Showing papers on "Thalamus published in 1999"
TL;DR: Spontaneous magnetoencephalographic activity was recorded in awake, healthy human controls and in patients suffering from neurogenic pain, tinnitus, Parkinson's disease, or depression, indicating the presence of a thalamocortical dysrhythmia which is responsible for all the above mentioned conditions.
Abstract: Spontaneous magnetoencephalographic activity was recorded in awake, healthy human controls and in patients suffering from neurogenic pain, tinnitus, Parkinson's disease, or depression. Compared with controls, patients showed increased low-frequency θ rhythmicity, in conjunction with a widespread and marked increase of coherence among high- and low-frequency oscillations. These data indicate the presence of a thalamocortical dysrhythmia, which we propose is responsible for all the above mentioned conditions. This coherent θ activity, the result of a resonant interaction between thalamus and cortex, is due to the generation of low-threshold calcium spike bursts by thalamic cells. The presence of these bursts is directly related to thalamic cell hyperpolarization, brought about by either excess inhibition or disfacilitation. The emergence of positive clinical symptoms is viewed as resulting from ectopic γ-band activation, which we refer to as the “edge effect.” This effect is observable as increased coherence between low- and high-frequency oscillations, probably resulting from inhibitory asymmetry between high- and low-frequency thalamocortical modules at the cortical level.
1,212 citations
TL;DR: The results suggest that descending axons, rather than apical dendrites, are primarily activated by MCS, and highlight the thalamus as the key structure mediating functional MCS effects, and propose a model of MCS action.
Abstract: Although electrical stimulation of the precentral gyrus (MCS) is emerging as a promising technique for pain control, its mechanisms of action remain obscure, and its application largely empirical. Using positron emission tomography (PET) we studied regional changes in cerebral flood flow (rCBF) in 10 patients undergoing motor cortex stimulation for pain control, seven of whom also underwent somatosensory evoked potentials and nociceptive spinal reflex recordings. The most significant MCS-related increase in rCBF concerned the ventral-lateral thalamus, probably reflecting cortico-thalamic connections from motor areas. CBF increases were also observed in medial thalamus, anterior cingulate/orbitofrontal cortex, anterior insula and upper brainstem; conversely, no significant CBF changes appeared in motor areas beneath the stimulating electrode. Somatosensory evoked potentials from SI remained stable during MCS, and no rCBF changes were observed in somatosensory cortex during the procedure. Our results suggest that descending axons, rather than apical dendrites, are primarily activated by MCS, and highlight the thalamus as the key structure mediating functional MCS effects. A model of MCS action is proposed, whereby activation of thalamic nuclei directly connected with motor and premotor cortices would entail a cascade of synaptic events in pain-related structures receiving afferents from these nuclei, including the medial thalamus, anterior cingulate and upper brainstem. MCS could influence the affective-emotional component of chronic pain by way of cingulate/orbitofrontal activation, and lead to descending inhibition of pain impulses by activation of the brainstem, also suggested by attenuation of spinal flexion reflexes. In contrast, the hypothesis of somatosensory cortex activation by MCS could not be confirmed by our results.
523 citations
TL;DR: An extended right hemisphere network including frontal (anterior cingulate-dorsolateral cortical)-inferior parietal-thalamic and brainstem (ponto-mesencephalic tegmentum) structures was found when subjects waited for and rapidly responded to a centrally presented white dot by pressing a response key with the right-hand thumb.
434 citations
TL;DR: Long-standing speculations about the similarities between dreaming and psychotic cognition are substantiated by describing the role of an over(re)active cortical cholinergic input system in either condition.
419 citations
TL;DR: The results of the activation study indicate that different functions in pain processing can be attributed to different brain regions.
Abstract: Brain imaging with positron emission tomography has identified some of the principal cerebral structures of a central network activated by pain. To discover whether the different cortical and subcortical areas process different components of the multidimensional nature of pain, we performed a regression analysis between noxious heat-related regional blood flow increases and experimental pain parameters reflecting detection of pain, encoding of pain intensity, as well as pain unpleasantness. The results of our activation study indicate that different functions in pain processing can be attributed to different brain regions; ie, the gating function reflected by the pain threshold appeared to be related to anterior cingulate cortex, the frontal inferior cortex, and the thalamus, the coding of pain intensity to the periventricular gray as well as to the posterior cingulate cortex, and the encoding of pain unpleasantness to the posterior sector of the anterior cingulate cortex.
