Brain Machine Interfaces Within a Critical Perspective

The possibility to substitute or extend the brain capabilities has always fascinated the scientific community and, currently, commercial and experimental efforts are proposing cutting-edge prototypal solutions. In a typical scenario, the brain is seen as a complex mechanistic machinery able to execute functions and to process information. These functions are virtually transferred to exogenous actors such as artificial devices that consider a variety of apparatuses variably applicable in complex neuropathological contexts. The applications can vary from functional substitution of lesioned brain regions, to dynamic supplementarity, to support "weakened" functions, to functional enhancement, or even (in a not far future) operative additionality of natural properties. However, the interface between the biological substrate and their artificial complement represents one of the most crucial elements in the plot. Indeed, these "junction points" reflect the most struggling limitations that, so far, have prevented from a full development in the field. On one hand, best brain-machine-interfaces (BMIs) are the result of a physical communication between the nervous system and the artificial device. Current available solutions are mostly invasive and include, for instance, subdural implanted microelectrode matrices or chronic macroelectrode stereotactic positioning into due brain targets. On the other hand, noninvasive BMIs, such as transcranical magnetic/current stimulations, propose surgical-free activations that however do not match the best requirements both for gross spatial resolution and because of the unreliable conveyed information. Invasive BMI, though partially supervening those problems, typically suffer, however, from other issues preventing their efficient long-term effectiveness. In fact, glial immunoreactions provoke, for instance, glial probe coatings degrading the electrodynamical features. In this review, we discuss the problems related to the diverse applications of BMI; a repertoire of recent cutting-edge insights in the BMI world will be analyzed, however, in a critical key throughout neurophysiological and neurobiological perspectives.