Apical length governs computational diversity of layer 5 pyramidal neurons

Abstract

<jats:p>Anatomical similarity across the neocortex has led to the common assumption that the circuitry is modular and performs stereotyped computations. Layer 5 pyramidal neurons (L5PNs) in particular are thought to be central to cortical computation because of their extensive arborisation and nonlinear dendritic operations. Here, we demonstrate that computations associated with dendritic Ca2+ plateaus in mouse L5PNs vary substantially between the primary and secondary visual cortices. L5PNs in the secondary visual cortex show reduced dendritic excitability and smaller propensity for burst firing. This reduced excitability is correlated with shorter apical dendrites. Using numerical modelling, we uncover a universal principle underlying the influence of apical length on dendritic backpropagation and excitability, based on a Na+ channel-dependent broadening of backpropagating action potentials. In summary, we provide new insights into the modulation of dendritic excitability by apical dendrite length and show that the operational repertoire of L5PNs is not universal throughout the brain.</jats:p>

Thalamus and claustrum control parallel layer 1 circuits in retrosplenial cortex

“…Our results reproduce these observations. Layer 5 is not a homogenous layer, often divided into sublayers 5A and 5B (Geijo-barrientos et al, 2019; Sempere-Ferràndez et al, 2018; Sigwald et al, 2020; Sripanidkulchai and Wyss, 1987; Yamawaki et al, 2016a), and contains a variety of pyramidal cells, including the thin-tufted and thick-tufted neurons whose apical dendritic branches may show different sublaminar targeting in layer 1 (Galloni et al, 2020; Wyss et al, 1990). Further work is needed to determine whether any particular subtype of layer 5 pyramidal neurons may exhibit substantial TC-evoked responses, but our results, reporting significantly larger responses to TC input by LR neurons, suggest LR cells are the predominant spatial information-encoding subtype within RSG.…”

Dendritic domain-specific sampling of long-range axons shapes feedforward and feedback connectivity of L5 neurons

“…V2M is defined in the Mouse Brain In Stereotaxic Coordinates atlas (Franklin & Paxinos 2007) which can be used to guide viral injections. Furthermore, as this atlas is based on cytoarchitecture, thus V2M can be visually distinguished and selectively targeted in slice recordings, as has previously been done (Galloni et al 2020, Young et al 2021. For whole-brain rabies tracing, on the other hand, we adopted the more recently developed Allen Common Coordinate Framework (CCFv3, (Wang et al 2020a).…”

“…It is thus likely that spatial and multisensory contextual information carried by LP inputs (Roth et al 2016) interacts with FF visual input in the tuft compartment. However, the role of tuft integration is likely to differ from primary sensory cortices, considering that ttL5 neurons in the secondary visual cortex can have substantially different integrative properties (Galloni et al 2020). Contrary to thalamic input, cortical FB inputs target all three dendritic domains.…”

Genetically Encoded Calcium Indicators Can Impair Dendrite Growth of Cortical Neurons

“…The dendritic architecture of cortical neurons has been correlated with intelligence in humans (Goriounova et al, 2018). The length of the apical dendritic trunk of layer V pyramidal neurons determines excitability and propensity for burst firing (Galloni et al, 2020). So, if cells fail to mature properly with GECI expression in experimental models in vivo, the cognitive performance of the individual may be compromised.…”