Clustering and Switching Patterns in Semantic Fluency and Their Relationship to Working Memory in Mild Cognitive Impairment

BACKGROUND AND PURPOSE: Semantic verbal fluency test is a neuropsychological assessment that can sensitively detect neuropathological changes. Considering its multifactorial features tapping various cognitive domains such as semantic memory, executive function, and working memory, it is necessary to examine verbal fluency performance in association with underlying cognitive functions. The objective of the current study was to investigate semantic fluency patterns of people with mild cognitive impairment (MCI) based on clustering and switching and their relationship with working memory. METHODS: Twenty-six individuals with MCI and 23 normal elderly adults participated in this study. A semantic verbal fluency test (animal version) was administered and the performance was analyzed using the following measures: number of correct words, cluster size, and number of switches. Scores of digit forward (DF) and backward span tasks were employed as working memory measures. RESULTS: Analyses of variance revealed significant group differences in the numbers of correct words and switches. Multivariate logistic regression and receiver-operating characteristic analyses showed that the number of switches more sensitively distinguished MCI existence than the number of correct words. Stepwise linear regression analysis showed that DF task and age significantly predicted the number of correct words while only the DF task significantly predicted the number of switches. CONCLUSIONS: Decrement in semantic verbal fluency in MCI seems to be associated with impaired switching abilities. Working memory capacity might serve as the underlying cognitive factor related to decreased verbal fluency in MCI.

Noun-Verb Dissociation in a Confrontation Naming Task for Persons with Mild Cognitive Impairment

BACKGROUND: The concept of Mild Cognitive Impairment (MCI) refers to a transitional period between normal aging and clinically demented state such as Alzheimer's disease. Detection of individuals with MCI is critical for prognosis of the disease progression and treatment of patients at risk. The current study manipulated linguistic complexity in naming nouns and verbs to examine whether the linguistically different entities contribute to differentiating individuals with MCI from normal elderly adults. Specific aims of the study are 1) to investigate the noun-verb dissociation in naming between the MCI and normal control groups and 2) to examine the differential effects between the groups depending on the linguistic subtypes of nouns (animate vs. inanimate) and verbs (the argument structure). METHODS: Twenty normal elderly individuals and 19 individuals with MCI participated in this study. A confrontation naming task was employed. Nouns were divided into the two subtypes (animate vs. inanimate), and verbs were classified into the three subtypes depending on the number of argument (1-place, 2-place, and 3-place). RESULTS: Results revealed that there were significant differences between the groups, indicating that individuals with MCI showed worse performance on naming in general than the control group. Furthermore, the MCI group presented differentially impaired performance on verbs than nouns compared to the control group. CONCLUSIONS: The results from the current study suggested that performance on a verb confrontation naming task could serve as a sensitive index to differentiate the MCI group from normal aging group.

Effects of Subthalamic Nucleus Deep Brain Stimulation on the Phonation and Articulation of the Patients with Parkinson's Disease

BACKGROUND: The purpose of this study was to investigate the effects of the subthalamic nucleus (STN) deep brain stimulation (DBS) on the phonation and articulation of patients with Parkinson's disease (PD). METHODS: Seven PD patients who underwent bilateral STN DBS were included. The patients were asked to make and sustain the vowel sounds /a/ and /i/ as long as possible and to repeat nonsense syllables, /pa/, /ta/, /ka/ and /pataka/ as quickly as possible for 3 seconds. When the patients were administered levodopa `on' and `off' treatments, we evaluated the effect of DBS on the maximum phonation time (MPT), jitter (pitch perturbation), shimmer (intensity perturbation), tremor index and diadochokinetic rate (DDK). In each condition, using a Unified Parkinson's Disease Rating Scale score, we also measured the motor disability of the patients. RESULTS: During levodopa `off', both the DBS and levodopa treatment caused significant prolongation of the MPT of the vowels /a/ and /i/. Acoustic analysis showed that DBS had an effect on shimmer only when the patients were levodopa `off'. At the articulatory level, no significant changes were found in the diadochokinetic rate under any conditions. However, there was a correlation between the amount of improvement of voice tremor and sum of UPDRS scores measuring `tremor at rest' and `postural tremor'. CONCLUSIONS: In patients with advanced PD, STN DBS improves phonation, but had limited effects on articulation.