Neuropsychology exam 2 studyguide
Neuropsychology exam 2 studyguide PSB 4240
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This 27 page Study Guide was uploaded by Puck Reeders on Monday November 2, 2015. The Study Guide belongs to PSB 4240 at Florida International University taught by Anthony Dick in Summer 2015. Since its upload, it has received 204 views. For similar materials see Neuropsychology in Psychlogy at Florida International University.
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Date Created: 11/02/15
Methods in Cognitive Neuroscience Posted: 5/18/2015 Some methods o Electrophysiological (oldest methods) Single unit recording (in monkeys/other animals) Electrostimulation in awake humans EEG/ERP o Magnetic MEG - Magnetoencephalography TMS – Transcranial Magnetic Stimulation MRI – Magnetic Resonance Imaging o Perfusion – changes in blood flow fNIRS ( Functional near infrared spectroscopy) PET – position emission tomography MRI Time scales and levels o All the different methods work at different time scales and levels. Brain – map – column – layer – neuron – dendrite – synapse EEG & MEG: Have very good temporal resolution (to look at changes in the brain function over miliseconds) but they have poor spatial resolution (where the signals are coming from). MRI: Better in spatial resolution because you can get down to the level of the cortical surface. Some MRI scans can get to the column or layer organization of the cortical surface (6 layers). To get down to the Neuron, Dendrite or Synapse level, you will need the Multi-Unit Recording, Single-Unit Recording or the Patch clamp recording -> these are invasive procedures typically only used in animals Single unit recording o Mouse with a small canula on the top of the head and a small electrode wire in the mouse’s brain. o Because mice and rats are genetically similar they have similar patterns of sutures on the skull. You can I those patterns and you can develop a stereotaxic coordinate system. You can validate his by sacrificing the animal and doing histology on the slices of the brain and seeing if the electrode is in the right position. o You can also segregate neurons from the brain and put them in a Petri dish and record the spiking of the electrode. You can record whether the neuron is responding or not. Electrostimulation and recording in awake humans o Electrodes on brain of people going in surgery Surface recording Down in cortex o You can also use a bipolar electrode to disrupt function temporarily. You would put the electrode in the cortex, and put a current in the surface there. The neurons underneath that cortex would be disrupted. This can show which part of the brain is performing a particular function. Example: pt counts from 1 to 10. When they get to 5 or 6, the surgeon puts the electrode down. If the person stops counting, you can assume that that area of the brain is involved in producing language. This allows you to try to map which are of the brain does what. Noninvasive procedures: EEG/ERP o EEG: Electroencephalogram o ERP: Event-related potentials (EEG that is time-locked to stimulus) Same procedure just different in how you present stimuli. o Can analyze: Peals (e.g., N400, P300) Power spectrum (Event related synchrony and desynchrony; ERS/ERD) Showing synchrony and desynchrony in the discharge of neurons that are associated with a task you are doing EEG power reflects the number of neurons that discharge synchronously o Power spectra analysis of electroencephalography data measure the number of neurons that______. Discharge synchronously You can use it on infants You can average the change in electrical potentials and look at the peaks The longer components show how the peak would change in response to a stimuli You can also look at the power spectra by difference in frequency bands that are associated with particular functions Delta – up to 4 Hz indicator of slow wave sleep Theta – 4-7 Hz Alpha – 8-12 Hz Beta – 12-30 Hz Gamma – 30-100+ Hz o The __________ rhythm is an indicator of adult slow wave sleep. Delta o As said before, there are two ways to analyze ERP analysis ERP analysis Power Spectra analysis: frequency band differences across the conditions Source analysis EEG o All electrodes recorded against reference electrodes o Choice of the reference electrode has an effect on the data o However, cortical source is difficult to determine due to the “inverse problem” Activity near skull is easier to detect han deep structures Activity in sulci difficult to detect (over 2/3 of cortex in sulci!) o The difficulty of localizing the cortical or subcortical source of the EE signals is called the ________ Inverse problem Noninvasive methods: MEG o Magnetoencephalography o MEG somewhat able to overcome source localization problem over the EEG Magnetic induction less impeded by skull o Uses SQUID: Superconducting Quantum Interference Device Measures magnetic induction produced by electrical transmission Indexes 10 neurons TMS o MS magnetic waves disrupt neural processes at a focused cortical source (i.e., “virtual lesion”) o The shape of the coil affects the magnetic disruption o Video of the guy where the motor function was interrupted o TMS can have a good effect on focal areas in the brain, they were targeting motor areas and that interrupted motor function fNIRS (Functional Near Infrared Spectroscopy) o When neurons activate, metabolic demand increases, increasing oxygen consumption and cerebral blood flow to that region in the brain o Oxygenate hemoglobin (HbO ) 2ill then displace deoxygenated hemoglobin (HHb) o HbO 2nd HHb have different absorption properties of near-infrared light, and the difference can be detected by a sensor through the skull. o Good spatial and temporal resolution. o Can be used on infants and children. o Look at slide Top: oxygenated (red) and deoxygenated (blue) curves Bottom: Arrangement of optical array used to collect data o __________ measures the different t absorption properties of oxygenated and e- oxygenated hemoglobin Functional Near Infrared Spectroscopy o Problem: because it is an optical system and only detects a small change, it only detects changes in the gyri. Cannot go in the sulci or subcortical structures Functional Neuroimaging: PET o Perfusion method o Position emission tomography o Invasive: involves injecting a radioactive tracer o As the tracer decays, it emits a positron o Positron’s interaction with electrons is detected by a receiving device Basically