Frontal Intermittent Rhythmic Delta Activity (FIRDA) is a type of brain wave abnormality found in EEG located in the frontal portion of the brain. FIRDA is commonly associated with lesions, tumors, and encephalopathies among other reasons. FIRDA is a rather nonspecific EEG patter in comparison to its counterparts located in the occipital and temporal lobes.
Brigo, Francesco. Intermittent Rhythmic Delta Activity Patterns. ScienceDirect. https://www.sciencedirect.com/science/article/pii/S1525505010007262