Brain & behaviour PDF

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Lecture 1: Historical perspectivesThe brain: ● Made up of neuronsTrepanning: ● Process of cutting into the skull ● Believed to be for medical treatment ● Used thousands of years ago3000BC Ancient Egyptians wrote about treatments for brain damage, observed that damage to one hemisphere of the brain a...

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Lecture 1: Historical perspectives The brain: ● Made up of neurons Trepanning: ● Process of cutting into the skull ● Believed to be for medical treatment ● Used thousands of years ago 3000BC Ancient Egyptians wrote about treatments for brain damage, observed that damage to one hemisphere of the brain affects movement/sensation on the contralateral (other side) of the body Hippocrates: ● 460 - 377 BC ● Greek physician ● Argued the brain supports the mind and behaviour ● Argued epilepsy was caused by dysfunction of the brain Plato & Aristotle: ● Plato - 439-347 BC, argued reason & perception lay in the head, emotions in the heart & lungs, liver & guts ● Aristotle - 384-322 BC, argued sensations & control is governed by the heart, and the brain served to cool the blood Galen: ● 129-199 AD ● Greek physician in Rome ● Argued against Aristotle ● Dissected bodies in Rome ● Argued the brain was responsible for sensation & behaviour Ibn Al-Haytham (Alhanzen): ● 965-1040 AD ● Arabian scholar ● ‘Father of optics’ - ‘how we see’ ● Argued the brain is where we truly see the world Andreas Versalius: ● 1514-1564 ● Anatomist, used diagrams ● Renaissance Italy ● Wrote the De humani corporis fabrica (On the Fabric of the Human Body) - an influential anatomy guide ● Argued the ventricles were crucial for sensation & movement

Rene Descartes: ● 1596-1650 ● Argued the ‘soul’ was separate from the body ● Sense of free will ● Pineal gland key seed of consciousness

Luigi Galvani: ● 1737-98 ● Italian physician & physicist ● Discovered that electrical stimulation of a dead frog leads to ‘reanimation’ of the limbs ● CNS runs through electricity Johannes Peter Müller: ● 1801-1858 ● German physiologist, comparative anatomist ichthyologist (study of fish) & herpetologist (study of amphibians) Franz Francis Gall: ● 1758-1828 ● Argued that specific functions are localised to different regions of the brain ● Phrenology - people with larger regions were better at that function (highly disproved) Jean Pierre Flourens: ● 1794-1867 ● French physiologist ● Founder of experimental brain science ● Found no evidence for the phrenologist’s view of functional specialisation (i.e. that language in the brain under the eye) Paul Broca: ● 1824-80 ● French anatomist, physician & anthropologist ● Discovered ‘Broca’s area’ in the frontal lobes - in the left hemisphere, responsible for speech production ● Established the dominance of the left hemisphere for language Carl Wernicke: ● 1848-1905 ● German anatomist & physician ● Discovered ‘Wernicke’s area’ - in the posterior temporal lobe, responsible for language comprehension John Hughlings Jackson: ● 1835-1911

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Insights in cerebral function from the study of brain damaged patients

Ferrier, Fritsch, Hitzig: ● Used electrical stimulation in the cortex to reveal the organisation of the motor cortex in animals Camillo Golgi & Ramon y Cajal: ● Advances in the understanding of neurons using microscopes & staining methods ● Golgi argued neurons were not individual entities but a collective mass ● Cajal argued neurons were separate (neuron hypothesis) and provided insights into how cells might participate in learning Hermann von Helmholtz: ● 1821-1894 ● German physician & physicist who made significant contributions to widely varied areas of science ● Physiology & psychology - known for his mathematics of the eye, theories of vision, ideas on the visual perception of space, colour vision research and on the sensation of tone, perception of sound, and empiricism Charles Scott Sherrington: ● 1857-1952 ● Work on reflexes & general principles of the nervous system Wilder Penfield: ● 1891-1976 ● Canadian neurosurgeon ● Developed a method for stimulating the brain during surgery to determine regions to avoid resecting ● Mapped out the human motor and somatosensory cortices Brenda Milner: ● Discoveries about the nature of memory and cognition from studying neurosurgical patients e.g. HM

