behavior analysis in a natural environment in the laboratory cells, synapses & circuits

#04: CELLS, SYNAPSES & CIRCUITS • behavior analysis • in a natural environment • in the laboratory • cells, synapses & circuits • basic properties of nerve cells • synaptic transmission • neuronal architecture & behavior • relating nerve cells to behavior • summary

NEURONAL ARCHITECTURE OF BEHAVIOR • behavior  circuits of interacting neurons, 3 types: SENSORY INPUT CENTRAL PROCESSING MOTOR OUTPUT BEHAVIOR

NEURONAL ARCHITECTURE OF BEHAVIOR • behavior  circuits of interacting neurons, 3 types: • sensory neurons... signal input • specialized receptor cells • convert features of environment neural signals • interneurons... central processing • motor neurons... motor output (behavior) • drive muscle activity @ neuromuscular junction • generate excitatory junctional potentials(EJPs)

NEURONAL ARCHITECTURE OF BEHAVIOR • electrical recordings: • electrode type • position ~ cells • extracellular V,  • intracellular mV,  • advantages & disadvantages p.24, fig.1.10

NEURONAL ARCHITECTURE OF BEHAVIOR • extracellular electrode • motor neurons • “unit” activity (>1) • ~ current flow in extracellular space p.24, fig.1.10

NEURONAL ARCHITECTURE OF BEHAVIOR • intracellular electrode • single motor neuron p.24, fig.1.10

NEURONAL ARCHITECTURE OF BEHAVIOR • extracellular electrode • records propagation of action potentials along axons p.24, fig.1.10

NEURONAL ARCHITECTURE OF BEHAVIOR • intracellular electrode • muscle fiber • EJPs  signals... • motor neuron  • others p.24, fig.1.10

NEURONAL ARCHITECTURE OF BEHAVIOR • extracellular electrode • electromyogram (EMG) • whole muscle activity p.24, fig.1.10

NEURONAL ARCHITECTURE OF BEHAVIOR • behavior  circuits... simple ones (in mammals) • e.g., human knee jerk reflex... • tap knee below patella •  stretches receptors in quads (muscle spindles) • activates sensory neurons (Ia) • synapse  motor neurons () •  contraction of quads p.25, fig.1.11

NEURONAL ARCHITECTURE OF BEHAVIOR • behavior  circuits... simple ones (in mammals) • e.g., human knee jerk reflex... • simple ? • sensory-motor ? • monosynaptic ? • no, other neurons involved p.25, fig.1.11

NEURONAL ARCHITECTURE OF BEHAVIOR • circuit complexity • e.g., primate visual cortex • boxes = assemblies of • 103 s of neurons • 106 s of synapses • 2 main pathways • V1  PG... object location • V1  TE... visual form p.25, fig.1.11

NEURONAL ARCHITECTURE OF BEHAVIOR • circuit complexity • e.g., primate visual cortex • Q: how to study cellular properties of neurons among such complexity ? • A: chose: • accessible behavior • in model organism providing special advantages p.25, fig.1.11

NEURONAL ARCHITECTURE OF BEHAVIOR • advantages & disadvantages • interesting... it is ALL interesting (not only ~ humans) • maintenance, availability & access to sufficient #s • model system... biology & tools available • behavior • anatomy / physiology • cell biology • pharmacology • genetics / genomics / proteomics

NEURONAL ARCHITECTURE OF BEHAVIOR • advantages & disadvantages • e.g., C. elegans (nematode) • cheap, maintenance, sample sizes, simple • behavior, simple anatomy, small simple & well- • characterized nervous system, development & cell • biology, genetic & pharmacological tools good • boring behavior, few properties of neuronal • assemblies or structures, small neurons • (electrophysiology difficult but accessible)

NEURONAL ARCHITECTURE OF BEHAVIOR • advantages & disadvantages • e.g., H. sapiens (humans) • interesting behavior, need to knowing how we • function (medical), sequenced genome,  ~ easy • research funding arguments • prohibitively complex in every respect, moral • issues for invasive & experimental study, • expensive, inconvenient & uncooperative subjects

RELATING NERVE CELLS TO BEHAVIOR • investigating how neurons  behavior • e.g., crayfish response to tail tactile stimulus • record lateral giant interneuron (LGI) • correlation (A): always stimulusbehavior ?...  p.27, fig.1.12

RELATING NERVE CELLS TO BEHAVIOR • investigating how neurons  behavior • e.g., crayfish response to tail tactile stimulus • record lateral giant interneuron (LGI) • correlation (A): always stimulusbehavior ?...  • sufficient (B): trigger LGI alone  response ?...  p.27, fig.1.12

RELATING NERVE CELLS TO BEHAVIOR • investigating how neurons  behavior • e.g., crayfish response to tail tactile stimulus • record lateral giant interneuron (LGI) • correlation (A): always stimulusbehavior ?...  • sufficient (B): trigger LGI alone  response ?...  • necessary (C): shut off LGI  no response ?...  p.27, fig.1.12

RELATING NERVE CELLS TO BEHAVIOR • investigating how neurons  behavior • e.g., crayfish response to tail tactile stimulus • record lateral giant interneuron (LGI) • correlation (A): always stimulusbehavior ?...  • sufficient (B): trigger LGI alone  response ?...  • necessary (C): shut off LGI  no response ?...  • should always attempt to ask these 3 questions, but • we rarely find this type of simplicity in nature

