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intermittent. If you happen to examine a patient when she’s asleep or when 
her consciousness is at a minimum, you may miss the 

À

 eeting evidence of 

that minimal consciousness. 

There are a lot of new technologies currently being used or on the horizon. 
One of these is the functional MRI scan, which measures blood 

À

 ow to the 

brain. By that, we can infer which parts of the brain are functioning and how 
much they’re functioning. PET scans also image blood 

À

 ow or metabolic 

activity in the brain so that we can infer brain activity. 

What about the notion of waking from a coma? When somebody is in a 
coma, can they wake up? The short answer to that question is it depends. 

The most signi

¿

 cant factor that 

determines whether someone can 
wake up is whether the cause of the 
coma is reversible. With reversible 
causes of coma, you absolutely can 
wake up. For example, someone 
with a toxic or metabolic cause 
that’s inhibiting brain function can 
wake up as soon as the toxin or 
the metabolic problem is removed. 

Trauma has a very poor prognosis because trauma represents actual brain 
damage. Seizures are a bit of a mixed bag. A seizure in and of itself can 
cause somebody to be comatose. If the seizure is the primary or sole cause 
of the coma, then treating the seizure can cause somebody to wake up from a 
coma. But sometime the seizures were occurring in the 

¿

 rst place due to a lot 

of underlying brain damage, which by itself is causing the coma. 

How good are we at predicting whether someone has any potential to 
wake from a coma? There are a few things that we do know: The longer 
that someone is in a coma, the lower their prognosis or statistical chance 
that they will wake up. The deeper the coma—in other words, the less brain 
function that there is—and the older the age of the patient, the worse the 
prognosis is also. Within 48 hours of someone entering a coma, prognosis is 
very uncertain. But by day 3 of a coma, using the neurological exam alone 

By day 3 of a coma ... we 
can make a very accurate 
prediction about the 
probability of someone having 
potential to awaken.

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Lecture 20: Myths about Coma and Consciousness

or with additional tests, we can make a very accurate prediction about the 
probability of someone having potential to awaken. 

Let’s look at some other myths surrounding brain function. What about 
getting knocked out? This is another TV and movie cliché, where someone is 
hit on the back of the head, maybe by the butt of a gun. He’ll be unconscious 
for an hour or so and then wake up with nothing more than a serious headache. 
Does this actually happen? You can knock somebody out by hitting him on 
the head, but he is unlikely to wake up with no injuries at any time after that. 
In fact, losing consciousness from a brain injury or from trauma is usually 
the threshold that will cause some permanent brain damage. 

What about amnesia? Another common TV and movie myth is that 
somebody with a head injury will lose all memories of who she is and what 
her life has been like up to that point. There’s a kernel of truth here in that 
a head injury, especially one hard enough to cause loss of consciousness, 
can cause loss of memory. However, it is a complete myth that people 
will forget who they are from a head injury or any neurological condition. 
If you have enough brain function to be awake, you know who you are. 
People who don’t remember their name or their identity have a psychiatric 
condition, not a neurological condition. 

Another brain myth that comes up often in the context of coma is the notion 
that we only use 10% of our brain. Unfortunately, this is a complete myth. 
We use 100% of our brain. There are many lines of evidence that support 
this—from anatomical studies to functional studies looking at PET scans, 
MRI scans, and functional MRI. The entire brain is functioning, and loss 
of 10% or 20% of the brain is actually correlated with a signi

¿

 cant loss of 

cognitive function. 

The brain is the most complex organ in the body—maybe the most complex 
thing that we’re aware of in the universe. Although we don’t fully understand 
brain function or how it generates consciousness, we understand a lot about 
it. We are getting an increasingly detailed picture of the different parts of
the brain: how they function, how they interact together, how they contribute 
to consciousness, and how damage to different parts of the brain can
impair consciousness. 

Ŷ

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Bauby, 

The Diving Bell and the Butter

À

 y

.

Parker and Parker, 

The Of

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 cial Patient’s Sourcebook on Coma

. 

