Slow cortical potentials: Plasticity, operant control, and behavioral effects

Slow cortical potentials are negative or positive polarizations of the electroencephalogram (EEG) or magnetic field changes in the magnetoencephalogram (MEG) that last from 300 ms to several seconds. They originate in depolarizations of the apical dendritic tree in the upper cortical layers that are caused by synchronous firing, mainly from thalamocortical afferents. Functionally they constitute a threshold regulation mechanism for local excitatory mobilization (negative slow potentials) or inhibition (positive slow potentials) of cortical networks. Humans can learn to voluntarily regulate these potentials after operant training using immediate feedback and positive reinforcement for self-generated slow potentials shifts. After learned self-regulation of negative slow cortical potentials, motor and cognitive performance of various tasks improves, depending upon the specific cortical location of the learned response. Learned reduction of cortical negativity increases seizure threshold and improves drug-resistant epilepsies. The learned self-regulation of slow cortical potentials is based on a redistribution of attentional resources and depends critically on a prefrontal and thalamic attention system. Finally, a thought translation device uses the slow potential self-regulation skill in totally paralyzed locked-in patients for communication with a language-shaping computer system.