L1 Introduction to Perception Flashcards
What is perception ?
The psychological processes and underlying physiological mechanisms by which we gain knowledge of the world via sense organs
Perception doesn’t just create a picture in the mind it lets us gain knowledge about the world
How much of the brain is visual brain areas ?
Over half of the cortex is a visual brain area
100000000 photoreceptors in each retina to receive light
100000000000 cells in the cortex
Each nerve cell makes 4000 connections to other cells
What are the motivations to study perception ?
Theoretical - understanding how the brain functions in general
Practical - discoveries in perception have been put to good use
What is the psychophysical approach to studying perception ?
Perception is an interdisciplinary endeavour
The oldest approach
What is detection threshold ?
The weakest stimuli that reliably evokes a sensation
What is discrimination threshold ?
The smallest difference between two stimuli that can be noticeable
How do you measure detection thresholds psychophysically ?
Limits - change stimuli strength until it is detected
Adjustment - same as limits but the subject changes it themself
Constant stimuli - show various strength stimuli at different times and ask if they can detect it or not
Use a forced choice task to remove bias
Must be over 75% correct in the Psychometric function graph
How do you measure discrimination thresholds psychophysically ?
Forced choice task - present two stimuli consecutively and ask which is stronger, then make the difference smaller or bigger
What is signal detection theory ?
Sensory systems are ‘noisy’ as neurons are always firing - sometimes we mistake background hum as a stimulus and sometimes we miss stimuli because of the background noise
What is the neuropsychological approach ?
Recording electrical activity of cells in sensory pathways
Put electrodes in the brain and present stimuli
It enables them to map the receptive field of a cell
What is a peri-stimulus-time-histogram ?
A plot showing how the firing rate of a cell changes during the time a stimulus is presented within its receptive field
How is neurophysiology reductionist ?
Reduces a complex problem
May not gain insight into the entire process of something such as vision
What are the methods used to study brain areas ?
PET and fMRI - active brain areas have more activity
PET - requires radioactive tagging so cannot be used as much
fMRI - activity is not well understood but good spatial accuracy
EEG/MEG - measures electrical activity across the brain
