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32 Cards in this Set

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Consciousness, is
sometimes it used to hide as a study of attention, unfashionable, very 'slippery' concept.
David Chalmers distinction: The easy problem..
-Finding the neural correlate of conciousness (NCC)
-Explaining the ability to apply info to thinking and behaviour
-Explaining the ability to focus attention, recall items from memory, integrate perceptions, etc.
David Chalmers distinction: The Hard problem..
-Why does consciousness feel the way it does?
-Why does it feel like anything?
David Chalmers distinction: The Hard problem, why is it hard?
"The problem of consciousness, simply put, is that we cannot understand how a brain, ie, a granular lump of biological matter, could be the seat of human consciousness, How could that 'lump' be conscious? or conversely how could I, as a conscious being, be that lump? (Akins, 1993)
The Hard problem with consciousness, why is it hard?
Nagel
Bats
Tomas Nagel (1974) - what is it like to be a bat? we can never know what its like to be a bat.
-Bats are mammals, they are conscious, but their consciousness is alien to us.
-They fly and hand upside down, we can imagine what it would be like to behave like a bat, but we cannot imagine what it is like for a bat to be a bat.
The Hard problem with consciousness, why is it hard?
Nagel
Objective
-Bats experience is subjective, scientific knowledge attempts to be objective.
-Study of objective science can never reveal the character of subjective experience,
The Hard problem with consciousness, why is it hard?
Nagel
Other humans
-We can use our imagination to know what its like to be George Clooney, but this is accessible to us because we base our imagination on own experience.
-We need subjective experience of being human to imagine the experience of others
-A Martian could not learn from objective facts what it is like to be human.
The Hard problem with consciousness, why is it hard?
Nagel
Overview
Physical facts are objective
Consciousness is subjective
SO consciousness can never be explained by physical facts
is this right? are the only objective facts physical? are the objective and subjective irreconcilable?
How do we study consciousness?
Patient studies: blindsight, agnosia (DF)
Masking studies: healthy controls
Split brain studies
Readiness potential (Libet)
Non conscious processing: Patient studies...
Consciousness seems to be unitary and crucial for mental activity
BUT without evidence that much mental activity goes on without us being aware of it.
Non conscious processing: Patient studies...
Blindsight
-Certain neurological damage renders parts of V1 inactive
-The parts of the visual field that correspond to the damaged regions in the V1 will be 'blind'
-The patient will deny all visual experience in these regions
-Flash a light onto that part of the retina and they will say there is nothing there so no conscious experience.
Non conscious processing: Patient studies...
Blindsight
However.. if the patient is asked to guess if there is a like in the blind region they perform better than chance (95%), this is called blindsight.
Implies V1 is necessary for conscious visual experience but unconsciously routes for visual info exist, necessary but not sufficient.
Non conscious processing: Dorsal & Ventral processing routes:
-After V1, visual pathways split into dorsal and ventral pathways in extra-striate cortex
-It is theorised that these pathways fulfil radically different functions (Milner, Goodale, 1995)
Non conscious processing: Dorsal & Ventral processing routes:
Ventral..
'what' pathway, slow, associated with conscious visual processing, conscious perception.
Milner and Goodale studied patent DF who had suffered damage to the ventral 'what' pathway
Non conscious processing: Dorsal & Ventral processing routes:
Dorsal..
'where' pathway, fast, movement sensitive.
Dorsal and Ventral systems work in parallel, normally.
Non conscious processing: Patient DF..
Visual form of agnosia,
No conscious perception of size, orientations or shape of objects
BUT could frequently perform appropriate actions with objects like picking up and posting through a slot although orientation not identified.
Dissociation between consciousness and action
Maybe 'consciousness' is not as important as on might think?
Non conscious processing: Patient DF and blindsight summary:
-Patients with lesions to primary visual cortex occasionally retain some visual abilities: better than chance on discrimination tasks, spatial navigation and coordination (avoid obstacles, etc)
-Thought to be because of the other 'backdoot' pathways that send signals to the dorsal stream the 'where' pathway.
Non conscious processing: Patient DF and blindsight summary:
The dorsal stream..
-mediates spatial processing and
-interaction with environment
-But the neural activity in these structures does not (is not alone sufficient to_ enter into consciousness.
Non conscious processing: Masking studies..
Objects substitution studies,
masked priming studies,
Non conscious processing: Masking studies, Object substitution masking studies..
-Masking occurs when a stimulus impairs perception of a nearby stimulus
-Object substitution masking occurs when attention cannot select a target object before it vanishes
-A mask is visible at the target location after the target has vanished
-Some visual info survives masking
-Subjects are accurate at reaching to grasp a masked shape even though they cant consciously see it!
Masked priming
The meaning of visual info can survive some kinds of masking
-participants must complete the stem to make any word other than the word that was masked
-They are more likely to use masked word which indicates subconscious influence on behaviour
NOBODY KNOWS..
what is special about neural activity that leads to awareness!
Split brain studies..
-The 2 hemispheres of the cortex are connected by the corpus callosum
-Provides info transfer between left and right
-Certain patients with severe epilepsy had their corpus callosum cut, in an effort to contain epilepsy to one hemisphere
-Can set up experiments which reveal surprising separations in function between halves.
Split brain studies..
Sperry's experiment:
-Objects presented to either right hand or left hand,
-words shown to the right visual field (RVF)or left (LVF)
-participants asked to id the object or select the object from a group of out of sight objects
-asked to id the word either verbally or by pointing to a word
Split brain studies..
Sperry's experiment results:
-Words presented to LH can be spoken
-Words presented to RH cannot be spoken, but can cause left hand to select object
-Participants will usually not be aware of why object selected by RH; Confabulation
Split brain studies..
Sperry's experiment results:
-If emotionally salient stimulus presented to RH
-Emotional response can result but again, participants not aware of reason;confabulation
Split brain studies..
Sperry's experiment, Left brain:
Language
Math calculation
Controls right side of body
receives visual signals from eye only
Split brain studies..
Sperry's experiment, Left brain:
Visual and spatial skills
controls left side of body
receives visual signals from left side only
split brain studies:
-functions of LH and RH can operate semi-independently
-speculation about 2 consciousnesses at same time?
-key point is splitting of functions which are usually associated with consciousness
Libet study:readiness potential
Benjamin Libet (1985):
Investigated timing relationship between deciding to make a movement and neural activity which precedes movement "readiness potential"
Participant decides to flex wrist at some time measured by position of rotating dot 'will', readiness potential measured by EEG
Actual time of movement measured by EMG (electromyography) FOUND THAT the readiness potential appeared before the decision to lift the finger.. interpretation controversial.
Haynes' study:
Found that brain activities had already occurred before the participants made the conscious decision of pushing a left or right button
Could predict what a participant would do 6 seconds before that participant is aware of his or her choice
implications for 'free will'
conscious decisions are preceded by unconscious processes in the brain by about a third of a second, so not decisions not made consciously.
Conscious initiation of decisions is an illusion
Libet's results and interpretation of data are very controversial due to the difficulty of timing intentions.