Consensus Paper: Cerebellum and Ageing.

Given the key roles of the cerebellum in motor, cognitive, and affective operations and given the decline of brain functions with aging, cerebellar circuitry is attracting the attention of the scientific community. The cerebellum plays a key role in timing aspects of both motor and cognitive operations, including for complex tasks such as spatial navigation. Anatomically, the cerebellum is connected with the basal ganglia via disynaptic loops, and it receives inputs from nearly every region in the cerebral cortex. The current leading hypothesis is that the cerebellum builds internal models and facilitates automatic behaviors through multiple interactions with the cerebral cortex, basal ganglia and spinal cord. The cerebellum undergoes structural and functional changes with aging, being involved in mobility frailty and related cognitive impairment as observed in the physio-cognitive decline syndrome (PCDS) affecting older, functionally-preserved adults who show slowness and/or weakness. Reductions in cerebellar volume accompany aging and are at least correlated with cognitive decline. There is a strongly negative correlation between cerebellar volume and age in cross-sectional studies, often mirrored by a reduced performance in motor tasks. Still, predictive motor timing scores remain stable over various age groups despite marked cerebellar atrophy. The cerebello-frontal network could play a significant role in processing speed and impaired cerebellar function due to aging might be compensated by increasing frontal activity to optimize processing speed in the elderly. For cognitive operations, decreased functional connectivity of the default mode network (DMN) is correlated with lower performances. Neuroimaging studies highlight that the cerebellum might be involved in the cognitive decline occurring in Alzheimer's disease (AD), independently of contributions of the cerebral cortex. Grey matter volume loss in AD is distinct from that seen in normal aging, occurring initially in cerebellar posterior lobe regions, and is associated with neuronal, synaptic and beta-amyloid neuropathology. Regarding depression, structural imaging studies have identified a relationship between depressive symptoms and cerebellar gray matter volume. In particular, major depressive disorder (MDD) and higher depressive symptom burden are associated with smaller gray matter volumes in the total cerebellum as well as the posterior cerebellum, vermis, and posterior Crus I. From the genetic/epigenetic standpoint, prominent DNA methylation changes in the cerebellum with aging are both in the form of hypo- and hyper-methylation, and the presumably increased/decreased expression of certain genes might impact on motor coordination. Training influences motor skills and lifelong practice might contribute to structural maintenance of the cerebellum in old age, reducing loss of grey matter volume and therefore contributing to the maintenance of cerebellar reserve. Non-invasive cerebellar stimulation techniques are increasingly being applied to enhance cerebellar functions related to motor, cognitive, and affective operations. They might enhance cerebellar reserve in the elderly. In conclusion, macroscopic and microscopic changes occur in the cerebellum during the lifespan, with changes in structural and functional connectivity with both the cerebral cortex and basal ganglia. With the aging of the population and the impact of aging on quality of life, the panel of experts considers that there is a huge need to clarify how the effects of aging on the cerebellar circuitry modify specific motor, cognitive, and affective operations both in normal subjects and in brain disorders such as AD or MDD, with the goal of preventing symptoms or improving the motor, cognitive, and affective symptoms.

Effects of a 10-week musical instrument training on cognitive function in healthy older adults: implications for desirable tests and period of training.

Introduction: Previous studies have shown that musical instrument training programs of 16 or more weeks improve verbal memory (Logical Memory Test delayed recall), processing speed (Digit Symbol Coding Test), and executive function (Trail Making Test Part B) of musically untrained healthy older adults. However, it is unclear whether shorter-period instrument training can yield similar effects. We sought to (1) verify those results and (2) clarify if intervention effects could be detected using other measures such as reaction time. Methods: Healthy older adults (mean age = 73.28 years) were pseudo-randomly assigned to an untrained control group (n = 30) or an intervention group (n = 30) that received a weekly 10-session musical instrument training program (using melodica). We conducted neuropsychological tests on which intervention effects or association with musical training were reported in previous studies. We newly included two reaction time tasks to assess verbal working memory (Sternberg task) and rhythm entrainment (timing task). Intervention effects were determined using a "group × time" analysis of variance (ANOVA). Results: The intervention effects were detected on the reaction time in Sternberg task and phonological verbal fluency. Although intervention effects had been reported on Logical Memory test, Digit Symbol Coding Test and Trail Making Test in previous studies with longer training periods, the present study did not show such effects. Instead, the test-retest practice effect, indicated by significant improvement in the control group, was significant on these tests. Discussion: The present results indicated the usefulness of working memory assessments (Verbal Fluency Test and Sternberg task) in detecting the effects of short-term melodica training in healthy older adults. The practice effect detected on those three tasks may be due to the shorter interval between pre- and post-intervention assessments and may have obscured intervention effects. Additionally, the findings suggested the requirement for an extended interval between pre- and post-tests to capture rigorous intervention effects, although this should be justified by a manipulation of training period.

