Parallel pathways in the retina

Transcription

1 Retinal origins of parallel pathways in the primate visual system Wednesday, September 23, 2015 Sherry, Parallel pathways in the retina Several different images of the outside world are sent simultaneously via parallel pathways from the eye to the brain. These lectures on functional retinal circuitry describe how this parallel processing starts at the first synapses in the retina between photoreceptors and bipolar cells, and how it is maintained, refined and embellished through the retinal circuits. Major resource for figures and additional information: 2 1

2 Introduction: Parallel pathways through the retina and into the central visual pathways Fall Nassi & Calloway,

3 Parallel pathways to the brain Parietal/Dorsal: Where Temporal/Ventral What Includes K-cell projections Koniocellular--- K 5 Berson, 2003 Another type of retinal ganglion cell (RGC): intrinsically photosensitive (iprgc or melanopsin cell) iprgcs predominantly project to non-visual brain regions such as the superchiasmatic nucleus (SCN) and the olivary pretectal nucleus (OPN) (pupil light reflex) 6 3

4 Functions of the retina Transduction of light to neural signals - Fox lectures Adaptation and adjustment of sensitivity later lectures Functions due to regional specializations Fovea (high acuity) Peripheral retina (high sensitivity) Functions due to specialized circuitry Rod and cone circuits Parallel pathways (to On and OFF midget, parasol and bistratified ganglion cells) 7 Range of Visual Sensitivity: Scotopic, Mesopic, Photopic (Rod) (Cone) 8 4

5 Topics for today Vertical and horizontal organization of the retina: 5 major types of neurons, and Müller cells The key role played by bipolar cells in setting up the parallel pathways through the retina Types of bipolar cells morphology & contacts Functional properties of bipolar cells The role of specific types of glutamate receptors Effects of horizontal cell feedback The terminations of bipolar cells in the IPL synapses with amacrine and ganglion cells 9 Vertical organization of the retina RPE ROS ONL RIS OPL INL IPL GCL NFL (RFNL) 10 5

6 Vertical organization of the retina tissue section 11 Retina: Flat mount Dacey, J. Neurosci,

7 Fovea Optic nerve head 13 Lateral (horizontal) organization of the macula Adler, 8 th Edition 14 7

8 Rod and cone densities along the horizontal meridian 15 Cone densities are highest in the fovea Slide 16 8

9 Retinal ganglion cell densities are also greatest in the central retina (macaque monkey) 17 Horizontal organization and cell types 18 9

10 19 Baboon retina at 3 eccentricities Foveal slope Parafoveal 30 deg nasal Krebs & Krebs 20 10

11 Effect of retinal eccentricity on acuity Stuart Anstis 21 Cell types 22 11

12 Photoreceptor outer segments 23 Photoreceptors of primates that are trichromats: humans and monkeys 24 12

13 Spectral Sensitivity Melanopsin receptor in giant retinal ganglion cells peaks at 482 nm Dacey et al., Nature Roorda & Williams,

14 Foveal region of retina Peripheral retina 27 Human foveal development Hendrickson 28 14

15 Horizontal cells 29 Bipolar cells ON cone bipolar cell OFF cone BC Rod bipolar cell 30 15

16 Bipolar cells of the retina: initiation of parallel pathways 31 Bipolar cells of the retina On cone bipolar cells Rod bipolar cells 32 16

17 Amacrine cells

18 A17 Amacrine cells 35 Human retinal ganglion cells melanopsin Webvision 36 18

19 Retinal ganglion cells: midget, parasol, small bistratified (a small population of giant melanopsin cells included in inset) 37 Topics for today Vertical and horizontal organization of the retina: 5 major types of neurons, and Mueller cells The key role played by bipolar cells in setting up the parallel pathways through the retina Types of bipolar cells morphology & contacts Functional properties of bipolar cells The role of specific types of glutamate receptors Effects of horizontal cell feedback The terminations of bipolar cells in the IPL synapses with amacrine and ganglion cells 38 19

20 Bipolar cells of the retina: the beginning of parallel pathways Boycott & Waessle 39 Synaptic organization: OPL Cone pedicle Rod spherule Triad: ribbon synapse Flat contacts Dowling, Boycott

21 On and Off pathways 41 Vertical organization of the retina -OPL 42 21

22 Synaptic organization: OPL Webvision 43 Tiger Salamander/Mudpuppy big retinal neurons early single cell recordings (Werblin & Dowling, 1968) 44 22

23 Sensory receptive field "area in which stimulation leads to response of a particular sensory neuron" Levine & Schefner and others 45 Classical retinal physiology Werblin & Dowling,

24 47 Ionotropic & metabotropic glutamate receptors 48 24

25 Synaptic transmission - glutamatergic Glutamate Ionotropic (GluR) Kainate Ampa NMDA Metabotropic mglur 49 Ionotropic and metabotropic glutamate receptors Ionotropic Metabotropic 50 25

26 Glutamate receptors in the OPL Webvision 51 Bipolar cells of the retina: the beginning of parallel pathways Boycott & Waessle 52 26

27 Convergence 53 Rod to RBC Trpm1* *Transient receptor potential (TRP) melastatin R.G. Smith, Univ. Penn 54 27

28 Primary rod pathway Synaptic organization: IPL Ribbon synapse Rod bipolar cell axon terminal: dyad 55 Rod and cone pathways 56 28

29 Rod Pathways mglur iglur glycine Demb et al., (2002) Primary Rod RBC AII CB - GC Secondary Rod Cone CB - GC Tertiary Rod - Off CB - GC 57 Retinal circuitry importance of horizontal cell feedback in surround formation for bipolar cells. Surrounds are enriched by amacrine cells for ganglion cells 58 29

30 Retinal ganglion cell receptive fields Center-Surround 59 Midget pathways project to parvocellular layers of the LGN (Martin et al., 1998) Horizontal cell feedback for surrounds is likely. On and off pathways are in parallel, and do not contribute to surrounds of other pathway in the midget and parallel pathways H-cell 60 30

31 Parasol cell diffuse pathways project to Magnocellular layers of the LGN (Martin et al., 1998) H-cell Amacrine cells 61 Small bistratified, s-cone pathways konio projecting Dacey 62 31

32 Midget pathway Summary: Parallel pathways through the retina for cone signals: cone to bipolar cell to ganglion cell Midget, On and Off (70% of ganglion cells) Diffuse/Parasol, On and Off (10% of ganglion cells) SBS pathway (On-OFF) (8% of ganglion cells) Melanopsin cells Dacey & Packer, 2003 Nassi & Calloway, Parallel pathways through the into the central visual pathways via the LGN in primate (W- probably Melanopsin cell) 64 32

33 Mosaic of neighboring parasol cells retrogradely stained from injections of biotinylated rhodamine dextran injections into the superior colliculus. (Circles show dendritic fields) 2008 by Society for Neuroscience Crook J D et al. J. Neurosci. 2008;28: Central retinal projections in primate of M, P, K to LGN, M to SC, and melanopsin cells to most other sites, as well as LGN