Whereas barrel-related circuits process lemniscal inputs that transit through the thalamic barreloids, septa-related circuits process paralemniscal inputs and inputs that are relayed through the ventral lateral part of the ventral posterior medial nucleus (VPMvl). 
In the ventral posterior medial nucleus of the thalamus, two of these pathways convey information through the core and tail of barrel-associated structures, called barreloids.
Here we investigate neuronal responses in the rat primary somatosensory cortex (S1) and ventral posterior medial nucleus of the thalamus (VPM) during a tactile discrimination task that requires animals to associate two different tactile stimuli with two corresponding choices of spatial trajectory to be rewarded.
These findings suggest that top-down influences, which are more likely to play a role during active discrimination than during passive whisker stimulation, may alter the pattern of neuronal firing within both the distinct layers of the primary somatosensory cortex (S1) and the ventral posterior medial nucleus (VPM).
We show that the densest zone of calbindin immunoreactivity is part of a more extensive, calbindin-immunoreactive region that lies well within the medial tip of the ventral posterior medial nucleus (VPM), as delineated by other staining methods, and prove that the use of different anti-calbindin antibodies cannot account for differences in interpretations of the organization of the posterior thalamic region.
In all cases, regardless of the level of the injections, terminal fibers were consistently distributed in three main locations: the submedial nucleus; the ventral aspect of the basal ventral medial nucleus and ventral posterior nuclei; and, the dorsomedial aspect of the ventral posterior medial nucleus. In several cases with trigeminal lamina I injections, a terminal labeling patch was observed within the core of the ventral posterior medial nucleus.
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.
In addition, surviving PrV cells exhibit delayed and more spatially restricted ascending projections to the ventral posterior medial nucleus of the thalamus (VPm).
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.
Whole-cell voltage recordings were made in vivo in the ventral posterior medial nucleus (VPM) of the thalamus in urethane-anaesthetised young (postnatal day 16-24) rats.
Type II fibers are thin; branch sparsely in the tectum; and form small-sized, bushy arbors in the ventral posterior medial nucleus (VPM).
This study investigated the organization of a vibrissal pathway that arises from the interpolar division of the spinal trigeminal complex (SP5i), transits through the ventral posterior medial nucleus (VPM), and innervates the somatosensory cortical areas in the rat.
Using stereological techniques in six pairs of individually matched brains from schizophrenics and controls, we measured the volumes and obtained estimates of the number of neurons in the three subnuclei (parvocellular, pc; densocellular, dc; magnocellular, mc) of the mediodorsal nucleus (MD) and from the ventral posterior medial nucleus. MDmc and the control ventral posterior medial nucleus showed no significant changes in cell number.
We investigated the influence of four different behavioral states on tactile responses recorded simultaneously via arrays of microwires chronically implanted in the vibrissal representations of the rat ventral posterior medial nucleus (VPM) of the thalamus and the primary somatosensory cortex (SI).
They were aimed at one or more of the three main target areas of thermoreceptive-specific lamina I spinothalamic neurons [ i.e., the nucleus submedius, the dorsomedial aspect of the ventral posterior medial nucleus, and the ventral aspect of the basal ventral medial nucleus (vVMb)], following microelectrode mapping of somatosensory thalamus.
Simultaneous recordings of up to 48 single neurons per animal were used to characterize the long-term functional effects of sensory plastic modifications in the ventral posterior medial nucleus (VPM) of the thalamus following unilateral removal of facial whiskers in newborn rats.
Here, we addressed this issue by simultaneously recording the extracellular activity of up to 135 neurons in the primary somatosensory cortex, ventral posterior medial nucleus of the thalamus, and trigeminal brainstem complex of adult rats, before and after a reversible sensory deactivation was produced by subcutaneous injections of lidocaine.
Extracellular single-unit recordings and controlled whisker stimuli were used to compare response properties of cells in the barreloids of the ventral posterior medial nucleus of the thalamus and the barrels in the rat primary somatosensory cortex.
Six to 14 mo after the facial nerve section, simultaneous recordings of neuronal ensembles located in the ventral posterior medial nucleus (VPM) of the thalamus revealed a marked reduction in receptive field (RF) size (in terms of number of whiskers), and the formation of abnormal RF surrounds, spanning the face and contiguous body regions.
This region corresponded to areas of intense anterograde labeling following injections placed in the ventromedial portion of the ventral posterior medial nucleus of the thalamus at the only sites where neural responses could be elicited by stimulation of ipsilateral intraoral structures.
In addition, sensory regions of the forebrain and brain stem (e.g., nucleus gracilis and ventral posterior medial nucleus of the thalamus) had a lower basal metabolic rate than control animals.
The present study examined the role of the ventral posterior medial nucleus of the thalamus (VPM) in classical heart rate (HR) conditioning using an acoustic conditioned stimulus (CS) and a corneal air puff unconditioned stimulus (US).
Terminals from the posterior interposed nucleus were located slightly rostral and lateral to those from the lateral nucleus, mainly around the border between the ventral lateral nucleus and the ventral posterior medial nucleus.
The CO-weak compartment, containing only calbindin cells, forms isolated zones throughout VPL and expands as a cap covering the posterior surface of the ventral posterior medial nucleus (VPM).
The projection from the whiskers of the rat to the S-I (barrel) cortex is segregated into two separate pathways--a lemniscal pathway relayed by the ventral posterior medial nucleus (VPM) to cortical barrels, and a paralemniscal pathway relayed by the rostral sector of the posterior complex (POm) to the matrix between, above, and below barrels.
The rodent barrel field cortex integrates somatosensory information from two separate thalamic nuclei, the ventral posterior medial nucleus (VPM) and the rostral sector of the posterior complex (POm).
(3) In ventral posterior medial nucleus of thalamus, there was an initial transient 200-300% increase in binding, peaking at PND10, followed by a steady decline in binding.
The pathway we examined extended from the periphery to sensory cortex and included: the nodose ganglion (periphery)----solitary nucleus (medulla)----parabrachial nucleus (pons)----ventral posterior medial nucleus (thalamus)----visceral and taste sensory areas (cortex). In the parabrachial nucleus of the pons many neuronal cell bodies could be shown to be immuno-positive for one of 5 neuropeptides (CCK, ENK, NT, SOM, SP) and have a projection to the ventral posterior medial nucleus of the thalamus. In the ventral posterior medial nucleus of the thalamus several neuronal cell bodies were shown to be immuno-positive for one of 3 neuropeptides (CCK, ENK, SOM) and project to the visceral and taste sensory cortex.
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