This functional dependence of {HEAD ~ η} allows the learning rate to change adaptively with {TAIL ~ the error} E 
This functional dependence of { HEAD ~ η } allows the learning rate to change adaptively with { TAIL ~ the error } E
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH