Present address: Central Nervous System Stability and Degeneration Group, Research School of Biological Sciences, as 2above.
Development of structural and functional connectivity in the thalamocortical somatosensory pathway in the wallaby
Version of Record online: 6 JUN 2007
European Journal of Neuroscience
Volume 25, Issue 10, pages 3058–3070, May 2007
How to Cite
Leamey, C. A., Flett, D. L., Ho, S. M. and Marotte, L. R. (2007), Development of structural and functional connectivity in the thalamocortical somatosensory pathway in the wallaby. European Journal of Neuroscience, 25: 3058–3070. doi: 10.1111/j.1460-9568.2007.05556.x
- Issue online: 6 JUN 2007
- Version of Record online: 6 JUN 2007
- Received 2 November 2006, revised 14 March 2007, accepted 22 March 2007
- whisker pathway
Neuronal activity is implicated as a driving force in the development of sensory systems. In order for it to play a developmental role, however, the pathways involved must be capable of transmitting this activity. The relationship between afferent arrival, synapse formation and the onset of chemical neurotransmission has been examined using the advantageous model of a marsupial mammal, the wallaby (Macropus eugenii), to determine at what stage activity has the capacity to influence cortical development. It is known that thalamocortical afferents arrive in the somatosensory cortex on postnatal day (P)15 and that their growth cones reach to the base of the compact cell zone of the cortical plate. However, electronmicroscopy showed that thalamocortical synapses were absent at this stage. Glutamatergic responses were recorded in the cortex following stimulation of the thalamus in slices at this time but only in magnesium-free conditions. The responses were mediated entirely by N-methyl-d-aspartate (NMDA) receptors. From P28, responses could be recorded in normal magnesium and comprised a dominant NMDA-mediated component and a non-NMDA mediated component. At this time thalamocortical synapses were first identified and they were in the cortical plate. By P63 the non-NMDA-mediated component had increased relative to the NMDA-mediated component, and by P70 layer IV began to emerge and contained thalamocortical synapses. By P76 a fast non-NMDA-mediated peak dominated the response. This coincides with the appearance of cortical whisker-related patches and the onset in vivo of responses to peripheral stimulation of the whiskers.