Advanced aging effects on implicit motor imagery and its links to motor performance: An investigation via mental rotation of letters, hands, and feet.

This study focuses on changes in implicit motor imagery during advanced aging and these changes' co-occurrences with physical motor deficits. We administered a mental rotation (MR) task with letters, hands, and feet to 28 young adults (20-27 years) and to 71 older adults (60-87 years), and assessed motor skills (gait mobility and hand dexterity) and neuropsychological performance. Compared to young adults, older adults showed lower MR performance for all stimuli and stronger biomechanical constraint effects on both hand and foot rotation. Moreover, the foot biomechanical constraint effect continued to increase during late adulthood, and declines in hand and foot motor imagery emerged at earlier old ages than declines in visual imagery. These results first demonstrated distinct aging trajectories of hand motor imagery, foot motor imagery, and visual imagery. Exploratory partial correlation analysis for older adults showed positive associations of low-level perceptual-motor skills (Trail Making Test-A performance) with hand and foot MR performance and positive associations of mobility (Timed Up and Go test performance) with foot and letter MR performance. These associations exhibited somewhat different patterns from those of young adults and raised the possibility that age-related declines in motor (and visual) imagery co-occur with declines in motor functioning.

Relationship between preoperative anxiety and onset of delirium after cardiovascular surgery in elderly patients: focus on personality and coping process.

BACKGROUND: Postoperative delirium is associated with increased mortality. Therefore, it is important to manage delirium during the entire perioperative period. Preoperative anxiety is associated with poor prognosis in postoperative patients who have undergone cardiovascular surgery. This study aims to investigate the relationship between preoperative anxiety and onset of delirium after cardiovascular surgery in elderly patients (aged 65 years or older), considering the individual psychological characteristics, such as personality and stress coping skills in response to anxiety, as confounding factors. METHODS: This prospective study included patients aged >65 years in a preoperative state before undergoing cardiovascular surgery. Subjects were divided into two groups based on whether they experienced postoperative delirium, or not. We compared clinical and demographic factors, preoperative psychiatric and psychological factors, and intraoperative and perioperative physical factors between the control and delirium groups. Multiple imputations were used to account for missing data. RESULTS: Out of 168 subjects enrolled in this study, 26 (15.5%) developed postoperative delirium. Univariate analysis showed significant differences in age (P = 0.027), cognitive function (P = 0.007), agreeableness (P = 0.029), and the Acute Physiology and Chronic Health Evaluation-II (APACHE-II) score (P = 0.023) between the delirium and control groups. Multiple logistic regression analysis did not identify a significant association between preoperative anxiety and the onset of postoperative delirium. However, age (odds ratio (OR) = 1.114, P = 0.018), agreeableness (OR = 0.555, P = 0.008), and the APACHE-II score (OR = 1.227, P = 0.008) were identified as risk factors for postoperative delirium. CONCLUSION: Agreeableness, one of the personality traits associated with preoperative anxiety, appears to be involved in the development of postoperative delirium as an independent psychological factor, regardless of age or physical factors.

Parental responsiveness and children's trait epistemic curiosity.

