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lateral geniculate nucleus [keywords]
- Lateral Geniculate Lesions Causing Reversible Blindness in a Pre-eclamptic Patient With a Variant of Posterior Reversible Encephalopathy Syndrome. [JOURNAL ARTICLE]
- J Neuroophthalmol 2014 Apr 15.
: Bilateral lateral geniculate nucleus (LGN) injury is a rare cause of vision loss. We describe a patient with pre-eclampsia who developed profound but reversible bilateral vision loss, bilateral serous retinal detachments, and magnetic resonance imaging signs of a variant of posterior reversible encephalopathy syndrome (PRES) that affected both LGNs and spared the retrogeniculate pathways. We provide evidence that the visual loss was not from the chorioretinal lesions but from the LGN lesions. The concurrence of PRES and lesions attributed to choroidal hypoperfusion provides support for the notion that vasoconstriction also underlies the pathogenesis of PRES.
- Repetitive and retinotopically restricted activation of the dorsal lateral geniculate nucleus with optogenetics. [Journal Article]
- PLoS One 2014; 9(4):e94633.
Optogenetics allows the control of cellular activity using focused delivery of light pulses. In neuroscience, optogenetic protocols have been shown to efficiently inhibit or stimulate neuronal activity with a high temporal resolution. Among the technical challenges associated with the use of optogenetics, one is the ability to target a spatially specific population of neurons in a given brain structure. To address this issue, we developed a side-illuminating optical fiber capable of delivering light to specific sites in a target nucleus with added flexibility through rotation and translation of the fiber and by varying the output light power. The designed optical fiber was tested in vivo in visual structures of ChR2-expressing transgenic mice. To assess the spatial extent of neuronal activity modulation, we took advantage of the hallmark of the visual system: its retinotopic organization. Indeed, the relative position of ganglion cells in the retina is transposed in the cellular topography of both the dorsal lateral geniculate nucleus (LGN) in the thalamus and the primary visual cortex (V1). The optical fiber was inserted in the LGN and by rotating it with a motor, it was possible to sequentially activate different neuronal populations within this structure. The activation of V1 neurons by LGN projections was recorded using intrinsic optical imaging. Increasing light intensity (from 1.4 to 8.9 mW/mm2) led to increasing activation surfaces in V1. Optogenetic stimulation of the LGN at different translational and rotational positions was associated with different activation maps in V1. The position and/or orientation of the fiber inevitably varied across experiments, thus limiting the capacity to pool data. With the optogenetic design presented here, we demonstrate for the first time a transitory and spatially-concise activation of a deep neuronal structure. The optogenetic design presented here thus opens a promising avenue for studying the function of deep brain structures.
- An Investigation of Lateral Geniculate Nucleus Volume in Patients with Primary Open-angle Glaucoma using 7 Tesla Magnetic Resonance Imaging. [JOURNAL ARTICLE]
- Invest Ophthalmol Vis Sci 2014 Apr 10.
Purpose:To investigate lateral geniculate nucleus (LGN) volume of primary open-angle glaucoma (POAG) patients compared with age and gender-matched controls using ultra-high field 7.0T magnetic resonance imaging (MRI). Methods:Methods: The study included 18 patients with POAG and 18 age-, and sex-matched healthy volunteers. All subjects underwent imaging on a high-resolution 7.0-T MR imaging system. Bilateral LGNs were identified, manually delineated, and LGN volumes were compared. Peripapillary retinal nerve fiber layer (pRNFL) thickness, optic nerve head parameters including optic disc size, rim area, and cup-to-disc ratio and combined thickness of the ganglion cell layer and inner plexus layer (GC-IPL) were measured by Cirrus high-definition optical coherence tomography (OCT). Correlations between OCT parameters and LGN volume were investigated. Results: Mean LGN volumes were significantly smaller in the POAG group than that in the control group (Right, glaucoma 83.97 ± 26.65 mm3 vs. control 106.12 ± 24.32 mm3 ; Left, glaucoma 65.12 ± 29.41 mm3 vs. control 92.70 ± 24.42 mm3 , both p<0.05). In the POAG group, average GC-IPL thickness was correlated with contra-lateral LGN volume (right LGN: r=0.605, p=0.008; left LGN r=0.471, p=0.049). The correlation for right LGN volume remained significant after correction for multiple comparisons. However, there was no correlation between LGN volume and average pRNFL thickness or optic disc parameters in the POAG group. Conclusions: On high-resolution 7.0T MRI, LGN volumes in POAG patients are significantly smaller than those of healthy subjects. Furthermore, in patients, LGN volume was found to be significantly correlated with GC-IPL thickness of the contralateral eye.