based on changing blood flow and a stimulus o Voxel = 3D pixel o fMRI has replaced PET to large degree o PET still useful for Clinical Radiolabeling o drug compounds MRI Magnetic Resonance Imaging o MRI invented in 1973, and fMRI in 1992 Same equipment different way of collecting daya o Clinical and Research settings o Not invasive, unless contrast agents are used. o It is safe if proper precautions are followed o Good spatial resolution but poor temporal resolution MRI: The physics o MRI of the knee is the same basic principle as the MRI of the brain o Magnetic resonance Imaging: a very strong magnet o Body mostly water and fat, contains a large number of hydrogen atoms (1 proton) o Protons spin and change orientation when placed in a magnetic field o o The spin around their axis of rotation o In a magnetic field, some protons line up with their axis parallel to the magnetic field, and some line up anti-parallel to the magnetic field. o Precession: the proton spins, but also precesses around the axis of the magnetic field Precession: motion of a spinning boy such that the axis sweeps out a cone Precessing protons have 2 states o Parralel (lower-energy) and anti-parralel (higher-energy) o In magnetic field, more pretons in the parallel state o A radiofrequency pulse perturbs the equilibrium state of the protons o When protons change state, they emit energy o When they return, this energy is detected by a radiofrequency coil Longitudinal and Transverse o Vector of magnetization has two components: Longitudinal (A) and Transverse (B) o Longitudinal: When you knock the spinning proton out of phase about 90 degrees. It is going to then immediately want to return to the parallel state with the magnetic field. When it returns you can detect that vector of magnetization change. The whole time it’s spinning and precessing around the axis rotation. o Transverse: Because it is precessing, it is also going to change the transversevector magnetization. As it comes down it is also precessing, and that will be quantified as the change of the transverse vector or magnization. o You can measure there two independently T1, T2, and T2*rates of relaxation o Longitudinal relaxation: T1 How long does it take the spinning proton to return to its original state o Transverse relaxation: T2 and T2* Spins of protons lose phase with each other, due to Interaction with other protons (T2): when they bump into eachother Differences in MF inhomogeneity (T2*): Phase loss is due to that the magnetic field is inhomogenous (for fMRI) Tissue contrast (T1 and T2) o MRI exploits the fact that different tissues (e.g., white matter, grey matter) have different T1 and T2 relaxation rates o If you excite protons there is a good time to record their vector of magnitezation. o If you record at the first dotted line in the picture below, bc one kind of tissue has a longer T1 relaxation rate than the other kind of tissue, you will get good tissue contrast. o If you record at the second dotted line, or way before the first dotted line close to the excitement, you get poor contrast o Therefore you would want to record when there is a big difference in relaxation rate for example of a longitudinal vector o Maximize contrast by receiving signal at point after excitation when difference is maximized. T1-weighed scan o Provides structural scan of brain (or other body parts) anatomy o CSF is dark, grey matter grey, white matter white o Excellent for looking at anatomy T2-Weighted Scan o CSF bright or dark (e.g., FLAIR), white matter is dark o FLAIR: is a T2 weighted scan, but it actually tries to drop the signal out of things like CSF (Fluid Attenuated inversion recovery sequence) (lesion is bright) o Lesion tumor show up bright on T2 o Hemoglobin has magnetic properties o T2 weighted scans are also good for detecting lesions in the white matter MS: myelin degenerates More white around the lateral ventricles and the ventricles are expanding because the white matter is atrophic. In a stained white matter cross section: white matter and the black dots are the myelin. Later on in the disease you have far fewer myelinated axons o In a T1-weighted scan, cerebrospinal fluid is always ________ Dark ( grey matter is grey, and white matter is white) Imaging Early Brain injury structural: o If they become right handed, the lesion is most likely in the right hemisphere o Sometimes the IQ of someone could be guessed by looking at the brain injury Prenatal strokes and R hand, age 25, (Verbal IQ: 77; Performance IQ: 73; Full scale IQ: 73) Bilateral interventricular hemorrhagic injury + midline shift (left hemisphere larger than left one) R hand, age 26 (VIG:101; PIQ:99: FIQ:100) Cyst filled with cerebral spinal fluid. In right hemisphere The white matter was necrotic and died and the empty space filled up with CSF. Halo or right hemisphere damage. They person is doing pretty well: average IQ. L hand, age 7 (VIQ: 100: PIQ:100: FIQ: 100) Left handed: likely to be left hemisphere injury. Small injury, average IQ, It has affected the putamen and parts of the internal capsule (descending motor pathways) higher up in the brain there is also damage that you cannot see on this picture. In the descending tracts (not on this picture) there is not much asymmetry. R hand, age 20 (VIQ: 110; PIQ: 79; FIQ: 96) Scored better on Verbal IQ Right handed: might guess it’s a right hemisphere injury T1 + Flair: Hemispherectomy (right hemisphere removed because of untreatable seizures) Almost no right cerebral peduncle in the teddy bear Recovery is amazing (would be worse if this happened in adults) Blood Oxygenation Level dependent (BOLD) fMRI: Basics o Oxygenated hemoglobin is diamagnetic; de-oxygenated hemoglobin is paramagnetic o Paramagnetic objects lead to T2* spin dephaing (a lower MR T2* signal) o Blood flow increases to brain regions activating in a response to a task o Oxygenated blood replaces the de-oxygenated blood following neural activity. Because they have a different magnetic influence on the MR signal, there will be a higher MR signal o BOLD stands for __________ “Blood Oxygenation Level Dependent” o BOLD signal rises to peak and falls over period of time (about 12-18 seconds) o Temporal resolution is not very good o MR images of whole brain acquired every 1-3 sec depending on scan/design o The replacement of de-oxygenated blood with oxygenated blood leads to ________ magnetic resonance signal Increased After all that we can take a structural scan of the brain and