Curiosity, the desire to learn new information, has a powerful effect on children's learning. Parental interactions facilitate curiosity-driven behaviors in young children, such as self-exploration and question-asking, at a certain time. Furthermore, parenting quality predicts better academic outcomes. However, it is still unknown whether persistent parenting quality is related to children's trait epistemic curiosity (EC). The current study examined whether parenting practices, responsiveness, and demandingness are cross-sectionally related to the trait EC of children in different age groups (preschoolers, younger and older school-aged children). We adopted a shortened Japanese version of the parenting style questionnaire and modified the trait EC questionnaire in young children. A sample of 244 caregivers (87.37% mothers) of children (ages 3-12) was recruited through educational institutions in Japan and reported on their parenting practices and trait EC. All data analyses were performed using SPSS version 26. Hierarchical regression analyses were performed to determine the explanatory variables for children's trait EC. Self-reported parental responsiveness significantly explained EC scores. To the best of our knowledge, this is the first study to show a cross-sectional relationship between parental responsiveness and children's trait EC. Future research should clarify whether parental responsiveness in early childhood predicts children's EC later in life.

Impact of Early-Commenced and Continued Sports Training on the Precuneus in Older Athletes.

Intervention studies on sedentary older adults have demonstrated that commencing physical exercise at an older age has a positive effect on brain structure. Although this suggests that older athletes with lifelong sports training have larger gray matter volume (GMV) in some brain regions compared to age-matched non-athletes, evidence in the literature is scarce. Moreover, it remains unclear whether a larger GMV is associated with training intensity or period of training in life. To address these gaps in the literature, we compared regional brain GMV between 24 older athletes (mean age, 71.4 years; age at the commencement of sports training, 31.2 years, continuous sports training, 40.0 years; current training time, 7.9 h/week) and 24 age-matched non-athletes (mean age, 71.0 years). The period of sports training and the current training time of the athletes were assessed. Both groups were evaluated for physical activity intensity as well as cognitive and motor performance. Although no group differences were noted in cognitive and motor performance, athletes reported higher physical activity intensity than non-athletes. Whole-brain structural analysis revealed a significantly larger GMV in several brain regions in athletes. Notably, the GMV of the precuneus in athletes was positively correlated with earlier commencement of sports training and training duration but was negatively correlated with current training time. Our findings demonstrate that early-commenced and continued sports training predicts structural maintenance of the precuneus in old age. Our results also suggest that excessive training time in old age may have a negative impact on the GMV of the precuneus; thereby delineating how the precuneus is associated with lifelong sports training in older athletes.

Selective attention to the mouth of a talker in Japanese-learning infants and toddlers: Its relationship with vocabulary and compensation for noise.

Infants increasingly gaze at the mouth of talking faces during the latter half of the first postnatal year. This study investigated mouth-looking behavior of 120 full-term infants and toddlers (6 months-3 years) and 12 young adults (21-24 years) from Japanese monolingual families. The purpose of the study included: (1) Is such an attentional shift to the mouth in infancy similarly observed in Japanese environment where contribution of visual speech is known to be relatively weak? (2) Can noisy conditions increase mouth-looking behavior of Japanese young children? (3) Is the mouth-looking behavior related to language acquisition? To this end, movies of a talker speaking short phrases were presented while manipulating signal-to-noise ratio (SNR: Clear, SN+4, and SN-4). Expressive vocabulary of toddlers was obtained through their parents. The results indicated that Japanese infants initially have a strong preference for the eyes to mouth which is weakened toward 10 months, but the shift was later and in a milder fashion compared to known results for English-learning infants. Even after 10 months, no clear-cut preference for the mouth was observed even in linguistically challenging situations with strong noise until 3 years of age. In the Clear condition, there was a return of the gaze to the eyes as early as 3 years of age, where they showed increasing attention to the mouth with increasing noise level. In addition, multiple regression analyses revealed a tendency that 2- and 3-year-olds with larger vocabulary increasingly look at the eyes. Overall, the gaze of Japanese-learning infants and toddlers was more biased to the eyes in various aspects compared to known results of English-learning infants. The present findings shed new light on our understanding of the development of selective attention to the mouth in non-western populations.

