The study of cerebral magnetic activity is very promising for the understanding and care of diseases involving impaired cerebral activity such as epilepsy. One of the main hurdle in the recording of cerebral magnetic activity is that the intensity of cerebral magnetic fields is very weak. In this regard, we explore another potential way to appreciate the magnetic cerebral activity using superparamagnetic nanoparticles. These particles react to magnetic fields and can aggregate under their influence. Being superparamagnetic, they are also visible on magnetic resonance imaging (MRI). Superparamagnetic nanoparticles distributed in cerebral tissue could aggregate under the influence of local magnetic fields, with this aggregation being visible using MRI. In order to explore the feasibility of this new concept, we observed the behaviour of nanoparticles brought in proximity of living rat's brain slices of different levels of activity. A statistically significant aggregation of nanoparticles that is proportional to the rat's brain activity was observed in the study of 9 rats. These results favour the statement that brain electrical magnetic fields are sufficient to induce an aggregation of superparamagnetic nanoparticles in their vicinity. These results serve as a first "stepping stone" for the basis of a new method to appreciate brain magnetic activity using aggregation of nanoparticles as a marker of increased brain activity.