B&B Principles of Neuroscience PDF

lOMoARcPSD|50486287 B&B Principles of neuroscience Brain & Behaviour I (University of York) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Miriam Tucker ([email protected]) ...

lOMoARcPSD|50486287 B&B Principles of neuroscience Brain & Behaviour I (University of York) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 B&B – principles of neuroscience Lecture 1 A history of the brain The link between mind and brain – ancient world The trial of Galileo – came up with the idea that all planets revolve around the sun The ancient egyptians – described how damage to the brain results in behavioural changes – found damage to the left side of the brain results in disturbance to the senses/movement in the right side of the body (and vice versa) – brain wasn’t preserved – wasn’t seen as a useful organ for the afterlife Plato, Aristotle and the soul – Plato divided the soul into 3 parts; rational thinking, emotional/spirited behaviour and desire (particularly sexual) – Aristotle 3 parts; rational thinking, imagination/cognition and memory – thought the soul resided in the heart and was separate from the brain Hippocrates, Galen and materialism – Hippocrates thought everything arose from the brain and the brain alone e.g pleasure, sorrow – with it we think and understand, see and hear etc – Galen noticed damage to the brain often caused behavioural effects – found there were some cavities in the centre of animal brains (ventricles) – thought there were animal spirits in these ventricles The link between mind and brain (renaissance) Leonardo, Michaelangelo and the renaissance – Leonardo Da Vinci drew a diagram of a brain influenced by Galen – ventricles in charge of senses, imagination/cognition and memory – Michaelangelo painting that looks a bit like the brain (hidden message of the link between mind and brain) Descartes – aware theres a brain and a mind but they are separate and need to be joined together (dualism) – thought pineal gland (in centre of brain) was the link between the mind and brain, thought animals had a brain not a mind, so aren’t capable of high level thinking, people with psychiatric conditions lost their connection between the mind and brain The relationship between structure and function in the brain Father Willis – father of neuroscience anatomy of the brain book – images of the brain – came up with names of parts we still use today e.g cerebral cortex and thought corpus collosum was location for rational thinking and that the cerebral cortex was a region for memory – early stages of our modern understanding of the brain Gall, phrenology and localization of function – had idea that different locations of the brain served different functions – thought that if certain parts of the brain were doing more they would grow more Equipotentiality (idea that all of the brain is involved in all behaviour) – a direct challenge to functional localization Animals to solve tasks e.g maze – once they solved complex task they made lesions to the brain – wanted to know if the lesions had to be in specific areas of the brain to affect behaviour or whether It was the size of the lesion (location or size) Conclusion – it was the SIZE of the lesion that was critical, not the location – challenged the idea of localization Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Brain lesions reveal distinct behavioural deficits Broca – came across a patient called Tan – could only say Tan – had a lesion on the left side of the brain Wernike – found someone with damage to this part of the brain (also on the left hand side) Wernike’s area – unable to understand language Broca came to the conclusion we speak with the left hemisphere Phineas Gage – worked on a railway in the US – iron bar pierced his brain – wasn’t the same person after the accident – used to be respectful, didn’t swear or drink, after he was unreliable, disrespectful, swore etc – made poor decisions, lost his job Golgi, Cajal, Brodmann and neuron doctrine Golgi discovered a way of looking at neurons in the brain (golgi’s stain) – gave us insight into the way the brain works – thought as the neurons were all connected the brain acted as a whole Cajal – saw bulges inbetween neurons – concluded that what he was seeing were individual nerve cells/neurons that were connected to eachother via the synapse – suggested there could be localization of function Brodmann – looked at the arrangement of neurons in the brain in different regions – came up with concept of cytoarchitecture (meaning cell arrangement) – noticed that the cytoarchitecture was very different in different parts of the brain – labelled the different regions with numbers – concluded that different regions of the brain were doing different things Techniques in cognitive neuroscience Single neuron recordings Involves recording from single neurons using a very thin electrode that is placed inside the brain – mostly done in animals as is invasive Hubel and Weisel – animal asked to