> The tectum is a beautiful piece of engineering. To control the head and the eyes efficiently, it constructs something called an internal model, a feature well

> The tectum is a beautiful piece of engineering. To control the head and the eyes efficiently, it constructs something called an internal model, a feature well known to engineers. An internal model is a simulation that keeps track of whatever is being controlled and allows for predictions and planning. The tectum’s internal model is a set of information encoded in the complex pattern of activity of the neurons. That information simulates the current state of the eyes, head, and other major body parts, making predictions about how these body parts will move next and about the consequences of their movement. For example, if you move your eyes to the right, the visual world should shift across your retinas to the left in a predictable way. The tectum compares the predicted visual signals to the actual visual input, to make sure that your movements are going as planned. These computations are extraordinarily complex and yet well worth the extra energy for the benefit to movement control. In fish and amphibians, the tectum is the pinnacle of sophistication and the largest part of the brain. A frog has a pretty good simulation of itself. There is actually an immense amount of meditation on this very notion of an internal model, antecedent to the modern concept of consciousness we've been discussing since Kant, which guides a life form, from Aristotle down to St. Thomas Aquinas. See Daniel Heller-Roazen's "The Inner Touch: Archaeology of a Sensation"