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Front Hum Neurosci. 2016 Aug 18;10:413. doi: 10.3389/fnhum.2016.00413. eCollection 2016.

Rod Driven Frequency Entrainment and Resonance Phenomena.

Author information

1
Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau Ilmenau, Germany.
2
Institute of Medical Statistics, Computer Sciences and Documentation, Jena University Hospital, Friedrich Schiller University Jena Jena, Germany.
3
Preston M. Green Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis MO, USA.
4
Institute of Biomedical Engineering and Informatics, Technische Universität IlmenauIlmenau, Germany; Hans Berger Department of Neurology, Biomagnetic Center, Jena University Hospital, Friedrich Schiller University JenaJena, Germany.

Abstract

A controversy exists on photic driving in the human visual cortex evoked by intermittent photic stimulation. Frequency entrainment and resonance phenomena are reported for frequencies higher than 12 Hz in some studies while missing in others. We hypothesized that this might be due to different experimental conditions, since both high and low intensity light stimulation were used. However, most studies do not report radiometric measurements, which makes it impossible to categorize the stimulation according to photopic, mesopic, and scotopic vision. Low intensity light stimulation might lead to scotopic vision, where rod perception dominates. In this study, we investigated photic driving for rod-dominated visual input under scotopic conditions. Twelve healthy volunteers were stimulated with low intensity light flashes at 20 stimulation frequencies, leading to rod activation only. The frequencies were multiples of the individual alpha frequency (α) of each volunteer in the range from 0.40 to 2.30(∗)α. Three hundred and six-channel whole head magnetoencephalography recordings were analyzed in time, frequency, and spatiotemporal domains with the Topographic Matching Pursuit algorithm. We found resonance phenomena and frequency entrainment for stimulations at or close to the individual alpha frequency (0.90-1.10(∗)α) and half of the alpha frequency (0.40-0.55(∗)α). No signs of resonance and frequency entrainment phenomena were revealed around 2.00(∗)α. Instead, on-responses at the beginning and off-responses at the end of each stimulation train were observed for the first time in a photic driving experiment at frequencies of 1.30-2.30(∗)α, indicating that the flicker fusion threshold was reached. All results, the resonance and entrainment as well as the fusion effects, provide evidence for rod-dominated photic driving in the visual cortex.

KEYWORDS:

alpha rhythm; frequency entrainment; magnetoencephalography; photic driving; resonance phenomena; rod-driven; visual system

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