maintain fixation on a point on the screen while a light is shown in different locations – many trials which are then averaged – histogram of number of responses that occur after stimulus onset (counted no. of times an action potential was produced – spikes per second) – after stimulus onset there was a large number of responses – indicates that this neuron is responsive to this location in the visual field (where the light is) Quiroga et al – people undergoing surgery where different parts of the brain are removed e.g epilepsy – neurons that responded to different views of the same person Electroencephalography (EEG) and Magnetoencephalography (MEG) EEG – measures the electrical activity directly – non-invasive (involves recording not stimulation) – although not best equipped for detecting the location of neural activity MEG – measures the magnetic fields that derive from the electrical responses in the brain EEG – record responses from electrodes on a cap on the head of pp whilst the pp does something – stimulus/activity repeated many times – average the activity over many trials to give us and ERP (event related potentials) (indicates changes in activity) Libet - Pp has hand on space bar which is pressed down – at certain time asked to look at clock face and asked to indicate at which point they had an urge to move (remove their hand Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 from the space bar) – found activity was already high at the point where they had an urge to move – the onset of having the urge to move occurs before we have the conscious awareness of moving – we may not be in charge of our conscious decisions Functional neuroimaging: fMRI, PET PET uses radioactive tracer injected into bloodstream Based on the idea that the brain has localization of function Each part of the brain receives an independent blood supply If a part of the brain becomes active it uses a lot of energy which needs to be replenished Increases in brain activity -> increase in blood flow -> increase in fMRI/PET signal Can see increases and decreases in activity in different locations of the brain – gives us an idea about which parts of the brain are doing what and when they are doing them Transcranial magnetic simulation – TMS Allows us to make temporary lesions in the activity of a particular location in the brain A magnetic field is generated that penetrates into the skull – causes a disruption in the electrical activity in a particular location of the brain – we can determine whether that activity disrupts a certain behaviour A magnetic coil is placed above the motor cortex (region of the brain that controls our movements) – can move the coil over different parts of the motor cortex and disrupt movements of different parts of the body depending on where the location is of the TMS coil Techniques vary in spatial and temporal resolution – there are pros and cons to each one Lecture 2 The resting membrane potential Electrical signals in the brain – a historical perspective Idea that fluids flow along nerve cells and that’s the way information is passed from one place to another Galen – idea of animal spirits Descartes – thought fluid would flow down nerve cells – would cause muscles to get bigger – why muscles contract Galvani – deduced electrical signals were important for transmitting information Penfield – neurosurgeon – taking out parts of brain that caused epileptic seizures – record from different parts of the brain to work out if they were responding normally – leave the normal functioning parts alone and take out the disease parts – discovered what we now know as primary motor cortex (involved in moving the body) and primary somatic sensory cortex (involved in getting sensations from the body) – when stimulated the motor cortex an area would twitch or move, when stimulated the somatic sensory cortex people reported sensation of being touched in certain areas Voltage gated sodium ion channels crucial for neuronal communication - liver of puffer fish contains toxin that blocks this so you die Neuron Axon – sending information Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Dendrites – receiving information Neuronal membrane: – ion channels present – allow the movement of ions (charged particles) from inside to out or outside to in the cell – very selective – only allow certain ions to move – can be in an open or closed state -ion pump – pumps ions from inside to out or outside to in the cell – moves ions along gradients – often requires energy Forces that control the movement of ions Chamber 1 and 2 have same conc of kcl (potassium chloride) – when kcl put into water it separates into ions K+ and Cl- - only K+ ions can move through the membrane - same conc either side – if 1 K+ ion randomly moves from chamber 1 to chamber 2 it increases the electrical charge in chamber 2 (makes it more positive) – chamber 1 will pull the K+ ion across to balance things out Higher conc in chamber 1 – K+ ion attracted to chamber 2 as there is a