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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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Lindquist LC, McIntire GR, Haigh SM. The effects of visual discomfort and chromaticity separation on neural processing during a visual task. Vision Res 2021; 182:27-35. [PMID: 33588291 PMCID: PMC7987861 DOI: 10.1016/j.visres.2021.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 12/13/2020] [Accepted: 01/14/2021] [Indexed: 01/23/2023]
Abstract
Visual stimuli that are uncomfortable to look at evoke a large neural response suggesting altered processing. While there is some evidence linking uncomfortable achromatic stimuli to impaired visual processing, the effect of uncomfortable chromatic patterns on visual cognition has yet to be explored. Large differences in chromaticity separation (e.g. red and blue) elicit visual discomfort, larger metabolic responses, larger visual evoked potentials, and greater alpha suppression compared to small chromaticity separations (e.g. pink and purple). We investigated the impact of stimuli that varied in their chromaticity separation (calculated in perceptual color space) on a visual task and their effect on neural responses across the cortex. Thirty participants completed a continuous pairs task (letters changed at 3 Hz) while grating patterns that differed in their chromaticity separation alternated with a grey screen at 5 Hz. The different temporal frequencies allowed for steady-state visual evoked potentials (SSVEPs) to the two stimulus-types to be measured simultaneously using electroencephalography (EEG). A subset of participants rated the gratings on a 9-point scale of discomfort. We observed greater ratings of discomfort and increased power at 5 Hz with the larger chromaticity separations. The increase in 5 Hz power with greater chromaticity separation was evident across the cortex. However, there was no significant effect of chromaticity separation on power at 3 Hz, or on reaction times, and no consistent effect on behavioral accuracy. Despite eliciting heightened neural responses across the cortex, short term exposure to uncomfortable chromatic stimuli does not adversely impact visual task performance.
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Affiliation(s)
- Lisa C Lindquist
- Center for Integrative Neuroscience, University of Nevada, Reno, 1664 North Virginia Street, Reno, NV 89557, United States
| | - Gregory R McIntire
- Center for Integrative Neuroscience, University of Nevada, Reno, 1664 North Virginia Street, Reno, NV 89557, United States
| | - Sarah M Haigh
- Center for Integrative Neuroscience, University of Nevada, Reno, 1664 North Virginia Street, Reno, NV 89557, United States.
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Morgan P, Macken B, Toet A, Bompas A, Bray M, Rushton S, Jones D. Distraction for the eye and ear. THEORETICAL ISSUES IN ERGONOMICS SCIENCE 2020. [DOI: 10.1080/1463922x.2020.1712493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Philip Morgan
- HuFEx, School of Psychology, Cardiff University, Cardiff, UK
| | - Bill Macken
- HuFEx, School of Psychology, Cardiff University, Cardiff, UK
| | - Alexander Toet
- The Netherlands Organization for Applied Scientific Research
| | - Aline Bompas
- HuFEx, School of Psychology, Cardiff University, Cardiff, UK
| | - Mark Bray
- BAE Systems-Applied Intelligence Laboratories, London, UK
| | - Simon Rushton
- HuFEx, School of Psychology, Cardiff University, Cardiff, UK
| | - Dylan Jones
- HuFEx, School of Psychology, Cardiff University, Cardiff, UK
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Photosensitivity and epilepsy: Current concepts and perspectives-A narrative review. Seizure 2017; 50:209-218. [PMID: 28532712 DOI: 10.1016/j.seizure.2017.04.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 03/31/2017] [Accepted: 04/04/2017] [Indexed: 01/15/2023] Open
Abstract
The authors review the influence of photic stimuli on the generation of epileptic seizures, addressing the first descriptions of the phenomenon and its subsequent exploration. Initially defined in the 1950's, links between intermittent photic stimulation (IPS) and seizures were well understood by the 1970. Since then the increasing exposure to photic stimuli associated with modern life (for instance through TVs, patterns, computer games and electronic instruments with flickering displays) has led to an increased interest in this issue. Diverse stimulation procedures have been described and difference in the effects of stimulation frequencies and types, colour and lighting have been recognised. Approximately 5% of patients with epilepsy have photosensitive epilepsy (PSE). PSE is commoner in younger individuals, more frequent in women, often time-limited, generally easy to treat and closely related to generalised epilepsies, especially Juvenile Myoclonic Epilepsy (JME). Structural and functional studies of PSE indicate abnormalities beyond the frontal lobes and evidence for the role of the visual cortex in human PSE. A reduction in connectivity between prefrontal and frontopolar regions and increased connectivity between occipital cortex and the supplementary motor area may be the basis for triggering motor seizures in JME. Due to the changes observed in such areas, it is hypothesised that photoparoxysmal responses (PPR) could be a final expression of pathogenic phenomena in the striato-thalamocortical system, and possibly a core feature of JME as system epilepsy. The familial transmission of epileptiform responses to IPS is well-recognised, but no clear relation between PSE and specific genes has emerged. Although the influence of ethnic factors on PSE has been widely studied, clear conclusions are still lacking. Pharmacological therapeutic approaches are beyond the scope of this review although preventive measures allowing patients to avoid PS seizure initiation and/or generalisation are discussed. Given the gender/age group most commonly affected by PSE, the risks and benefits of drug treatment need to be carefully weighed up.
