Neurobiology of Behaviour:

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1 Neurobiology of Behaviour: The mechanisms underlying an animal s response to its environment Department of Physiology awitney@tcd.ie

Comparative aspects of nervous systems Human brain has 10 12 neurons, Brain The model systems approach - simpler nervous systems - ecological specialisms Molecular and Cellular similarities: Spinal

2 Comparative aspects of nervous systems Human brain has neurons, Brain The model systems approach - simpler nervous systems - ecological specialisms Molecular and Cellular similarities: Spinal Cord Invertebrate and Vertebrate nervous systems share properties at a molecular and cellular level (eg neurotransmitters) Morphological differences: Vertebrate: spinal cord and brain Invertebrate: segmental nervous system Brain Thoracic Abdominal

3 Typical Neuron Neurons: Cells specialized for processing and transmitting information INPUT Receiving signals Sensory Neurons: Neurons that are specialized to respond to the environment Motor Neurons: Neurons that have axons terminating on muscle fibres Interneurons: All the other forms of neurons Sending signals OUTPUT The Action Potential

4 Moving in the environment: - The Leech: Understanding the neural basis for rhythmic movements like locomotion Learning and adapting to the environment: - The cellular basis for changes in behaviour during learning. - Hebb (1949): Repetitive activity at a synapse could produce lasting cellular changes - Aplysia: Habituation and Classical Conditioning (in the tradition of Ivan Pavlov) Sensing the environment: - The barn owl: Learning to locate prey, formation and plasticity of an auditory map - The weakly electric fish: Electric signals to detect objects in the environment Spatial Navigation: - Changes in brain volume after spatial tasks Control of the Hand: - Primates, the opposable thumb, and development of underlying control Collective Behaviour: - Swarming in Locusts Neurobiology of Animal Behaviour

movements like locomotion, swimming, flight, breathing can occur in the absence of sensory

5 Behaviour is Movement: Central Pattern Generators The Medicinal Leech Hirudo medicinalis Central pattern generators (CPGs) : neural circuits that generate periodic motor commands for rhythmic movements like locomotion, swimming, flight, breathing can occur in the absence of sensory feedback, but are shaped by sensory input Following a rhythmic movement: frameby-frame analysis of swimming

6 Hirudo medicinalis as a model system for understanding CPGs An accessible nervous system A repetitive behaviour, the CPG can be initiated in isolated ganglia An easily elicited behaviour Understanding of CPGs important comparatively across species

7 The Leech: Model systems and Identified Neurons Staining of an identified neuron in the Leech An identified neuron is one that is recognizable as it occurs in the same location and has the same function in every member of a species P, T, N, Rz cells

simple nervous system (20,000 neurons) Large (up to 1 mm in diameter) identified

8 Aplysia californica : A model system for learning and memory Kandel, E.R. (2001) Science Vol 294 pp Aplysia californica, The sea hare Relatively simple nervous system (20,000 neurons) Large (up to 1 mm in diameter) identified neurons Neurons can be identified by position, size, colour and their electrophysiological properties

9 Habituation in Aplysia Gill withdrawal reflex occurs when the siphon or mantle shelf is stimulated. Understanding habituation at a cellular level

org/ Intracellularly record from identified

10 Abdominal Ganglion showing Identified Neurons Intracellularly record from identified sensory neuron and identified motor neuron M S Record membrane potential

11 Habituation of a tactile response Habituation could be -Short term (minutes) -Long term (hours to weeks) Response can be restored through a strong electric shock (sensitisation) Behavioural change is accompanied by changes in the strength of the monosynaptic connections between the sensory and motor neurons Depression at the synapse Changes in behaviour as a result of experience: non-associative learning

12 Classical Conditioning: Aplysia CS (conditioned stimuli) = Siphon Stimulation US (unconditioned stimuli) = Tail Shock CS+US CS UCR CR UR (unconditioned response)= Siphon Withdrawal Siphon withdrawal reflex can be Classically Conditioned Associative Learning: the learning of stimulusresponse relationships

mouse are received by the owl s left and right ears.

13 Auditory Localization in the Barn Owl, Tyto alba Knudsen, E.I. (2002) Nature Vol 417 pp Sound waves generated by movements of a mouse are received by the owl s left and right ears. Space around head relative to line of sight ITD Interaural Time Difference Interaural Level Difference

Prisms Day 42 Day 1 visual field displaced to right Removal Neurobiology:

14 Plasticity of auditory localization in juveniles as a prism vision Behaviour: Head Orientation to visual (purple) and auditory (red) Before Prisms Day 42 Day 1 visual field displaced to right Removal Neurobiology: Influence on neurons in Optic Tectum 8 wks R ear leads Auditory and Visual RF Aligned prism

15 Plasticity shown in the projection from ICC to ICX (central nucleus of Inferior Colliculus to external nucleus of Inferior Colliculus) Spatial distribution of labelled axons for normal juveniles and prism reared adults

The weakly electric fish generates electrical signals to probe the environment.

