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Katydid's Site Index
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| Type || Frequency (Hz) || Location || Normally || Pathologically
| Delta || up to 4 || frontally in adults, posteriorly in children; high amplitude waves || adults slow wave sleep
Has been found during some continuous attention tasks (Kirmizi-Alsan et al. 2006) || subcortical lesions
metabolic encephalopathy hydrocephalus
deep midline lesions
| Theta || 4 – 7 || Found in locations not related to task at hand || young children
drowsiness or arousal in older children and adults
Associated with inhibition of elicited responses (has been found to spike in situations where a person is actively trying to repress a response or action) (Kirmizi-Alsan et al. 2006). || focal subcortical lesions
deep midline disorders
some instances of hydrocephalus
| Alpha || 8 – 12 || posterior regions of head, both sides, higher in amplitude on dominant side. Central sites (c3-c4) at rest . || relaxed/reflecting
closing the eyes
Also associated with inhibition control, seemingly with the purpose of timing inhibitory activity in different locations across the brain (Klimesch, Sauseng, & Hanslmayr 2007; Coan & Allen 2008). || coma
| Beta || 12 – 30 || both sides, symmetrical distribution, most evident frontally; low amplitude waves || alert/working
active, busy or anxious thinking, active concentration || benzodiazepines
| Gamma || 30 – 100+ || Somatosensory cortex || Displays during cross-modal sensory processing (perception that combines two different senses, such as sound and sight) (Kisley & Cornwell 2006; Kanayama, Sato, & Ohira 2007; Nieuwenhuis, Yeung, & Cohen 2004)
Also is shown during short term memory matching of recognized objects, sounds, or tactile sensations (Herrmann, Frund, & Lenz 2009) || A decrease in gamma band activity may be associated with cognitive decline, especially when related the theta band; however, this has not been proven for use as a clinical diagnostic measurement yet (Moretti et al. 2009).
| Mu || 8 – 13 ||Sensorimotor cortex.|| Shows rest state motor neurons (Gastaut, 1952). || Mu suppression could be indicative for motor mirror neurons working, and deficits in Mu suppression, and thus in mirror neurons, might play a role in autism. (Oberman et al., 2005)