perception Flashcards

Question

the use of visual electrophysiology

Answer 1

- Experiments normally performed on animals. - Tiny electrode placed close to (or sometimes inside) a visual neuron - Visual stimuli are presented to the animal (which is normally anaesthetized and paralyzed) - The electrical signals in the neuron are recorded - is a non-invasive technique that measures the electrical activity of the visual system, from the retina to the brain, to assess visual function and diagnose conditions affecting the visual pathway.

Answer 2

- help to shape ganglion cell receptive fields

Answer 3

-are the primary output neurons of the retina transmitting visual information from the eye to the brain via their axons, which form the optic nerve - respond with a series of nerve impulses - the more stimulation there is, firing rate increases - they respond to contrast between centre and surround, finds the intensity edges - encode opponents of colour (blue-yellow, red-green)

Answer 4

-Bilateral structure with 6 layers. -the relay station between the eye and the visual cortex Layers 1, 4, 6 receive info from the contralateral (opposite) eye, while layers 2, 3, 5 receive info from the ipsilateral (same) eye. - different colour channels in the different layers Retinotopic organization, encoding spatial position. Different channels: M pathway (motion), P pathway (fine details), K pathway (color).

Answer 5

6-layered structure in the occipital lobe, receives input from the LGN. - combines and analyses the visual information relayed from the LGN and transmits this information to the higher visual association areas (the extrastriate cortex), which provide further interpretation. -Processes basic features like orientation, motion, and color. - however function is still debated as very complexed, but we know we would be blind without it.

Answer 6

Receptive fields: simple cells (respond to certain orientations) - respond well to vertical lines but not horizontal complex cells (direction + orientation selective) end-stopped cells (length, moving angles and corners).

Answer 7

- different cells in V1 code different positions - orientation - spatial frequency (size of a visual feature) - binocular disparity (Difference in receptive field position between the eyes -helps in depth perception) - motion - colour

Answer 8

- beyond V1, the receptive fields get bigger and more specialised Includes regions specialized for more complex features - (e.g., motion detection in V5, face recognition in IT). V2 = colour, form, depth V3 = motion, form V4 = colour, shape V5/MT = motion, depth IT = complex form MST = motion in depth parrallel pathways: 1. action parietal pathway (dorsal) - is often called the “where” pathway, because it codes for the locations of objects and their movement 2. perception temporal pathway (ventral) - is often called the “what” pathway, as this pathway codes for object identification as well as color vision. - precise retinotopic position less important as receptive fields get bigger

Answer 9

Optic Nerve: Carries visual information from the retina to the brain. Optic Chiasm: Where the optic nerves cross; information from the left visual field goes to the right hemisphere and vice versa.

Answer 10

Similar to ganglion cells, with center-surround organization. The LGN does little processing but regulates the flow of information to the cortex.

Answer 11

Retinotopic Position: Maps the position of visual stimuli on the retina. Orientation: Responds to specific orientations of lines and edges. Spatial Frequency: Encodes the size of visual features (e.g., fine vs coarse details). Binocular Disparity: Encodes differences between the two eyes' views, helping with depth perception. Motion: Processes motion through V5 (specialized for motion). Color: Encodes color information.

Answer 12

Through differential activation of L, M, and S cones (responsible for different parts of the spectrum).

Answer 13

are interneurons in the retina that act as a crucial link, transmitting visual information from photoreceptors (rods and cones) to ganglion cells, which then send the signals to the brain

Answer 14

Scene: A real-world view of an environment containing background elements and multiple, meaningfully arranged objects. Objects: Items within a scene that are typically acted upon, unlike scenes which are acted within. natural scenes -> produced in the world

Answer 15

Used to transform features into objects: 1. Proximity – group elements that are close together. 2. Similarity – group elements that look alike together 3. Good continuation – perceive smooth, continuous lines or patterns.

Answer 16

Key for perceptual segregation—distinguishing object (figure) from background (ground). - how do we tell an object is in front of the other in an image -We detect details better in the foreground. -The element of the photo closest to you makes up the foreground. -The furthest element away from you is the background

Answer 17

- illusory contours are inferred by the visual system - sometimes the foreground object isn't actually there but our brain sees it (e.g. Kanizsa triangle): Brain "fills in" missing information to perceive whole shapes. - We see triangle floating, but isn't really there, is defined but the edges and shapes around it(background)

Answer 18

Superordinate: Broad (e.g. "animal") Basic: Default category level (e.g. "dog") Subordinate: Specific exemplar (e.g. "Border Collie") -Basic level is often used most quickly and easily in categorisation tasks.

