Assignment: Brain Research history

Assignment: Brain Research history

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Assignment:  The History of Brain Research

• Hippocrates and Galen proposed encephalocentric explanations of behavior that focused on the brain as the chief source of behaviors, thoughts, and feelings. Aristotle supported a cardiocentric theory that regarded the heart as the source of all behavior.

• In the Western world, cardiocentric theories did not give way to encephalocentric expla- nations of behavior until the time of Galen in the second century.

• The modern concept of the brain and brain function did not develop until controlled experiments were conducted in the early 19th century.

• The earliest investigators of the brain disagreed about whether specific behaviors could be localized to discrete brain structures (localization) or whether the entire brain contrib- utes to any given behavior (holism). Research on the motor cortex in dogs, monkeys, and people supports the concept of localization by showing that the motor cortex is topo- graphically organized in such a way that specific cells in the motor cortex control certain muscles in the body.

Studying the Brain and Behavior • Many fields of inquiry are concerned with studying the relationship between the brain and

behavior, including behavioral and cognitive neuroscience and physiological psychology. • Neuroscience is a multidisciplinary approach to studying the brain. Behavioral neuroscience

involves bottom-up research strategies that begin by studying the neuron and its interac- tion with other neurons. Cognitive neuroscience involves top-down research strategies that manipulate cognitive events like problem solving to produce an effect on neural function- ing. Physiological psychology is often used interchangeably with behavioral neuroscience. Bottom-up scientific approaches often require the use of nonhuman research subjects.

Brain Lesions and Brain Stimulation • The earliest techniques used to study the brain and behavior were brain lesioning and

stimulation. • Lesioning involves disrupting the function of a particular area of the brain. Ablations

are typically performed to remove tissue from the cerebral cortex, whereas subcortical lesions are produced by direct current (DC) electricity, radio frequency current, or ionizing radiation.

• Brain stimulation involves causing a part of the brain to become active and can be accom- plished using alternating current (AC) electricity, stimulating chemicals, or transcranial magnetic stimulation.

Recording Brain Activity • Brain activity can be recorded using electroencephalography (EEG), magnetoencephalog-

raphy (MEG), single photon emission computed tomography (SPECT), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI).

• Electroencephalography (EEG) permits recording the electrical activity of the brain. In the event-related potential procedure, the timing and location of brain activity in response to a stimulus are identified.

• Magnetoencephalography (MEG) permits measuring the magnetic fields generated by active brain cells.

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CHAPTER 1Web Links

• Computed tomography (CT) provides three-dimensional images of the brain. Single pho- ton emission computed tomography (SPECT) permits identification of active brain regions by detecting the emission of single photons from an injected radioisotope.

• Positron emission tomography (PET) provides detailed information about active brain areas, due to the release of positrons by the injected radioisotope used in PET imaging.

• Functional magnetic resonance imaging (fMRI) permits measurement of blood flow through a brain region, which is an indicator of brain activity in that region.

• Microdialysis involves sampling brain chemicals in live, active subjects.

Biological Explanations of Behavior • Natural selection was one early biological explanation of behavior proposed by Charles

Darwin in the late 19th century. According to Darwin, specific traits selectively develop in individual species due to a process called natural selection, in which animals that survive to reproduce have traits that ensure survival and pass these traits on to their offspring.

• The American psychologist William James (1842–1910) introduced the concept of func- tionalism to explain behavior based on its selective advantage (that is, its survival benefit to a particular species).

• Other biological explanations of behavior focus on biological properties of an individual, including the individual’s genetic background, structural damage in the brain, or the role of various chemicals in the nervous system.

Questions for Thought

1. Name a behavior that might not be controlled by the brain. 2. Design a top-down study and a bottom-up study that would help us understand the rela-

tionship between handedness and verbal ability. 3. Under what circumstances should an investigator choose to use nonhuman participants

in a study? 4. What techniques might investigators use to study brain changes in Alzheimer’s disease? 5. What is topographical organization, and how was it discovered? 6. Who were the earliest proponents of localization and holism? 7. How are subcortical brain lesions produced? 8. What are the benefits and drawbacks of EEG, MEG, SPECT, PET, and fMRI?

Web Links

For more information on brain imaging and mapping, visit the Organization for Human Brain Mapping’s website. This professional organization provides numerous resources for learning about brain mapping techniques, the advantages and disadvantages of each, and safety tips when using certain imaging methods. http://www.brainmapping.org/

The American Psychological Association (APA) offers information on how to ethically and respon- sibly perform research, including the use and care of nonhuman subjects in laboratories. http://www.apa.org/

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CHAPTER 1Key Terms

Key Terms

ablation The removal of a part of the brain.

behavioral neuroscience A specialized branch of both neuroscience and psychology that involves bottom-up research strategies in which brain function is manipulated and the effect on behavior measured.

bottom-up research strategies Research strategies used by behavioral neuroscientists that begin by studying the basic levels of brain function in order to understand higher level functions like thought, attention, and emotion.

brain recording A method of studying the brain that enables investigators to pinpoint active brain regions.

brain stimulation A method of studying the brain that involves causing a part of the brain to become active.

