Neuronal network analyses: premises, promises and uncertainties

Abstract

Neuronal networks assemble the cellular components needed for sensory, motor and cognitive functions. Any rational intervention in the nervous system will thus require an understanding of network function. Obtaining this understanding is widely considered to be one of the major tasks facing neuroscience today. Network analyses have been performed for some years in relatively simple systems. In addition to the direct insights these systems have provided, they also illustrate some of the difficulties of understanding network function. Nevertheless, in more complex systems (including human), claims are made that the cellular bases of behaviour are, or will shortly be, understood. While the discussion is necessarily limited, this issue will examine these claims and highlight some traditional and novel aspects of network analyses and their difficulties. This introduction discusses the criteria that need to be satisfied for network understanding, and how they relate to traditional and novel approaches being applied to addressing network function.

Anatomical recovery of the spinal glutamatergic system following a complete spinal cord injury in lampreys

“…Our study provides an accessible model system to decipher the molecular mechanisms underlying glutamatergic spinal circuit remodelling and regeneration and how these processes could be optimized for therapeutic interventions in mammals. Further, this work stresses the importance of studying the changes above the injury and not only below, as suggested before by other authors47 and also the necessity of increasing our understanding of the spinal circuits not only in lesioned but also in un-lesioned animals4849.…”

Dynamic systems approaches and levels of analysis in the nervous system

“…Similar considerations apply to interactions between regions of the nervous system (e.g., Bullmore and Sporns, 2009), where each region is actually a neuronal network but can be treated as a component. Assume, following traditional neurobiological criteria, that understanding implies the ability to explain the spatial and temporal aspects of the networks activity in terms of the activity of its cellular and synaptic components (see Selverston, 1980; Yuste, 2008; Parker, 2010). The fundamental first step according to these criteria is to identify the network neurons: while this seems trivial, even this initial step can be difficult as network neuron identification criteria can introduce errors of inclusion or exclusion (see Parker, 2010), and non-neuronal elements (glia) may also contribute to network function (Araque and Navarrete, 2010).…”

“…The major problem is linking across levels in the nervous system, for example, in the way that NAD and other enzymes are linked as functional components of the Kreb's cycle, which is in turn linked as a component of metabolism. Where strong claims to these mechanistic links have been made in the nervous system they are either demonstrably in error or underdetermined by the data and reflect the belief that the level of explanation given is sufficient (see Dudai, 2004; Parker, 2006, 2010). …”

Shining light into the black box of spinal locomotor networks

“…On the other hand, the initial flurry of studies while technically outstanding have not yet provided a conceptual advance that have leapfrogged us beyond that articulated by Graham-Brown. Most probably, this is because networks, no matter where they are located, are difficult to understand (Parker 2010;Selverston 2010). To fully appreciate their operation, a multi-pronged approach combining behavioural, genetic, modelling, intracellular and imaging techniques needs to be applied.…”