Word Context Diversity And Recognition Memory: Evidence From Patients With Alzheimer's Disease

At present, Dementia of the Alzheimer type is one of the major disease threat to the health of the elderly .Because dementia of the Alzheimer type is a progressive development of lethal neurodegenerative diseases, the clinical manifestations: the deterioration of cognitive and memory function, the progressive decline of daily living ability,and accompanied by a variety of neuropsychiatric symptoms and behavior disorder. Nowadays, There is still no radical cure method for Alzheimer's type of dementia, mostly through taking drugs to control the decline of the brain function, so, It's a very important thing to delay dementia symptoms from different aspects of the cognitive to investigate the mechanism of disease.Lexical processing is a basic cognitive ability of mankind. The existing theoretical model holds that lexical cognition is influenced by a variety of variables,where word frequency is a very important driving variable. Interestingly, in the lexical recognition task,normal and dementia of the Alzheimer type patients showed a reversal model of the word frequency effect. However, the latest research has found that, In the process of human visual lexical processing, the contextual diversity rather than the word frequency determines the time of word naming and processing. Under the condition of controlling the contextual diversity, the word frequency effect disappears. But under the condition of controlling the word frequency effect, the effect of the contextual diversity still exist. If contextual diversity can replace the word frequency affects people's normal lexical processing and recognition, then,whether there is a contextual diversity effect in the visual lexical recognition of the dementia of the Alzheimer type patients? If so, what effect pattern does the effect have? But the domestic and foreign researchers have not yet studied the above problems basic on the systematic experimental science......In view of this, the researchers make full use of the Chinese words and characters corpus characteristics, based on the recognition task to design of two behavioral experiments were provided to investigate cognitive mechanisms of the words or characters contextual diversity in language processing in dementia of the Alzheimer type patients. In experiment 1, the researchers screened 40 normal elderly people(NC), while through the Nanjing Military Region, Nanjing General Hospital to screening out the 40 mild dementia of the Alzheimer type(DAT) elderly people based on the clinical diagnosis of doctors. The experiment requires subjects to study 20 high-frequency low-contextual diversity words, 20 low-frequency low-contextual diversity words, 20 high-frequency high-contextual diversity words, then trying to judge the 60 target words and 60 interference words line. In experiment 2,to examining the characters' contextual diversity, the specific experimental operation as same as experiment one. Two experiments were stimulated by E-Prime program, and the subjects were recorded by key reaction. Then, the hit rate, false rate, discriminant index d',likelihood ratio ? and other data were analyzed.The experiment 1 found that: (1) regardless of the NC or DAT, Under the condition of control word contextual diversity(CD), the word frequency (WF) effect disappears; but under the condition of controlling the WF, the CD still exists; (2) the DAT compared with NC on the hit rate, WF show a slight reversal tendency, and CD appear an obvious reversal tendency; but on the false alarm rate, both of the WF and CD show a same rising tendency; (3) Compared with the NC on the discriminant index d', WF show the reversal trend, but CD show the same trend;and on the likelihood ratio ?,both of the WF and CD show the reversal tendency.The experiment 2 found that: (1) regardless of the NC or DAT, Under the condition of control character contextual diversity (CD), the character frequency effect (CF) disappears; but under the condition of controlling the CF effect, the CD still exists; (2) DAT compared with the NCon the hit rate, CF show a slight reversal tendency, and CD appear an obvious reversal tendency; but on the false alarm rate,both of the CF and CD show a same rising tendency; (3) Compared with the NC, the discriminant index d ' show the reversal tendency of CF and CD, but only CF showthe reversal tendency on the likelihood ratio ?.In summary, the experimental results of experiment 1 and 2 show that regardless of the DAT or NC, under the condition of controlling the CD ,WF or CF effect disappears, but under the condition of controlled WF or CF, the CD effect still exists.Also, compared with the NC,the DAT show a slight reversal tendency of WF and CF,but show an obvious reversal tendency of CD.