Biopsychology and the Brain - Part 2 PDF

THE BRAIN PART 2 1 ELECTROENCEPHALOGRAPHY (EEG) Electrodes are placed on the scalp to measure electrical activity due to neural activity The EEG signal is averaged over many occurrences (to reduce effects of random neural firing) – this should be the same event (e.g. onset of stim...

THE BRAIN PART 2 1 ELECTROENCEPHALOGRAPHY (EEG) Electrodes are placed on the scalp to measure electrical activity due to neural activity The EEG signal is averaged over many occurrences (to reduce effects of random neural firing) – this should be the same event (e.g. onset of stimulus, pressing a button, etc.) Electrodes record a series of positive and negative peaks The i) timing and ii) amplitude of peaks reflects certain cognitive processes 2 3 1 4 Requirements for detecting a signal § Synchrony § Spatial proximity § Parallel geometric configuration 5 6 2  Pros and Cons Advantages include... § Very high temporal resolution (msecs) § Non-invasive § Relatively suitable for children and patients But... § Poor spatial resolution § Anatomical uncertainty 7 POSITRON EMISSION TOMOGRAPHY (PET) PET measures local blood flow (rCBF) A radioactive tracer injected into blood stream The tracer takes up to 30 seconds to peak 8 9 3  MAGNETIC RESONANCE IMAGING (MRI) 10 Increase in information processing Increase in neural activity Increase in venous oxygenation Increase in fMRI signal 11 HOW DOES FMRI WORK? Deoxygenated hemoglobin is magnetic, oxygenated hemoglobin is not. So, the amount the magnetic field is perturbed depends on the proportion of deoxygenated hemoglobin in the blood. deO2 Hb perturbs the magnetic field deO 2Hb 12 4 13 With the aid of functional magnetic resonance imaging, neuroscientists have been hard at work on Allen’s fantasy. Under controlled conditions, they can tell from a brain scan which of two images you’re looking at. They can tell whether you’re thinking of a face, an animal, or a scene. They can even tell which finger you’re about to move. 14 Pros and Cons Advantages include... § Non-invasive (for MRI, PET draws on radiation) § Good spatial resolution (though not as high as single- unit recording) But... § Poor temporal resolution § Limitations in interpreting activation (excitation or inhibition?) 15 5  The previous “observation” methods tell us that a region is active but not that it is necessary Which brings us to our next set of methods... 16 METHODS OF INTERFERENCE We can study the impact of interfering (including removing / damaging) a region, allowing us to ask: “What functions remain?” “Which brain locations are crucial for a cognitive function?” “Can two functions be disrupted independently of each other?” 17 NEUROPSYCHOLOGICAL PATIENTS 18 6  Alzheimer’s disease 19 HOW CAN WE ANALYZE LESION PATIENTS? 1) Group by syndrome: For investigating neural correlates of a disease pathology (e.g. Alzheimer’s) 2) Group by behavioral symptom: Can potentially identify multiple regions that are implicated in a behavior, without noise from symptom heterogeneity 3) Group by lesion location: Useful for testing predictions from functional imaging and focusing on the role of particular structures 20 GROUP STUDIES CAN ESTABLISH STRUCTURE- FUNCTION RELATIONSHIPS WITH MORE PRECISION 21 7  NEUROPSYCHOLOGICAL EXPERIMENTS What are the strengths of this method? What are the shortcomings? 22 TRANSCRANIAL MAGNETIC STIMULATION (TMS) Temporarily disrupts a cognitive function (“virtual lesion”) A coil containing a wire that carries an electric current is placed near the participant’s head A rapid change in the current creates a magnetic field The magnetic field induces a current in nearby neurons (causing them to "fire", i.e. generate action potentials) 23 24 8  Pros and Cons Advantages include... § Temporary effects – no (patient) confound of brain reorganization § A focal lesion § Under the experimenter’s control But... § Some areas cannot be stimulated § Uncertainty over the size of each stimulation area § May be affecting an excitatory or inhibitory area 25 Deep Brain Stimulation Pros and Cons? 26 27 9 CEREBROSPINAL FLUID (CSF) CSF is found in the ventricles and surrounds the brain It provides protective cushioning (buoyancy) It also regulates the extracellular environment (waste products, hormones, etc.) 28 EMBRYONIC NERVOUS SYSTEM Forebrain Midbrain Hindbrain Be sure to learn how these sections of the nervous system differ in their roles 29 CEREBRAL CORTEX Neocortex: Outermost Layer Four Lobes: Frontal Parietal – occipital (vision) – temporal (hearing, language processing, memory) – frontal (intelligence, Occipital personality, voluntary muscles) – parietal (spatial location, Temporal attention, motor control) 30 10  SOMATOSENSORY, MOTOR, AND ASSOCIATION CORTEX Somatosensoy Cortex (in parietal lobe) – body sensations / touch Motor Cortex (in frontal lobe) – voluntary movements Association Cortex (75% of cortex) – not sensory or motor, but associations between 31 THE HEMISPHERES Corpus Callosum large bundle of axons that connects the two hemispheres of the brain 32 HEMISPHERES OF THE CORTEX Hemispheric specialization of function – both hemispheres are involved but one can be more important than the other left hemisphere - verbal processing, speech, grammar right hemisphere - spatial perception, visual recognition, emotion 33 11  ENDOCRINE SYSTEM Set of glands { pituitary, thyroid, parathyroid, pancreas, adrenal, ovaries, testes that regulate the body by secreting hormones {chemical messages into the bloodstream { relatively slow communication system interconnected with the nervous system 34 GENES AND THE ENVIRONMENT: GENETIC EXPRESSION Genotype Ø genetic heritage + Effects of experience environment alters how genetic traits develop = Phenotype Ø observable characteristics both physical & psychological Gene X Environment Interaction 35 12