Biology subjects

Ideriha, T.

Publications and source records attributed to Ideriha, T..

5 recordsLinked to original sources

bioRxiv2026

Use of anodal transcranial direct current stimulation for improving motor performance in healthy adults: A systematic review and meta-analysis

PurposeTranscranial direct current stimulation (tDCS) can noninvasively modulate activity in targeted brain regions. It is well established that the excitability of motor-related regions can increase when the target region is located beneath the anode (anodal tDCS), suggesting its potential to increase motor performance. Although such attempts have been widely examined, the results remain inconclusive. The purpose of this study was to assess the conditions under which anodal tDCS may improve motor performance in healthy adults. MethodsWe conducted a systematic review of studies on the use of anodal tDCS for improving motor performance in healthy adults. A computerized search was performed using the Web of Science, Scopus, PubMed, JDreamIII, and Ichushi-Web to identify relevant studies published between January 1, 1990 and May 25, 2022. ResultsTwenty-five studies were included in the qualitative synthesis. For the meta-analysis, 25 trials (N=885) were extracted from 23 studies. There were significant effects of anodal tDCS on motor performance improvement, but with evidence of publication bias and substantial heterogeneity among the trials. Post-hoc analysis revealed that motor performance 24 hours after the application of anodal tDCS may benefit from stimulation. There was no marked effect related to stimulation intensity, duration, or whether stimulation was provided during motor performance. ConclusionsOur study clarified the current state of anodal tDCS use for motor performance enhancement and indicates that there is currently no reliable evidence to support its effectiveness. Further studies, particularly randomized controlled trials, are necessary to establish the reliability of these effects for future applications.

neuroscience↗

bioRxiv2024

Switching on Behavioral and Neural Rhythmicity to Retrieve Memories When the Number of Retained Items Exceeds Four

Even when we experience difficulty in recalling memories, we nevertheless manage to retrieve the target items. However, the neural mechanisms that enable such difficult memory retrieval are unknown. Here, we report an intriguing phenomenon where our nervous system "switches on" behavioral/neural rhythmicity to retrieve memory when the number of candidate items exceeds four. In our experiments, participants learned and retrieved 2-5 color/letter pairs. Analyses of hundreds of reaction times revealed a significant tendency for memory recall to occur at discrete times corresponding to theta-alpha (4-13 Hz) cycles, but only when the number of memorized pairs exceeded four. Electrophysiological data localized theta-alpha rhythmicity around parietal electrodes, a region associated with the long-term memory system. Our findings suggest that neural rhythmicity facilitates memory retrieval when the number of candidate items exceeds four, which is known as the "magical number" corresponding to the limit of human cognitive capacity.

neuroscience↗

bioRxiv2024

The flow state is not accompanied by frontal-midline theta activity: An EEG investigation of more than 700 video gameplay sessions

People sometimes experience a "flow state"--characterized by hyperfocus, time distortion, and loss of self-awareness--during sports or video gameplay. Previous neuropsychological studies using simple laboratory tasks have reported that the flow state is associated with activation in the frontal lobe, reflected in theta (4-7 Hz) band rhythmic neural activity in medial prefrontal regions (frontal-midline theta [FMT] activity). However, the findings of previous studies might be problematic because they did not appropriately capture the neural activity associated with the flow state for the following reasons: 1) they used unfamiliar and unmotivating tasks; 2) they defined the neural basis of the flow state as neural activity occurring during tasks of optimal difficulty, disregarding trial-to-trial variations in subjective experience of the flow state; 3) the duration of the experiment or the number of trials was not sufficient to capture the rare experience of flow; or 4) they ignored individual differences in neural activities related to flow experiences. Thus, we examined the relationship between the flow state and FMT activity, recorded via scalp electroencephalography, in an experimental paradigm that addressed these four issues. First, participants played their favorite competitive video games, which they had been routinely playing. Second, task difficulty was kept as uniform as possible across trials by employing rank matching to directly examine the correlation between subjective flow level and FMT activity across trials. Third, to address the concern regarding the low frequency of the flow experience, more than 100 trials were completed over 10 days by each participant. Lastly, we adopted a within-participant statistical approach to examine individual differences in the nature of the flow experience. The results showed no correlation between FMT activity and the degree of subjective flow in six out of seven participants, contrary to previous reports. Our results challenge the conventional view that frontal lobe activity, as reflected in FMT activity, is instrumental in entering into the flow state.

neuroscience↗

bioRxiv2022

Overflow of Working Memory from an Easily Accessible Active State

Working memory is a system that realizes short-term memory retention and is essential to everyday activities. Recently, it has been suggested that working memory items can be maintained in both an active state with sustained neural activity and a latent state without any explicit neural activity. However, how easily we can retrieve memories in each state and how much information can be retained in the active state remains unknown. Here, we addressed these questions by adopting a novel experimental paradigm for measuring the reaction time required to recall a letter of the alphabet when presented with a corresponding color, based on memorized color/letter pairs. The results demonstrated that when participants retained only two pairs of items, they could recall both pairs similarly quickly. However, when there were two or more memorized pairs, the most recent or internally attended pairs were recalled more quickly than the other pairs. These results suggest that memories in the "active" state are accessed first and memories that have overflowed into the "latent" state are accessed afterward. Additionally, the capacity of the easily accessible active state is extremely limited (to approximately two chunks of information) compared with the traditionally considered working memory capacity (four to seven chunks). These results provide robust behavioral support for the co-existence of multiple states in working memory and underscore the need for a more detailed classification of the working memory capacity. SIGNIFICANCE STATEMENTWe sometimes cannot quickly retrieve what we are sure we remember. Regarding working memory retrieval, we observed a phenomenon that the most recently encoded memory was retrieved quickly whereas others were retrieved afterward, showing an "overflow" of memory items from an easily accessible active state. This observation has two critical implications: 1) when maintaining multiple items in working memory, not all items are functionally the same, and there is a dissociation between easily accessible active items and items that have overflowed to a latent state; 2) the number of items that can be maintained in the active state is two, which is remarkably smaller than the traditionally considered working memory capacity of four, necessitating the update of working memory models.

neuroscience↗

bioRxiv2021

Rhythmic Accessibility to Sequential Working Memory in a Theta Phase-Dependent Manner

Working memory is active short-term memory storage that is easily accessible for later utilization. There is emerging evidence that memorized items are represented rhythmically on the specific phase of the theta-band (4-7 Hz) neural oscillation. However, it is still unknown how this process impacts the accessibility to the active memory storage. Here we show that simply memorizing sequential information causes theta-band fluctuation in our behaviour (i.e., reaction time, RT). We measured RTs to a visual probe that appeared at sequentially memorized locations after a random interval. Consequently, RTs to the probes fluctuated in the theta range as a function of the random interval, and the behavioural rhythmicity supported the hypothesis of the phase-dependent coding of sequential working memory. The current results demonstrate that our behaviour fluctuates unconsciously in the theta-range when recalling sequential memory, suggesting that accessibility to sequential working memory is rhythmic rather than stable, possibly reflecting theta-phase dependent coding.

neuroscience↗