May 2007
Volume 48, Issue 13
ARVO Annual Meeting Abstract  |   May 2007
Non-Invasively Introduced Longterm-Potentiation of VEP Responses Without PERG Changes
Author Affiliations & Notes
  • A.-L. Wurschum
    Universitaet Wuerzburg, Wuerzburg, Germany
  • J. Classen
    Universitaet Wuerzburg, Wuerzburg, Germany
    Neurologische Klinik,
  • T. Meigen
    Universitaet Wuerzburg, Wuerzburg, Germany
  • Footnotes
    Commercial Relationships A. Wurschum, None; J. Classen, None; T. Meigen, None.
  • Footnotes
    Support None.
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 2343. doi:
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      A.-L. Wurschum, J. Classen, T. Meigen; Non-Invasively Introduced Longterm-Potentiation of VEP Responses Without PERG Changes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2343.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose:: Recent research has shown that cortical longterm-potentiation (LTP), introduced non-invasively by rapid visual stimulation with sine wave-gratings (photic tetanus) is specific to spatial-frequency (McNair et al. 2006). The aim of this study was to assure that LTP-like effects are not due to adaptation on a retinal level.

Methods:: 19 visually normal subjects were examined. We simultaneously recorded pattern electroretinograms (PERGs) using DTL electrodes and visual evoked potentials (VEPs) using 3 occipital positions (Oz, 3.5 cm lateral to the left and right of Oz). All recordings were preformed monocularly from the right eye. During the 2 pre-tetanic blocks horizontal sinusoidal gratings of 2 different spacial frequencies (1cpd, 5cpd) were presented for 33ms with randomly jittered inter-stimulus intervals of 1000-1500ms. During the photic tetanus, sinusoidal gratings with a spatial frequency of either 1cpd or 5cpd were presented with a temporal frequency of 8.6 Hz for 2 minutes. Two post-tetanic blocks consisting of the same stimuli as the pre-tetanic blocks followed the photic tetanus. In order to quantify systematic effects of the photic tetanus we subtracted PERGs and VEPs of the pre-tetanic blocks from the post-tetanic block. In order to evaluate, whether these effects exceeded normal fluctuations a similar comparison was preformed for both pre-tetanic and both post-tetanic blocks. Statistical significance was evaluated by "projection onto centroid difference vectors" (Achim, 2001).

Results:: No significant differences in waveform of the PERG could be shown, when pre- and post-tetanic blocks were compared. We did though find significant differences (p<5%) in grand mean VEP waveform between the pre-tetanic and the post-tetanic blocks in both tetanized and non-tetanized sinusoidal gratings in the group tetanized with 5cpd gratings. Significant differences could be shown between both pre-tetanic blocks for both sinusoidal gratings.

Conclusions:: We showed that LTP modulations of VEP responses are not due to adaptive processes in the retina. The significant changes in VEP waveform between the two pre-tetanic blocks indicate that even the presentation of non-tetanic stimuli can affect responses of subsequent VEP recordings. Our data suggest that a different experimental design is required to properly separate possible spatial frequency specific effects of tetanic stimulation on VEP responses from more general adaptive modulations.

Keywords: visual cortex • electrophysiology: non-clinical • adaptation: pattern 

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