Difference between revisions of "On-Off Direction-Selective Ganglion Cell/ko"

From Eyewire
Jump to: navigation, search
(Created page with "1960년대 에 행해진 초기 실험으로부터 수용장은 꽤 넓으며, 작은 변화에 민감하고, 방향 선택적 서브유닛들이 망막을 통해 여러 번...")
(Created page with "==해부학적 구조(Anatomy)==")
Line 13: Line 13:
 
1960년대 에 행해진 초기 실험으로부터 수용장은 꽤 넓으며, 작은 변화에 민감하고, 방향 선택적 서브유닛들이 망막을 통해 여러 번 반복적으로 존재한다는 것이 밝혀졌습니다.<ref name=\"barlow1965\" />
 
1960년대 에 행해진 초기 실험으로부터 수용장은 꽤 넓으며, 작은 변화에 민감하고, 방향 선택적 서브유닛들이 망막을 통해 여러 번 반복적으로 존재한다는 것이 밝혀졌습니다.<ref name=\"barlow1965\" />
  
== Anatomy ==
+
==해부학적 구조(Anatomy)==
  
 
[[Image:DSGC_overview.jpg|thumb|Left|350px|Image of an On-Off Direction-Selective Ganglion Cell<ref name="borst2011">A. Borst and T. Euler (2011). €œSeeing Things in Motion: Models, Circuits, and Mechanisms. Neuron <strong>71</strong> (6): 974-994 doi:[http://dx.doi.org/10.1016/j.neuron.2011.08.031 10.1016/j.neuron.2011.08.031]</ref>.]]
 
[[Image:DSGC_overview.jpg|thumb|Left|350px|Image of an On-Off Direction-Selective Ganglion Cell<ref name="borst2011">A. Borst and T. Euler (2011). €œSeeing Things in Motion: Models, Circuits, and Mechanisms. Neuron <strong>71</strong> (6): 974-994 doi:[http://dx.doi.org/10.1016/j.neuron.2011.08.031 10.1016/j.neuron.2011.08.031]</ref>.]]

Revision as of 03:49, 8 January 2016

아이와이어에서 재구성된 ON-OFF 방향 선택성 신경절 세포

망막에 있는 방향 선택성 세포들은 시각적 자극의 방향에 다르게 반응하는 신경세포들입니다. 이 단어는 \"자극이 수용장에서 한 방향으로 움직일 때 특히 격렬하게 신호를 발생하는” 한 무리의 신경세포를 묘사하는 데 쓰입니다[1] 생쥐의 망막에선 세 종류의 방향 선택성 세포들이 알려져 있습니다; ON/OFF 방향 선택성 신경절 세포, ON 방향 선택성 신경절 세포(밝은 자극의 이끄는 선두 가장자리에 반응) 및 OFF 방향 선택성 신경절 세포(밝은 자극의 끌리는 꼬리 부분에만 반응)입니다. 각각의 세포는 독특한 생리 및 해부학적 구조를 갖고 있습니다.[2] 이 페이지의 나머지 부분의 내용은 ON/OFF 방향 선택성 신경절 세포에만 해당되는 내용입니다.

생리(Physiology)

반응이 없는 방향과 선호하는 방향에서 자극에 대해 ON/OFF 방향 선택성 신경절 세포가 반응하는 것을 보여주는 모식도. 입력신호는 선호하는 방향에서는 배가되고 반응이 없는 방향에서는 억제됩니다.[3]

ON/OFF방향 선택성 신경절 세포는 국소적인 움직임 탐지기의 역할을 합니다. 만일 밝은 자극(예를 들어 빛)이 세포가 선호하는 방향으로 움직이면 세포는 이끄는 선두 가장자리와 끌리는 꼬리 쪽 가장자리 모두 에서 신호를 발사합니다. 중요한 대비로써, 밝은 자극이 선호 방향의 반대 방향(반응이 없는 방향)으로 움직이는 경우 매우 적거나 반응이 아예 없게 됩니다.Cite error: Invalid <ref> tag; refs with no content must have a name 자극에 대한 반응은 크기, 모양, 색깔, 속도 등과 같은 자극의 여러 가지 성질들로부터 독립적입니다. 이들 세포들은 중심-주변 구조를 가지고 있으며 수상돌기의 크기는 중심 수용장의 크기와 관련이 있습니다.Cite error: Invalid <ref> tag; refs with no content must have a name

ON/OFF 방향 선택성 신경절 세포는 방향 선호의 차이에 따라 4개 군으로 분류할 수 있으며 배, 등, 코, 측두(ventral, dorsal, nasal, temporal)입니다. 다른 군의 세포들은 수지돌기 구조도 다르며 두뇌에서 시냅스의 표적도 다릅니다.Cite error: Invalid <ref> tag; refs with no content must have a name

1960년대 에 행해진 초기 실험으로부터 수용장은 꽤 넓으며, 작은 변화에 민감하고, 방향 선택적 서브유닛들이 망막을 통해 여러 번 반복적으로 존재한다는 것이 밝혀졌습니다.Cite error: Invalid <ref> tag; refs with no content must have a name

해부학적 구조(Anatomy)

Error creating thumbnail: Unable to save thumbnail to destination
Image of an On-Off Direction-Selective Ganglion Cell[4].

