Lecture 2.2 - Sensory Information II Flashcards
T or F: Perception involves associating meaning to a stimulus
True
Differentiate between sensation and perception.
Sensation: the neural activity triggered by a stimulus activating a sensory receptor i.e. touch
Perception: Associated meaning to that particular sensation picked up by the sensory receptor
Involves integration, selection, organization, and interpretation of information that comes from that sensation
Can the same sensory stimulus be perceived differently?
Yes
What are the 4 main functions/purposes of sensation?
- Perception - associated meaning to these sensations you experience daily
- Control of movement - “don’t continue touching that because it doesn’t feel right/there is pain when I touch it”
- Regulation of body function
- Maintenance of arousal
What are sensory receptors?
Sensory receptors occur in specialized organs such as the eyes, ears, nose, and mouth, as well as internal organs, and skin. Each receptor type conveys a distinct sensory modality to integrate into a single perceptual frame eventually.
What are the 4 sources of sensory information?
- Afferent sources - i.e. sensory neurons like touch receptors
- Exteroception - i.e. auditory, visual, olfaction
- Feedback - information produced from various sensory sources as a consequence of movement
* Info about movement itself, typically during or after the movement - Feedforward - information about the intended actione
* Expectation about the movement consequences before any action begins
* A reference point to what the system should feel like
Describe the pathway of optical array –> optical flow (light) entering the eye
- Light enters through the cornea.
- Light passes through the iris & pupil.
- Light hits lens once it passes through iris.
- Light hits retina at the back of the eye.
- Light impulses travel from retina to the optic nerve (CN II).
- Optic nerve carries impulses to visual cortex.
Describe the structures of the visual system
➔ Cornea → clear outer layer at the front of the eye
➔ Iris → controls the amount of light that enters the eye.
➔ Pupil → opening in the iris, controls intensity of light
permitted to strike the lens.
➔ Lens → controls the focus of light.
➔ Retina → Converts light into neural impulses.
➔ Optic nerve (CN II) → carries neural impulses to the brain.
➔ Visual Cortex → region of the brain that receives,
integrates and processes visual information.
What is the snellen scale?
➔ Measure of static *visual acuity
◆ 20/20 - normal vision measured in feet
◆ 6/6 - normal vision measured in meters
◆ 20/200 - at 20 ft. distance, what a normal eye sees at 20 ft., this individual sees at 200 feet = letters are very small/hard to read = poor vision
*Visual acuity = test distance / letter size
What are the 4 different streams of vision of the vision system?
➔Focal vision is the conscious vision that identifies objects in the center of the visual field
➔Ambient vision is orientating the body to take in the entire visual field – turning body orientation changes the ambient vision
➔Optical flow is the flow of light across the retina – the light that enters the eye
– The visual perception of motion, position, timing or direction
– The perception/interpretation of it
➔Optical array is the reflected light entering the eye
from everything in the environment.
– Not vision but reflected light, however we need this in order for there to be vision,
–> Why we can’t see objects in the dark
After the optic nerve (CNII) carries the impulse to the visual cortex, it differentiates into which 2 pathways? Describe each pathway
- Ventral pathway
- What the object is, object perception
- Happens in the inferotemporal cortex
- Consciously controlled - what we choose to focus on
- Primarily useful in the central visual field / focal vision - Dorsal pathway
- Where the object is and where I am, motor movement perception
- Tells us how to move within the field that we see
- Happens in the posterior parietal cortex
- Non-conscious vision - we would go crazy if we paid attention to everything in our visual field
- Movement information goes straight to the effector since it is non-consciously controlled - doesn’t need to go through a comparator
What is cerebral kinetopsia and what visual pathway does it affect?
Motion blindness
- Patients cannot perceive motion in their visual fields
- Affects the dorsal pathway
- Movement jumps from scene-to-scene, like glitching
With a ball catching task, what happens when you cut down the viewing time / time of perception? What does this show?
Study from Whiting (1970)
Catches will become less consistent, shows visual processing / perception of movement takes time
What is perception-action coupling?
- Requires meaning attached to a sensation, which is then used to produce an action/movement.
- “We must perceive in order to move, but we also must move in order to perceive”
- i.e. lionel messi analogy
- i.e. moving wall experiment - how they perceive this movement of the walls from their visual field affects their balance
- Don’t have good perception of movement = not able to move properly
- i.e. visual cliff paradigm - infants reluctant to crrawl over “cliff” due to perceived depth - adults know their is plexiglass, perceive the exteroceptive input differently, and then their movement programming is different
What is the Tau variable?
Tau (T) an optic (eye) variable that specifies time until perception/recognition/contact
- Involves judging of distance between multiple stimuli
- Involves the dorsal pathway
Retinal image size / image rate of change in size = time remaining until contact
Smaller retinal image size = longer time remaining until contact
- Explains why objects further away are harder to determine their velocity of travel due to smaller retinal image size
- When time intervals between stimuli become inconsistent, the shorter time interval saw the corresponding stimulus as being closer
- Shows how flinching happens
i.e. 3 light experiment, all 3 lights flash at the same time intervals, however, the furthest light is perceived as slower because it was just a little further away
- Stimulus being perceived differently because of the inconsistency in time intervals