use software to process this we can re-construct the lateral surface. o You create a 3D image from an MRI image Normal Language Comprehension o Someone listening to someone telling a story: Visual cortex active: Occipital lobe by the calcarine fissure Lateral part of the superior temporal gyrus: processing speech Transverse temporal gyrus Wernicke Area is also active Broca’s are also active Area near the motor cortex also active MRI: Diffusion tensor imaging o Same machine, different pulse sequence o DTI takes advantage of the anisotropic (directional) nature of water molecules in axons o In CSF it flows a bit more in undirected manner o The direction of fractional anisotropy (FA) is higher in white matter than in grey matter o Direction of FA can be used to map fiber pathways across voxels o Diffusion tensor imaging takes advantage of the anisotropic diffusion direction of water molecules in __________ Axons (Anisotropic means that it is in a directed fashion) Motor Systems We start with what is a motor loop. o You have an upper motor neuron in the motor cortex (most motor cortex is buried in the central sulcus) o If you follow the blue line (slide 1) down, there are a couple of stops along the way to lower motor neurons into the spinal cord, and these will eventually be sent out as projections to the muscles. o Then there is a feedback loop for the sensory systems. o Motor neurons come out of the ventral root of the spinal cord and the sensory neurons come into the dorsal root, and then backup in the somatosensory cortex via the thalamus. The somatosensory cortex is mostly located in the post central gyrus Motor systems o There are only ~1 million motor neurons, and most of them are in the spinal cord. o Dark stain in picture is white matter, and white stain is grey matter. o Lower motor neurons in spinal cord and brainstem are targets of CNS pathways. o There is a systematic organization of the motor neurons in the spinal cord: there are neurons associated with hand function etc. o _______ in the brainstem and spinal cord are target of CNS motor pathways Lower Motor neurons Central Pattern Generators o Motor programs for whole movements (breathing, walking) o Upper motor neurons influence action of central pattern generators o As long as there generators are firing you get whole movements Cut head of chicken: still walks around o There are neuro assemblies for whole movements. The advantage is that you don’t have to “reinvent the wheel” o Most are very well established at birth Organization o Upper motor neurons in central sulcus and extending into the pre-central gyrus. o They are going to target the lower motor neurons, which then targets muscles o The basal ganglia structures (mainly the dorsal striatum)are going to influence, via the thalamus, the firing of the upper motor neurons (UMN) o The association cortex (especially the parietal and frontal lobes) are going to influence the firing of the UMN (upper motor neurons) o Also the cerebellum, via the thalamus, is going to influence the firing of the UMN o All this, establishes the motor system o UMN in the primary motor cortex will be discussed first. UMN (Upper Motor Neurons) in the primary motor cortex o In central sulcus/precentral gyrus o Decending fiber pathways o Many cortico-spinal, or motor spinal pathways The biggest one is the cortico spinal tract (CST) (voluntary movement) Starts in central sulcus (bets cell) which send their axons down into the spinal cord. Axons come down into the internal capsule; collection of fibers that goes down splitting the striatum. Then it comes to the teddy bear through the cerebral peduncle Then it comes down through the pons and the medulla Right around the medulla most of the fibers (80%) cross over into the other side of the spinal cord to target the spinal neurons. That means that if you have right motor neurons firing, it is going to influence the action of the left spinal cord, and the other way around. If you damage right motor cortex, you will have trouble moving limbs on left side of body. Tectospinal Tract (reflex to visual stimulation) Originates in the superior cullicus Tecto pulvinar pathway (rapid response vision response): this pathway responds to if a baseball is going to your head. The tectospinal tract is the motor component. Rubrospinal Tract (voluntary movement) Originates in the red nucleus Down to spinal cord Reticulospinal tract (voluntary movement; muscle tone; posture; balance) Originates in the reticular formation in the pons Vestibular spinal tract (posture; head motion) Originates in the Vestibular Nucleus 8 cranial nerve carries that vestibular information from the semicircular canals in the ears and the first target is the vestibular nucleus. This also influence lower motor neurons Corticobulbar tract (speech) CST pyramidal decussation (also called the parymidal tracts) o Crosses over at the level of the medulla o UMN (pyramidal neurons) mainly in central sulcus come down through internal light grey capsule (striatum)* 20% remains ipsilateral and 80% crosses over at the medulla level (pyramidal decussating) o The majority of fibers of the corticospinal tract cross at the ________ in the medulla Pyramidal decussation The motor cortex is mostly buried in the central sulcus and extends out to the precentral gyrus (primary motor cortex in purple) (check slide) o The motor cortex has an imprecise somatotopic map. This means that the more dorsal you are, the parts of the brain in charge of moving lower limbs are dorsally. o The parts of the brain in charge of moving arm and hand are also somewhat superior/dorsally (in green on slide) o The face and mouth are located in the pre-central gyrus (green in slide) o Green: premotor cortex, and coordinates with the primary motor cortex to influence movement. o In the sensory homunculus there are large hands and large lips because they are a large amount of neurons in that area. The motor homunculus is similar, but the hand representation is even larger because it is very beneficial for humans to use the hands (especially for fine motor skills). In evolution: climbing trees, picking up nuts etc. Same thing for the mouth. Convergence and overlap in Penfield’s date o You stimulate areas in the central sulcus and they wanted to see which parts of the limbs would move, and they found a somatotopic organization. o The organization is not as well defined as previously thought: areas/fields overlap quite a bit. The “Hand” knob of the motor