Date of Award

5-1-2016

Degree Name

Master of Arts

Department

Psychology

First Advisor

Hoane, Michael

Abstract

After sustaining a traumatic brain injury (TBI), a person’s ability to make daily decisions can be affected. Simple tasks such as, deciding what to wear are no longer effortless choices, but are instead difficult decisions. Incorporating behavioral assays that address decision-making skills after TBI can help a pharmacological treatment become easily translatable, as it is specifically assessing a certain aspect of cognitive functioning. Magnesium is a multimodal treatment that can decrease apoptosis, decrease breakdown of the blood brain barrier, and lessen brain edema after a TBI, which can affect the recovery of a patient. A discrimination task was used in conjunction with a magnesium treatment in order to examine how decision-making is affected after TBI and if the treatment helps to attenuate cognitive and motor deficits. Thirty-one male Sprague-Dawley rats (Harlan, Indianapolis, IN) were used and separated into MAG/TBI, VEH/TBI, or VEH/Sham groups. Before induction of a bilateral frontal injury, rats were shaped to learn to dig in the sand for a reinforcer and then pre-trained on the dig task. After surgery, rats received either an i.p. injection of 2 mmol/kg magnesium chloride or 0.1% phosphate buffer solution (PBS). Magnesium injections occurred 4 hours post-surgery, then at 24 hours and at 72 hours. Dig task testing began 7 days post-injury, lasting for 4 weeks. The discriminations included two scent pairings; basil (baited) versus coffee then the reversal and then cocoa (baited) versus cumin then the reversal. The locomotor placing task was conducted in order to assess for the recovery of motor function after TBI. Fear conditioning was also conducted to examine the role of extinction after TBI. The results indicated that the magnesium treatment was successful at attenuating cognitive and motor deficits after TBI. The results also indicated that the dig task is a sufficient operant conditioning task in the assessment of frontal functioning after TBI. The fear conditioning procedures, however, failed to produce significant results. Discrimination testing and a magnesium treatment both have the potential to positively impact the millions of people suffering from a TBI.

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