Lecture 20: Consciousness Flashcards
Consciousness involves
having access to information: The ability
to report on the content of mental experience (e.g., perception,
emotion, imagery), without knowing about the processes that build
up to that content/experience
* E.g., Chess player can memorize the configuration of an entire
chess board without knowing exactly how they did it
(underlying process)
Also typically involves some aspect of sentience: First person,
subjective experience of thoughts, perceptions, and feelings
Attention is the gateway to consciousness
- Change blindness and inattentional blindness If you don’t pay attention to it, you’ll miss it
- Attentional blink
- Look for the numbers amongst letters
-People usually notice and
report the first number,
subsequently miss the
second number
Conscious vs. Unconscious Processing
Whereas unconscious experience (even of high-level, semantic
tasks) can happen in posterior regions of the brain, conscious
experience is associated with widespread activity that includes
more anterior parts of the brain such as the frontal and parietal
lobes
* Conscious processing requires engagement of the fronto-parietal
attention network
High-level neural regions track conscious experience
- Binocular rivalry:
Presented with a stable, ambiguous stimulus
Perceptual
experience of
switching
between the 2
images
When your attention/conscious experience is on the face, more activity in FFA;
if conscious experience is of the house, then more activity in PPA!
Visual word form area (VWFA)
Responds more to alphabets
you’re familiar with
- Priming task: Presented symbols sequentially, occasionally with a word
- Behaviorally, people often miss the word, but will show priming effects when later
presented with a word-stem completion task - Compare brain activity for words they report seeing vs. don’t see
You see activity in VWFA regardless of whether the individual
reports seeing the word or not, but you get the strongest
activity in VWFA if the person reports seeing the word, AND you
also get widespread activation in other frontoparietal
regions
activation of high-level regions is not sufficient for
consciousness (sometimes active even during unconscious processing)… requires much more widespread neural regions,
particularly other areas within the fronto-parietal attention
network
Disorders of Consciousness
Anesthetized individuals show much lower overall neural network
connectivity than awake patients
- In the medical arena, scientists are still trying to understand whether
people in unresponsive wakefulness state (UWS) or minimally conscious
state have any remaining consciousness at all
Are UWS Patients Conscious?
Disorders of Consciousness
* Bekinschtein et al.: Trace conditioning paradigm
Play a tone, introduce a delay for several seconds, then shock
* Logic: Patients will only acquire a standard conditioning response (i.e.,
increased SCR) if they become aware that the tone and shock are
linked (not merely implicit learning… involves some aspect of explicit,
conscious learning)
Individuals in a UWS do show trace conditioning effect, but
anesthetized patients do not à suggests that people in a UWS might
have some level of awareness of what is going on around them
Disorders of Consciousness
* Visual imagery in unresponsive wakefulness state (UWS) patients
- Visual imagery often evokes similar brain activity to actual perception
- Ask individual in scanner to imagine 2 activities: playing tennis
(activates SMA), vs. walking through house (activates PPA)
UWS patient activates the expected regions during visual imagery,
similar activity compared to controls
Not just an automatic response (don’t show same activity when just
hearing the word without imagining anything)
However, not all UWS patients show modulation of brain activity based on
instructions (5 out of 54), and only 1 patient could actually use this activity as
a mode of communication (e.g., “Imagine playing tennis to say yes, imagine
walking through your house to say no”)
Summary: Disorders of Consciousness
* Some studies/methods seem to suggest that UWS patients do possess
some conscious awareness (trace conditioning, visual imagery), whereas
others don’t
* Limitations:
Not all patients show the same effects! Some variability…
* Ideally should compare all these different measures in the SAME patients
- Posterior regions of the brain are engaged in
unconscious processing
Posterior regions of the brain are engaged in unconscious processing, but
more widespread activation, including what is required for conscious experience?
frontal and parietal lobes, is
required for conscious experience (fronto-parietal attention network)
High-level neural regions that track conscious experience (give 2)
FFA, PPA track conscious experience
Visual word form area (VWFA)
More active for words/consonant strings
in familiar languages than line drawings, digits, or letters in other
languages
Corpus callosum
Fiber tract that connects the left and right hemispheres
of the brain – severing corpus callosum results in dissociation of
conscious experience amongst the 2 brain hemispheres
