PSY3010S - Research in Neuropsychology.pdf
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The Cell Doctrine WEEK ONE:Research in Neuropsychology Galen (130 - 201 AD)-Ventricular Localization Hypothesis(first anatomical...
The Cell Doctrine WEEK ONE:Research in Neuropsychology Galen (130 - 201 AD)-Ventricular Localization Hypothesis(first anatomical theory) esearch Methods One R - Mental and spiritual processes arise reside in brain’s ventricles What is neuropsychology - Early attempt to localize mental function - Later known as The Cell Doctrine (innacurate) Earliest Discoveries Anatomical Discoveries and Spiritual Soul Trephination (Stone Age) Andres Vesalius (1514-1564):Shift away from VentricularTheory(founder of - Form of brain surgery human anatomy) - Drill holes through the skull to relieve pressure - Overall structure and mass mediate mental processes - Reasons: - Groundwork for a more integrated understanding of brain function 1. Medical Emergency 2. “Magical” form of healing (eg epilepsy or schizophrenia) R ene Descartes (1596-1650):Mind-Body Dualism(firstunderstanding of mental - Similar procedures were done today health) - Split between mental processes and physical abilities - Pineal gland control center of mind and body - unique because there is only one and it is in the middle of brain Ancient Greek Perspectives Hippocrates (460-377BCE):Brain Hypothesis(idea thatbrain is source of all behaviour) - Brain controls senses and movements - Understood contralateral control - Emotions arise in the brain - Behaviour is not divinely controlled but rather medical Plato (420-347 BCE):Tripartite Soul Concept - Soul divided into reason, spirit, and appetite - Reason arises in the brain Aristotle (384-322 BCE):Cardiac Hypothesis - The heart is the seat of thought and emotion Localization Theory Integrated Theories Franz Gall (1758 -1828):Localization Theory and Phrenology Hughlings Jackson (1835-1911): Jackson’s functional model - Localization theory: - Higher mental function composed of simpler functions Brain composed of independent organs, each responsible for specific - Hierarchical organization of brain: personality or cognitive trait Lower levels = basic functions - Phrenology: Higher levels = complex thought and behaviour Personality and cognitive traits determined by size of brain area/shape of - Damage to higher levels result in “dissolution” of complex functions, revert to skull (size of brain area = amount of skill in that area) basic functions Era of Cortical Localization Alexander Luria (1902-1977): Luria’s Functional Model Paul Broca (1824-1880)Localization of expressivelanguage - CNS Divided Into Units: - Production of language localized to region of the left frontal lobe Unit 1: brainstem and associated areas = regulate arousal and Carl Wernicke (1848-1904)Localization of receptivelanguage maintain muscle tone - Understanding language is localized to region of the left temporal lobe Unit 2: posterior areas of cortex = reception, integration, and analysis of sensory information Unit 3: frontal and prefrontal lobe = planning, executing and verifying behaviour - Behaviours have unique functional systems, each have unique pattern of interaction among units - Pluripotentiality: one neural structure can fulfillmultiple functions, depending on the functional network and pattern of co-activations displayed at any given time Critique of Localization Theory - Plasticity: the ability of the brain to change orreorganize the functioning of its Sigmund Freud (1856-1938)Complex Networks in Brain structures and neural mechanisms - Cognitive function involves complex networks of regions in the brain - Need to understand connectivity and interactions to understand behaviour (Relatively) Modern Neuropsychology and cognition Technological advancements (eg. neuroimaging) Expansion of research areas (eg. cognitive neuroscience) Localization vs Equipotentiality Henry Hecaen (1912 - 1983) Pierre Flourens (1794-1867):Equipotential theory - Demonstrated functional properties of the RH - Brain regions have potential to carry out most functions Arthur Benton (1902 - 2007) - Regions can compensate for damaged areas - Developed neuropsychological measures for RH Karl Lashley (1890-1958):Principle of mass action Oliver Zangwill (1913 - 1987) - Each part of brain participates in more than one function - Showed language in left-handed people may be localized to the RH - Extent of behaviour impairment is directly proportional to mass of removed Norman Geschwind (1927 - 1984) tissue - Behavioural disturbances due to disconnections between brain pathways Muriel Lezak (1970s) - Pioneered the assessment approach in neuropsychology esearch Methods 2 R Structural Imaging Neurohistory used to quantify brain structure Definition: Study of the microscopic structure of brain tissue C heaper and more widely available Key techniques: - Golgi stain: visualizes entire neurons - including dendrites and axons X-Ray (late 1970s) - Nissl stain: highlights cell bodies What it is: Uses and significance: - Visualize skull and large abnormalities in brain - Investigating neuronal organization and connectivity How it works: - Diagnosing brain tissue abnormalities - Electromagnetic waves are absorbed at different rates by different tissues Nissl stain - Dense structures, like bone, absorb more X-rays and appear white on image What it is: - Less dense structures, like tissue, appear darker - Visualization of cell body and nucleus of neuron Application: How it works: - Quickly assess bone injuries and detect major tumors or large bleeds - Uses simple dyes Advantage: Uses: - Universally available technology - Study neuronal density - Inexpensive - Study arrangement of neurons in different brain regions - Good visualization of the skull (works for skull fractures) - Helps with pathology (can’t see cell body if axon is injured) Disadvantage: Limitations: - Radiation exposure can destroy diseased tissue - Limited structural information - 2D images - Technical variability - Little differentiation between