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Asymmetric temporal properties in the receptive field of retinal transient amacrine cells.

Djupsund K, Furukawa T, Yasui S, Yamada M - J. Gen. Physiol. (2003)

Bottom Line: The fastest speeds were found in the dorsal area of the receptive fields, on average five times faster than those detected within the ventral area.Based on these results, we modeled the velocity asymmetry and the displacement of amplitude center by adding a contribution of an asymmetric polyaxonal inhibition to the network.Due to the asymmetry in the conduction velocity, the time delay of a light response is proposed to depend on the origin of the photostimulus movement, a potentially important mechanism underlying direction selectivity within the inner retina.

View Article: PubMed Central - PubMed

Affiliation: Department of Production, Information, and Systems Engineering, Tokyo Metropolitan Institute of Technology, 6-6, Asahigaoka, Hino, Tokyo 191-0065, Japan.

ABSTRACT
The speed of signal conduction is a factor determining the temporal properties of individual neurons and neuronal networks. We observed very different conduction velocities within the receptive field of fast-type On-Off transient amacrine cells in carp retina cells, which are tightly coupled to each other via gap junctions. The fastest speeds were found in the dorsal area of the receptive fields, on average five times faster than those detected within the ventral area. The asymmetry was similar in the On- and Off-part of the responses, thus being independent of the pathway, pointing to the existence of a functional mechanism within the recorded cells themselves. Nonetheless, the spatial decay of the graded-voltage photoresponse within the receptive field was found to be symmetrical, with the amplitude center of the receptive field being displaced to the faster side from the minimum-latency location. A sample of the orientation of varicosity-laden polyaxons in neurobiotin-injected cells supported the model, revealing that approximately 75% of these processes were directed dorsally from the origin cells. Based on these results, we modeled the velocity asymmetry and the displacement of amplitude center by adding a contribution of an asymmetric polyaxonal inhibition to the network. Due to the asymmetry in the conduction velocity, the time delay of a light response is proposed to depend on the origin of the photostimulus movement, a potentially important mechanism underlying direction selectivity within the inner retina.

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A comparison of the locations of the latency center and the amplitude center of a TAC. Squares, response latency; circles, amplitude (On-responses). Left y-axis, amplitude. Right y-axis, latency. Space constants on the left and right side of receptive field were 1.08 and 1.13 mm. Conduction velocities in the left and right side of receptive field were 13 and 28 mm/s, respectively. Before fitting, the amplitudes were averaged with 3- or 5-point adjacent averaging. The location of the latency center was determined by the intersection of the regression lines for the conduction velocity. The center of the amplitude was similarly determined by the intersection of the regression lines for the fit by the exponential decay function. For this cell, a displacement of ∼200 μm between these two centers could be seen.
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fig7: A comparison of the locations of the latency center and the amplitude center of a TAC. Squares, response latency; circles, amplitude (On-responses). Left y-axis, amplitude. Right y-axis, latency. Space constants on the left and right side of receptive field were 1.08 and 1.13 mm. Conduction velocities in the left and right side of receptive field were 13 and 28 mm/s, respectively. Before fitting, the amplitudes were averaged with 3- or 5-point adjacent averaging. The location of the latency center was determined by the intersection of the regression lines for the conduction velocity. The center of the amplitude was similarly determined by the intersection of the regression lines for the fit by the exponential decay function. For this cell, a displacement of ∼200 μm between these two centers could be seen.

Mentions: We could determine the receptive field center for both the latency and amplitude profiles. The faster halves were longer than the slower halves, on average by 370 μm (n = 24), as shown in the example in Fig. 7 . When we superimposed the field centers, the location of the latency center was on average displaced 185 μm toward the slower half of the receptive field. The displacement between the location of the amplitude center and the latency center was close to 200 μm, as shown in Table II .


Asymmetric temporal properties in the receptive field of retinal transient amacrine cells.

Djupsund K, Furukawa T, Yasui S, Yamada M - J. Gen. Physiol. (2003)

A comparison of the locations of the latency center and the amplitude center of a TAC. Squares, response latency; circles, amplitude (On-responses). Left y-axis, amplitude. Right y-axis, latency. Space constants on the left and right side of receptive field were 1.08 and 1.13 mm. Conduction velocities in the left and right side of receptive field were 13 and 28 mm/s, respectively. Before fitting, the amplitudes were averaged with 3- or 5-point adjacent averaging. The location of the latency center was determined by the intersection of the regression lines for the conduction velocity. The center of the amplitude was similarly determined by the intersection of the regression lines for the fit by the exponential decay function. For this cell, a displacement of ∼200 μm between these two centers could be seen.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2233775&req=5

fig7: A comparison of the locations of the latency center and the amplitude center of a TAC. Squares, response latency; circles, amplitude (On-responses). Left y-axis, amplitude. Right y-axis, latency. Space constants on the left and right side of receptive field were 1.08 and 1.13 mm. Conduction velocities in the left and right side of receptive field were 13 and 28 mm/s, respectively. Before fitting, the amplitudes were averaged with 3- or 5-point adjacent averaging. The location of the latency center was determined by the intersection of the regression lines for the conduction velocity. The center of the amplitude was similarly determined by the intersection of the regression lines for the fit by the exponential decay function. For this cell, a displacement of ∼200 μm between these two centers could be seen.
Mentions: We could determine the receptive field center for both the latency and amplitude profiles. The faster halves were longer than the slower halves, on average by 370 μm (n = 24), as shown in the example in Fig. 7 . When we superimposed the field centers, the location of the latency center was on average displaced 185 μm toward the slower half of the receptive field. The displacement between the location of the amplitude center and the latency center was close to 200 μm, as shown in Table II .

Bottom Line: The fastest speeds were found in the dorsal area of the receptive fields, on average five times faster than those detected within the ventral area.Based on these results, we modeled the velocity asymmetry and the displacement of amplitude center by adding a contribution of an asymmetric polyaxonal inhibition to the network.Due to the asymmetry in the conduction velocity, the time delay of a light response is proposed to depend on the origin of the photostimulus movement, a potentially important mechanism underlying direction selectivity within the inner retina.

View Article: PubMed Central - PubMed

Affiliation: Department of Production, Information, and Systems Engineering, Tokyo Metropolitan Institute of Technology, 6-6, Asahigaoka, Hino, Tokyo 191-0065, Japan.

ABSTRACT
The speed of signal conduction is a factor determining the temporal properties of individual neurons and neuronal networks. We observed very different conduction velocities within the receptive field of fast-type On-Off transient amacrine cells in carp retina cells, which are tightly coupled to each other via gap junctions. The fastest speeds were found in the dorsal area of the receptive fields, on average five times faster than those detected within the ventral area. The asymmetry was similar in the On- and Off-part of the responses, thus being independent of the pathway, pointing to the existence of a functional mechanism within the recorded cells themselves. Nonetheless, the spatial decay of the graded-voltage photoresponse within the receptive field was found to be symmetrical, with the amplitude center of the receptive field being displaced to the faster side from the minimum-latency location. A sample of the orientation of varicosity-laden polyaxons in neurobiotin-injected cells supported the model, revealing that approximately 75% of these processes were directed dorsally from the origin cells. Based on these results, we modeled the velocity asymmetry and the displacement of amplitude center by adding a contribution of an asymmetric polyaxonal inhibition to the network. Due to the asymmetry in the conduction velocity, the time delay of a light response is proposed to depend on the origin of the photostimulus movement, a potentially important mechanism underlying direction selectivity within the inner retina.

Show MeSH
Related in: MedlinePlus