Posner et al., 

Plum and Posner

’

s Diagnosis of Stupor and Coma.

1. 

What do we know about the neural correlates of consciousness—how 
brain function causes our conscious awareness?

2. 

Can someone really awaken after being in a coma for years?

3. 

What would you say about the idea that most people use only 10% of 
their brain function?

    Questions to Consider

    Suggested Reading

76

Lecture 21: What Placebos Can and Cannot Do

What Placebos Can and Cannot Do

Lecture 21

There’s also what we call nocebo effects. If these psychological factors 
or some of them can lead to the false impression that there is a bene

¿

 t 

from an inactive treatment, can there also be harm or perceived or 
measured harm from an inactive treatment? It turns out that there
can be.

A 

placebo is any inactive substance or intervention given as a real 
treatment. Any perceived response to a medical intervention 
other than a physiological response to an active treatment can be 

considered a placebo response. There are many types of placebo effects. One 
category is psychological effects. These include the desire of the patient to 
improve, to please the person administering the treatment, and to justify the 
risk and expense of the treatment. Another powerful psychological effect is 
con

¿

 rmation bias. This includes the notion that people tend to notice and 

remember events that con

¿

 rm their beliefs, biases, and desires. They will 

also miss, ignore, or explain away any discon

¿

 rming evidence. 

There are many other observational artifacts that contribute to placebo 
effects. An artifact is anything that causes an illusion in observation. One that 
scientists recognize is regression to the mean: In any system or any symptoms 
that 

À

 uctuate over time, any extreme in this 

À

 uctuation is more likely to be 

followed by a return to the mean, just from pure statistics. There are also 
observer effects. This is simply the understanding that the act of observing 
affects behavior and outcomes. For example, subjects in a clinical trial may 
be more compliant with their treatment when they’re being regularly seen by 
a health-care provider. 

There are also many nonspeci

¿

 c effects. That means that there are bene

¿

 ts of 

variables that are incidental to the treatment itself. For example, if you disrupt 
your stressful day to undergo a treatment, the treatment may be relaxing in 
and of itself. There’s also psychological bene

¿

 t from the therapeutic and 

caring attention of the provider. 

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What about expectation? There is a common belief that someone needs to 
have an expectation of bene

¿

 t from a treatment for there to be a placebo 

effect. This itself is a myth. However, expectation may enhance or increase 
the placebo effects that are occurring. 

Can there be real bene

¿

 ts to placebos? They are present. There are real 

bene

¿

 ts to placebos, but we have to put them in context to understand that 

they are very strictly limited. Placebo 
effects can cause a genuine reduction 
in stress from nonspeci

¿

 c  and 

psychological aspects of the treatment. 
And reduction in stress does reduce 
risk factors for many real biological 
disorders like heart disease. Muscle 
tension also responds to psychological 
stress. When you’re anxious or under 
a lot of stress, you’ll tense up your 
muscles, which can cause a lot of very 
real symptoms. Therefore, placebo effects that reduce stress will improve 
those biological functions. The perception of pain is also highly subjective. 
Anything that provides improved mood or comfort or the expectation of 
bene

¿

 t will improve or decrease this perception of pain. 

However, these limited and carefully delineated placebo effects should not 
be used to argue that placebos can have other effects that are not documented 
and not plausible. Placebos are not a panacea. In fact, systematic reviews 
of clinical trials have found no measurable mind over matter or biological 
placebo effect. 

So is there anything bene

¿

 cial to placebo effects? If so, is there any way to 

exploit them without deceiving patients and without using treatments that 
are harmful or contain unnecessary components? First of all, it’s important 
to remember that real and effective medical interventions come with placebo 
effects. This includes things like a good therapeutic relationship between 
the treater and the patient, a positive mood and outlook, overall healthful 
behaviors, and improved compliance with a necessary treatment. However, 
placebo effects cannot ethically be used to promote pure placebo treatments. 

There are real bene

¿

 ts 

to placebos, but we have 
to put them in context to 
understand that they are very 
strictly limited.