Sachiko Kiyama

Distant functional connectivity for bimanual finger coordination declines with aging: an fMRI and SEM exploration

Although bimanual finger coordination is known to decline with aging, it still remains unclear how exactly the neural substrates underlying the coordination differ between young and elderly adults. The present study focused on: (1) characterization of the functional connectivity within the motor association cortex which is required for successful bimanual finger coordination, and (2) to elucidate upon its age-related decline. To address these objectives, we utilized functional magnetic resonance imaging (fMRI) in combination with structural equation modeling (SEM). This allowed us to compare functional connectivity models between young and elderly age groups during a visually guided bimanual finger movement task using both stable in-phase and complex anti-phase modes. Our SEM exploration of functional connectivity revealed significant age-related differences in connections surrounding the PMd in the dominant hemisphere. In the young group who generally displayed accurate behavior, the SEM model for the anti-phase mode exhibited significant connections from the dominant PMd to the non-dominant SPL, and from the dominant PMd to the dominant S1. However, the model for the elderly groups anti-phase mode in which task performance dropped, did not exhibit significant connections within the aforementioned regions. These results suggest that: (1) the dominant PMd acts as an intermediary to invoke intense intra- and inter-hemispheric connectivity with distant regions among the higher motor areas including the dominant S1 and the non-dominant SPL in order to achieve successful bimanual finger coordination, and (2) the distant connectivity among the higher motor areas declines with aging, whereas the local connectivity within the bilateral M1 is enhanced for the complex anti-phase mode. The latter may underlie the elderlys decreased performance in the complex anti-phase mode of the bimanual finger movement task.

Use of the sit-to-stand task to evaluate motor function of older adults using telemetry

BackgroundPhysical exercises are widely used in community programs, but not all older adults are willing to participate. Information and communication technology may solve this problem by allowing older people to participate in fitness programs at home. Use of remote instruction will facilitate physical exercise classes without requiring that participants gather at one place. The aim of this study was to examine use of a sit-to-stand task in evaluating motor function using conventional video communication in a telemetry system to enable real-time monitoring, and evaluation in physical performance of older adults at home.MethodsThe participants were 59 older individuals and 81 university students. Three physical exercise batteries were used: arm curl, figure-of-eight walk test, and functional reach. The knee extension maximum angular velocity (KEMAV) and the iliac elevation maximum velocity (IEMV) during standing up from a chair and the heel rise frequency were used in the motion-capture measurements. The results were assessed using multi-group structural equation modeling (SEM) for the young and older groups.ResultsYoung participants consistently performed better than their older counterparts on all items. Analyses with multi-group SEM based on correlations between items yielded a good model-fit for the data. Among all path diagrams for IEMV and KEMAV in the older and young groups, paths from muscular strength to skillfulness showed significant effects. The path from the IEMV to muscular strength was also significant in the older group.ConclusionsMulti-group SEM suggested that video-based measurements of IEMV during sit-to-stand motion can estimate muscular strength, which suggests that remote monitoring of physical performance can support wellness of community-dwelling older adults.

The multiple pronunciations of Japanese kanji: A masked priming investigation

English words with an inconsistent grapheme-to-phoneme conversion or with more than one pronunciation (“homographic heterophones”; e.g., “lead”–/l∊d/, /lid/) are read aloud more slowly than matched controls, presumably due to competition processes. In Japanese kanji, the majority of the characters have multiple readings for the same orthographic unit: the native Japanese reading (KUN) and the derived Chinese reading (ON). This leads to the question of whether reading these characters also shows processing costs. Studies examining this issue have provided mixed evidence. The current study addressed the question of whether processing of these kanji characters leads to the simultaneous activation of their KUN and ON reading, This was measured in a direct way in a masked priming paradigm. In addition, we assessed whether the relative frequencies of the KUN and ON pronunciations (“dominance ratio”, measured in compound words) affect the amount of priming. The results of two experiments showed that: (a) a single kanji, presented as a masked prime, facilitates the reading of the (katakana transcriptions of) their KUN and ON pronunciations; however, (b) this was most consistently found when the dominance ratio was around 50% (no strong dominance towards either pronunciation) and when the dominance was towards the ON reading (high-ON group). When the dominance was towards the KUN reading (high-KUN group), no significant priming for the ON reading was observed. Implications for models of kanji processing are discussed.

Is pitch accent necessary for comprehension by native Japanese speakers? - An ERP investigation

Not unlike the tonal system in Chinese, Japanese habitually attaches pitch accents to the production of words. However, in contrast to Chinese, few homophonic word-pairs are really distinguished by pitch accents (Shibata & Shibata, 1990). This predicts that pitch accent plays a small role in lexical selection for Japanese language comprehension. The present study investigated whether native Japanese speakers necessarily use pitch accent in the processing of accent-contrasted homophonic pairs (e.g., ame [LH] for ‘candy’ and ame [HL] for ‘rain’) measuring electroencephalographic (EEG) potentials. Electrophysiological evidence (i.e., N400) was obtained when a word was semantically incorrect for a given context but not for incorrectly accented homophones. This suggests that pitch accent indeed plays a minor role when understanding Japanese.

Investigation of age-related changes in brain activity during the divalent task-switching paradigm using functional MRI

This study compared the brain activation of young and older subjects during the use of the task-switching paradigm (TSP) at various task speeds to examine the relationship between task load and brain activation. Specifically, it attempted to examine whether the task load-dependent BOLD response gradient is a useful tool for functional magnetic resonance imaging-based assessments of age-related changes in cognitive function. We predicted that the extent of the activation of the brain regions responsible for task-set reconfiguration and the inhibition of task switching functions induced during the performance of a TSP-based task would vary according to age. Task difficulty was controlled by altering the inter-stimulus interval. Although similar brain regions were activated in both age groups, significant differences in the extent of the activation were detected between the young and older groups. In particular, some regions were activated in the older group, but not the young group. This study indicated that TSP-based task performance-induced activation of the brain regions linked to executive function increases with age and that the degree and pattern of such activation depend on the content and difficulty of the task being performed. This indicates that the age- and task difficulty-dependent augmentation of brain activation varies between brain regions.

Involvement of the Ventrolateral Prefrontal Cortex in Learning Others' Bad Reputations and Indelible Distrust.

A bad reputation can persistently affect judgments of an individual even when it turns out to be invalid and ought to be disregarded. Such indelible distrust may reflect that the negative evaluation elicited by a bad reputation transfers to a person. Consequently, the person him/herself may come to activate this negative evaluation irrespective of the accuracy of the reputation. If this theoretical model is correct, an evaluation-related brain region will be activated when witnessing a person whose bad reputation one has learned about, regardless of whether the reputation is deemed valid or not. Here, we tested this neural hypothesis with functional magnetic resonance imaging (fMRI). Participants memorized faces paired with either a good or a bad reputation. Next, they viewed the faces alone and inferred whether each person was likely to cooperate, first while retrieving the reputations, and then while trying to disregard them as false. A region of the left ventrolateral prefrontal cortex (vlPFC), which may be involved in negative evaluation, was activated by faces previously paired with bad reputations, irrespective of whether participants attempted to retrieve or disregard these reputations. Furthermore, participants showing greater activity of the left ventrolateral prefrontal region in response to the faces with bad reputations were more likely to infer that these individuals would not cooperate. Thus, once associated with a bad reputation, a person may elicit evaluation-related brain responses on their own, thereby evoking distrust independently of their reputation.