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Chapter 1


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Janelle Leboutillier

Chapter 1: Introducing Biological Psychology Biological Psychology as an Interdisciplinary Field  Biological psychology is the branch of psychology that studies the biological foundations of behavior, emotions, and mental processes  Relationship between biology and behavior is circular. Just as our biology can influences our behavior, so does our behavior influences our biology o High levels of testosterone are associated with increased aggression (biology driving behavior) o Watching a favorite sports team lose lowers testosterone levels (behavior drives biology) Historical Highlights in Biological Psychology  Archeological evidence of brain surgery suggests that many years ago people tried to cure others by drilling holes in the skull (trephining or trepanation) with the hope to release demons or relieve feelings of pressure  Edwin Smith Surgical Papyrus is the Egyptian text which is the oldest known medical writing in history o The Egyptians didn’t think the brain is important so they would remove it through the nostrils during mummification  The Greek scholars thought the brain as an organ of sensation o Hippocrates suggested that it was the source of intelligence o Aristotle believed the heart was the source of intellect whereas Herophilus (father of anatomy) believed that the ventricles played this important role of intellect  Galen believed that the ventricles played an important role in transmitting messages to and from the brain o Fluids flowing within the ventricles were believed to be continuous with fluids in the nerves. This persisted until the modern times  Galen got his ideas from Descartes who was impressed by the hydraulic statues and he used those to model for how the human body should work o Simple withdrawal reflex: when nerves sense heat or pain, they open pores in the brain and these pores release animal spirits that circulated through hollow tubes in the body. Reservoirs in the muscles would fill with these spirits causing the foot to pull away from the fire  Descartes is also notable for his support of the mind-body dualism o According to Descartes, the bodies of both humans and animals work mechanically o Descartes believed that humans had special capacities that they did not share with other animals and that these were contained in the mind o For Descartes, the mind was neither physical nor accessible to study through science  Modern sciences are based on monism rather than dualism o Monism perspective proposes that the mind is the result of activity in the brain which can be studied scientifically  The invention of microscopes (Leeuwenhoek) opened many doors for research  With better understanding of electricity (Benjamin Franklin), the Galen-Descartes notion of control through the movement of fluids was discarded  Galvani connected wires from a rooftop antenna to the legs of frogs and electrical disturbances in passing clouds would make the frogs twitch in unison  Franz Gall and Spurzheim proposed that he structure of an individual’s skull could be correlated with his or her individual personality characteristics and abilities o Phrenology  They also proposed a more modern view of the brain as the organ of the mind, composed of interconnected, cooperative yet relatively independent functional units  Paul Broca correlated the damage he observed in the patients with their behavior and concluded that language functions were localized in the brain  Fritsch and Hitzig described the results of electrically stimulating the cortex of a rabbit and a dog. By stimulating the motor cortex, they could produce movement on the opposite side of the body  Hughlings Jackson proposed that the nervous system was organized as a hierarchy with simpler processing carried out by lower levels and more sophisticated processing carried out by the higher levels such as the cerebral cortex Research Methods in Biological Psychology Histology  Histology is the study of microscopic structures and tissues  Histology allows to observe structure, organization and connections of individual cells  Leeuwenhoek was the first to investigate nerve tissue under a microscope  In order to view tissues under a microscope, they must be made into thin enough slices that allow light to pass through them  Because brain tissue is very watery and fragile, it is hard to preserve the thin slices so they fix the tissue by either freezing it or treating it with formalin (this hardens the tissue and preserves it from breakdown by enzymes or bacteria)  After fixation, it is sliced by a microtome which is like a miniature meat slicer and the fragile slices are mounted on to slides for viewing  The slice also needs to be stained in order to see the different structures o To make a structural analysis of single cells, Golgi silver stain is used o To identify cluster of cell bodies, the major bulk of the nerve cell, use a Nissl stain o To follow pathways carrying info from one part of the brain to another, use a myelin stain which would stain the insulating material that covers many nerve fibers (myelin sheath) o If you know where a pathway ends but want to know the origin, use horseradish peroxidase (when it is injected into the end of a nerve fiber, it travels backwards towards the cell body)  Once tissue is appropriately prepared it could be now viewed under a light or electron microscope  Electron microscopes use short, highly concentrated electron beams rather than light to form images. They can provide clear images of the synapse Autopsy  Autopsy means “to view oneself”  Autopsy has been replaced by modern imaging methods but it is still used  Autopsies must be interpreted carefully just like correlational methods  The differences