Postnatal development of the mouse barrel cortex

: investigating the intrinsic properties of spiny stellate neurons across the first two weeks of life

Abstract

Sensation and perception are key aspects of cognition and healthy adult brain functioning. A region of the brain called the somatosensory cortex is responsible for the integration of sensory information. At the level of cortical circuits, key developmental time windows have been identified where significant changes in plasticity, synaptogenesis and spontaneous activity occur. It appears that disturbances to these processes can result in global impacts on cognition and behaviour, potentially underlying various neurodevelopmental disorders. A starting point to unpicking this complexity is to decode the biophysical changes that occur to healthy neurons during development. This report presents whole cell current clamp electrophysiology data obtained from layer IV spiny stellate neurons in the mouse barrel cortex over the first 2 weeks of life (postnatal days 4 - 14), focusing on changes to intrinsic properties with age, internal solution and temperature. Developmental changes were found in both the passive and active dynamics, with cells displaying decreased input resistance, increased action potential height, increased rate of rise and fall and decreased action potential width with age. A novel finding of this report is that intracellular infusion of biocytin induced development-dependent, temperature-independent changes in the active and passive dynamics of cells. These findings highlight the necessity for fine-tuning of concentrations of dyes when performing intracellular recordings, while widespread changes in the neuronal dynamics with altered temperature indicate the importance for standardised conditions in electrophysiology experiments. The observations in this report highlight how maturation of intrinsic properties is a complex, non-linear process that is prone to perturbation by external factors. These changes are likely due to developmental alterations in neuronal size, morphology, ion channel expression and activation and may reflect an overall increase in excitability and temporal precision of spiny stellate cells as they mature, allowing for more refined neural representation of sensory stimuli.

Date of Award	1 Oct 2019
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Michael C Ashby (Supervisor)