second brain

second brain (plural second brains)

1. (anatomy, informal) The enteric nervous system.
   • 2018, Lee Holmes, Supercharge Your Gut: Supercharged Food‎^[1], Allen & Unwin, →ISBN:

     Although our ‘second brain’ doesn't make executive decisions like our actual brain, the two do communicate back and forth via electrical impulses through a pathway of nerves—the gut-brain axis—and this pathway influences our endocrine, immune and neural systems.

   • [2023 November 21, Yasemin Saplakoglu, “In the Gut’s ‘Second Brain,’ Key Agents of Health Emerge”, in Quanta Magazine‎^[2]:

     This network can function nearly independently from the brain; indeed, its complexity has earned it the nickname “the second brain.” And just like the brain, it’s made up of two kinds of nervous system cells: neurons and glia.]

2. (lifehacking, colloquial) The practice of unloading information to a digital storage, such as a notetaking application; the application and the associated data collectively.
   • 2022, Tiago Forte, Building a Second Brain: A Proven Method to Organise Your Digital Life and Unlock Your Creative Potential‎^[3], Profile Books, →ISBN:

     Camille is the cofounder and lead designer of a start-up in Quebec, Canada. She uses her Second Brain to save excerpts from the many research reports and studies she reads as part of her work designing electric vehicle charging stations for large residential buildings.

   • 2025 June 17, Joan Westenberg, “I Deleted My Second Brain”, in A newsletter about tech + philosophy‎^[4]:

     But over time, my second brain became a mausoleum. A dusty collection of old selves, old interests, old compulsions, piled on top of each other like geological strata. Instead of accelerating my thinking, it began to replace it. Instead of aiding memory, it froze my curiosity into static categories.

• second brain on Wikipedia.Wikipedia