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Found on QuantifiedSelf :

Our guts can be monitored much like our brains thanks to the number of nerve endings which produce electrical signals. The technology that allows for this is called (EGG) electrogastrogram.

PubMed Abstract:

Despite its simplicity and noninvasiveness, the use of the electrogastrogram (EGG) remains limited in clinical practice for assessing gastric disorders. Recent studies have characterized the occurrence of spatial gastric myoelectric abnormalities that are ignored by typical approaches relying on time-frequency analysis of single channels.

Read More @ PubMed

Wikipedia for EGG:

Slow wave frequency varies in the different organs of the GI tract and is characteristic for that organ. They set the maximum frequency at which the muscle can contract:

• stomach – about 3 waves in a minute,
• duodenum – about 12 waves in a minute,
• jejunum – about 11 waves in a minute.^[3]
• ileum – about 8 waves in a minute,
• rectum – about 17 waves in a minute.^[4]