Seminario de Investigación: The vertebrate forebrain conserved from lamprey to mammals: ion channels, transmitters and connectivity.

Sten Grillner, Karolinska Institute, Estocolmo, Suecia

Resumen: The vertebrate forebrain conserved from lamprey to mammals. Ion channels, transmitters and connectivity. The lamprey diverged from the vertebrate line of evolution leading up to mammals 560 million years ago. What is common in the organization of the nervous system of lamprey and mammals must have been present already very early in vertebrate evolution. We have previously shown that the basic organization of the brainstem spinal cord is conserved and also the midbrain control of eye and orienting movements. Recently we have shown in a series of studies that the detailed organization of the basal ganglia and related habenula complex is conserved with regard to transmitters, neuropeptides, expression of ion channel subtypes, neuronal activity pattern and connectivity. We now show that also the organization of pallium (corresponding to cortex) is similar in that we have specific projection neurons to the tectum/superior colliculus, the midbrain tegmentum and to reticulospinal neurons in the hindbrain. Moreover, stimulation of the pallial region can elicit eye, orienting, locomotor and oral movements. These movements are elicited by monosynaptic connectivity to the different motor centres. There is also a retinotopic visual area and a somatosensory area in lamprey cortex, which is three-layered with 22% GABA interneurons and 78% glutamatergic neurons. In conclusion, the basic features of the vertebrate forebrain existed already at the dawn of vertebrate evolution.

Bio: Sten Grillner is professor at the Karolinska institute in Stockholm with research focused on the cellular bases of motor behaviour. He is a member of several academies, including the National Academy of the US, and the Spanish Medical Academy and has received several international awards including The Kavli award in Neuroscience 2008. He was president of the Federation of European Neuroscience Organisation (FENS) 2010-2012 and Secretary General of IBRO 2013 – 2015. He is a founding member of HBP.

Sten Grillner has unravelled the intrinsic function of the modular network organization underlying fundamental aspects of our motor repertoire. His initial work defined the basic organisation of the mammalian locomotor system in terms of supraspinal command systems, spinal networks coordinating the movements (CPGs), and the sensory control of the CPGs. To address the next level question - the molecular, cellular and synaptic design of these neuronal circuits - he developed a novel and simpler vertebrate model (lamprey). The different network interneurons, their synaptic interaction (transmitters, receptor subtypes), and their membrane properties (ion channel subtypes expressed) have been identified. The palette of different subtypes of ion channels expressed in different neurones is found to be of critical importance for network function. Through an interaction between detailed multi-faceted experimentation and large scale modelling with biophysically realistic numbers of Hodgkin-Huxley neurons, the operation of this entire motor control system has been uncovered.

In the more recent work related to the forebrain mechanisms underlying selection of behaviour he has demonstrated that the basal ganglia, the dopamine innervation, habenulae and the projection pattern from the lamprey pallium are all evolutionary conserved to a considerable degree. This includes overall neural organization and connectivity, transmitters, membrane properties including expression of ion channels. The lamprey belongs to the oldest group of now living vertebrates, and it diverged from the evolutionary leading up to mammals some 500 million years ago. The conclusion is that these forebrain circuits underlying selection of behaviour and decision-making had evolved very early in vertebrate evolution – and have remained practically unchanged in basic design since the dawn of vertebrate evolution. The lamprey motor system can be regarded as a blue-print of the vertebrate motor system

Fecha y hora: Viernes, 17 de enero de 2020, 12:30 h.

Lugar: Seminario IV