INTENTION AS A COMPONENT OF THE ALPHA-RHYTHM RESPONSE TO MENTAL ACTIVITY

Many studies of alpha-rhythm reactivity conclude that alpha is selecti vely attenuated by attention accompanying mental activity. The topogra phy of this attenuation is assumed to match the relevant functional to pography of the cortex. But there are reports of apparent increased at tention resulting in no change, or even enhanced alpha - the paradoxic al response. It is proposed that in this case, alpha amplitude may be dependent on an intention component of behaviour. Some conflicting rep orts of alpha reactivity to mental processes may then be resolved. It is argued that the classical attention model of alpha is untenable, ex cept for simple sensori-motor responses. Reasons are given to support this and the concept of intention Bs a neuropsychological variable is introduced. Evidence is presented for a generalisation of an oculomoto r model of alpha activity proposed by Wertheim who demonstrated that a lpha reduces during attentive, but not during intentive visual behavio ur. The generalisation follows from reports of enhanced alpha in the f ew seconds prior to a skilled action in sport, and by neurophysiologic al evidence for a separate cortical organisation for perception and ac tion. Varying proportions of attention and intention then add a dimens ion to the factors influencing alpha blocking which may explain its in consistent response.