Nerve Cells & Behaviour Flashcards
1
Q
542-520 MYA
CAMBRIAN EXPLOSION
A
- rise in organism diversity
- rapid appearance of many animal body plans aka. trilobite fossils
- vertebrate origins
2
Q
key questions
BIOLOGICAL PSYCHOLOGY
A
- 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?
3
Q
THE BRAIN: NAKED EYE
A
- 15cm front to back (adult)
- even the largest nerve cells are miniscule and need to be stained to be seen
- cortex = 3mm thick
4
Q
THE BRAIN: LIGHT MICROSCOPE
A
- large nerve cell bodies = 100um (0.1mm) in diameter (x100 magnification)
- large axons/dendrites are about 10um (.01mm) in diameter (x1000 magnification)
5
Q
THE BRAIN: ELECTRON MICROSCOPE
A
- 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)
6
Q
BEHAVIOUR MODEL
A
- 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
7
Q
TINBERGEN (1963)
A
- 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
8
Q
MACHANISMS & ADAPTIVE FUNCTIONS OF BEHAVIOUR
A
PROXIMATE CAUSATION
ULTIMATE CAUSATION
9
Q
PROXIMATE CAUSATION
A
- during animal’s life-time
- how is beh produced?
- how does beh develop?
- how is beh inherited?
10
Q
ULTIMATE CAUSATION
A
- over several generations
- why has a beh developed?
- what selective advantage does it provide?
- what is the evolutionary history?
11
Q
COMPARATIVE APPROACHES ROOTS
A
- roots of comparative approaches/methods in beh/neuroscience research
- focus on systematic comparisons by middle of 20th century
12
Q
ETHOLOGY
A
- “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)
13
Q
BEH = MOTOR OUTPUT
A
- 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
14
Q
CLASSICAL ETHOLOGICAL STUDIES
A
- 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
15
Q
TINBERGEN (1952): STICKLEBACKS
A
- 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
16
Q
UNDERLYING MECHANISMS
A
- releaser stimuli can trigger beh output
- ie. herring gull chicks begging response; beak colour preferences
17
Q
ADVOCATING COMPARATIVE APPROACHES: HOPKINS
A
- 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
18
Q
ADVOCATING COMPARATIVE APPROACHES: PAPANIKOLOPOULOU
A
- 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
19
Q
ROOTS OF NEUROETHOLOGICAL RESEARCH
A
- 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
20
Q
BEH PHYSIOLOGY
A
- 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
21
Q
BEHAVIOURISM IN SCHOOLS OF EXPERIMENTAL PSYCHOLOGY
A
- 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
22
Q
QUANTIFYING BEH W/COMPUTATIONAL TOOLS
A
- 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)
23
Q
SYNAPTIC PROCESS
A
- at synapses, neuronal signals are transmitted between neurons OR to target tissue/organ under neural control
24
Q
HODGKIN-HUXLEY MODEL (1952)
A
- model of action potential
- studies on giant axons of squids revealed basic properties of neural signals
25
KANDEL (2000)
- 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
26
ESCAPE BEHAVIOUR
- 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
27
HILL, WYSE & ANDERSON (2008)
- centralisation/cephalisation in evolution of nervous system
- neuronal interactions = very similar across animal kingdom; what differs = number of cells, connectivity complexity & nervous system structure
28
WHY ARE BRAINS DIVERSE?
1. COMPARATIVE NEUROANATOMY
2. BEHAVIOURAL PHYSIOLOGY/NEUROETHOLOGY
3. NEUROGENETICS
29
COMPARATIVE NEUROANATOMY
- study brain structures/neuronal connectivity in dif species of selected groups (taxon) within phylogenetic lineage
30
BEHAVIOURAL PHYSIOLOGY/NEUROETHOLOGY
- measure neural activity; link to beh responses w/consideration of dif tasks & species-specific adaptations
31
NEUROGENETICS
- identify neurons & brain areas from dif patterns of gene activity & link to dif tasks & beh responses
32
NORTHCUTT (2002)
- 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)
33
HALLEY & KRUBITZER (2019)
- 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
34
MEASURING NEURAL ACTIVITY
- 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)
35
ELECTROPHYSIOLOGICAL METHODS OF MEASURING NEURAL SIGNALS
- 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
36
CAREW (2000)
- 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
37
BONTONOU & THOMAS (2014)
- 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
38
DROSOPHILIA: MANIPULATIONS OF NEURAL CIRCUITS UNDERLYING COURSHIP BEH
- 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)
39
MANOLI & BAKER (2004)
- 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)
