Dr. David Berson

What you have to imagine is starting in the spinal cord and working your way up into this big, magnificent brain.

And what you would do as you enter the skull is get into a little place where the spinal cord kind of thickens out.

It still has that sort of long, skinny, trunk-like feeling.

Right.

It starts to spread out a little bit.

And that's because your evolution has packed more interesting goodies in there for processing information and generating movement.

So this midbrain you're talking about is the last bit of this enlarged sort of spinal cordy thing in your skull, which is really the brainstem is what we call it.

The last bit of that before you get to this relay up to the cortex is the midbrain.

And there's a really important visual center there.

It's called the superior colliculus, but this is where most of the action is in terms of interpreting visual input and organizing behavior around that.

You can sort of think about this region of the brainstem as a reflex center that can reorient the animal's gaze or body, or maybe even attention to particular regions of space

out there around the animal and that could be all for all kinds of reasons i mean it might be a predator just showed up in one corner of the forest and you pick that up and you're trying to avoid it or just any movement many movement right it might be you know that suddenly uh you know something splats on the page when you're reading a novel and and your eye

reflexly looks at it you don't have to think about that that's a reflex but these are centers that emerged early in the evolution of brains like ours to handle complicated visual events that have significance for the animal in terms of space where is it in space and in fact this same center actually gets input from all kinds of other sensory systems that take information from the external world from particular locations

and where you might want to either avoid or approach things according to their significance to you.

So you get input from the touch system.

You get input from the auditory system.

I worked for a while in rattlesnakes.

They get input from a part of their warm sensors on their face.

They're in these little pits.

They have a version of an extra receptive sensory system.