 1. Mirror therapy 2. Prostheses L’homme sans douleur: anterior cingulate cortex lesion - He doesn’t feel pain - He isn’t afraid of injuries Even with cingulotomy, the pain comes back Hypnosis: people can change activity of their brain Neurosignature: pain has a specific pattern in the brain Lecture 21: We perceive our environment via physical and chemical interactions Physical senses: with external organs - Audition - Vision - Touch Chemical senses: direct connection - Taste - Smell - Trigeminal system Taste: - Interaction between soluble substances with gustatory receptors, in taste buds - Sweet - Sour  - Salty - Bitter - Umami Smell: - Via olfactory receptors in the olfactory mucosa - Millions of different odors - Volatile substances Trigeminal system: - Independent from smell and taste - Evokes sensations such as o Irritation o Burning o Freshness o Tingling Sensory organ of taste: - Taste buds found in the papillae of the tongue o THOSE THAT HAVE SOMETHING TO DO WITH SENSE OF TASTE  Fungiform papillae  Foliate papillae  Circumvallate papillae o SOMATOSENSORY OF THE TONGUE, NOTHING WITH TASTE  Filiform papillae The taste map is a LEGEND ---> NOT TRUE AT ALL Smell: - (compare noses with churches) - Olfactory receptor neurons (ORN): o Located in roof portion of nasal cavity o Receptors in their cilia o Surround by supporting cells o Can regenerate from stem cells The olfactory code: - Approx. 400 different types of olfactory receptors o Each ORN carries ONE type of receptor  o Each ORN can be activated by different substances o Each substance can activate different types of ORN - Different for everybody o Olfactory world smells different for people  Example: cilantro - We can distinguish billions of odors Axons of ORN pass through the cribriform plate of the ethmoid bone and reach the olfactory bulb Special things about smell: 1. No crossing over: left nostril = left hemisphere 2. No relay in thalamus 3. Only 2 neurons until reach the cortex 4. Brain regions are not exclusively for smell a. Orbitofrontal cortex = reward system b. Amygdala = fear c. Entorhinal cortex = learning and memory Memory: place travel - When smelling something, it brings you back to a specific place where you smelled that thing Orthonasal olfaction: through inhalation via nostrils - Retronasal olfaction: through exhalation via throat - Also, what makes us differentiate between an apple and a banana Functions of smell: 1. Warning a. Microbial threats = disgust b. Non-microbial threats = fear 2. Nutrition a. Detection and ID (less impo today) b. Expectancy violation  c. Intake regulation d. Breastfeeding 3. Communication Olfactory dysfunction: - Approx 20% of population has one - Quantitative dysfunction o Anosmia:  Complete loss of olfactory function  5% of pop o Hyposmia  Partial loss  15% of pop - Qualitative dysfunction o Parosmia  Odors perceived different than supposed to  30% of patients with hyposmia o Phantosmia  Perception of smells without of odor source  Very rare Main causes: - Diseases of nose or nasal mucosa --> 25-50% of olfactory dysfunction - Neurological diseases --> 15-35% (TBI, Alzheimer, Parkinson, congenital) - Unknown --> 15-35% - Age Olfactory dysfunction = marker of COVID Consequences of olfactory dysfunction: - Danger - Professional - Quality of life Lecture 22: (only 1-2 questions on this lecture) Visual deprivation: - Volume of grey and white matter is lower in people born blind - Increase in thickness of cortex - Increase in metabolism of visual cortex We can rewire the brain so that auditory cortex uses visual info. SUMMARY: Adaptive reorganization of neurons to integrate the function of 2 or more sensory systems Blind people are better at touch Tactile perception in the blind: critical period is before age 7 Study: found that blind people use visual cortex for tasks that are important for daily life activity SUMMARY: age and importance of task are important factors for functional changes in blind people SUMMARY: the 2 visual pathways are preserved, and they take over tactile functions Odor perception in the blind: when seeing a scary movie, recognize sweat from fear - Odors that differ between blind and sighted: o Fear o Disgust Taste perception in the blind: WORSE in blind people, because fewer exposure to different tastes, so more difficult to distinguish - Have less restrictions - Are less peaky - BUT: the pleasurable part of taste is not present Thermal and pain perception in the blind: - Detect the second pain better than sighted people - BUT: not the first pain, since there is not much room for improvement SUMMARY: 2 hypotheses for crossmodal plasticity 1- Cortical reorganization 2- Unmasking *Sensory substitution