16 Sensory Processing: the weakly electric fish Gnathonemus petersii How can sensory feedback from self-movement be distinguished from sensory feedback from external source? The weakly electric fish generates electrical signals to probe the environment. The electrolocation commands can be gated, amplified or predicted in the brain by the fish return signal.

Corollory Discharge enabling Sensory Cancellation Gnathonemus petersii senses objects through the distortions they cause in an electric field that it creates.

17 Corollory Discharge enabling Sensory Cancellation Gnathonemus petersii senses objects through the distortions they cause in an electric field that it creates. Modifications to signal occur through corollary discharge mechanisms Similarity with the concept of efference copy Importance in distinguishing self from other Crapse & Sommer (2008) Nature Reviews Neuroscience Vol 9 pp

studied by Professor Brenda Milner (hippocampal lesion; entorhinal cortex +) Phineas Gage injured 1848 - function of the

18 Neurobiology of Human Behaviours Neuropsychological Case Studies Patients with lesions in known brain areas Memory Deficits: The amnesic H.M. studied by Professor Brenda Milner (hippocampal lesion; entorhinal cortex +) Phineas Gage injured function of the frontal lobe Corkin (2002) Nature Reviews Neuroscience Vol 3 p Imaging has enabled the site of brain lesions to be determined. The influence of damage to resulting behaviour can then be studied Reconstruction of the accident of Phineas Gage

19 The hippocampus and spatial navigation Birds: brood parasites, foodcaching Rats in mazes Human taxi drivers

20 The Brown-headed Cowbird, Molothrus ater A brood parasite: The female, but not the male, requires knowledge of nest sites Sherry, DF. (2006) Annual Review of Psychology Vol 57 pp Discovery Communications, LLC.

21 Hippocampal Volume: Comparison of the brown-headed cowbird with non-brood parasites

22 Hippocampal Volume in Taxi Drivers Taxi drivers show a decrease in size of anterior hippocampus Maguire et al (2000) PNAS Vol 97 No 8 pp Taxi drivers show an increase in size of posterior hippocampus

23 Time as a taxi driver and hippocampal volume Changes in size of posterior and anterior hippocampal volume related to time as a taxi driver

A primate special skill: the hand and object manipulation Non-human primates Evolution of the opposable thumb enabling precision grasping Development of descending corticospinal tract

24 A primate special skill: the hand and object manipulation Non-human primates Evolution of the opposable thumb enabling precision grasping Development of descending corticospinal tract Cutaneous afferents Napier, 1970 (a) tree-shrew (contrast) (b) chimpanzee (c,h) hand, foot,a potto (d,i) hand,foot, a tarsier. (e) hand gibbon (f) hand macaque (g,j) foot, gorrilla baboon

25 Witney et al (2004) TINS Vol 27 (10) pp Efference copy

26 Collective Behaviour Final larval instar solitarious and gregarious locusts What triggers locusts to swarm? M. L. Anstey et al., Science 323, (2009) Published by AAAS

27 Serotonin in the thoracic CNS is correlated with the degree of behavioral gregarization Serotonin is necessary M. L. Anstey et al., Science 323, (2009) Published by AAAS

Neurobiology of Navigation in Migratory animals?

unfamiliar territory A magnetic compass?

28 Neurobiology of Navigation in Migratory animals? Migratory animals capable of navigating for long distances in unfamiliar territory A magnetic compass? The underlying neurobiology of long distance migratory behaviour is not well understood. Where might the primary sensory receptor be? What might the receptor be like? Bingman and Cheng (2005) Ethology, Ecology & Evolution Vol 17 pp

29 Neurobiology of Behaviour An animals response to the environment will be influenced by their underlying nervous system Behaviour ultimately can be explained from the cellular properties of and synaptic interactions among sensory neurons, interneurons and motoneurons. Simpler nervous systems (Model systems) are often used to understand how nervous systems evolve to the specific demands of the animal s environment. With a Model Systems approach there is the aim of identifying cellular properties and understanding neural circuits that are the basis for specific behaviours. In humans, neuropsychological case studies have provided important information about overall brain areas implicated in our performance of certain tasks. The neurobiology for some behaviours is not well understood

Behavioral Neurobiology

Behavioral Neurobiology The Cellular Organization of Natural Behavior THOMAS J. CAREW University of California, Irvine Sinauer Associates, Inc. Publishers Sunderland, Massachusetts PART I: Introduction