The Lost Mind of Dr. Brain is the third installment of the educational Dr. Brain series, created and published by Sierra Entertainment.
As in the first two games, Lost Mind features science related puzzles. Where the previous installments featured a large, semi-free-roaming environment, however, Lost Mind confines the player to one single area (Dr. Brain's laboratory), with puzzles accessed from a central 'map' screen. Similarly, while the previous games' puzzles ranged across a variety of disciplines (both Castle and Island contained memory and word puzzles, as well as puzzles related to art and the sciences), Lost Mind focuses solely on the human brain, with puzzles related to spatial orientation, memorization, and symbolic association.
Due to the restricted game environment, much of the humor that was found in the first two games is missing in Lost Mind; since the player no longer has free rein over an entire island or castle, there is very little to explore, and very little with which to interact.
Between the second and third installments, several new characters have been introduced: Dr. Brain's niece, Elaina, is on hand to replace Dr. Brain as host, and also serves as a guide to Dr. Brain's mental pathways. Also, Rathbone, Dr. Brain's laboratory rat, provides what limited verbal humor can be found in the game.
- Train of Thought - A real-time path finding puzzle in which the player attempts to guide several (sometimes several dozen) colored balls along the tracks to their respective exit point. Rathbone resembles an Irishman in this puzzle.
- Synaptic Cleft - A real-time game of forces where objects enter from the left and must be guided to a small aperture on the right. Various attractive and repellent obstacles litter the center region. Rathbone has a heavy southern accent and resembles a cowboy in this puzzle.
- Neural Maze - A multi-dimensional maze in which the player must find a way from start to finish. The start and end points are usually on different levels, neither of which having paths leading all the way to the end. The player must often move up and down through dozens of levels several times before finally arriving at the destination. Rathbone has a heavy Brooklyn Accent and looks like a utility worker in this puzzle.
- File Sorting - A pure memory puzzle in which the player must store objects and then retrieve them at a later point. The higher levels involve swapping of compartments to further muddy the waters. Rathbone resembles Rod Serling with a similar theme from The Twilight Zone in this puzzle.
- Pentode - A real-time matching puzzle involving Greek letters, Roman numerals, ASL, or even periodic elements. Rathbone talks like a stereotypical Hollywood butler for a rich mansion, and you must listen to him to solve the Pentode puzzle.
- The Music Region - A puzzle primarily involving musical aptitude, particularly for reading musical score. A piece is played and the user must correct the score to match the desired musical sound. Rathbone resembles a gentleman similar to the musician Amadeus Mozart from the movie Amadeus and plays the harpsichord.
- 3D Construction - A puzzle of pure spacial orientation. The player must reconstruct the plans for a multi-layered, 3-dimensional object based only on visual inspection and manipulation of an original model. Rathbone has a Scandinavian accent in this game and wears a construction hat.
- Motor Programming - A primitive (non- complete) programming language similar to Logo in which the player must programmatically guide a mini-Dr Brain through a maze of obstacles while collecting a number of items. Rathbone is "Rathbot" in this puzzle, and talks and looks like a robot.
- Word Surge - Similar to the classic word-scramble game, but with slightly more complex possibilities. The strategies for solving the puzzles are similar to those required to solve a Rubic's Cube. Rathbone resembles a British gentleman from the 18th century in this puzzle.
- Dreamland - The final puzzle, requiring that the player beats the previous puzzles before being able to access it. Almost exactly like the Synaptic Cleft puzzle, except the mouse is attractive rather than repellent to the desired object. Rathbone is not present in this puzzle at all.