394 citations
TL;DR: An extensive collation of connection tracing studies revealed approximately 1500 extrinsic connections between the cortical areas and thalamic nuclei of the cat cerebral hemisphere, and the organization of the entire cortico-thalamic network was investigated.
Abstract: Data on connections between the areas of the cerebral cortex and nuclei of the thalamus are too complicated to analyse with naked intuition. Indeed, the complexity of connection data is one of the major challenges facing neuroanatomy. Recently, systematic methods have been developed and applied to the analysis of the connectivity in the cerebral cortex. These approaches have shed light on the gross organization of the cortical network, have made it possible to test systematically theories of cortical organization, and have guided new electrophysiological studies. This paper extends the approach to investigate the organization of the entire corticothalamic network. An extensive collation of connection tracing studies revealed ~1500 extrinsic connections between the cortical areas and thalamic nuclei of the cat cerebral hemisphere. Around 850 connections linked 53 cortical areas with each other, and around 650 connections linked the cortical areas with 42 thalamic nuclei. Non-metric multidimensional scaling, optimal set analysis and non-parametric cluster analysis were used to study global connectivity and the ‘place’ of individual structures within the overall scheme. Thalamic nuclei and cortical areas were in intimate connectional association. Connectivity defined four major thalamocortical systems. These included three broadly hierarchical sensory or sensory/motor systems (visual and auditory systems and a single system containing both somatosensory and motor structures). The highest stations of these sensory/motor systems were associated with a fourth processing system composed of prefrontal, cingulate, insular and parahippocampal cortex and associated thalamic nuclei (the ‘fronto-limbic system’). The association between fronto-limbic and somato-motor systems was particularly close.
380 citations
TL;DR: In beta3 knockout mice, GABAA-mediated inhibition was nearly abolished in reticular nucleus, but was unaffected in relay cells, and oscillatory synchrony was dramatically intensified, suggesting that recurrent inhibitory connections within reticle nucleus act as "desynchronizers."
Abstract: Neuronal rhythmic activities within thalamocortical circuits range from partially synchronous oscillations during normal sleep to hypersynchrony associated with absence epilepsy. It has been proposed that recurrent inhibition within the thalamic reticular nucleus serves to reduce synchrony and thus prevents seizures. Inhibition and synchrony in slices from mice devoid of the gamma-aminobutyric acid type-A (GABAA) receptor beta3 subunit were examined, because in rodent thalamus, beta3 is largely restricted to reticular nucleus. In beta3 knockout mice, GABAA-mediated inhibition was nearly abolished in reticular nucleus, but was unaffected in relay cells. In addition, oscillatory synchrony was dramatically intensified. Thus, recurrent inhibitory connections within reticular nucleus act as "desynchronizers."
359 citations
TL;DR: The belt and parabelt regions appear to be concerned with integrative and associative functions involved in pattern perception and object recognition and connect with regions of temporal, parietal, and frontal cortex that mediate additional auditory functions, including space perception and auditory memory.
357 citations
TL;DR: Despite the lack of cortical innervation by thalamic axons, neocortical region-specific gene expression developed normally and provides evidence that patterning mechanisms intrinsic to the neocortex specify the basic organization of its functional subdivisions.
Abstract: There is a long-standing controversy regarding the mechanisms that generate the functional subdivisions of the cerebral neocortex. One model proposes that thalamic axonal input specifies these subdivisions; the competing model postulates that patterning mechanisms intrinsic to the dorsal telencephalon generate neocortical regions. Gbx-2 mutant mice, whose thalamic differentiation is disrupted, were investigated. Despite the lack of cortical innervation by thalamic axons, neocortical region-specific gene expression (Cadherin-6, EphA-7, Id-2, and RZR-beta) developed normally. This provides evidence that patterning mechanisms intrinsic to the neocortex specify the basic organization of its functional subdivisions.
340 citations
TL;DR: It is argued that a peripheral mechanism of inhibition is incorrectly inferred from inhibition data available to date, which suggests that inhibitory processes always involve the cortex, and inhibitory effects are exerted upstream from the primary motor cortex.
340 citations
TL;DR: Functional magnetic resonance imaging findings specify differences between somatosensory and pain sensation and suggest a number of rich avenues for future research.
