Satoshi Umeda

Background: Alzheimer's disease (AD) accounts for the majority of dementia-related disorders among aging populations. Given the irreversible nature of AD, early detection of cognitive impairment is critical for improving prognosis and facilitating timely interventions before individuals meet the clinical criteria for AD. Objective: The objective of this review is to provide a comprehensive summary of recent advances in task-based electroencephalography (EEG), such as using attention and inhibitory control tasks, which has recently emerged as a promising non-invasive biomarker for assessing neurophysiological alterations associated with AD and mild cognitive impairment (MCI). Methods: This systematic review evaluates the efficacy of task-based EEG biomarkers in distinguishing cognitively impaired individuals from those without impairment. A comprehensive literature search was conducted across PubMed, Semantic Scholar, and SpringerLink databases for studies published between 2017 and 2024. Results: Findings indicate consistent neurophysiological alterations in MCI and AD, particularly reductions in event-related potential amplitudes and prolonged latencies, with P3 abnormalities observed in about half of the studies assessing selective attention and inhibitory control. Similarly, a comparable number of studies using working memory tasks report disrupted functional connectivity patterns, increased low-frequency oscillations (delta and theta activity), and reduced fast oscillations (alpha and beta activity). Conclusions: These EEG-based indices demonstrate potential as objective biomarkers for detecting neural alterations associated with cognitive decline in both AD and preclinical dementia stages. Further research is needed to standardize EEG protocols and validate their clinical utility for early diagnosis and disease progression monitoring.

Autonomic nervous system (ANS) is a mechanism that regulates our internal environment. In recent years, the interest in how tactile stimuli presented directly to the body affect ANS function and cortical processing in humans has been renewed. However, it is not yet clear how subtle tactile stimuli below the level of consciousness affect human heart rate and cortical processing. To examine this, subthreshold electrical stimuli were presented to the left forearm of 43 participants during an image-viewing task, and electrocardiogram (ECG) and electroencephalogram (EEG) data were collected. The changes in the R-wave interval of the ECG immediately after the subthreshold electrical presentation and heartbeat-evoked potential (HEP), the afferent signal processing of cardiac activity, were measured. The results showed that heart rate decelerated immediately after the presentation of subthreshold electrical stimuli. The HEP during stimulus presentation was amplified for participants with greater heart rate acceleration immediately after this deceleration. The magnitude of these effects depended on the type of the subthreshold tactile stimuli. The results suggest that even with subthreshold stimulation, the changes in autonomic activity associated with orienting response and related afferent signal processing differ depending on the clarity of the tactile stimuli.

広範な陳旧性の左後頭葉梗塞に加え，右後頭葉外側の新規脳梗塞にて熟知相貌に対する相貌失認を呈した症例を報告した．症例は70歳代の右利き男性であった．熟知相貌および表情の認知に困難さを認め，全般性注意機能，処理速度の低下がみられた．全般性認知機能および相貌認知以外の視覚認知機能は保たれていた．相貌失認は左右半球の後頭顔領域，紡錘状回顔領域，前部側頭葉の脳内ネットワークに機能不全が生じたことで発現したと考えられた．老若および性別の判断に関する相貌認知は保たれていた．拡散テンソルトラクトグラフィにより，右半球の下前頭後頭束や下縦束の白質線維が温存されたことが要因であると考えられた．さらに，全般性注意機能および処理速度の向上を図る認知リハビリテーション介入によって，表情認知の改善が得られる可能性が示唆された．

With the objective to investigate the role of the insula in recognizing emotion, we performed direct electrical stimulation over the anterior insular cortex during awake surgery while simultaneously delivering an emotional sensitivity task. We registered 18 consecutive patients with brain tumors associated with the insular lobe, who were undergoing tumor resection. An emotional sensitivity task was employed to measure the patients’ ability to recognize emotions from facial expressions before, during, and after awake surgery. Furthermore, we performed voxel-based lesion symptom mapping (VLSM) to identify the association between relevant brain lesions and emotion recognition. When we performed direct electrical stimulation over the anterior insular cortex during awake surgery, the results showed that the ability to recognize anger was significantly enhanced with the presence of anterior insular stimulation (p < 0.05). Comparing the performance in the emotional sensitivity task before and after surgery, the performance in the anger condition became worse (p < 0.01), but became better in the sadness condition after surgery (p < 0.01). In the case of anger recognition, lower scores in the correct response index were associated with lesions involving the left insula in the VLSM study. Direct electrical stimulation over the anterior insular cortex enhanced anger recognition in patients with insular tumors. In contrast, accuracy of anger recognition was significantly reduced, and sadness was improved, when the performance of emotional sensitivity was compared pre- and post-surgery. Our findings suggest that the insular cortex is involved in changes in emotion recognition, including anger and sadness recognition by modulating arousal level that is closely connected with interoception.

Background: Previous epidemiological and clinical studies have shown that dairy products have beneficial effects on cognitive decline and dementia. Enzymatic digestion of whey protein produces a whey peptide rich in tryptophan-tyrosine-related peptides which improve cognitive performance in mice. We evaluated the effects of whey peptides on cognitive functions in healthy adults in a randomized, double-blind, placebo-controlled design. Methods: 101 healthy adults (45 to 64 years), with a self-awareness of cognitive decline received either whey peptide or placebo supplements for 12 weeks. Changes in cognitive function were assessed using neuropsychological tests at 6 and 12 weeks after the start of supplementation. Results: Verbal fluency test (VFT) score changes tended to be higher in the whey peptide group compared with the placebo at 12 weeks. Subgroup analysis classified by the degree of subjective fatigue showed that changes in the VFT as well as the Stroop and subjective memory function tests between baseline and 6 weeks of intervention were significantly better in subjects with high-level fatigue from the whey peptide group as compared to the placebo group. Conclusions: Intake of whey peptide might improve cognitive function in healthy middle- and older-aged adults with high subjective fatigue levels. Further studies will elucidate the relationship among cognitive improvement, whey peptides, and psychological fatigue.