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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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Protocols for presenting light stimuli (including test stimuli and masking-cone stimuli). (a) An mRGC stimulus with masking stimuli flickering with contrast of ±0.30 modulation at 20 Hz. The stimulus to the mRGC varied from background (B) to high (H) with contrast of +0.50 modulation for 250 msec. (b) A cone stimulus with the masking stimuli. The stimulus to the cone varied from background (B) to high (H) with contrast of +0.30 modulation. Each measurement was repeated 30 times.
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Figure 2: Protocols for presenting light stimuli (including test stimuli and masking-cone stimuli). (a) An mRGC stimulus with masking stimuli flickering with contrast of ±0.30 modulation at 20 Hz. The stimulus to the mRGC varied from background (B) to high (H) with contrast of +0.50 modulation for 250 msec. (b) A cone stimulus with the masking stimuli. The stimulus to the cone varied from background (B) to high (H) with contrast of +0.30 modulation. Each measurement was repeated 30 times.

Mentions: Figure2 shows the protocol for presenting the light stimuli with masking-cone stimuli. Panel (a) shows an mRGC stimulus with masking-cone stimuli. Panel (b) shows a cone stimulus with the masking stimuli and a constant mRGC stimulus. Each trial consisted of 2,000-msec presentation of the masking stimuli, 100-msec presentation of background (B) stimulus levels, and presentation of a test stimulus for 250 msec. The masking stimuli were presented at 20 Hz as square waves with a Michelson contrast of 0.30. At a high temporal frequency of 20 Hz, sensitivity of the cone is higher than that of the mRGC, as response latency to light is 30 to 40 msec for the cones and 900 msec for those mRGCs which do not receive input from the rods or cones [8]. Therefore, it was expected that the masking-cone stimulus would efficiently stimulate the cone components in the ERG responses. The masking stimulus modulated L, M and S cones with no change in mRGC excitation. This temporally flickering mask can selectively suppress the cone-mediated pathways since it is modulated only in L, M and S cones.


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)

Protocols for presenting light stimuli (including test stimuli and masking-cone stimuli). (a) An mRGC stimulus with masking stimuli flickering with contrast of ±0.30 modulation at 20 Hz. The stimulus to the mRGC varied from background (B) to high (H) with contrast of +0.50 modulation for 250 msec. (b) A cone stimulus with the masking stimuli. The stimulus to the cone varied from background (B) to high (H) with contrast of +0.30 modulation. Each measurement was repeated 30 times.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Protocols for presenting light stimuli (including test stimuli and masking-cone stimuli). (a) An mRGC stimulus with masking stimuli flickering with contrast of ±0.30 modulation at 20 Hz. The stimulus to the mRGC varied from background (B) to high (H) with contrast of +0.50 modulation for 250 msec. (b) A cone stimulus with the masking stimuli. The stimulus to the cone varied from background (B) to high (H) with contrast of +0.30 modulation. Each measurement was repeated 30 times.
Mentions: Figure2 shows the protocol for presenting the light stimuli with masking-cone stimuli. Panel (a) shows an mRGC stimulus with masking-cone stimuli. Panel (b) shows a cone stimulus with the masking stimuli and a constant mRGC stimulus. Each trial consisted of 2,000-msec presentation of the masking stimuli, 100-msec presentation of background (B) stimulus levels, and presentation of a test stimulus for 250 msec. The masking stimuli were presented at 20 Hz as square waves with a Michelson contrast of 0.30. At a high temporal frequency of 20 Hz, sensitivity of the cone is higher than that of the mRGC, as response latency to light is 30 to 40 msec for the cones and 900 msec for those mRGCs which do not receive input from the rods or cones [8]. Therefore, it was expected that the masking-cone stimulus would efficiently stimulate the cone components in the ERG responses. The masking stimulus modulated L, M and S cones with no change in mRGC excitation. This temporally flickering mask can selectively suppress the cone-mediated pathways since it is modulated only in L, M and S cones.

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