Stroke subtypes and interventional studies for transient ischemic attack.

Transient ischemic attack (TIA) is the most important risk factor for ischemic stroke. The risk is the highest in the first hours after symptom onset, and treatment must be initiated in emergency. In the acute phase, antithrombotic agent is probably the most important treatment, but it is not excluded that lipid-lowering agents and/or antihypertensive drugs are also important.

The vibrissal system as a model of thalamic operations.

The highly segregated organization of the vibrissal system of rodents offers a unique opportunity to address key issues about thalamic operations in primary sensory and second order thalamic nuclei. In this short review, evidence showing that reticular thalamic neurons and relay cells with receptive fields on the same vibrissa form topographically closed loop connections has been summarized. Within whisker-related thalamic modules, termed barreloids, reticular axons synapse onto the cell bodies and dendrites of residing neurons as well as onto the distal dendrites of neurons that are located in adjacent barreloids.

Feedforward inhibitory control of sensory information in higher-order thalamic nuclei.

Sensory stimuli evoke strong responses in thalamic relay cells, which ensure a faithful relay of information to the neocortex. However, relay cells of the posterior thalamic nuclear group in rodents, despite receiving significant trigeminal input, respond poorly to vibrissa deflection. Here we show that sensory transmission in this nucleus is impeded by fast feedforward inhibition mediated by GABAergic neurons of the zona incerta.

Dendroarchitecture and lateral inhibition in thalamic barreloids.

Thalamic cells that relay vibrissa information to barrel cortex are clustered within whisker-related modules termed barreloids. Each barreloid receives input from one principal whisker and inhibitory inputs from reticular thalamic neurons with receptive fields that correspond to that same whisker. Although the proximal dendrites of relay cells are confined to their home barreloid, distal dendrites often extend into surrounding barreloids representing adjacent whiskers on the mystacial pad.

Synthesis of multiwhisker-receptive fields in subcortical stations of the vibrissa system.

This study addresses the origins of multiwhisker-receptive fields of neurons in the thalamic ventral posterior medial (VPM) nucleus of the rat. We sought to determine whether multiwhisker-receptive field synthesis occurs in VPM through convergent projections from the principalis (PrV) and interpolaris (SpVi) nuclei, or in PrV by intersubnuclear projections from the spinal trigeminal complex. We tested these hypotheses by recording whisker-evoked responses in PrV and VPM before and after electrolytic lesion of the SpVi in lightly anesthetized rats.

A map of angular tuning preference in thalamic barreloids.

A double-labeling protocol was used to determine how cells with different angular preferences to whisker motion distribute across the dimensions of a barreloid in the ventral posterior medial nucleus of the rat thalamus. Individual barreloids were labeled retrogradely by injecting Fluoro-Gold in identified barrel columns, and single relay cells (n = 30) pertaining to the labeled barreloids were stained juxtacellularly with Neurobiotin after determination of their angular tuning preference to controlled whisker deflection. Results show that cells with like angular preference are clustered within the barreloids.

The relay of high-frequency sensory signals in the Whisker-to-barreloid pathway.

The present study investigated the operational features of whisker-evoked EPSPs in barreloid cells and the ability of the whisker-to-barreloid pathway to relay high rates of whisker deflection in lightly anesthetized rats. Results show that lemniscal EPSPs are single-fiber events with fast rise times (<500 microsec) that strongly depress at short inter-EPSP intervals. They occur at short latencies (3.

Dendroarchitecture of relay cells in thalamic barreloids: a substrate for cross-whisker modulation.

A double-labeling protocol was used to determine how the dendroarchitecture of relay cells relates to the three-dimensional structure of barreloids in the ventral posterior medial nucleus of the rat thalamus. Single barreloids were retrogradely labeled by injecting Fluoro-Gold in identified barrel columns, and single relay cells activated by the same whisker, or by an adjacent whisker located on the same arc, were juxtacellularly labeled with biotinylated dextran. Results show that the dendritic field of relay cells is asymmetric, variously oriented with respect to the geometry of the barreloids, and that all cells extend dendrites in surrounding barreloids.

Substrate for cross-talk inhibition between thalamic barreloids.

A double-labeling protocol was used to determine whether thalamocortical and reticular thalamic cells with overlapping receptive fields form open or closed loop connections in the vibrissal system of the rat. Results show that individual reticular cells exclusively project to the barreloid representing the principal whisker of their receptive field. Furthermore, solid retrograde labeling of relay cells reveals that a large number extend dendrites outside their home barreloid.