This is my first pixel art. I made it for a bigger project which I'm planing.
Please be nice :)
I like it as well. My only comment is that it looks a bit more like a cloud than a brain because the general shape is off. But I study neuroscience, so I'm a bit biased. Here's an example of stripped down model of a human brain: http://www.joelertola.com/tutorials/brain/gifs/Brain.gif
Your colors remind me a bit of this image: http://www.zeitnews.org/images/stories/brain-763982-1.jpg.
I like that you refined the shape and lines very well.
But it of course lacks volume = shading.
The shading tones you used do no good, since they are almost invisible.
Actually I like it. Shadows and lights are made well and simple colouring is nice.