Vision: A Window on Consciousness

Logothetis, N.K. (November 1999). Vision: A Window on Consciousness, Scientific American.

In this article, Nikos k. Logothetis, Director of the physiology of cognitive processes division at the Max Planck Institute in Germany, summarizes some recent research attempting to grope at the problem of consciousness.

What is consciousness? What are we actually conscious of? Is there a consciousness cortex? Or shy of that, are there certain pockets of neurons well correlated with subjective awareness? Neuroscience has grown increasingly concerned with these questions as it has grown increasingly more equipped to answer them. Logothetis scopes the article to a discussion of experiments related to visual awareness. As our visual processing is far and away the most adept sensory system, it is an important place to begin study.

Inspired by ambiguous stimuli (such as Necker Cubes and Salvador Dali paintings), which can be useful in experiments designed to reach consciousness, Logothetis describes how experiments involving binocular rivalry have show promising initial results. In binocular rivalry, the visual system is exposed to two “opposing” images, one in each eye, which can be difficult to resolve. To the conscious observer, these opposing images appear to alternate in consciousness, the mind becoming aware of one and then the other as the visual system selects one visual stimulus from one eye and then the other. This presents some interesting opportunities for examining the role of consciousness.

Using brain imaging and single cell recording techniques, the researchers reveal that neurons whose behavior reflects perception are distributed throughout the visual pathway. However, earlier stages of the visual pathway do not show behavior related directly to perception as often as later stages of the pathway which more reliably correlate with awareness. As an example, the inferior temporal cortex (ITC), long believed to be important for perceiving form and recognizing objects, appears to be a particularly active region when subjects report seeing faces.Technology has brought us to a place where tools exist in our toolbox for elucidating the mysteries of the mind. However, the sheer complexity of the human brain will ensure that isolating brain structures, pathways, and processes responsible for mediating consciousness will still be a daunting task for future researchers.