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1: Introduction Cognitive Neuroscience David Eagleman Jonathan Downar Chapter Outline Who Are We? In Pursuit of Principles How We Know What We Know Thinking Critically about the Brain The Big Questions of Cognitive Neuroscience The Payoffs of Cognitive Neuroscience 2 Who Are We? The Mission of Cognitive Neuroscience Neuroscience is a Relatively New Field 3 Who Are We? The brain is made of neurons and glia, each containing a copy of the genome. There are nearly 100 billion of each of these types of cells. A typical neuron makes about 10,000 connections to other cells. Together, they form a three-pound organ that has the consistency of Jell-O. 4 Different Views of the Brain 5 The Mission of Cognitive Neuroscience Determine how the brain processes information, builds memories, and makes decisions. Figure out what makes us who we are. 6 The Mission of Cognitive Neuroscience Emergent Properties Characteristics of a system that are not part of the individual components that make up the system. Arranging all of the molecules into a cell, then into organs, and into a body can produce a living, conscious individual. Cognitive neuroscience seeks to understand these emergent properties. 7 Neuroscience is a Relatively New Field Combines biology and psychology to connect neural functions to behaviors. “Neuroscience” was first used in the 1960s. 8 Neuroscience is a Relatively New Field Every year, nearly 30,000 researchers, fellows, students, and health professionals attend the annual meeting of the Society for Neuroscience. 9 Neuroscience is a Relatively New Field Rapid growth of the field due to Greatly increased research in and understanding of biology. Greatly increased computing power at everlower prices. New theoretical approaches to the study of perception, learning, reasoning, and disease states. 10 In Pursuit of Principles The Functions behind the Form Which Parts Matter? What Is the Brain For? 11 Which Parts Matter? Explanations in cognitive neuroscience can be at the level of individual molecules or at the level of systems or neurons. All thoughts, memories, moods, and decisions are brought about by the physical substance of the brain. Alterations to the anatomy or chemistry of the brain result in changes to behaviors. 12 Which Parts Matter? 13 What Is the Brain For? The brain and therefore our thoughts and behaviors are shaped by evolution. Adaptations Mechanisms such as behaviors or physical traits that enhance the reproductive success of organisms that possess them. Our current thoughts or behaviors are adaptations that benefitted our ancestors. 14 What Is the Brain For? The “mind” seems separate from the brain, apparently non-physical. Research suggests that the mind is a product of the brain. All of our thoughts and behaviors result from the interactions of the physical parts of the brain. 15 How We Know What We Know Connectional Methods Correlational Methods Lesion Methods Stimulation Methods A Toolbox of Complementary Methods 16 How We Know What We Know Scientists have studied the brain for 150 years, trying to link the brain with behavior. Such studies have used techniques from microscopes to inserting genes into existing cells. 17 How We Know What We Know 18 Connectional Methods The function of a neuron depends on its input and output. Tracing these connections can tell neuroscientists what the cell does. It is possible to label cells that provide input to the neuron as well as the cells that the neuron sends messages to. 19 Connectional Methods Diffusion tensor imaging provides a way to map these connections in a nondestructive way in living brains. 20 Connectional Methods 21 Correlational Methods Researchers observe brain activity while the subject performs a particular behavior. Observing how brain activity changes as behavior changes provides information about the brain regions that are important for that behavior. 22 Correlational Methods Invasive Methods Microelectrodes can be implanted in the brain to record the electrical activity of individual neurons or groups of neurons. Microdialysis samples the chemical makeup and concentration of fluid in the brain. Voltammetry measures the levels of neurotransmitters in a tissue by monitoring voltage changes in the probe. 23 Correlational Methods Less Invasive Methods Electroencephalography (EEG) places electrodes on the scalp to monitor electrical activity in the brain. Magnetoencephalography (MEG) monitors the very small changes in the magnetic field around the head that result from the electrical activity of the brain. 24 Correlational Methods 25 Correlational Methods Indirect Methods Positron emission tomography (PET) studies inject small quantities of radioactive molecules into the body and monitoring how they are distributed in the body. Magnetic resonance imaging (MRI) enables researchers to visualize the structure of the brain in detail without exposing the subject to radiation. 26 Correlational Methods MRI Techniques Functional Magnetic Resonance Imaging (fMRI) can map blood flow and oxygenation to identify what parts of the brain are active during particular tasks. Diffusion Tensor Imaging (DTI) identifies connections between different regions. Voxel-based morphometry (VBM) maps the shape and thickness of brain regions. 27 Correlational Methods 28 Lesion Methods Lesions are areas of the brain that are damaged by disease or injury. Traumatic brain injuries, stroke, or tumors can result in lesions that affect behaviors. In the 1860s, the neurologist Paul Broca studied patients who had difficulties producing speech. 29 Lesion Methods 30 Lesion Methods Caveats to Lesion Studies Lesions are rarely small enough and specific enough to affect just one brain area. The lesion may spare enough of the tissue that the function is preserved, making it appear that that brain region is not involved in the behavior. Researchers must be careful to characterize the deficit precisely. 31 Stimulation Methods Researcher stimulate or increase the activity in a brain region and observe how behaviors change. Penfield and Jasper used electrical stimulation of brain regions to map the sensory and motor areas. Transcranial magnetic stimulation (TMS) uses electromagnetic coils to activate neurons in a particular region of the brain. 