Week 11

Spatial and non-spatial working memory at different stages of Parkinson's disease

Parkinson’s disease (PD) is characterized through the deterioration of motor functions, produced through the decline of dopamine-generating cells. Owen et al. (1997) now suggests that parallel to this motor function degeneration, there is a deterioration of cognitive functions. In their study Owen et al. tested 21 patients with PD in different stages (mild and severe), being either medicated or non-medicated, on their abilities in three different kinds of working memory (spatial, verbal, visual). 


As they predicted, they found an increase of impairment parallel to an increase of severeness in the disease. Non-medicated patients with mild symptoms showed no impairment in all three working memories, medicated patients with mild symptoms showed an impaired spatial working memory but normal abilities for the visual and verbal task, and medicated patients with severe symptoms showed impairment in all 3 tests. It was concluded that first symptoms of PD occur in the frontal lobe (spatial) and then expanding to other brain areas. Compared to Patients with frontal lobe damage however, patients with PD show significantly less severe symptoms.

However, Owen et al. mentioned an extreme difference in task difficulty between the spatial task and the verbal and visual task. A slightly more difficult spatial task would be expected to show impairment even for the first condition. (210 words).

Nevertheless, this study failed to explicitly test any additional frontal lobe functions in PD, which makes it hard to evaluate the expansion of the impairment in these patients. Since frontal lobe patients show a complete destruction of the brain tissue, whereas PD only exhibits deterioration of single areas within the lobe, less severe symptoms might be expectable.

Week 10

Memory for Places learned long ago is intact after hippocampal damage

Many studies over the past decades suggested an important role of the hippocampus for navigation and orientation. A study by Maguire et al. (1997) found an enlarged hippocampus in London taxi drivers who through functional imaging, and Morris et al. (1982) even found impairments in navigation in rats with a damaged hippocampus.

A study by Teng and Squire (1999) however, examined a patient with virtually complete bilateral damage to the hippocampus. Patient E.P. (76 years) had amnesia in 1992 and moved to a new city in 1993. As expected, it was impossible for him to retrieve any information about the city he is currently living in. However, observing his virtually navigation skills for remote memories of the city he grew up in, showed no difference to controls. Teng and Squire concluded, that the hippocampus is necessary for the encoding of long-term declarative memories but seems to be spared in their retrieval.

It can be criticised however that E.P was asked 10 questions about navigating to different locations whereas controls were only asked a mean of 9.5 questions. More questions can improve an overall performance. Moreover, results of controls are given as rages, without stating a mean or SD. In the case of outliers, comparing E.P.’s performance with the controls can lead to misinterpretation (213 words).

Nevertheless, it is shown that navigation cannot be located in the hippocampus completely, since E.P was able to complete most of the given tasks without impairment.