Cognitin in clinical context Flashcards
cognition
“refers to all processes by which the sensory input is transformed, reduced, elaborated, stored, recovered and used” Neisser 1967
used in everything humans do
information processing metaphor
looking at brain doesnt reveal its functions, needs a metaphor
processes between presentation of stimulus and response
information -> input -> processor -> storage -> processor -> output -> information
whys scientific metaphor needed for cogition
scientific theories aim to be refutable
can’t look inside mind to see cognition
cognitive psychology relies on analogy
models of cognition evaluated against data
methodological approaches
- experimental psychology: healthy humans tested, large sample sizes, small budget
- computational modelling: computer stimulations of cognitive processes, parallel distributed processing
- cognitive neuropsychology: consequences of brian damage, associations and dissociations
- cognitive neuroscience: brain implements cognitive functions using neuroimaging technology
top down processing
processing influenced by individual goals, expectations, desires, plans, intentions rather than stimulus by itself
bottom down processing
processing directly influenced by stimulus, input proceeds through series of processing stages until required output is produced
perception
refers to ability to extract meaning from sensory input
includes audition, taste, touch, olfaction but is dominated by vision
vision alone accounts for over 50% of neurons in cortex
perception is constructive process
visual system
image -> retina -> cognitive system constructs perception
distal stimulus-object “out there” in environment
proximal stimulus-info registered on sensory receptors
misleading impression of simplicity
tootel 1982-support notion that near perfect representation of eternal world is projected onto primary visual cortex
monkeys unconscious, eyes pinned open, stimulus displayed for 25 mins to eyes, eyes in glucose solution, activity of brain detected, image in visual cortex, not what stimulus was
processing streams
ventral-‘what’ pathway, facts/objects you see
dorsal-‘where’ pathway, sensory inputs/location
-ventral stream; visual memory, specialised for object perception and recognition, determines what you’re looking at, V1 to temporal lobe
-dorsal stream; no visual memory, determines where object is using spatial configurations between objects, V1 to posterior regions of parietal lobe
-no colour at peripheral vision, brain assumes it
object recognition; 3 stage model
- image->local features ->shape representation ->object recognition
- image -> edge detection/contrast -> gestalt principles/feature integration -> stored representation/knowledge
- if object recognition goes wrong can tell when
gestalt principles
- whole visual perception more than sum of parts
- perceptual system try impose organisation on inputs
- components of image grouped together on basis of certain visual properties
- laws ‘good continuation’ and ‘closure’ = illusory contours
- see patterns rather than random arrangement
- proximity/similarity/continuation/closure
shape perception
- primarily bottom up processes produce primitive sketch
- sketch contains primitives eg edges/orientations/positions
- top down processes used to group collections of primitives into “lines, curves, blobs, groups and small patches” known as symbolic primitves
object recognition 3 models
- template matching
- feature analysis
- recognition
how do we do facial recognition so well
- challenge of individuating faces made apparent by fact they share basic configuration
- first order relations: two eyes, nose, mouth
- features are ample for rendering percept of face, but inadequate in rendering percept of ‘that’ face
- some instances where features are distinctive and accurate in signalling identity of individual
- second order relational properties
early model of facial recognition-modular model
Bruce and Young 1986
modular model with sub functions whihc are processed independently
distinctive pathways: recognising familiar faces vs recognising expressions
parallel pathways: facial expression, facial speech, visually derived semantic information
familiar face recognition-fru&pins
serial process
- face recognition units-stored descriptions of previously encountered faces, seen it before?
- personal identity nodes-identity specific info, their job, where they are from
- name generation-input from PINs generate name of identified individual
other routes for face recognition
parallel
expression analysis-computing facial emotion as happy, fearful etc
-facial speech analysis-lip reading regardless of hearing loss or not
-directed visual processing-when looking for information from a face
early evidence for bruce and young model-memory loss diary
memory loss diary study
-person not recognised
-feeling familiarity without identity
-person recognised, name not retrieved
-person misidentified
-repetition priming-recognise it quicker next time
familiarity not influence gender decision, expression analysis
humans selectively attend to identity or emotion in sorting tasks
brain support for Bruce and Young model
parallism: double dissociation between processing of facial expression and face recognition, some have deficits in identity but not expression and vice versa
double dissociation: two related processes function independently
different cortical sites active in processing of identity vs emotion, lateral fusiform gyri and inferior occipital
challenge of semantic priming
semantic-meaning/content/facts
face responded to faster if follows a closer related face than unrelated face
response to target is faster when proceeded by semantically related prime
interactive activation and competition (IAC model)
-built in as basic models/processes
-semantic information/knowledge is ‘pooled’
relationships between different bits of knowledge are represented in connections between the pools
-connections wihtin pools are mutually inhibitory
-connections between pools are mutually facilitatory
-if info from a pool is recollected, it inhibits any other info from pool being remembered but info from other pools that is linked is remembered
face selective neurons
- signal face familiarity, PINs are modality free gateways to semantic info
- no separate node for names; part of semantic information
- inferior temporal cortex-only neurons in cortex fire when hands or face are seen, but dont fire when fruit or genitalia are seen
- superior temporal sulcus used in social interactions, social perception and speech
logic of gnostic units
cells in inferior temporal cortex are selective to complex stimuli, giving credence to hierarchal theories of object perception
- early visual cortex codes elementary features such as line orientation and colour
- cells at highest level in hierarchy code specifically to shapes such as hands or faces