Prefrontal Plasticity after a 3-Month Exercise Intervention in Older Adults Relates to Enhanced Cognitive Performance.

This study examined exercise intervention effects on older adults' brain structures and function. Brain data were analyzed from 47 healthy adults between 61 and 82 years of age who, in a previous study, showed cognitive improvement following a 3-month intervention. The participants were assigned to a motor exercise intervention group (n = 24), performing exercise training programs for a 12-week period, or a waiting control group (n = 23), abstaining from any exercise program. Structural analysis of the frontal cortex and hippocampus revealed increased gray matter volume and/or thickness in several prefrontal areas in the intervention group and reduced hippocampal gray matter volume in the control group. Importantly, the volume increase in the middle frontal sulcus in the intervention group was associated with a general cognitive improvement after the intervention. Functional analysis showed that the prefrontal functional connectivity during a working memory task differently changed in response to the intervention or waiting in the two groups. The functional connectivity decreased in the intervention group, whereas the corresponding connectivity increased in the control group, which was associated with maintaining cognitive performance. The current longitudinal findings indicate that short-term exercise intervention can induce prefrontal plasticity associated with cognitive performance in older adults.

Musical instrument training program improves verbal memory and neural efficiency in novice older adults.

Previous studies indicate that musical instrument training may improve the cognitive function of older adults. However, little is known about the neural origins of training-related improvement in cognitive function. Here, we assessed the effects of instrumental training program on cognitive functions and neural efficiency in musically naïve older adults (61-85 years old). Participants were assigned to either the intervention group, which received a 4-month instrumental training program using keyboard harmonica, or a control group without any alternative training. Cognitive measurements and functional magnetic resonance imaging during visual working memory (VWM) task were administered before and after the intervention in both groups. Behavioral data revealed that the intervention group significantly improved memory performance on the test that measures verbal recall compared to the control group. Neuroimaging data revealed that brain activation in the right supplementary motor area, left precuneus, and bilateral posterior cingulate gyrus (PCgG) during the VWM task decreased after instrumental training only in the intervention group. Task-related functional connectivity (FC) analysis revealed that the intervention group showed decreased FC between the right PCgG and left middle temporal gyrus, and between the left putamen and right superior temporal gyrus (lPu-rSTG) during a VWM task after the intervention. Furthermore, a greater improvement in memory performance in the intervention group was associated with a larger reduction in lPu-rSTG FC, which might be interpreted as improved neural efficiency. Our results indicate that the musical instrument training program may contribute to improvements in verbal memory and neural efficiency in novice older adults.

Neural Advantages of Older Musicians Involve the Cerebellum: Implications for Healthy Aging Through Lifelong Musical Instrument Training.

This study compared 30 older musicians and 30 age-matched non-musicians to investigate the association between lifelong musical instrument training and age-related cognitive decline and brain atrophy (musicians: mean age 70.8 years, musical experience 52.7 years; non-musicians: mean age 71.4 years, no or less than 3 years of musical experience). Although previous research has demonstrated that young musicians have larger gray matter volume (GMV) in the auditory-motor cortices and cerebellum than non-musicians, little is known about older musicians. Music imagery in young musicians is also known to share a neural underpinning [the supramarginal gyrus (SMG) and cerebellum] with music performance. Thus, we hypothesized that older musicians would show superiority to non-musicians in some of the abovementioned brain regions. Behavioral performance, GMV, and brain activity, including functional connectivity (FC) during melodic working memory (MWM) tasks, were evaluated in both groups. Behaviorally, musicians exhibited a much higher tapping speed than non-musicians, and tapping speed was correlated with executive function in musicians. Structural analyses revealed larger GMVs in both sides of the cerebellum of musicians, and importantly, this was maintained until very old age. Task-related FC analyses revealed that musicians possessed greater cerebellar-hippocampal FC, which was correlated with tapping speed. Furthermore, musicians showed higher activation in the SMG during MWM tasks; this was correlated with earlier commencement of instrumental training. These results indicate advantages or heightened coupling in brain regions associated with music performance and imagery in musicians. We suggest that lifelong instrumental training highly predicts the structural maintenance of the cerebellum and related cognitive maintenance in old age.

