Perception 2 Flashcards
Sensory adaptation
A decrease in sensory receptor sensitivity to a constant stimulus helps us ignore unchanging information.
Sensory systems respond less to repeated stimuli.
The brain interprets the proximal stimulus based on changes, not fixed values.
Context affects perception early in the sensory process.
Visual( Ganglion cells) adaptation
adapt their firing rate to ambient light levels.
In bright light, they need stronger stimuli to respond.
They detect changes in brightness rather than absolute light levels.
Weber’s Law
The just noticeable difference (JND) is the smallest change in a stimulus that can be detected.
JND depends on the stimulus magnitude: ∆I / I = K (Weber’s Law).
K (Weber fraction) varies by sense:
Loudness: ≈ 0.05
Brightness: ≈ 0.08
Heaviness: ≈ 0.02
Auditory adaptation &
Weber’s law
Auditory Adaptation: The ear becomes less sensitive to constant or repeated sounds.
Weber’s Law: A ~5% change in sound intensity is needed to notice a difference.
Examples:
Tuning out background noise (like an air conditioner).
Noticing volume changes more in quiet settings than in noisy ones.
Somatosensory system (weight and Weber’s law
JND in Weight: ~2% of the
object’s weight
I = 𝐾 4/ 200 = 0.02 2%
- Heavier objects require greater
changes to detect differences
Somatosensory
adaptation
- SA = slow adapting
- RA = rapid adapting
A receptive field is the area of a sensory surface that a neuron responds to( Acuity)
Smaller receptive fields → Higher acuity (sharp perception).
Larger receptive fields → Lower acuity but respond to more complex stimuli.
Higher-order neurons process broader and more complex sensory information.
Visual receptive
fields( photoreceptors and Retinal ganglion cells)
Each neuron after photoreceptors processes input from multiple photoreceptors.
Retinal ganglion cells gather signals from bipolar and amacrine cells to detect patterns and contrast.
Visual receptive fields ( Ganglion cells, LGN. V1)
Ganglion cells: Detect contrast with center-surround fields
.
LGN: Keeps center-surround organization
.
V1 neurons: Respond to edges and orientation
Ganglion cell ( Action)
Action potentials of ganglion cell and At rest, ganglion cells is firing at some baseline level
ganglion cell / Light falls outside
There is no change in response when light falls outside the receptive field of a ganglion cell.
Light at center of receptive field.
= increased firing rate.
No Change when Ganglion cells
There is no change in the ganglion cell’s response when light falls outside its receptive field.
Ganglion cells/ falls on the surrounding Light
When light falls on the surrounding area that inhibits the cell, the cell’s response decreases further.
Auditory of a hair cell
Receptive field of a hair cell: frequency of sound.
Somatosensory receptive fields( mechanoreceptor, Suface, Deeper)
The receptive field of a mechanoreceptor is the area on the skin that the receptor responds to:
Surface receptors: Smaller receptive fields.
Deeper receptors: Larger receptive fields.
Somatosensory
receptive fields/ body, Back, Thigh, Foot.
Receptive field size and acuity vary across different body parts:
Back: Larger receptive fields, lower acuity.
Thigh: Moderate receptive field size and acuity.
Foot: Smaller receptive fields, higher acuity.
Somatosensory
Lateral inhibition enhances contrast by
allowing neurons to adjust their signals, making sensory information more distinct.
Topographic maps
show how sensory information is organized in the brain, with nearby sensory areas mapped to nearby brain regions.
Retinotopic map
How is visual information organized in primary visual cortex? Ret, Hierarchically, V1, LGN
Retinotopically: Neighboring areas on the retina map to neighboring areas in V1
Hierarchically: Visual info flows through V2, V3, V4, V5 (MT).
V1: Processes initial visual features.
LGN to V1: LGN sends visual info to V1 for recognition
Retinotopic Map
organizes retinal information in the brain, with Neighboring retina areas mapped to V1 areas.
Tonotopic( Auditory) Maps
A tonotopic map is a fundamental organizing principle in the auditory system. It represents the mapping of different sound frequencies to specific spatial locations.
Somatotopic maps
A somatotopic map links body parts to the somatosensory cortex. Somatotopy is this point-for-point mapping.
Somatosensory homunculus
It is a cortical homunculus, which is a map of the body’s surface on the somatosensory cortex in the brain. The somatosensory cortex is arranged such that a particular location receives information from a particular part of the body.