Research Methods Neuroscience Research Focus Structure How is it built How is it connected What does it look like Function How does it work What does it do Why is it important Studying the Living Human Brain Neuroimaging CT computerized tomography PET positron emission tomography MRI magnetic resonance imaging fMRI 1991 functional MRI Computerized Tomography CT Uses multiple x rays to construct a 3D image X ray penetrates body and absorbed by various radiopaque tissues Digital reconstruction within plane of slice Positron Emission Tomography PET Injection of a radioactive substance 2 deoxyglucose into the bloodstream which is taken up by parts of the brain according to how active they are Baseline measure subtracted from activity during task Positron Emission Tomography PET Injection of a radioactive substance 2 deoxyglucose into the bloodstream which is taken up by parts of the brain according to how active they are Magnetic Resonance Imaging MRI Magnetic field and radio waves used to produce high resolution structural images of the brain Functional Magnetic Resonance Imaging fMRI Changes in blood flow and blood oxygenation in the brain i e hemodynamics are closely linked to neural activity Ratio of oxyhemoglobin to deoxyhemoglobin determines areas of brain activation Functional Magnetic Resonance Imaging fMRI Measures brain activation by detecting increases in oxygenenated blood directed at active neural structures Difference Image BOLD blood oxygen level dependent signal Brain Recording Methods Electroencephalography EEG Event Related Potential ERP Magnetoencephaolgraphy MEG Single cell recording Electroencephalogram EEG Scalp electrodes provide information about the activity of large populations of neurons Used to study sleep and diagnose seizures Event Related Potential ERP Series of EEG responses to environmental stimuli Useful in studies of perception cognitive processes Event Related Potential ERP Series of EEG responses to environmental stimuli Useful in studies of perception cognitive processes BA MBA Technique Description EEG Sums electrical activity of neurons between two electrodes detects fast changing brain activity but is poor at localizing it Temporal Resolution Spatial Resolution 1 ms 10 15 mm 1 ms 0 5 mm CT Forms 3D image of brain by combining X rays of cross sections of brain images structure and damage MRI Measures variations in hydrogen concentrations in brain tissue images structure and damage 3 5 s 1 1 5 mm PET Image produced by emissions from injected substances that have been made radioactive tracks changing activity detects receptors etc 45 s 4 mm fMRI Detects increases in oxygen levels during neural activity tracks changing activity 1s 1 2 mm Magnetoencephalography MEG Brain s magnetic output is assessed Skull is transparent to magnetism not electricity making MEG less distorted than EEG Localization of activity is possible Superconducting quantum interference device Neurophysiology Extracellular Recording In vivo recording of electrical activity of one or more neurons Electrode located near not within neuron Correlate with behavioral cognitive eventsgood way to figure out how individual neurons react when the subject is conducting a particular task Neurophysiology Intracellular Recording Brain slice 0 5 mm wide Vicoscopy can record from an individual neuron Inject current depolarizing neuron causing Action Potential Brain stimulation Transcranial Magnetic Stimulation TMS Lesions BRAIN MANIPULATION METHODS Optogenetics VIDEO http video mit edu watch optogenetics controlling the brain with light 7659 Brain Stimulation Pass small current to activate particular brain regions Delineate functional properties of neural Clarify roletissue of particular substrates prior to surgery Brain mapping When people went into surgery pinfield poked at neurons and asked the participants to tell him what it affected and from this experiments he created a map of the brain Homunculus Brain Stimulation Olds Milner pleasure pathways Ratbots respond to stimulation by changing direction Transcranial Magnetic Stimulation TMS Applies strong and quickly changing magnetic fields to surface of skull that can interrupt brain function Transcranial Magnetic Stimulation TMS Applies strong and quickly changing magnetic fields to surface of skull that can interrupt brain function rTMS successfully used to temporarily change brain activity immediately below stimulation site Mainly used for psychoactive disorders Schizophrenia Depression Lesions Humans Trauma Strokes Tumors Infection Toxins Neurological disease Utilize lesions to infer what the area with the lesions purpose is Lesions Animals Ablation Heat Electrolytic burns a hole in the brain Neurotoxic kill only a particular portion of the brain and only killing neurons not axons Cooling reversible inactivation pretty much turn neurons off for a little while Stereotaxic Surgery Brain atlas Stereotaxic Surgery Brain Structure Methods Histology Tract tracing Diffusion tensor imaging Histology Study of microscopic structure and tissue Tissue to be viewed must be 1 Fixed by freezing or formaldehyde 2 Sliced thinly by a vibrating microtome or cryostat 3 Mounted on microscope slides 4 Stains applied to highlight structures of interest 5 Viewed with a microscope e g Light Confocal Electron Stain Types Nissl stain Cell bodies of neurons Example Cresyl Violet Stain Types Golgi stain Single cells Darkly stains full neuron Randomly stains 5 of neurons Stain Types Myelin stain Stains myelin that wraps and insulates axons Identifies neural pathways Tract Tracing Anterograde Moving forward Where a pathway ends Retrograde Moving backward Where a pathway begins Anterograde Tracing Neural Connections Retrograde Diffusion Tensor Imaging DTI allows direct in vivo examination of aspects of the tissue microstructure DTI takes advantage of diffusion anisotropy to provide excellent details of the brain e g it enables mapping of the orientation of the white matter tracts Human Connectome Project Neurochemical Methods Neuropharmacology Microdialysis Immunocytochemistry Neuropharmacology Drugs chemical substances that alter biochemical functioning Receptor antagonists Inhibitors of neurotransmitter receptors block Receptor agonists Mimic actions of naturally occurring neurotransmitters enhance Methamphetamine Neuropharmacology Mainly drugs are given orally but sometimes In animals drug infusion can be localized through use of guide cannula Drugs can be infused