Abstract: Brain activity was studied with functional magnetic resonance imaging (fMRI) following thermal stimulation. Two groups (n = 6/group) of human male volunteers were given up to four noxious (46 degrees C) and four non-noxious (41 degrees C) stimuli. In the 46 degrees C experiment, positive signal changes were found in the frontal gyri, anterior and posterior cingulate gyrus, thalamus, motor cortex, somatosensory cortex (SI and SII), supplementary motor area, insula, and cerebellum. Low-level negative signal changes appeared in the amygdala and hypothalamus. All regions activated by 46 degrees C were also activated by 41 degrees C. However, except for SI and thalamus, significantly more activation was observed for the 46 degrees C stimulus. A significant attenuation of the signal change was observed by the third stimulus for the 46 degrees C, but not for 41 degrees C experiment. Similar findings were replicated in the second group. These fMRI findings specify differences between somatosensory and pain sensation and suggest a number of rich avenues for future research.
TL;DR: Recording in the lateral geniculate nucleus of awake behaving ferrets revealed patterns of spontaneous activity that reflect a reshaping of retinal drive within higher visual stages, which emerge from interactions between retina, thalamus, and cortex.
Abstract: The properties of spontaneous activity in the developing visual pathway beyond the retina are unknown. Multielectrode recordings in the lateral geniculate nucleus (LGN) of awake behaving ferrets, before eye opening, revealed patterns of spontaneous activity that reflect a reshaping of retinal drive within higher visual stages. Significant binocular correlations were present only when cortico-thalamic feedback was intact. In the absence of retinal drive, cortico-thalamic feedback was required to sustain correlated LGN bursting. Activity originating from the contralateral eye drove thalamic activity far more strongly than that originating from the ipsilateral eye. Thus, in vivo patterns of LGN spontaneous activity emerge from interactions between retina, thalamus, and cortex.
TL;DR: It now appears that the connectivity of the corticofugal feedback pathway is also fundamentally linked to the orientation preference of the cortical cells involved.
Abstract: The cerebral cortex receives sensory input from the periphery by means of thalamic relay nuclei, but the flow of information goes both ways. Each cortical area sends a reciprocal projection back to the thalamus. In the visual system, the synaptic relations that govern the influence of thalamic afferents on orientation selectivity in the cortex have been studied extensively. It now appears that the connectivity of the corticofugal feedback pathway is also fundamentally linked to the orientation preference of the cortical cells involved.
TL;DR: The patterns of thalamo‐amygdala connectivity observed support previous parcellation schemes that segregate the LA into dorsal, medial, and lateral areas, and suggest that the LA should be further divided into anterior and posterior parts.
Abstract: Projections to the amygdala from the auditory thalamus have been implicated in the associative conditioning of fear responses to acoustic stimuli. Thalamo-amygdala auditory projections enter the amygdala via the lateral nucleus (LA). It is well documented that these projections originate in the medial division (MGm) of the medial geniculate nucleus (MGN), the posterior intralaminar nucleus (PIN), and the suprageniculate nucleus (Sg). It is not known, however, whether these thalamic projections terminate in a topographic fashion within the LA. We therefore used several retrograde tract tracing techniques to determine whether the terminations of thalamo-amygdala fibers have a topographic organization within the LA. These tracers were injected into various locations within the LA, and the distribution of the retrogradely labeled cells throughout the thalamus was analyzed. In general, rostral to caudal distinctions in the thalamus are maintained in the LA, such that projections from throughout the MGN terminate in the anterior part of the LA, whereas the caudal part of the MGN projects to the caudal part of the LA. Furthermore, the density of cells that give rise to thalamo-amygdala projections varies within each thalamic nucleus along the rostro-caudal axis. The patterns of thalamo-amygdala connectivity observed support previous parcellation schemes that segregate the LA into dorsal, medial, and lateral areas, and suggest that the LA should be further divided into anterior and posterior parts. In addition to the well-known projections to the LA originating from PIN, MGN, and Sg, we also found substantial projections from the dorsal portion of the MGN (MGd) and the lateral posterior thalamic nucleus (LP). These findings suggest that some of the functional segregation in the thalamus may be preserved in the LA, and that the role of the MGd and LP in thalamo-amygdala transmission should be reconsidered.
TL;DR: The spinothalamic tract projects to the medial and lateral thalamus and, based on positron emission tomography studies, activates several cortical areas, including the anterior cingulate gyrus (BA 24 and 25), the lateral basal frontal cortex, and the mesiofrontal cortex.