cortex o It is a little omega shape, in the central sulcus, and this is what shows activation of the motor function of the hand Function of Motor Cortex o Parts of MC may not implement discrete muscles, but rather organized movements. It is difficult to find the muscles that could move just a finger. If u drive that neuron you end up driving whole movements. o Categories of movement are elicited by electrical stimulation of motor cortex o Motor cortex has an organized network of whole movements rather than single movements Motor cortex o The motor cortex does not work in isolation. o Prefrontal cortex plans (Planning) Supplementary cortex + premotor cortex organize sequence (organization) primary motor cortex executes actions (Execution) Difficulty of movement o It depends on how difficult movement is Simple movement: You do not need much. Mainly motor cortical activity. Sequenced movement: Different regions interact (learning how to play the piano and also speech) Planned movement (navigate fingers through maze) o It is a whole motor system in the cortex VIDEO 2 The primary parts of the motor system involve the primary motor cortex in the central sulcus, the other cortical regions influencing the firing of those neurons, but the Basal Ganglia also contribute to the motor system. o They do so by regulating the neural discharge of the motor neurons in the cortex. o What are the Basal Ganglia? Striatum Caudate Nucleus Putamen Globus Pallidus Sometimes: Subthalamic Nucleus and Substantia Nigra and Thalamus (depends who you ask) o In this picture, notice the Putamen, Globus Pallidus and the Caudate Nucleus o In this picture, you can see the Caudate and the Putamen o In the motor cortex you have the internal capsule coming down through the striatum (black pathway) o Sagittal Section, Note in slide Caudate Putamen Fibers of the descending motor system going down splitting the striatum (black fiber pathway) Th: Thalamus Am: Amygdala HC: Hippocampus Cerebral peduncle o In the picture lower left, you see the peduncle and the substantia nigra o Close up Slide note: Caudate Put: Putamen CC: corpus callosum GP: globus pallidus AC: anterior commissure F: fornix 3: third ventricle Basal Ganglia function is defined by its inputs and outputs o Cortical projections reach putamen, caudate, nucleus accumbans, and subthalamic nucleus o Two output nuceli: GPi (internal part of the Globus Pallidus) SNr (Reticular part of the Substantia Nigra) o Green: Excitatory Red: inhibitory You see in green he excitatory input, and then you have a loop that goes through the thalamus back up to the cortex. o 3 targets: Thalamus Superior Colliculus Pedunculo-pontine nucleus And back to the cortex Example of organization of basal ganglia projections o Specific example: Putamen o Cortical neuron sends projections to putamen. There are synapses in the putamen and when those are activated, they inhibit parts in the GPe (external part of the globus pallidus), GPi (internal part), the SNc and SNr. o The Substantia nigra (SNc) then project back into the putamen. In some cases those projections are inhibitory, and in other cases they are excitatory. o The thalamus is also going to target the Putamen, and other neurons in the thalamus are going to target the cortex Thalamic Routes o BG modulate cortical output for motor, cognitive, affective systems o The loop depends on the cortical origin Motor loop (Purple): The motor loop goes from the motor and premotor cortical regions to the putamen, then to the Globus Pallidus (GP), which targets the Ventral Anterior(VA) and the Ventral Lateral(VL) part of the thalamus , Those thalamic outputs target the same regions they were sent from GP is an output of the basal ganglia that targets the thalamus Association loop (blue): The association loop goes from the prefrontal cortex, parietal, temporal cortex to the Caudate. That targets the GP (Globus Pallidus) + SNr (reticular part of Substantia Nigra). That goes to the DM (Dorso medial root of the Thalamus) and then back to the cortex Limbic loop (Orange): From limbic lobe to the Nucleus accumbens to Ventro Posterior Nucleus to the Thalamus and back to the limbic system o Note: The primary Sensory areas do not loop through the basal ganglia (e.g., Pimary visual cortex and Primary auditory cortex), and that is because they are not targeting the basal ganglia o Loops summarized Putamen – GP – Thalamus – Cortex – Motor – Somatosensory loop Caudate – Gpa – SNr – Thalamus (DM) – Association cortex loop Limbic – ventral striatum loop (Nucleus Accumbens) o Know that there are 3 different loops!!! Non Thalamic routes o Output to superior colliculus: Influence head and eye movement o Output to pedunculopontine nucleus: Influence spinal cord and locomotion and postural control Disorders of BG(Basal Ganglia) illuminate function o Parkinson’s disease Symptoms: muscle rigidity, tremor, postural and gait abnormalities, bradykinesia (difficulty in movement) Late stage akinesia (inability to move), impaired cognitive function Treatable, but not curable What causes it: Degeneration of dopaminergic neurons in substantia nigra (pars compacta) There are 2 parts of the substantia nigra Compact part (SNc): where there are many dopaminergic neurons: this part of the brain produces dopamine Reticular part (SNr): One of the output nucleus of the basal ganglia o CP: cerebral peduncle o RN: red nucleus Parkinson’s disease is caused by degeneration of dopaminergic neurons in the______ Substantia Nigra pars compacta Treatments: (Check slides to see how the SN is degenerated Early on: L-Dopa (dopamine precursor) (Dopamine itself does not cross the BBbarrier) Ineffective after degeneration reaches a certain point Deep brain stimulation of GPi or STN also effective, but exact mechanism unknown (Put electrode deep in brain). Works well temporarily. o Hungtington’s disease Results from genetic mutation, but onset is mid-adulthood People who carry the genetic mutation, they don’t know they have the disease, and they are likely to pass it on to relatives Symptoms: involuntary movement of extreminities, changes in mood and emotional state, late stage dementia. Cause: Mutation of gene coding Huntington protein produces degeneration of GABAergic neurons in striatum. GABA is a inhibitory NT It messes up the Basal Ganglia circuit There is no cure o Executive dysfunction Executive function is a term for a number of processes associated with the frontal lobe: Planning, switching between conflicting possibilities, inhibiting pre--??