Showing papers on "Cuneate nucleus published in 2001"

Afferent synaptic contacts on glycine‐immunoreactive neurons in the rat cuneate nucleus

Abstract: This study was aimed to clarify whether the primary afferent terminals (PATs), GABAergic terminals, and glutamatergic terminals made direct synaptic contacts with glycine-IR neurons in the cuneate nucleus of rats. In this connection, injection of the anterograde tracer WGA-HRP into brachial plexus, antiglycine preembedding immunoperoxidase, and anti-GABA, along with antiglutamate postembedding immunogold labeling, were used to identify the PATs, glycine-IR neurons, GABA-IR terminals, and glutamate-IR terminals, respectively. The present results showed that HRP-labeled PATs, immunoperoxidase-labeled glycine-IR terminals, immunogold-labeled GABA-IR, and glutamate-IR terminals made axodendritic synaptic contacts with immunoperoxidase-labeled glycine-IR neurons. The latter three presynaptic elements also formed axosomatic synapses with glycine-IR neurons. Statistical analysis has shown that the minimum diameter of the glycine-IR dendrites postsynaptic to the above-mentioned four presynaptic elements did not differ significantly. In addition, the synaptic ratio of the glutamate-IR terminals on the glycine-IR dendrites was higher than that of GABA-IR terminals. The synaptic ratio of the GABA-IR terminals on glycine-IR dendrite was in turn higher than that of the PATs and glycine-IR terminals. It is suggested that the PATs and glutamate-IR terminals on the glycine-IR neurons may be involved in subsequent postsynaptic inhibition for spatial precision of lateral inhibition. On the other hand, the GABA-IR and glycine-IR terminals which make synaptic contacts with the dendrites of glycine-IR neurons may provide a putative means for disinhibition or facilitation to maintain the baseline neuronal activity in the rat cuneate nucleus. The results of quantitative analysis suggest that glutamate act as the primary excitatory neurotransmitter, while GABA, when compared with glycine, may serve as a more powerful inhibitory neurotransmitter on glycine-IR neurons in the rat cuneate nucleus. Synapse 41:139–149, 2001. © 2001 Wiley-Liss, Inc.

Transmission Security for Single, Hair Follicle–Related Tactile Afferent Fibers and Their Target Cuneate Neurons in Cat

Abstract: Transmission from single, identified hair follicle afferent (HFA) nerve fibers to their target neurons of the cuneate nucleus was examined in anesthetized cats by means of paired recording from ind...

A Realistic Computational Model of the Local Circuitry of the Cuneate Nucleus

Abstract: Intracellular recordings obtained under cutaneous and lemniscal stimulation show that the afferent fibers can establish excitatory and inhibitory synaptic connections with cuneothalamic neurons [5]. In addition, distinct types of recurrent collaterals with the capability of either exciting or inhibiting both cuneothalamic neurons and interneurons were also discovered [6]. With these data we have generated hypothesis about which circuits are implicated and also developed realistic computational models to test the hypothesis and study the cuneate properties [17,18]. The results show that the cuneate could perform spatial and temporal filtering and therefore detect dynamic edges.

A Cuneate-Based Network and Its Application as a Spatio-Temporal Filter in Mobile Robotics

Abstract: This paper focuses on a cuneate-based network (CBN), a connectionist model of the cuneate nucleus that shows spatial and temporal filtering mechanisms. The circuitry underlying these mechanisms were analyzed in a previous study by means of a realistic computational model [9,10] of the cuneate. In that study we have used experimental data (intracellular and extracellular recordings) obtained in cat in vivo [2,3] to guide and test the model. The CBN is a high-level description of the realistic model that allows to focus on the functional features and hide biological details. To demonstrate the CBN capabilities we have applied it to solve a filtering problem in mobile robotics.

The cerebral cortex modulates the cutaneous transmission through the dorsal column nuclei

Abstract: Summary. Introduction. The mechanisms used by the cerebral cortex to modulate the cutaneous information at prethalamic levelhave been scarcely studied. This article reviews experimental evidence leading to a better understanding of this issue at the levelof the cuneate nucleus (Burdach nucleus). Development. The primary afferents and the corticocuneate fibers make synapticcontact with cuneothalamic neurons and with inhibitory interneurons in the middle cuneate nucleus. By stimulating the skin atdifferent places while recording the cuneothalamic intracellular activity in anaesthetized animals with the cortex intact, withthe cortex pharmacologically inactivated, or in absence of a cerebral cortex it was possible to ascertain the functional role ofthe corticocuneate fibers. The primary afferents activated by stimulating a particular zone of the skin induce monosynapticexcitation on a group of cuneothalamic cells at the same time at which inhibit, through intranuclear interneurons, neighboringcuneothalamic cells with unmatched receptive fields. Similarly, the corticocuneate cells receiving information from the stimulated skinfurther increase the excitation of the cuneothalamic neurons with matched receptive fields while inhibiting others with unmatched fields.The cortex exaggerates an excited center surrounded by an inhibited periphery thus increasing the tactile discrimination both spatiallyand temporally which is essential for exploratory and manipulative purposes. [REV NEUROL 2001; 33: 448-54]

Research report Somatotopic reorganization in the brainstem and thalamus following peripheral nerve injury in adult primates

Abstract: Injury-induced reorganization of central somatotopic maps is a phenomenon that has proven to be useful for elucidating the mechanisms and time course of neural plasticity. To date, the overwhelming majority of this line of research has focused on such plastic events in cortical areas, at the expense of subcortical structures. In this study, we used multi-unit electrophysiological recording techniques to assess the somatotopic organization of brainstem and thalamic areas following chronic survival from paired median and ulnar nerve section in adult squirrel monkeys. We report that the extent of cutaneously-driven reorganization in both the cuneate nucleus of the brainstem and the ventroposterior lateral nucleus of the thalamus is comparable to that previously documented for area 3b of cortex. These observations are consistent with those previously reported in thalamus, and are unique for brainstem. © 2001 Elsevier Science B.V. All rights reserved.