Consciousness Flashcards
Consciousness has been studied historically across 4 disciplines: Introspectionism, behaviourism, cognitive psychology and neuroimaging.
What are the rough decades and details of these movements?
Introspectionism began in Germany in the late 19th century, and was taken to America.
Behaviourism began in the early 20th C and dominated for half a century.
In the early 1960s cognitive psychology brought the focus back to mental proceses which behaviourism had ignored.
IN the 90s neuroimaging began using fMRI, MEG and PET to measure brain function by proxy
There are 3 philosophical perspectives on qualia; dualism (Descartes), materialism (Minsky) and epiphenomenalism.
What defines each perspective?
Dualism was defined by Descartes, claiming that the mind and body are distinctive processes. This belief is no longer widely held.
Materialismo states that states and consciousness are material and result from material interactions (eg neurons). “Minds are simply what brains do” - Minsky.
Epiphenomenalism claims that mental states are subjective products of the brain’s physical events but they play no causal role.
What is the difference between materialism and epiphenomenalism?
Materialism states that mental processes are material and result from material interactions, whereas epiphenomenalism claims that they are the results of physical processes but have no causal role.
In the 60s cognitive psychology emerged, putting an end to the dominance of behaviourism which negated the role of thought (the mind) in psychology because it was immeasurable.
Cognitive psychology put the brain back in psychology, but how did it still continue to ignore the mind?
Cognitive psychology thought of the brain as similar to a computer system, which still didn’t allow study of consciousness.
What is binocular rivalry, and how does the brain resolve it?
Binocular rivalry is when each eye is presented with a totally different image (not parts of the same image as occurs naturally).
The brain can’t fuse the images, so perception flickers between the conflicting images.
What is interocular suppression?
Interocular suppression is how the brain resolves interocular rivalry. The image from one eye will be suppressed, such as what happens with the roll-of-paper and hand experiment.
Why is binocular rivalry so useful for studying consciousness?
Binocular rivalry demonstrates that neurons at a higher level than V1 are alternating between perceptual options. At the level of V1, neurons respond continuously to the stimulus.
What are neural correlates of consciousness?
Neural correlates of consciousness are the minimal set of neuronal events/ mechanisms which are sufficient for a given conscious percept.
How did Logothetis and Schall (1989) show that the MST/ MT are responsible for stimulus selection during binocular rivalry, using a monkey trained to report seeing upwards or downwards motion?
Logothetis and Schall showed that neurons in the MST/ MT fired in synchrony with the monkey’s reported percept - ‘up motion’ cells fired when the monkey reported seeing up, and these cells ceased firing when the monkey reported seeing down.
Therefore they drew the conclusion that the recorded cell in the MST/MT was the cell which modulates consciously perceived direction.
In several studies, the Logothetis group showed that conscious perception increased up the hierarchy of visual cortical areas. (IT containing the most cells modulated by percepts and V1 containing the least).
How was this disproved by Pacual-Leone and Walsh (2001) using TMS?
A TMS pulse over MT (motion perception area) generates the impression of moving phosphenes.
When a pulse was added over V1 before the pulse over MT, the phosphenes remained. This is inconsistent with the feedforward model because the percept would have to pass through V1 on it’s way to MT, and if you knock out V1 the percept should have been interrupted.
When a pulse was added over V1 after MT, the perception of phosphenes was impaired. This is inconsistent with the feedforward model because if V1 is only involved preceding the percept, lesioning V1 after MT shouldn’t have had any effect.
This experiment showed that V1 feeds back to MT, and is therefore necessary for conscious perception.
TMS studies showed that feedback from V1 to MT is necessary for conscious perception. How was this strengthened by studies with blindsighted subjects, and a retinally blind subject?
Subjects with blindsight were missing V1 unilaterally. TMS over their remaining MT area on that same side elicited no phosphenes, again showing that V1 is necessary for this percept.
TMS over their ‘good side’ with remaining V1 did elicit the phosphenes.
The retinally blind subject still experienced phosphenes when TMS was used over MT
MT cell activity correlates closely with motion perception, but V1 doesn’t.
How was this NCC (neural correlate of consciousness) tested by Salzman et al (1990 & 1992) using single cell recording of a monkey?
Give a recording and electrical stimulation example.
The monkey was trained to respond when perceiving an upward motion, and the MT cell responsible for that motion direction perception was recorded simultaneously.
Psychometric and cellular data corresponded perfectly (1:1 ratio).
Electrical stimulation of that same cell then boosted likelihood that the monkey would perceive that direction.
