When delta is pathological, it represents cognitive impairment or of brain damage. Delta excesses often correlated with damage to the white matter (the white matter axons are exclusively excitatory). Focal&nbsp;delta activity should always be considered abnormal, possibly indicating a lesion, and should result in referral of the patient to a neurologist for further evaluation.&nbsp; Generalized background slowing indicates diffuse cerebral dysfunction, which, similar to focal slowing, is also not specific as to cause. Delta can indicate the effects of sedative centrally acting medications, neurodegenerative disorders, a widespread neurodevelopmental disorder, hydrocephalus, metabolic or toxic encephalopathy, CNS infectious disorders such as meningoencephalitis, traumatic brain injury, hypoxia, or anoxia. The delta band may be composed of delta rhythm activity (usually over 75 µV and rather rhythmic), slow cortical potentials (DC shifts) at .5 Hz and below, and also artifact (e.g., eye movement, glossokinetic artifact, electrodermal or sweat artifact).<br><br><img src="@@PLUGINFILE@@/focal-delta.png" alt="Focal Delta in a 12-year-old girl with complications from an anoxic head injury" width="635" height="547" class="img-responsive atto_image_button_middle"><br><p style="text-align: center;"><span style="font-size: 1rem;">Figure : Focal Delta in a 12-year-old girl with complications from an anoxic head injury</span></p><p style="text-align: center;"><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/focal-delta-z-scored.png" alt="Focal Delta in a 12 year old girl with complications from an anoxic head injury" width="623" height="389" class="img-responsive atto_image_button_middle"><br></p><p style="text-align: center;">Figure : Focal Delta in a 12 year old girl with complications from an anoxic head injury<br></p><p style="text-align: center;"><br></p><p style="text-align: left;">An excess of delta activity may be seen in the records of individuals with learning disabilities, Alzheimer’s disease, demyelination, toxic or metabolic disturbances, edema, and with aging there is frequently an increase of delta waves, especially in the left hemisphere.&nbsp; Pathological delta patterns, known as FIRDA (Frontal Intermittent Rhythmic Delta Activity) and OIRDA (Occipital Intermittent Rhythmic Delta Activity) are abnormal and pathological delta patterns. FIRDA is a transient, rhythmic slow wave pattern over the anterio EEG leads, that indicates cerebral lesions, circulation infarcts, stroke victims, and various metabolic disturbances.<br></p><p style="text-align: left;"><br></p><p style="text-align: left;"><img src="@@PLUGINFILE@@/firda-pattern.png" alt="FIRDA Pattern in an elderly woman with metabolic encephalopathy" width="627" height="461" class="img-responsive atto_image_button_middle"><br></p><p style="text-align: center;">Figure : FIRDA Pattern in an elderly woman with metabolic encephalopathy<br></p><p style="text-align: center;"><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/unhealthly-delta.png" alt="Unhealthy Delta" width="626" height="314" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center;"><br></p><p style="text-align: center;"><img src="@@PLUGINFILE@@/global-delta.png" alt="Global Delta in Head Injury, Deprivation of Oxygen for Prolonged Period of Time" width="627" height="357" class="img-responsive atto_image_button_text-bottom"><br></p><p style="text-align: center;">Figure : Global Delta in Head Injury, Deprivation of Oxygen for Prolonged Period of Time</p>