Lecture #4 - Biology of Behaviour

Nervous system 07/10/2015

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Biological basis of behaviour

Announcements

• Movember

– Iwill support any person in the class who joins a team

• Thanksgivingthank your parent(s)

Announcements

• Regenesis

– If you are a undergraduate or graduate student, please support our work by taking 20 seconds of your time to cast your vote in support of Regenesis at: evote.yorku.ca

• A teaching moment – critical thinking & the federal election

Social Psychology in Action

• How the media & politicians shape political debate

– How many of you have heard about the debate about the niqab during the federal election campaign?

– How many of you have heard about the debate about aboriginal issues during the federal election campaign?


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Social Psychology in Action• Availability heuristic

– A mental shortcut that relies on immediate examples (usually visual) that come mind when evaluating a specific topic, concept, or decision.

– Not just in Canada, not just one party

Communication in the Nervous System

• neurons (nerve cells): workers ‐‐transmit info

glial cells: bodyguards -- feed & protect

Structure of a Neuron• Dendrites

– receive info from other neurons and transmits to cell body.

• Cell body– contains nucleus; decides “to fire or not to fire”

• Axon

– conducts impulses (fire signal) away from cell body

Structure of a Neuron

Myelin Sheath fatty insulation from glial cells surrounding axon

multiple sclerosis: loss of myelin causes erratic signals


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Recent views on neurons• neurogenesis: production of new neurons from immature stem cells– immature cells can develop into any cell type in the appropriate environment

• Mirror neurons– Neurons activated by performing an action or “seeing another” perform the same action

• little progress in understanding the function of mirror neurons

• overemphasis on the studying actions?

How Neurons Communicate

• axon terminals release neurotransmitters

• neurotrans. enters synaptic gap

• neurotrans. binds to receptors that it fits

• Excitatory signal (pos) Fire!

• Inhibitory signal (neg) Hold your fire!

Action Potential• Cell at rest (resting potential): polarized membrane (neg. molecules/ions inside & pos. outside)

• Cell body averages out signals & decides if it should fire.

• Cell in action (action potential ‐‐ AP): membrane depolarised & pos. sodium ions flood in

• AP is an electrical signal that follows an all‐or‐none law (same strength); the intensity of stimulation is determined by the rate of firing

From Postsynaptic Potentials to Neural Networks

• One neuron gets signals from thousands of others

• Requires integration of signals– PSPs (+ & ‐) add up

• Neural networks– patterns of neural activity: interconnected neurons that fire together or sequentially

• Synaptic connections– elimination and creation: synaptic pruning


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Estimated number of synapses in the human visual cortex as a function of age.

Neurotransmitters

• Specific neurotransmitters work at specific synapses

– lock & key (binding)

• Agonist – chemical that mimics action of a neurotransmitter

• Antagonist – opposes action of a neurotransmitter

Neurotransmitters

• Acetylcholine (ACh): muscle control, but also memory & emotion

– Agonist – nicotine

– Antagonist – curare

Neurotransmitters – The monoamines

Dopamine: movement; learning; emotion

Parkinson’s -- dopamine degeneration

Schizophrenia – dopamine hypothesis

Norepinephrene: mood & arousal

Serotonin: sleep & wakefulness; appetite; agressionProzac (antidepressant) – serotonin circuits


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Neurotransmitters – The amino acids

GABA Gamma-aminobutyric acid

Inhibitory PSPs

Glutemate Excitatory PSPs

Other chemical messengers

• Endorphins (endogenous opioid peptides): natural opiates – reduce pain & increase pleasure by altering neurotrans. activity

• Hormones produced by glands (e.g., pituitary, pineal) in the endocrine system, for (slow) control of general systems through bloodstream– Oxytocin – reproductive beh., bonding, trust

– Melatonin – biological rhythms

Structure of the Nervous System The Central Nervous System

• Brain

• Spinal cord

– from the base of the brain down the center of the back.

– protected by spinal column.


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The Withdrawal Reflex Peripheral Nervous System

• Somatic

– nerves connected to sensory receptors & skeletal muscles

– afferent (incoming) & efferent (outgoing) nerves

• Autonomic

– sympathetic systemmobilizes resources & increases energy during emotion and stress

– parasympathetic system operates during relaxed states & conserves energy

The Autonomic Nervous System

Emily Dickinson

The Brain – is wider than the Sky –For – put them side by side –The one the other will containWith ease – and You – beside –

The Brain is deeper than the sea –For – hold them – Blue to Blue –The one the other will absorb –As Sponges – Buckets – do –

The Brain is just the weight of God –For – Heft them – Pound for Pound –And they will differ – if they do –As Syllable from Sound –


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Mapping the Brain

• Lesion method

• Electroencephalogram (EEG)

