Prospective Memory Impairment In The Patients With Parkinson's Disease At The Early And Middle Stage

Parkinson's disease (PD) is a neurodegenerative disease which is characterized by movement dysfunction. The worst damage occurs in the dopamine-producing neurons of the substantia nigra, and the neurons degenerate in a characteristic way, forming clumps of protein called Lewy bodies. In the recent decades, people have gradually recognized that Parkinson's disease is usually accompanied by sensory, autonomic and cognitive disturbances. It is known that even in the early stage, the cognitive function is usually impaired. Its prominent cognitive impairments lie in attention, executive function, visuo-spatial functions and memory. These impairments are attributed to the disruption of fronto - subcortical neuro-circuits.Previous researches on memory deficits in Parkinson's disease mainly focused on the retrospective memory, but rarely on its prospective memory deficits. Prospective memory is memory for actions to be performed in the future. Einstein and McDaniel proposed an important distinction between event-based and time-based prospective memory. Event-based prospective memory is remembering to perform an action when some external event occurs. Time-based prospective memory is remembering to perform an action at a certain time. Kliegel, Katai and Altgassen have found some prospective memory deficits in Parkinson' s disease in different perspectives. But there had not been such a research on PM of Parkinson' s disease in China. The purpose of the present study was to explore the time-based and event-based prospective memory impairments in patients with Parkinson's disease. In addition, the relationship between prospective memory and the variables, such as age, education, duration, the side of onset and Hoehn-Yahr staging on patients with Parkinson's disease were analyzed.ObjectivesTo investigate the features of prospective memory impairment in patients with Parkinson's disease at the early and middle stage.Method:(1) Fifteen patients with Parkinson's disease and fifteen age- sex-education- and occupation- matched normal control subjects were enrolled in this study.(2) Background measures: MMSE, verbal fluency test and digital span test were performed to assess general cognitive functions.(3) All participants were asked to complete event-based and time-based prospective memory tasks. In the event-based prospective memory task, the subjects were asked to tap the desk whenever words of particular categories were presented. In the time-based prospective memory task, the subjects were asked to tap the desk at certain times.Results:There were no significant differences of performances of MMSE, verbal fluency test and digital span test between PD group and normal controls. In the EBPM task, there was a significant difference between these two groups (patients: 3.93±2.69, controls: 6.00±2.17, t= -2.318. P=0.028). In the TBPM task, there was no significant difference between the two groups (patients: 3.47±1.96, controls: 3.80±1.70, t=-0.498, p=0.622). The retrospective memory study did not show significant differences between two groups. And all participants could recall the rules in EBPM and TBPM tasks after the experiment. So, the impairment of EBPM in the Parkinson's disease patients did not result from the RM impairment, but from their failure to retrieve it spontaneously when the target words appeared. There were no relationships between age, education, duration, side of onset, Hoehn-Yahr staging and EBPM, TBPM in patients with Parkinson's disease. There was positive correlation between the EBPM task and verbal fluency test, digital span test, and between the TBPM task and verbal fluency test.Conclusions:(1)The EBPM was impaired and the TBPM was relatively spared in Parkinson's disease patients.(2)PM was not affected by age, education, duration, Hoehn-Yahr staging and side of onset in patients with Parkinson's disease.