The ON/OFF DSGCs are commonly recognized by their bistratified dendritic arbors, which extend to two layers of the inner plexiform layer (IPL). These cell types are also known to synapse with both bipolar cells and starburst amacrine cells (SAC). As described above, there are four cell subtypes, each with own preference for direction. Each subtype of ON/OFF DSGCs has differences in dendritic patterns and axonal projections to the brain. These differences indicate that outputs from different subtypes may wire to different parts of the brain [5]

Depiction of six reconstructed ON/OFFDSGCs. Figure A shows the bistratification of the ON and OFF arbors. Colors correspond to orientation of preferred direction. Figure B shows a bottom view of the traced arbors.[6]

Connections

Excitation comes from both bipolar cells and starburst amacrine cells.[4] The main source of inhibition is from starburst amacrine cells. Using manual reconstruction of 6 ON/OFF DSGCs and their synaptic partners, it was found that over 90% of SAC – ON/OFF DSGC synapses were oriented in the null direction.[6]

As illustrated in the accompanying figure, light enters the retina through the photoreceptors, and excitatory inputs are transmitted to the ON/OFF DSGCs via Glutamate and Acetylcholine from the bipolar and starburst amacrine cells. Inhibitory GABA inputs, which are crucial for suppressing information in the null direction (and thereby creating a direction-selective motion detector) are received from SACs. The motion detection result is fed to higher parts of the brain for further processing.

Error creating thumbnail: Unable to save thumbnail to destination
Depiction of the circuitry surrounding a ON/OFF DSGC [4]
Error creating thumbnail: Unable to save thumbnail to destination
Figure showing how ON/OFF DSGCs can be distinguished from other RGCs. As described in the text, this is accomplished using CART; a careful morphological analysis confirms that this marker correctly identifies the ON/OFF DSGCs with no false positives. [5]

Molecules

As described above, ON/OFF DS ganglion cells can be divided into 4 subtypes differing in their directional preference, ventral, dorsal, nasal, or temporal. Recent research has identified markers for distinguishing between the different subtypes, and for separating ON/OFF DSGCs from other retinal ganglion cells. These markers are independent of experience, and suggest a method for how these cells obtain different inputs.

Recent research has lead to the development of transgenic mouse lines that selectively mark ON/OFF DSGCs that prefer ventral or nasal motion and another line that marks ventral and dorsal preferring DSGCs. These lines were used to identify cell surface molecules (including Cadherin 6, CollagenXXV1, and Matrix metalloprotease 17), that allow each of the four types of ON/OFF DSGCs to be differentiated. A neuropeptide, CART (cocaine and amphetamine regulated transcript) has been found to differentiate ON/OFF DSGCs from all other retinal ganglion cells. Strikingly, these patterns of molecular differentiation occur before animal eye-opening, and demonstrate that these differences are experience-independent. Therefore, the molecular differences may help to explain the differing functionality between subtypes. [5]

Models

The firing pattern of On-Off Direction-Selective Ganglion cells is time-dependent and is supported by the Reichardt- Hassenstain model, which detects spatiotemporal correlation between two adjacent cells [7].

File:Reichardt model.jpg
Graphic explaining the Reichardt-Hassenstain model [7]

As applied to the visual system, this model considers the processed stimulus(i.e., light) inputs to two adjacent cells. After a time delay, each delayed input is multiplied by the original signal from the other cell. The resulting signals are subtracted, and the positive outcome indicates the preferred direction [7].

This behavior was validated in the visual system using calcium imaging in the fly [8]. However, this model correspondence has only been completed at a high-level (input-output), rather than at an anatomical or physiological level.[4]

History

Direction Selective units were first explored in cats by Hubel and Wiesel in 1959. Levick and Barlow performed many of the seminal early experiments related to direction selectivity during the 1960s using rabbit retina [9]. In these experiments, they measured action potentials generated from a black-white grating with a small slit [7]. Many additional experiments have been performed during the past fifty years in organisms as diverse as the turtle (e.g., Marchiafava 1979) and the mouse (Briggman 2011).

References

  1. H. B. Barlow and W. R. Levick (1965) The Mechanism of Directionally Selective Units in Rabbit's Retina J. Physiol. 178: 477-504
  2. \"Motion Sensing in Vision.\" Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/wiki/Motion_Sensing_in_Vision (Accessed April 02, 2012).
  3. D. I. Vaney, B. Sivyer, and W. R. Taylor (2012). Direction selectivity in the retina: symmetry and asymmetry in structure and function. Nature Neuroscience 13 (3): 194-208
  4. 4.0 4.1 4.2 4.3 A. Borst and T. Euler (2011). €œSeeing Things in Motion: Models, Circuits, and Mechanisms. Neuron 71 (6): 974-994 doi:10.1016/j.neuron.2011.08.031
  5. 5.0 5.1 5.2 J. N. Kay et al. (2011) Retinal ganglion cells with distinct directional preferences differ in molecular identity, structure, and central projections. J. Neurosci. 31 (21): 7753-7762 doi: 10.1523/​JNEUROSCI.0907-11.2011
  6. 6.0 6.1 K. L. Briggman, M. Helmstaedter, and W. Denk (2011). Wiring specificity in the direction-selectivity circuit of the retina Nature 471: 183–188
  7. Cite error: Invalid <ref> tag; no text was provided for refs named wiki
  8. J. Haag (2004). €œFly Motion Vision Is Based on Reichardt Detectors Regardless of the Signal-to-noise Ratio. Proc. Natl. Acad. Sci. 101 (46): 16333-16338 doi: 10.1073/pnas.0407368101
  9. Cite error: Invalid <ref> tag; no text was provided for refs named barlow1965