Answer 19

Viewpoint Invariance: We store 3D, angle-independent representations Multiple Views: We store several 2D views/pictures and piece them together. what one is it? Do we store a single, viewpoint invariant representation of a given object or do we have a number of “snapshots” of the object from different viewpoints which together make the object representation up? 'pictures' from lots of different angles

Answer 20

A rapid, general description of a scene - (e.g. “beach” or “busy street”) - occurs within a fraction of a second.

Answer 21

1. Naturalness – natural vs. man-made. 2. Openness – visible horizon or not. 3. Roughness – number of objects (complexity). 4. Expansion – sense of depth/perspective. (looking into distance or not) 5. Colour – typical hues (e.g., blue sky = outdoors). - are the colours characteristics of a given location? - We make assumptions about the identities of objects in scenes depending on their size and location - Based on our experience of the world, we expect it to look a certain way

Answer 22

Indirect perception theories (Helmholtz, Gregory, Rock, Friston): We infer or hypothesis about the nature of the world based on experience. - these inferences can affect our judgement can lead to superstitious perception (seeing things that aren't there). Expectations shape what we see (e.g. ambiguous images perceived differently depending on suggestion). -If you tell people there is something there, they can still see it

Answer 23

Study of how place names reflect people’s perception of their environment. - how they conceptualize it E.g. names like "Squinty Bridge" reflect shared conceptualisation. - How people think about places using names

Answer 24

retina -> LGN -> V1 -> differs in complex pathways e.g V2, V3, MT, V4 Increasingly complex features processed along this "ventral stream" (aka the “what” pathway). - IT (inferotemporal cortex), and its sub-regions TE and TEO are seen as the end-point of the “ventral” or “what” processing stream

Answer 25

FFA (Fusiform Face Area) = Face recognition OFA (Occipital Face Area) = Face features PPA (Parahippocampal Place Area)= Scene/place recognition EBA (Extra-striate Body Area) = Body image perception VWFA (Visual Word Form Area) = Word/form recognition (related to reading, dyslexia)

Answer 26

Crucial for object recognition Includes TE and TEO, which are high-level object processing areas.

Answer 27

A neuron from the medial temporal lobe responding specifically to images of Jennifer Aniston. Suggests possible sparse coding in memory and recognition (but could be memory-related).

Answer 28

Perception is about affordances: what actions an object allows. We see objects in terms of what we can do with them.

Answer 29

It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought … It implies withdrawal from some things in order to deal effectively with others.”

Answer 30

Selective Attention: Focusing on specific stimuli while ignoring others. Divided Attention: Attempting to attend to multiple things simultaneously (e.g. driving).

Answer 31

-We can't process all stimuli — limited capacity. -Attention helps filter and prioritise important information. two types: 1. Exogenous (bottom-up):-Stimulus/environment driven - attention drawn by something happening around you (e.g. a loud noise). 2. Endogenous (top-down): Internally guided by the attender, trying to decide what to focus on (e.g. searching for your keys) - in the real world, normally a combination of the two is used

Answer 32

Illusion of rich perception: We think we see everything, but we don’t without attention. Exceptions: Faces can sometimes be perceived without attention.

Answer 33

Inattentional Blindness: Failure to notice events due to not attending to it (e.g. gorilla in basketball video). - especially in dynamic events Change Blindness: Large scene changes go unnoticed if attention isn't directed. - For example, observers often fail to notice major differences introduced into an image while it flickers off and on again. - can be alleviated if location of change is cued - motion IS sensitive to these changes- we can detect the change when the change moves

Answer 34

Seen in films due to: Inattentional blindness (within a scene). Change blindness (an error that occurs following a cut in the action).

Answer 35

- A theatrical analogy … but the meaning is clear - But … we can pay attention to - Things that are outside this spotlight - Objects as well as locations

Answer 36

the basic idea: Vision analyzes features separately (modular) e.g. color, orientation, motion Question: How are these features combined into a unified object? is attention the glue that sticks them all together?

Answer 37

Two stages: 1. Preattentive Stage: Features processed separately and in parallel. 2. Focused Attention Stage: Attention combines features to create an object. Without attention: illusory conjunctions (e.g. wrong feature combos). Supporting Evidence: -Experiments show people mix up features if attention is limited. -Treisman's anecdote: thought she saw a bearded man with a hat (actually two men).

Answer 38

Parallel Search / Pop-out: Fast detection of one basic feature (e.g. one letter o among all letter V's). - can be easily seen due to differences in orientation, motion direction, colour (seen effortlessly) Conjunction Search: Slow, effortful when target has combination of features (e.g. red "O" among red "X" and green "O"). - this requires sustained effort - is this attention? - need to look in detail at the image

Answer 39

Neural synchronisation may help explain feature binding. (coordinated firing of neurons) Gamma band synchrony: Neurons responding to same object fire in sync across regions. May serve as “glue” alongside or instead of attention.

