Readiness For Action
by Lüder Deecke and Wilfried Lang University Clinic of Neurology, Währinger Gürtel 18-20, A-1090 Vienna, Austria
Readiness for action is expressed in the brain by means of a slow negative DC-potential which is a preparatory facilitation process (synaptic drive) over certain cortical areas that will be involved in the intended volitional act. This 'volition-related potential' has been termed Bereitschaftspotential (BP) or readiness potential ( Kornhuber & Deecke 1964, 1965). The importance of the availability of the BP is the possibility of making philosophical values such as volition or will accessible to neurophysiological experimentation. As an important result of such research, we postulated from our studies that the supplementary motor area (SMA) participates in the preparation of willful, self- initiated action ( Deecke & Kornhuber, 1978). By now this postulate that a certain brain potential is generated in a certain brain area has long been confirmed. The BP or more precisely its early component BPI was found to be generated by the SMA. Our notion of two components of the BP, the bilaterally-symmetrical BP1 (1.5 to 0.5 sec prior to the onset of voluntary action) and the asymmetrical, i.e. contralaterally dominant BP2 (0,5 to 0 sec prior to movement onset) was as well confirmed by other groups. Our 1978 publication appeared in the same year as Lassen, Ingvar & Skinhoj ( 1978), who found that not only the primary motor area (NU) but also SMA showed increased rCBF (regional cerebral blood flow) in conjunction with hand movements. With the rCBF method - the subjects are continuously making movements (similar as with the emission CTs or FMRI) - one cannot distinguish whether the SMA is activated before, during or after the movement. The BP, being an entirely pre-movement phenomenon proofs that the SMA activation starts already prior to the onset of voluntary action. The BP amplitude is a function of psychological values such as level of motivation, strength if imagination, intentional engagement, directed attention, inertial as well as emotional load, proactive interference, etc. Using magnetoencephalography (MEG), 3 principal generators of the Bereitschaftsfeld (BF) or readiness field (RF) preceding unilateral movement can be distinguished: (1) the supplementary motor area (SMA) for BF1, (2) the contralateral motor cortex (MI) for BF2 and (3) the ipsilateral MI ( Lang, Cheyne, Kristeva, Beisteiner, Lindinger & Deecke 1991). According to recent evidence the cingulate motor area (CMA) may also be involved in BPI generation. Philosophy of volition had some tradition in the past, at present will is not particularly 'in'. It is hoped that experimental access by natural sciences tools may change the present neglect. Present day philosophy mostly deals with 'retrorolandic matters' (perception, cognition, etc.) but it is important to focus more interest on 'prerolandic' matters, such as motor, motivation, volition, will, planning, providence, precaution, emotionally-engaged anticipation of action, cortically monitored vs. automatic (subconscious) actions, etc.