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Bimler D. Flicker between equal-luminance colors examined with multidimensional scaling. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2010; 27:523-531. [PMID: 20208944 DOI: 10.1364/josaa.27.000523] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Even when two rapidly alternating color stimuli are equated in luminance, the flicker between them is not always zero. By one hypothesis this residual chromatic flicker is tritanopic, like edge distinctness: dependent purely on L- and M-cone stimulation, with no contribution from S-cones. Judgments of flicker intensity between pairs of colors were analyzed with multidimensional scaling (MDS)--in effect treating them as an index of color dissimilarity. They reveal a systematic reduction of flicker when stimulus pairs differ along a chartreuse-magenta direction in the color plane, corresponding to an effective compression of color space along this axis or an equivalent elongation along a blue-orange axis. In contrast, judgments of edge distinctness between the same pairs reveal the expected tritanopic axis of compression. It follows that chromatic flicker does receive a contribution from S-cone stimulation, but this interacts with the contribution from L- and M-cones, perhaps due to phase delays.
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Affiliation(s)
- David Bimler
- Department of Health and Human Development, Massey University, Private Bag 11-222, Palmerston North, New Zealand.
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Bhagat M, Bhushan C, Saha G, Shimjo S, Watanabe K, Bhattacharya J. Investigating neuromagnetic brain responses against chromatic flickering stimuli by wavelet entropies. PLoS One 2009; 4:e7173. [PMID: 19779630 PMCID: PMC2747006 DOI: 10.1371/journal.pone.0007173] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2009] [Accepted: 08/23/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Photosensitive epilepsy is a type of reflexive epilepsy triggered by various visual stimuli including colourful ones. Despite the ubiquitous presence of colorful displays, brain responses against different colour combinations are not properly studied. METHODOLOGY/PRINCIPAL FINDINGS Here, we studied the photosensitivity of the human brain against three types of chromatic flickering stimuli by recording neuromagnetic brain responses (magnetoencephalogram, MEG) from nine adult controls, an unmedicated patient, a medicated patient, and two controls age-matched with patients. Dynamical complexities of MEG signals were investigated by a family of wavelet entropies. Wavelet entropy is a newly proposed measure to characterize large scale brain responses, which quantifies the degree of order/disorder associated with a multi-frequency signal response. In particular, we found that as compared to the unmedicated patient, controls showed significantly larger wavelet entropy values. We also found that Renyi entropy is the most powerful feature for the participant classification. Finally, we also demonstrated the effect of combinational chromatic sensitivity on the underlying order/disorder in MEG signals. CONCLUSIONS/SIGNIFICANCE Our results suggest that when perturbed by potentially epileptic-triggering stimulus, healthy human brain manages to maintain a non-deterministic, possibly nonlinear state, with high degree of disorder, but an epileptic brain represents a highly ordered state which making it prone to hyper-excitation. Further, certain colour combination was found to be more threatening than other combinations.
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Affiliation(s)
- Mayank Bhagat
- Department of Electrical Engineering, Indian Institute of Technology, Kharagpur, India
| | - Chitresh Bhushan
- Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur, India
| | - Goutam Saha
- Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur, India
| | - Shinsuke Shimjo
- Department of Biology, California Institute of Technology, Pasadena, California, United States of America
- NTT Communication Sciences Laboratories, Atsugi, Kanagawa, Japan
- Exploratory Research for Advanced Technology (ERATO), Japan Science & Technology Agency, Atsugi, Kanagawa, Japan
| | - Katsumi Watanabe
- Exploratory Research for Advanced Technology (ERATO), Japan Science & Technology Agency, Atsugi, Kanagawa, Japan
- Research Center of Advanced Science and Technology, University of Tokyo, Tokyo, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
| | - Joydeep Bhattacharya
- Department of Psychology, Goldsmiths College, University of London, London, United Kingdom
- Commission for Scientific Visualization, Austrian Academy of Sciences, Vienna, Austria
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Pastor MA, Valencia M, Artieda J, Alegre M, Masdeu JC. Topography of Cortical Activation Differs for Fundamental and Harmonic Frequencies of the Steady-State Visual-Evoked Responses. An EEG and PET H215O Study. Cereb Cortex 2006; 17:1899-905. [PMID: 17060366 DOI: 10.1093/cercor/bhl098] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In humans, visual flicker stimuli of graded frequency (2-90 Hz) elicit an electroencephalographic (EEG) steady-state visual-evoked response (SSVER) with the same fundamental frequency as the stimulus and, in addition, a series of harmonic responses. The fundamental component of the SSVER is generated by increased synaptic activity in primary visual cortex (V1). We set out to determine the cortical origin of the harmonic responses in humans. For this purpose, we recorded the SSVERs at 5 different frequencies (5, 10, 15, 25, and 40 Hz) and measured regional cerebral blood flow (rCBF) with positron emission tomography-H(2)(15)O at rest and during visual stimulation at the same frequencies. The rCBF contrast weighted by the amplitude of the SSVERs first harmonics showed activation of a swath of cortex perpendicular to V1, including mostly the inferior half of the parieto-occipital sulcus. This area overlapped minimally with the primary visual cortex activated by the fundamental frequency. A different method, estimating EEG cortical source current density with low-resolution brain electromagnetic tomography, gave the same results. Our finding suggests that the inferior portion of the banks of the parieto-occipital sulci contains association visual cortex involved in the processing of stimuli that can be as simple as a flickering light source.
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Affiliation(s)
- M A Pastor
- Department of the Neurological Sciences, Center for Applied Medical Research, University of Navarra School of Medicine and the Clínica Universitaria de Navarra, Pamplona, Spain
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