Answer 40

Enhances perception: Faster responses to attended objects/locations Higher contrast sensitivity. (seeing more clearly) Enhances neural activity: Increased firing in visual areas (e.g., parietal cortex, V1 → MST).

Answer 41

Retina: Contains rods and cones. Eccentricity: Measures how far a stimulus is from the center of gaze. -As eccentricity increases (i.e., the point moves further from the fovea towards the periphery), visual acuity and processing speed tend to decrease. Fine detail seen in central vision (high cone density). Eye movements help bring areas of interest into the center.

Answer 42

Attention often follows where we look. Stimulus Salience Theory: We look at the most attention-grabbing parts of a scene - most salient objects (e.g., bright colors, motion). salience = the quality of being particularly noticeable or important; prominence. issues with salience: Works in controlled environments (e.g. computer screen), less effective in real-world tasks. (tend to look where the next action is)

Answer 43

Real-world attention is task/action-driven, not just salience-based. Tatler et al. (2011): Eyes go to task-relevant areas, not necessarily the most salient. - suggests that a simple salience model should be rejected

Answer 44

Autism: Eye movement patterns can differ. Some autistic individuals look at less socially relevant parts of scenes. May link to monotropism.

Answer 45

a theory of autism which has emerged fromautistic people's experience. Fewer, stronger interests are aroused and they attract more processing resources. Harder to shift attention between competing stimuli. Explains difficulty attending to multiple sensory inputs (e.g., looking and listening at once). a theory suggesting that autistic individuals and some people with ADHD tend to focus intensely on a small number of interests, experiencing a "tunnel of focus" and finding it challenging to shift attention to other things

Answer 46

Motion of Objects: Movement of objects in the 3D world changes the retinal image, and we typically perceive this movement as solid and coherent instead of a blurry mess. Motion of the Observer: When the observer moves, the retinal image changes differently, affecting how we perceive motion. The relative motion between the observer and object determines the perception of movement.

Answer 47

Motion detection involves measuring the image at one place and time and then comparing it later at another place and time. Velocity = Distance/Time. By knowing the separation and time delay, the speed of motion can be determined. Our perception of motion depends on the outputs of motion detectors (left and right detectors). - both left and right detectos arrive at the same time (via delay from left) This system helps us perceive motion. -How we see motion will depend on how these detectors are designed and implement

Answer 48

Phenomenon where we perceive motion even in stationary images (e.g., when squares in different corners appear to move when shown sequentially).

Answer 49

Motion may not always exist even though we perceive it (e.g., movies and illusory patterns) -simulate motion by "fooling" our motion detectors in the brain).

Answer 50

in motion tracking, the visual system needs to match elements from one frame to another. the challenge of determining which visual elements in one frame of a sequence correspond to which elements in the next frame solution: Nearest Neighbour Matching: The visual system tends to match elements based on the least motion and proximity. - It solves the correspondence problem by determining which image features correspond to each other across frames. (think of lecture example white squares moing on a black background)

Answer 51

- Moving in one direction - Can group based on similarity and proximity = when elements move in the same direction or at a similar pace, we perceive them as a group, even if they are visually separated, essentially meaning that things that "share a common fate" (movement) are seen as belonging together; - this is often observed in nature with flocks of birds or schools of fish moving in unison.

Answer 52

Motion detectors have small receptive fields, which can create ambiguities in perceiving motion the barber pole illusion: a rotating barber pole where stripes appear to move vertically, even though they are moving diagonally).

Answer 53

Optic flow is the pattern of retinal motion when moving towards or away from an object. It provides information about speed and direction (e.g., when driving or walking, it helps determine heading). a form of visual streaming which occurs as we are moving continuously in one direction. It occurs because the image of the same object(s) are constantly changing with regards to which area of the retina they stimulate.

Answer 54

1. i walk past, your eyes are still straightforward: moing object, retinal motion 2. i was past and you track me with your eyes vtrickier: no retinal motion, but still perceiee it 3. you moe yourself through the scene vveen tricker: lots of retinal motion, but no perceied motion of the world answer = corollary discharge

Answer 55

A neural copy of a motor command sent to the brain so that sensory feedback related to movement can be accurately interpreted. This helps prevent the perception of the world "jumping around" when we move our eyes or body. a hypothetical comparator compares retinal motion to the efferent signal from the eyes: v- if these signals are different, motion is perceied v- if these signals are matched, no motion is perceied * what our brain is telling our eyes to do - When you move your eyes, a corollary discharge signals other brain areas that your vision will be shifting, so you don't perceive the world as suddenly jumping around. - a copy of a motor command that your brain sends to other parts of itself, essentially giving them a heads-up about a movement you are about to make, allowing your brain to anticipate and interpret sensory feedback related to that movement accurately; it's like a notification system within your brain

