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Synaptic connections between puramidal cells and interneurons in superficial layers of the neocortex

100%

Wozny C. , Williams S.

Acta Neurobiologiae Experimentalis

2009

tom 69

nr 3

To understand how sensory information is processed in the neocortex it is essential to investigate the neuronal microcircuits and the dynamics of cortical signalling. Layer 1 of the neocortex is a cell-sparse and synaptic dense zone. Layer 1 neurons are exclusively GABAergic. Here, we recorded from layer 1 interneurons in the adult neocortex and we found that layer 1 interneurons displayed highly diverse morphological and electrophysiological properties. Electrophysiologically, L1 interneurons showed accommodating, non-accommodating, accelerating, bursting, irregular and stuttering behaviour upon a sustained current injection. Based on their morphology, various types including neurogliaform cells, basket cells and axo-axonic cells could be identifi ed. Layer 1 interneurons are electrically coupled and provide inhibitory synaptic input to fellow layer 1 interneurons and layer 2/3 pyramidal neurons. However, little is known about the translaminar excitatory innervation of layer 1 interneurons. We performed pairedrecordings from layer 1 and layer 2/3 neurons in adult neocortical slices. The properties of unitary EPSPs were found to be dependent on the identity of the postsynaptic neuron. Our results suggest that L2/3 pyramidal neurons effi ciently recruit layer 1 interneurons providing a substrate for feedback inhibition, which might contribute to the sparse fi ring of L2/3 pyramidal neurons observed in-vivo.

Three-dimensional finite element simulation of intrusion of the maxillary central incisor

61%

Ryniewicz W. , Ryniewicz A. M. , Bojko Ł. , Pełka P. , Filipek J. , Williams S. , Loster B. W.

Biocybernetics and Biomedical Engineering

2016

tom Vol. 36, no. 2

385--390

Purpose: The aim of this study is to generate a global digital model of treatment, analysis of stress distribution and displacements: in a construction of the bracket, in the incisor with bonded bracket, in tissues of the incisor, in a periodontal membrane and in an alveolus. Methods: An orthodontic therapy was provided with a three-dimensional model of a unique Cannon Ultra bracket. The placement of the bracket to the incisor was provided according to clinical standards. Composite material was placed between the rough surface of the bracket's base and labial incisor surface – which, in a digital model, resulted in contact without displacement. The bracket was loaded. An orthodontic arch wire was free to move in a wing slot of the bracket. For simplification, a force vector was parallel to the longitudinal axis of the incisor. A clamper was set on the surface of the cortical bone of the alveolus. The model was divided into a finite number of tetrahedral elements. To calculate the distribution of stress Ansys Workbench software was used. Results: The stress values indicate that there were no tissue overloaded areas. The stress distribution was regular in the periodontal ligament. Slight movements were observed with maximal values in the area of apex. Conclusions: This study simulation proves that tissues surrounding the tooth were influ-enced mechanically by the force loaded on the bracket. [...]