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Many studies have examined the effects of transcranial alternating current stimulation (tACS) on working memory, showing that low-intensity stimulation can enhance cognitive performance by modulating neuronal activity, particularly in the frontal cortex and the parietal lobule. Specific frequencies, such as the gamma frequency, have demonstrated beneficial effects on memory under high cognitive load. However, tACS has technical limitations, including uncomfortable sensations and uneven diffusion of electrical currents within the brain, which restrict its effectiveness in deeper brain regions.
Transcranial alternating magnetic stimulation (tAMS) is emerging as a potentially more precise and comfortable method. Unlike tACS, tAMS uses magnetic fields that penetrate more deeply into the brain and provide a more homogeneous distribution of induced electrical currents, allowing for more targeted stimulation. This study compares the effects of tACS and tAMS on working memory, with the hypothesis that tAMS will offer additional advantages in terms of comfort and efficacy. Cognitive performance will be assessed using working memory tasks, along with EEG signals to analyze neuronal modulations. The objective is to demonstrate that tAMS more effectively reaches deep brain regions and improves cognitive functions.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| 40 Hz tACS stimulation | Experimental |
| |
| 60 Hz tACS stimulation | Experimental |
| |
| 40 Hz tAMS stimulation | Experimental |
| |
| 60 Hz tAMS stimulation | Experimental |
| |
| No stimulation | Sham Comparator |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Electrical stimulation | Other | The experimental session lasts 2 hours and 30 minutes and includes four phases: Time 0, dedicated to training and adjustment of task difficulty, followed by Time 1, Time 2, and Time 3, corresponding respectively to assessments of working memory performance before, during, and after exposure to stimulation. Each phase includes blocks of the Sternberg task, for a total of 180 trials per session. Each block lasts 10 minutes. |
| Measure | Description | Time Frame |
|---|---|---|
| Sternberg task | During each trial, participants memorize a sequence of eight letters presented sequentially. They are then shown a probe letter displayed in blue and must indicate whether this letter was part of the memorized sequence. Participant performance will be evaluated based on two behavioral measures: accuracy (proportions of correct and incorrect responses) and reaction time in milliseconds. | Baseline (Day 1, before exposure), periprocedural (Day 1, during exposure), and post-intervention (Day 1, immediately after exposure) |
| Measure | Description | Time Frame |
|---|---|---|
| EEG Power Outcomes | Absolute power of EEG frequency bands will be measured using power spectral density analysis to quantify the energy within each frequency band associated with working memory. | Baseline (Day 1, before exposure), periprocedural (Day 1, during exposure), and post-intervention (Day 1, immediately after exposure) |
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Inclusion Criteria:
Non inclusion Criteria:
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| ID | Term |
|---|---|
| D004558 | Electric Stimulation |
| ID | Term |
|---|---|
| D010812 | Physical Stimulation |
| D008919 | Investigative Techniques |
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| Magnetic stimulation | Other | The experimental session lasts 2 hours and 30 minutes and includes four time points: Time 0, dedicated to training and adjustment of task difficulty, followed by Time 1, Time 2, and Time 3, corresponding respectively to assessments of working memory performance before, during, and after exposure to stimulation. Each time point includes blocks of the Sternberg task, for a total of 180 trials per session. Each block lasts 10 minutes. |
|
| No stimulation | Other | The experimental session lasts 2 hours and 30 minutes and includes four time points: Time 0, dedicated to training and adjustment of task difficulty, followed by Time 1, Time 2, and Time 3, corresponding respectively to assessments of working memory performance before, during, and after exposure to sham stimulation. Each time point includes blocks of the Sternberg task, for a total of 180 trials per session. Each block lasts 10 minutes. |
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| EEG Power Outcomes |
Relative power of EEG frequency bands will be calculated as the proportion of power in each frequency band relative to the total EEG signal power. |
| Baseline (Day 1, before exposure), periprocedural (Day 1, during exposure), and post-intervention (Day 1, immediately after exposure) |
| EEG Power Outcomes | Mean frequency of the EEG signal will be calculated from the power spectral density to characterize frequency distribution related to working memory processes. | Baseline (Day 1, before exposure), periprocedural (Day 1, during exposure), and post-intervention (Day 1, immediately after exposure) |
| EEG Power Outcomes | Median frequency of the EEG signal will be derived from the power spectral density as an indicator of the central tendency of EEG frequency content. | Baseline (Day 1, before exposure), periprocedural (Day 1, during exposure), and post-intervention (Day 1, immediately after exposure) |
| EEG Power Outcomes | Peak power frequency of the EEG signal will be identified as the frequency at which maximum power occurs. | Baseline (Day 1, before exposure), periprocedural (Day 1, during exposure), and post-intervention (Day 1, immediately after exposure) |
| EEG Signal Regularity Outcomes (RQA) | Recurrence rate derived from recurrence quantification analysis will be used to quantify the proportion of recurrent patterns in the EEG signal. | Baseline (Day 1, before exposure), periprocedural (Day 1, during exposure), and post-intervention (Day 1, immediately after exposure) |
| EEG Signal Regularity Outcomes (RQA) | Determinism derived from recurrence quantification analysis will be used to assess the temporal organization and regularity of EEG signal dynamics. | Baseline (Day 1, before exposure), periprocedural (Day 1, during exposure), and post-intervention (Day 1, immediately after exposure) |
| Neuropsychological data | Score from the Multidimensional Fatigue Inventory (MFI-20) will be used to assess fatigue. The Multidimensional Fatigue Inventory is a self-reported questionnaire with total scores ranging from 20 to 100. Higher scores reflect higher levels of fatigue. | Baseline (Day 1, before exposure) |
| Neuropsychological data | Score from the State-Trait Anxiety Inventory (STAI) will be used to assess anxiety. The State-Trait Anxiety Inventory is a self-reported questionnaire with scores ranging from 20 to 80. Higher scores reflect higher levels of anxiety. | Baseline (Day 1, before exposure) |