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Distinct responses of cones and melanopsin-expressing retinal ganglion cells in the human electroretinogram.

Fukuda Y, Higuchi S, Yasukouchi A, Morita T - J Physiol Anthropol (2012)

Bottom Line: Two distinct positive peaks appeared in the mRGC response, approximately 80 msec after the onset of the stimuli and 30 msec after their offset, while no such peaks appeared in the cone response.The response to the mRGC stimulus was significantly higher than that to the cone stimulus at approximately 80 msec (P < 0.05) and tended to be higher than the cone stimulus at approximately 280 msec (P = 0.08).Implicit time of the first peak was much longer than that to the b-wave and this delay might reflect mRGC's sluggish responses.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Living Environmental Science, Fukuoka Women's University, 1-1-1, Kasumigaoka, Higashi-ku, Fukuoka 813-8529, Japan. fukuda@fwu.ac.jp

ABSTRACT

Background: The discovery of the novel photoreceptor, melanopsin-expressing retinal ganglion cells (mRGCs), has raised researchers' interest in photoreceptive tasks performed by the mRGC, especially in non-image-forming visual functions. In a prior study, we investigated the mRGC response to light stimuli independent of rods and cones with the four-primary illumination system, which modulates stimulus levels to the mRGC and cones independently, and mRGC baseline responses were recorded in the electroretinogram (ERG).

Methods: In the present study, we used the same illumination system to compare independent responses of the mRGC and cones in five subjects (mean ± SD age, 23.0 ± 1.7 years). The ERG waveforms were examined as direct measurements of responses of the mRGCs and cones to stimulation (250 msec). Implicit times (the time taken to peaks) and peak values from 30 stimuli given to each subject were analyzed.

Results: Two distinct positive peaks appeared in the mRGC response, approximately 80 msec after the onset of the stimuli and 30 msec after their offset, while no such peaks appeared in the cone response. The response to the mRGC stimulus was significantly higher than that to the cone stimulus at approximately 80 msec (P < 0.05) and tended to be higher than the cone stimulus at approximately 280 msec (P = 0.08).

Conclusions: Implicit time of the first peak was much longer than that to the b-wave and this delay might reflect mRGC's sluggish responses. This is the first report of amplitudes and implicit time in the ERG from the response of the mRGC that is independent of rods and cones, and obtained using the four-primary illumination system.

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Responses to the mRGC and cone stimuli when the masking-cone stimuli were not presented. The averaged ERG responses of five subjects are shown following stimulation of the mRGCs (black line) and the cones (gray line). Upper panels show individual responses to the mRGC stimulus (left) and the cone stimulus (right), with adjacent panels coming from the same subject. The lower panel shows the averaged response. Black arrows show peaks and troughs in response to the mRGC stimulus and white arrows show troughs in response to the cone stimulus. The temporal envelope of the test stimulus is shown by the grey line above the time-scale axis.
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Figure 4: Responses to the mRGC and cone stimuli when the masking-cone stimuli were not presented. The averaged ERG responses of five subjects are shown following stimulation of the mRGCs (black line) and the cones (gray line). Upper panels show individual responses to the mRGC stimulus (left) and the cone stimulus (right), with adjacent panels coming from the same subject. The lower panel shows the averaged response. Black arrows show peaks and troughs in response to the mRGC stimulus and white arrows show troughs in response to the cone stimulus. The temporal envelope of the test stimulus is shown by the grey line above the time-scale axis.

Mentions: Figure4 shows ERG responses of the five subjects to the mRGC stimulus (black line) and the cone stimulus (gray line) when the masking-cone stimuli were not presented. Figure5 shows ERG responses when the masking-cone stimuli were given before the test stimulus. In the case without the masking stimuli (Figure4), the averaged response to the mRGC stimulus (black line) had two peaks and two troughs. It increased after the onset of the mRGC stimulus, reached the smaller peak at approximately 75 msec (implicit time: 75 ± 9.4 msec, amplitude: 1.2 ± 0.4 μV, mean ± SD) and a trough at 120 to 180 msec; there followed a larger peak approximately 30 msec after the offset of the stimulus at approximately 280 msec (282 ± 10.4 msec, 3.6 ± 2.3 μV) and a second trough approximately 100 msec after the offset of the stimulus at approximately 350 msec. By contrast, there were no such positive peaks but only two negative troughs when the cones were stimulated (gray line); the first trough at approximately 100 msec (96 ± 9.5 msec, -2.2 ± 1.3 μV), a period of electro-neutrality between 150 and 250 msec, and a second trough approximately 65 msec after the offset of the stimulus at approximately 315 msec (316 ± 10.3 msec, -2.6 ± 0.5 μV).


