This study proposes a new methodology to diagnosis posttraumatic stress disorder (PTSD) utilizing electroencephalography (EEG) and focusing on the right temporoparietal junction (rTPJ) and parietal lobe. This is the first quantitative neurological methodology in existence for this type of diagnosis. The new model was tested on an African American heterosexual female utilizing two different breathing tasks and one heartbeat detection task. During the heartbeat detection task, low-mid range beta wave activity was almost non-existent for the rTPJ and the parietal lobe at 22 Hz. The parietal lobe’s absolute power is unusually low for the right side and shows to not be active. This data supports the idea that during a task that requires concentration a participant with PTSD is unable to focus, which can be used to quantitatively diagnose PTSD for the first time ever.