METHODS: Participants (N = 16; 8 boys; age 12.5 ± 0.8 years) performed, on separate days, HIIE cycling consisting of 8 × 1-min work-intervals at 100%-to-70% (HIIEH-L), 70%-to-100% (HIIEL-H) or 85% (HIIECON) peak power separated by 75 s recovery. Affect, enjoyment and cerebral haemodynamics (oxygenation (∆O2Hb), deoxygenation (∆HHb) and tissue oxygenation index (TOI)) were recorded before, during, and after all conditions.
RESULTS: Affect and enjoyment were lower during HIIEH-L compared to HIIEL-H and HIIECON at work-intervals 1 to 3 (all P 0.83) but were greater during HIIEH-L than HIIEL-H and HIIECON at work-interval 8 (all P 0.83). ∆O2Hb was similar across conditions (P = 0.87) but TOI and ∆HHb were significantly greater and lower, respectively during HIIEH-L compared to HIIEL-H and HIIECON at work-interval 8 (all P 0.40). Affect was correlated with TOI (all r > 0.92) and ∆HHb (all r > -0.73) across conditions.
CONCLUSIONS: HIIEH-L offers advancement to the HIIECON and HIIEL-H which bring significant greater affect and enjoyment towards the end HIIE work-interval, implicating the feasibility and adoption of this protocol for health promotion in youth. Also, changes in prefrontal cortex haemodynamics are associated with the affect during HIIE.
OBJECTIVE: We evaluated whether transorbital ACS modulates BOLD activity in early visual cortex using high-resolution 7 Tesla functional magnetic resonance imaging (fMRI).
METHODS: In this feasibility study transorbital ACS in the alpha range and sham ACS was applied in a random block design in five healthy subjects for 20 min at 1 mA. Brain activation in the visual areas V1, V2 and V3 were measured using 7 Tesla fMRI-based retinotopic mapping at the time points before (baseline) and after stimulation. In addition, we collected data from one hemianopic stroke patient with visual cortex damage after ten daily sessions with 25-50 min stimulation duration.
RESULTS: In healthy subjects transorbital ACS increased the activated cortical surface area, decreased the fMRI response amplitude and increased coherence in the visual cortex, which was most prominent in the full field task. In the patient, stimulation improved contrast sensitivity in the central visual field. BOLD amplitudes and coherence values were increased in most early visual areas in both hemispheres, with the most pronounced activation detected during eccentricity testing in retinotopic mapping.
CONCLUSIONS: This feasibility study showed that transorbital ACS modifies BOLD activity to visual stimulation, which outlasts the duration of the AC stimulation. This is in line with earlier neurophysiological findings of increased power in EEG recordings and functional connectivity reorganization in patients with impaired vision. Accordingly, the larger BOLD response area after stimulation can be explained by more coherent activation and lower variability in the activation. Alternatively, increased neuronal activity can also be taken into account. Controlled trials are needed to systematically evaluate the potential of repetitive transorbital ACS to improve visual function after visual pathway stroke and to determine the cause-effect relationship between neural and BOLD activity changes.
METHODS: Eight electronic databases (Web of Science, PubMed, ScienceDirect, American Psychological Association PsycNet, Cochrane Library, Scopus, Embase, and Ovid) were searched for the study. Articles published from January 1 to December 31, 2022, were considered for this review. A random-effects meta-analysis and between-study heterogeneity analysis were conducted using Comprehensive Meta-Analysis V3.0 software.
RESULTS: We identified 7829 articles of which 28 met the full inclusion criteria and were included in the systematic review and analyses. Our pooled analysis suggested that participants with MCI can be differentiated from HC by significant P200, P300, and N200 latencies. The P100 and P300 amplitudes were significantly smaller in participants with MCI when compared with those in the HCs, and the patients with MCI showed increased N200 amplitudes. Our findings provide new insights into potential electrophysiological biomarkers for diagnosing MCI.