Sensation and Perception

sensation

early processing of stimuli in environment

perception

formation and experience of the mental representation of those stimuli

what is transduction

translating energy into neural signal by a receptor

what do sensory receptors do?

specific physical properties in our environment

what kind of sensory receptors are there?

light - photoreceptors

pressure - mechanoreceptors

molecules - chemoreceptors

what is a receptive field

space in sensory area that when stimulated, evoke selective response from neurons

types of receptive fields

visual rf - lateral geniculate nucleus (LGN)

somatosensory RF - primary somatosensory cortex

what factors influence receptive fields?

size and desnity of receptive field influence acuity or sensitivty of receptive field

placing a stimulus within a receptive field can either excite or inhibit neural firing

what is adaptation?

"resetting" gain or sensitvity of the system to account for ambient conditions

allows you to habituate to sound, smell, touch

how do we process senses via the sensory pathway?

all start with receptor cells that tranduce environmental stimuus into neural signal -> end in primary sneosry cortices. all pass through brain stem and thalamus on the way (EXCEPT FOR OLFACTORY SYSTEM)

T/F all sensory information goes through futher stages of processing?

yes, sensory information goes through further stages of processing within and between modalities, starting with secondary sensory cortices.

are neurons tuned to certain properties in the environment?

yes, neurons along sensory pathways are tuned to certain stimulus properties (orientation, colour)

T/F different properties of environment is specialized by different pathways

yes.

eg V4: colour, V5/MT: motion

what are topographic maps?

an ordered mapping of the external world to its represetation in the brain

somatotopy: body parts

tonotpy: sound frequency

gustatotpy: taste

what do maps do?

represent locations in visual field and magnify regions of greater important/higher acuity

how does multisensory integration work?

information from multiple senosry modalities converged subcortically. we integrate cooinciding sensory inputs to better interpret the enviornment, weighing each input based on reliability

what are the wonders of object recognition

1. despire having seperate prciessing streans,m we ave a perceptual ecpeirence that unifies these

2. we can identify the same object across variations while also distungushing it from other similar looking objects

3. we can recognise objects, eent thoght they take copeltely different form

why is levelling up so hard?

need to construct 3d representation from 2d retinal projectio

what are the levels of visual processing?

low level procesing - pixels, edges

mid level processing - shape form grouping

high level processing - object recognition

what is dorsal pathway responsible for? what is ventral pathway responsible for?

dorsal: grasping, reaching, space/action related information

ventral: object analysis and identification

what does damage to dorsal pathway do? what is intact and what is impaired?

impairments using visual information to guide actions

What does LOC do?

differentiate between shapes and non shapes, but doesnt distinguish between shape and non shape

what region of the brain is sensitive to whether objects are recognisable or not?

anterior regions of the ventral temporal cortex (VTC)

not only can VTC differentiate between objects, but it can also...

differentiate between different groupings of objects (faces vs scence)

T/F VTC neurons have large receptive fields and their representatoins are robust to chages in view (view invariant)

True

Stages of processing in the ventral pathway

LGN: pixels,

V1: colour, line

LOC: shapes

VTC: complex featues and objects

What is visual agnosia?

caused by damage to the ventral pathway including LOC,

deficit in recognising visually presented objects

what is apperceptive agnosia?

capable of percieing light and dark boundaries

inability to match or copy objects on the basis of form. unable to recognise objects from atypical views

what is associative agnosia?

ability to copy objects, point by point

unable to identify objects by sight, but can with other senses like touch, knows action associated with object

What is propognosia

face specific recognition impairment

what is disassoable dorsal?

being able to make appropriate movements to execute an action but unable to match objects with eachother (acting without perceving)

dorsal: unconcious

ventral: concious

percieved motion activated motor cortex but not visual cortex

True

informatoin encoded in later visual areas..

tend to better rflect what is perceived rather than not only what is sensed.