RELATING NERVE CELLS TO BEHAVIOR • investigating how synapses  behavior • e.g., Drosophila escape response (mutants, pharmacological agents) • inject current across brain

RELATING NERVE CELLS TO BEHAVIOR • investigating how synapses  behavior • e.g., Drosophila escape response (mutants, pharmacological agents) • inject current across brain • measure speed of transmission in down-stream motor neurons • chemical synapses: slow

RELATING NERVE CELLS TO BEHAVIOR • investigating how synapses  behavior • e.g., Drosophila escape response (mutants, pharmacological agents) • inject current across brain • measure speed of transmission in down-stream motor neurons • chemical synapses: slow • electrical synapses: fast (middle leg) escape behavior

RELATING NERVE CELLS TO BEHAVIOR • investigating how restricted neural networks  behavior • e.g., lobster ingestion • food  esophagus  3 chamber stomach: • cardiac sac • gastric mill • pylorus

} rhythmic RELATING NERVE CELLS TO BEHAVIOR • investigating how restricted neural networks  behavior • e.g., lobster ingestion • food  esophagus  3 chamber stomach: • cardiac sac • pylorus (A) • gastric mill (C) p.28, fig.1.13

RELATING NERVE CELLS TO BEHAVIOR • investigating how restricted neural networks  behavior • e.g., lobster ingestion • stomatogastric ganglia (STG)  rhythm • all 30 neurons known • circuits mapped (B,D) • functions in isolated preparations (A,C) p.28, fig.1.13

RELATING NERVE CELLS TO BEHAVIOR • neural control  behavior in complex organism • e.g., selective attention in monkeys (stimulus choice) • unit recordings in cortex • cellular response to peripheral light (A) p.30, fig.1.14

RELATING NERVE CELLS TO BEHAVIOR • neural control  behavior in complex organism • e.g., selective attention in monkeys (stimulus choice) • unit recordings in cortex • cellular response to peripheral light (A) • response > if animal pays attention (B) p.30, fig.1.14

RELATING NERVE CELLS TO BEHAVIOR • neural control  behavior in complex organism • e.g., selective attention in monkeys (stimulus choice) • unit recordings in cortex • cellular response to peripheral light (A) • response > if animal pays attention (B) • response >> if animal  ~ behavior (C) p.30, fig.1.14

RELATING NERVE CELLS TO BEHAVIOR • neural control  behavior in complex organism • e.g., selective attention in monkeys (stimulus choice) •  visual system response due to • ~ stimulus • other neural systems ~attention (& ~ activity ?) • gain some understanding of mechanism, even at this simple level of analysis

SUMMARY: INTRODUCTION & TERMS • behavior... examples discussed: • field studies  ethology • ethograms • FAP, SS, IRM, releasers, interlocking releasers • laboratory studies  associative learning • classical / Pavlovian conditioning, US, CS, UR, CR • operant/instrumental conditioning

SUMMARY: INTRODUCTION & TERMS • nervous system • neurons • channels, resting potentials, action potentials • synapses • chemical, electrical, EPSPs, IPSPs • plasticity, synaptic depression & potentiation, presynaptic inhibition & facilitation • circuits • sensory neurons, interneurons, motor neurons • recording neural activity

SUMMARY: INTRODUCTION & TERMS • relating nerve cells to behavior • neurons  behavior • crayfish tail flip response • synapses  behavior • Drosophila escape response • restricted circuits  behavior • lobster digestion • whole organism  behavior • monkey selective attention

SUMMARY: WE HAVE NOT DISCUSSED… • nervous system development and plasticity… • neurogenesis, apoptosis and necrosis • growth • cell adhesion and axon pathfinding • formation, maintenance and plasticity of synapses • organogenesis • general brain and nervous system anatomy… • humans • other vertebrates • invertebrates

SUMMARY: WE HAVE NOT DISCUSSED… • brains are not merely composed of neurons… glia… • oligodendrocytes* and astrocytes (CNS) • Schwann cells (PNS)* • form myelin sheath (vertebrates) • neuron cell structure… general categories… • microfilaments, neurofilaments and microtubules • axon transport • structure and functional details at synapses • ion channel anatomy

SUMMARY: WE HAVE NOT DISCUSSED… • details about signals transmission… • action potentials • frequency coding • signal propagation • myelin function • “types” of signalling • silent, beating, bursting • effects of sustained neural stimulation • changing neuron properties

SUMMARY: WE HAVE NOT DISCUSSED… • measuring currents and channels… electrophysiology… • criteria for ion channel activities • conductance, selectivity, gating, pharmacology • activation, inactivation • whole cell voltage clamp • patch (voltage) clamp • ion channel molecular biology and manipulation • maintenance of ion concentration gradients

SUMMARY: WE HAVE NOT DISCUSSED… • intercellular communication… • gap junctions and neurosecretion • neurotransmitter release • transmitters and hormones • receptors and transduction mechanisms • neuromoduation

behavior analysis in a natural environment in the laboratory cells, synapses & circuits