Word scanning in native and non-native languages: insights into reading with declined accommodation.

This study investigated the effects of declined accommodation on reading performance in non-native and native languages. Eighteen native Japanese speakers participated: eight presbyopes and ten non-presbyopes. In the experiment, participants were asked to scan, or sequentially read six-word items presented in two-line texts, identify a non-word target as quickly as possible, and indicate its location. In addition to the participant type (presbyopes/non-presbyopes) and language of the reading material (Japanese/English), viewing distance (35 cm/70 cm) and contrast (18%/100%) were manipulated. The results showed that the presbyopes exhibited worse reading performance than the non-presbyopes at closer distances irrespective of the language. Notably, the inferiority of the presbyopes' reading performance was more pronounced when they read in a non-native language than in their native language. It should be noted that differences in reading performance between the presbyopes and non-presbyopes were subtle for high-contrast words at longer viewing distances, indicating that age- or cohort-related perceptual, motor, and cognitive differences were almost negligible, but accommodation mattered. These results suggest that the effect of accommodation decline is influenced by the language of the reading material.

Neural Correlates of Working Memory Maintenance in Advanced Aging: Evidence From fMRI.

Working memory (WM)-related brain activity is known to be modulated by aging; particularly, older adults demonstrate greater activity than young adults. However, it is still unclear whether the activity increase in older adults is also observed in advanced aging. The present functional magnetic resonance imaging (fMRI) study was designed to clarify the neural correlates of WM in advanced aging. Further, we set out to investigate in the case that adults of advanced age do show age-related increase in WM-related activity, what the functional significance of this over-recruitment might be. Two groups of older adults - "young-old" (61-70 years, n = 17) and "old-old" (77-82 years, n = 16) - were scanned while performing a visual WM task (the n-back task: 0-back and 1-back). WM effects (1-back > 0-back) common to both age groups were identified in several regions, including the bilateral dorsolateral prefrontal cortex (DLPFC), the inferior parietal cortex, and the insula. Greater WM effects in the old-old than in the young-old group were identified in the right caudal DLPFC. These results were replicated when we performed a separate analysis between two age groups with the same level of WM performance (the young-old vs. a "high-performing" subset of the old-old group). There were no regions where WM effects were greater in the young-old group than in the old-old group. Importantly, the magnitude of the over-recruitment WM effects positively correlated with WM performance in the old-old group, but not in the young-old group. The present findings suggest that cortical over-recruitment occurs in advanced old age, and that increased activity may serve a compensatory function in mediating WM performance.

Face-specific memory deficits and changes in eye scanning patterns among patients with amnestic mild cognitive impairment.

Amnestic mild cognitive impairment (aMCI) is a prodromal stage of Alzheimer's disease (AD). Previous studies have shown functional and structural degradation of the fusiform face area, which is a core region for face processing, in addition to medial temporal lobe degradation. We predicted that patients with aMCI exhibit a loss of face processing and/or face memory, accompanied by abnormal eye scanning patterns, since patients who have deficits in face perception (i.e. prosopagnosia) exhibit such tendencies. Eighteen patients with aMCI and age-matched healthy controls were tested for perception and short-term memory of visually presented faces and houses while their gaze was recorded. Patients with aMCI showed a decline in memory, compared with control observers, for faces, but not for houses. Patients looked more at the mouth of faces, compared with control observers. We demonstrate here the loss of short-term face memory in aMCI with abnormal scanning patterns that might reflect the cerebral abnormality found in patients with aMCI.

Visuotactile interaction even in far sagittal space in older adults with decreased gait and balance functions.

