Background
As a result of aging, older adults exhibit a decline in cognitive function. Several risk factors for cognitive impairment have been found, and aging is one of them. Furthermore, cognitive decline due to aging is progressive and irreversible, and it can hamper individuals’ performance of daily activities. Impaired ability to perform activities of daily living (ADL) and instrumental activities of daily living (IADL), which increases individuals’ dependence on others, affects psychological quality of life [
1]. Cognitive function comprises a wide range of dimensions, including attention, memory, calculation, orientation, working memory, language, visuospatial ability, problem-solving, executive function, and processing speed [
2]. The decline of cognitive functions and the development of dementia increase the probability of disability in older adults, resulting in an economic burden on the public health system [
3]. Therefore, a key issue is to identify how cognitive decline in older adults can be delayed and prevent a decline in their ADL ability and eye–hand coordination (EHC). Furthermore, effective interventions that might reduce or delay cognitive decline, or indeed lead to improvements in cognitive function and EHC, are critical for the older adults, especially those at higher risk of cognitive decline.
EHC involves the synergistic functioning of the perception and motor systems [
4,
5]. Aging results in physiological changes, and EHC is controlled by the frontal lobe of the cerebrum; cognitive decline affects motor planning and execution and causes problems such as decreased muscular endurance and poor coordination. Thus, cognitive decline greatly affects EHC [
6,
7]. As a result of aging, older adults experience a decline in physical activity and a gradual decrease in proprioceptive acuity; the optic nerve axon population also declines, leading to poor EHC [
8], which is associated with the symptoms of early stage of cognitive decline [
9,
10]. EHC is required for performing daily life activities such as bathing, dressing, exercising, and writing [
8]. Severe impairment of EHC affects ADL ability and is closely associated with cognitive decline and nervous system dysfunction. Impaired EHC leads to the decreased ability to perform ADL and social activities in the general population, whereas it may lead to loss of ability for independent living in older adults [
11]. Therefore, normal EHC is beneficial toward maintaining the quality of life of individuals. For normal EHC, smooth and natural coordination between the visual and motor systems are essential.
EHC can be divided into the sub-abilities of visual-motor integration (VMI), visual perception (VP), and motor coordination (MC) [
12]; these sub-abilities must be in a normal state to ensure smooth and natural EHC. VMI refers to the ability of the visual system to deliver information about the surrounding environment to the brain for organization, analysis, comparison, integration, and other processing. For example, the eyes see the shape of an object, and a pen is used to write it out; this transcribing action is a result of integration between VP and MC. The order of development for VP is pyramid-like and comprises the following dimensions (listed from bottom to top): visual attention, visual scanning, shape identification, visual memory, and visual cognition, which is the highest class. By means of visual input information being processed by perception, these link to cognition and life experiences. MC refers to smoothness, precision, and control during an action. Movement can be divided into coarse action and fine action. Coarse action refers to actions requiring coordination between parts of the body, whereas fine action comprises basic actions of the hand, such as drawing and writing [
13].
Interactive cognitive-motor training (ICMT) involves using a computer to simulate a real-world environment; in this training, users receive immediate visual feedback from a projector screen and can experience and interact with the images presented by the computer [
14]. Compared with traditional motor training, the advantages of ICMT are as follows: (1) it simultaneously promotes cognitive function: ICMT users are required to simultaneously process information, which enhances their selective attention required to execute tasks, their executive function required to plan or make screen response decisions, and their other promotional abilities required to perform various cognitive functions [
15]; (2) its cost and complexity are relatively low, and dropout rates are also lower [
16]; (3) it can assist the measurement (using tables), data analysis, and monitoring of the extent of improvement in participants; (4) individual training programs can be provided, and different training stages can be adjusted according to the individual [
15]; and (5) it enhances observational learning to provide visual, auditory, and kinesthetic feedback [
17].
Studies have indicated that the EHC of older adults can be enhanced through exercises or EHC training [
18,
19]. Past theories and empirical studies have further confirmed that interventional measures are effective strategies that improve the cognitive function of older adults [
20,
21]. Additionally, empirical studies have indicated that virtual reality training that combines cognition and physical activity is more effective than a training model with either cognition or physical activity [
22,
23]. However, studies have primarily focused on interventions in older adults with mild cognitive impairment or dementia, and few empirical studies on the EHC of individuals without cognitive impairment have been conducted. Therefore, this study examined the effects of ICMT on the VMI, VP, and MC sub-abilities of the EHC and cognitive function in older adults. The primary hypothesis of this study is that older adults who completed ICMT would show greater improvements on older adults’ VMI, VP, and MC sub-abilities of EHC when compared with an active control group. The secondary hypothesis of this study is that older adults who completed ICMT would show greater improvements on older adults’ cognitive function when compared with an active control group.