Abstract: Angina pectoris often results from ischemic episodes that excite chemosensitive and mechanoreceptive receptors in the heart. Ischemic episodes release a collage of chemicals, including adenosine and bradykinin, that excites the receptors of the sympathetic and vagal afferent pathways. Sympathetic afferent fibers from the heart enter the upper thoracic spinal cord and synapse on cells of origin of ascending pathways. This review focuses on the spinothalamic tract, but other pathways are excited as well. Excitation of spinothalamic tract cells in the upper thoracic and lower cervical segments, except C7 and C8 segments, contributes to the anginal pain experienced in the chest and arm. Cardiac vagal afferent fibers synapse in the nucleus tractus solitarius of the medulla and then descend to excite upper cervical spinothalamic tract cells. This innervation contributes to the anginal pain experienced in the neck and jaw. The spinothalamic tract projects to the medial and lateral thalamus and, based on positron emission tomography studies, activates several cortical areas, including the anterior cingulate gyrus (BA 24 and 25), the lateral basal frontal cortex, and the mesiofrontal cortex.
TL;DR: The results demonstrate that eachHCN channel transcript has a unique distribution in the brain and suggest that the heterogeneity of neuronal Ih may be, at least in part, due to the differential expression of HCN channel genes.
Abstract: Hyperpolarization-activated cation currents, termed I(h), are observed in a variety of neurons. Four members of a gene family encoding hyperpolarization-activated cyclic-nucleotide-gated cation channels (HCN1-4) have been cloned. The regional expression and cellular localization of the four HCN channel types in mouse brain was investigated using in situ hybridization. The expression of HCN1 was restricted to the olfactory bulb, cerebral cortex, hippocampus, superior colliculus and cerebellum. In contrast, HCN2 transcripts were found at high levels nearly ubiquitously in the brain, and the strongest signals were seen in the olfactory bulb, hippocampus, thalamus and brain stem. HCN3 was uniformly expressed at very low levels throughout the brain. Finally, HCN4 transcripts were prominently expressed selectively in the thalamus and olfactory bulb. Some neurons expressed two or more HCN channel transcripts including hippocampal pyramidal neurons (HCN1, HCN2 and low levels of HCN 4) and thalamic relay neurons (HCN2 and HCN4). Our results demonstrate that each HCN channel transcript has a unique distribution in the brain. Furthermore, they suggest that the heterogeneity of neuronal I(h) may be, at least in part, due to the differential expression of HCN channel genes.
TL;DR: Behavior experiments demonstrate that DC lesions reduce the nocifensive responses produced by noxious stimulation of the pancreas and duodenum, as well as the electrophysiological responses of ventral posterolateral neurons to these stimuli.
Abstract: A limited midline myelotomy at T10 can relieve pelvic cancer pain in patients. This observation is explainable in light of strong evidence in support of the existence of a visceral pain pathway that ascends in the dorsal column (DC) of the spinal cord. In rats and monkeys, responses of neurons in the ventral posterolateral thalamic nucleus to noxious colorectal distention are dramatically reduced after a lesion of the DC at T10, but not by interruption of the spinothalamic tract. Blockade of transmission of visceral nociceptive signals through the rat sacral cord by microdialysis administration of morphine or 6-cyano-7-nitroquinoxaline-2,3-dione shows that postsynaptic DC neurons in the sacral cord transmit visceral nociceptive signals to the gracile nucleus. Retrograde tracing studies in rats demonstrate a concentration of postsynaptic DC neurons in the central gray matter of the L6-S1 spinal segments, and anterograde tracing studies show that labeled axons ascend from this region to the gracile nucleus. A similar projection from the midthoracic spinal cord ends in the gracile and cuneate nuclei. Behavioral experiments demonstrate that DC lesions reduce the nocifensive responses produced by noxious stimulation of the pancreas and duodenum, as well as the electrophysiological responses of ventral posterolateral neurons to these stimuli. Repeated regional blood volume measurements were made in the thalamus and other brain structures in anesthetized monkeys in response to colorectal distention by functional MRI. Sham surgery did not reduce the regional blood volume changes, whereas the changes were eliminated by a DC lesion at T10.
TL;DR: The result suggests that the thalamic plasticity that is seen immediately after a peripheral deafferentation is dependent upon both descending corticofugal projections and ascending trigeminothalamic projections.
