A hypothesis of local intrinsic cortical signal processing.

Nearly a century ago, Ramón y Cajal [1] speculated that cortical interneurones underlie specific functions that are fundamental to human thought. Here we develop a computational analysis of the function of local cortical loops and their synaptic connections. Specifically, we propose that the function of cortical interneurones is to reduce redundancy and to contribute to compute saliency of information represented in neurones by implementing divisive normalization and multiplicative filtering functions. This contextual filtering by cortical interneurones reduces the energy of locally homogeneous information flowing between different cortical areas, in a non-linear manner and along various event spaces, thereby ensuring a homeostatic level of informational selectivity. Dysregulations of the synaptic transmission in this ubiquitous basic building block of the functional architecture of the brain are correspondingly associated with disturbances of informational selectivity. Perturbations of synaptic transmission in local intrinsic connections of the cerebral cortex consequently lead to various kinds of cognitive and/or affective disorders, depending on the exact nature, the extension and the specific localization of the distortion.