Faster than the brain’s speed of light: Retinocortical interactions differ in high frequency activity when processing darks and lights

Abstract

Some studies suggest that the processing of darks benefits from greater neural resources in the visual system and potentially occurs faster. However, evidence from the human is still sparse, especially with respect to retinocortical interactions. We recorded retinal and cortical responses to 480 ms light flashes simultaneously with electroretinography (ERG) and magnetencephalography (MEG) in ten participants and analyzed the high frequency responses to the flash onsets and offsets.We show that high frequency oscillations for flash offsets occur earlier than flash onsets in the cortex but not in the retina. Interestingly, while the onset activity involved a wide range of frequencies Hz in the retina, and 55-145 Hz in the cortex), the offset response was restricted to the 75-95 Hz frequency band in both retina and cortex. The results suggest faster propagation times but not earlier retinal processing for darks than lights, suggesting a thalamic role. They also support previous findings that the retinal high frequency activity is transmitted to cortex. Furthermore, the outcomes add to the ongoing discussion about the function of narrowband oscillations in the human visual system.

MVPA Analysis of Intertrial Phase Coherence of Neuromagnetic Responses to Words Reliably Classifies Multiple Levels of Language Processing in the Brain

“…Source reconstruction was conducted using an LCMV beamformer (Van Veen et al, 1997) using planar gradiometer data and previously developed (Westner, 2017; Westner and Dalal, 2017) Hilbert beamformer. The decision to use only gradiometers was chosen as mixing channel types is not trivial due to magnetometers and planar gradiometers producing values of different scales; furthermore planar gradiometers are less sensitive to external magnetic sources and have a better signal-to-noise ratio compared to magnetometers (Hari et al, 1988).…”

Neural language processing across time, space, frequency and age: MEG-MVPA classification of intertrial phase coherence

“…Source reconstruction was carried out based on planar gradiometer data using a unit-noisegain scalar LCMV beamformer (Van Veen et al, 1997) and a Hilbert transformation-based beamforming technique (Westner, 2017;Westner & Dalal, 2017). For the adaptive filter, source orientation was optimised by using the orientation of maximum signal power; the output value selected was the neural activity index (NAI, Sekihara & Nagarajan, 2008).…”

Contactless recordings of retinal activity using optically pumped magnetometers

“…Concurrent with the a-wave is a high-frequency oscillatory burst (centered around 120 Hz), the oscillatory potential (Fröhlich, 1914;Munk and Neuenschwander, 2000). Its origin is attributed to diverse cell populations (Doty and Kimura, 1963;Kenyon et al, 2003;Frishman, 2013) and it is transmitted to visual cortex (Lopez and Sannita, 1997;Neuenschwander et al, 2002;Todorov et al, 2016;Westner and Dalal, 2019, but see Doty and Kimura, 1963;Heinrich and Bach, 2004;Molotchnikoff et al, 1975).…”