higher conc in chamber 1 – diffusion force will pull the K+ ion into chamber 2 – consequence = chamber 2 becomes more positive – causes an electrical force back to chamber 1 from chamber 2 – K+ ions attracted back into chamber 1 by electrical force – eventually get a balance between the diffusion force and electrical force – what happens at the resting state of neurons Resting membrane potential and Na+/K+ pump Sodium potassium pump takes 3 sodium ions from inside the neuron and transports them to outside – then takes 2 potassium ions from outside and moves them inside: - Creates a higher conc of sodium outside the neuron and creates a higher conc of potassium inside the neuron - Creates an imbalance in charge – inside of neuron becomes more negatively charged – creates conc gradients and electrical gradients Open inside cell – high affinity for sodium which binds to the pump – phosphorylation of ATP – opens to the outside and releases sodium as it now has a low affinity for it – high affinity for potassium which binds to the pump – opens inside the neuron and releases potassium inside the cell – net loss of one positively charged ion results in an electrical current The action potential - occurs when voltage gated ion channels open Threshold Resting potential – negatively charged (-65mv) Inject -ve currents into the neuron = neuron becomes more negatively charged (hyperpolarised) Inject +ve currents into the neuron – neuron becomes more positively charged (depolarisation) Inject more +ve currents to above the threshold (-50mv) – neuron fires an action potential Action potentials don’t get bigger, just more frequent Axon hillock is where action potentials are generated (between axon and soma) Voltage gated (gate is closed unless the voltage gets to a certain level – the threshold level) Na+ and K+ channels Once get to threshold level – voltage gated sodium ion channels open – movement of sodium into the neuron - theres a higher conc of sodium outside the neuron because of the Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 sodium potassium pump – the neuron is negatively charged so the electrical forces push it inside Both forces (diffusion force and electrical force) going in the same direction – sodium comes into the neuron as a result A little while later the potassium ion channels open – results in potassium leaving the neuron The action potential The neuron gets depolarised above threshold – sodium gated ion channels open – sodium goes into neuron along its diffusion and electrical force (flood of sodium into the neuron) – causes neuron to become more positive – above threshold so action potential occurs Sodium voltage gated ion channels close and potassium voltage gated channels open – diffusion and electrical forces push potassium ions from inside the neuron to outside – causes the potential/charge of the neuron to decrease Potassium voltage gated channels stay open – more potassium leaks out of the neuron – makes neuron more negative – dips/undershoots (occurs as most voltage gated potassium channels are still open) – then goes back to resting membrane potential (recovery phase) The action potential is propagated along the axon down to the synapse Myelin sheath – insulates the axon and speeds up the nerve impulse – nerve impulse jumps from one node of ranvier to another (not all neurons have a myelin sheath so conduction of action potentials is slower in those neurons) The synapse Chemical signals in the brain – a historical perspective Dale and Lowei – worked together – discovered chemicals that influenced the way the brain works Lowei – 2 chambers each with a frog heart in saline solution – chambers connected by a tube – dissected the heart with the vagus nerve – stimulated vagus nerve of heart 1 causing it to slow down – heart 2 (which doesn’t have a vagus nerve attached) after a little while, starts to slow down too – from this Lowei summised that there were chemicals that were released from the vagus nerve which caused heart 1 to slow down – some of these chemicals diffused into the water, passed down the tube into the second chamber which caused heart 2 to slow down – chemicals now known as neurotransmitters Discovery of neurotransmitters allowed the possibility of developing drugs that could help people in a less invasive way Synapse Action potential comes down and reaches the end of the terminal – causes calcium ion channels to open – let calcium into the neuron (which is positively charged) – causes vesicles to move to the end of the terminal and deposit their contents into the synapse Pre synaptic knob – vesicles storing neurotransmitter molecules Neurotransmitter in synapse binds to receptors on the post synaptic knob – causes the receptor to open a pore which allows ions to pass through Neurotransmitter receptors in the postsynaptic knob Receptor has a region that the neurotransmitter can bind to Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 In closed state when there are no neurotransmitters When