NEURAL CIRCUIT TUNING FLY VISUAL INTERNEURONS TO MOTION OF SMALL OBJECTS .1. DISSECTION OF THE CIRCUIT BY PHARMACOLOGICAL AND PHOTOINACTIVATION TECHNIQUES
NEURAL CIRCUIT TUNING FLY VISUAL INTERNEURONS TO MOTION OF SMALL OBJECTS .1. DISSECTION OF THE CIRCUIT BY PHARMACOLOGICAL AND PHOTOINACTIVATION TECHNIQUES
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DOI：
10.1152/jn.1993.69.2.329
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发表时间：
1993-02-01
影响因子：
2.5
通讯作者：
BORST, A
中科院分区：
文献类型：
--
作者：
WARZECHA, AK;EGELHAAF, M;BORST, A
1.在许多动物物种中发现了对小物体运动调谐的视觉中间神经元，并且被认为是通过相对运动进行图形-背景辨别的神经元基础。一个经过充分研究的例子是绿头苍蝇第三视觉神经元中的FD 1细胞。这种细胞类型对小物体的运动反应最好。扩展模式的运动只产生微小的响应。作为导致这种反应特征的神经元机制，有人提出，FD 1-细胞被两种推测为GABA能的，因此是抑制性CH-细胞，VCH-和DCH-细胞抑制。CH-细胞对FD 1-细胞活性降低的运动类型反应最好。CH-细胞抑制FD 1-细胞，从而介导其对小的移动物体的选择性的假设通过烧蚀CH-细胞来测试，无论是直接烧蚀还是光灭活。在应用γ-氨基丁酸（GABA）拮抗剂苦毒素后，FD 1细胞对大场运动的反应比对小场运动的反应更强烈，即，它已经失去了小领域的选择性。这表明FD 1细胞对微小运动物体的调节依赖于GABA能机制，因此最有可能依赖于CH细胞。每个CH-细胞的小场调谐的作用是通过单独灭活它们来确定的。他们被注入荧光染料，然后用激光照射消融。只有光灭活的VCH-细胞消除了特定的选择性的FD 1-细胞的小场运动。消融的DCH-细胞没有显着改变的FD 1-细胞的响应特性。这揭示了VCH细胞在介导FD 1细胞对小物体运动的特征敏感性中的重要作用. FD 1细胞对同侧视野腹侧部分的小物体运动最敏感，而背侧部分的运动对细胞的影响很弱。这一特定特征与VCH细胞对同侧运动的敏感性非常吻合，这在视野的腹侧部分最为明显。FD 1细胞的空间敏感性分布也与图形-背景辨别和注视行为的特征相匹配。
1. Visual interneurons tuned to the motion of small objects are found in many animal species and are assumed to be the neuronal basis of figure-ground discrimination by relative motion. A well-examined example is the FD1-cell in the third visual neuropil of blowflies. This cell type responds best to motion of small objects. Motion of extended patterns elicits only small responses. As a neuronal mechanism that leads to such a response characteristic, it was proposed that the FD1-cell is inhibited by the two presumably GABAergic and, thus, inhibitory CH-cells, the VCH- and the DCH-cell. The CH-cells respond best to exactly that type of motion by which the activity of the FD1-cell is reduced. The hypothesis that the CH-cells inhibit the FD1-cell and, thus, mediate its selectivity to small moving objects was tested by ablating the CH-cells either pharmacologically or by photoinactivation.2. After application of the gamma-aminobutyric acid (GABA) antagonist picrotoxinin, the FD1-cell responds more strongly to large-field than to small-field motion, i.e., it has lost its small-field selectivity. This suggests that the tuning of the FD1-cell to small moving objects relies on a GABAergic mechanism and, thus, most likely on the CH-cells.3. The role of each CH-cell for small-field tuning was determined by inactivating them individually. They were injected with a fluorescent dye and then ablated by laser illumination. Only photoinactivation of the VCH-cell eliminated the specific selectivity of the FD1-cell for small-field motion. Ablation of the DCH-cell did not significantly change the response characteristic of the FD1-cell. This reveals the important role of the VCH-cells in mediating the characteristic sensitivity of the FD1-cell to motion of small objects.4. The FD1-cell is most sensitive to motion of small objects in the ventral part of the ipsilateral visual field, whereas motion in the dorsal part influences the cell only weakly. This specific feature fits well to the sensitivity of the VCH-cell to ipsilateral motion that is most pronounced in the ventral part of the visual field. The spatial sensitivity distribution of the FD1-cell matches also the characteristics of figure-ground discrimination and fixation behavior.