Neural Mechanisms of Startle BehaviorRobert C. Eaton In the past fifteen years there has been considerable interest in neural circuits that initiate behavior patterns. For many types of behaviors, this involves decision-making circuits whose primary elements are neither purely sensory nor motor, but represent a higher order of neural pro cessing. Of the large number of studies on such systems, analyses of startle circuits compose a major portion, and have been carried out on systems found throughout the animal kingdom. Startle has been an im portant model because of the reliability of the behavioral act for laboratory study and the accessibility of the underlying neural circuitry. However, probably because of the breadth of the subject, this material has never been reviewed in a comprehensive way that presents the elements com mon to startle circuits in the different animal systems in which they occur. This book presents a diversity of approaches based on a broad back ground of animal groups ranging from the earliest nervous systems in cnidarians to the most recently evolved and advanced in mammals. The behaviors themselves are all short latency, fast motor acts, when consid ered on the time scale of the organism, and involve avoidance or evasion, although in some cases we do not yet completely understand their natural role. These behaviors occur in response to stimuli that have sudden or unexpected onset. |
Contents
1 Introduction | 1 |
2 The Distribution of Startle and Escape Responses | 2 |
3 The Distribution of Giant Fiber Systems and Responses They Mediate | 4 |
4 The General Neurobiological Significance of Studies on Fast Systems | 6 |
5 Some Historical Notes to the Contributions That Follow | 9 |
6 References | 11 |
1 Introduction | 15 |
2 Fast Pathways in Sea Anemones and Colonial Anthozoans | 17 |
24 The Central Consequences of LG Firing Do Not Produce Postflexion Reextension Which Is Instead a Chain Reflex | 187 |
25 LG Firing Promotes but Does Not Drive Subsequent Swimming | 189 |
26 Commentary | 191 |
3 The Circuitry for Tailflip Production | 192 |
31 New Findings | 193 |
32 The Relationship between Giant and Nongiant Tailflip Pattern Generating Circuitry | 200 |
33 Why Are the SGs Interposed between Giants and FFs? | 202 |
34 Switching of Outputs of the Nongiant Premotor Neuron 13 | 205 |
3 The Escape System of Aglantha | 19 |
32 Layout of Nerves and Muscles | 21 |
33 Physiological Analysis | 22 |
4 The Escape Systems of Siphonophores | 26 |
41 Nanomia | 28 |
42 Chelophyes | 37 |
5 Conclusions | 39 |
6 References | 41 |
1 Introduction | 43 |
11 Evidence That Giant Nerve Fibers Mediate Rapid Escape | 44 |
12 Experimental Utility of Annelid Escape Reflexes | 45 |
2 Polychaete Escape Reflexes | 46 |
21 Afferent Pathways | 47 |
22 Central Conduction | 49 |
23 Efferent Pathways and Behavioral Correlates | 51 |
3 Giant Fiber Reflexes in Leeches | 53 |
4 Rapid Escape Reflexes in Oligochaete Earthworms | 58 |
42 Conduction Properties of Giant Fibers | 62 |
43 Afferent Pathways | 64 |
44 Efferent Pathways | 69 |
45 Rapid Escape Movements | 72 |
46 Habituation | 75 |
5 Growth and Development of Earthworm Giant Fiber Systems | 76 |
51 Embryonic and Postembryonic Development of Escape Reflexes | 77 |
52 Food Deprivation Effects on Giant Fiber Growth | 79 |
53 Regeneration of Giant Fibers | 81 |
6 Conclusions | 85 |
7 References | 86 |
1 Introduction | 93 |
11 Historical Background | 94 |
2 The Escape Behavior | 95 |
23 Sensory Structures That Evoke Escape | 98 |
3 Neural Elements of the Escape System | 99 |
32 Sensory Structures of First Instar Nymphs | 101 |
33 The Giant Interneurons | 104 |
4 Alterations of the Escape Response | 122 |
42 dGIs as Bifunctional Interneurons | 123 |
5 Summary | 126 |
6 References | 128 |
1 Introduction | 133 |
2 Behavior | 134 |
3 Normal Anatomy and Physiology | 137 |
4 Development | 151 |
5 Mutants | 153 |
52 Physiological Screen | 154 |
53 Examples of Mutants | 155 |
6 Conclusion | 159 |
7 References | 160 |
1 Introduction | 163 |
2 The Jump in the Locust | 164 |
3 Patterning of Motor Activity for the Jump | 166 |
4 Movement Detector MD Neurons in the Locust | 169 |
