The electro-encephalographic (EEG) brain activity was recorded in 13 healthy subjects via 128 scalp electrodes during a task assessing short-term memorisation of electrical nociceptive stimuli intensities. The EEG activity occurring during the memorising period was contrasted with that of a cognitive task of same difficulty, yet requiring no memorisation. Control tasks, audio or somatosensory, were conducted to determine the specific effects of nociceptive memorisation. Task performances were assessed and EEG signals were analysed as spectral composition and brain sources via topographical localisation reconstruction. Two consecutive periods of same duration were defined in the memorisation phase enabling analysis of the brain activity evolution during the encoding process. 
Whatever the sensory modality, alpha power increased focally during the memorisation phase compared to the cognitive task. Enhancement was stronger for somesthesic stimulations, and significantly so for the nociceptive modality which appeared as the hardest task. Alpha enhancement was distributed over the occipito-temporal scalp, and source reconstruction (LORETA) indicated sources in the bilateral occipital cuneus and gyri during the first period of memorisation, then in the right superior and middle temporal gyri during the second period. 
Alpha oscillations are considered to reflect inhibitory processes. Respectively, focal alpha enhancement may signal inhibition of task-irrelevant neuronal structures in visual occipital areas, along with process that directs the stream of information to structures representing encoding-relevant material. Since alpha power was correlated to task load and the type of attentional resources needed for its execution, our results suggest that this process may be critical for a correct information-storage.

ALPHA BAND POWER FOCAL CHANGES DURING THE SHORT-TERM MEMORISATION OF PAIN: A HIGH-DENSITY EEG STUDY WITH SOURCE LOCALISATION