Download CHAPTER 5: SIMPLE NERVOUS SYSTEMS AND BEHAVIOR

CHAPTER 5:
SIMPLE NERVOUS SYSTEMS
AND BEHAVIOR
What are the properties of the CNS of the simplest animals?
Choanoflagellates
Probable animal ancestors,
unicellular, aggregate in groups,
feed on bacteria, similar to some
cells in sponges.
Bilateral
symmetry
Radial
symmetry
Vertebrates
Invertebrates with
no nervous system
Invertebrates with
nervous system
Simple nervous systems: Invertebrates
Gangliar
organization of the
CNS of
invertebrates with
bilateral symmetry.
(Notice the ventral
position.)
Octopus intelligence
http://www.youtube.com/watch?v=T8cf7tPoN5o
Video
The neuron
Axon terminal
(with vescicles)
Hippocampal neuron
stained for spectrin (red)
and tubulin (green).
Synapse
Myelin: evolved independently in vertebrates
and other phyla, apparently several times
(present in earthworms and some shrimp
species). Most invertebrates lack myelin.
Post-synaptic
dendrite
(with receptors)
Neuron # 1
Vescicle with neurotransmitter
Extracellular compartment
(ions, enzymes, etc.)
Receptor
Synapse
Neuron # 2
Neuron # 1
Na+
Neuron # 2
Neurons: Action potentials
http://www.youtube.com/watch?v=ifD1YG07fB8&feature=related
Video
Neurons: Synaptic transmission
http://www.youtube.com/watch?v=9vZI_XKca88
Video
Animal evolution: a simplified view
Sponges
Cnidarians
Planarians Arthropods Mollusks
Vertebrates
Central nervous systems (CNS)
Neurons, diffuse nervous systems
Multicellular animals, no neurons
Diffuse nervous systems in cnidarians
Hydra
*Neural nets.
*No differentiation
between CNS-PNS.
*Neurons have familiar
properties.
Jellyfish
http://www.youtube.com/watch?v=kZYN-a7BXE0&feature=related
Video
Functional properties of cnidarian neurons
Graded potentials
Action potential
Presynaptic
Postsynaptic
Echo
Jellyfish
Basic behaviors
•Simple-system approach
•Reflexes
•Modal action patterns
•Behavioral plasticity (learning)
Animal evolution: a simplified view
Sponges
Cnidarians Planarians Arthropods Mollusks
Vertebrates
Central nervous systems (CNS)
Neurons, diffuse nervous systems
Multicellular animals, no neurons
Simple-systems approach
To study the neural basis of behavior, one approach is to
select a simple behavior and a simple nervous system.
Simple behavior:
•Reflexes
•Modal action patterns
•Habituation
•Sensitization
Pupillary reflex
Patellar reflex
Aplysia californica
http://www.youtube.com/watch?v=Q1KI30JmemU
Video
Simple nervous systems: Mollusks
•Few neurons
•Large neurons
•Stable locations across animals
•Identifiable
Aplysia californica (sea hare)
Basic behaviors
•Simple-system approach
•Reflexes
•Modal action patterns
•Behavioral plasticity (learning)
Reflex: a simple behavior and a simple neural network
A unit of behavior that
includes:
•An input (stimulus),
•Some degree of
processing in the
CNS (monosynaptic,
polysynaptic), and
•An output (simple
response or
secretion).
Patellar reflex
Gill-withdrawal reflex of Aplysia
Gill-withdrawal reflex of Aplysia
Stimulating and
recording electrodes
Gill
Abdominal
ganglion
Siphon nerve
Genital nerve
Pericardial nerve
Water pik
Branchial nerve
Siphon
Basic behaviors
•Simple-system approach
•Reflexes
•Modal action patterns
•Behavioral plasticity (learning)
Modal action patterns
Sequentially organized, species-typical behaviors that once
activated develop in a ballistic manner.
Dorso-ventral
contractions
(escape
response)
Stimulus: jet of
salty water
simulating a
predator
(starfish)
Animal lands at
a distance from
previous
location
MAP in Tritonia
Escape MAP in Tritonia
https://www.youtube.com/watch?v=JCr1b1mJWoU
Video
Basic behaviors
•Simple-system approach
•Reflexes
•Modal action patterns
•Behavioral plasticity (learning)
A conversation with Eric Kandel
Up to 16:30 min
http://www.youtube.com/watch?v=rHx32Erpyfo
Video
A conversation with Eric Kandel: Summary
• In the 1950s there was a family of competing ideas about how memories could
be stored: diffused storage, glial cells, synapses critical.
• Explicit or declarative memory: the recall of information about people, places,
and objects, and it requires the medial temporal lobe and the hippocampus.
• Implicit or procedural memory: perceptual/motor skills, habits, including
classical and operant conditioning, habituation, and sensitization.
• Aplysia: a simple animal, simple nervous system, and simple behavior, a
reduced form of a human brain.
• Short-term vs. long-term memory: preexisting connections and proteins vs.
gene expression, new protein synthesis, and new connections.
• Only those synapses that are active are strengthened.
• Experience can alter whether a gene is turned on or off in a neuron.
• Brain representations depend on experience.
• Survival requires the ability to modify responses through learning.
A tentative classification of learning phenomena
Learning Phenomena
Specific
General
Nonassociative
Associative/Cognitive
•Habituation
•Short term
•Long term?
•Classical conditioning
•Human language
•Instrumental conditioning
•Song learning
•Sensitization
•Short term
•Long term?
•Rule learning
•Imprinting
•Social learning
Properties of habituation
Response Strength
12
10
(3)
8
(1)
6
(2)
4
(2)
2
0
0
6
Resting
period
9 Resting 12
period
Strong12
10
ISI = 60 s
12
ISI = 10 s
10
8
8
8
6
6
6
12
Response Strength
3
4
4
(5)
2
2
2
0
0
0
0
1
2
3
4
(6)
Weak10
4
(4)
15
5 0
1
2
3
4
5
0
1
2
3
4
5
6
7
8 Resting
9 10
period
12
Response Strength
12
10
200 Hz
8
(9)
8
(7)
600 Hz
10
6
400 Hz
4
(8)
6
4
600 Hz
2
0
2
DS
DS
0
0
1
2
3
4
5
6
7
8
0
Habituation Trials
1
2
3
4
5
6
7
8
9
10
11
12
Habituation of the Galvanic skin response in humans
Aplysia’s siphon retraction reflex and learning
https://www.youtube.com/watch?v=yLa-cXg8BwM
Video
Habituation in Aplysia
Habituation in Aplysia: Mechanisms
↓Ca++ influx:
habituation
Habituation of the gill-withdrawal reflex in Aplysia is caused by a decrease in
calcium influx into sensory neuron, which causes a reduction in neurotransmitter
release onto motor neuron, thus decreasing the motor response (gill contraction).
Dishabituation and sensitization in Aplysia
Long-term sensitization
Short-term
sensitization
Short-term sensitization and dishabituation in Aplysia: Mechanisms
↓K+ outflux: shortterm sensitization
(spike broadening)
↑Ca++ influx:
dishabituation
(increased excitability)
Short-term habituation and dishabituation in Aplysia: A cellular model
Morphological changes in long-term habituation and sensitization
Long-term habituation
Long-term sensitization
Normal
Evolution of neural plasticity
Plasticity: peripheral
Lower invertebrates
Body
surface
Effector
Plasticity: peripheral & central
Higher invertebrates
Body
surface
Effector
Plasticity: only in the CNS
Vertebrates
Body
surface
Effector
Excitatory
Plastic