Biology subjects

Jamann, N.

Publications and source records attributed to Jamann, N..

3 recordsLinked to original sources

bioRxiv2023

Visuomotor experience induces functional and structural plasticity of chandelier cells

Detailed characterization of interneuron types in primary visual cortex (V1) has greatly contributed to understanding visual perception, yet the role of chandelier cells (ChCs) in visual processing remains poorly characterized. Using viral tracing we found that V1 ChCs predominantly receive monosynaptic input from local layer 5 pyramidal cells and higher-order cortical regions. Two-photon calcium imaging and convolutional neural network modelling revealed that ChCs are visually responsive but weakly selective for stimulus content. In mice running in a virtual tunnel, ChCs respond strongly to events known to elicit arousal, including locomotion and visuomotor mismatch. Repeated exposure of the mice to the virtual tunnel was accompanied by reduced visual responses of ChCs and structural plasticity of ChC boutons and axon initial segment length. Finally, ChCs only weakly inhibited pyramidal cells. These findings suggest that ChCs provide an arousal-related signal to layer 2/3 pyramidal cells that may modulate their activity and/or gate plasticity of their axon initial segments during behaviorally relevant events.

neuroscience↗

bioRxiv2022

Sodium channel endocytosis drives axon initial segment plasticity

Activity-dependent plasticity of the axon initial segment (AIS) endows neurons with the ability to adapt action potential output to changes in network activity. Action potential initiation at the AIS highly depends on the clustering of voltage-gated sodium channels, however the molecular mechanisms regulating their plasticity remain largely unknown. Here, we used novel genetic tools to endogenously label sodium channels and their scaffolding protein, to reveal their nanoscale organization and longitudinally image AIS plasticity in hippocampal neurons, in slices and primary cultures. We find that induction of NMDA receptor-mediated long-term synaptic depression is linked to a rapid and local endocytosis of sodium channels from the distal AIS. These data reveal a novel fundamental mechanism for rapid activity-dependent AIS reorganization sharing conserved features with synaptic plasticity.

neuroscience↗

bioRxiv2020

Sensory input drives rapid homeostatic scaling of the axon initial segment in mouse barrel cortex

The axon initial segment (AIS) is an important axonal microdomain for action potential initiation and implicated in the regulation of neuronal excitability during activity-dependent cortical plasticity. While structural AIS plasticity has been suggested to fine-tune neuronal activity when network states change, whether it acts as a homeostatic regulatory mechanism in behaviorally relevant contexts remains poorly understood. Using an in vivo model of the mouse whisker-to-barrel pathway in combination with immunofluorescence, confocal analysis and patch-clamp electrophysiological recordings, we observed bidirectional AIS plasticity. Furthermore, we find that structural and functional AIS remodeling occurs in distinct temporal domains: long-term sensory deprivation elicits an AIS length increase, accompanied with an increase in neuronal excitability, while sensory enrichment results in a rapid AIS shortening, accompanied by a decrease in action potential generation. Our findings highlight a central role of the AIS in the homeostatic regulation of neuronal input-output relations.

neuroscience↗