Writing in Neuropsychologia, a study led by Giuseppe Iaria, a University of British Columbia Faculty of Medicine and Vancouver Coastal Health Authority postdoctoral fellow, used functional magnetic resonance imaging (fMRI) together with behavioral studies to assess and characterize the navigational deficiencies of a patient who is completely unable to orient within any environment, getting lost even within the neighborhood where the patient lived for many years.
This is the first case of a patient who, without apparent brain damage or cognitive impairment, is unable to orient within any environment. Researchers also believe that there are many others in the general population who may be affected by this developmental topographical disorder.
Brain malformations or lesions in parts of the brain important for navigation are known to cause navigation difficulties but no such defects or lesions in the patient's brain were detected. Moreover, a series of behavioural tests revealed that patient's problem was due to a specific inability to form cognitive maps.
"Navigating and orienting in an environment are complex cognitive skills, involving parts of the brain used for memory, attention, perception, and decision-making. It also requires using at least two distinct types of memory systems," says Iaria.
The procedural memory system involves using landmarks, distances, or following stereotyped movements to move between locations. The spatial memory system is more complex. When moving through an environment – familiar or not – a person creates a mental representation of the environment, called a cognitive map. It is the ability to "create" and "read" these cognitive maps that enables a person to navigate by following a route without getting lost.
"We suspect that this patient is not unique, and that there are others suffering varying degrees of selective developmental topographical disorientation," says Dr. Jason Barton, Canada Research Chair and director of the Human Vision and Eye Movement Laboratory where the patient was studied. "They might have a lifelong story of episodes like getting lost in their own house or neighbourhood, at school or at work, and having to rely on others for directions. In extreme circumstances, this can even lead to social isolation."
The researchers are now reaching out to the public, with a website specifically designed to inform people about orientation skills and reach others who experience topographical disorientation. This will help researchers to better understand the disorder and to develop rehabilitation treatments that may help affected individuals develop orientation skills. More information is available at www.gettinglost.ca
