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Chapter 3


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Ted Petit

University of Toronto 1 PSYB65: Human Brain and Behavior Sayanutha Niranjan Chapter 3 Techniques in Neuropsychology: Investigating How the Brain produces Behavior in Humans Study of the Damaged Nervous System The Scientific Method: has at its roots in the principles of objectivity and replication or confirmation of results Empirical Method = level of objectivity  “observation” Replication: when neuropsychologists try to replicate their results to prove their findings were not a fluke. Control: the ability to manipulate something to determine the effects and cut out extremes and confounding variables that may cause a researcher to make false conclusions.  Refers to having an appropriate comparison sample so that deviations from this sample can be observed Hypothesis  prediction that may be formed as a statement that can be rejected Independent variable: variables that researcher manipulates to determine how the behavior is affected Dependent variable: response or behavior that the experimenter measures Converging Operations: allows conclusions to be made based on different ways that a hypothesis is tested. Nonhuman Animal Models Non-Human Research: Raising non-human subjects in controlled conditions allows for less variability between subjects that is not available in human subjects.  Limitations of this are that if the animal performs the task incorrectly would you attribute it to learning or lack of interaction with the stimulus?  Also, the conclusions may not be generalizable to other species, especially humans which have much more complex nervous systems.  Non human animals are not sufficiently behaviorally sophisticated to be useful in understanding the principles of human behavior  Humans have a complex CNS unique too humans, language & memory Neuropsychological Celebrity: Phineas Gage  25 year old railway construction foreman  Expanding railway – drilling holes, putting in an explosive powder, inserting a fuse and covering the powder with sand  Phineas accidently prematurely ignited the charge  Explosion projected 4-foot long taming rod through his left cheek, penetrating the base of his skull and exiting through top of his head  He didn’t’ even lose consciousness – spoke few mins later  Personality has changed dramatically  “NEW PERSONALITY”  Focal brain damage can alter one’s personality 1 University of Toronto 2 PSYB65: Human Brain and Behavior Sayanutha Niranjan Delayed Nonmatching to Sample task  Tasks involves a food reward and a food-deprived nonhuman animal  Animal observes the food reward paired with stimulus A; then the animal is required to pick the novel stimulus B to receive the reward o Researcher discovered many important principles involved in learning and memory by using such tasks o Unclear if animals ever exhibit this type of behavior in naturalistic settings Cognitive Testing - Mini-mental state exam looks at how people can answer a series of questions, which are designed briefly to examine cognitive functions such as language, orientation, attention and orientation to time - Get a gross degree to which nervous system functions are involved in any injury Cognitive Testing: these are given to participants in the same way and scored in the same way so that they are standardized.  They are usually general and if something wrong is detected the test is more specific, used to help with diagnosis and rehab.  Some limitations occur with this testing since there is a lot of variation in the population ex. A person with a disability will produce an invalid intelligence test score. Brain Imaging Functional neuroimaging provides the researcher with in vivo (live) pictures of the brain areas that are most active during a cognitive task Structural Imaging: a test that provides an image of the brain structure, which helps clinicians find the location of an injury or abnormality. X-Rays (Neuroradiology):  Discovered when a scientist noticed a glowing fluorescent screen on a table when studying cathode rays.  It was discovered that the rays could penetrate the tube they were contained in.  X-rays – more dense the material, the less penetrable the substance is to x-rays  However X-rays cannot pass through all objects, which are why it passes through soft tissues or bone cracks, but not dense bone or foreign objects.  The X-rays that pass through are able to hit a photographic plate.  Since X-rays are radiation too much can be harmful, but it can be used to kill cancer growths.  Very dense structures (such as bone) appear bright and lower-density structures (crack in a bone) appear dark  Provide a 2-D representation of density  These cannot provide information on pathologies inside the skull since the brain is soft tissue. o Not proved to be very useful for neuroimaging b/c brain is soft tissue encased in bone 2 University of Toronto 3 PSYB65: Human Brain and Behavior Sayanutha Niranjan o Doesn’t give info on what occurred inside the skull o Relatively inexpensive and are fast way to get good structural info about the integrity of the skull, their ability to image the structures within the skull is limited Computed Axial Tomography (CAT/CT scans):  Give a non-invasive view of the brain involving computing and x-rays.  It involves sending X-rays into the body at different angles then computed into a 3-D image and brain slices where dense areas are bright and the rest is dark.  The problem is it cannot differentiate between white and grey matter.  The axial version scans in one plane images constructed in one plane  Now CT images can often be constructed in two or other planes as well  Coronal plane shows slices perpendicular to the horizon, taken along the superior-inferior axis  Sagittal plane perpendicular to the horizon, but taken along the dorsal-ventral axis  Painless takes relatively little time – performed on an unconscious individual  These scans help identify abnormalities in the brain shown by changes in density on the scan (except for tumors similar in density to normal cells) so they could be related to behavioral defects. Magnetic Resonance Imaging (MRI): - Noble prize-winning research of Felix Bloch and Edward Purcell - Produced an image using nuclear magnetic precision measurement, similar to CT scans, however they have better resolution. - Initially called “nuclear magnetic resonance imaging” but term nuclear was dropped from name b/c many people find references to radiation unsettling o Since hydrogen is a common element in the body with poles facing random directions, this scan places a strong magnetic field near the brain so the atoms poles become aligned and polarized. o Once aligned, atoms can be perturbed in a uniform direction through the application of a radio frequency pulse o The machine measures the relaxation time, which follows the pulse, which is the time taken by the atoms to return to their normal, random state o The receiver coil (measures intensity) and gradient field produce the 3- D image. o Measured longitudinally (T1) and horizontally (T2), or time it takes for the atoms to return to their normal positions therefore measures H density. o The T1 image shows brain, bone, air and water as dark and the T2 shows a dark image with fluid as bright. o MRIs contain extremely strong magnets- magnetic strength can be measured in units of Tesla (T) o The limitations are that any internal metal in the body will be attracted to the magnet, which is a dangerous in
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