Abstract: Multiple neuron ensemble recordings were obtained simultaneously from both the primary somatosensory (SI) cortex and the ventroposterior medial thalamus (VPM) before and during the combined administration of reversible inactivation of the SI cortex and a reversible subcutaneous block of peripheral trigeminal nerve fibers. This procedure was performed to quantify the contribution of descending corticofugal projections on (i) the normal organization of thalamic somatosensory receptive fields and (ii) the thalamic somatosensory plastic reorganization that immediately follows a peripheral deafferentation. Reversible inactivation of SI cortex resulted in immediate changes in receptive field properties throughout the VPM. Cortical inactivation also significantly reduced but did not completely eliminate the occurrence of VPM receptive field reorganization resulting from the reversible peripheral deafferentation. This result suggests that the thalamic plasticity that is seen immediately after a peripheral deafferentation is dependent upon both descending corticofugal projections and ascending trigeminothalamic projections.
TL;DR: Electron microscopy of areas of overlap confirmed synaptic contacts of anterogradely labeled presynaptic profiles originating in the superficial layers of the superior colliculus with retrogradely labeled postsynaptic profiles of thalamo‐amygdaloid projection neurons.
Abstract: The aim of the present study was to identify synaptic contacts from axons originating in the superior colliculus with thalamic neurons projecting to the lateral nucleus of the amygdala. Axons from the superior colliculus were traced with the anterograde tracers Phaseolus vulgaris leucoagglutinin or the biotinylated and fluorescent dextran amine "Miniruby." Thalamo-amygdaloid projection neurons were identified with the retrograde tracer Fluoro-Gold. Injections of Fluoro-Gold into the lateral nucleus of the amygdala labeled neurons in nuclei of the posterior thalamus which surround the medial geniculate body, viz. the suprageniculate nucleus, the medial division of the medial geniculate body, the posterior intralaminar nucleus, and the peripeduncular nucleus. Anterogradely labeled axons from the superior colliculus terminated in the same regions of the thalamus. Tecto-thalamic axons originating from superficial collicular layers were found predominantly in the suprageniculate nucleus, whereas axons from deep collicular layers were detected in equal density in all thalamic nuclei surrounding the medial geniculate body. Double-labeling experiments revealed an overlap of projection areas in the above-mentioned thalamic nuclei. Electron microscopy of areas of overlap confirmed synaptic contacts of anterogradely labeled presynaptic profiles originating in the superficial layers of the superior colliculus with retrogradely labeled postsynaptic profiles of thalamo-amygdaloid projection neurons. These connections may represent a subcortical pathway for visual information transfer to the amygdala.
TL;DR: 4‐Tesla functional magnetic resonance imaging (fMRI) was used to identify changes in activity in discrete regions of the human brain previously identified in animal studies to be involved in visceral control and observed neural activation, the first demonstration of human brain activity in response to visceral stimulation as measured by fMRI.
Abstract: Visceral function is essential for survival. Discreet regions of the human brain controlling visceral function have been postulated from animal studies (Cechetto and Saper [1987] J. Comp. Neurol. 262:27–45) and suspected from lethal cardiac arrythmias (Cechetto [1994] Integr. Physiol. Behv. Sci. 29:362–373). However, these visceral sites remain uncharted in the normal human brain. We used 4-Tesla functional magnetic resonance imaging (fMRI) to identify changes in activity in discrete regions of the human brain previously identified in animal studies to be involved in visceral control. Five male subjects underwent heart rate (HR) and/or blood pressure (BP) altering tests: maximal inspiration (MX), Valsalva's maneuver (VM), and isometric handgrip (HG). Increased neuronal activity was observed during MX, VM, and HG, localized in the insular cortex, in the posterior regions of the thalamus, and in the medial prefrontal cortex. To differentiate special visceral (taste) regions from general visceral (HR, BP) regions in these areas, response to gustatory stimulation was also examined; subjects were administered saline (SAL) and sucrose (SUC) solutions as gustatory stimuli. Gustatory stimulation increased activity in the ventral insular cortex at a more inferior level than the cardiopulmonary stimuli. The observed neural activation is the first demonstration of human brain activity in response to visceral stimulation as measured by fMRI. J. Comp. Neurol. 413:572–582, 1999. © 1999 Wiley-Liss, Inc.
