視知覚と脳

Abstract

It has become well known that the brain is the centre of our mind (even if one may not accept it as the entire site of mind) and it is now essential for psychologists to take advantage of recent advances in brain imaging techniques. We often see images acquired by using magnetic resonance imaging (MRI) and functional MRI (fMRI) even in common media. It is, however, not always well-understood how fMRI works and what it can really tell us. In this article, I will review the basics of MRI and fMRI and discuss how they can actually help understanding the organisation and functions of our brain. In the domain of visual perception, retinotopy has been playing a major role in proving that fMRI is a useful neurophysiological tool. It has served to map out the structure of the cortical areas in humans, and provided the basis for further investigation of detailed visual functions. Retinotopy is only available in the visual cortex by definition, but a similar idea of tonotopy is used in the auditory domain and we might find other simple principles for other parts of the brain. I will then review our own studies on the 'Rotating Snakes' illusion, which induces an impressing sense of illusory motion in a stationary drawing. We have first demonstrated that MT+, the distinct area for visual motion processing, is activated by the illusory motion. Then we revealed the whole network from V1 to MT+ underlying the illusion by using fMRI adaptation. fMRI no longer represents simple localisation theories, as it was once criticised, but it is expected to help understanding how the brain works as a network. Technical improvement in both measurement and analysis is still on-going, and anyone who is interested in human brain and mind should keep an eye on its advancement even if they are not involved in conducting experiments by themselves.