1. Lecture 12: olfaction: the insect antennal lobe References: H C Mulvad, thesis (http://www.nordita.dk/~mulvad/Thesis), Ch 2http://www.nordita.dk/~mulvad/Thesis G Laurent, Trends Neurosci 19 489-496 (1996) M Bazhenov et al, Neuron 30 553-567 and 569-581 (2001) Dayan & Abbott, Sect 7.5

2. Olfaction (smell)

3. The oldest sense (even bacteria do it)

4. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar)

5. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar) Basic anatomy:

6. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar) Basic anatomy: Insects:receptor cells -> antennal lobe -> mushroom bodies

7. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar) Basic anatomy: Insects:receptor cells -> antennal lobe -> mushroom bodies Mammals: receptor cells -> olfactory bulb -> olfactory cortex

8. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar) Basic anatomy: Insects:receptor cells -> antennal lobe -> mushroom bodies Mammals: receptor cells -> olfactory bulb -> olfactory cortex ~100000 receptor cells, several hundred types (distinguished by receptor proteins)

9. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar) Basic anatomy: Insects:receptor cells -> antennal lobe -> mushroom bodies Mammals: receptor cells -> olfactory bulb -> olfactory cortex ~100000 receptor cells, several hundred types (distinguished by receptor proteins) any cell responsive to a range of odorants:

10. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar) Basic anatomy: Insects:receptor cells -> antennal lobe -> mushroom bodies Mammals: receptor cells -> olfactory bulb -> olfactory cortex ~100000 receptor cells, several hundred types (distinguished by receptor proteins) any cell responsive to a range of odorants: => an odor produces a characteristic pattern of activity across the receptor cell population

11. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar) Basic anatomy: Insects:receptor cells -> antennal lobe -> mushroom bodies Mammals: receptor cells -> olfactory bulb -> olfactory cortex ~100000 receptor cells, several hundred types (distinguished by receptor proteins) any cell responsive to a range of odorants: => an odor produces a characteristic pattern of activity across the receptor cell population Receptor physiology: Receptor proteins (1 kind/cell): metabotropic, G-protein coupled, lead to opening of Na channels

12. Olfaction (smell) The oldest sense (even bacteria do it) Highly conserved in evolution (mammals and insects similar) Basic anatomy: Insects:receptor cells -> antennal lobe -> mushroom bodies Mammals: receptor cells -> olfactory bulb -> olfactory cortex ~100000 receptor cells, several hundred types (distinguished by receptor proteins) any cell responsive to a range of odorants: => an odor produces a characteristic pattern of activity across the receptor cell population Receptor physiology: Receptor proteins (1 kind/cell): metabotropic, G-protein coupled, lead to opening of Na channels, similar to phototransduction in retina

13. Antennal lobe ~1000-10000 neurons in locust: 1130: 830 excitatory, 300 inhibitory in honeybee: 800 excitatory, 4000 inhibitory

14. Antennal lobe ~1000-10000 neurons in locust: 1130: 830 excitatory, 300 inhibitory in honeybee: 800 excitatory, 4000 inhibitory Organized into glomeruli (bunches of synapes) (~1000 in locust, 160 in bee)

15. Antennal lobe ~1000-10000 neurons in locust: 1130: 830 excitatory, 300 inhibitory in honeybee: 800 excitatory, 4000 inhibitory Organized into glomeruli (bunches of synapes) (~1000 in locust, 160 in bee)

16. Antennal lobe ~1000-10000 neurons in locust: 1130: 830 excitatory, 300 inhibitory in honeybee: 800 excitatory, 4000 inhibitory Organized into glomeruli (bunches of synapes) (~1000 in locust, 160 in bee) Connections between AL neurons: dendrodentritic

17. Excitatory cells (PN) PN = projection neuron: axon takes its spikes out of the antennal lobe, to the mushroom bodies (+ other higher areas)

18. Excitatory cells (PN) PN = projection neuron: axon takes its spikes out of the antennal lobe, to the mushroom bodies (+ other higher areas) transmitter: ACh

19. Excitatory cells (PN) PN = projection neuron: axon takes its spikes out of the antennal lobe, to the mushroom bodies (+ other higher areas) transmitter: ACh

20. Excitatory cells (PN) PN = projection neuron: axon takes its spikes out of the antennal lobe, to the mushroom bodies (+ other higher areas) transmitter: ACh Dendrites have postsynaptic terminals in 1 or more glomeruli (10-20 in locust)

21. Inhibitory cells (LN) LN = local neuron: projects only within the antennal lobe

22. Inhibitory cells (LN) LN = local neuron: projects only within the antennal lobe no Na spikes, only Ca “spikelets”

23. Inhibitory cells (LN) LN = local neuron: projects only within the antennal lobe no Na spikes, only Ca “spikelets” transmitter: GABA

24. Inhibitory cells (LN) LN = local neuron: projects only within the antennal lobe no Na spikes, only Ca “spikelets” transmitter: GABA

25. Inhibitory cells (LN) LN = local neuron: projects only within the antennal lobe no Na spikes, only Ca “spikelets” transmitter: GABA Dendrites with postsynaptic terminals in several or all glomeruli

