Lecture 7: Role of attention in consciousness and signatures of consciousness Flashcards
What does the cocktail party effect demonstrate?
Unattended salient stimuli can gain access to consciousness
How was this cocktail party effect studied in an experimental setting?
Dichotic listening paradigms: subjects are presented with two audio inputs in two sides of a pair of headphones and requested to report what is said through one input and ignore the other. Participants are then typically asked questions about the other input in some manner
What was concluded from the cocktail party and other divided-attention experiments?
Cocktail party and other divided-attention experiments suggest an unconscious semantic comprehension process
Evaluate this evidence for unconscious semantic comprehension
It’s not exactly water tight evidence because:
•Never sure whether subjects fully divide their attention
•Maybe participants just switch their attention very quickly
What did the scientists have to do in response to these criticisms?
The scientists had to come up with smarter designs regarding what processing goes on in the absence of attention (and therefore consciousness). They came up with the paradigm of innatentional blindness
Describe the innatentional paradigm discussed in the lecture
Subjects have to focus on the centre of a static screen where rapid series of numbers are presented and perform (for example) an N-back task. Images of either spider silhouettes or non spider silhouettes (e.g snowflake, butterfly) are shown around the periphery of the task (graded into the static) and participants are asked whether they noticed the spiders and checks are carried out.
Subjects who did not see the spiders are then selected and compare the processing in e.g fMRI between the two conditions where you present non-spiders.
What results were gathered from this inattentional blindness study?
Activity in the amygdala typical of a fear response was recorded both when the participants were consciously aware of the spiders and when they were not which was not observed when presenting non-spiders.
Describe Sergent and Dehaene’s work on EEG and attentional blink
They put together all the brain data when subjects saw the T2, and the ones when subjects didn’t. They also made one baseline data. It is seen that the activity dies out much quicker in the not-seen brain activity, but it is still present.
What is ECoG?
Electrocorticography (also called intracranial electroencephalography, iEEG). Mainly used in patients with epilepsy and during this procedures if the patient gives permission, neuroscientific studies are also done (while they already have electrodes inside their brain).
How has ECoG been insightful? Give an example
Dehaene and colleges did multiple studies with these patients. One of them investigated the activity during a masking experiment. The results are about unconscious (word wasn’t seen) and conscious (word was seen) experience.
Conscious or unconscious there is am initial reaction to the word. But only after we become aware of the word there is continued activity seen (indicated with the grey circle).
What conclusions can be drawn from this masking study?
Information can be processed unconsciously by the brain. It can activate several levels of information processing and mere brain activation doesn’t generate a conscious experience.
What has 1. fMRI and 2. (mainly) EEG/iEEG demonstrated about brain activity and consciousness? Thirdly how are these insightful?
> More widespread activity when conscious (fMRI)
> Activity in early visual cortex does not really dissociate conscious from unconscious processing, later processing does (mainly scalp EEG or iEEG)
> We can isolate “signatures of consciousness” with different imaging techniques (e.g. fMRI: frontoparietal activation, EEG: P3 ERP component). Reflecting the transition from unconscious to conscious.
Signatures of consciousness are what we measure with brain imaging tools. What do they reflect?
They reflect underlying neural mechanisms, such as feedback processing, but are not the mechanism itself.
What 4 signatures are mentioned in the book?
- A sudden ignition of parietal and prefrontal circuits.
- A late slow wave called the P3 wave (the P3b we talked about).
- A late sudden burst of high-frequency oscillations.
- A synchronisation of information exchanges across distant brain regions.
What do EEG/MEG/intracranial signal results show?
In EEG/MEG/intracranial signal results show signals that are a mixture of oscillations in different frequencies. Frequencies can be slow (theta and beta) or fast/high (gamma). There is also the power of the oscillations showing how strong they are. Also where peaks are happening is important.