TL;DR: This prediction is accurate when tactile stimuli are self-produced relative to when they are externally produced, and is therefore used to attenuate the somatosensory response to the former type of tactile stimulation but not the former, and supports the proposal that the cerebellum is involved in predicting the sensory consequences of movements.
Journal Article•
TL;DR: The dynamic changes of rCBF and rCMRO2 observed in children probably reflect the physiologic developmental state within anatomic areas of the brain.
Abstract: BACKGROUND AND PURPOSE: Normal values for cerebral blood flow (CBF) and metabolism in adults are well established, but not for children. Our goal, therefore, was to clarify functional developmental changes of the brain in children in relation to CBF and oxygen metabolism. METHODS: We measured regional CBF (rCBF), regional cerebral metabolic rate for oxygen (rCMRO2), and regional oxygen extraction fraction (rOEF), using positron emission tomography (PET). We performed 30 PET studies in 24 children ages 10 days to 16 years (nine boys, 15 girls), using a steady inhalation method with C15O2, 15O2, and 15CO in order to measure rCBF, rCMRO2, and rOEF, respectively. Regions of interest were set in the primary cerebral areas (sensorimotor, visual, temporal, and parietal cortex), cerebral association areas (frontal and visual association), basal ganglia (lenticular and thalamus), and posterior fossa (brain stem and cerebellar cortex). Subjects were grouped by age ( RESULTS: rCBF and rCMRO2 were lower in the neonatal period than in older children and adults, and increased significantly during early childhood. rCBF was higher as compared with adults, peaking around age 7, whereas rCMRO2 was relatively high, with the last area to increase being the frontal association cortex. Both rCBF and rCMRO2 reached adult values during adolescence. No difference in rCBF was observed between the basal ganglia and the primary cerebral cortex; however, it was prominent in the occipital lobe in every age bracket. No significant changes in rOEF were found during childhood. CONCLUSION: The dynamic changes of rCBF and rCMRO2 observed in children probably reflect the physiologic developmental state within anatomic areas of the brain.
TL;DR: A bilateral activation of the lateral pain system as well as involvement of the medial pain system during dynamic mechanical allodynia in patients with mononeuropathy is revealed.
Abstract: The objective of this study was to investigate the central processing of dynamic mechanical allodynia in patients with mononeuropathy. Regional cerebral blood flow, as an indicator of neuronal activity, was measured with positron emission tomography. Paired comparisons were made between three different states; rest, allodynia during brushing the painful skin area, and brushing of the homologous contralateral area. Bilateral activations were observed in the primary somatosensory cortex (S1) and the secondary somatosensory cortex (S2) during allodynia compared to rest. The S1 activation contralateral to the site of the stimulus was more expressed during allodynia than during innocuous touch. Significant activations of the contralateral posterior parietal cortex, the periaqueductal gray (PAG), the thalamus bilaterally and motor areas were also observed in the allodynic state compared to both non-allodynic states. In the anterior cingulate cortex (ACC) there was only a suggested activation when the allodynic state was compared with the non-allodynic states. In order to account for the individual variability in the intensity of allodynia and ongoing spontaneous pain, rCBF was regressed on the individually reported pain intensity, and significant covariations were observed in the ACC and the right anterior insula. Significantly decreased regional blood flow was observed bilaterally in the medial and lateral temporal lobe as well as in the occipital and posterior cingulate cortices when the allodynic state was compared to the non-painful conditions. This finding is consistent with previous studies suggesting attentional modulation and a central coping strategy for known and expected painful stimuli. Involvement of the medial pain system has previously been reported in patients with mononeuropathy during ongoing spontaneous pain. This study reveals a bilateral activation of the lateral pain system as well as involvement of the medial pain system during dynamic mechanical allodynia in patients with mononeuropathy.
TL;DR: It was demonstrated that the mid‐dorsolateral frontal cortex and its medial extension is the origin of a specific fiber pathway, running posteriorly as part of the cingulum bundle, and terminating mainly in the retrosplenial area 30 and the posterior presubiculum.
