Week 2 - Perception, Attention & Consciousness Flashcards
Sense organs:
Visual Vestibular Auditory Olfactory Tactile Gustatory
Sense organs:
Visual - seeing -eyes Vestibular - balance - ears Auditory - hearing -ears Olfactory - smell - nose Tactile - touch - skin Gustatory - taste - tongue
3 shared characteristics across senses
Transduction
Adaptation
Sense & perceive
Transduction
Transforming the physical energy caused by a stimulus into electrical signals that are sent to the brain for further information processing
Adaptation
The decreasing response of sense organs cause by exposure to a continuous level of stimulation
Slow & quick adaptation
No adaptation for high intensity stimulation
Sense & perceive
Information that the brain must process following transduction are sensations
Perceptions are the meaningful experiences that result after brain processes the sensations
What Is attention
Narrowing of the senses (Aristotle)
One from many thoughts / objects taking vivid possession of the mind (James)
Filter / bottleneck - owing to limited capacity perceptual system (broadbent)
Providing priority - semantic priming
Response preparation/ selecting a goal for an intended action (promotor theory)
Non-response based - facilitating memory & consciousness
Attentional resource limitation & selection - eliminated by practice
Attention
Selecting ideas in ones mind or aspects of the physical environment for further active processing
Attention: characteristics
Attentional beam/ spotlight/ focus -> fovea / peripheral
Detection of attended than unattended stimuli - faster
Consequences of attention -> priority, not acuity
Spatial and temporal limitations
Paradigms: attentional blink
Evaluates temporal limitations of attention
Attention: characteristics
Feature-based versus spatial attention (goal or no)
Local/ global processing ( big letter made of little letters- faster at recognising if they are the same)
Endogenous / exogenous cueing ( endogenous = you choose / exogenous = e.g. a cup falling - grabs your attention without you choosing)
Overt / covert attention (can look at one thing and be actually attending to another )
Top-down / bottom-up attention (previous knowledge influencing or no)
Top-down/ bottom-up: orienting brain
Dorsal system:
Ventral system:
Dorsal system: Voluntary orienting (covert/overt) Top-down attention
Ventral system:
Involuntary orienting (unexpected)
Bottom up attention
Attention: brain basis
Not single brain region
System of networks
Not the whole brain
Neuroimaging Electrophysiology Neuropsychology Pharmacology Studies on humans (all age groups) and animals Behavioural paradigms (several)
Neural electro physiological markers: MMN
Mismatch negativity (MMN): Perception of unexpected or deviant stimuli
Attention & the posterior parietal cortext
The human posterior parietal cortex is divided by the intraparietal sulcus (IPS) into the superior parietal lobe (SPL) and the inferior parietal lobe (IPL)
The IPL consists of the Angular Gyrus (Ang) and the supramarginal gyrus (Smg)and boarders on the superior temporal gyrus at a region often referred to as the temporoparietal junction (TPJ)
Attention: three brain networks
Select
Also referred to as ‘executive attention’
Involves mechanisms for monitoring & resolving conflict among thoughts, feelings, and responses.
Attention: three brain networks
Orient
Defined as the selection of information from sensory input
Aligning attention (overt or covert) to source of sensory signals
Attention: three brain networks
Alert
Defined as achieving and maintaining a state of high sensitivity to incoming stimuli
Levels of alertness vary with influence of warning signals
Agnosia: disorder of perception
Impairment in higher visual processes necessary for object recognition
Relative preservation of elementary visual functions. Absence of dementia. Preserved general knowledge about objects
Able to recognise objects through other modalities (touch, audition, verbal description)
Integrative agnosia
A form of visual agnosia in which one retains the ability to recognise elements of objects but is unable to integrate these elements together into comprehensible perception.
Optic aphasia
A condition in which a person cannot name a visually presented object, despite being able to indicate the identity of the object through gesture and sort the visual stimuli into categories
Balint’s syndrome
Agnostic syndrome that results from large bilateral parietal lesions and is composed of three deficits: (1) paralysis of eye fixation with inability to look voluntarily into the peripheral visual field, (2) optic ataxia, and (3) disturbance of visual attention such that there is neglect of the peripheral field
Prosopagnosia
Inability to recognise familiar faces despite adequate elementary visual function (visual field, visual acuity, colour)
Faces no more important than objects (face blindness)
Use of secondary information for recognition (voice, hair, smell, clothing)
Apperceptive agnosia
Difficulty forming a complete visual perception
Visual form agnosia: inability in simple shape discrimination. Inability to group local visual elements into contours, surfaces, and objects
Diffuse bilateral damage to the lateral occipital lobes, critical structures involved in visual perception
Preserved visual acuity, visual fields, brightness discrimination, colour vision, and fixated maintenance (elementary visual functions)
Associative Agnosia
Adequately perform figure-copying, but often unable to identify the copied image.