Answer 56

We think that receptive fields in V5/MT are built up from component motion detectors with smaller receptive fields in monkeys: FST (fundus of superior temporal cortex) = actions MSTd (medial superior temporal dorsal) = self motion vMST (medial superior temporal cortex) = trajectories similar for humans with some differences in anatomical detail: hMT+/V5 - interactions between form and motion pathways - areas V3 (dynamic form) and posterior superior temporal sulcus seem important here vvv- recent experiments on inputs from estibular system to motion sensitie cortex

Answer 57

-Motion captured by attaching lights to joints of a human in a dark room. v- iewed in a fraction of a second -Observers perceive the motion of the person despite not seeing the person directly (only dots of light). -Rich information such as identity, emotion, and gender can be inferred from biological motion, even with simple light-dot displays. Still not clear how such simple displays are spontaneously organized and informative

Answer 58

Scrambling the dots that represent human motion makes it much harder to perceive the motion or recognize the person.

Answer 59

The Superior Temporal Sulcus (STS), specifically the posterior part, plays a crucial role in processing biological motion. Functional imaging can be used to study how the STS activates during biological motion perception. - different brain circuits engaged in autism for biological motion

Answer 60

Human vision is sensitive to wavelengths between 400-700 nm, which correspond to different colors. - We associate a particular wavelength of electromagnetic radiation with a particular colour sensation - But… - The rays to speak properly are not coloured. In them is nothing else than a certain Power and Disposition to stir up a Sensation of this or that Colour … so Colours in the Objects are nothing but a Disposition to reflect this or that sort of rays more copiously than the rest

Answer 61

- colours are not contained in the radiation itself - they are created by our visual systems, essentially arbitrarily ( how do we know the colour we see is the same as someone else's)

Answer 62

An optical illusion that demonstrates the perception of color without specific wavelengths.

Answer 63

The color of an object is determined by the wavelengths it reflects. - If object has a high reflectance of a particular wavelength, it tends to be that colour - the measurement of how much light a surface reflects at different wavelengths across the electromagnetic spectrum,

Answer 64

= by spectral distribution of reflected light

Answer 65

Object Identification: Color helps distinguish objects and categories if the 3D shape is the same (e.g., lemon vs. lime). - in some cases colour is diagnostic for a particular object class - even when colour is not diagnostic it can help us narrow down the search or identify specific example (looking for a red car) -Color perception can be influenced by expectations, such as the typical color of fruit or vegetables. (bannana is always yellow) -Prior knowledge of typical object colors (e.g., bananas are yellow) influences color perception and categorization.

Answer 66

Colour matching experiments: Any color can be matched by adjusting the relative amounts of red, green, and blue light. (3 primary lights with different spectral sensitivities) Three cone types: L-cones(long): Sensitive to red light M-cones(medium): Sensitive to green light S-cones(short): Sensitive to blue light - (blue sensitivity at the shortest wavelength(nm), then green then red) Physiology: The brain processes the outputs of these cones to perceive color. Trichromacy is based on the principle that colors are determined by the differential activation of these cones. - rods are x100 more sensitive and s cones are much less sensitive in absoloute terms

Answer 67

- the trichromatic system can be fooled by metamers definition = a light that looks the same as another light but the spectral content is completely different - Physically different light spectra that appear perceptually identical to the human eye. Example: The same cone activation can result from different wavelengths of light, such as in computer screens simulating colors. colors that appear identical to the human eye under certain lighting conditions, despite having different spectral power distributions

Answer 68

Afterimages: Viewing a color for a prolonged time induces an afterimage of the complementary color (e.g., yellow induces blue). Opponent color pairs: Red-Green Blue-Yellow Black-White Some authors have argued that it is possible to see reddish-greens and yellowish-blues Physiology: Opponent cells in the retina and LGN (Lateral Geniculate Nucleus) respond to color contrasts between these pairs - can combine opponent colours with trichromacy by combining the cone outputs - L-M mechanism (“red”- “green”) - (L+M) - S - mechanism (“yellow” - “blue”)

Answer 69

Ganglion Cells: Midget ganglion cells process red/green information, while other ganglion cells handle blue/yellow information. colour opponent ganglion cell: red on/ green off ( bright red, dimmer green) green off/ red on - cones feed into ganglion cells then LGN

Answer 70

This theory suggests that color perception is controlled by the activity of two opponent systems: a blue-yellow mechanism and a red-green mechanism. Color-Opponent Ganglion Cells: These cells are excited by one color and inhibited by its opponent color, forming the basis of this theory. Red-Green and Blue-Yellow Oppositions: These cells respond to specific color pairs, with one cell being excited by red and inhibited by green, and another being excited by blue and inhibited by yellow. By comparing the activity of these cells, the brain can determine which colors are present in the visual scene. A cell might be excited by red light but inhibited by green light, or vice versa.

