Visual evoked potentials during suppression in exotropic and esotropic strabismics: strabismic suppression objectified
We performed an electrophysiological study in order to objectify suppression in strabismus. The extent of cortical involvement in the process of interocular suppression was also explored. Possible differences in the suppressive process of esotropic and exotropic strabismics were also studied.
An electroencephalographic recorder with eight leads was applied to the posterior one-third of the skull; three occipital, three parietal, and two temporal leads. We measured the activity of these visual cortical areas during stimulation of each eye under monocular as well as binocular viewing conditions with hemisinusoidal light pulses in a nature-like complex visual background. Recordings were made from six primary esotropic strabismic subjects and four primary exotropic and one consecutive exotropic strabismic subject. Also, five normal controls were studied.
A characteristic, triphasic response complex was found at approximately 80 ms following the start of each light pulse under monocular viewing conditions in the dominant and the nondominant eye. However, under dichoptic viewing conditions in the nondominant eye of all esotropic cases as well as in the nondominant eye of three of five exotropic cases, this response complex was completely absent. They showed approximately 100% reduction of their cortical response activity.
These results show the vast extent of the cortex that is involved in the suppressive process, giving a good insight in the power of suppression.
KeywordsEsotropia Exotropia Suppression Strabismus Visual evoked potential
- 4.Bagolini B (1976) Sensorial anomalies in strabismus (suppression, anomalous correspondence, amblyopia). Doc Ophthalmol 41:1–22Google Scholar
- 13.Fries P, Schroder JH, Singer W, Engel AK (2001) Conditions of perceptual selection and suppression during interocular rivalry in strabismic and normal cats. Vision Res 41:771–783Google Scholar
- 15.Gulyas B, Roland PE (1994) Binocular disparity discrimination in human cerebral cortex: functional anatomy by positron emission tomography. Proc Natl Acad Sci USA 91:1239–1243Google Scholar
- 17.Hillyard SA, Anllo-Vento L (1998) Event-related brain potentials in the study of visual selective attention. Proc Natl Acad Sci USA 95:781–787Google Scholar
- 26.Mauguiere F, Ceranic B, Cooper R, Holder GE, Luxon LM, Pottinger RC Abnormal waveforms and diagnostic yield of evoked potentials. Clinical neurophysiology, vol 1, EMG, Nerve conduction and evoked potentials, Chap. 3.5:497Google Scholar
- 28.Ogle KN (1962) The visual space sense. Science 138:763–771Google Scholar
- 36.Sommer M, Meinhardt J, Volz HP (2003) Combined measurement of event-related potentials (ERPs) and fMRI. Acta Neurobiol Exp (Warsz.) 63:49–53Google Scholar