PSYC 211 - Chapter 5


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Experimental Ablation: The removal or destruction of a portion of the brain of a laboratory animal; presumably, the functions that can no longer be performed are the ones that region previously controlled. The oldest method used in neuroscience. Evaluating the behavioral effects of the brain damage Lesion : a wound or injury. o A researcher who destroys part of the brain refers to the damage as a brain lesion. o Lesion Study is a synonym for experimental ablation. o The rationale: the function of an area of the brain can be inferred from the behaviors that the animal can no longer perform after the damage. o We need to be careful in interpreting the effects of brain lesions. For example, when an animal bumps into objects, it can be due to deficits in motor coordination or blindness. Goals of lesion studies o To discover what functions are performed by different regions of the brain, and then to understand how these functions are combined to accomplish particular behaviors. o Circuits in the brain perform functions, not behaviors. No one region is solely responsible for a behavior; each region contributes to performance of the behavior. Ex) reading involves functions required for controlling eye movements, perceiving and recognizing words and letters, comprehending the meaning of the words, and so on. The interpretation of lesion studies is complicated as all regions of the brain are interconnected. For example, even though the damage to the structure X impairs a particular behavior, the behavior can be actually performed by neural circuits located elsewhere in the brain. (Damage to X may simply interfere with the normal operation of the neural circuits in Y) E.g. when the septum in the brain of a female rodent is damaged, the animal does not show any maternal behavior. It’s actually because the connection between the septum and the hippocampus controls the neural circuits located in the hippocampus, which is responsible for maternal behavior. So the septum itself is not involved in the mother’s spatial perception, but through its control over neural circuits in the hippocampus. Producing brain lesions Radiofrequency lesions o Parts of the brain immediately beneath the skull can be easily destroyed. But more often, we want to destroy regions located beneath the cortex. o Then small subcortical lesions are produced by passing a radiofrequency current through a stainless steel wire that is insulated except the tip. o The wire is guided stereotaxically o The passage of the current produces heat that kills cells. o The size and shape of the lesion is determined by the duration and intensity of the current o But this method can destroy everything in the vicinity. Excitotoxic lesions
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This note was uploaded on 02/13/2011 for the course PSYC 211 taught by Professor Yogitachudasama during the Winter '09 term at McGill.

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