Nerve Cells & Behaviour

Question 1

542-520 MYA

CAMBRIAN EXPLOSION

Answer 1

• rise in organism diversity
• rapid appearance of many animal body plans aka. trilobite fossils
• vertebrate origins

Question 2

key questions

BIOLOGICAL PSYCHOLOGY

Answer 2

• how/why do brains/beh change?
• does it always have to be complex?
• are there brain/beh features conserved across taxa/over evolutionary times?
• what do brains/beh of animals reveal about ours/vice versa?

Question 3

THE BRAIN: NAKED EYE

Answer 3

• 15cm front to back (adult)
• even the largest nerve cells are miniscule and need to be stained to be seen
• cortex = 3mm thick

Question 4

THE BRAIN: LIGHT MICROSCOPE

Answer 4

• large nerve cell bodies = 100um (0.1mm) in diameter (x100 magnification)
• large axons/dendrites are about 10um (.01mm) in diameter (x1000 magnification)

Question 5

THE BRAIN: ELECTRON MICROSCOPE

Answer 5

• synaptic ending = 1um in diameter (x10^4 magnification)
• synaptic cleft between neurons = 20nm across (x10^5 mag)
• neuronal membrance = 5nm (x10^6 mag)
• ion channel diameter = .5nm (x10^7 mag)

Question 6

BEHAVIOUR MODEL

Answer 6

• beh can be observed/measured to directly/indirectly identify underlying mechanisms
• evidence = either causal/of correlational nature
• brain/neurons/muscles + evolution -> genetic/epigenetic inheritance + ecology = behaviour

Question 7

TINBERGEN (1963)

Answer 7

• showed why we should care about neuro/physiological mechanisms when studying beh via 4 explanatory lvls:
  1. PROXIMATE - description of mechanisms underlying beh in individual/group
  2. ONTOGENY - development of beh within individual lifespan
  3. PHYLOGENY - development of beh over generations/in dif populations
  4. ULTIMATE/FUNCTIONAL - adaptive sig/utility of beh for organism

Question 8

MACHANISMS & ADAPTIVE FUNCTIONS OF BEHAVIOUR

Answer 8

PROXIMATE CAUSATION
ULTIMATE CAUSATION

Question 9

PROXIMATE CAUSATION

Answer 9

• during animal’s life-time
• how is beh produced?
• how does beh develop?
• how is beh inherited?

Question 10

ULTIMATE CAUSATION

Answer 10

• over several generations
• why has a beh developed?
• what selective advantage does it provide?
• what is the evolutionary history?

Question 11

COMPARATIVE APPROACHES ROOTS

Answer 11

• roots of comparative approaches/methods in beh/neuroscience research
• focus on systematic comparisons by middle of 20th century

Question 12

ETHOLOGY

Answer 12

• “bio study of beh” (Tinbergen (1963))
• “comparative study of beh which applies to beh of animals/humans” (Lorenz (1981))
• ethological approach = animals observed in natural habitats/under ecologically relevant conditions; research focused on beh w/low interindividual variability ie:
  1. LOCOMOTION (walking/swimming/flying)
  2. SEQUENCES (courtship/copulation/fights)
  3. FAST RESPONSES (escape/collision avoidance/capture)

Question 13

BEH = MOTOR OUTPUT

Answer 13

• movement of dif parts of body (dif muscle groups/appendages/limbs/vocal cords/syrinx)
• decision-making in neuronal mechanisms to switch between movements/actions
• variable/stereotyped elements of motor patterns
• rapid responses/oscillatory activity
• coordination/sequences of motor patterns
• aka. SEE W1 VIDEO NOTES

Question 14

CLASSICAL ETHOLOGICAL STUDIES

Answer 14

• fixed (elementary) actions/fixed action patterns (beh action sequences) = highly stereotyped beh responses (ie. greylag geese egg rolling)
• vacuum activity = responses in absence of stimuli

Question 15

TINBERGEN (1952): STICKLEBACKS

Answer 15

• some beh patterns = stereotyped (fixed acts/action patterns); can be triggered by specific stimuli
• sign stimulus (releaser) & releasing values
• testing retrieval beh w/egg pairs; shape/size = critical cues
• see W1 VIDEO NOTES

Question 16

UNDERLYING MECHANISMS

Answer 16

• releaser stimuli can trigger beh output
• ie. herring gull chicks begging response; beak colour preferences

Question 17

ADVOCATING COMPARATIVE APPROACHES: HOPKINS

Answer 17

• neuroethogists believe we can learn gen principles about nervous systems by specialised studying systems
• they learn from animals that experience dif sensory world from our own
• such qs derive introductory survey of neuroethology incl. exotic senses/motor progams/surprising integration

Question 18

ADVOCATING COMPARATIVE APPROACHES: PAPANIKOLOPOULOU

Answer 18

• dorsophilia offer facile/economical whole animal system w/many homologous organs to humans/high functional conservation/established methods of generating/validating human disease models BUT…
• remains relatively underused as drug discovery tool as its relevance to mammalian systems = questionable
• recent exciting success stories using validation strongly suggest fly models should figure prominantly in drug discover pipeline

Question 19

ROOTS OF NEUROETHOLOGICAL RESEARCH

Answer 19

• sign stimuli -> sensory pathway -> innate releasing mechanims (+ biorhythms + arousal inhibition) -> motor pathway -> muscles aka. fixed action pattern
• early ethological concepts of mechanisms underlying beh patterns
• neurobiology unravelling substrates for beh/plasticity

Question 20

BEH PHYSIOLOGY

Answer 20

• study of localisation/release of stereotypes/elementary forms of beh in CNS (ie. von Holst (1939))
• J. Segaar (1961) studies effect of brain lesions on fixed motor beh in 3-spined stickleback