Uses shape cues to try to identify the presented object (as opposed to colour and texture). Often mistakes objects for one that is similar in shape.
Failure of the structured perception to appropriately activate the network of knowledge about the functional, contextual, and categorical properties.
Category-specific visual agnosia (CSVA) usually distinguishes between biological (fruits) and nonbiological objects (tools).
Simultanagnosia
Inability to appreciate the overall meaning of a complex picture or stimulus, with preserved perception of isolated elements or details within the stimulus.
Dorsal stimultagnosia cannot detect more than one object at a time and have difficulty shifting attention from object to object. Impairments result from an inability to disengage attention from a specific object or a region of space.
Ventral stimultagnosia characterised by the reduced ability to recognise multiple visual stimuli rapidly.
Loss of vision
Damage to different parts of the visual pathways from the eye to the visual centres of the brain leads to different patterns of visual field loss
Loss of vision: Hemianopsia
Loss of vision over half of the visual field, typically from damage to the optic radiations that project to V1 or damage to V1 itself.
Loss of vision: cortically blind
Cortically blind - lesions in primary visual cortex
The phenomenon of Blindsight
Some cortically blind patients retain the ability to detect visual information within this blind region.
Forced choice trials (detection of a light flash - occurred on 50% of trials)
Only close to chance when flashed in blind spot (43% - labelled DISC)
Otherwise way above chance detection
Reports not seeing “light” but noticing change.
Neglect: Disorder of attention
Unilateral spatial neglect: failure to respond, orient or report stimuli presented on the opposite side of the brain lesion [high heterogeneity in USN Presentation]
Inability is not attributable to primary sensory or motor deficits
Right hemisphere brain lesions to the lateral posterior parietal lobe
Precise location and size of parietal lobe lesion varies (inferior / superior)
Mechanism: spatial attention theory
Attentional bias- excessive orienting to ipsilesional side of space and away from contralesional side
Mechanism: spatial representation theory
Disrupted conscious representation of left side of space
Neglect: disorder of attention
Egocentric USN
Allocentric USN
Other USNs
Neglect: disorder of attention
Egocentric USN Neglect of the contralesional side of space as defined by the midline of the body, head, or retina Body-centred Heat-centred Retinocentric
Allocentric USN
Neglects the right side of individual items regardless of where the items appear with respect to the viewer.
Stimulus-centred
Object-centred
Other USNs
Distinguished by not only reference frame but also sensory modality, regions of space affected, or mode of output. (E.g. neglect dyslexia, neglect dysgraphia)
Which attentional network is affected in neglect?
Conflicting evidence (neuropsychological & neuroimaging)
Disorder associated with diverse presentations
Both DAN & VAN are involved via complex dynamics
(Involving alerting, orienting and conflict-monitoring)
Consciousness
Consciousness is a subjective experience
Sentience (Phenomenal awareness, subjective experience)
Access to information (ability to report content of one’s experiences of the world)
Self-knowledge (conscious awareness of ourselves)
Measuring conscious experience
Libet experiment
Brain imaging
Libet experiment - showed that the brain conducts the action before we are conscious of it
Failures to report a conscious experience may be due to failures of attention, memory, inner speech rather than the absence of relevant conscious experience.
Can ask people in a vegetative state to imagine certain activities for different answers to questions. Communicated with them- they were actually conscious
Theories of consciousness
Baar’s Global Workspace Theory
Dehaene & Nacchache’s Theory
Baar’s Global Workspace Theory:
- Unconscious processes take place in local modules distributed across the brain
- Conscious processing involves global access to these widespread modular representations
- Competition among processors and outputs for a limited capacity resource (GW) that “broadcasts” information for widespread access.
- Dynamic, flexibility in processing
- GW capacity limits correspond to the limits typically placed on focal attention or working memory in many cognitive models.
Dehaene & Nacchache’s Theory
- Baar’s model further developed with proposed connections to particular brain systems
- Consciousness (both in the access & phenomenal sense) occurs when & only when the relevant content enters the larger global network involving both primary sensory areas as well as many other areas including frontal and parietal areas associated with attention
- Conscious perception begins only with the “ignition” of larger global network; activity in the primary sensory areas will not suffice.
Anil was sitting in bed at 11pm and reading a book. He is suddenly distracted by a loud scream coming from outside his house.
Which specific attentional system will be activated as a response in this situation?
A. Executive
B. Orient
C. Alert
D. Spatial
C.Alert
