Molnár, Linett (2025) The Effects of Transcranial Alternating Current Stimulation (tACS) Over the Occipito-Parietal Cortex on Visuospatial Attention. Bachelor thesis, Psychology.
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Abstract
Multiple brain mechanisms regulate visuospatial attention, one of the many cognitive processes in which neural oscillations are essential. Alpha-range oscillations (7–13 Hz) have repeatedly been found to decrease during periods of increased attention. Researchers have used transcranial alternating current stimulation (tACS), a non-invasive neurostimulation technique aimed to modulate the rhythmicity of brain activity, to explore causal relationships between oscillations and cognition. The current thesis aims to present a conceptual replication study aimed at replicating previous findings that alpha tACS applied to the left or right occipito-parietal cortex reduces visuospatial attention in the contralateral hemifield. It was hypothesised that independent of cue validity, applying tACS would result in slower reaction times and lower accuracy in the ipsilateral hemifield. Additionally, it was expected that valid trials, regardless of stimulation, would result in faster reaction times and higher accuracy compared to invalid trials. 11 participants completed a Posner visuospatial attention task during three experimental conditions: left, right, and sham tACS. The hypothesis concerning validity and reaction times was confirmed, further supporting decades of research validating the Posner task. However, no significant effects of tACS were found, consistent with previous null findings. Several factors may explain this, including individual variability, lack of phase alignment, or insufficient stimulation intensity. A previously unanticipated result showed that cues on the left hemifield resulted in slower reaction times compared to those in the right hemifield. The finding broadly supports the idea that visuospatial attention might be biased toward the left visual field. Nevertheless, as this is an interim analysis, the full project may yield different results, and a larger sample will be needed to confirm these preliminary findings.
| Item Type: | Thesis (Bachelor) |
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| Supervisor name: | Wischnewski, M. and Mathot, S. |
| Degree programme: | Psychology |
| Differentiation route: | None [Bachelor Psychology] |
| Date Deposited: | 02 Jul 2025 13:50 |
| Last Modified: | 02 Jul 2025 13:50 |
| URI: | http://gmwpublic.studenttheses.ub.rug.nl/id/eprint/5256 |
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