neurotransmitter binds to the receptor it becomes open and allows ions from outside the cell to pass through inside Positively charged ions – neuron will become more positive – more likely to depolarise and more likely to fire an action potential Negatively charged ions – neuron will be more negative – hyperpolarised – less likely to fire an action potential Drugs operate by having a very similar structure to the neurotransmitter – they bind to the receptor causing the ion channels to open – called agonists (act exactly like the neurotransmitter) Other drugs have structures similar to the neurotransmitter but block the binding sites of the neurotransmitter – called antagonists Once neurotransmitter has an effect it needs to be removed from the synapse: - Neurotransmitter is broken down - Neurotransmitter taken up by support cells Some drugs can affect this process by preventing the reuptake of a neurotransmitter (agonists – prolonging the effect of a neurotransmitter) Chlorpromazine – dopamine antagonist Prozac – 5-HT2B agonist Nicotine – nicotinic acetylcholine agonist Integrating synaptic potentials Threshold and the summation of postsynaptic potentials 3 inputs (from other neurons): - E1 – an excitatory input - E2 – and excitatory input - I – Inhibitory input Receiving an input from one excitatory input (E1 or E2): The neurotransmitters bind, which opens the receptors which allows positively charged ions to enter the neuron – increase in positive charge in the neuron (but not above threshold) – decays after a period of time and goes back down to resting potential More than one excitatory input (E1 and E2): Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Increase in positive current from E1 and E2 – sum up to get above threshold level – combination of the 2 causes an action potential to occur within the neuron 1 Inhibitory input: Receptor allows negatively charged ions into the neuron – neuron becomes more negatively charged (hyperpolarised) – inhibitory post synaptic potential (less likely to fire an action potential) – dissipates and goes back to resting potential An excitatory input and an inhibitory input: Cancel eachother out – could be a little bit of net positive charge but it gradually gets back to resting membrane potential All three (E1, E2 and I): Summed activity of the excitatory neurons – effect of inhibitory input takes it just below threshold – action potential doesn’t occur Lecture 3 The human nervous system The brain of a psychopath Raine – compared the brains of control people (normal/non psychopathic people) with the brains of psychopaths using PET scans (which look at blood flow to diff regions of the brain) – found a difference in the blood flow to particular regions – in psychopath the amygdala, medial prefrontal cortex and cingulate gyrus were getting less blood flow Neurons Dendrites – involved in receiving information Axon – for sending info Cerebral cortex – outside covering of the brain Glial cells 3 types: 1. Astrocyte – play a role in neurotransmitter reuptake - important role in blood flow to particular regions of the brain 2. Oligodendrocyte - Produce myelin and wrap around the axons 3. Microglial cell - Perform immune function – if there’s any inflammation or disease in the brain they will become active Central and peripheral nervous system Central nervous system: - Brain - Spinal cord Peripheral nervous system: - Nerves that come from the spinal cord and go towards muscles in the body - Autonomic nervous system – composed of 2 parts: 1. Sympathetic – in action – four F’s – flight fight fright and sexual behaviour Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 2. Parasympathetic – involved at rest – controls digestion, increases digestion/blood flow to the gut, slows down heart rate Grey matter and white matter Grey matter = predominantly the cell bodies and the dendrites of neurons White matter = predominantly the axons – myelin gives the difference in appearance Can distinguish between the 2 in MRI scans The lateral surface of the brain The lobes of the cerebrum 4 lobes: 1. Frontal lobe – involved in planning, movement, personality 2. Parietal lobe – involved in sensation, visually guided movement, spatial attention 3. Temporal lobe – involved in hearing, visual recognition e.g faces 4. Occipital lobe – involved in processing visual info Anatomical terminology Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Dorsal = superior, ventral = inferior Gyri and sulci The folds and indentations in the brain that give it its wrinkled appearance Gyri = the bumps/’hills’ we can see Sulci = the valleys inbetween the gyri Sylvian fissure – divides the temporal lobe from the frontal and parietal lobe Central sulcus – divides the frontal lobe from the parietal lobe Precentral gyrus - Gyrus anterior to the central sulcus – strip of brain that contains the primary motor cortex Postcentral gyrus - Posterior the the central sulcus, in the parietal lobe – contains the primary somatosensory Lateral surface