Freethought & Rationalism Archive

beausoleil · 12-10-2002, 10:15 PM

As an old Russian friend of mine once said...

"Is DATA, is not model. If model disagrees with data, model is wrong"

Jesse · 12-10-2002, 10:50 PM

I guess what I'm asking is, does the data actually show that 100% of the people with this neurological condition exhibit the belief that people close to them have been replaced by doubles, or might there be occasional exceptions, as with Nash and his schizophrenic delusions?

ps418 · 12-11-2002, 03:18 AM

Quote:

Originally posted by Jesse:
<strong>I guess what I'm asking is, does the data actually show that 100% of the people with this neurological condition exhibit the belief that people close to them have been replaced by doubles, or might there be occasional exceptions, as with Nash and his schizophrenic delusions?</strong>

Jesse,

Im getting ready for work, so I only have a minute, but the answer is: no, apparently not everyone with this type of brain damage develops this delusion.

Gurdur · 12-11-2002, 12:17 PM

Quote:

Originally posted by Jesse:

I still don't see why it would be impossible. Imagine I'm in a VR simulation with my friend, and although in reality she's a 22-year-old woman in the simulation she looks like a 45-year-old-man; I wouldn't feel any connection to this face either, but I could still intellectually recognize who it really is and treat them accordingly.

In this case, your hard-wiring is fine. If you really want to, you can talk yourself into thinking you're George Soros.

Quote:

If a cognitively normal person with this condition just found it too disconcerting to look at people and have them appear "wrong", he could always adopt strategies like not looking directly at people when talking to them

To a degree, this is what Capgras' sufferers do - they ignore the problem as being too much of a source of discomfort - and they don't violently reject the people close to them, they just tend to sidle around them - they still can't accept that that peron is really the person they formerly felt close to.
Some Capgras' are well enough to recognise they are suffering from a disability, and they seek help themselves.

However, in other conditions, where normal cognitive functioning is even less impaired, such as the proprioceptive/leg syndrome I mentioned, the sufferer will continue to violently reject the offending "foreign" part, or eventually just try complete denial and switch out.

Quote:

--recognition of voice is not affected, right?

It is affected, since you have different parts of the brain telling you different things, and different hard-wired modalities take places in an automatic ladder of precedence - IOW, it doesn't matter at all about the voice, you'll only care about the face/feeling.

Quote:

I think it is possible, to some extent at least, to compensate intellectually for distorted senses--

Depends on the syndrome and the severity of damage - as well as other factors.

BTW, wih respect, you're making not very close comparisons - you're comparing non-specific drug reactions and otherwise OK cognition with neuro hard-wired conditions - they fall into a different class, and are better compared within that class, rather than with members of other classes.

Gurdur · 12-11-2002, 12:22 PM

Quote:

Originally posted by ps418:

....but the answer is: no, apparently not everyone with this type of brain damage develops this delusion.

The brain-localization for this particular function is itself not very specific, so it's not surprising that brain damage is fairly non-specific (being limited to saying IIRC front, right lobe, which is a rather broad locale), or severe dysfunction (e.g. severe psychological trauma and depression) is fairly non-specific and very contingent in causing Capgras.

It's not like the aphasias, or Korsakoff's/Wernicke's, or other similar, caused by damage to very localized, well-described brain areas.

MrDarwin · 12-11-2002, 12:40 PM

I thought Capra's Delusion was the idea that you had never been born, only to discover that the world would be a much worse place without you. This disorder is especially prevalent during the holiday season.

Jesse · 12-11-2002, 01:09 PM

Gurdur:
BTW, wih respect, you're making not very close comparisons - you're comparing non-specific drug reactions and otherwise OK cognition with neuro hard-wired conditions - they fall into a different class, and are better compared within that class, rather than with members of other classes.

Fair enough. Another comparison that might be closer is with people who have brain damage that causes them to neglect everything on one side of their visual field--I don't remember what this is called, but the idea is that they're not just blind to it, they actually are unable to conceptualize the idea of objects to their "left", say, so if they try to draw a clock they'll crowd all 12 numbers onto the right side. However, some of these people are able to intellectually understand that they're missing something, and adopt coping strategies like rotating their plate as they eat so they won't neglect half their food.

You said that their are some people with this damage who are able to recognize that the problem lies with them rather then the people they're close to, so I think we're not really in complete disagreement here, even if you don't think my reasons for suspecting there might be people like that are totally sound.

BTW, I remember reading somewhere--I think maybe in Ramachandran's <a href="http://www.amazon.com/exec/obidos/ASIN/0688172172/internetinfidelsA/" target="_blank">Shadows of the Brain</a>--that there was some similar delusion, I think a case of people failing to realize that they were paralyzed, that could be temporarily "cured" by squirting some cold water in the patient's left ear. Here, I found a page describing this phenomenon:

<a href="http://www.alumni.caltech.edu/~rbell/PhantomsInTheBrain.html" target="_blank">http://www.alumni.caltech.edu/~rbell/PhantomsInTheBrain.html</a>

Quote:

Some victims of serious brain injuries deny their problem, such as denying paralysis. Some without paralysis deny that they own perfectly functional parts of their body. Neurologists call this anosognosia, a fancy Greek-derived word that means you don't know yourself. Ramachandran had care of a woman who denied completely the paralysis of her left side. When asked to tie her shoes she failed but did not understand (or admit understanding) that she failed because she did not use her left hand. When asked to clap she raised her right hand in front of her and waved it back and forth, claiming that she was clapping. Ramachandran wanted to find out whether she truly did not know her paralysis or suppressed the knowledge.

