Mechanisms of Perception, Conscious Awareness and Attention
- Created by: meg_lou
- Created on: 10-05-17 10:34
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- Mechanisms of perception, conscious awareness and attention
- Visual cortex
- Where
- Back of brain in occipital love
- Its main input from the lateral geniculate nucleus
- Visual receptive field
- Receptive fields respond to different things
- Neurons are sensitive to different parts of a scene
- 3 types of neutrons distinguished: simple, complex and hypercomplex cells
- Function
- V1 transforms information about the whole image from the LGN into separate parts of a scene
- E.g. different neurons would encode different sets of lines
- Visual cortex has an organisation that forms a map of a scene that was being looked at in different areas
- V1 is first level where visual information is separated into dorsal and ventral stream
- V1 transforms information about the whole image from the LGN into separate parts of a scene
- Where
- Organisationalprinciples
- Hierarchal
- Specificity and complexity increases with each level
- V1 processes edges and lines
- V2 processes shapes
- V4 processes objects
- Inferotemporal cortex (IT) processes faces
- V4 processes objects
- V2 processes shapes
- Secondary areas - input mainly from primary (e.g. visual)
- Association areas- input from more than one sensory system (higher in hierarchy)
- Evidence - to treat a scotoma, perceptual filling in is done from scene interpretations higher up
- Functional segregation
- Each level of the cortex contains functionally distinct areas that respond to different aspects of stimuli
- Physical separation according to function e.g. orientation sensitivity in V1
- Parallel processing
- Analysis of a signal in different ways by the multiple parallel pathways
- Two different parallel streams of analysis in our sensory systems
- One that influences behaviour without our conscious awareness and one that engages it
- Supports control of behaviour vs conscious awareness theory
- One that influences behaviour without our conscious awareness and one that engages it
- Hierarchal
- Mechanisms
- Evidence for separation
- Object discrimination task
- Primate has bilateral to temporal lobe
- Cannot discriminate between objects
- Two results together form a double dissociation
- Ventral necessary for recognition and dorsal necessary for location
- Two results together form a double dissociation
- Cannot discriminate between objects
- Primate has bilateral to temporal lobe
- Landmark discrimination task
- Primate has bilateral lesion to parietal lobe
- Unable to discriminate a location
- Two results together form a double dissociation
- Ventral necessary for recognition and dorsal necessary for location
- Two results together form a double dissociation
- Unable to discriminate a location
- Primate has bilateral lesion to parietal lobe
- Object discrimination task
- Disorders of visual perception
- Prosopagnosia - unable to recognise faces but other recognition is unaffected
- Evidence for functional segregation - shapes not processed in same place as faces
- Capgras delusion - familiar person is an impostor
- Facial recognition intact but damage to parallel unconscious system for emotional recognition of faces
- Prosopagnosia - unable to recognise faces but other recognition is unaffected
- Other cases
- Oliver Sacks
- Man could only see one object at a time (Simultanagnosia)
- Dr P could not recognise a glove and mistook his wife's head for a hat
- Man could only see one object at a time (Simultanagnosia)
- Oliver Sacks
- Evidence for separation
- Visual cortex
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