Neurocognition of spatial memory : studies in patients with acquired brain damage and healthy participants

Abstract

Spatial memory is an essential cognitive process that is used to encode the space around us, for example when travelling to our job or when trying to find our car keys. The enormous amount and the variety of spatial information we rely on to find our way through the world suggests it is a complex function which can be subdivided into a number of different components. This variety of processes makes it likely that it is not one single brain area that is crucially involved in spatial memory, but that several brain areas work together entailing an extended neural network for spatial information processing. In the first part of this thesis the different ways of encoding spatial information and the brain areas that are involved in these processes are studied. Therefore, patients with acquired brain damage due to Korsakoff amnesia and stroke were tested with a number of different spatial memory tasks, assessing object-location memory, spatial working memory and route learning.

From a purely functional perspective it has been argued that throughout evolution spatial memory might have developed into a function that works largely automatic. That is, spatial memory is used on a daily basis when trying to find our belongings or move around in the environment, but we are rarely aware of this process. We usually start thinking about it at the moment that something goes wrong and we get hopelessly lost. The underlying mechanisms of automatic encoding of spatial information are discussed in the second part of this thesis. First, automaticity of spatial memory was studied when walking a route through a building. It was found that basic aspects of route learning, such as landmark recognition are processed more automatically than more complex aspects that require a mental map of the route. Additionally, the integration of spatial information with other types of information, in particular temporal order information, was studied. It was shown that performance on a spatial and temporal order memory task improved under intentional learning conditions. Moreover, spatial and temporal order memory deteriorated with aging. The latter two findings indicate that spatial and temporal order information are not processed automatically in memory.