Shining light into the black box of spinal locomotor networks

Abstract

Rhythmic activity is responsible for numerous essential motor functions including locomotion, breathing and chewing. In the case of locomotion, it has been realized for some time that the spinal cord contains sufficient circuitry to produce a sophisticated stepping pattern. However, the central pattern generator for locomotion in mammals has remained a 'black box' where inputs to the network were manipulated and the outputs interpreted. Over the last decade, new genetic approaches and techniques have been developed that provide ways to identify and manipulate the activity of classes of interneurons. The use of these techniques will be critically discussed and related to current models of network function.

Selection of Motor Programs for Suppressing Food Intake and Inducing Locomotion in the Drosophila Brain

“…Isolated spinal cord preparations have been used to demonstrate the existence of locomotive CPGs in the mammalian spinal cord [10],[11]. The neural networks comprising the motor programs and the motor neurons for the single limbs are located in the spinal cord, and the motor network of a limb can be divided into motor subprograms and sets of motor neurons for each joint of a limb.…”

Neuronal network analyses: premises, promises and uncertainties

“…This can only be dismissed if the heterogeneity was assumed to be of no functional importance, a view that is gradually being challenged (see below ;Soltesz 2006). Patrick Whelan (Whelan 2010) will discuss these issues further.…”

“…In addition to the significant insights into the principles of network operation that they have provided, these systems serve as a historical record of potential sources of error and limits to understanding that should inform current approaches and claims (these aspects are highlighted by Allen Selverston (Selverston 2010)). The issue will also examine the utility of certain experimental approaches (Astrid Prinz (Prinz 2010) and Smeal et al (2010) on theoretical and computational approaches; Patrick Whelan (Whelan 2010) on molecular approaches), and features that may extend the traditional criteria needed to understand networks (Vladimir Brezina , as an illustration of a network scheme based on assumption rather than direct characterization. For example, in this scheme the I cells are not defined; are they the large crossed caudal (CC) or small crossing inhibitory neurons (ScIN; Parker 2006a)?…”

Central Pattern Generators: Mechanisms of Operation and Their Role in Controlling Automatic Movements

“…The scale bar shows 10 sec. Modifi ed from [Whelan, 2010]. D) Relationship between refl ex reaction and phase of the locomotor cycle.…”

“…Recent studies using both physiological and embryological and molecular-genetic methods have made signifi cant progress in understanding the functional organization of the locomotor CPG in rodents [Gosgnach, 2011;Goulding, 2009;Whelan, 2010]. At least fi ve classes of interneuron involved in forming the locomotor CPG have been identifi ed in the ventral part of the spinal cord (V0, V1, V2, V3, and Hb9).…”