Moving The Mind’s Eyes

Advances in neurobiological research often demonstrate how very difficult it is for us to get a good look at ourselves. Effective analytic tools in the sciences usually rely on defined categories such as organic and inorganic; animals and plants; protons, neutrons and electrons; voluntary action versus involuntary action; motor skills versus thinking skills. But refinements in our analytic efforts often require redefining the very categories they have created. The famous particle/wave duality of light is a perfect example.

A recent article about a particular brain structure contributed to my fascination with how thought-governed lives emerge from the basic aspects of our biology that we share with so many creatures. The article is called Seeing Without Looking: Brain Structure Crucial for Moving the Mind’s Spotlight. It summarizes findings reported in a December issue of Nature. It considers the relationship between looking at something with your eyes and paying attention to something with, for lack of a better word, your mind.

The brain structure in question is called the superior colliculus. Its function has been understood to be the motor control of head and eye movement, i.e. sending motor control commands to eye and neck muscles. But experiments at the Salk Institute for Biological Studies indicate that the superior colliculus is equally involved when you move your attention away from the thing you may be looking at. And the institute, it seems, has been paying attention to the superior colliculus for some time. Another study was reported on in September 2008.

This one observed what happens when we track what researchers called “the invisible center” of a moving object. The invisible center of something is like an airplane whose presence at night can only inferred from peripheral lights, say on its wings. Since the superior colliculus contains a topographic map of the visual space around us, it mirrors geographic space, and it is possible to identify neurons that correspond to the spot in this space where our eyes would focus (named the foveal location). The studies confirmed that neurons in the foveal location are active even when the object of their attention was invisible, like the dark airplane. The eyes seem to be pointing to the invisible part of the image.

In February 2009, researchers at Salk also found that the superior colliculus controls microsaccades, those quick tiny eye-movements necessary to keep visual images from fading and that appear to be random.   But according to Richard Krauzlis, an associate professor in the Salk laboratory “…results show that the neural circuit for generating microsaccades is essentially the same as that for voluntary eye movements. This implies that they are caused by the minute fluctuations in how the brain represents where you want to look.” (emphasis mine). It was demonstrated that even if we avert our eyes away from an object that gets our attention, the direction of microsaccades will be biased toward that object.

These observations suggest an interesting link between our eyes and the more general action of just paying attention to something and thus also indicate some overlap of reflexive (automatic) action and thoughtful (deliberative) behavior. Voluntary and involuntary movements share neurons. It was also noted in the December 2009 article, (again quoting Richard Krauzlis) “… results show that deciding what to attend to and what to ignore is not just accomplished with the neocortex and thalamus, but also depends on phylogenetically older structures in the brainstem.”

When a brain structure that seems built to move eye and neck muscles is also found active in moving our attention, purely mindful attention becomes linked to sight. That the eyes will lock on an invisible object suggests that something of the visual brain will respond to internal stimuli. And finding that neural circuits for what appear to be reflexive eye movement, namely microsaccades, are essentially the same as the ones for voluntary movement, suggests that distinguishing between voluntary and involuntary is not so easy given that microsaccades happen completely outside of our awareness.

Each of these studies focusses on a detail that would seem to have no affect on how we see ourselves. But they contribute to the steady progress neuruoscientists are making as they try to unravel what the brain is doing. This unraveling often leads to novel considerations like Semir Zeki’s idea that the visual arts are an extension of the function of the visual brain (August 2009 post).

The body is built to be in its world, to see it and move through it and use it. Our elaborate conceptual structures built with language, reason, mathematics and all of our scientific efforts are inevitably grounded in fundamental biological actions and may be motivated by more than our awareness can discern. It is entirely reasonable to consider that we can never fully understand what we’re doing or why.

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