cardiocentric explanations Heart-centered explanations of behavior that posited that the heart produces and regulates all behaviors, including thoughts and emotions; such expla- nations were popular in ancient civilizations of Western society.

cognitive neuroscience A specialized branch of both neuroscience and psychology that involves a top-down approach in which the highest levels of functioning, cognitive events like thinking or problem solving, are manipulated in order to observe the effect on neurons.

computed tomography (CT) A recording tech- nique that provides a three-dimensional image of the brain as a result of passing a series of X-rays through the head at various angles.

control In an experiment, the concept of control means all environmental and individual variables (such as room temperature, time of day, or medication level) are strictly con- trolled, and only the independent variables are allowed to vary.

correlational research Research that involves studying the relationship between two or more variables by measuring one or more vari- ables of interest without trying to control any of them; such research can inform us about the co-occurrence of variables.

craniotomy An incision in the skull.

electrode An insulated wire that is used to conduct electricity in brain lesioning or brain stimulation.

electroencephalography (EEG) A brain record- ing technique that measures the electrical activity of the brain.

encephalocentric explanations Brain- centered explanations of behavior that came about as a result of dissection studies of human and other animal cadavers in ancient Greece, which led to the discovery of nerves and nerve function.

event-related potential (ERP) A measured change in brain activity following the presenta- tion of a stimulus.

experiment A method of conducting research that involves measuring behavior while one or more variables are manipulated and all other variables are held constant or controlled.

functional magnetic resonance imaging (fMRI) A recording technique that is based on MRI technology and permits localization of accumulation of oxygenated hemoglobin in the brain, which indicates areas of increased brain activity.

functionalism A concept introduced by Ameri- can psychologist William James to explain behavior based on its selective advantage (that is, its survival benefit to a particular species).

holism A theory of how the brain divides its labors that holds that every area of the brain is equally capable of controlling all human functions.

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CHAPTER 1Key Terms

hypothesis A testable prediction about the relationship between two or more variables.

independent variable A variable that is manipulated in an experiment.

institutional animal care and use committee (IACUC) A committee composed of scientists and nonscientists that must give approval for all experiments with nonhuman subjects and is also responsible for regularly inspecting animal living quarters and other research areas.

lesioning Destroying or disrupting the func- tion of a specific brain structure.

localization A theory of how the brain divides its labors that holds that human functions are regulated by distinct, specific areas of the brain.

magnetoencephalography (MEG) A technique for studying the brain that enables investiga- tors to measure the magnetic fields generated by active brain cells.

microdialysis A technique for sampling chemi- cals in live, active subjects; it involves inserting a tube-shaped probe into the region of the brain under investigation and collecting brain fluid that is then chemically analyzed to deter- mine which substances are present.

microelectrodes Very tiny electrodes that can be inserted into individual neurons.

multidisciplinary An approach to studying the brain that involves contributions from several different fields or disciplines, including biolo- gists, chemists, physicists, anatomists, physi- ologists, psychologists, mathematicians, and engineers.

natural selection An early biological explana- tion of behavior proposed by Charles Darwin in the late 19th century; the theory holds that specific traits, including behavioral traits, selectively develop because animals that sur- vive to reproduce have those traits and pass them on to their offspring.

neuron A specialized cell that is the funda- mental unit of the nervous system.

neuroscience A multidisciplinary approach to studying the brain that involves many differ- ent fields or disciplines working together to conduct research into how the brain works.

nonexperimental research A research method that involves collecting data on particular vari- ables without controlling any of the variables.

phrenology A theory that lumps on the out- side surface of the brain correspond to human capacities and that a person’s psychic endow- ments can be measured by examination of the skull’s shape. Nineteenth-century Europeans used head shaping to encourage the devel- opment of qualities such as intelligence and moral character in their children.

physiological psychology Like behavioral neuroscience, physiological psychology uses a bottom-up approach to studying the brain and behavior. The term physiological psychology can be used interchangeably with the term behavioral neuroscience.

positron emission tomography (PET) A recording technique that is used to localize the source of positrons emitted from radioactive isotopes in the brain, which is associated with brain activity.

single photon emission computed tomogra- phy (SPECT) A recording technique that is an extension of the CT technique and is used to localize the highest concentrations of photon- emitting isotopes in the brain, which are associated with brain activity.

stereotaxic brain atlas A book that contains dozens of maps of the brain, each map repre- senting a slice through a particular region of the brain.

stereotaxic instrument An apparatus that allows investigators to locate subcortical brain structures with great precision.

subcortical Located below the cortex.

thermocautery A procedure for studying the brain that uses heat to cut away tissue.

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CHAPTER 1Key Terms

top-down research strategies Research strat- egies used by cognitive neuroscientists that involve studying high-level cognitive functions in order to draw conclusions about functions at the cellular levels.

topographical organization The precise map- ping of the body onto an area of the brain, showing that specific areas of the brain control certain parts of the body.

transcranial magnetic stimulation A nonin- vasive treatment for depression that involves directly stimulating neurons in the cerebral cortex.

variable In research, a quality or characteristic of an organism that varies and is not constant.

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