Abstract: The present study investigated the origin, course, and terminations of the association fiber system linking the frontal cortex with the hippocampal system by means of the cingulum bundle. Injections of tritiated amino acids were placed within individual cytoarchitectonic areas of the frontal cortex in the rhesus monkey. It was demonstrated that the mid-dorsolateral frontal cortex (areas 46, 9/46, and 9) and its medial extension (medial areas 9 and 9/32) is the origin of a specific fiber pathway, running posteriorly as part of the cingulum bundle, and terminating mainly in the retrosplenial area 30 and the posterior presubiculum. This fiber bundle therefore provides the anatomical substrate of a functional interaction between the mid-dorsolateral frontal cortex and the hippocampal memory system for the monitoring of information within working memory.
TL;DR: There is a mismatch between the effector muscle for a thalamic cell and the muscles with EMG correlated with activity of that cell during dystonia, which may result from the reorganization of sensory maps and may contribute to the simultaneous activation of multiple muscles observed in dySTONia.
Abstract: Indirect evidence suggests that the thalamus contributes to abnormal movements occurring in patients with dystonia (dystonia patients). The present study tested the hypothesis that thalamic activit...
TL;DR: The aim of this study was to establish the safety of performing fMR imaging in patients with thalamic deep brain stimulators and to determine the value of fMR Imaging in detecting cortical and subcortical activity during stimulation.
Abstract: The utility of functional magnetic resonance (fMR) imaging in patients with implanted thalamic electrodes has not yet been determined. The aim of this study was to establish the safety of performing fMR imaging in patients with thalamic deep brain stimulators and to determine the value of fMR imaging in detecting cortical and subcortical activity during stimulation. Functional MR imaging was performed in three patients suffering from chronic pain and two patients with essential tremor. Two of the three patients with pain had undergone electrode implantation in the thalamic sensory ventralis caudalis (Vc) nucleus and the other had undergone electrode implantation in both the Vc and the periventricular gray (PVG) matter. Patients with tremor underwent electrode implantation in the ventralis intermedius (Vim) nucleus. Functional MR imaging was performed during stimulation by using a pulse generator connected to a transcutaneous extension lead. Clinically, Vc stimulation evoked paresthesias in the contralateral body, PVG stimulation evoked a sensation of diffuse internal body warmth, and Vim stimulation caused tremor arrest. Functional images were acquired using a 1.5-tesla MR imaging system. The Vc stimulation at intensities provoking paresthesias resulted in activation of the primary somatosensory cortex (SI). Stimulation at subthreshold intensities failed to activate the SI. Additional stimulation-coupled activation was observed in the thalamus, the secondary somatosensory cortex (SII), and the insula. In contrast, stimulation of the PVG electrode did not evoke paresthesias or activate the SI, but resulted in medial thalamic and cingulate cortex activation. Stimulation in the Vim resulted in thalamic, basal ganglia, and SI activation. An evaluation of the safety of the procedure indicated that significant current could be induced within the electrode if a faulty connecting cable (defective insulation) came in contact with the patient. Simple precautions, such as inspection of wires for fraying and prevention of their contact with the patient, enabled the procedure to be conducted safely. Clinical safety was further corroborated by performing 86 MR studies in patients in whom electrodes had been implanted with no adverse clinical effects. This is the first report of the use of fMR imaging during stimulation with implanted thalamic electrodes. The authors' findings demonstrate that fMR imaging can safely detect the activation of cortical and subcortical neuronal pathways during stimulation and that stimulation does not interfere with imaging. This approach offers great potential for understanding the mechanisms of action of deep brain stimulation and those underlying pain and tremor generation.
TL;DR: As a corollary, orexin A may be released into the ventricles and interact with neurons in distant targets, in addition to influencing the activity of neurons with which ORX-LI axons make synaptic contacts.
TL;DR: Overall, in vitro data indicate that reported regional differences in the in vivo responses of MGV and MGD cells to auditory stimuli are not well correlated with major differences in intrinsic membrane features or synaptic responses between cell types.
Abstract: Anatomic, intrinsic, and synaptic properties of dorsal and ventral division neurons in rat medial geniculate body. Presently little is known about what basic synaptic and cellular mechanisms are em...
TL;DR: Striatal interneurons immunoreactive for somatostatin, parvalbumin and choline acetyltransferase, but not those containing calretinin, receive strong inputs from the centromedian nucleus in monkeys.
TL;DR: For instance, the authors showed that microinjections of the cannabinoid agonist WIN55,212-2 (5 microg) into 17 different brain regions significantly increased tail-flick latencies when injected into the amygdala, the lateral posterior and submedius regions of the thalamus, the superior colliculus and the noradrenergic A5 region.