--- responses (all PFC) Woman suffered from recurring headaches for a month, vomiting, then disappeared for 3 days. Personality changed: Abnormal behaviors include vulgarity, impulsiveness, easy frustration, violent outbursts, minor criminal behavior etc. typical frontal lobe dysfunction What happened? Degeneration of Caudate. She probably had an infection that targeted the caudate. And because the caudate is connected up to the frontal lobe that circuit to regulate behavior and executive function. Therefore damaging it will influence executive functions o Tourrette syndrome Repetitive, uncrotollable tics (curse words or motor system related) May involve dysfunction of striatum and GP (Globus pallidus) When the person in the video tries to speak, his symptoms get worse. The reason is probably that articulating is a difficult motor sequence to accomplish and that brings on the basal ganglia to try and regulate cortical discharge. When that happens you are taxing(challenge) other abilities of the motor cortex, which is to impede motor movement. Therefore it makes it more difficult to perform those functions. Ex: When u are sitting here reading this, you motor cortex is trying to let you sit still and inhibits movements. Hyphotheses of Basal Ganglia function o BG may be involved in regulating the rate and timing of cortical neuronal discharge. It is a modulater of the neuronal discharge. o This may involve a direct pathway that facilitates selected cortical activity, and an indirect pathway that suppresses other cortical activity. Not yet proven o One Theory of basal ganglia function is that these nuclei regulate the _______ and _______ of cortical neuronal discharge Rate + Timing Direct pathway: leads to increased cortical output (facilitatory) o 1) Excitatory corticostriatal fibers o 2) activate inhibitory neurons in the striatum o 3) The striatum inhibits GPi o 4) and the SNr, thus inhibiting the thalamus o 5) this allows the thalamus to facilitate certain cortical outputs o Indirect pathway: leads to decreased cortical output o 1) goes to Putamen o 2) inhibits GPe (external part of Globus pallidus) o 3) inhibits subthalamic nucleus o 4)positive feedback to GPi, which is an output nucleus o 5) that leads to more inhibition in the thalamic discharge o 6) which will lead to less excitatory output from the thalamus o 7) less excitatory output from the cortex o In Parkinsons: o If you lose those dopimanergic neurons from the SNc, it is going to cause decreased activity in the direct pathway and increased activity in the indirect pathway. o Both of those will increase the output of the GPi (globus pallidus internal part) and the SNr (reticular part of substantia nigra). o This will inhibit the thalamus which will cause diminished cortical output o This could underlie the bradykinesia and hypokinesia o Disrupting one little part of the circuit influences the whole functioning of the circuit. For the test only know the following: o There is a direct pathway that is excitatory, and an indirect pathway that is inhibitory. That is one theory of how parkinsons affects the working of the Basal Ganglia. Video: “Dissection of the human brain” - Heimer o Hypothesis: Claustrum is important for consciousness Cerebellum o Means Little brain o It has a cortical structure similar to the cerebrum, and it has subcortical nuclei. o It has various parts/lobes and those are defined by sulcal boundaries. o The output parts of the celebellum form peduncles Organization of the cerebellum (KNOW THIS) o Excitatory inputs via inferior and middle cerebellar peduncle o To cerebellar cortex o To Purkinje cells of cortex that send inhibitory output to cerebellar nuclei o Excitatory cerebellar nuclei project out via the superior cerebellar peduncle o Excitatory inputs enter the cerebellar cortex via the ______ and _____ cerebellar peduncles. Inferior and Middle Purkinje cells are output cells that target the subcortical nuclei o They are on the bottom layer of the cortex ML: molecular layer Band of purkinje cell layer Granular layer WM: white matter o Purkinje cells have many dendrites o Cells in granular layer send fiber to Purkinje layer which bifurcate as parallel fibers o Each parallel fiber synapses ~500 P-cells o In addition, climbing and mossy fibers o Climbing fibers come from the contralateral inferior olivary nucleus (near medulla). 4 They wrap around purkinje cells and make about 10 synapses o Mossy fibers synapse on granular cells which send projections up via those parallel fibers o green: single climbing fiber Red: single purkinje neuron o There are bout 15-26 million purkinje cells in the cerebellum and each make about 200.000 synapses There are 2 loops o [cortico-ponto cerebellar connections through MCP] Cortical projections go to the pons and then through the middle cerebellar peduncle (MCP) they target the purkinje cells (orange in slide) o Then you have the fiber coming up from the inferior olivary nucleus, those cross over initially and come up via the inferior cerebellar peduncle(ICP) (green) Different wording: Climbing fibers arise from the inferior olivary complex and enter via ICP o The purkinje neurons project to the subcortical nuclei. Those subcortico nuclei are output neurons that go via the thalamus back up to the cortex. (another loop) Function cerebellum: o Lateral hemispheres involved in movement and planning o Medial hemispheres involved in adjusting limb movements o Vermis involved in postural adjustment o Flocculus and vermis (middle parts) are involved in eye movement. o Cerebellum also involved in motor learning o Possibily cognitive function Receives input from visual, auditory, association and limbic cortices. Example of cerebellum and learning o Woman is trying to throw darts, gets prism glasses, which makes her see things adjusted a few cm compared to where it actually is, and then she throws without glasses. o She shows very off the first time with the glasses on, but she learns how to adjust and throws more accurate o Then you take the glasses off, and they over correct it, but again learn how to adjust. o Someone with damage to the cerebellum does not do this too well: evidence: cerebellum is involved in learning. Cerebellar ataxia o People can move, but the fine movements are not organized Development o Granule cells develop postnatally o Highly dependent on environment Think of child learning how to walk NOTES DO NOT INCLUDE NOTES OF THE HEIMER VIDEO