Week 10 Lecture 1 Flashcards
Steve Pinker’s Categorisation Model
Self knowledge - the feeling of I, the perception of being oneself.
Access to information - we can report the content of mental experience without awareness of the neural processes. Conscious vs unconscious processing.
Sentience - what it is like to be something. The feeling you have of yourself and the world. These feelings are qualia. Emotions are a qualia - the hard problem is explaining these feelings in terms of brain activity and understanding where they come from.
Sensory binding
Any skilful motor action e.g. playing an instrument, tying shoelaces.
Turning your automatic behaviour into an explanation is very difficult as your conscious mind does not know how it does it.
Visual binding
Features are processed in separate retinotopic maps in visual cortex but perception is integrated.
It has been suggested that when our brain areas vibrate at the same frequency (40Hz) this is binding of features of stimulation.
Give two examples of having access to information without being aware of it.
Blindsight = Patients with visual cortex damage can respond to visual stimuli in the blind part of the visual field without being conscious of it.
Weiskrantsz (1974/86) suggested that subcortical networks underlie blindsight - the visual stimulus is being represented in other parts of the brain.
Subliminal perception = visual information being presented so briefly that the subject is unaware of it yet biases the processing of stimuli.
Originally 100s papers by Anthony Marcel 1983 but have not been replicated - treat with caution.
When learning becomes unconscious
Petersen et al 1998.
When you are learning how to do something you are aware of it then it becomes automatic and you are not aware you are doing it.
Conscious processing is used during practice of complex skills e.g. driving, language. Consciousness improves processing efficiency by moving it into unconsciousness.
2 tasks in the study - verbal task (new verb learning) and motor task (maze tracing). Ability increased as it became an automatic process.
New skill - frontal areas more active.
More automatic - frontal areas not active, occipital and parietal areas are.
Free will experiments
Libet et al 1983
Subjects instructed to press a button freely and note when they felt the urge/made the decision to press the button by looking at a second hand on a clock (1 revolution in 3 seconds). Measured EEG.
Readiness potential starts 250ms before intention to press button. And about half a second before action taken.
Could be that free will is an illusion or that the experiment is too simple to require actual consciousness.
Soon et al 2008
Replicated the above using fMRI - unusual as poor temporal resolution.
Found that the action is predicted seconds before the awareness to act. This is before the decision or the action.
How to find a neural correlate of consciousness.
Crick and Koch (1998)
1. Use a paradigm where the stimulus remains the same but the content of consciousness changes (awareness of stimuli).
2. Observe how the changes in consciousness are reflected in brain activity.
What is a bistable stimulus?
Stimulus stays the same but the perception of the stimulus changes e.g. Necker cube or structure from motion.
What is binocular rivalry?
Present 2 different stimuli (2D images) one for each eye, stereoscopic vision (combining the two stimuli) creates a 3D structure from the 2 images if related. If you show 2 unrelated images the brain will flip flop between them.
fMRI correlates of stimulus detection
Dehaene et al 2001
Visual detection is associated with amplified left word form area activity. And widespread activity in the frontal, temporal and parietal cortex.
Word stayed the same but came in and out of awareness (visible or not).
Visual cortex was active when visible and not visible.
Parietal and occipital cortices only active when in awareness.
Auditory detection neural correlates of consciousness using fMRI
Sadaghiani et al 2009
Participants presented with soft tones, so soft that they were heard and sometimes not heard. Sound not detected, auditory cortex activated. Also activity in the frontal lobe and parietal love when sound was detected and entered consciousness.
EEG correlates of stimulus detection
Sergent et al 2005
First 200ms waves similar if stimulus visible or not.
At 100ms it was not in awareness, but visual cortex active.
At 576ms it had entered awareness and there was now frontal, parietal and occipital activation.
