The hand and the brain

Abstract

Everyone involved in hand surgery and hand rehabilitation is well aware of the importance of well functioning hands for our patients' well being and life quality. A powerful pain free handgrip and well-coordinated precision movements of the fingers together with well-preserved sensory functions form a base for every individual's working capacity. Our hands are heavily involved in the interaction with other individuals in social life. Impaired hand function may have serious consequences for activities of daily living as well as subjective well being of our patients. The outer brain The philosopher Descartes named the hand the outer brain-a very clever expression for the close and intimate interaction between the hand and the brain. The hand is-like the brain-intelligent, it remembers, and it can improvise. The hand can be regarded an extension of the brain to the environment. Through the sense of touch our hands helps to explore and perceive the surrounding world. The hand is a symbol for identity and is intimately linked to our personality. The movements and gestures of our hands are important components of the body language, helping to express our feelings and being an important tool for communication with other individuals. The touch of a hand generates comfort and consolation. In fact, the pleasant feeling of well being which is generated by the touch of hands has recently been linked to a special system of small-sized nerve fibres-producing a faint sensation of pleasant touch. fMRI analysis during stimulation of these C tactile afferents in hairy skin showed activation of the insular region of the brain but not of somatosensory areas S1 and S2 (Olausson et al., 2002). The findings identify these C tactile afferents as a system for limbic touch that may underlie emotional, hormonal and affiliative responses to caress-like, skin-to-skin contact between individuals.