Brain Dive: 1st GIG/"SUPER SPARTAN"
During Section 9's brain dive/briefing, various scenes from the first season (or 1st GIG) are displayed including the raid on the Chinese restaurant at the beginning of "¥€$" and Section 9's apprehension of Ernest Serano at the STARCHILD COFFEE HOUSE at the end of "EQUINOX".
A brain dive is a quicker way of passing around information. Comparable to the Tachikoma's sychronizations, a brain dive will allow for information to pass between hosts much faster than explaining it through words.
A brain dive into Motoko by her section members is first mentioned in chapter 2, "SUPER SPARTAN", from the 1991 Ghost in the Shell manga by Shirō Masamune.
Batou's comment to the other section members about having their back-hacks up is to warn his teammates not to get to close to Motoko's ghost line. In the manga, a few of the members, including Batou, dive a bit too close to Motoko's ghost and she orders them out else they want to be, "brain-burned."