• Electrical stimulation of the brain (ESB)

– Transcranial magnetic stimulation (TMS)

• Computerized tomography (CT scan)

• Positron‐Emission tomography (PET)

• Magnetic resonance imaging (MRI & fMRI)

Lesion method

• Lesion: abnormality from trauma (e.g., concussion), disease or intentional neurosurgery

Computerized tomography ‐‐CT scan

• high def ‐‐ bony structures & soft tissues

• organs: brain, muscles, joint structures, veins & arteries

• anomalies: tumors & hemorrhages

Positron‐Emission tomography (PET)

• 3‐d images of blood flow & chemical reactions

• measures use (metabolization) of glucose & oxygen in brain

• more active brain areas ‐‐ increased blood flow & more oxygen consumption

Normal Alzheimer's


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functional Magnetic resonance imaging fMRI

• uses magnetic field, radio frequency pulses & computer to produce detailed pictures of organs, soft tissues, bone, etc.

• measures tiny metabolic changes taking place in active part of brain

Axial slice renderings of mean activations (red/yellow scale bar) and deactivations (blue/green scale bar) associated with improvisation during Scale and Jazz paradigms

Anatomy of the Brain – greatest hits

• The brain stem

• The cerebellum

• The thalamus

• The hypothalamus and the pituitary gland

• The amygdala

• The hippocampus

• The cerebrum and lobes of the cerebral cortex

Hindbrain• Pons ‐‐ sleeping, waking & dreaming.

• Medulla ‐‐ automatic functions (breathing, heart rate, …)

• Cerebellum ‐‐Regulates movement and balance

• Mnemonic: Medusa bless her heart, cerebrates her dance on the ponds of her dreams

Midbrain

• between hind. & forebrain

• dopamine synthesis (movement)

• Reticular formation –arousal


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Forebrain• Thalamus ‐ relays sensory messages to the cerebral cortex

• Hypothalamus – basic drives (hunger, thirst, sex)

• Limbic system – network involved in emotion, motivation, & memory

• Amygdala ‐ emotion regulator

• Hippocampus ‐ gateway to memory (the case of H.M.)

Forebrain

Mnemonic: Thalma the traffic cop & sex hungry hypo-Louise forgot to set up their hippocampus in the Lymbic system and they cried their amygdalas out.

The Cerebrum

• Largest structure of forebrain

• Upper part of brain that is divided into two hemispheres connected by the corpus callosum.

• In charge of most sensory, motor and cognitive processes.

• Surrounded by cerebral cortex (3 mm of layers of dense grey cells) that can be divided into four lobes (per hemis.)

Lobes of the Cerebral Cortex• Occipital lobes

– Visual cortex.

• Parietal lobes

– Somatosensory cortex.

• Temporal lobes

– Memory, perception, emotion and auditory cortex.

– Left lobe, Wernicke’s area

• Frontal lobes

– Emotion, planning, creative thinking and motor cortex.

– Left lobe, Broca’s area


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Lobes of the Cerebral Cortex Adaptiveness – Echolocation & the blind

• Daniel Kish

• Where does it happen in the brain?

Hemispheres & Corpus Callosum

• Millions of axons connecting hemispheres

• pathway for communication

• severed for treatment of severe epilepsy

Hemispheric specialisation

Left hemisphere

Broca’s area (1861) -- left frontal lobe handles speech production

Wernicke’s area (1874) -- left temporal lobe deals with language comprehension

Right hemisphere: spatial abilities, facial recognition, & creativity


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THE “SPLIT” BRAIN• 1953: Myers & Sperry sever corpus callosum (c.c) in cats

• 1960s: c.c. severed in humans with severe epilepsy (split brain patients)

• 1970s: Sperry conducts studies with patients (N.B. neural connections crossed)

• 1981: Sperry wins Nobel prize

http://ca.youtube.com/watch?v=lfGwsAdS9Dc

Split‐Brain ExperimentHemispheric specialisation

• studies based on assumption of right handedness

• data from left handers is mixed

• handedness may exist on a continuum


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Handedness

• 1 – right only

• 2 – right usually

• 3 – both hands

• 4 – left usually

• 5 – left only

1. Draw?2. Ball throwing?3. Bread slicing?4. Match holding?5. Hair combing?6. Lid removal?7. Teeth brushing?8. Cutting?9. Spoon holding?10. Sweeping (top hand)?11. Writing?

Are There “His” and “Hers” Brains?

• small diffs between gender groups

• larger differences within groups.

• sex diffs in lateralization of language?

– not always replicated

– no support in meta‐analyses

• sex differences in brain could be the result rather than the cause of beh. diffs

Critical thinking: The allure of neuroscienceWeisberg et al, in 2008

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Lecture #4 - Biology of Behaviour