Answer 71

achromatic channel: L+ M red-green channel: L vs M blue-yellow channel: (M+L) vs S

Answer 72

Function: Respond only to color contrast (not intensity) and are thought to play a role in phenomena like simultaneous color contrast. A specific type of color-opponent cell found in the retina, with center and surround regions having opposite color responses, useful for detecting color edges. - thought to be in V1 - their exisitence is contraversial simultaneous colour contrast: = perceptio of a colour is altered by it's surroundings -Grey square in centre of red looks reddish, one in middle of green looks greenish -By stimulating the surrounding we can induce colour

Answer 73

LGN (Lateral Geniculate Nucleus): Neurons respond to differences in cone activation, which is the first stage of color processing. V1 (Primary Visual Cortex): More complex color processing occurs here, where cone outputs are combined to perceive distinct colors. Colour Representation: Different regions of V1 (specific blobs and layers) process specific color information, contributing to the perception of hues. * From LGN to V1 we have the transformation of cones to colour

Answer 74

- is a combination of illumination and reflectance of object together Determined by spectral distribution of reflected light * Spectral power distribution of illuminant * Spectral reflectance function of object * But we don’t want objects to look different when the illumination changes (this would be confusing)

Answer 75

Definition: The perception that colors remain constant under varying illumination. - colours do not appear to change at different times of day or from artificial to daylight Mechanisms: 1. Chromatic Adaptation: The visual system adapts to the color of surrounding light, making objects appear the same color despite changes in lighting. 2. Context Effects: The surrounding colors can influence the perceived color. 3. Memory Effects: Expectations based on prior knowledge (e.g., yellow for a banana) influence perception. -Doesn't always work if we have narrow spectral distribution

Answer 76

Definition: The ability to perceive the true reflectance of objects despite changes in lighting. Example: White chalk appears white, and black charcoal appears black, regardless of light conditions. Factors: Use of lightest/darkest reference: The brain uses the extremes of lightness in the environment to judge other colors (e.g., shadows vs. material changes).

Answer 77

Extra-striate Areas: Multiple brain areas, such as V4 and IT (Inferotemporal Cortex), are involved in higher-order color processing and object categorization. Task-Dependent Processing: The extent of color processing can vary depending on task engagement, attention and type of response.

Answer 78

It’s the idea that we assume the colour we see belongs to the object itself—as if it’s part of the material of the object—not something caused by the lighting or environment. The color we see is a mix of: The light source (like daylight or a lamp) The object’s surface (what wavelengths it reflects) But our brain filters that out, and decides: “This must be the object’s true color.” -Boundary between two objects -> colour change and lightness change -Changing shadows and shading -> just lightness

Answer 79

Proprioception: Sense of limb position. Kinesthesis: Sense of muscle movement. Tactile Perception (Somesthesis): Sense of objects touching the skin.

Answer 80

Components: Receptors (in the skin) Spinal pathways Brain regions (e.g., S1, S2)

Answer 81

1. Merkel receptors (SA1) - respond to continuous pressure( sustained response) - involved in sensing fine details (texture, shape, edges) 2. Meissner corpuscles (RA1/FA1) -respond to application and removal of stimulus (Transient Response) - Involved in handgrip control - high frequency vibrations 3. pacinian corpuscles (PC/FA2) - respond to stimulus onset and offset - detect high frequency vibration and fine textures by moving fingers 4. Ruffini endings (SA2) - respond to continuous pressure (sustained response) - detect skin stretching - deeper in skin (contravertial) -

Answer 82

SA = Slowly Adapting → Continuous pressure. RA/FA = Rapidly/Fast Adapting → Vibration or change. Sustained Response (Slowly Adapting) What it means: The receptor continues to fire as long as the stimulus is present. Purpose: Detects constant, ongoing pressure or stretch. Example receptors: Merkel (SA1) → texture, shape. Ruffini (SA2) → skin stretch. 🧠 Think: “I’m still holding this object.” Transient Response (Rapidly/Fast Adapting) What it means: The receptor fires only when the stimulus starts and stops, not during. Purpose: Detects changes, like touch onset, release, or vibration. Example receptors: Meissner (RA1 / FA1) → touch changes, grip control, flutter Pacinian (FA2 / PC) → vibration, fine texture. 🧠 Think: “Something just touched me” or “It’s moving!”

Answer 83

merkel -> SA1 fibre -> pressure stimulus -> pressure perception meissner -> RA1 fiber -> light tapping stimulus -> flutter perception ruffini -> SAII fiber -> stretching of skin stimulus -> stretch perception pacinian -> PC -> rapid vibration stimulus -> vibration perception

Answer 84

Free nerve endings on hairy skin, slow conducting(non-myelinated), respond to gentle touch, linked to pleasant touch (→ Insular Cortex).

