Negative Cognitions and PTSD: Using N400 and Reaction Time Measurements to Assess Semantic Expectancy Biases in Trauma Survivors

The goal of my project, performed for the completion of an honor’s thesis in psychology, is to use physiological measurements in order to address semantic (meaning) expectancy biases in civilian trauma survivors. With the... [ view full abstract ]

The goal of my project, performed for the completion of an honor’s thesis in psychology, is to use physiological measurements in order to address semantic (meaning) expectancy biases in civilian trauma survivors. With the help of my advisor, Professor Matthew Kimble, I have recruited participants from Addison County, both with and without a history of trauma, and run them through a simple lexical decision making task. During this task, participants are hooked up to an electroencephalogram (EEG), which measures superficial electrical activity on the surface of the scalp. During the lexical decision making task, participants are asked to identify if a word on their screen is a “real word” (ex. arms, legs, weapons) or a “nonsense word” (grilk, hyulf, fzq) by pressing a button on a response pad. I have used the EEG measurements to assess average N400 amplitudes in participants. The N400 is a negative going waveform that occurs between 350 and 600ms after stimulus onset and has been reliably proven to assess semantic expectancy violations - or what one might colloquially refer to as “surprise”. My hypothesis is that individuals with a history of trauma will yield smaller N400s (indicative of less “surprise”) and shorter reaction times to threatening words, and larger N400’s and slower reaction times to non-threatening words, which is indicative of a physiologically measurable semantic expectancy bias in survivors of trauma.