recognition & localization of predators & prey feature analyzers in the brain

1. PART 2: SENSORY WORLDS #10: FEATURE ANALYSIS IN TOADS II • recognition & localization of predators & prey • feature analyzers in the brain • from recognition to response • summary

2. PART 2: SENSORY WORLDS #10: FEATURE ANALYSIS IN TOADS II • recognition & localization of predators & prey • feature analyzers in the brain • from recognition to response • summary

3. FEATURE ANALYZERS IN THE BRAIN • thalamic-pretectal neuron responses to relevant stimuli • many classes of neurons respond, but... • no profiles ~ behavior... • eg, TH3 cells p.109 fig.4.10

4. p.110 fig.4.11 FEATURE ANALYZERS IN THE BRAIN • tectal neuron responses to relevant stimuli • many classes of neurons respond • T5(1) & (2) interesting • T5(1) squares > worms • T5(2) worms > squares • each 20°- 30° of entire visual field

5. FEATURE ANALYZERS IN THE BRAIN • tectal neuron responses to relevant stimuli • T5(2) neurons also showed invariance with • contrast • velocity • distance • T5(2) are candidate prey-recognition neurons • ~ same configural detection rules as behavior • good eg ofneural correlate of behavior

6. FEATURE ANALYZERS IN THE BRAIN • tectal neuron responses to relevant stimuli • remaining questions about T5(2) neurons perform prey recognition function (addressed next time...) • how are they wired into nervous system ? • further evidence for proposed function ?

7. FEATURE ANALYZERS IN THE BRAIN • ganglion cells, contralateral projections  OT & TP • orderly maps retinotopic projections • neuron classes (R16) p.105 fig.4.7 p.103 fig.4.5

8. FEATURE ANALYZERS IN THE BRAIN • tectal neuron responses to relevant stimuli • remaining questions about T5(2) neurons perform prey recognition function (addressed next time...) • how are they wired into nervous system ? • further evidence for proposed function ?

9. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • main determinants of neuron response properties • timing • magnetude • what are the sources of T5(2) cell inputs ? of excitatory / inhibitory input

10. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • TP inhibition of T5(2) neurons in OT • diagonal moving stimulus... p.111 fig.4.12

11. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • TP inhibition of T5(2) neurons in OT • diagonal moving stimulus  excitation p.111 fig.4.12

12. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • TP inhibition of T5(2) neurons in OT • diagonal moving stimulus  excitation • + electrical stimulation of TP  inhibition p.111 fig.4.12

13. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • TP inhibition of T5(2) neurons in OT • diagonal moving stimulus  excitation • + electrical stimulation of TP  inhibition • remove electrical stimulation  excitation p.111 fig.4.12

14. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • TP inhibition of T5(2) neurons in OT • OT excitation of TP neurons (no details... reverse experiment likely did not give reverse results) p.111 fig.4.12

15. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • TP inhibition of T5(2) neurons in OT  avoidance ? • OT excitation of TP neurons  orienting ? p.111 fig.4.12

16. TH3 T5(2) FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • connectivity possibilities TP OT • what would happen... ? • feedback loop  oscillator • what about T5(2) feature analyzer output ?

17. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • proposed connectivity T5(1) T5(2) OT TP TH3 • rationale not immediately clear • let’s examine this hypothesis anyway...

18. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • recall response profiles of all 3 types of neurons • TH3... (in TP) • T5(1)... (in OT) • T5(2)... (putative feature analyzers in OT) p.113 fig.4.13

19. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • consider the relative effects of a worm stimulus... • TH3 doesnot inhibit • T5(1) does excite • T5(2)  net effect... excited about worms p.113 fig.4.13

20. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • consider the relative effects of the antiworm... • TH3 doesinhibit • T5(1) does not excite • T5(2) not excited about the antiworm stimulus p.113 fig.4.13

21. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • consider the relative effects of the square... • TH3 doesinhibit • T5(1) does excite • T5(2) moderately excited about squares p.113 fig.4.13

22. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • neuron firing in the hypothetical circuit (schematic) • worm • antiworm • sm square • lg square • recall EFR & IFR p.113 fig.4.13

23. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • PT inhibitory signals  OT for T5(2) response • disrupt PT should block inhibition p.113 fig.4.13

24. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • no lesion... intact PT • lesion in PT • 2 things happen to T5(2) response • no inhibition • selectivity lost p.114 fig.4.14

25. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • lesion in PT • profiles of T5(2) firing (B) = behavior (C) p.114 fig.4.14

26. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • increased responses to “inappropriate” stimuli • termed disinhibition syndrome • orienting & snapping at non-prey items: • other toads • experimenter • own extremities

27. FEATURE ANALYZERS IN THE BRAIN • neural circuit for feature analysis • T5(2) = feature analyzer neurons in prey-catching • further evidence • inter- & intracellular recordings • during behavior • neurons fire while animals orient • stimulate same neuron  same orientation • ok then... how do T5(2) neurons  motor centers ? • final section of chapter

28. FROM RECOGNITION TO RESPONSE • motor centers: bulbar-spinal region of brain • OT (T5(2) & other) neurons project  BS region • stimulate BS region  spike in T5(2) neurons* • dye-fill T5(2)  see projections into BS region * opposite to the normal direction of information flow... “antidromic” (?)

29. FROM RECOGNITION TO RESPONSE • adaptive motor response model • sensory-motor interface: command-releasing systems (CRSs) • made of command elements (CEs)... eg, T5(2) & TH3 • motor program generators (MPGs) p.116 fig.4.15

30. p.97 fig.4.1 FROM RECOGNITION TO RESPONSE • adaptive motor response model p.116 fig.4.15

31. FROM RECOGNITION TO RESPONSE • adaptive motor response model • specific responses of feature detector neurons • behavioral experiments • anatomical analyses of brain structures • physiological analyses of PT & OT neurons • initial concept incorrect... • response not from single aspect of stimulus • configuration of stimuli... sign stimuli ~ prey • assemblies of filtering / triggering elements

32. SUMMARY: SENSORY WORLDS • input specialization • conversion of physical stimulus  neural signal • acoustic fovea on basilar membrane in bat • visual fovea in front of toad

33. SUMMARY: SENSORY WORLDS • receptive field of a neuron • source of stimulus and/or representation on sensory surface (e.g. basilar membrane or retina) • center/surround; excite/inhibit • auditory difficult, achieved by neural processing • essential aspect of receptive fields  contrast

34. SUMMARY: SENSORY WORLDS • tuning • sensory neurons respond to part of stimulus range • many differently tuned neurons cover whole range • achieves gain in sensitivity > broad tuned system

35. SUMMARY: SENSORY WORLDS • maps • sensory world represented in brain map • toad: retina tectum • owl: auditory world ICX • bat: distance/velocity profiles cortex • 3 common features: • topography: near-neighbor relationships preserved; tonotopy, retinotopy • distortion: fovea overrepresented • alignment: multimodal maps coincide

36. SUMMARY: SENSORY WORLDS • abstraction • aspects of stimuli are perceived separately • owl: timing & intensity processing • bat: velocity & distance processing • how are parts reassembled by the brain ? • EMERGENT PROPERTIES REALIZED

37. SUMMARY: SENSORY WORLDS • feature analyzers • some neurons respond to complex stimuli • toad: T5(2) neurons & moving worm stimuli • bat: cortex neurons & multiple harmonic echoes • capture important aspects of behaviorally relevant stimuli

38. SUMMARY: SENSORY WORLDS • coincidence detection • post-synaptic neuron responses to coincident temporal signals • owl: left/right coincidence in nucleus laminaris; also includes concept of delay lines • unique disparities encoded by multiple delay lines • range of disparities represented in neural network

39. SUMMARY: SENSORY WORLDS • exam 1: R.2.22