Dr Jenny Morton, Dr Lisa Saksida and Dr Tim Bussey from the Departments of Pharmacology and Experimental Psychology at the University of Cambridge, who led the research, tested normal mice and mice carrying the HD gene mutation. The task set was a choice between two visual stimuli on a touch-sensitive computer screen. If a mouse touched the correct stimulus, it was rewarded with food pellets; if it touched the incorrect stimulus, the lights went out and the mouse did not get a reward. Both normal and HD mice learnt to touch the correct stimulus with their noses and were able to learn the correct stimulus to obtain a reward by day 10.
The researchers also demonstrated that when the stimuli were reversed (so the stimulus that had previously been correct was now incorrect), HD mice struggled with the task although younger HD mice, who had not progressed as far in the disease, eventually learned it. When the mice were then presented with a new pair of stimuli, this proved too difficult even for the younger HD mice.
Importantly, and where the screen is so valuable, all the HD mice were physically able to complete the task (i.e. they were able physically to touch the screen and obtain rewards, even though their responses were often incorrect). This indicates that their poor cognitive performance was not secondary to motor impairments. It also confirms that mice with HD have cognitive problems that worsen with increasing age.
Dr Morton said, "We are very excited about the results from the touchscreen apparatus. For many HD patients, the cognitive and emotional symptoms are as disabling as the more obvious motor effects of the disease, and much effort is focused on understanding cognitive decline in HD".
"Useful cognitive testing has been a bottle-neck in developing new treatments for this aspect
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Source:University of Cambridge