Answer 85

= specific areas of skin where a particular mechanoreceptor (a sensory receptor for touch) is responsive, and each mechanoreceptor responds to a touch stimulus in a specific area of the skin. Larger fields = less sensitivity. Two-point discrimination test: Tells if you can distinguish between two stimuli. example: Using a vey sharp pencil, attaching them together and poke at different parts of skin, can you tell if there is one or two pencils? - If pencils fall within the same receptor fields cannot discriminate the difference - If they fall within two different receptor fields will be able to tell the difference

Answer 86

Sensory Homunculus: Body parts with more tactile sensitivity take up more cortical space. Plasticity: Cortical maps can change (e.g., string players have more stimulation for cortex for left hand- more touch going here).

Answer 87

the two spinal pathways: 1. Medial Lemniscal Pathway: Fine touch, vibration, proprioception. 2. Spinothalamic Pathway: Pain, temperature, crude touch. Pathway: Receptors → Spinal Cord → S1- Primary (somatosensory receiving area) → S2- Secondary ( secondary somatosensory cortex)→ Higher cortical areas (e.g., premotor cortex).

Answer 88

Study of active exploration via touch. - how we use our somatosensory system to evaluate the world around us -Active touch is more sensitive than passive Touch for object identification.

Answer 89

* When we actively use our hands to explore objects in the world we are more efficient at gaining information than when the object is moved passively across our hand * The way we explore objects with our hands is tailored to the amount of information that we hope to gain Lateral motion → Texture Pressure → Hardness Enclosure → Volume Contour following → Shape Functionally tailored to the type of information needed.

Answer 90

= are specialised receptors that are sensitive to stimuli which are potentially damaging to the skin types: Thermal (Hot/Cold) Mechanical (Cut, pressure) Chemical (e.g., capsaicin) Silent (Inflammation) - pain can not be explained by the simple activation of these receptors

Answer 91

1. A-delta fibre axons - myelinated and faat conducting - initial, sharp pain 2. C-fibre axons - unmyelinated and slow conducting - dull, throbbing longer lasting pain, less intense think stubbed toe vs touching hot plate

Answer 92

Discriminative: Locate and classify pain (where/what type). Affective: Emotional response (how it feels).

Answer 93

Spinal cord ‘gate’ controls signal flow to the brain. S (small) fibres = Excitatory (nociceptors) → Pain ↑ L (large) fibres = Inhibitory (non-pain touch) → Pain ↓ -Activity in S fibres increases when nociceptors stimulated. Activate T (Transmission) also known as P (Projection) cells. More activity here = more pain. All excitatory. -Activity in L fibres increases to normal (nonpainful) tactile stimulation (e.g. rubbing the skin). Activates inhibirory neurons which decreases pain. Closes the gate. Central Control: Brain (e.g., attention, distraction, expectation) can close the gate.

Answer 94

Phantom limb pain: Perception in amputated limbs. - Brain activity resembles real pain. Endorphins: Natural brain chemicals reduce pain perception.

Answer 95

is the sensory process by which organisms detect and perceive temperature changes, mediated by specialized receptors called thermoreceptors, which convert thermal energy into electrical signals.

Answer 96

are key somatosensory relay nuclei in the thalamus, receiving sensory information from the body and face, respectively, and relaying it to the primary somatosensory cortex

Answer 97

is the minimal distance between two points of stimulation on the skin that an individual can perceive as two distinct points rather than one - more sensitive when the threshold is lower

Answer 98

A pressure wave created by vibrations in a medium (usually air). Key Point: No sound in a vacuum because there are no molecules to vibrate. -When an object vibrates, it causes movement in surrounding air molecules. These molecules bump into the molecules close to them, causing them to vibrate as well.

Answer 99

1. Loudness: derived from sound wave pressure level 2. Pitch: derived from sound wave frequency changes 3. Timbre: derived from sound wave shape (quality of sound)

Answer 100

Physical Measure: Sound Pressure Level (SPL) in decibels (dB). - physical measure of sound amplitude Perceptual Measure: How loud a sound is perceived. Key Points: 10 dB SPL increase → Approx. doubling perceived loudness. Loudness varies with sound frequency. Phons: A unit used to measure perceived loudness.

Answer 101

Physical Measure: Sound frequency in Hertz (Hz). - measure of sound oscillation rate - 1 Hz = 1 oscillation per second Perceptual Measure: The "highness" or "lowness" of a sound. Key Points: Pitch perception is a ‘metameric’ percept (same pitch can sound different on different instruments). Sounds separated by an octave (e.g., 500 Hz to 1000 Hz) are perceived similarly.(chroma)

Answer 102

Definition: The quality of a sound, allowing differentiation of sounds with the same pitch and loudness (e.g., different instruments). - everything that is not loudness, pitch, or spatial perception in a sound (multidimentional) - it is what makes a musical note sound different from another one. Key Points: Related to harmonic structure and the relative amplitude of harmonics. Harmonics: Integer multiples of the fundamental frequency.

