The Amazing Talking Magic Brain is an animated toy from Regency Toys (aka Regency Merchandise). While I'm not sure when this toy was released exactly, the box does mention "©1999". It requires three AA batteries.
The toy resembles a brain with a pair of gray eyes attached, standing on its spinal cord in a clear dome on a black circular base.
To play with it, you're supposed to ask a question and then press the blue button for an answer. The brain glows red, it talks, and it blinks its eyes as it talks. The pink button is supposed to turn the toy on or off.
While the toy has a feminine voice, there's another version of it called Houdini's Magic Brain which has a masculine voice. I don't know which version of the toy came first.