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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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Comparison of response latencies of TACs to spot and annulus irradiation, as restricted to responses of similar amplitude (±10% of average in each set). (A) Independence of response latencies of spot size. The latency was determined as the time from the stimulus onset or offset to the first response peak. The response latency was essentially the same for different spot diameters. (B) Dependence on the inner diameter of the annuli, ranging from 0 to 3 mm. The response latency increased with diameter. The data at diameter 0 were those responses to spots from A, fulfilling the amplitude criterion. The outer diameter was 12 mm in all cases.
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fig2: Comparison of response latencies of TACs to spot and annulus irradiation, as restricted to responses of similar amplitude (±10% of average in each set). (A) Independence of response latencies of spot size. The latency was determined as the time from the stimulus onset or offset to the first response peak. The response latency was essentially the same for different spot diameters. (B) Dependence on the inner diameter of the annuli, ranging from 0 to 3 mm. The response latency increased with diameter. The data at diameter 0 were those responses to spots from A, fulfilling the amplitude criterion. The outer diameter was 12 mm in all cases.

Mentions: The latencies to spot stimuli did not change with spot diameter, as shown in Fig. 2 A. The average latency of On-responses was 59 ± 4 ms (n = 31), indistinguishable from the Off-response latencies (53 ± 3 ms, n = 31). The latency of responses to annuli, however, increased with the inner diameter of the annulus (Fig. 2 B). The conduction velocity was determined by the ratio between the difference of inner radii of the two annular light stimuli and the time difference of the response peak latencies. The obtained conduction velocities were 114 ± 23 mm/s for On- and 108 ± 21 mm/s (n = 26) for Off-responses, as shown in Table I .


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

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

Comparison of response latencies of TACs to spot and annulus irradiation, as restricted to responses of similar amplitude (±10% of average in each set). (A) Independence of response latencies of spot size. The latency was determined as the time from the stimulus onset or offset to the first response peak. The response latency was essentially the same for different spot diameters. (B) Dependence on the inner diameter of the annuli, ranging from 0 to 3 mm. The response latency increased with diameter. The data at diameter 0 were those responses to spots from A, fulfilling the amplitude criterion. The outer diameter was 12 mm in all cases.
© Copyright Policy
Related In: Results  -  Collection

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

fig2: Comparison of response latencies of TACs to spot and annulus irradiation, as restricted to responses of similar amplitude (±10% of average in each set). (A) Independence of response latencies of spot size. The latency was determined as the time from the stimulus onset or offset to the first response peak. The response latency was essentially the same for different spot diameters. (B) Dependence on the inner diameter of the annuli, ranging from 0 to 3 mm. The response latency increased with diameter. The data at diameter 0 were those responses to spots from A, fulfilling the amplitude criterion. The outer diameter was 12 mm in all cases.
Mentions: The latencies to spot stimuli did not change with spot diameter, as shown in Fig. 2 A. The average latency of On-responses was 59 ± 4 ms (n = 31), indistinguishable from the Off-response latencies (53 ± 3 ms, n = 31). The latency of responses to annuli, however, increased with the inner diameter of the annulus (Fig. 2 B). The conduction velocity was determined by the ratio between the difference of inner radii of the two annular light stimuli and the time difference of the response peak latencies. The obtained conduction velocities were 114 ± 23 mm/s for On- and 108 ± 21 mm/s (n = 26) for Off-responses, as shown in Table I .

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