Discussion
The findings of this study indicated that 30-min ICMT sessions conducted three times a week for 8 weeks, with a total of 24 sessions, showed a small to large effect size and no significant decline for the VMI, VP, and MC of EHC. Compared with the active control group, the intervention could effectively promote the attention dimension of cognitive function.
EHC plays a crucial role in the successful performance of visual and spatial activities of daily living. According to the principle of motor learning, motor learning includes learning new skills or repeating the same skills, which can enhance visual abilities [
36,
37]. The study intervention involved repeating the same motor skill, which may have resulted in the enhancement of visual abilities in older adults, thus further improving their EHC. Additionally, the findings of this study showed that the 24 sessions of ICMT showed an improvement of the score for VMI, VP, and MC of EHC of the experimental group. These findings are consistent with those of previous studies, which have confirmed that poor EHC can be reversed through intervention [
18].
The study intervention improved the score of VMI and showed a small to moderate effect size of the experimental group. VMI is the integration of the perceptual and motor system. Previous studies of similar computerized interventions have shown no statistically significant effects on the VMI. Studies have also suggested that visual-motor integration training resulted in no statistically significant decline in the effectiveness on VMI between the two groups in this study [
38,
39].
The study intervention improved the score of VP and showed a small effect size in the experimental group. The interventions for VP can be divided into the major categories of developmental, neurophysiologic, or compensatory approaches. According to the theoretical definition, ICMT intervention in this study is a neurophysiologic approach. This type of intervention emphasizes the importance of postural stability to promote the oculomotor efficiency, visual-receptive, and visual-cognitive components in an individual [
40]. However, vision damage in older adults, such as presbyopia and cataract, is irreversible and causes a decreased ability to recognize items; thus, this may have resulted in changes in the VP scores of participants.
The study intervention showed moderate to large effect sizes and maintain the score for the MC of the experimental group. When an individual is performing an action, VP involves the use of visual information to confirm the position of each action. During the action, immediate visual or other sensory feedback must be relied on to perform follow-up actions [
11]. However, in this study, VP feedback was employed more, and other sensory feedback was employed less, which may have resulted in no statistically significant difference in MC between the two groups. Additionally, during the execution of ICMT, participants were unable to equally use all four limbs for the activity, and they mostly used their dominant hand for the activity, which may have also resulted in maintenance of MC but no statistical difference between the groups.
Although the intervention of the present study was effective for the experimental group, the statistically difference between the experimental and active control groups of VMI, VP and MC could not be obtained. This crucial possible cause may be that the active control group of this study used tablet computers to engage in the passive information activity, and previous studies have indicated the effectiveness of training on tablet computers for MC and VMI [
5]. This result is consistent with previous research, which have suggested that tablet computers training can significantly enhance visuospatial abilities, processing speed and memory ability for healthy older adults and patients with mild cognitive impairment [
41,
42].
The study intervention showed an immediate, significant, and small effect size for the attention dimension of cognitive function. Attention is the process by which an individual respond to visual or auditory stimuli in the environment, and previous studies have confirmed that computerized training can promote the selective attention of older adults (effect sizes ranged from 0.20 to 1.64) [
43,
44], which are consistent with the effect size of this study (Cohen’s
d = 0.30). Although the study intervention had no statistically significant changes on other sub-items of cognitive function, there was no decreasing trend. In addition, the differences between this study and previous studies may be because ICMT primarily consists of physical activity. The participants were all healthy older adults, their cognitive function was originally high. Thus, the intervention did not result in significant change on other sub-items of cognitive function.
Conclusions
This study verified that the 24 sessions of ICMT showed small to large effect sizes for the VMI, VP, and MC of EHC and could effectively promote the attention dimension of cognitive function. The advantage of this study is not only that interventional studies were conducted on the EHC of older adults, a topic less frequently discussed in past studies, but also that the VMI, VP, and MC of EHC were analyzed. In addition, because there was no decreasing trend, it may delay the decline of the overall cognitive function of older adults. However, there are few limitations of this study. First, it requires more long-term data, such as data from 1- or 2-year follow-up. Second, the vision damage (such as presbyopia and cataract) in the older adults may cause a decreased ability to recognize the target items of intervention. Finally, a majority of the subjects were female in this is study, which may limit generalizability. Future research should extend the range of participants to older adults with different degrees of cognitive function (such as individuals with mild cognitive impairment or dementia), increase the training session duration, use of a true control group and should conduct long-term follow-up. In clinical practice, because the interactivity of the study intervention was favorable and older adults showed a high participation rate, ICMT should be included in routine community activities to prevent the decline of EHC and cognitive function in older adults.