in brain structure are correlated with sexual orientation, we cannot conclude on the basis of these data that brain structure either causes or is caused by sexual orientation Imaging  Computerized Tomography (CT) o Rontgen discovered X-rays o Normal x-rays don’t do a good job of imaging soft tissue o CT was invented by Hounsfield and Cormack o CT technology provides high resolution and the construction of highly detailed 3D images o Even though it provides structural information, it can’t distinguish between a living brain and a dead one (provides no info regarding activity levels in the brain)  Positron Emission Tomography (PET) o Allows us to observe the brain activity through a gamma camera which is used to detect radiation released by radioactive atoms that were decaying o PET combines with radioactive tracers with variety of molecules (oxygen, water and drugs) o Each gamma ray resulting from the breakdown of the tracer is recorded by detectors and fed into the computer by which the data are reconstructed into images o Programmers have assigned red and yellow to areas of high activity and green, black and blue to areas of low activity  Magnetic Resonance Imaging (MRI) o Standard medical diagnostic tool and a valuable research asset o Uses powerful magnets to align hydrogen atoms within a magnetic field. Radio frequency pulses are directed at the body producing resonance or “spinning” of the hydrogen atoms o When the radio frequency pulses cease, the atoms relax and the natural alignment of the hydrogen atoms return to original state o To construct the image, each small area of tissue is assigned a voxel (a 3D version of a pixel) and the darkness of each voxel represents the level of pulse activity in an area o fMRI is used to assess brain activity and it takes advantage of the fact that active neurons require more oxygen than less active neurons, and that variations in the blood flow will reflect this need o fMRI is used to track blood flow o Hemoglobin has different magnetic properties when it is combined with oxygen or not and so signals from a voxel will change depending on the oxygenation of the blood in that area known as the Blood Oxygenation Level Dependent (BOLD) effect o MRI technology has advantages over CT and PET. It can provide images taken at any angle without any movement of the individual o fMRI is superior in both spatial and temporal resolution to PET scans Recording  allows researcher to record the electrical and magnetic output from the brain and this electrical activity can be recorded using electrodes  The Electroencephalogram (EEG) o Berger was the first to conduct an EEG and noticed that the recordings varied during wakefulness, sleep, anesthesia, and epilepsy o EEG recordings measure the activity of large number of cells (field potential) o Several factors produce some distortion of the relationship between the actual activity of the brain and the recorded field potentials (electrodes are located on the surface of the scalp and the EEG is most highly influenced by the activity of cortical cells closest to the electrodes; cells in the deeper structures in the brain have little influence on the EEG; the bones and tissues separating the brain from the electrodes substantially reduce the signal reaching the electrodes) o Computerized EEG brain tomography can be used to generate maps of activity, making it possible to pinpoint the source of abnormal activity o EEG brain tomography can also be used to follow a patient through withdrawal from psychoactive drugs or during a coma and it can also aid in diagnosis of many disorders such as schizophrenia, dementias, epilepsy, and ADHD  Evoked Potentials o This technique allows researchers to correlate the activity of cortical sensory neurons recorded through scalp electrode with stimuli presented to the participant o The electrical activity to the response is quite small so the responses to many presentations of a stimulus are averaged (useful when a person’s behavior does not provide a clear indication of whether a particular stimulus had been perceived) o Ex. When spoken to by parents or others, a child with autism often shows no reaction at all. Through observations of evoked potentials to sound, we can determine whether the child can actually hear  Magnetoencephalography (MEG) o Allows researchers to record the brain’s magnetic activity o Active neurons put out tiny magnetic fields o Major advantage of recording magnetism rather than electrical activity from the brain relates to the interference of the skull bones and other tissues separating the brain from the electrodes (these tissues prevent a large amount of the brain’s electrical activity from being recorded using EEG o The skull bones and tissues allow magnetism to pass through without any reduction o Recordings of the magnetic fields produced by the brain can be taken much faster than either fMRI or PET scans o MEG is also silent as opposed to the loud hammering sound produced by the magnets used in MRI and it provides researchers with an important technique for studying brain responses to sound o MEG utilizes sensors known as superconducting quantum interference devices (SQUIDs) that convert magnetic energy into electrical impulses that can be recorded and analyzed o MEG doesn’t provide any anatomical data so researchers superimpose the recordings on 3D images obtained with MRI o Ex. MEG can allow researchers to localize cognitive functions such as language and also provide precise localization of the source of abnormal electrical activity that characterizes a seizure  Single-Cell Recording o Intra and extracellular events of a single neuron can be assessed using tiny electrodes that are surgically implanted o These electrodes can identify the occurrence of electr
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