HNS56 A Virtual Reality? Human Perceptual Function Flashcards
Perception
Basis of awareness
- enable internal representations of everything
- determines personal behaviour
- determines illness, consultation, adherence behaviour
Disturbance (pathology and trauma)
—> impairs normal subjective function in specific ways
—> both symptomatic and diagnostic
NOT the same as seeing/hearing/feeling
Clinical relevance:
- Illness perception
- pain
- diagnostics (pattern detection, blindness)
- risk, threat, unhealthy behaviour
- Axis I psychiatric disorders (panic disorder, PTSD)
- Neurological symptoms
Personal relevance:
- conscious experience underpins all of you
- dreams, waking, spiritual experience
3 functional units of Brain by AR Luria
- Regulating cortical tone and consciousness
- Brainstem: ascending reticular activating system
—> project to different parts of cortex
—> ensure modulation of cortical tone (arousal) is consistent with organism’s requirement
- ensure cortex is optimally aroused / suppressed (e.g. during sleep) - Registering + Processing + Storing information
- intimately involved with process of perception and memory
- contain Reception, Interpretation, Synthesising areas involved in perception
- receives all sensory input —> integrated into other functions
- regulated by other 2 units - Planning + Regulation + Execution + Evaluation
- Anterior cortex + PFC
- plan + initiate action —> by directing motor centres
- regulate behaviour by monitoring performance
Hierarchical organisation of each functional unit
- Primary Projection Zone (PPZ)
- 2nd functional unit
- respond to physical characteristics of sensory activity
- e.g. superior temporal region: cell topographically matched to distribution of hair cells in Organ of corti in Cochlea —> respond to discrete pitches - Secondary Projection Zone (SPZ)
- 2nd functional unit
Example:
- respond to clusters / types of sounds
- stimulation of cells in this area —> experience of discrete sounds e.g. cars, voices
- Proximal to PPZ —> deal with “simple compound” tone
- Distal to PPZ —> complex tone e.g. music - Tertiary Projection Zone (TPZ)
- 2nd functional unit
- complex, integrated experience (e.g. memories of acts / events)
- integrate features from secondary projection zones
- e.g. tertiary zone between auditory and visual projection zones —> sound-image combinations (visualisation of cat and its cry)
- where most complex integration of perception takes place
Neuronal activity: Sensory organ —> PPZ —> SPZ —> TPZ
Brodmann’s area
Functional performance of cortex
3 laws about neurological function
- Stronger the stimulus —> stronger response
- “Higher” brain functions —> less localised than more specific brain functions
- “Higher” brain functions —> more likely to be lateralised into one hemisphere (e.g. language on the left)
Senses
Arises from activation of peripheral energy detectors
—> afferent impulse to CNS
—> PPZ (occipital for vision etc.)
—> Secondary / Tertiary activity occurs in cortex surrounding PPZ
—> more complex, synthetic perception activity
How an organism obtains information for perception:
- Sensation: a result of somatic division of PNS
- Perception and Integration: requires CNS —> **synthesise “experience” by **giving meaning to patterns of activity (NOT all afferent activity gets processed)
5 major senses:
- Sight, Hearing, Taste, Smell, Touch
Percentage of neurons in brain devoted to each sense:
- Sight: 30%
- Touch: 8%
- Hearing: 2%
- Smell: <1%
—> Over 60% of brain involved with vision in some way
Sensation vs Perception
Sensation:
- sense organs
—> energy detectors and signaling devices
—> Afferent neural activity
—> Afferent activity presents centrally primarily as sensation
Perception:
- synthetic central processes
—> involve attribution of meaning to extrinsic and intrinsic activity
—> work on basis of ***rule-application
—> presence of “hypothesis-testing” process to try to find a “best-fit” interpretation for a particular pattern of cortical activity, irrespective of origin e.g. language processing
Constructive perception
- Direct by-product of sensations about the world and how it works
- NOT objective
- may reflect personality and interpretation
Attentional processes and Capacity channels
- Crucial element of recognition
- severely disrupted by damage to ***Inferior frontal cortex —> paralyse person’s capacity to respond to everything
- enables selection of input for further processing (∵ for any modal input: Limited capacity channel —> only limited access to different information streams —> restrict extent and speed that information can be acquired)
- most memory problems are attention problems —> information never got into brain in the first place
Bottom-up vs Top-down processing
Preliminary processing:
- Bottom-up: specific elements of stimulus identified and assembled into more complex forms such as geons
- ***Stimulus information
Top-down processing:
- driven by knowledge-based processes e.g. expectations and context —> provide collateral information about likely nature of input
- past experience, may help reduce uncertainty and set salience (salience also influenced by current physiological status)
- ***Contextual information
Constancies
Characteristic of perception
- Rule-driven process
- e.g. colour, shape, size, brightness, location
- e.g. shape constancy —> cube shape remains the same despite viewing from different angles - Sensory features of objects consistently seen as object characteristics (not simply as sensory features)
—> ***Objectification of sensory characteristics —> allow ability to construct virtual reality
Memory concepts
3 stages of memory:
- Encoding
- Storage
- Retrieval / Rehearsal
Sensory register
—(Limited capacity channel)—> Short-term memory
—(Encoding, Storage, Retrieval, Rehearsal)—> Long-term memory
- “Early” vs “Late” selection of input
- Available attentional capacity: determining criteria for input selection stage
Levels of processing
Sensory, Shallow, Intermediate, Deep
Sensory encoding:
- most superficial
- sensory stores “buffer” registers
- 200ms
- Eidetic, Echoic registers
Attentional theory of remembering:
- Structural encoding: most Superficial
- Phonemic encoding: Intermediate
- Semantic encoding: Deepest
Summary of features of Perception
- Recognition through activation
- Attentional process
- Limited capacity channels
- Short-term / Long-term memory activation
- Bottom-up processing
- Top-down processing
- Constancies - Synthesis
- Top-down processing
- Hypothesis-testing - Pattern detection
- give meaning to stimuli —> model and predict outcome
Stimulus characteristics
- Size, shape, colour, location, pitch, timbre
- Intensity (brightness, volume)
- Magnitude (size)
- Contrast
- Novelty
- Salience (relevance - determined by top-down influence)
Before attention, stimuli are organised according to bottom-up steps:
- Feature analysis
- Proximity
- Organisation
- Similarity
- Simplicity (complex pattern reduced to basic pattern)
- Continuity
Top-down influence
1. Past experience —> expectation generated —> set up priming to detect certain likely stimuli associated with the context —> reduce uncertainty —> make it less of random detection process —> increase speed of recognition
