1. H CH7: escape behavior in crayfish H behavior features & functional anatomy H neuronal architecture H adaptive modulation H summary: chapter 7 PART 3: MOTOR STRATEGIES #15: ESCAPE BEHAVIOR IN CRAYFISH

2. H walking is normal mode of locomotion H integrated motor escape response  tail flip H tail propulsion using flexor & extensor muscles BEHAVIOR & FUNCTIONAL ANATOMY

3. H nongiant H slower H medial giant: H anterior stimulus H move back H rapid H lateral giant: H tail stimulus H move up & back H rapid H 3 types of tail flip response BEHAVIOR & FUNCTIONAL ANATOMY

4. H tail flip can be elicited by H electrical stimulus H tactile stimulus H responses are comparable H triggers initiate complex motor sequences BEHAVIOR & FUNCTIONAL ANATOMY

5. H typical invertebrate CNS plan (ganglia + connectives) H brain H SOG complex H 5 thoracic ganglia H 6 abdominal ganglia... contain tail flip circuitry H ganglia communicate & are coordinated via connectives H peripheral comm. via roots H 1: swimmerets H 2: extensors H 3: flexors (motor only) NEURONAL ARCHITECTURE

6. H 2 pairs of prominent giant axons H lateral giant interneurons (LGI) H cell bodies & dendrites in each abd. segment H electrical synapses (septate / segmental) H axons project  next segment H lateral giant escape H medial giant intern. (MGI) H cell bodies & dendrites in brain H ~ single fast neuron H medial giant escape NEURONAL ARCHITECTURE

7. H giant interneurons  motor giant neurons (MoGs) H MoGs  flexor muscles H sensory input to: H head  MGI  all MoGs H tail  LGI  1-3 MoGs H focus on LGls NEURONAL ARCHITECTURE

8. H LGI tail flip circuitry H sensory input: ~1000 hairs with sensory neurons H sensory interneurons:  LGIs & brain H A: phasic H C: tonic H LGIs NEURONAL ARCHITECTURE

9. H LGI tail flip circuitry H sensory input: ~1000 hairs with sensory neurons H sensory interneurons:  LGIs & brain H A: phasic H C: tonic H LGIs H MoGs NEURONAL ARCHITECTURE

10. H LGI tail flip circuitry H sensory input: ~1000 hairs with sensory neurons H sensory interneurons:  LGIs & brain H A: phasic H C: tonic H LGIs H MoGs H flexor muscles: H 5 / segment H + other input NEURONAL ARCHITECTURE

11. H chemical synapses (slow) at input & output H electrical synapses (fast) elsewhere H sensory  LGI H directly (  ) short latency H indirectly (  ) long latency NEURONAL ARCHITECTURE

12. H chemical synapses (slow) at input & output H electrical synapses (fast) elsewhere H sensory  LGI H directly (  ) short latency H indirectly (  ) long latency H sensory influence  fast flexor motor neurons H LGI  MoGs & segmental giant (SG)... very fast ! NEURONAL ARCHITECTURE

13. H LGIs  SG (electrical) H SGs  fast flexor motor neurons (electrical) NEURONAL ARCHITECTURE

14. H LGI neurons at center of circuit H convergence of sensory input  LGI H divergence of LGI output  motor NEURONAL ARCHITECTURE

15. H 3 components of “flipping out” behavior H rapid flexion of abdomen H re-extension of abdomen H swimming H independent behavior modules NEURONAL ARCHITECTURE

16. H LGIs only involved in flexion H 2 abdominal sensory input channels H  biphasic LGI spike (EPSP) H indirect chemical H direct electrical NEURONAL ARCHITECTURE

17. H rapid flexion response to abrupt tail stimulus because H sensory - interneuron chemical synapses depress with prolonged stimuli H electrical synapses  LGI have high threshold & short time constants H sensory input  presynaptic LGI inhibition NEURONAL ARCHITECTURE

18. H 2 pathways from LGI (elect)  H MoG (chem)  flexor muscles H SG (elect)  FFs (chem)  flexor muscles H FFs threshold below that of signal from SG... H no delay in signal NEURONAL ARCHITECTURE

19. H LGI fast speed from H large diameter axons H electrical synapses H LGI sufficient & necessary for tail flip response ? NEURONAL ARCHITECTURE

20. H necessary: H sever MoG* H stimulate tail flip H hyperpolarize LGI H measure severed MoG output H LGI sufficient & necessary for tail flip response... H  “command neurons” H sufficient: H inject current H  tail flip NEURONAL ARCHITECTURE

21. H LGI makes all-or-nothing decision to escape ? H what about upstream sensory decision ?... H graded, not all-or-none synaptic input H together... explains why there is no partial tail flip NEURONAL ARCHITECTURE

22. H no single LGI satisfied criteria H they are in series, linked abdominal segments H act as functional unit H command neuron H firing or stimulation elicits complex behavior... H eg, coordinated / rhythmic appendage movement H criteria: neuron should demonstrate H activity necessary & sufficient to elicit behavior H normal response to sensory stimulus H normal pattern of activitation NEURONAL ARCHITECTURE

23. H LGI inhibitory signals: “command-derived inhibition” H ensures that additional flexor responses do not occur NEURONAL ARCHITECTURE

24. H LGI inhibitory signals: “command-derived inhibition” H ensures that additional flexor responses do not occur H LGI spikes inhibit further LGI & MGI spikes H sensory, LGIs, MoGs & muscles inhibited NEURONAL ARCHITECTURE

25. H further inhibition of H extension H slow flexor and slow extensor systems H widespread inhibitory influence H critical timing (details... ) H every level of tail flip circuitry NEURONAL ARCHITECTURE

26. H read and be sure you understand text sections on H re-extension H swimming H problems... journal questions NEURONAL ARCHITECTURE

27. H other influences on tail flip responses ? H does not always work H modulated by H restraint-induced inhibition H motivation (feeding) H learning ADAPTIVE MODULATION

28. H blocked by nerve cord transection H decreased facilitation of reflex H increased inhibition at higher levels H voluntary tail flip remains H restraint-induced inhibition ADAPTIVE MODULATION

29. H cut nerve cord abolishes feeding- induced increase H must be eating to influence response H motivational modulation of escape behavior H feeding raises threshold of tail flip response ADAPTIVE MODULATION

30. H feeding modulates LGI firing only H degree of inhibition relative to stimulus H “competition” ADAPTIVE MODULATION

31. H modulation of escape behavior by learning H repetition... what is important & what is not H habituation: reduced response with repeated stimuli H self-induced habituation by water movement ? H prevented by command-derived inhibition ADAPTIVE MODULATION

32. H anterior tactile stimulus  tail flip response H mediated by lateral giant interneurons (LGI) H sensory hair inputs H LGIs sufficient & necessary for response  widespread activation of flexor system H command neurons, trigger escape response H command-derived inhibition, cancels competing response, enables subsequent elements SUMMARY

33. H command-derived inhibition, cancels competing response, enables subsequent elements H reextension from sensory feedback (reafference), via stretch receptors (muscle receptors, MROs) & sensory hairs on tailfan H swimming from central pattern generator activated by sensory input with prolonged delay H modulated by various influences... restraint, feeding, learning SUMMARY

34. H NO CLASS on T.3.20 H SECTION 3 REVIEW on R.3.22 H 2 nd MIDTERM EXAM: H written, 15% of final grade H ASSIGNED (web page) @ 6 pm T.3.27 H DUE (eMail) @ 3 pm R.3.29 NEUROBIOLOGY CALENDAR