Distinct responses of cones and melanopsin-expressing retinal ganglion cells in the human electroretinogram.

Fukuda Y, Higuchi S, Yasukouchi A, Morita T - J Physiol Anthropol (2012)

Responses to the mRGC and cone stimuli when the masking-cone stimuli were not presented. The averaged ERG responses of five subjects are shown following stimulation of the mRGCs (black line) and the cones (gray line). Upper panels show individual responses to the mRGC stimulus (left) and the cone stimulus (right), with adjacent panels coming from the same subject. The lower panel shows the averaged response. Black arrows show peaks and troughs in response to the mRGC stimulus and white arrows show troughs in response to the cone stimulus. The temporal envelope of the test stimulus is shown by the grey line above the time-scale axis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475092&req=5

Figure 4: Responses to the mRGC and cone stimuli when the masking-cone stimuli were not presented. The averaged ERG responses of five subjects are shown following stimulation of the mRGCs (black line) and the cones (gray line). Upper panels show individual responses to the mRGC stimulus (left) and the cone stimulus (right), with adjacent panels coming from the same subject. The lower panel shows the averaged response. Black arrows show peaks and troughs in response to the mRGC stimulus and white arrows show troughs in response to the cone stimulus. The temporal envelope of the test stimulus is shown by the grey line above the time-scale axis.
Mentions: Figure4 shows ERG responses of the five subjects to the mRGC stimulus (black line) and the cone stimulus (gray line) when the masking-cone stimuli were not presented. Figure5 shows ERG responses when the masking-cone stimuli were given before the test stimulus. In the case without the masking stimuli (Figure4), the averaged response to the mRGC stimulus (black line) had two peaks and two troughs. It increased after the onset of the mRGC stimulus, reached the smaller peak at approximately 75 msec (implicit time: 75 ± 9.4 msec, amplitude: 1.2 ± 0.4 μV, mean ± SD) and a trough at 120 to 180 msec; there followed a larger peak approximately 30 msec after the offset of the stimulus at approximately 280 msec (282 ± 10.4 msec, 3.6 ± 2.3 μV) and a second trough approximately 100 msec after the offset of the stimulus at approximately 350 msec. By contrast, there were no such positive peaks but only two negative troughs when the cones were stimulated (gray line); the first trough at approximately 100 msec (96 ± 9.5 msec, -2.2 ± 1.3 μV), a period of electro-neutrality between 150 and 250 msec, and a second trough approximately 65 msec after the offset of the stimulus at approximately 315 msec (316 ± 10.3 msec, -2.6 ± 0.5 μV).

Bottom Line: Two distinct positive peaks appeared in the mRGC response, approximately 80 msec after the onset of the stimuli and 30 msec after their offset, while no such peaks appeared in the cone response.The response to the mRGC stimulus was significantly higher than that to the cone stimulus at approximately 80 msec (P < 0.05) and tended to be higher than the cone stimulus at approximately 280 msec (P = 0.08).Implicit time of the first peak was much longer than that to the b-wave and this delay might reflect mRGC's sluggish responses.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Living Environmental Science, Fukuoka Women's University, 1-1-1, Kasumigaoka, Higashi-ku, Fukuoka 813-8529, Japan. fukuda@fwu.ac.jp

ABSTRACT

Background: The discovery of the novel photoreceptor, melanopsin-expressing retinal ganglion cells (mRGCs), has raised researchers' interest in photoreceptive tasks performed by the mRGC, especially in non-image-forming visual functions. In a prior study, we investigated the mRGC response to light stimuli independent of rods and cones with the four-primary illumination system, which modulates stimulus levels to the mRGC and cones independently, and mRGC baseline responses were recorded in the electroretinogram (ERG).

Methods: In the present study, we used the same illumination system to compare independent responses of the mRGC and cones in five subjects (mean ± SD age, 23.0 ± 1.7 years). The ERG waveforms were examined as direct measurements of responses of the mRGCs and cones to stimulation (250 msec). Implicit times (the time taken to peaks) and peak values from 30 stimuli given to each subject were analyzed.

Results: Two distinct positive peaks appeared in the mRGC response, approximately 80 msec after the onset of the stimuli and 30 msec after their offset, while no such peaks appeared in the cone response. The response to the mRGC stimulus was significantly higher than that to the cone stimulus at approximately 80 msec (P < 0.05) and tended to be higher than the cone stimulus at approximately 280 msec (P = 0.08).

Conclusions: Implicit time of the first peak was much longer than that to the b-wave and this delay might reflect mRGC's sluggish responses. This is the first report of amplitudes and implicit time in the ERG from the response of the mRGC that is independent of rods and cones, and obtained using the four-primary illumination system.

Show MeSH
Related in: MedlinePlus