4. Consciousness enters the lab Flashcards
Posterior part of inferior temporal cortex
containing information about head position - basic aspects of face perception
What are main findings from research conducted by Doris Tao?
She researched face-selective cells in macaque monkey’s brains.
She observed posterior-anterior gradient: areas becoming increasingly orientation invariant and responding more to specific faces.
Anterior part of inferior temporal cortex
responding to specific faces/individuals - more complex aspects of face perception
What about areas in the middle of inferior temporal cortex?
They contain single cells highly selective for particular features such as hair or iris.
Binocular rivarly experiments in monkeys
Face-selective cells in IT respond when the face is dominating (seen)
Where in the brain perceptual modulation can be found?
Mainly in high level brain regions (lateral PFC, frontal eye fields, PULVINAR, superior temporal sulcus/IT) - regarding binocular rivarly/
Binocular rivarly experiments in humans
Using house and face stimuli and investigating effects on two areas in the ventral stream:
PPA - house area
FFA - face area
fMRI (BOLD) singal measurement
Results:
PPA - more active when house seen (=dominant)
FFA - more active when face seen (=dominant)
however, no preparatory activity was detected (probably due to low temporal fMRI resolution)
Where perceptual modulation is not present in binocular rivarly?
V1 -> which makes sense, because V1 sees the same input all the time (however, some perceptual modulation may be present due to feedback proceses)
What are advantages and disadvantages of binocular rivarly?
+ good for studying spontaneous switches of perception
- not optimal for isolating NCC (no unconscious condition)
- difficult to seperate cause and effect
- is increased firing of IT/PFC cause of switch to face percept or the consequence of it?
=> areas of improvement -> neural measures with better temporal resolution
study paradigm van Gaal - Can the meaning of mutliple words be integrated unconsciously?
- masked vs not masked condition
- 2 x 2 design: prime (written in arabic/verbal notation), target (written in arabic/verbal notation)
- task: is the number bigger or smaller than 5?
results:
- main effect: sligthly faster if target is arabic (ex: 6)
- congruent trial: faster response, higher activation of relevant motor cortex
- semantic processing: system extracts the information from the prime to apply it to the target
Experiment - unconscious sounds
Participants were required to detect beeps.
Beeps -> at a threshold, making it tricky to detect them
Detected sound => widespread activation + auditory cortex active
Non-detected sound => local activation of auditory cortex
How to measure consciousness in objective tasks?
consciousness = INDEPENDENT VARIABLE (masked/not masked)
measurement across ALL trials
method: task performance, averaged across many trials
there is objective correct answer on each trial
How to measure consciousness in subjective tasks?
consciousness = DEPENDENT VARIABLE (seen/unseen, high/low confidence)
measuring consciousness on every SINGLE trial
method: asking about stimuli (yes/no, graded versions of perception, confidence scales), post-decision wagering -> betting how good you performed
there is no correct answer -> focus on subjective experience
post-hoc trial sorting is used to select conscious and unconscious trials
Signal detection theory
Looks at how humans make decision based on strength of the signal and their confidence. in uncertain situations There are 4 possible outcomes that can occur in detection task, depending whether observer responds ‘‘yes’’ or ‘‘no’’ to the presence of signal:
- hit (present stimuli, response “yes”)
- miss (present stimuli, response “no”)
- false alarm (absent stimuli, response “yes”)
- correct rejection (absent stimuli, response “no”)
What is response bias?
a behavioral tendency to respond “yes”, which is independent of sensitivity. Also referred to as “criterion”
