Going in the right direction?

Liam Myles responds to Emily Farran's article.

I was delighted to read Professor Emily Farran’s article ‘Finding a route to independence’ (November issue), on spatial navigation in neurodevelopmental disorders. The article concluded that impaired ‘cognitive maps’ underlie deficits in spatial navigation in individuals with Williams Syndrome (WS) and Down Syndrome (DS). However, on reading the article, I began to wonder if the navigational difficulties experienced by individuals with these neurodevelopmental disorders could be attributed to lower verbal abilities.

The article began by discussing a seminal theory by Siegel and White, which proposed in 1975 that spatial abilities are governed by both associative mechanisms and a cognitive map. A cognitive map can be defined as a representation of space that entails knowledge of the spatial relationships between objects contained within the environment. Crucially, cognitive maps facilitate flexible navigation using novel routes. Put simply, they help us find shortcuts!

Farran proceeded to discuss numerous interesting studies which seemed to suggest that cognitive maps are impaired in individuals with WS and DS. For example, one study required individuals with WS to walk around a university campus and, when prompted, indicate the direction of different landmarks which were not currently visible. The authors reported a disproportionate impairment in the ability to complete this task, compared to other tasks that are considered to be dependent on associative mechanisms. These results were taken as evidence of impaired cognitive mapping in individuals with WS and DS.

However, evidence for cognitive maps in humans is equivocal. It is difficult to determine the extent to which humans rely on cognitive maps during navigation as we have another brilliant tool at our disposal - language! Humans can use language as a ‘crutch’ to complete various complex navigational tasks, which may not otherwise be possible, and this often confounds experiments assessing the use of flexible navigation strategies. For example, when walking around a university campus, one might leave the psychology department and walk down the hill towards the library. Upon reaching the library, one turns right and crosses the grass, arriving at the campus café. One could quite readily derive the direction of the (now occluded) psychology department by a verbally mediated process that is based upon the memories of the directions and turns taken along the route. Indeed, our ability to use language to reason through spatial problems allows us to find novel routes through environments, without relying on a ‘cognitive map’.

How does this relate to neurodevelopmental disorders? Well, individuals with both WS and DS often have poor verbal abilities (see Bellugi et al., 1999 in Trends in Neurosciences). Therefore, such individuals may be less capable of using verbal reasoning strategies as a crutch when solving spatial tasks. Interestingly, individuals with DS show both poorer ‘configural spatial knowledge’ and lower linguistic abilities than individuals with WS (see the Bellugi et al. article again, and Farran et al., 2015 in Journal of Neurodevelopmental Disorders). These results suggest that lower verbal abilities could underlie deficits in tasks requiring flexible navigational strategies, rather than impaired cognitive mapping mechanisms. This raises an important question – to what extent can spatial difficulties encountered by individuals with these neurodevelopmental disorders be accounted for by poor verbal abilities? I would be interested to know whether others think we are going in the right direction with cognitive maps.

Liam Myles
Assistant Psychologist
Surrey and Borders Partnership NHS Foundation Trust

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