5 Initiation of the Jump by MovementDetecting Neurons | 174 |
6 Conclusions | 176 |
7 References | 177 |
1 Introduction | 179 |
2 The Roles of the Giant Axons | 181 |
21 The LGs Are Necessary for the Short Latency Phasic Flexions That Follow Them | 183 |
22 The LGs Are the Decision and Trigger Neurons for LG Tailflips | 184 |
23 The LGs Are Sufficient for Phasic Flexion but Do Not Produce Fully Normal Responses | 185 |
4 Concluding Remarks | 209 |
1 Introduction | 213 |
2 Types of Startle Responses and FastStarts | 216 |
3 Stimulus Conditions for Eliciting FastStarts | 218 |
4 Performance Measures of FastStarts | 220 |
42 Mechanical Form | 221 |
43 The Role of FastStarts in Predator and Object Avoidance | 224 |
44 Directionality of the Escape Response | 225 |
5 The Mauthner Cell | 227 |
6 The Role of the M Cell in Triggering FastStarts | 230 |
61 Evidence from Chronic Electrophysiological Recordings | 233 |
62 Evidence from Acute Electrophysiological Recordings | 235 |
7 Sensory Inputs to the M Cell | 236 |
71 Eighth Nerve Afferents | 237 |
72 Lateral Line Afferents | 239 |
8 Initiation and Propagation of the M Spike | 241 |
9 Inhibitory Actions on the M Cell | 242 |
92 Chemically Mediated Collateral Inhibition of the MCell Soma | 245 |
93 Neurons Responsible for Collateral Inhibition | 246 |
94 Dendritic Location of Presynaptic and Postsynaptic Inhibition | 248 |
101 Cranial and Pectoral Fin Components | 249 |
102 Axial Musculature | 251 |
103 Crossed Spinal Inhibition | 252 |
11 Fatigue in the MCell System and Response Changes Possibly Underlying Habituation | 253 |
12 NonMauthner FastStart Circuits | 256 |
13 Discussion and Conclusions | 259 |
14 References | 262 |
1 Introduction | 267 |
2 A Device for the Assessment of Startle | 269 |
21 Calibration of the Response Detection Unit | 272 |
23 The Production of Visual Signals | 274 |
25 The Modification of Reflex Latency | 275 |
27 General Procedural Considerations | 277 |
3 Assessing the Threshold for Startle | 278 |
32 The UpDown Technique | 280 |
33 Reflex Modification Procedures to Assess Sensory Thresholds | 282 |
4 Conclusions | 283 |
5 References | 284 |
1 Introduction | 287 |
2 The Behavioral Response | 288 |
22 The Form of the Response | 289 |
3 Organisms with the System | 293 |
42 Extrinsic Neural Systems That Modulate Startle | 300 |
5 Pharmacology | 304 |
52 Neurotransmitters That Modulate Startle | 305 |
6 Development | 323 |
7 Modification of Startle by Prior Experience | 324 |
72 Habituation | 325 |
73 Sensitization | 332 |
74 Conditioned Fear and Startle | 338 |
8 Summary and Conclusions | 341 |
9 References | 342 |
1 Introduction | 353 |
2 Large Size Electrical Transmission and Speed of Response | 354 |
3 Command Neurons Shared Circuitry and Modulation of AllorNone Responses | 357 |
4 Some Conclusions and Some Questions | 361 |
362 | |
365 | |
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Common terms and phrases
acoustic startle action potentials activity afferent Aglantha amplitude animal annelids auditory background noise Biol brain Camhi cercus circuitry clonidine cockroach command neuron Comp conduction velocity contralateral crayfish Davis DCMD dendrite dGIs dorsal earthworm Eaton electrical elicited EPSP escape behavior escape reflex escape response evoked excitation Faber fast-start Figure firing fish flexion flexor function ganglion giant axons giant fiber giant fiber systems giant interneurons giant nerve fibers goldfish Günther habituation increase startle inhibition inhibitory initial input intensity interneurons interval intracellular ipsilateral jump Korn Krasne latency lesions LGMD Lumbricus terrestris M-cell m/sec Mauthner cell mediated MGF spikes motoneurons movements msec muscle Nanomia nerve cord nervous system neural nongiant occur pathway pattern Physiol polychaetes posterior prepulse produced Psychol rats recording Ritzmann segments sensory siphonophore spinal startle reaction startle reflex startle response stimulus studies swimming synapses tactile tailflip teleosts threshold transmission ventral vGIs visual wind zebrafish
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