'To find out, we took advantage of an ingenious experiment performed in 1987 by and Italian neurologist, Eduardo Bisiach, on a patient with neglect and denial. Bisiach took a syringe filled with ice-cold water and irrigated the patient's left ear canal - a procedure that tests vestibular nerve function. Within a few seconds the patient's eyes started to move vigorously in a process called nystagmus. the cold water sets up a convection current in the ear canals thereby fooling the brain into thinking the head is moving and into making involuntary correctional eye movements that we call nystagmus. When Bisiach then asked the denial patient whether she could use her arms she calmly replied that she had no use of her left arm. Amazingly the cold water irrigation of the left ear had brought about a complete (though temporary) remission from the anosognosia.'

So he performed the experiment on his patient.

'After the nystagmus I asked again, "How are you feeling?"

"My ear's cold."

"What about your arms? Can you use your arms?"

"No," she replied, "my left arm is paralyzed."

That was the first time she had used that word in the three weeks since her stroke.

"Mrs. Macken, how long have you been paralyzed?"

She said, "Oh, continuously, all these days."

This was an extraordinary remark for it implies that even though she had been denying her paralysis each time I had seen her over these last few weeks the memories of her failed attempts had been registering somewhere in her brains, yet access to them had been blocked. The cold water acted as a "truth serum" that brought her repressed memories about her paralysis to the surface.

Half and hour later I went back to her and asked, "Can you use your arms?"

"No, my left arm is paralyzed." Even though the nystagmus had long since ceased she still admitted she was paralyzed.

Twelve hours later a student of mine visited her and asked, "Do you remember Dr Ramachandran?"

"Oh, yes, he was that Indian doctor."

"And what did he do?"

He took some ice-cold water and he put it into my left ear and it hurt."

"Anything else?"

"Well, he was wearing that tie with the brain scan on it." True, I was wearing a tie with a PET scan on it. Her memory for details was fine.

"What did he ask you?"

"He asked me if I could use both my arms."

"And what did you tell him?"

"I told him I was fine."'

I think Ramachandran's theory about this was that the left brain has a kind of narrative module that explains our own behavior to ourselves, and is also responsible for "delusional" narratives in cases like these, analogous to Freudian "defense mechanisms". Somehow the cold water was believed to stimulate the right hemisphere and disrupt these defense mechanisms. If correct, this might suggest that the explanation for delusions does not lie solely with the brain damage, but also in the way other parts of the brain react to and compensate for this damage.

Gurdur · 12-11-2002, 01:37 PM

Quote:

Originally posted by Jesse:
....
If correct, this might suggest that the explanation for delusions does not lie solely with the brain damage, but also in the way other parts of the brain react to and compensate for this damage.

Yes.
Try confabulation in Wernicke's/Korsakoff's syndrome as a good example.

Delusions is not quite the right term; false induction and confabulation better fits the bill in many cases.

theyeti · 12-11-2002, 02:19 PM

Quote:

Originally posted by Jesse:
<strong>
I still don't see why it would be impossible. Imagine I'm in a VR simulation with my friend, and although in reality she's a 22-year-old woman in the simulation she looks like a 45-year-old-man; I wouldn't feel any connection to this face either, but I could still intellectually recognize who it really is and treat them accordingly.</strong>

In such a case, assuming that you're normal, I imagine that you would keep a mental picture of your friend in mind when dealing with the 45-year-old image. Most of the time when we think of someone, we picture their face in our mind (and to a lesser extent their voice) and this mental picture is what constitutes our "feeling" of that person, or is at least causally connected to it. I would guess that a person with Capras' disease is unable to do this, and so would never "feel" a person's presence regardless of what they look like externally. Just my guess.

theyeti

ps418 · 12-11-2002, 03:17 PM

Quote:

Gurdur: and they don't violently reject the people close to them, they just tend to sidle around them - they still can't accept that that peron is really the person they formerly felt close to.

That's surely correct in general, but there are some exceptions. Eliis and Lewis (2001) cite Silva et al (1994) as stating that some people with Capgras delusion have made preparations to kill the 'imposter.' However, I don't know whether these cases occurred in people who were otherwise psychiatrically 'normal' (i.e. whether their Capgras was secondary to head injury or to mental illness).

<a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=112872 68&dopt=Abstract" target="_blank">Ellis HD, Lewis MB, 2001. Capgras delusion: a window on face recognition. Trends Cogn Sci. 2001 Apr 1;5(4):149-156.</a>

<a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=781502 5&dopt=Abstract" target="_blank">Silva et al., 1994. A cognitive model of dangerous delusional misidentification syndromes. J Forensic Sci Nov;39(6):1455-67.</a>

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12-10-2002, 10:15 PM	#11
beausoleil Senior Member Join Date: May 2002 Location: US and UK Posts: 846	As an old Russian friend of mine once said... "Is DATA, is not model. If model disagrees with data, model is wrong"

12-10-2002, 10:50 PM	#12
Jesse Moderator - Science Discussions Join Date: Feb 2001 Location: Providence, RI, USA Posts: 9,908	I guess what I'm asking is, does the data actually show that 100% of the people with this neurological condition exhibit the belief that people close to them have been replaced by doubles, or might there be occasional exceptions, as with Nash and his schizophrenic delusions?

12-11-2002, 12:40 PM	#16
MrDarwin Veteran Member Join Date: May 2001 Location: Washington, DC Posts: 4,140	I thought Capra's Delusion was the idea that you had never been born, only to discover that the world would be a much worse place without you. This disorder is especially prevalent during the holiday season.

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