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Łabęcki M, Nowicka MM, Wróbel A, Suffczynski P. Frequency-dependent dynamics of steady-state visual evoked potentials under sustained flicker stimulation. Sci Rep 2024; 14:9281. [PMID: 38654008 DOI: 10.1038/s41598-024-59770-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 04/15/2024] [Indexed: 04/25/2024] Open
Abstract
Steady-state visual evoked potentials (SSVEP) are electroencephalographic signals elicited when the brain is exposed to a visual stimulus with a steady frequency. We analyzed the temporal dynamics of SSVEP during sustained flicker stimulation at 5, 10, 15, 20 and 40 Hz. We found that the amplitudes of the responses were not stable over time. For a 5 Hz stimulus, the responses progressively increased, while, for higher flicker frequencies, the amplitude increased during the first few seconds and often showed a continuous decline afterward. We hypothesize that these two distinct sets of frequency-dependent SSVEP signal properties reflect the contribution of parvocellular and magnocellular visual pathways generating sustained and transient responses, respectively. These results may have important applications for SSVEP signals used in research and brain-computer interface technology and may contribute to a better understanding of the frequency-dependent temporal mechanisms involved in the processing of prolonged periodic visual stimuli.
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Affiliation(s)
- Maciej Łabęcki
- Department of Biomedical Physics, Faculty of Physics, University of Warsaw, 5 Pasteur St, 02-093, Warsaw, Poland
| | - Maria Małgorzata Nowicka
- Laboratory of Language Neurobiology, Nencki Institute of Experimental Biology, 3 Pasteur St, 02-093, Warsaw, Poland
| | - Andrzej Wróbel
- Laboratory of Neuroinformatics, Nencki Institute of Experimental Biology, 3 Pasteur St, 02-093, Warsaw, Poland
- Department of Epistemology, Faculty of Philosophy, University of Warsaw, 3 Krakowskie Przedmiescie St, 00-047, Warsaw, Poland
| | - Piotr Suffczynski
- Department of Biomedical Physics, Faculty of Physics, University of Warsaw, 5 Pasteur St, 02-093, Warsaw, Poland.
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Henney MA, Carstensen M, Thorning-Schmidt M, Kubińska M, Grønberg MG, Nguyen M, Madsen KH, Clemmensen LKH, Petersen PM. Brain stimulation with 40 Hz heterochromatic flicker extended beyond red, green, and blue. Sci Rep 2024; 14:2147. [PMID: 38273009 PMCID: PMC10810780 DOI: 10.1038/s41598-024-52679-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 01/21/2024] [Indexed: 01/27/2024] Open
Abstract
Alzheimer's disease (AD) is associated with electrophysiological changes in the brain. Pre-clinical and early clinical trials have shown promising results for the possible therapy of AD with 40 Hz neurostimulation. The most notable findings used stroboscopic flicker, but this technique poses an inherent barrier for human applications due to its visible flickering and resulting high level of perceived discomfort. Therefore, alternative options should be investigated for entraining 40 Hz brain activity with light sources that appear less flickering. Previously, chromatic flicker based on red, green, and blue (RGB) have been studied in the context of brain-computer interfaces, but this is an incomplete representation of the colours in the visual spectrum. This study introduces a new kind of heterochromatic flicker based on spectral combinations of blue, cyan, green, lime, amber, and red (BCGLAR). These combinations are investigated by the steady-state visually evoked potential (SSVEP) response from the flicker with an aim of optimising the choice of 40 Hz light stimulation with spectrally similar colour combinations in BCGLAR space. Thirty healthy young volunteers were stimulated with heterochromatic flicker in an electroencephalography experiment with randomised complete block design. Responses were quantified as the 40 Hz signal-to-noise ratio and analysed using mixed linear models. The size of the SSVEP response to heterochromatic flicker is dependent on colour combinations and influenced by both visual and non-visual effects. The amber-red flicker combination evoked the highest SSVEP, and combinations that included blue and/or red consistently evoked higher SSVEP than combinations only with mid-spectrum colours. Including a colour from either extreme of the visual spectrum (blue and/or red) in at least one of the dyadic phases appears to be more important than choosing pairs of colours that are far from each other on the visual spectrum. Spectrally adjacent colour pairs appear less flickering to the perceiver, and thus the results motivate investigations into the limits for how alike the two phases can be and still evoke a 40 Hz response. Specifically, combining a colour on either extreme of the visual spectrum with another proximal colour might provide the best trade-off between flickering sensation and SSVEP magnitude.
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Affiliation(s)
- Mark Alexander Henney
- Department of Applied Mathematics and Computer Science, Technichal University of Denmark, Kgs. Lyngby, 2800, Denmark.
- OptoCeutics ApS, Copenhagen, 1610, Denmark.
| | - Marcus Carstensen
- OptoCeutics ApS, Copenhagen, 1610, Denmark
- Department of Electrical and Photonics Engineering, Technichal University of Denmark, Kgs. Lyngby, 2800, Denmark
| | - Martin Thorning-Schmidt
- OptoCeutics ApS, Copenhagen, 1610, Denmark
- Department of Electrical and Photonics Engineering, Technichal University of Denmark, Kgs. Lyngby, 2800, Denmark
| | - Marta Kubińska
- OptoCeutics ApS, Copenhagen, 1610, Denmark
- Department of Electrical and Photonics Engineering, Technichal University of Denmark, Kgs. Lyngby, 2800, Denmark
| | - Manja Gersholm Grønberg
- Department of Applied Mathematics and Computer Science, Technichal University of Denmark, Kgs. Lyngby, 2800, Denmark
| | - Mai Nguyen
- OptoCeutics ApS, Copenhagen, 1610, Denmark
| | - Kristoffer Hougaard Madsen
- Department of Applied Mathematics and Computer Science, Technichal University of Denmark, Kgs. Lyngby, 2800, Denmark
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Hvidovre, 2650, Denmark
| | | | - Paul Michael Petersen
- Department of Electrical and Photonics Engineering, Technichal University of Denmark, Kgs. Lyngby, 2800, Denmark
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