Sensory System Receptors transduce energy o Vision: light is converted to chemical energy by photoreceptors AP o Auditory: air pressure converted to mechanical energy AP o Somatosensory: Mechanical energy activates mechanoreceptors (e.g., touch) AP o Gustatory(taste)/olfactory(smell): Molecules in air or saliva will fit to receptors AP o Pain: tissue damage releases chemical: acts like NT (neurotransmitter) o Sensory receptors _______ energy Transduce Example: feather touches arm: o Feather touches the hair on your arm. Down at the follicle there is a dendrite of a sensory neuron wrapped around it. o That will move the dendrite. o This causes stretch sensitive channels to open, which propagates to voltage-gated ion channels for sodium o o Recall: The way to get an action potential going was to have a voltage gated sodium channel. When that channel opened, sodium would rush into the cell. o This is the same idea, but the channel responds to the stretching of the dendrite: stretch leads to opening of sodium channels, sodium rushes into the cell, this leads to a local change in the potential, and if the local change is significant enough to reach threshold, the AP is propogated along the axons and get a nerve impuls. Receptive Fields o Neurons and receptors have “receptive fields” Only respond to specific stimulus o Receptor density determines sensitivity Fovea in the retina has high density of cone cells Tactile receptors more numerous in fingers than arm Better two point discrimination in fingers. If u put 2 pencil tips on your arm. Then u start moving those closer together while eyes are closed. At a point you think it’s only one pencil tip. The distance between the 2 pencils would be larger on your arm compared to on your finger. o Sensory receptors have_____ which means they only respond to specific stimuli Receptive fields Topographic organization o Topographic organization is a neural-spatial representation of the world o Different regions of the brain represent different aspects of the sensory input EX: Visual system is in the occipital lobe, temporal lobe for audition, parietal for somatosensory and frontal for motor and somatosensation Vision o Eye Retina is where the photoreceptors are located If you are looking at an image it gets flipped by the lens Light comes into the lens and passes to the back of the eye. The retina sits by the back of the eye. Optic nerve is the major output that goes to the thalamus Retina has layers with different cell bodies The sclera in the back is the white part of the eye Retina o Check slides for layers in the retina o Discuss two layers Layer of rods and cones Ganglion cells (inner layer) o Direction of information flow: Light is coming into the retina, but it is actually hits the “output layer” (ganglion cell layer) first, and only in the back of the retina it will hit the rod/cone layer Rods and cones impacting some of the same target neurons, so there is early integration of information. Output layer: Ganglion cell layer: These cells bundle up to form the optic nerve Slide: dissected Retina o IN the middle you see the fovea, and the optic disk left of that. o The optic disk is the eyes blind spot. Blind spot: o Blind spot because all the axons of the ganglion cells cord up to form the optic nerve, and because they are packing all these axons in such a small area, there is no room for photo receptors there (rods and cones). There are no photoreceptors in the blind spot. Photo receptors are required for the sensation of vision. The brain fills in the information for you, so you don’t have a hole in your visual field How to find this spot: If you hold the book at a certain length in front of you and you focus on a spot some of the book will disappear. (this is different when driving). Retina is regionally specified o Cone cells are highly concentrated in the fovea Function well in light, and are good at processing color o Rod cells are highly concentrated outside of the fovea, none in fovea Function well in dim light o The fovea is densely populated with _______ and not populated at all with ________ Cone cells / Rod cells Retinal neurons translate patterns of light into patterns of contrast o Visual light has leveral wavelengths within it. You can see this when light goes through a prism. o Humans have 3 different kinds o cone cells and rod cells. o Different cones absorb different wavelengths more efficiently S cones: Low wavelength – purple and blue Rods: Blue to grey wavelength M cones: Green spectrum L cones: Red Spectrum o Different people (even if not color blind) have different concentration of the photoreceptors o If you are color blind, there are glasses that can shift the light in a wavelength you can see. Ganglion cells have center surround receptive fields o Their axons form the optic neve, and have center-surround receptive fields o Center-surround receptive field: The way light hits the receptive fields determines how they are going to fire: On-center ganglion cells: If light hits the center, the receptive fields is such that the neuron will fire more intensely, but the outside of the receptive field indicates that the neuron with dampen its firing rate. Off center ganglion cells: If light hits the center of an off center ganglion cell it will dampen its firing. What this allows in the NS is the detection of boundaries. If you have a dark and light spot, and you have these receptive fields of the ganglion cells, it can determine the firing rate and that will change over the boundaries. The firing rate changes with the movement across the fields. Center-surround fields allows for edge detection. Without these ganglion cells, you will not see edges. Optical solutions: (check slide) its looks like they are moving: Apparent motion because some contrast changes processed faster then others, which activated motion sensitive cells. o Ganglion cells have ________ receptive fields Center-surround From retina to the brain o This is done through the optic nerve o Half of the visual field of each eye is going to cross to the contralateral hemisphere. o Look at how the arrow is represented in the eyes. Half of the arrow (inner half) go contra lateral. Each optic tract “looks at” the contra lateral visual field o The left visual field will be processed in the right hemisphere. The right visual field will be processed in the left hemisphere. o These projections of the optic nerve go to the lateral geniculate nucleus in the thalamus (first stop). And that