The Vision Thing and Brain Mapping

Knowledge about brain organization and development is rapidly evolving, partly due to new tools we have for research, such as various MRI techniques. One type of question being investigated is the degree to which brain organization is pre-programmed in the genes vs a result of the process of development.

Our current models of visual organization in the brain is that there are two streams of visual information: the ventral stream relates to object recognition (and lesions of which result in visual agnosia, or the inability to recognize objects), and the dorsal stream is for planning actions. Lesions of the dorsal stream result in what is called optic ataxia.

The dorsal stream of visual information is therefore related to seeing an object heading in your direction and getting out of the way, or to the act of catching a baseball. While the ventral stream will tell you that what you are catching is a baseball and not a rock.

However, the processing does not stop there and the ventral stream also separates living and non-living objects. The distinction is obviously vitally important to our survival. One recent piece of research looking at the brain activity of sighted people compared to those blind from birth shows that such categories are hard-wired into our visual cortex. In those blind from birth the visual input data is missing but the reaction algorithm still exists. The article doesn't explore whether this ventral stream is, in such cases, receiving inputs from other senses such as sound.

In our attempts to evolve into something more than irascible simians, it is worth knowing which of our reactions are due to hardware and which to software. But our brains are somewhat plastic so that the distinction is not as clear-cut as in silicon-based computers. We can be programmed, deprogrammed and reprogrammed, but some things are harder to change than others.

Have some ancient brain structures passed their usefulness? Or is our consciousness doomed to witness a mere fraction of what is really going on inside our minds?

full article at Neurologica blog.