Why bother study decision-making in dementia? This is the issue tackled by a new paper by Prof. Manes’ team in Argentina. The paper from Prof Facundo Manes’ group, published in Nature (Neurology Reviews), indeed does provide the first ever comprehensive review of decision-making in dementia (including the neurodegenerative diseases), that I am aware of. There are certainly various reasons that I can think of, in complete agreement with the authors. Firstly, patients themselves suffer from abnormal decision-making, and this is bound to have an effect on their day-to-day lives. Secondly, it is possible that the medical profession may be able to do something about them one day. This is related to a third powerful reason, that each of the dementias carries with a unique ‘profile badge’ as they’d say on Facebook. This profile is a different type of response to decision-making situations, e.g. more conservative, more risky, more impulsive, more time-consuming, and it’s considered that this has something to do the part of the brain affected.

The link to the paper is here.

Nat Rev Neurol. 2010 Oct 12. [Epub ahead of print] Decision-making cognition in neurodegenerative diseases. Gleichgerrcht E, Ibáñez A, Roca M, Torralva T, Manes F from the Institute of Cognitive Neurology (INECO), Favaloro University, Castex 3293 (1425), Buenos Aires, Argentina.

I first became interested in dementia when I was studying my finals in Cambridge in 1996. Notwithstanding it, I did a Ph.D., awarded by the University of Cambridge in 2001. I was the first person in the world to demonstrate that patients with early behavioural variant frontotemporal dementia displayed a risky profile, but that it was not impulsive, because such patients took a long time to reach their problematic decisions. I note, interestingly, that this has been found to be a possible pattern of behaviour when patients with behaviour variant frontotemporal dementia are driving, anecdotally, but this has never been investigated formally to my knowledge, but these accounts have been very few in number, and do not constitute a reliable observation.

Most relevantly to Prof Manes’ article, I showed that the most likely place to pinpoint the pathology was the orbitofrontal lobe (or ventromedial prefrontal cortex), discussed as being important for ‘action selection’ in decision-making in the model proposed. This is closely connected with the ventral parts of the ‘striatum’ in the midbrain, and it is possible that the orbitofrontal lobe, ventral striatum and the insula have a special role to play in this decision-making, whether normally or abnormally.

The review contains a very nice picture of this ‘brain circuitry’, otherwise known in the trade as ‘distributed neuronal network’. It doesn’t matter if you go for another view of the brain, called ‘localization of function’ – decision-making without the orbitofrontal cortex is like a plasma screen without a cathode ray tube. I’ve got that right, haven’t I?

The most obvious feature of dementia, certainly in patients with Alzheimer’s disease, is memory loss. The authors allude to this being a problem in studying decision-making in dementia; when patients have other more prominent problems, making ‘pure’ decision-making hard to study. I found that my eight patients reported in Brain had no problems with standard tests, including those traditional tests of frontal lobe function.

I thought that this article was a brilliant contribution to the literature, and meticulously researched according to the plethora of published studies we are lucky to have so far.

Bravo!

Dr Shibley Rahman is an expert in behavioural variant frontotemporal dementia.