Wednesday, 29 October 2008

Are brain damaged people who confabulate even trying to remember?

When a patient with brain damage provides bizarre answers to questions about their life or their recent activities, they are said to be confabulating. It's nearly always associated with damage to the frontal cortex and has traditionally be construed as a problem with memory retrieval - a mixing up of real memories with imagined facts. But now Gian Zannino and his associates have proposed a new explanation. Their suggestion is that confabulation often doesn't involve memory at all. Rather, they say it reflects a basic inability to select the appropriate mental process for the task at hand.

Zannino's group studied patient M.L. - a 55-year-old woman who frequently confabulates following an aneurysm in the front of her brain. They compared her performance on a range of psychological tests with that of two patients with frontal lobe brain damage who don't confabulate, and with five healthy controls.

The researchers showed first that M.L., but not the other participants, confabulated just as much regardless of question difficulty. So, for example, she gave bizarre, incorrect answers whether she was describing the last time she'd travelled by ship ("I went, I took the ship in Lyons and I went to Great Britain, then I sailed round the island, because I had to go opposite St. Paul's island"), or whether she was answering a deliberately impossible question about the job held by Baudelaire's sister ("tailor"). By contrast, in the case of impossible questions, the control participants would simply say they didn't know. The researchers said that as M.L.'s tendency to confabulation doesn't vary with the difficulty of memory retrieval, it undermines the idea that it's inherently a memory retrieval problem.

Secondly, the researchers showed that M.L. produced bizarre answers to tasks that didn't involve memory, and that she used the wrong mental process in a word definition task. In the former situation, she invented new features when asked to copy a simple line drawing, and in the latter case she gave the origins of words rather than their definitions.

Zannino's team concluded by arguing against an intimate link between confabulation and recollective processes. "We believe that the present case report provides evidence that in confabulators the lack of strategic control might occur at a very high hierarchical level in the control of mental processes - that is, at a level where confabulators have to choose between engaging in an attempt to recollect or perform some other less demanding mental process..."

ResearchBlogging.orgGian Daniele Zannino, Francesco Barban, Carlo Caltagirone, Giovanni Carlesimo (2008). Do confabulators really try to remember when they confabulate? A case report Cognitive Neuropsychology, 25 (6), 831-852 DOI: 10.1080/02643290802365078

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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