introduction to sensation and perception Flashcards
Lecture 2/22
define sensation
registering stimulation of the senses
define perception
processing and interpreting sensory information
define cognition
using perceived information to learn, classify and comprehend
fundamental concepts - electromagnetic energy
links to eyes
photoreceptors
primary visual cortex
fundamental concepts - chemical composition
links to tongue and nose
chemoreceptors
gustatory cortex and olfactory cortex
fundamental concepts - air pressure waves
links to ears
mechanoreceptors
auditory cortex
fundamental concepts - tissue distortion
links to touch/ nerves
mechanoreceptors and thermoreceptors
somatosensory cortex
fundamental concepts - gravity and acceleration
links to body/ movement
e.g. handstand
mechanoreceptors
temporal cortex
define transduction
conversion of environmental energy to nerve signals
feedback reception
a top down process - going backwards through the sections below. (not via thalamus for smell)
environmental stimulus, receptors, intermediate neurons, thalamus neuron,
primary visual cortex, secondary associative cortex, higher cortex
bottom up processing
perception starts with the physical characteristics of stimuli and basic sensory processes
e.g. feature detectors
gibson - direct perception 1950
links to bottom up processing
the information coming from sensory receptors is enough for perception to be rich and detained - complex mechanisms are not necessary
the environment contains sufficient cues to provide context to aid perception
e.g. texture can indicate depth
direct perception
gibson 1950s
gibson 1950
direct perception
top down processing
the perceiver constructs their understanding of external stimuli based on their past experience and knowledge
gregory 1966
links to top down processing
“perception is not determined simply by stimulus patterns; rather it is a dynamic searching for the best interpretation of the available data”
how do we investigate sensation and perception
- straining
- single cell recordings = electrophysiology
- functional magnetic resonance imaging = FMRI
- Lesion studies e.g. phineas cage
- event-related potential (ERP) from electroencephalogram (EEG)
- Optical imaging / near infa-red spectroscopy (NIRS)
- psychophysics
- illusions and introsception
- computational modelling
what is single cell recording
action potentials of neurons recorded with mircoelectrode inserted close to cell.
single neurons can be selective for a stimulus as specific as one particular person
how is a single cell recording completed
cortical recording requires section of skull to be removed
microelectrodes inserted close to a cell to see its action potential
why is single cell recordings helpful
useful for identifying cells which are selective for certain features e.g. orientations, direction of motion and faces
Quiroga et al (2009) Quiroga et al (2005)
- epilepsy patients implated with depth electrodes, recording from single cell
-presented with photos, text name and spoken name of multiple people
- selective neurons in medial temporal lobe represent individuals in multiple sensory modalities
who research epilepsy with single cell recordings
Quiroga et al (2009) Quiroga et al (2005)
lesion studies
can be done by
knife or neurotoxins
a knife will cut axons but a neurotoxin can only destroy nerve cells
disadvantages of lesion studies
- ethical issues
- studying a faulty system - wont tell you about a healthy system
- brain changes in response to damage
neuro-psychology
damage to brain due to stroke, trauma, road accidents, boxing etc.
disadvantages of neuro-psychology
damage can be diffuse
individual variation in damage
virtual lesions - TMS
Transcranial Magnetic Stimulation = TMS
- pulses of magnetic energy disrupt activity in a small part of the brain for a short period
- can be used to investigate sensation and perception
e.g. biological motion
what is biological motion
is the use of dots in a formation that courses the brain to see a human figure
changing the sped and location of the dots can course the brain to see different genders, weights, happiness or nervousness
what does TMS stand for
transcranial Magnetic stimulation
Grossman et al (2005) - TMS
TMS over posterior superior temporal sulcus disrupts biological motion
disruption of upright biological motion over PPosterior STS (right T6) but not over motion area of visual cortex (V5/MT)
what is psycho-physics
quantifying relationship between physical stimuli and the psychological response
links to absolute/detection threshold and difference threshold
what is an detection threshold
links to psycho-physics
smallest stimulus intensity needed for detection
e.g minimum concentration of a flavor you can taste
what is a difference threshold
links to psycho-physics
smallest difference between two stimuli that can be detected - just noticeable difference -JND
e.g the minimum difference between two colours that you can see
psycho-physics measuring thresholds
two alternative forced choice (2AFC)
psychometric function
what is psychometric function
what is the physical response to the manipulation
what real life issue can psycho-physics be used to study
can be used to find disrupted biological motion in children with autism - blake et al (2003)
blake et al 2003 methods - psycho-physic
used biological motion task video - dots showing human figure
two conditions - one normal second scrambled dots
second task was global form task - had to work out with quadrant has the shape in
blake et al 2003 - findings
(psycho-physics)
Autistic children show poorer performance than typically developing children for biological motion but not for form task
example of research for psycho-physic
blake et al 2003
example of visual illusions researcher
suchow and alvarez 2011
the spinning dancer
visual illusion by Kayahara (2003)
bi-stable perception - no depth cues leads to visual ambiguity
striking individual differences in perception - is it left or right leg being stood on
individuals can learn to switch between both options
ways that illusions can be questioned
introspection and systematically
SAQ - fill in the blanks - Quiroga et al 2005 study used (i) method, investigating the (ii) brain area and showed that neurons can be selective to (iii) type of stimulus.
i = single cell recordings
ii = medial temporal lobe
iii= certain features e.g. orientation, direction of motion and faces