- Central pontine and extrapontine myelinolysis: the great masquerader-an autopsy case report. [Journal Article]
- Case Rep Neurol Med 2014.:745347.
Central pontine myelinolysis is a demyelinating disorder characterized by the loss of myelin in the center of the basis pontis usually caused by rapid correction of chronic hyponatremia. The clinical features vary depending on the extent of involvement. Demyelination can occur outside the pons as well and diagnosis can be challenging if both pontine and extrapontine areas are involved. We herein report a case of myelinolysis involving pons, lateral geniculate bodies, subependymal region, and spinal cord. To the best of our knowledge, this case represents the second case of spinal cord involvement in osmotic demyelination syndrome and the first case of involvement of thoracic region of spinal cord.
- Antidromic latency of magnocellular, parvocellular, and koniocellular (Blue-ON) geniculocortical relay cells in marmosets. [JOURNAL ARTICLE]
- Vis Neurosci 2014 Apr 7.:1-11.
We studied the functional connectivity of cells in the lateral geniculate nucleus (LGN) with the primary visual cortex (V1) in anesthetized marmosets (Callithrix jacchus). The LGN sends signals to V1 along parallel visual pathways called parvocellular (P), magnocellular (M), and koniocellular (K). To better understand how these pathways provide inputs to V1, we antidromically activated relay cells in the LGN by electrically stimulating V1 and measuring the conduction latencies of P (n = 7), M (n = 14), and the "Blue-ON" (n = 5) subgroup of K cells (K-BON cells). We found that the antidromic latencies of K-BON cells were similar to those of P cells. We also measured the response latencies to high contrast visual stimuli for a subset of cells. We found the LGN cells that have the shortest latency of response to visual stimulation also have the shortest antidromic latencies. We conclude that Blue color signals are transmitted directly to V1 from the LGN by K-BON cells.
- Iron deposits in post-mortem brains of patients with neurodegenerative and cerebrovascular diseases: a semi-quantitative 7.0 T magnetic resonance imaging study. [JOURNAL ARTICLE]
- Eur J Neurol 2014 Apr 2.
Accumulation of iron (Fe) is often detected in brains of people suffering from neurodegenerative diseases. However, no studies have compared the Fe load between these disease entities. The present study investigates by T2*-weighted gradient-echo 7.0 T magnetic resonance imaging (MRI) the Fe content in post-mortem brains with different neurodegenerative and cerebrovascular diseases.One hundred and fifty-two post-mortem brains, composed of 46 with Alzheimer's disease (AD), 37 with frontotemporal lobar degeneration (FTLD), 11 with amyotrophic lateral sclerosis, 13 with Lewy body disease, 14 with progressive supranuclear palsy, 16 with vascular dementia (VaD) and 15 controls without a brain disease, were examined. The Fe load was determined semi-quantitatively on T2*-weighted MRI serial brain sections in the claustrum, caudate nucleus, putamen, globus pallidus, thalamus, subthalamic nucleus, hippocampus, mamillary body, lateral geniculate body, red nucleus, substantia nigra and dentate nucleus. The disease diagnosis was made on subsequent neuropathological examination.The Fe load was significantly increased in the claustrum, caudate nucleus and putamen of FTLD brains and to a lesser degree in the globus pallidus, thalamus and subthalamic nucleus. In the other neurodegenerative diseases no Fe accumulation was observed, except for a mild increase in the caudate nucleus of AD brains. In VaD brains no Fe increase was detected.Only FTLD displays a significant Fe load, suggesting that impaired Fe homeostasis plays an important role in the pathogenesis of this heterogeneous disease entity.
- Synapse elimination and learning rules co-regulated by MHC class I H2-D(b.) [JOURNAL ARTICLE]
- Nature 2014 Mar 30.
