Intracellular processing of motion information in a network of blowfly visual interneurons [Elektronische Ressource] / vorgelegt von Yishai Michael Elyada

Yishai Elyada

Sujets

• Biologie

Informations

• Publié par: ludwig-maximilians-universitat_munchen
• Publié le: 01 janvier 2009
• Nombre de lectures: 31
• Langue: Deutsch
• Poids de l'ouvrage: 4 Mo

Extrait

Intracellular processing of motion
information in a network of blowfly
visual interneurons

Yishai Michael Elyada

München 2009

Intracellular processing of motion
information in a network of blowfly
visual interneurons

Dissertation
Zur Erlangung des Doktorgrades
der Naturwissenschaften (Dr.rer.nat.)
der Fakultät für Biologie
der Ludwig-Maximilians-Universität München

Angefertigt am Max-Planck-Institüt für Neurobiologie,
Abteilung ’Neuronale Informationsverarbeitung’


Vorgelegt von
Yishai Michael Elyada

München 2009

Hiermit erkläre ich, daß ich die vorliegende Dissertation selbständig und ohne
unerlaubte Hilfe angefertigt habe. Sämtliche Experimente wurden von mir selbst
durchgeführt, außer wenn explizit auf Dritte verwiesen wird. Ich habe weder anderweitig
versucht, eine Dissertation oder Teile einer Dissertation einzureichen bzw. einer
Prüfungskommission vorzulegen, noch eine Doktorprüfung durchzuführen.

München, den





















1. Gutachter: Dr. Alexander Borst
2. Gutachter: Dr. Benedikt Grothe
Tag der mündlichen Prüfung: Dienstag, den 14. 07.2009


Contents
Abstract ................................................................................................................. 9
Chapter 1. Introduction ......... 11
1.1. Visual orientation in flight ........................................................................ 11
1.1.1. Optic flow and the optomotor response ..................... 12
1.2. Local motion detection ............. 16
1.2.1. The Reichardt detector ................................................................................ 17
1.2.2. Evidence in insects ....................... 18
1.2.3. Response properties .................... 20
1.3. The fly visual system ................................................................................ 22
1.3.1. The compound eye ....................... 23
1.3.2. The lamina .................................................................................................... 27
1.3.3. The medulla .. 29
1.3.4. The lobula ..... 31
1.3.5. The lobula plate............................................................................................ 31
1.4. Lobula plate tangential cells ..................................... 34
1.4.1. Lobula plate tangential cells and optic flow integration ............................. 34
1.4.2. HS cells ......................................................................... 38
1.4.3. CH cells ......................................... 39
1.4.4. FD cells (CI cells) ........................................................................................... 40
1.4.5. Bilateral spiking cells – H cells and V cells .................... 41
1.4.6. VS cells .......................................................................................................... 43
1.4.7. Calcium responses ........................ 45
1.5. Lateral interactions between VS cells................................ 47
1.5.1. Axo-axonal gap junctions ............................................. 48
1.5.2. Functional significance ................................................. 49
1.6. Neuronal morphology and intracellular computation 51


1.6.1. Segregation and aggregation of inputs ........................................................ 51
1.6.2. Non-linear integration in LPTC dendrites .................... 54
1.7. Goals and project outline ......................................................................... 55
Chapter 2. Methods .............................................. 57
2.1. Experiments ............................................................. 57
2.1.1. Preparation and positioning of the flies ...................... 57
2.1.2. Electrophysiology ......................................................... 59
2.1.3. Visual stimulation ................................ 61
2.1.4. Electrical responses ...................... 62
2.2. Data analysis ............................................................ 63
2.2.1. Cell identification ......................................................... 63
2.2.2. Calcium imaging ........................... 64
2.3. Modeling.................................................................................................. 66
2.3.1. VS cell network model ................. 66
2.3.2. Model parameters ....................................................................................... 69
2.3.3. Modeling visual input ................... 70
2.3.4. Modeling calcium responses ........................................................................ 71
Chapter 3. Results ................................................. 72
3.1. Two receptive fields in single VS cells ....................................................... 73
3.1.1. Linearity and homogeneity of calcium responses ....................................... 73
3.1.2. Mapping the receptive fields ....................................... 74
3.2. Information flow underlying receptive field broadening ........................... 77
3.2.1. Controlling information flow with voltage clamp ........................................ 78
3.2.1. Clamping out dendritic input to the axon terminal ..... 80
3.3. Interpolation of dendritic signals in the terminals ..... 83
3.3.1. Faster reporting of calcium dynamics .......................................................... 83
3.3.2. Frequency response and SNR of the calcium dye ........................................ 85
3.3.3. Smoothing of dendritic fluctuations in the axon terminal........................... 87
3.4. Functional consequences .......................................... 88
3.4.1. Compartmental model ................................................. 89
3.4.2. Quantifying response smoothness .............................................................. 90
3.4.3. The shunting effect of chemical synapses ................... 92
3.5. Small field selectivity of VS cell dendrites ................. 95
Chapter 4. Discussion .......................................................................... 100
4.1. Methodology ......................... 100
4.1.1. Calcium imaging 101
4.1.2. Single electrode voltage clamp .................................................................. 104
4.1.3. Local voltage clamp as a tool ..... 105
4.1.4. The effects of dendritic voltage clamp in VS cells ...... 106
4.2. Relation to previous results .................................................................... 107
4.2.1. Receptive field broadening in VS cells ....................... 107
4.2.2. Information flow in the lobula plate .......................................................... 108
4.3. Broad receptive fields and population coding ......... 112
4.3.1. Noise correlations ...................................................... 113
4.3.2. Stimulus dimension .................................................... 114
4.3.3. Relevance to the VS cell network............................... 116
4.4. Gap junctions ......................................................................................... 117
4.5. Separating VS cell input sources ............................. 119
4.5.1. Linear and non-linear integration .............................. 120
4.6. Small field selectivity of VS cell dendrites ............................................... 121




List of Figures
Figure 1-1: Optic flow fields for different flight maneuvers. ............................................ 16
Figure 1-2: The Reichardt detector. .................................................. 18
Figure 1-3: Schematic overview of the fly visual system 24
Figure 1-4: The fly retina – morphology and light responses ........................................... 25
Figure 1-5: The two motion detection pathways in the lamina ....... 28
Figure 1-6: Lobula plate tangential cells ........................................... 37
Figure 1-7: VS cells and their receptive fields ................................... 45
Figure 1-8: Single neurons as dual layer neural networks ................ 53
Figure 1-9: Narrow dendritic and broad axonal receptive fields in single VS cells .......... 57
Figure 2-1: Access to the lobula plate and the LPTCs. ...................................................... 59
Figure 2-2: Identification of a VS4 cell by the relative position of its main dendrite. ...... 64
Figure 2-3: Calculating the region of interest (ROI). ......................... 65
Figure 2-4: Normalizing calcium imaging receptive fields. ............................................... 66
Figure 2-5: VS network models used for simulations. ...................... 68
Figure 3-1: Current-calcium influx relationship in VS cell dendrites and axons ............... 75
Figure 3-2: Broadening of VS cells’ receptive fields within single cells. ........................... 76
Figure 3-3: Broadening of VS cells’ receptive fields – population analysis. ..................... 77
Figure 3-4: No broadening of rece