Spatial proximity of signals from different sensory modalities is known to be a crucial factor in facilitating efficient multisensory processing in young adults. However, recent studies have demonstrated that older adults exhibit strong visuotactile interactions even when the visual stimuli were presented in a spatially disparate position from a tactile stimulus. This suggests that visuotactile peripersonal space differs between older and younger adults. In the present study, we investigated to what extent peripersonal space expands in the sagittal direction and whether this expansion was linked to the decline in sensorimotor functions in older adults. Vibrotactile stimuli were delivered either to the left or right index finger, while visual stimuli were presented at a distance of 5 cm (near), 37.5 cm (middle), or 70 cm (far) from each finger. The participants had to respond rapidly to a randomized sequence of unimodal (visual or tactile) and simultaneous visuotactile targets (i.e., a redundant target paradigm). Sensorimotor functions were independently assessed by the Timed Up and Go (TUG) and postural stability tests. Results showed that reaction times to the visuotactile bimodal stimuli were significantly faster than those to the unimodal stimuli, irrespective of age group [younger adults: 22.0 ± 0.6 years, older adults: 75.0 ± 3.3 years (mean ± SD)] and target distance. Of importance, a race model analysis revealed that the co-activation model (i.e., visuotactile multisensory integrative process) is supported in the far condition especially for older adults with relatively poor performance on the TUG or postural stability tests. These results suggest that aging can change visuotactile peripersonal space and that it may be closely linked to declines in sensorimotor functions related to gait and balance in older adults.

Improved Digit Span in Children after a 6-Week Intervention of Playing a Musical Instrument: An Exploratory Randomized Controlled Trial.

Previous studies have reported that music training not only improves children's musical skills, but also enhances their cognitive functions. However, there is a disagreement about what domain(s) might be affected. Moreover, effects of short-term (

Language/Culture Modulates Brain and Gaze Processes in Audiovisual Speech Perception.

Several behavioural studies have shown that the interplay between voice and face information in audiovisual speech perception is not universal. Native English speakers (ESs) are influenced by visual mouth movement to a greater degree than native Japanese speakers (JSs) when listening to speech. However, the biological basis of these group differences is unknown. Here, we demonstrate the time-varying processes of group differences in terms of event-related brain potentials (ERP) and eye gaze for audiovisual and audio-only speech perception. On a behavioural level, while congruent mouth movement shortened the ESs' response time for speech perception, the opposite effect was observed in JSs. Eye-tracking data revealed a gaze bias to the mouth for the ESs but not the JSs, especially before the audio onset. Additionally, the ERP P2 amplitude indicated that ESs processed multisensory speech more efficiently than auditory-only speech; however, the JSs exhibited the opposite pattern. Taken together, the ESs' early visual attention to the mouth was likely to promote phonetic anticipation, which was not the case for the JSs. These results clearly indicate the impact of language and/or culture on multisensory speech processing, suggesting that linguistic/cultural experiences lead to the development of unique neural systems for audiovisual speech perception.

Impact of language on functional connectivity for audiovisual speech integration.

Visual information about lip and facial movements plays a role in audiovisual (AV) speech perception. Although this has been widely confirmed, previous behavioural studies have shown interlanguage differences, that is, native Japanese speakers do not integrate auditory and visual speech as closely as native English speakers. To elucidate the neural basis of such interlanguage differences, 22 native English speakers and 24 native Japanese speakers were examined in behavioural or functional Magnetic Resonance Imaging (fMRI) experiments while mono-syllabic speech was presented under AV, auditory-only, or visual-only conditions for speech identification. Behavioural results indicated that the English speakers identified visual speech more quickly than the Japanese speakers, and that the temporal facilitation effect of congruent visual speech was significant in the English speakers but not in the Japanese speakers. Using fMRI data, we examined the functional connectivity among brain regions important for auditory-visual interplay. The results indicated that the English speakers had significantly stronger connectivity between the visual motion area MT and the Heschl's gyrus compared with the Japanese speakers, which may subserve lower-level visual influences on speech perception in English speakers in a multisensory environment. These results suggested that linguistic experience strongly affects neural connectivity involved in AV speech integration.

The neural mechanism of biomechanical constraints in the hand laterality judgment task: A near-infrared spectroscopy study.

