Disorders of spatial memory

Topographical Disorientation
Full article: Topographical disorientation or Developmental topographical disorientation

Topographical disorientation is a cognitive disorder that results in the individual being unable to orient his or herself in the real or virtual environment. Patients also struggle with spatial information dependant tasks. These problems could possibly be the result of a disruption in the ability to access one’s cognitive map, a mental representation of the surrounding environment or the inability to judge objects’ location in relation to one’s self.

Developmental Topographical Disorientation (DTD) is diagnosed when patients have shown an inability to navigate even familiar surroundings since birth and show no apparent neurological causes for this deficiency such as lesioning or brain damage. DTD is a relatively new disorder and can occur in varying degrees of severity.

Topographical Disorientation in Mild Cognitive Impairment: A Voxel-Based Morphometry Study was done to see if Topographical Disorientation had an effect on individuals who had mild cognitive impairment. The study was done by recruiting forty-one patients diagnosed with MCI and 24 healthy control individuals. The standards that were set for this experiment were 1.Subjective cognitive complaint by the patient or his/her caregiver. 2) Normal general cognitive function above the 16th percentile on the Korean version of the Mini-Mental State Examination (K-MMSE). 3) Normal activities of daily living (ADL) assessed both clinically and on a standardized scale (as described below). 4) Objective cognitive decline below the 16th percentile on neuropsychological tests. 5) Exclusion of dementia. (TD) was assessed clinically in all participants. Neurological and neuropsychological evaluations were determined by a magnetic imaging scan which was performed on each participant. Voxel-based morphometry was used to compare patterns of gray-matter atrophy between patients with and without TD, and a group of normal controls. The outcome of the experiment was that they found TD in 17 out of the 41 MCI patients (41.4%). The functional abilities were significantly impaired in MCI patients with TD compared to in MCI patients without TD and that the presence of TD in MCI patients is associated with loss of gray matter in the medial temporal regions, including the hippocampus.Tae-Sung Lim, Giuseppe Iaria, So Young Moon. "Topographical Disorientation in Mild Cognitive Impairment:A Voxel-Based Morphometry Study." 9 August 2010. 16 April 2011 .

Hippocampal Damage and Schizophrenia
Research with rats indicates that spatial memory may be adversely affected by neonatal damage to the hippocampus in a way that closely resembles schizophrenia. Schizophrenia is thought to stem from neurodevelopmental problems shortly after birth.

Rats are commonly used as models of schizophrenia patients. Experimenters create lesions in the ventral hippocampal area shortly after birth, a procedure known as neonatal ventral hippocampal lesioning(NVHL). Adult rats who with NVHL show typical indicators of schizophrenia such as hypersensitivity to psychostimulants, reduced social interactions and impaired prepulse inhibition, working memory and set-shifting. Similar to schizophrenia, impaired rats fail to use environmental context in spatial learning tasks such as showing difficulty completing the radial arm maze and the Moris water maze.

GPS
Recent research on spatial memory and wayfinding in an article by Ishikawa et al in 2008 revealed that using a GPS device reduces an individual’s navigate abilities when compared to other participants who were using maps or had previous experience on the route with a guide. A second possibility is that the visual set-up of each tool differs. GPS allows the user to only see a small detailed close-up of a particular segment of the map which is constantly updated. In comparison, maps usually allow the user to see the same view of the entire route from departure to arrival. Other research has shown that individuals who use GPS travel more slowly overall compared to map users who are faster. GPS users stop more frequently and for a longer period of time whereas map users and individuals using past experience as a guide travel on more direct routes to reach their goal.

Learning Difficulties and Spatial Memory
Nonverbal learning disability is characterized by normal verbal abilities but impaired visuospatial abilities. Problem areas for children with nonverbal learning disability are arithmetic, geometry, and science. Impairments in spatial memory is implicated in nonverbal learning disorder and other learning difficulties.

Arithmetic word problems involve written text containing a set of data followed by one or more questions and require the use of the four basic arithmetic operations (addition, subtraction, multiplication, or division). Researchers suggest that successful completion of arithmetic word problems involves spatial working memory (involved in building schematic representations) which facilitates the creation of spatial relationships between objects. Creating spatial relationships between objects is an important part of solving word problems because mental operations and transformations are required.

For example, consider the following question: "A child builds three towers using red and white coloured blocks of the same size. The lowest tower has 14 blocks; the highest has 7 more blocks. The intermediate tower has three blocks less than the highest one. How many blocks are in each of the three towers?" To solve the question, it is necessary to maintain incoming information (i.e., the text) and integrate it with previous information (such as knowledge for arithmetic operations). The individual must also select relevant (i.e., the spatial relationship between the blocks) and inhibit irrelevant information (i.e., the colours and textures of the blocks) and simultaneously build a mental representation of the problem.

Researchers investigated the role of spatial memory and visual memory in the ability to complete arithmetic word problems. Children in the study completed the Corsi Block Task (forward and backward series) and a spatial matrix task, as well as a visual memory task called the house recognition test. Poor problem-solvers were impaired on the Corsi Block Tasks and the spatial matrix task, but performed normally on the house recognition test when compared to normally achieving children. The experiment demonstrated that poor problem solving is related specifically to deficient processing of spatial information.