crossing occurs at the Optic Chiasm and that turns into 2 optic tracts. Those go to the LGN in the thalamus. o The LGN has 2 type of cell layers Magnocellular layers (lower 2 layers) The neurons in here are very sensitive to movement and contrast Parvocellular layers (upper4 layers) Color and form information o From the LGN you need to get to the primary visual cortex in the occipital lobe. This happens via a secondary pathway of axons Primary pathway was from retina via optic nerve and chiasm to LGN. After the LGN the axons and sent to terminate in the strait cortex or primary visual cortex. This is in the calcarine sulcus. Part of it is called Meyers loop Check slide with blue and green tracts. From the optic radiation the terminations occurs in the calcarine fissure o The thalamic terminations go to layer 4 of the cortex o There is a prominent layer four input that denotes what is known as the primary visual cortex It is called that because it is the first cortical stop in the brain for visual information coming from the thalamus. It makes it look like there is a stripe, and that’s why it is also called the striate cortex. A lot of it (incl the calcarine surface) is in the medial surface and a lot reaches the occipital pole. It is called Broadman Area 17, and moves into broadman area 18 which has a different cytoarchitecture. Vision: Foveal representation o Foveal representation maps to the occipital pole o Much is buried in the calcarine sulcus Also called striate cortex (BA 17), or VI (primary visual cortex). o The top of the foveal representation maps to the bottom, and the bottom maps to the top o The more lateral parts of the visual field map to the more interior part of the calcarine fissure and extend to the gyri there. Vision: Columnar representation in visual cortex o If you see stimuli, for example a vertical facing line, there is a particular column or neurons in the cortex that goes down the 6 layers of cortex, there is a column that will respond maximally to the vertically oriented line, and minimally to a horizontally oriented line. o This preferential response changes if you move over the columns o These are called ocular dominance columns. o There are also color sensitive columns, so if you look down on a patch of cortex you can see how these are organized. o Neurons that respond similar tend to be next to eachother Damage to visual cortex o If you damage part of the visual cortex you would lose vision o If you damage the left calcarine fissure, you lose the right visual field: Hemianopia (lost half visual field) o If the lesion is smaller, you will have less visual loss: Quadrantanopia (lost ¼ visual field) o Even smaller: Scotoma (lost a smaller part of visual field) Dorsal and Ventral visual routes o You start in the calcarine fissure in the cortex (primary visual cortex) Parvocellular layers (LGN in thalamus) project to the calcarine fissure form and color Ventral root. WHAT pathway!! Occipital to Temporal lobe Magnocellular layers(LGN in thalamus) project to the calcarine fissure movement and contrast motion and location targets superior temporal sulcus and anterior occipital sulcus: WHERE/HOW!!(dorsal root) Where is it in the visual field, and how is it moving Occipital to parietal o It is much more complex than that! Look at the monkey visual map! Motion (V5/MT+) --> in anterior occipital sulcus o Part of dorsal visual stream: interested in processing moving things o Woman with motion blindness (Bilateral V5/MT+ lesions) “She had difficulty, for example, in pouring tea or coffee into a cup because the fluid appeared to be frozen, like a glacier” “In a room full of people, ‘people are suddenly here or there, but I have not seen them moving’”. Ventral stream: V4 - Color/ Fusiform Face Area o o Man with color blindness and prosopagnosia “Everything appears in various shades of grey” (V4 area lesion) “I can see the eyes, nose, and mouth quite clearly, but they just don’t add up. I have to tell by the clothes or voice whatever it is a man or a woman, as the faces are all neutral. I cannot recognize people in photographs, even myself.” Fusiform face area lesion – prosopagnosia Some people are born with this condition Visual tracts o There are also other pathways out of the retina, mainly through the thalamus o Geniculostriate tract (pattern analysis) – (talked about this before) LGN Area 17 Secondary I Secondary II Tertiary and paralimbic o Tectopulvinar system detection and orientation of visual stimuli – especially rapidly moving stimuli Pulvinary nucleus (part of thalamus Projects to superior culliculus Projects to Lateral posterior- pulvinar thalamic complex o Other projections go to the hypothalamus and are involved in Modulation of pupillary size Modulation of body temp, hormone production and circadian rhythm 8 thcranial nerve o 8 cranial nerve carries auditory and vestibular information Auditory = hearing Vestibular= body position and balance Audition – properties of sound Frequency (Pitch): High frequency more waves per second. Ampliture (loudness): Size of waves. High amplitude means louder Complexity (timbre): simple waves will be simple tones Range of human hearing: 20 – 20,000 Hz How do we hear sound o It starts with a sound wave, which is the movement of air molecules. o Sound wave is going to picked up by outer ear. o Sound waves travel through external ear canal and hit the eardrum. o Eardrum will vibrate o Auditory system amplifies this sound o Amplification occurs through the Ossicles (smallest 3 bones in the body) o Those bones will make contact with the cochlea (auditory nerve) Auditory nerve is the axons coming out of the cochlea (only 30.000 fibers) o The Major function of the ______ is to amplify sound Ossicles Where do the nerve cells of the auditory nerve originate? o They originate from the hair cells, which are sitting inside the cochlea on the organ of corti o There are outer hair cells and inner hair cells, and those sit on top a basilar membrane o The basilar membrane is rolled up in the cochlea Basilar membrane has a tonotopic organization: Basilar membrane responds to progressively higher frequencies along its length Thickest part: highest frequencies o The basilar membrane responds to progressively higher frequencies along its length. This defines the _____ or the basilar membrane. Tonotopic organization If you unroll the cochlea you can see how it works o Sound waves reach peak at different points on Basilar membrane depending on frequency o