32 Stimulation Methods 33 Stimulation Methods Repetitive transcranial magnetic stimulation (rTMS) can be used to treat depression. Transcranial direct current stimulation (tDCS) applies a direct current to the scalp to inhibit neurons adjacent to the positively-charged cathode and stimulate neurons adjacent to the negativelycharged anode. 34 Thinking Critically About the Brain Is the Brain Equipped to Understand Itself? Biases and Pitfalls in Human Cognition A Toolbox of Critical-Thinking Techniques 35 Is the Brain Equipped to Understand Itself? The brain has evolved to control three specific classes of behaviors: Homeostatic behaviors, which maintain a normal range of survival parameters. Agonistic behaviors, which defend against rivals. Reproductive behaviors, which promote the continuation of the species. 36 Is the Brain Equipped to Understand Itself? Maintaining the body’s balance of energy, temperature, hibernation, and other critical parameters for one’s own survival Defending against hostile rivals or predators, establishing territory or dominance over rivals, and seeking out prey to sustain one’s own survival Seeking out mates, procreating, and prompting the survival of one’s own offspring 37 Biases and Pitfalls in Human Cognition The anchoring bias refers to the tendency to be overly influenced by a single observation, typically the first observation. The confirmation bias is the tendency to seek out and emphasize information that matches our existing beliefs. 38 Biases and Pitfalls in Human Cognition 39 Biases and Pitfalls in Human Cognition There is a long list of biases and heuristics that adversely affect our ability to observe and draw accurate conclusions about our own brain. Availability heuristic Affect heuristic Illusory correlation Belief bias 40 A Toolbox of Critical-Thinking Techniques The scientific method provides a systematic way to study a process and avoid biases and heuristics. Make observations about the world. Develop a hypothesis to explain the observations. Generate testable predictions about the hypothesis. Perform experiments to test the predictions. 41 A Toolbox of Critical-Thinking Techniques The results of one experiment help to refine the hypotheses for the next experiment. Experiments are repeated and extended to show they are reproducible. Results are subjected to independent peer review to reduce the biases that may have been introduced by the experimenter. 42 A Toolbox of Critical-Thinking Techniques Findings are reviewed by peers and replicated or refuted by further experiments. 4. Experimental testing of predictions: requires careful measurement and comprehensive efforts to control for any additional factors that could influence the observations. Experiments are designed to test the predictions of the hypothesis against alternatives. 1. Observation: Careful, repeated measurements using standardized techniques Overcoming bias: Standardization of measures; Disconfirmation of hypothesis; Peer review of findings; Replication of results; Progress by iterations 2. Generation of specific and testable predictions: if our hypothesis X is true, then we ought to be able to observe other phenomena A, B, and C. Observations lead to research questions. 2. Development of a hypothesis: a proposed explanation for the observations in question; a good hypothesis should be falsifiable. Competing hypotheses lead to competing predictions. 43 The Big Questions in Cognitive Neuroscience 2. 3. 4. 5. Why Have a Brain at All? How is Information Coded in Neural Activity? How Does the Brain Balance Stability against Change? How Does Vision Have So Little to Do with the Eyes? 44 The Big Questions in Cognitive Neuroscience 6. 7. 8. 9. How Does the Brain Stitch Together a Picture of the World from Different Senses? How Does the Brain Control Our Actions? What is Consciousness? How Are Memories Stored and Retrieved? 45 The Big Questions in Cognitive Neuroscience What Do Brains Sleep and Dream? 11. How Does the Human Brain Acquire Its Unique Ability for Language? 12. How Do We Make Decisions? 13. What Are Emotions? 14. How Do We Set Our Priorities? 10. 46 The Big Questions in Cognitive Neuroscience How Do I Know What You’re Thinking? 16. What Causes Disorders of the Mind and the Brain? 15. 47 The Payoffs of Cognitive Neuroscience Healing the Disordered Brain Enhancing Human Abilities Blueprints for Artificial Cognition Brain-Compatible Social Policies 48 Healing the Disordered Brain Depression affects as many as 1 in 10 individuals. Techniques such as rTMS and deep brain stimulation have been identified that can help alleviate the symptoms of conditions such as depression, Parkinson’s disease, and obsessive-compulsive disorder. 49 Healing the Disordered Brain 50 Enhancing Human Abilities Understanding how humans make decisions can provide insight into how to encourage us to make better decisions. Brain interface devices, such as cochlear implants and implanted electrodes to enable paralyzed patients to move devices outside their own body, can restore lost functions to individuals. 51 Enhancing Human Abilities Can we create new senses for humans? https://ted.com/talks/david_eagleman_can _we_create_new_senses_for_humans 52 Blueprints for Artificial Cognition Researchers are learning from the brain to improve the abilities of our computing devices, such as speech recognition, locomotion, and object recognition. Such artificial “neural networks” are now being used to recognize patterns of brain activity in brain imaging studies. Much remains to be done to find artificial equivalents to much human cognition. 53 Brain-Compatible Social Policies Eyewitnesses are very compelling in the courtroom, but are notoriously unreliable. Cognitive neuroscience can help understand and explain the factors that influence the memory of such witnesses. 54 Brain-Compatible Social Policies 55 Brain-Compatible Social Policies An increased understanding of the neuroscience of addiction can inform our policies regarding punishment and treatment of addicts. Such research suggests ways to attack the demand for the drugs within the reward system of the brain. 56 Brain-Compatible Social Policies Modern neuroscientific research has important implications for criminal punishment and rehabilitation. It is estimated that about 25% of the American prison population has a mental illness, so providing appropriate care is important. 57