The mental rotation (MR) task is defined as a discrimination task between mirror-reversed images involving discrepancy in angular orientation. Various studies have shown that the MR task likely causes mental imagery, that is, visual and/or motor imagery, depending on stimulus types. When figures of rotated hands are presented to be identified as a left or right hand, reaction times (RTs) usually show an effect of biomechanical constraints (BC): a hand in a position difficult to reach with a real movement results in longer RTs. The BC effect as a marker of motor imagery has been investigated by brain function measures (fMRI, PET, EEG and MEG) as well as by RTs. Unlike other neuroimaging techniques, NIRS (near-infrared spectroscopy) imposes few physical constraints on participants and is relatively unaffected by motion artifact, which permits serial assessments of tasks in relaxed and natural environment. Focusing on these advantages, a NIRS study on motor imagery in HLJ was carried out in which we measured the brain activation during the HLJ task and a single character judgment task. In the HLJ task, both the RTs and the activity of the left superior parietal lobe (SPL) showed an interaction between Hand (left, right) and Orientation (135°, 225°) i.e., the BC effect, but not in the character judgment task. More specifically, in the analysis of BC-related activity of SPL, although the Hand×Orientation interaction was significant, the left SPL for the left hand significantly increased from 135° to 225°, but the reversed increase (from 225° to 135°) was not found for the right hand. These results suggest that left SPL is involved in the BC effect and NIRS differentiates left hand awkwardness of right-hander in the HLJ task.

Effects of Word Width and Word Length on Optimal Character Size for Reading of Horizontally Scrolling Japanese Words.

The present study investigated, whether word width and length affect the optimal character size for reading of horizontally scrolling Japanese words, using reading speed as a measure. In Experiment 1, three Japanese words, each consisting of four Hiragana characters, sequentially scrolled on a display screen from right to left. Participants, all Japanese native speakers, were instructed to read the words aloud as accurately as possible, irrespective of their order within the sequence. To quantitatively measure their reading performance, we used rapid serial visual presentation paradigm, where the scrolling rate was increased until the participants began to make mistakes. Thus, the highest scrolling rate at which the participants' performance exceeded 88.9% correct rate was calculated for each character size (0.3°, 0.6°, 1.0°, and 3.0°) and scroll window size (5 or 10 character spaces). Results showed that the reading performance was highest in the range of 0.6° to 1.0°, irrespective of the scroll window size. Experiment 2 investigated whether the optimal character size observed in Experiment 1 was applicable for any word width and word length (i.e., the number of characters in a word). Results showed that reading speeds were slower for longer than shorter words and the word width of 3.6° was optimal among the word lengths tested (three, four, and six character words). Considering that character size varied depending on word width and word length in the present study, this means that the optimal character size can be changed by word width and word length in scrolling Japanese words.

Brain activation during visual working memory correlates with behavioral mobility performance in older adults.

Functional mobility and cognitive function often decline with age. We previously found that functional mobility as measured by the Timed Up and Go Test (TUG) was associated with cognitive performance for visually-encoded (i.e., for location and face) working memory (WM) in older adults. This suggests a common neural basis between TUG and visual WM. To elucidate this relationship further, the present study aimed to examine the neural basis for the WM-mobility association. In accordance with the well-known neural compensation model in aging, we hypothesized that "attentional" brain activation for easy WM would increase in participants with lower mobility. The data from 32 healthy older adults were analyzed, including brain activation during easy WM tasks via functional Magnetic Resonance Imaging (fMRI) and mobility performance via both TUG and a simple walking test. WM performance was significantly correlated with TUG but not with simple walking. Some prefrontal brain activations during WM were negatively correlated with TUG performance, while positive correlations were found in subcortical structures including the thalamus, putamen and cerebellum. Moreover, activation of the subcortical regions was significantly correlated with WM performance, with less activation for lower WM performers. These results indicate that older adults with lower mobility used more cortical (frontal) and fewer subcortical resources for easy WM tasks. To date, the frontal compensation has been proposed separately in the motor and cognitive domains, which have been assumed to compensate for dysfunction of the other brain areas; however, such dysfunction was less clear in previous studies. The present study observed such dysfunction as degraded activation associated with lower performance, which was found in the subcortical regions. We conclude that a common dysfunction-compensation activation pattern is likely the neural basis for the association between visual WM and functional mobility.