Lecture 2: Basic neuroanatomy Brain myths: ● ‘The adult brain doesn’t grow any new nerve cells’ - certain regions grow new neurons throughout life ● ‘We only use 10% of our brain - we use all of it ● ‘Left-brained people are rational & methodical but right-brained people are creative’ - both hemispheres contribute to creativity & rationality Sperm whales have the biggest brain Organisation of the nervous system: ● CNS - brain & spinal cord ● PNS - (connects the CNS to the limbs & organs) contains somatic nervous system (controls muscles & movement) & autonomic nervous system (controls internal organs & glands) ● There is also an enteric system in the PNS which controls the gut Directions in the brain: ● Dorsal is superior (upwards) ● Ventral is inferior (downwards) ● Dorsal is also posterior (right) ● Ventral is also anterior (left) ● The spinal cord runs vertically ● Medial is the middle parts ● Caudal is the back & rostral is the front ● Coronal plane, sagittal plane, axial plane - the ways you can cut through the brain Human brain: ● Frontal lobe (front) ● Parietal lobe (behind frontal) ● Occipital lobe (back) ● Temporal lobe (side) CNS: ● Cerebral hemispheres & diencephalon known as forebrain - hippocampus & amygdala also sit in the forebrain ● Diencephalon - contains the thalamus & hypothalamus (hypo meaning lower) ● Thalamus - processing pathways for sensory information and linking cortex & cerebral hemispheres ● Pons & cerebellum (hindbrain) - pons connects the medulla & midbrain, the cerebellum has densely packed neurons which plays a part in balance, fine motor control, timing ● Pons, medulla & midbrain (brainstem) - form the brain stem which connects the spinal cord into cerebral hemispheres ● Medulla - critical for temperature regulation, breathing

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Spinal cord - has 4 regions, cervical, thoracic, lumbar, sacral

PNS (peripheral nervous system): ● Cranial nerves ● Spinal nerves ● Peripheral ganglia ● Encased by vertebral column Gyri are the bumps in the brain Sulci are the gaps in the brain Sylvian Fissure separates the frontal and temporal lobe, it is the most important groove/gap in the brain Gyri and sulci: ● These are all mirrored in each hemisphere unless stated otherwise ● Precentral sulcus - in front of the precentral gyrus, involved in movement (primary motor cortex) ● Precentral gyrus - in front of the central sulcus, involved in senses (primary somatosensory cortex) ● Central sulcus - on each hemisphere, divides the frontal lobe from the parietal lobe ● Postcentral gyrus - behind the central sulcus ● Postcentral sulcus - behind postcentral sulcus ● Superior frontal gyrus - at the front of the brain, top of the head ● Middle frontal gyrus - behind superior frontal gyrus ● Inferior frontal gyrus - has the orbital part, triangular part, opercular part which are important in speech production (left hemisphere) ● Inferior parietal lobule - above superior ● Intraparietal sulcus - the gap between the lobules ● Superior parietal lobule - important for organising representations of the world ● Supramarginal gyrus - processes information ● Angular gyrus - processes information ● Occipital gyri - has superior and inferior ● Primary auditory cortex - part of the cerebral cortex, curves round the temporal lobe, processes sound information, in the left hemisphere ● Insular cortex - part of the cerebral cortex, receives sensory information from environment, links sensory experience and emotional valence, in the left hemisphere ● Fissures are also used to describe the gaps (gyri) in the brain ● Calcarine fissure - at the back of the brain, where the primary visual cortex is Ventricles are fluid-filled spaces within the brain Meninges: ● Surround the spinal cord & help protect the brain ● Between the skull & cerebral cortex ● Three layers - pia mater (protects brain tissue), arachnoid (allows cushioning),

dura mater (2 layers, protects contact between brain & skull) Brodmann’s areas: ● Way of dividing the cerebral cortex ● A numbering system for different areas ● The largest area of neurons sit in area 4 Dividing up the brain: ● White matter vs gray matter - to look at these, staining techniques can be applied (nissl for gray and myelin stain for white), white matter is the pathways of the neurons which connect each other ● Cortex vs subcortical nuclei ● Nuclei vs ganglia The limbic system: ● Contains a range of subcortical structures ● Contains amygdala & hippocampus ● Hippocampus curves round & connects into the mammillary bodies ● Mammilary bodies send projections out through the cingulate cortex ● The cingulate gyrus is in the cortex Basal ganglia: ● Deeper structures ● Thalamus & substantia nigra sit outside the basal ganglia ● Globus pallidus - control conscious and proprioceptive movements ● Caudate nucleus - plans the execution of movement ● Putamen - connected to the substantia nigra and globus pallidus, regulates movements and influences various types of learning ● Caudate nucleus & putamen can be grouped as striatum ● Lateral medial Deeper into the brain: ● Superior colliculus (role in visual processing) & inferior colliculus (role in auditory processing) form key parts of the midbrain ● Cerebral aqueduct - cerebral spinal fluid flows through this ● Reticular formation - groups of cells linked to arousal functions ie sleep ● Red nucleus - in front of the reticular formation, involved in motor control alongside substantia nigra ● White matter surrounds all of these ● Corpus callosum - communication between the two hemispheres, white matter Ventricles: ● Fluid-filled spaces in the brain known as cerebral spinal fluid (CSF) ● Four in the brain ● 2 lateral ventricles ● If the fluid gets obstructed you can get hydrocephalus - a buildup of fluid which puts pressure on the brain