bone and CSF Golgi stain What it is: - Visualization of entire neuron (cell body, dendrites, axons) How it works: - Uses silver chromate to stain individual neurons Uses: - Study complete structure of neuron - Study complex networks and connections between cells - Understand intricate wiring of the brain by mapping distribution of axons and dendrites - Identify neuron types Limitations: - Selective staining: Only stains small percentage of neurons - Can only be used on dead tissue - Complex preparation: staining process is technically demanding - Cannot see inner structure CT Scan MRI What it is: What it is: - Provides cross-sectional images of the brain - Highly detailed image of the brain How it works: How it works: - Machine sends X-ray beams through body from multiple angles - Machine uses magnets to align the hydrogen atoms in body - X-ray detectors on the opposite side of machine measure the amount of - Radio wave sent through, knocking the hydrogen atoms out of alignment X-rays that pass through body - When the radio wave is turned off, hydrogen atoms realign and send out - Data sent to computer and computer creates image signals Uses: - Machine detects these signals and a computer turns them into detailed - Determine presence of lesions, images - structural deviations, and tumors Uses: Advantages: - Determine presence of lesions, - Quick (±10-15 minutes) Advantages: - Inexpensive - Safer for repeated exposure (no radiation) - Widely used in research - Highly detailed images (more sensitive, better for diagnosis) - Quiet Limitations: - Good for emergencies - Long (±30-60 minutes) Limitations: - expensive - Poor resolution of grey and white matter structures - Uncomfortable due to - No information about function - enclosed space and loud noises - Harmful with excessive exposure - structural deviations, and tumors Research Methods 3 PET (Positron Emission Tomography) unctional Neuroimaging F What it is: the use of neuroimaging technology to measure an aspect of brain function - Imaging technique that visualizes metabolic processes in the brain - Uses radioactive tracers to detect functional changes in brain tissue fMRI (Functional Magnetic Resonance Imaging) How it works: What is it: - Radiotracer (usually glucose) injected - Measures brain activity by detecting changes in blood flow - Tracer accumulates in areas with high metabolic activity How it works: - As tracer is metabolized, they emit gamma rays - Blood-Oxygen-Level Dependent (BOLD) Signal: - Gamma rays are detected and computer generates image showing metabolic Increased neuronal activity > increased blood flow > higher oxygen activity levels > stronger MRI signal Uses: Uses: - Studying brain metabolism, blood flow, and neurotransmitter activity - Brain mapping: identifies areas of the brain involved in specific functions - diagnosing and monitoring neurological disorders - Patient performs a task during the process Advantages: - Clinical use: pre-surgical planning, understanding brain disorders - Functional imaging: provides information on brain function and metabolism Advantages: - Early detection: can detect abnormalities before structural changes occur - Non-invasive: no need for injections or radiation Limitations: - High Spatial Resolution: detailed images of brain activity - Radiation exposure Limitations: - Cost and availability - Temporal resolution: slower compared to electrical activity measurements like EEG - Motion sensitive: patient must remain still during the scan SPECT (Single Phonton Emission Computed Tomography) Electrophysiological Procedures What it is: EEG (Electroencephalography) - Imaging technique that visualizes blood flow and activity in the brain What it is: - Uses radioactive tracers to detect functional changes in the brain tissue - Records electrical activity of the cortex How it works: - Measures brain waves and patterns - Radioatracer injection How it works: - Tracer uptake - Electrodes detect electrical signals produced by neurons - Detection - Signals amplified and recorded by a computer Uses: - Different brain wave patterns (e.g. alpha, beta, delta, theta) are analysed - Diagnosing and monitoring neurological conditions Uses Advantage: - Diagnosing and monitoring epilepsy and sleep disorders - Functional imaging: provides information on blood flow and brain activity - Monitoring brain activity during anesthesia and surgery - Less expensive Advantages: Limitation: - Non-invasive - Radiation exposure - High temporal resolution: can capture rapid changes in brain activity - Lower spatial resolution compared to PET - Real-time monitoring Limitations: - Limited spatial resolution: - limited ability to pinpoint the location of brain activity - Requires a controlled environment to avoid external electrical interference EP’s (Evoked Potentials) What is it: - Measures brain’s response to specific stimuli - Types: auditory, visual, somatosensory How it works: - Specific stimuli are presented to patient while electrodes record brain activity - Electrical responses represent the timing and strength of neuronal pathways Applications: - Assesses sensory pathway integrity - Diagnosing & monitoring multiple sclerosis and other neurological conditions Advantages: - Specific - Objective measurement - Non-invasive Disadvantages: - Requires specialized equipment and expertise - Limited specificity: does not provide detailed anatomical information - Requires controlled environment Cerebrospinal Fluid Studies Cerebrospinal Fluid What is it: - CSF studies involve analysing the fluid that surrounds the brain and spinal cord How it works: - Lumbar puncture/spinal tap Applications: - Diagnosing neurological conditions (e.g. infections, abnormal proteins) Advantages: - Detailed diagnostic information: comprehensive data on chemical and cellular composition of CSH - Direct access to CNS: allows for direct precise diagnosis Limitations: - Invasive: procedure can be uncomfortable and carries risks such as headache, bleeding or infection - Procedure time: takes longer and requires more preparation
