Unlike previous "Switched-On" releases, which compiled each of the band's eras in chronological order, Pulse of the Early Brain covers rarities from all over their career.

Pulse of the Early Brain received universal acclaim from music critics, who praised the inclusion of Simple Headphone Mind and Low Fi, but some also consider it to be the most and least essential release in Stereolab's catalogue.

It marks the first appearances of members Mary Hansen and Andy Ramsay and contains "blissfully loud and transporting rock" that has a variations of "a hypnotic whir that seems unencumbered by the rules of gravity: the analog rumble, synth squiggles, and strummed chords are a collective force onto itself.

[2] It was intended for a sculpture in 2000 by Charles Long, but the track "Unity Purity Official" with its "percolating rhythms, retro-futurisms, and ye-ye melodies" was chosen instead.

[2][3] "Blaue Milch" is a "reimagining of a Peter Thomas Sound Orchestra piece" released under Bungalow Records in 1998.

[16] Critics considered the inclusion of the EPs Simple Headphone Mind and Low Fi to be highlights of the compilation.

[2][4] Stephen Thomas Erlewine commented: "Oozing with ambient grooves and catchy harmonies, the fifth volume of rarities from the avant-pop quintet calls back to their space-age prime.

[1][4][5] Robert Ham of Pitchfork questioned the inclusion of short tracks and felt that the EP Simple Headphone Mind were "skeletal and unfinished.