Saccadic Suppression in the Magnocellular Pathway during Reading

Authors

  • Parameswari Shunmugam
  • Vijayakumar ‎
  • Nachiappan Murugavadigal

Abstract

Movement detection and acuity resolution deferentially affect the magnocellular, parvocellular and koniocellular pathways of the human visual neural system. Temporal and spatial frequency sensitivity measurements are used to identify the neural behaviour of these pathways. The magnocellular pathway (MP)  is  known to carry a limited range of temporal frequency components of signals resulting from a visual scene.  In this paper, we show a possible mechanism which will give rise to a fixed bandwidth of the temporal frequencies which can be conveyed by the MP during fixations and saccades. We will also explain why temporal frequency components outside this bandwidth are not available for the MP.  We have proposed two factors to explain our results. The first, which is neural in origin, is the correlated firing mechanism of the parasol ganglions which serve the MP and the second, which is  biophysical in origin,  is the windowing effect of saccades and fixations. Using the two mechanisms, we will show that the allowed temporal frequencies in  the MP have an unique upper and a lower bound. The upper bound arises from the fixed correlated firing time of the parasol retinal ganglions.  The lower bound is calculated using the windowing effect of eye fixations and saccades.  We will show how the combined effect of the correlated firing the retinal ganglions and the windowing effect of fixations and saccades provides an explanation for the various aspects of the observed phenomenon known as saccadic suppression.

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Published

2020-02-21

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Articles