Autonomic nervous system: ● Sympathetic nervous system ● Parasympathetic nervous system FOUR GROUPS OF NEURONS IN THE BRAIN Distribution of noradrenaline in the brain: ● Adrenaline regulates heart rate & is involved in fight or flight ● Noradrenaline is linked to adrenaline production ● Locus ceruleus is a nucleus which contains neurons project out into the spinal cord and cerebellum innovating (connecting onto) axons, involved in stress, releases noradrenaline Distribution of dopamine in the brain: ● Ventral tegmentum - a nucleus in the midbrain, sends projections on the mesocortical pathway & the mesolimbic pathway ● Mesocortical pathway - projects mostly to the frontal cortex ● Mesolimbic pathway - projects mostly to the limbic striatum (part of basal ganglia) Distribution of acetylcholine in the brain: ● Pedunculopontine nucleus - projects to the thalamus ● Nucleus basalis - projects to the neocortex, in the base of the front of the brain ● These two release acetylcholine Distribution of serotonin in the brain: ● Raphe nuclei ● Range of nuclei run down the spine ● Sends a range of information into the cortex, cerebellum ● Serotonin is a modulator eg in mood, but also in social bonding, food regulation, learning

Lecture 3:

Neurons & glia Why do we have neurones? ● Neurones allow centralised and plastic control of the body ● Imagine touching a hot iron - sensory neuron detects heat, sends a signal through spinal cord, forms connection with motor neuron, which instructs arm muscle to move ● Allows the body to respond Neurones are not the only cell in the brain: ● Adult male human brain contains on average 86.1 billion neurones ● 84.6 billion non neuronal cells ● Neurones - excitable cells that can send signals over long distances ● Microglia - essentially the immune system of the brain & spinal cord ● Astrocytes - non-excitable (cells that do not generate action potentials) cells which maintain the local ionic environment (energy), provide metabolites to neurones, modulate synaptic efficacy, and link neurones to blood supply Neurones being excitable cells: ● Capable of integrating & propagating signals rapidly (1ms for an action potential) ● Distinct zones for input (dendrite) and output (axon) allowing directional flow of information ● Form hierarchical networks capable of rapid processing & high spatial precision, allow brain to compute Astrocytes being non-excitable cells: ● Slow signals (3s) propagate within astrocytes via calcium ions, which modulate neuronal excitability ● Connect to each other via gap junctions which allow flow of current (but not macromolecules) ● Form syncytical networks that modulate slowly ● Astrocytes & brain homeostasis - send processes out from blood vessels and neurones, take up from blood vessels energy supply, can control size of blood vessels Glia in brain function: ● Glia means glue ● Neuroglia - provide physical support, control nutrient flow, involved in phagocytosis ● Astrocytes - provide physical support, remove debris (phagocytosis) & transport nutrients to neurones, help maintain brain homeostasis ● Phagocytosis is the process whereby a phagocyte (type of white blood cell) engulfs a foreign particle (often a pathogen) and breaks it down ● Microglia - involved in phagocytosis & brain immune function ● Oligodendrocyte - provide physical support & form the myelin sheath around axons in the brain ● Schwann cells - form of oligodendrocyte which form myelin for peripheral axons Oligodendrocytes: ● Form the myelin sheaths necessary for fast neural signaling

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Form around axons but leave gaps which speeds up transmission Multiple sclerosis - a demyelinating disease which breaks down myelin sheaths & nerve impulses can no longer be transmitted effectively

The function of the brain & nervous system is to receive, transmit & process signals How the electrical signals of neurons are recorded: ● A piece of neural tissue would be placed in a bath full of salty liquid ● Two electrodes are placed in this bath, one inside the axon & one outside the axon ● These two signals are measured ● The difference between these two signals is compared by a voltmeter ● Voltmeter measures the potential difference between the plus & minus poles of a battery by the light that is produced Ions: ● ● ● ● ● ● ● ● A cell: ● ● ● ●

Need understanding of this to understand why a potential difference is produced Ions are atoms or molecules that have lost or gained one or more electron Electrons are negatively charged Cations - ions that have lost electrons, positively charged Anions - ions that have gained electrons, negatively charged Salts - solid substances made of ions, always contain equal numbers of positive & negative charges When salts are dissolved in water, positive & negative ions separate and move about freely Some are intracellular & others are extracellular Has a cell membrane Inside the cell is the intracellular space Outside the cell is the extracellular space The membrane is formed of fats & proteins (channels) which form pores in the membrane, allowing ions to move in and out

