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The electrical response of the retina was examined as a function of retinal region, using stimuli of various spatial frequencies in the first experiment. In the second experiment, the regional response of the retina to defocus at high and low spatial frequencies was investigated. Twenty three subjects were recruited for global flash multifocal electroretinogram (mfERG) in experiment 1. Black and white gratings (printed on plastic transparent sheets) of four spatial frequencies (SF), 0.24, 1.2, 2.4 and 4.8 cycle per degree were presented in front of the mfERG stimulation. The amplitudes and implicit times of the direct (DC) and induced (IC) components of mfERG responses were pooled into six concentric rings for analysis. There was low amplitude DC at low SF, which increased with increasing SF, and which decreased with increasing eccentricity. The IC was high in amplitude at all SF and reduced in amplitude with increasing eccentricity. Our findings suggested that outer and inner retina had different characteristics in processing spatial details. In experiment 2, Twenty-three young adults were recruited for mfERG measurement. The retinal electrical responses for low (0.24cpd) and high (4.8cpd) SF under fully corrected conditions of short-term negative defocus (-2D) and short term positive defocus (+2D) conditions were measured. There was a sign-dependent response to defocus in the DC response, mainly in peripheral regions. The sign dependent response at low SF was more obvious than that at high SF, and was located more peripherally. The IC response showed no clear trends for either defocus condition. The human retina seems to have a decoding system for optical defocus, which was tuned for low spatial frequency, and was located in the retinal near periphery.

Lycium Barbarum Polysaccharides (LBP) are the active components of Wolfberry (a traditional Chinese medicine) which has long been used for improving visual function. This study aims to investigate localized changes of retinal function in a partial optic nerve transection (PONT) model, and effects of LBP on visual function. The multifocal electroretinograms (mfERG) were obtained from 30 eyes of 30 Sprague-Dawley rats. The rats were divided into 6 groups (five treatment groups and one control group). Starting from the first day of the experiment, the rats in the (PONT+LBP) group and the (LBP) group were dosed with LBP; rats in the (PONT+PBS (phosphate buffered saline)) group and the (PBS) group were dosed with PBS via nasogastric tube every day until euthanized. The dorsal part of the optic nerve was transected in the (PONT), (PONT+LBP) and (PONT+PBS) groups at the end of week 1 (day 7 after LBP or PBS feeding began). The mfERG was measured at three time points: week 2, week 3 and week 5. Significant reduction of P1 and PhNR amplitudes of the mfERG were observed in all retinal regions a week after PONT. Feeding with LBP prior to PONT preserved retinal function. All mfERG responses returned to the normal range in the superior retina, which corresponds to the transected dorsal region of the optic nerve, while most of the inferior retinal responses were significantly increased at week 4 after PONT. The ventral part of the retina had secondary degeneration which was not only limited to the ganglion cell layer, but is a widespread effect affecting the outer retina. LBP altered the functional reduction caused by PONT by regulating the signal from the outer retina.

Purpose: The aim of this study was to obtain a better understanding of the cellular contributions to the chick global flash mfERG by using a pharmacological dissection method. Method: Global flash mfERGs were recorded from 11 white leghorn chicks (Gallus gallus). The inner retinal response was suppressed by injection of tetrodotoxin (TTX) and N-methyl-D-aspartic acid (NMDA). Responses from ON- and OFF-pathway were isolated by further injection of 2-amino-4-phosphonobutyric acid (APB). Results: The global flash mfERG of white leghorn chicks consist of a direct component (DC) originated from outer retina and a late induced component (IC) originated from the inner retina which are comparable to the global flash mfERG responses from primate, porcine and human. The ON- and OFF- responses found in chicks are also similar to that of porcine and primate with the N1 component is mainly from OFF-bipolar responses and the ON-response contributes mainly in the P1 component. Conclusion: Because of the similarities for the global flash mfERG found in chick to other species, this makes the possibility of using chick retina as a potential animal model for eye research in the area of mfERG.

Introduction: Adaptation is one of the key characteristic of our vision which can maximize the visual function. It applies to both spatial and temporal characteristics. The fast flickering stimulation characteristics of the multifocal electroretinogram (mfERG) can be applied to analyze retinal interactions between flashes and to investigate retinal temporal processing mechanism. Besides, its localized stimulus pattern can also be used as a tool for investigation of retinal spatial interaction. Methods: The mfERG recordings were obtained from 13 eyes of 9, normal, six-week-old Yorkshire pigs. The control mfERG was measured using the pattern consisting of 103 nonscaled hexagons, where each hexagon will follow a pre-set m-sequence. Nine isolated hexagons from the 103 nonscaled pattern were chosen in the masking mfERG stimulation, where the remaining hexagons were kept at constant luminance. First-order and the second-order kernel responses were analyzed, which represent the outer and inner retinal responses, respectively. Results: The second-order kernel response amplitude from the visual streak region showed a significant enhancement under the masking stimulation. Conclusions: The enhancement found under the masking condition indicates that the retinal signal will be suppressed under surrounding flicker stimulation, and this spatial inhibitory mechanism may originate from the inner retina.