Dependence on Visual Feedback During Motor Skill Learning in Alzheimer's Disease

Three experiments examined the role of visual feedback on the performance of a fine motor task, namely the rotary pursuit, in patients with Alzheimer's disease (AD) and healthy older adults. After extensive practice tracking a fully visible target, participants in Experiments 1 and 2 were tested under restricted vision (RV) conditions. In both experiments, the two groups showed a drop in performance when vision was restricted, with AD patients showing a significantly larger decline. Tracking improved significantly in normal controls, but not AD patients across the RV trials after the initial drop. When difficulty of the rotary pursuit task was manipulated in Experiment 3 without restricting vision, AD patients and normal controls showed identical patterns of performance. Consequently, it could be concluded that AD patients in the first two experiments were relying more heavily on visual information for accurate performance of the tracking task than their healthy peers.     

One size does not fit all: face emotion processing impairments in semantic dementia, behavioural-variant frontotemporal dementia and Alzheimer's disease are mediated by distinct cognitive deficits

Patients with frontotemporal dementia (both behavioural variant [bvFTD] and semantic dementia [SD]) as well as those with Alzheimer's disease (AD) show deficits on tests of face emotion processing, yet the mechanisms underlying these deficits have rarely been explored. We compared groups of patients with bvFTD (n = 17), SD (n = 12) or AD (n = 20) to an age- and education-matched group of healthy control subjects (n = 36) on three face emotion processing tasks (Ekman 60, Emotion Matching and Emotion Selection) and found that all three patient groups were similarly impaired. Analyses of covariance employed to partial out the influences of language and perceptual impairments, which frequently co-occur in these patients, provided evidence of different underlying cognitive mechanisms. These analyses revealed that language impairments explained the original poor scores obtained by the SD patients on the Ekman 60 and Emotion Selection tasks, which involve verbal labels. Perceptual deficits contributed to Emotion Matching performance in the bvFTD and AD patients. Importantly, all groups remained impaired on one task or more following these analyses, denoting a primary emotion processing disturbance in these dementia syndromes. These findings highlight the multifactorial nature of emotion processing deficits in patients with dementia.     

Age-related changes of arm movements in dual task condition when walking on different surfaces

The purpose of this study was to investigate whether the dual task paradigm would influence arm movements during walking. Furthermore, we examined the effects of different walking surfaces on arm movements while performing dual tasks. The effects of age and gender were also investigated. Fifteen young adults and 15 older adults were included in this study. Subjects were asked to perform the walking task alone (single-task trial) and walking in combination with a cognitive task (dual-task trial). Four walking conditions (1 single task and 3 dual task trials)×two walking surfaces were encountered. Both age groups had greater elbow and trunk movement in the sagittal plane under the dual task trials as compared to the single task trial (p<.05). Subjects had greater upper extremity and upper body movement on the soft floor than on the hard floor (p<.05). Subjects had greater movement amplitude when confronting a challenging environment, especially in the contralateral side. Among gender, there was a group-gender interaction: the older females had smaller upper extremity movement than the older males (p<.05) but the opposite was true for the young adults. The results suggest that different age groups of males and females use different balance control strategy to deal with the challenging conditions.     

Two mutations preventing PDZ-protein interactions of GluR1 have opposite effects on synaptic plasticity

The regulated trafficking of GluR1 contributes significantly to synaptic plasticity, but studies addressing the function of the GluR1 C-terminal PDZ-ligand domain in this process have produced conflicting results. Here, we resolve this conflict by showing that apparently similar C-terminal mutations of the GluR1 PDZ-ligand domain result in opposite physiological phenotypes during activity- and CamKII-induced synaptic plasticity.