The formation of precise connections between retina and lateral geniculate nucleus (LGN) involves the activity-dependent elimination of some synapses, with strengthening and retention of others. Here we show that the major histocompatibility complex (MHC) class I molecule H2-D(b) is necessary and sufficient for synapse elimination in the retinogeniculate system. In mice lacking both H2-K(b) and H2-D(b) (K(b)D(b)(-/-)), despite intact retinal activity and basal synaptic transmission, the developmentally regulated decrease in functional convergence of retinal ganglion cell synaptic inputs to LGN neurons fails and eye-specific layers do not form. Neuronal expression of just H2-D(b) in K(b)D(b)(-/-) mice rescues both synapse elimination and eye-specific segregation despite a compromised immune system. When patterns of stimulation mimicking endogenous retinal waves are used to probe synaptic learning rules at retinogeniculate synapses, long-term potentiation (LTP) is intact but long-term depression (LTD) is impaired in K(b)D(b)(-/-) mice. This change is due to an increase in Ca(2+)-permeable AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors. Restoring H2-D(b) to K(b)D(b)(-/-) neurons renders AMPA receptors Ca(2+) impermeable and rescues LTD. These observations reveal an MHC-class-I-mediated link between developmental synapse pruning and balanced synaptic learning rules enabling both LTD and LTP, and demonstrate a direct requirement for H2-D(b) in functional and structural synapse pruning in CNS neurons.
- Case Report: Practicability of functionally based tractography of the optic radiation during presurgical epilepsy work up. [JOURNAL ARTICLE]
- Neurosci Lett 2014 Mar 29.:56-61.
Pre-operative tractography of the optic radiation (OR) has been advised to assess the risk for postoperative visual field deficit (VFD) in certain candidates for resective epilepsy surgery. Diffusion tensor imaging (DTI) tractography relies on a precise anatomical determination of start and target regions of interest (ROIs), such as the lateral geniculate nucleus (LGN) and the primary visual cortex (V1). The post-chiasmal visual pathway and V1 show considerable inter-individual variability, and in epilepsy patients parenchymatous lesions might further complicate this matter. A functionally based tractography (FBT) seems beneficial for precise OR identification. We assessed practicability of FBT for OR identification in a patient with occipital lobe epilepsy due to a temporo-occipital maldevelopmental tumor. The MRI protocol at 3T included a T1-weighted sagittal 3D scan, a T2-weighted axial 2D scan and a DTI scan using an echo planar spin echo sequence. ROIs for fiber tracking of OR (LGN & V1) were determined with T2*-weighted fMRI-based retinotopic assessment. After DTI pre-processing and fiber tracking, paths with similar properties were combined in clusters for visual presentation and OR localization. Retinotopic phase maps allowed for the identification of V1 and LGN for a precise DTI-based reconstruction of OR, which was distant to the patient's tumor. Location and structure of ORs were comparable in each hemisphere. FBT could thus influence the human research of the extrastriate visual pathway and the risk management of post-operative VFD in epilepsy surgery.
- An Unusual Cause of Blindness: Infarction in the Bilateral Lateral Geniculate Bodies. [JOURNAL ARTICLE]
- J Stroke Cerebrovasc Dis 2014 Mar 25.
A 10-year-old girl presented with acute blindness after a severe episode of febrile diarrhea. Magnetic resonance images were consistent with the diagnosis of infarction in the bilateral lateral geniculate bodies.
- Effects of intracerebroventricular corticotropin releasing factor on sensory-evoked responses in the rat visual thalamus. [JOURNAL ARTICLE]
- Brain Res 2014 Mar 22.
Corticotropin releasing factor (CRF) coordinates the brain׳s responses to stress. Recent evidence suggests that CRF-mediated activation of the locus coeruleus-norepinephrine (LC-NE) system contributes to alterations in sensory signal processing during stress. However, it remains unclear whether these actions are dependent upon the degree of CRF release. Using intracerebroventricular (ICV) infusions, we examine the dose-dependent actions of CRF on sensory-evoked discharges of neurons in the dorsal lateral geniculate nucleus of the thalamus (dLGN). The LGN is the primary relay for visual signals from retina to cortex, receiving noradrenergic modulation from the LC. In vivo extracellular recording in anesthetized rats was used to monitor single dLGN neuron responses to light flashes at three different stimulus intensities before and after administration of CRF (0.1, 0.3, 1.0, 3.0 or 10.0μg). CRF produced three main effects on dLGN stimulus evoked activity: (1) increased magnitude of sensory evoked discharges at moderate doses, (2) decreased response latency, and (3) dose-dependent increases in the number of cells responding to a previously sub-threshold (low intensity) stimulus. These modulatory actions were blocked or attenuated by intra-LC infusion of a CRF antagonist prior to ICV CRF administration. Moreover, intra-LC administration of CRF (10ng) mimicked the facilitating effects of moderate doses of ICV CRF on dLGN neuron responsiveness to light stimuli. These findings suggest that stressor-induced changes in sensory signal processing cannot be defined in terms of a singular modulatory effect, but rather are multi-dimensional and dictated by variable degrees of activation of the CRF-LC-NE system.