Brain substrate
The brain substrate was a physical layer within the humanoid brain. 

During a mind transfer, the neural image of the brain substrates were scanned, mapped, and transferred to a new body. This procedure was done in 2399 by Doctors Altan Inigo Soong and Agnes Jurati, with help from Soji Asha, for the patient Jean-Luc Picard before his brain functions ceased. This neural image was placed within a golem. ()

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Brain anatomy