Now Martin Wiesmann and colleagues have shown that another complicating issue, even in the complete pitch dark, is whether participants have their eyes open or shut.
They found that when participants closed their eyes in the dark, brain areas related to vision, touch, hearing, balance, smell and taste were all activated relative to when they lay in the dark with their eyes open. By contrast, lying in the dark with their eyes open, activated participants’ brain areas related to attention and eye movement.
The researchers said the findings point to the there being two kinds of mental activity: “…with the eyes closed, an ‘interoceptive’ state characterised by imagination and multisensory activity, in contrast to an ‘exteroceptive’ state, with the eyes open, characterised by attention and oculomotor activity”.
“It therefore seems critical that subjects do not change the state of their eyes during an experiment”, they added.
Wiesmann and his colleagues said more research was needed to test whether the increased sensory activity observed in the brain when someone closes their eyes in the dark is also accompanied by an enhancement of their sensory acuity.
Wiesmann, M., Kopietz, R., Albrecht, J., Linn, J., Reime, U., Kara, E., Pollatos, O., Sakar, V., Anzinger, A., Fest, G., Bruckmann, H., Kobal, G. & Stephan, T. (2006). Eye closure in darkness animates olfactory and gustatory cortical areas. NeuroImage, 32, 293-300.
Link to critique of functional brain imaging by Paul Bloom, writing in Seed Magazine. Open access.
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