Answer 103

Components: Pinna, Concha. Function: Gathers and funnels sound energy via the auditory meatus to the eardrum (tympanic membrane) and selectively filters sound frequencies for source elevation cues.

Answer 104

Components: 3 Ossicles (Malleus, Incus, Stapes). - bones Function: Impedance matching (boosts pressure up to 200x) to transfer sound from air (low-impedance airborne sounds) to fluid (high-impedance) in the inner ear. for understanding: impedance matching refers to the middle ear's ability to efficiently transfer sound energy from the air (low impedance) to the fluid-filled inner ear (high impedance) by using the ossicles and eardrum as a "transformer". - "impedance" describes a medium's resistance to movement, like how easily sound vibrations can pass through it. Air has a low impedance, while the fluid in the inner ear has a much higher impedance. This system allows the ear to efficiently transmit sound energy from the air to the inner ear, enabling us to hear.

Answer 105

contains the cochlea: A snail-shaped structure where pressure waves are transformed into neural signals - contains the organ of Corti, which is crucial for hearing. - is a coiled structure with fluid filled chambers on each side Vestibular System attatched: Responsible for balance.

Answer 106

- the sensory organ (equivalent of retina in vision) - runs along the whole basilar membrane - contains hair cells with stereocillia: transducers that convert motion into neuronal signald - start of the auditory nerve

Answer 107

inner hair cells: the sensory receptors that send information to higher cerebral levels - 95% of auditory nerve fibers connect to IHC. - humans have around 3500 outer hair cells: - receieve projections from upper cerebral levels in the brain - role in active filtering Mechano-electrical Transduction: Mechanical tension on hair cells opens potassium (K+) channels, leading to action potentials in the auditory nerve fibers.

Answer 108

Phase Locking: Auditory nerve fibers fire at specific positions in the sound wave. - one cue to sound frequency - each nerve fiber tuned to a best frequency

Answer 109

mechanical properties of the basilar membrane: - narrow and stiff at the base - wide and flexible at the apex - different parts tuned to different frequencies frequency decomposition: - high frequencies at the base - low frequencies at the apex Tonotopic Organization: Different frequencies are processed at different places along the basilar membrane of the cochlea. Key Point: Tonotopy = A frequency map, like the retina for vision.

Answer 110

1. Place Model: Pitch is determined by the location of stimulation on the basilar membrane. (zone of maximum excitation) 2. Rate Model: Pitch is determined by the frequency of nerve firing. (precise timings of individual spikes- micro-seconds) - perceptual system uses a combination of the two systems Basilar Membrane: Acts as the auditory equivalent of the retina in vision

Answer 111

Auditory signals travel through the auditory nerve, the cochlear nucleus in the brainstem, cross over to the opposite side, and then pass through the inferior colliculus → thalamus (medial geniculate body) → auditory cortex in the temporal lobe.

Answer 112

Auditory Cortex: Located in the temporal lobe, responsible for processing sound information. characteristic frequency: Narrowly Tuned Neurons: Respond to a narrow frequency range. Broadly Tuned Neurons: Respond to a broad frequency range. What vs. Where Pathways: 1. What Pathway: Processes "what" the sound is (identity), going from the temporal lobe to the frontal lobe for decision-making. 2. Where Pathway: Determines "where" the sound is coming from, linking with the visual system for spatial awareness.

Answer 113

cochlea -> auditory nerve -> cochlear nucleus -> superior olivary complex(brainstem) -> inferior colliculus(midbrain) -> medial geniculate body(thymus) -> auditory cortex (cortex) - can have slight deviations in pathways (secondary) involving the trapezoid body

Answer 114

1. Sweet: Indicates high calorific value (energy-rich foods). 2. Bitter: Often a warning for toxic substances (poisonous). 3. Salty: Important for regulating hydration and electrolytes (controversial to some researchers). 4. Sour: Often associated with acidic or spoiled food. 5. Umami: Savory or meaty taste, often related to proteins.

Answer 115

Tongue: Main organ for taste. Taste Receptor Cells: Located in taste buds on the tongue. Different Areas: No specific taste zones on the tongue (debunking the "taste map"). Sensitivity varies. (sensitive and insensitive areas for basic tastes)

Answer 116

Different taste receptors are activated by specific tastants (sweet, sour, etc.), each signaling through distinct neural pathways. Each taste receptor type sends signals along its own specific neural pathway

Answer 117

- as soon as an appropriate tastant molecule attaches to the receptor the cell depolarises and sends a signal down one of the gustatory nerves. Salty/Sour: Through ion channels (direct interaction with ions). Sweet/Bitter/Umami: Involve G-protein-coupled receptors (GPCRs).