Travelling waves on basilar membrane stimulate hair cells in the organ of corti, in locations that depend on sound frequency o Inner hair cells are sensory cells and outer hair cells are amplifiers o _____ are sensory cells. _____ are amplifiers Inner Hair cells; outer hair cells If you have a max frequency on the basilar membrane it will stimulate the inner hair cells. o If the inner hair cells fire an AP, the AP will go along the Auditory nerve How do inner hair cells fire an AP? o Endolymph fills the semicircular canals and cochlea o Gelateour mass (G) couples each hair bundle to mechanical forces o Tip links to connect hair cells and increase chance of firing o Hair cells have Kinocilium, that extend out from the body of the cell. They impact the Gelatenous mass (G), which sits in an viscous fluid called endolymph. If the basilar membrane fires where the endolymph is, the gelatinous mass is going to vibrate and the hair cells will move. Each hair cells is connected by tiplinks to increase chance to fire AP. If the movement opens an ion channer sensitive to the movement of hair cells. If enough Ions move through that chancel, and AP will fire through the 8 cranial nerve What happens after the auditory information is sent out of the cochlea. The info goes up! st o It has to read the Cochlear nucleus (1 ear) o Superior olivary nucleus (2 ndear) 2 spots: Ipsilateral and contra lateral superior olivary nucleus Sound localization by arrival and intensity differences. Detects where the sound is coming from, by detecting the difference in the firing of the arrival and intensity. It is going to be different because there is space between your ears nd o Inferior colliculus (2 ear) o Medial Geniculate nucleus (2 ndear) (auditory thalamus) o Primary Auditory cortex (2 ndear) in transverse temporal gyrus Primary auditory cortex maintains tonotopic organization o Lateral parts respond to lower frequencies o Medial parts respond to higher frequencies Balance o Receptors in semicircular ducts detect angular acceleration of head o Vestibular system involved in balance, eye movement, body position in space o Balance is similar to audition. Endolymph circles through semicircular canals. o There are 3 major loops in the canals and they have a prefential direction for each. o They have little receptors in there and when the endolymph moves in a region it will move the receptor and if the receptor moves enough it will create a AP If you get seasick this system is over reacting. Medication dampens the vestibular nucleus’ response. Somato sensation o Receptors encode nature, location, intensity, and duration of stimuli o Different receptors for different stimuli Chemoreceptors (chemical differences eg. Pain) , thermoreceptors (temp), and mechanoreceptors (touch) Somatosensation: Receptive fields o 2 point discrimination receptive fields Narrow receptive field in finger tips and wide one in the arm. o The neurons will send projections to the spinal cord, via the dorsal root. Through the dorsal columns will send info up to the cuneate nucleus and the facilis nucleus up to the thalamus and then to the somatosensory cortex. Somatosensory modalities o Submodalities: Nocioception (pain & temperature) Hapsis (fine touch and pressure) Proprioception (body position) o Some sensory endings are encapsulated, others not (free nerve endings) o Receptors show adaptation Slow adapting respond less with continued stimulation Rapid adapting adapt quickly to signal change o Proprioception defines the sensation of ________ Body position Examples slow vs fast adapting o Slow adapting: strechting muscle. If muscle stretches the neuron will continue to fire o Rapid adapting: hair cell movement ion opening, and closes and u won’t feel it anymore Muscle spindles detect muscle length o Stretch receptors responds when muscle moves o Wrapping of dendrite around spindle o Receptors in muscles and joints detect muscle status and limb position Muscle spindles (muscle stretch) – depends on receptor type Golgi tendon organs (tendon stretch) – Rapid Joint receptors (join movement) – Rapid Touch and Position sense pathways o Finger touch Dorsal root ganglion spinal cord up through dorsal columns cuneate nucleus up medial lemniscus to thalamus primaru somatosensory cortex (parietal lobe) Somatosensory cortex: in the parietal lobe in the post central gyrus o Humunculus: large hands, lips and mouth o Also a somatotopic organization to some degree: more ventral parts of the post central gurys represent the face and mouth, and more dorsal parts the hand, and on the medial surface the lower limbs. o Also in the primary somatosensory cortex (post central gyrus) you have: BA: 3a – muscles BA 3b – Skin (slow) BA 1 – Skin (fast) BA 2 – Joints, pressure o Somatosensory cortex maintains a general ________ organization Somatotopic Gustation (taste) o Taste buds respond to chemicals in saliva (chemosense) o Chemicals bind to chemoreceptors o Four main chemical components: Sweet, sour, salty and bitter o Taste buds are distributed throughout the tongue and are innervated by cranial nerves VII, IX and X o o There is a higher sensitivity for bitter at the back of the tongue but you can also taste bitter anywhere else on the tongue. o After leaving the tongue, the fibers project ipsilateral (uncrossed) through the thalamus to the anterior part of the insula. In other mammals there are direct projections to the hypothalamus and amygdala but not in Humans and primates o _____ cortex is a primary termination for gustatory pathways The insula cortex Olfaction (smell) o Also a chemical sense o Airborn chemicals will reach the olfactory epithelium (in the nose). This epithelium is a collection of neurons with receptors that are sensitive to different chemicals in the air. o Olfactory epithelium contains chemoreceptors of different types, which synapse on glomeruli (interneuron). The axons of the glomeruli form the olfactory tract o o The axons initially go through the cribriform plat, which is porous because it allows the axons to go through there o Pattern of glomeruli activation that determines smell. The combination of chemicals will determine the smell. Dogs have about 100 times the density of receptors on epithelium Women tend to have a better sense of smell than men do. o The olfactory epithelium contains ________ Chemo receptors After the glomeruli axons leave in form of the olfactory tract they have to go somewhere:
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