of the brain Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Ventral surface of the brain More anatomical terminology Used for dissecting the brain along different axes to allow us to look inside the structure of the brain Sagittal section – allows you to split the 2 hemispheres of the brain apart Coronal (frontal) section – divides the brain in sections that go from front to back (anterior to posterior) Horizontal plane divides the brain from top to bottom (superior to inferior or dorsal to ventral) Medial surface of the human brain Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Sagittal section between the 2 hemispheres: Cingulate sulcus – forms a boundary between the superior frontal gyrus and the cingulate gyrus – often affected in psychopaths Orbital gyri also affected in psychopaths – less blood flow and activity in these regions Calcarine sulcus – important as a landmark for showing the primary visual cortex Parieto-occipital sulcus – divides the occipital lobe from the parietal lobe Basal ganglia and amygdala Coronal (Frontal) sections through the brain Can see white and grey matter Structures in the middle of the brain: White matter bands that join the 2 hemispheres – one is corpus callosum, another is the anterior commissure (important for joining info from the temporal lobe in the right and left hemisphere) Basal ganglia Diseases of the basal ganglia: - Parkinson’s disease - inability to initiate movement - Huntington’s disease – make lots of unconsciously initiated movements - Tourette’s – uncontrolled utterances Amygdala – region involved in processing fear and emotion Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Thalamus and hippocampus Thalamus – relay point for all sensory information (apart from smell) from the body to the cerebral cortex – important role in sensory processing Hypothalamus and the pineal gland Hypothalamus: Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 - monitors internal state of the body e.g the amount of water in the blood, temperature – connection with the autonomic nervous system - Detects changes in water, glucose and oxygen levels – sends signals to change this e.g signals to stomach when glucose is low Brainstem and cerebellum Cerebellum (little brain) - Role in the coordination of movements Brainstem Made up of: - Midbrain – vision and auditory reflexes - Pons – has important neurones for processing auditory info - Medulla – controls vital organs e.g controls heart rate and breathing Connections within the brain Commisure – communication from one hemisphere to another: - corpus callosum - Anterior commisure Association tract - communication within the brain Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Projection tract – connect the brain to the rest of the body Meninges and ventricles Ventricles – fluid filled regions in the brain – contain cerebral spinal fluid – 4 in total 2 lateral ventricles (left and right) Important role for generating cerebral spinal fluid which forms a cushion between the brain and the skull Meninges Membranes that hold in the cerebral spinal fluid on the surface Infection/swelling of meninges = meningitis The brain’s blood supply Brain takes up 20% of the body’s supply of oxygen and glucose 2 main arteries: - Internal carotid artery - Basilar artery Come together in the circle of willis – if there is a reduction in blood supply from one artery then the other artery can compensate for it Lecture 4 Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Does overall brain size predict behavioural differences between species? Savant syndrome – people who have special abilities – high cognitive abilities eg learning languages, but limited to everyday life tasks – often not able to live without assistance Neuroethology – a comparative approach Comparing behaviour of brains between different species Does absolute brain size correlate with cognitive ability? Allometry – the importance of brain size relative to body size – as the body increases in size, the brain increases in size Residual brain size is related to more complex behaviour e.g howler monkey has smaller brain than squirrel monkey – squirrel monkey needs more fruit so forages and has to search for food – has to travel further, have to have a better idea of spatial awareness, need to know whether the fruit is ripe etc (more complex behaviour) – howler monkey just eats what’s around it Evolution of the human brain and cognition Over time human body weight has increased by 50% – brain size also increased by 200% Genes may underlie evolutionary changes in brain size Does the size of brain regions predict behavioural differences between species? The localization of function – different regions of the brain are specialised for individual behaviours Evolutionary specializations of brain and behaviour Bat – echolocation to navigate around the world Tarsia – big eyes to see well The principle of proper mass (idea that a brain region is big enough to do its job properly) Focus on A and D Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 SC: superior colliculus IC: inferior colliculus SC involved in vision, IC involved in auditory processing In bat IC is bigger as it uses its hearing much more In tarsier SC is bigger as it uses its vision more Overrepresentation of critical body parts in sensory and motor maps Regions of the brain that have maps of the body = primary motor cortex and primary somatic sensory cortex (different regions of these strips are specialised for different regions of the body) The representation of different areas is disproportional to the size of the body part e.g the leg is a large part of the body but has the same representation of the hand (which is a much smaller body part) Things that are more important e.g hands and face (important for sensation, emotion and motor control) have a bigger representation In rats the representation of whiskers (important as they move around in the dark and use them to feel around them) is large relative to other parts of the body The hippocampus and the evolution of learning and memory Hippocampus = region important for memory and spatial navigation Scrub jay – finds food where it can and eats it – smaller hippocampus than you would predict from its brain size Clark’s nutcracker – more complicated pattern of behaviour – stores food and can remember the locations of where they’ve stored it – needs to remember what it stored and where – memory task more demanding – as a result has a larger hippocampus than you would predict from its brain size Neocortex size and the evolution of social intelligence Larger amounts/volume of neocortex are often reflected by higher rates of deception (social intelligence) Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 Face regions and social networks Animals are able to recognise individual members of their species Brain imaging studies of monkeys – found regions of the brain specialised for processing faces Higher response in action potentials when people are viewing faces compared to non face objects 3 regions that have face selected patches – increase in face regions in individuals that live in larger groups (relationship between brain size and behaviour reflected in a specific brain region involved in processing faces and relative to the size of the social network in which the animal lives) Broca’s area and the evolution of language Broca’s area involved in the production of language Damage to broca’s area = motor aphasia (inability to speak) Macaque monkey – doesn’t have developed language – broca’s area proportionally much smaller than in the human brain (reflects our understanding that language is much more developed in humans than it is in monkeys in terms of communication) Communication in song birds Increase in repertoire size gives you an increase in the residual size of the song bird nucleus (the larger the nucleus the more songs the bird knows/can sing) Do differences in brain size predict behavioural differences with humans? Correlations between IQ and cortical (cerebral cortex) thickness If you have a thicker cortical thickness (particularly in the frontal cortex) in young childhood IQ is negatively predicted (lower IQ than average) A thicker cerebral cortex in late childhood (in frontal regions) predicts IQ – continues in early adolescence and early adulthood but to a lesser extent However thickness of other regions of the cerebral cortex aren’t a good predictor of IQ – suggests different regions of the brain might be involved in different types of function Overrepresentation of critical body parts in sensory maps 1. Study of violin players - Looking at the representation of the left hand in violin players - Compared the size of the representation of digits in the left hand (important for people who play the violin) - Stimulated fingers of the left hand to see the magnitude of the response in the right hemisphere and the right primary somatosensory cortex - Found a much larger representation of the fingers in the left hand of the primary somatosensory cortex in violin players compared to control pp who did not play the violin 2. Representation of somatosensory cortex – looking at the size of the representations of different digits of people who use touch screen phones - Comparing people who have a touch screen phone, and predominantly use their thumb for manipulating the phone to people who do not have a touch screen phone Downloaded by Miriam Tucker ([email protected])  lOMoARcPSD|50486287 - The representation of the thumb is much greater in people who have a touch screen phone and use their thumb compared to people who don’t have a touchscreen phone - Same test but with pp who use their index finger to interact with their touchscreen phone – same outcome (greater representation of index finger in those with touchscreen phones) The size of the hippocampus in taxi drivers - The longer someone has been a taxi driver, the larger their posterior hippocampus Downloaded by Miriam Tucker ([email protected])