Answer 118

sweet: sugars; glucose, sucrose, fructose sour; acids; citric, acetic salt; sodium chloride bitter; quinine, caffiene umami; monosodium glutamate- soy sauce

Answer 119

Taste signals are sent to the brainstem, then to the orbitofrontal cortex (OFC), which processes taste-related information. signals from the taste cells travel along: - the chorda tympani nerve (from front and sides of tongue) - the glossopharyngeal nerve ( from back of tongue) - the vagus nerve (from the mouth and throat) - the superficial petronasal nerve (from the soft palate) - these make connections to the brain stem in the nucleus of the solitary tract (NST) - from the NST to the thalamus and then into the insula and the frontal operculum cortex in the frontal lobe - fibres from the taste system also reach thr OFC in the frontal lobe which also recieves olfactory signals.

Answer 120

Pheromone Detection: Used for communication in some species. Food Appreciation: Smell enhances the perception of food flavor. Danger Detection: Can detect harmful substances (e.g., gas, smoke). Anosmia: Loss of smell significantly affects quality of life.

Answer 121

- can measure detection thresholds for different odorant concentrations - recognition threshold - normally requires 3x the concentration compared to simple detection (not just that there is a smell but what it actually is) - often easier to detect presence of a smell when you can give a name to it Methods of Measuring Smell: 1. olfacometer = A device used to control the flow, concentration, and humidity of odorant-laden air. -Allows for precise delivery of smells in lab settings. 2. sniffin-sticks = Pen-like tools infused with specific odorants. Each stick releases a consistent odor and can be used for standardized testing. problems: - Hard to control exact concentrations of odorants, especially in natural environments. -Smells are volatile, so they dissipate quickly and inconsistently. -Humidity and airflow can affect odor perception.

Answer 122

Olfactory Mucosa: Located in the upper nasal cavity, where odorants are detected. Olfactory Receptor Neurons (ORNs): Located in the olfactory mucosa; they are responsible for detecting odor molecules and producing a neural signal. Olfactory Bulb: Receives and processes signals from ORNs; involved in initial odor encoding.

Answer 123

- there are ~350 different classes of ORN in the human - there are ~1000 of each class making ~4million ORNs in total - all ORNs of one type send their output signals to just one or two glomeruli in the olfactory bulb

Answer 124

1. Olfactory Receptor Neurons (ORNs) detect odorants. 2. Signals pass through the olfactory bulb to the piriform cortex (primary olfactory cortex) and amygdala (emotion processing). -Then, information is sent to the orbitofrontal cortex (OFC) for higher-order processing.

Answer 125

Pattern Encoding: Olfactory signals are encoded as patterns of activity across different classes of ORNs. - different molecules e.g hexanol stimulates a different number of receptors in the olfactory receptor neurons (ORNs) Each odorant activates a specific pattern of ORN responses (similar to color perception in vision) but there are 350 types of ORNs. Olfactory Bulb: Responsible for processing signals from ORNs and sending them to higher brain centers.

Answer 126

Flavor is a combination of taste and smell. Taste: Sensory information from the tongue (sweet, salty, etc.). Smell: Olfactory input that contributes significantly to flavor perception. - flavour perception deteriotes when nose is blocled, eating chillis etc

Answer 127

The orbitofrontal cortex (OFC) integrates both taste and smell information, creating the full perception of flavor. Bimodal Neurons: Respond to both taste and smell or taste and vision playing a role in the pleasantness of flavors (reward-related processing).

Answer 128

Synaesthesia: Some people experience synaesthesia, where they may "taste" words or associate specific tastes with people or concepts. Olfactory Memory & Emotion: Smell is closely linked to memory and emotional responses due to its connections to the hippocampus and amygdala.

Answer 129

Dogs: Have far superior olfactory sensitivity compared to humans. Humans: Use olfactory signals for both recognition and emotional responses (e.g., pleasantness or aversion). - tasters non-tasters and supertasters (think bitter TASR38 gene)

Answer 130

including factors such as: - texture of food - temperature - spiciness - coolness (mint) - dryness - hynger/thirst, vision and audition contributing to flavour

Answer 131

a water-soluble chemical that produces a taste sensation by activating taste receptor cells, leading to activity in taste-related pathways in the nervous system

Answer 132

* Odorants are inhaled and flow over the olfactory mucosa * Odorant molecules stimulate the Olfactory Receptor Neurons (ORNs) embedded in the mucosa which produce a neural signal * This signal is passed to the glomeruli (neurons) in the olfactory bulb

Answer 133

- odorant molecules released by food travel to the nasal cavity via the retronasal route