Question 21

BEHAVIOURISM IN SCHOOLS OF EXPERIMENTAL PSYCHOLOGY

Answer 21

• experimental psychology emphasised role of learning/individial experience that influences beh expression (ie. Skinner/Pavlov) BUT…
• focus on input-output relations & discarding role of genetic/epigenetic factors/inheritance

Question 22

QUANTIFYING BEH W/COMPUTATIONAL TOOLS

Answer 22

• machine vision algorithms allow to track fly & monitor posture of body/wings
• high-throughout behavioural screening facilities study of role of genes in social beh in fruitflies (aggression/courtship)

Question 23

SYNAPTIC PROCESS

Answer 23

• at synapses, neuronal signals are transmitted between neurons OR to target tissue/organ under neural control

Question 24

HODGKIN-HUXLEY MODEL (1952)

Answer 24

• model of action potential
• studies on giant axons of squids revealed basic properties of neural signals

Question 25

KANDEL (2000)

Answer 25

- simple neuronal model of aplysia californica includes (20k neurons): 1. buccal/cerebral/pleural/pedal/abdominal ganglion 2. siphon 3. mantle shelf 4. parapodium 5. gill

Question 26

ESCAPE BEHAVIOUR

Answer 26

- stimuli -> afferent neurons -> interneurons/ganglia/brain -> efferent neurons = beh (aka. signal transmission) - reflex responses = very fast - may not require communication w/brain - synapse -> terminal ganglion -> abdominal segments -> nerve cord -> methathoracic ganglion

Question 27

HILL, WYSE & ANDERSON (2008)

Answer 27

- centralisation/cephalisation in evolution of nervous system - neuronal interactions = very similar across animal kingdom; what differs = number of cells, connectivity complexity & nervous system structure

Question 28

WHY ARE BRAINS DIVERSE?

Answer 28

1. COMPARATIVE NEUROANATOMY 2. BEHAVIOURAL PHYSIOLOGY/NEUROETHOLOGY 3. NEUROGENETICS

Question 29

COMPARATIVE NEUROANATOMY

Answer 29

- study brain structures/neuronal connectivity in dif species of selected groups (taxon) within phylogenetic lineage

Question 30

BEHAVIOURAL PHYSIOLOGY/NEUROETHOLOGY

Answer 30

- measure neural activity; link to beh responses w/consideration of dif tasks & species-specific adaptations

Question 31

NEUROGENETICS

Answer 31

- identify neurons & brain areas from dif patterns of gene activity & link to dif tasks & beh responses

Question 32

NORTHCUTT (2002)

Answer 32

- brain-body relations; larger bodies can grow/carry/sustain larger brains - concentrated brain evolution = size-associated variations/allometric effects within phylogenetic lineage (ie. enlargement of whole brain)

Question 33

HALLEY & KRUBITZER (2019)

Answer 33

- mosaic brain evolution = selective size changes in some brain components - human/primate brains have very large neocortexs w/more areas/unique connectivities > other mammals - associated w/larger number of non-primary cortical areas - other areas ie. subcortical (dorsal thalamus) don't change much in size - frontal brain enlargement including thalamus has occurred independently in various vertebrate groups - only largest rodent (capybara) has similar thalamus-to-neocortex as smallest primate - aka. dif evolutionary selection factors can affect only some brain systems and/or whole brain

Question 34

MEASURING NEURAL ACTIVITY

Answer 34

- aka. intracellular recordings - can measure neuronal signals as dif in potential on each side of membrane (units/Volt) by creating electrical circuit w/wired electrodes: 1. inserted inside (intracellular fluid) & outside (extracellular fluid) aka. the neuron 2. placed close outside neuron (extracellular fluid) relative to other tissues elsewhere (extracellular fluid)

Question 35

ELECTROPHYSIOLOGICAL METHODS OF MEASURING NEURAL SIGNALS

Answer 35

- placing electrodes in tissues/dissociated cells -- intracellular/extracellular recordings of membrane potentials (single/multi-unit recordings aka. EMG) - placing electrodes on skin/scalp -- extracellular recordings of membrane potentials (EEG; EMG) - optical methods to measure neural activity ie. optical imaging (Ca^2+imaging; fMRI; MRI; PET) measuring activation of processes correlated w/changes in membrane potential in neurons

Question 36

CAREW (2000)

Answer 36

- dif ways to measure signals from motoneurons to a muscle at neuro-musclar junction: 1. extracellular recording of multiple units 2. intracellular recording from single motoneuron 3. extracellular recording of multiple units from nerve tract (bundle of axons) w/hook electrodes 4. intracellular recordings from muscle fibre 5. EMG

Question 37

BONTONOU & THOMAS (2014)

Answer 37

- sexual communication in drosophilia genus - Fru^m = responsible for orchestrating whole sequence of male's courtship beh - Fru^m = allele of Fru expressed in males - Fru^f = allele of Fru expressed in females

Question 38

DROSOPHILIA: MANIPULATIONS OF NEURAL CIRCUITS UNDERLYING COURSHIP BEH

Answer 38

- knock-out/inhibition of genes in neurons - knock-down/reversibly silence neurons in normally-beh transgenic flies (ie. change in ambient temperature illuminating w/UV-light) - generating/testing gynandromorphs (ie. fly w/mixtures of male/female brain tissues)

Question 39

MANOLI & BAKER (2004)

Answer 39

- median bundle neurons coordinate beh during drosophilia male courtship - fru (fruitless) gene = only expressed in neurons; codes 4 proteins aka. regulatory genes (which control other genes) - GFP = green fluorescent protein; excited by blue/UV light; gene found in jellyfish & other cnidarians (corals/sea anemones); copepods (crustaceans); amphioxus (early vertebrates)