ELSEVIER Electroencephalography and clinical Neurophysiology96 (1995) 502-508 Short latency visual evoked potentials to flashes from light-emitting diodes Hillel Pratt *, Naomi Bleich, William Hal Martin EL,oked Potentials l~lboratory, Behavioral Biology. Gutwirth Bldg., Technion-lsrael hlstitute of Technology, HaiI'a 32000. Israel Accepted for publication: 25 April 1995 Abstract Short latency visual evoked potentials (SVEPs) have been described in response to high-intensity, strobe flashes, High-intensity flashes can now be generated from goggle-mounted light emitting diodes (LEDs) and the SVEPs to such flashes have been shown to be reproducible across subjects, avoiding photic spread to the examination room and acoustical artifacts from the strobe stimulator. In this study, SVEPs from multichannel records are described in terms of normative latencies and amplitudes, as well as scalp distributions, to explore their generators. Potentials were recorded from 10 young male subjects, from 16 scalp locations, in response to flashes from goggle-mounted LEDs. Flashes were presented to each eye in turn, as well as binocularly. The latencies, scalp distributions and intersubject variabilities of the LED evoked SVEPs were similar to those obtained with strobe flashes. SVEP components were divided into 3 groups, according to their latency and the electrodes at which they were recorded with the largest amplitudes: periocular (under 40 msec latency), fronto-central (40-55 msec) and paricto-occipital (55-80 msec latency). The scalp distributions observed in this study suggest subcortical generators along the visual pathway, beginning at the retina. The use of goggle-mounted LEDs should promote routine evaluation of the integrity of the visual pathway between retina and cortex using SVEPs. Keywords: Short latency VEP; Flash; Sub-cortical; Human 1. Introduction Surface recorded short latency visual evoked potentials (SVEPs), other than the electroretinogram (ERG), have been described since the early days of evoked potentials, typically in response to very bright flashes (Cobb and Dawson, 1960; Ciganek, 1961; Allison et al., 1977). The components earlier than 45 msec have been attributed to the retinal oscillatory potentials (Pratt et al., 1982), but those at latencies from 45 to 80 msec are generally agreed to be of retrobulbar and for the most part subcortical origin (Cracco and Cracco, 1978; Harding and Rubinstein, 1980; Siegfried and Lukas, 1981; Pratt et al., 1982, 1986; Whit- taker and Siegfried, 1983; Perez-Arroyo and Chiappa, 1985). SVEPs have been found to exhibit small inter- and * Corresponding author. Tel.: +972 4 292321/226695: Fax: +972 4 229949; E-mail: MDR49BB@TECHNION.TECHNION.AC.IL. Present address: Garfield Auditory Research Lab, Temple University School of Medicine, 3440 N. Broad Street, Philadelphia, PA 19140, USA. intra-subject variability and clinical promise of sensitivity to lesions affecting the optic pathway (Harding and Rubin- stein, 1982; Pratt et al., 1982, 1986; Perez-Arroyo and Chiappa, 1985). The high intensity flashes necessary to evoke SVEPs have been generated by strobe stimulators. Such stimula- tors entail masking the discharge sound of the stimulator to avoid acoustically evoked artifacts. The photic spread of high intensity strobe flashes to the examination room may be disruptive to concurrent procedures such as intraopera- rive or intensive care monitoring. These limitations hin- dered the clinical use of strobe evoked SVEPs. Conven- tional light emitting diode (LED) stimulators avoid these pitfalls but their low luminosity evokes SVEPs that are low in amplitude and too variable to be useful. With the advent of high efficiency LEDs, high intensity flashes can now be generated from goggle-mounted LEDs, and the SVEPs to such flashes have been shown to be reproducible across subjects, avoiding the limitations of strobe stimula- tors (Pratt et al., 1994). 0168-5597/95/$09.50 © 1995 Elsevier Science Ireland Ltd. All rights reserved SSDI 00 I 3-4694(95)00089-5 EEP 94591