26. Antennal lobe responses:temporally modulated oscillatory activity patterns

27. ~20 hz oscillations:

28. Antennal lobe responses:temporally modulated oscillatory activity patterns (No oscillations in input from receptor cells) ~20 hz oscillations:

29. Oscillations and transient synchronization membrane potentials

30. Oscillations and transient synchronization membrane potentials Local field potential In mushroom body: Measures average AL activity (cell in mushroom body)

31. Oscillations and transient synchronization membrane potentials Local field potential In mushroom body: Measures average AL activity PN firing transiently synchronized to LFP (cell in mushroom body)

32. Model (Bazhenov et al) 90 PNs, 30 LNs

33. Model (Bazhenov et al) 90 PNs, 30 LNs Single-compartment, conductance-based neurons

34. Model (Bazhenov et al) 90 PNs, 30 LNs Single-compartment, conductance-based neurons (post)synaptic kinetics

35. Model (Bazhenov et al) 90 PNs, 30 LNs Single-compartment, conductance-based neurons (post)synaptic kinetics Fast excitation, fast and slow inhibition

36. Model (Bazhenov et al) 90 PNs, 30 LNs Single-compartment, conductance-based neurons (post)synaptic kinetics Fast excitation, fast and slow inhibition 50% connectivity, random

37. Model (Bazhenov et al) 90 PNs, 30 LNs Single-compartment, conductance-based neurons (post)synaptic kinetics Fast excitation, fast and slow inhibition 50% connectivity, random Stimuli: 1-s current pulse inputs to randomly-chosen 33% of neurons

38. Bazhenov network

39. Excitatory neurons

40. Active currents:

41. Excitatory neurons Active currents: Na

42. Excitatory neurons Active currents: Na K

43. Excitatory neurons Active currents: Na K A-current

44. Excitatory neurons Active currents: Na K A-current Synaptic input

45. Excitatory neurons Active currents: Na K A-current Synaptic input Fast (ionotropic) synaptic currents (nACh and GABA A ): ( [O] is open fraction)

46. Excitatory neurons Active currents: Na K A-current Synaptic input Fast (ionotropic) synaptic currents (nACh and GABA A ): ( [O] is open fraction) [T] is transmitter concentration:

47. Excitatory neurons Active currents: Na K A-current Synaptic input Fast (ionotropic) synaptic currents (nACh and GABA A ): ( [O] is open fraction) [T] is transmitter concentration: exc inh

48. Slow inhibition Kinetics like GABA B

49. Slow inhibition Kinetics like GABA B G-protein concentration:

50. Slow inhibition Kinetics like GABA B G-protein concentration: Activated receptor concentration

51. Slow inhibition Kinetics like GABA B G-protein concentration: Activated receptor concentration Fast and slow Components:

52. Inhibitory neurons

53. Active currents:

54. Inhibitory neurons Active currents: Ca

55. Inhibitory neurons Active currents: Ca ( -> Ca spikes)

56. Inhibitory neurons Active currents: Ca K ( -> Ca spikes)

57. Inhibitory neurons Active currents: Ca K Ca-dependent K current ( -> Ca spikes)

58. Inhibitory neurons Active currents: Ca K Ca-dependent K current ( -> spike rate adaptation)( -> Ca spikes)

59. Inhibitory neurons Active currents: Ca K Ca-dependent K current Dynamics of n K(Ca) : ( -> spike rate adaptation)( -> Ca spikes)

60. Inhibitory neurons Active currents: Ca K Ca-dependent K current Dynamics of n K(Ca) : Ca dynamics: ( -> spike rate adaptation)( -> Ca spikes)

61. 2 neurons (1 PN, 1LN)

62. 6 PNs + 2 LNs

63. (fast) inhibition between LNs

64. 6 PNs + 2 LNs (fast) inhibition between LNs

65. 6 PNs + 2 LNs (fast) inhibition between LNs LNs take turns:

66. Full network (90+30)

67. Responses of 4 PNs to 1 stimulus

68. Reliable (trial-to-trial reproducible) firing timing when there is large Inhibitory input

69. Another stimulus: Input to same set of PNs but different LNs

70. Another stimulus: Input to same set of PNs but different LNs

71. Another stimulus: Input to same set of PNs but different LNs Same overall firing rate pattern, but different temporal fine structure

72. 3 rd stimulus: Input to 90%-different set of neurons:

73. 3 rd stimulus: Input to 90%-different set of neurons:

74. 3 rd stimulus: Input to 90%-different set of neurons: Different firing pattern across neurons (but same network-average rate)

75. Blocking LN-LN inhibition LNs now spike ~ regularly

76. Blocking LN-LN inhibition LNs now spike ~ regularly Less difference between responses to stimuli 1 and 2

77. Reducing I K(Ca) (reducing LN spike-rate adaptation)

78. Reducing I K(Ca) (reducing LN spike-rate adaptation)

79. Reducing I K(Ca) Less precise timing, weaker temporal modulation, reduced discriminability (reducing LN spike-rate adaptation)

80. Role of slow LN-PN inhibition

81. Slow rate modulations abolished

82. Role of slow LN-PN inhibition Slow rate modulations abolished  reduced discriminability