Lecture 12: Clinical Cases Flashcards
What does having activity in the sensory areas of the brain tell us about someone’s state of consciousness?
Having activity in the sensory areas of the brain tell us nothing about consciousness. When patients of vegetative state and coma etc are made listen to sounds, their auditory cortex is active. And we also saw before in the data that these cortices can show activity for unconscious information as well so it isn’t distinctive.
In what areas can we look for activation as markers for consciousness?
There are certain hubs in the brain (IPC, PCC, mPFC, ACC) that are also involved with the global workspace that we can look into, as already mentioned. We can look at the connectivity and integrity profile of the patients to see the consciousness level.
How else can we use brain activation as an indicator of consciousness?
We can also look the connectivity of the networks during the default mode. This is again related to global workspace as well and can tell us about the patients’ consciousness level. They already tried this by putting patients under fMRI and doing a functional connectivity analysis. It was found that on a group level the Default Mode Network integrity is a good measure to explain loss of consciousness.
How effective are these approaches at estimating one’s level of consciousness?
Although these approaches are getting much better, they still can’t give a definite answer in single cases. There is strong correlation between their conscious state and the DNS integrity. But it doesn’t separate the groups as clear as we want.
Describe another method, outside the use of fMRI, to measure a person’s state of consciousness
Another way to measure is the minimal energetic requirement of awareness. FDG-PET is used to measure the energy. It is glucose labeled with radioactive tracer molecule (injected), this creates a map of glucose uptake in all regions of the brain. A high correlation between the metabolic index and the consciousness state of the patients was seen. There was also a follow-up done, and it was seen that there’s a somewhat clear categorisation between patients (their first measurement) who got recovered and who couldn’t recover. There are still outliers, so again, it isn’t a 100% accurate measure on individual level.
How did these FDG-PET studies lend credence to GNWS theory?
Reductions in frontal and parietal metabolism, so where the GNWS is, was seen during loss of consciousness.
Describe the procedure of the study by Monti et al. ( 2010) which attempted to establish patient’s state of consciousness
They use an imagination task as an active task. They ask patients to imagine walking around their house or playing tennis. Patients with disorders of consciousness have difficulties expressing their conscious experiences. The brain is used as an output patient to see whether the patient starts to process these imaginations.
Imagining the house requires spatial navigation activation in the brain to layout how the house looks like and see how it looks like. In the study, they focused on parietal regions that are known to be involved in this. And later, also in their second paper, they focused on the para-hippocampal regions. Both light up when this imagination task is done in healthy participants.
Imagining to play tennis light the supplementary and pre-supplemantary motor areas up, in the medial of the prefrontal cortex. Regions that involved in planning complex motor actions and planning sequences of motor actions.
Evaluate this measurement methodology
A good thing about this is the system is very simple and robust. There is consistent activity in these areas in healthy subjects. There is very little variability, which makes it a great measure.
Describe findings of previous research which lead to this study by the full Monty
In the study of 2006, they questioned what would happen if a VS patient is asked to imagine playing tennis or walking around the house. They did this on a patient with bilateral damage to frontal the frontal lobes. She had a clear sleep-wake cycle but was unable to show any conscious behaviour, fully unresponsive.
When participant is asked to imagine either one of the scenarios, activation in the auditory cortex is seen. So at least the initial part of the process is working in the brain, potentially the patient can transfer this info to higher-order regions and see what to do with the task, and respond correctly.
When the activation in this patient’s brain and the healthy subjects’ brains were compared, it was shown that they’re correlated. The active parts overlap. Therefore the researchers concluded that that the patient is fully conscious. Although the clinical diagnosis suggests that she was not
This conclusion obviously let to a lot of critique and questions. Describe one of these
What if this activity observed is unconscious response? What if when we present the word, that generates automatic associations and automatically activate them in an unconscious way. So a feedforward automatic response that has nothing to do with consciousness.
What response were there to these criticisms?
Their other paper responded to this questions. It can be seen that both this patient and the health patients show that same BOLD response, very strong and also lasts very long, then reduces back again. => Durable information maintenance. The patient is actually performing the task for 30 seconds continuously that is conscious. If it was unconscious, this brain activity pattern would be much less durable, with a weak that dies out quickly
What is the aim of the Monti paper?
The Monti paper questions whether we can use this activity pattern to report consciousness and replies to the follow-up questions that have arisen.
How did Monti’s paper differ to that of the previous one methodologically?
The previous study was a case study, but this was has 54 patients who all did the tennis and house.
What were the results of the study?
In these 54 patients, 5 could do the imagination task (at least one of the conditions). 5 out of 54 is a high amount as it is about 10%. Even though they are diagnosed as VS (unconscious), the brain scans reveal that they can still do imagination tasks.
How has this active paradigm developed to further become a tool?
Now the idea is communicating with these brain-damaged patients by using the brain scans. Patients are asked to imagine playing tennis if they want to say “yes” and imagine walking around the house if they want to say “no”.
