Where is the ‘Jennifer Aniston neuron’?

Abstract

It is generally believed that spike timing features (firing rate, ISI) are the main characteristics that can be related to neural code. Contrary to this common belief, spike directivity, a new measure that quantifies transient charge density dynamics within action potentials (APs) provides better results in discriminating different categories of visual object recognition. Specifically, intracranial recordings from medial temporal lobe (MTL) of epileptic patients have been analyzed using firing rate, interspike intervals and spike directivity. A comparative statistical analysis of the same spikes from four selected neurons shows that electrical micro-mapped features in neurons display higher separability to input images compared to spike timing features. If the observation vector include data from all 4 neurons then the comparative analysis shows a highly significant separation between categories for spike directivity (p=0.0023) and does not display separability for ISI (p=0.3768) and firing rate (p=0.5492). The presence of electrical micro-maps within APs suggests the existence of an intrinsic “neural code" where information regarding input images is electrically written/coded and read/decoded during AP propagation in the neuron. The occurrence of electrical micro-maps within APs reflects information communication and computation in analyzed neuron within a millisecond-level time domain of AP occurrence. This existence of a “lower level” of coding where information is processed within neurons raises questions regarding the richness and reliability of models that constrain neural code to spike timing features. Additionally, this phenomenon that occurs within APs may provide a step forward in understanding the fundamental gap between molecular description, information processing and neuronal function. Importantly, this paper confirms a new paradigm regarding neural code where information processing, computation and memory formation in the brain can be explained in terms of dynamics and interaction of electric charges.