Abstract
The primary driver of the evolution of the vertebrate nervous system has been the necessity to move, along with the requirement of controlling the plethora of motor behavioural repertoires seen among the vast and diverse vertebrate species. Understanding the neural basis of motor control through the perspective of evolution, mandates thorough examinations of the nervous systems of species in critical phylogenetic positions. We present here, a broad review of studies on the neural motor infrastructure of the lamprey, a basal and ancient vertebrate, which enjoys a unique phylogenetic position as being an extant representative of the earliest group of vertebrates. From the central pattern generators in the spinal cord to the microcircuits of the pallial cortex, work on the lamprey brain over the years, has provided detailed insights into the basic organization (a bauplan) of the ancestral vertebrate brain, and narrates a compelling account of common ancestry of fundamental aspects of the neural bases for motion control, maintained through half a billion years of vertebrate evolution.This article is part of the theme issue ‘Systems neuroscience through the lens of evolutionary theory’.
Highlights
Among vertebrates, there is a gradual development of the movement repertoire from fishes and amphibians to that of birds and mammals
We will compare the nervous system of the lamprey with that of mammals, representing two phylogenetic extremes, to explore how much is common and what may have been modified from the point around 560 Ma, when the evolutionary line of lampreys became separate from that of mammals
The different neural networks underlying the execution of movement from the midbrain to the spinal cord in both the lamprey and mammals is shown in figure 1
Summary
There is a gradual development of the movement repertoire from fishes and amphibians to that of birds and mammals. The lamprey, belonging to the oldest group of living vertebrates, has only a limited set of motor behaviours such as locomotion, predation and feeding, while a cheetah, a balletdancer or a pianist have a varied and versatile movement repertoire. We will report that the basic neural organization is remarkably similar between these two groups, the number of neurons has increased markedly in practically all structures and so has the behavioural repertoire. We will first consider the neuronal networks underlying the actual execution of movements located mostly in the spinal cord, brainstem or midbrain—and the basic neural organization, ‘the motor infrastructure’, in the lamprey and in mammals (figure 1a,b). We will consider the forebrain (cortex, basal ganglia, thalamus, habenula) and its role in selection of action and decisionmaking and for recruiting the motor programmes needed at a particular point of time to meet intrinsic or environmental demands
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