At rest, neurones are polarised, meaning there is a potential difference between the inside and outside of the cell, when the difference gets larger, the cell is polarised Membrane potential can be recorded using an electrode. The resting membrane potential (-70 millivolts mV) describes the potential difference across the membrane of excitable cells in between action potentials. More specifically, the resting membrane potential references the intracellular potential to the extracellular potential of nerve and muscle cells at rest Resting membrane potential is a result of: ● Differences in ionic concentrations between the inside & outside of the neuron ● Ion channels in the neuronal cell membrane that only allow certain ions to pass in and out of the neuron ● The resting potential requires energy to activate the sodium potassium ion pump - brings 2 potassium ions & 3 sodium ions out of the cell, which results in a net increase in positive charge outside the cell

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This pump is always active and uses energy in the form of ATP to exchange the ions This sets up concentration gradients for potassium & sodium, and provides the resting potential

Resting membrane potential: ● Allows neurones to be excited ● When a stimulus is applied, the resting membrane potential is added to by small excitatory postsynaptic potential, which causes the RMP to move slightly closer to 0 ● Once it reaches a threshold, there is a massive influx of sodium ions which changes the polarity of the cell membrane & makes the inside of the cell positive ● Followed by a recovery ● At this threshold of excitation, a group of sodium channels open (voltage gated), sodium iols flood into the cell, depolarising the cell even further ● Sodium channels close, potassium channels open, causing the membrane potential to return to its resting level How does generating this action potential help neurones signal? ● When the action potential happens in one part of the membrane, it causes the neighbouring part of the membrane to slightly depolarise ● This causes an action potential in the neighbouring signal and so forth ● Myelin sheath speeds this process up by helping the signals jump ● Process of jumping speeds up the transmission from soma to synaptic terminals An action potential is generated between the cell soma & the axon The action potential propagates down the axon towards its endings (terminal buttons) Between a presynaptic terminal button and postsynaptic cell is a synapse An action potential causes an influx of calcium ions into the presynaptic space, which causes the release of neurotransmitters into the synaptic cleft There are specialised receptors for neurotransmitters, when receptors open they allow an influx of ions across the cell membrane Two most important neurotransmitters are glutamate (excitatory) & GABA (inhibitory) The receptors for glutamate allow for positive ions into the postsynaptic neuron (which causes membrane potential to get closer to 0 aka depolarise) The receptors for GABA allow for negative ions into the postsynaptic neuron (which causes membrane potential to go further from 0 aka hyperpolarise) The postsynaptic neuron has to synaptics, one excitatory and one inhibitory, so one releases GABA and the other releases glutamate If only the excitatory inputs are active, the signals propagate to the axon hillock, if the inhibitory is active at the same time as excitatory the threshold is not met so action potential is not made Lecture 4: Neurotransmitters

Why do drugs work? ● Cocaine blocks the reuptake of dopamine after its release at a synapse ● Cocaine - blocking these transports increases dopamine in synapse, increasing activation and thus reward, sustained activation of dopamine receptors leads to reduction in dopamine receptors, creates a tolerance, leading to withdrawal but also a need for more cocaine in order to gain the same effects ● Cocaine has to reach a threshold to be effective ● Effect of a drug depends on its concentration ● Dose-response curve ● There is a point where no matter how much you take of a drug, increasing the dose will not produce a stronger effect ● Different effects occur at different concentrations eg morphine can ease pain but too much can have a negative effect on respiration ● Size of action of drugs is usually at the synapses between neurones ● They effect brain activity by changing the strength or duration of the release from presynaptic neurone ● They also can change the strength or duration of the effect on postsynaptic neurones ● Different circuits within the brain express different types of neurotransmitters ● Each circuit has a neurochemical signature Neurotransmitters & their receptors: ● Neurotransmitters - made & stored in the presynaptic neuron, are released at the presynaptic terminal when stimulated and produce a response from the postsynaptic neuron ● Neurotransmitter receptors - activated by a neurotransmitter, change the flow of ions into the postsynaptic neuron, either directly (ionotropic) or indirectly (metabotropic) ● Each neurotransmitter may have several receptors, which are expressed in different neurons Probably every neurone is sensitive to both glutamate & GABA Neurotransmitter reuptake: ● If neurotransmitters remain in the synapse, their effect will continue ● Neurotransmitter reuptake removes the neurotra...