Advances in transsynaptic retrograde degeneration of optic neuropathy / 中华眼底病杂志

Transsynaptic retrograde degeneration of optic neuropathy (TRDON) refers to the degeneration and/or apoptosis of presynaptic neurons (retinal ganglion cells) caused by damage to the lateral geniculate body and post-geniculate visual pathway. At present, the pathogenesis of TRDON is secondary apoptosis of P β-type retinal ganglion cells, resulting in the atrophy of optic tract, thinning of the retinal nerve fiber layer and retinal ganglion cell layer thickness and declining of retinal microvascular density, which are consistent with the visual field defect attributed to the primary disease. Of which, the thinning of the retinal ganglion cell layer thickness is considered as the characteristic of TRDON. Now, there is little understanding and related research on TRDON in China. Clinicians should pay attention to the characteristics and severity, occurrence time and location of the above structural changes in these patients through optical coherence tomography, and monitor the activity and progress of the lesions, so as to determine the cut-off point for drug intervention and the drug targets for developing new treatment methods, and bring benefits for patients in partial visual function recovery and disability reduction.

Three-Dimensional Heterogeneity of Cerebellar Interposed Nucleus-Recipient Zones in the Thalamic Nuclei / 神经科学通报·英文版

The cerebellum is conceptualized as a processor of complex movements and is also endowed with roles in cognitive and emotional behaviors. Although the axons of deep cerebellar nuclei are known to project to primary thalamic nuclei, macroscopic investigation of the characteristics of these projections, such as the spatial distribution of recipient zones, is lacking. Here, we studied the output of the cerebellar interposed nucleus (IpN) to the ventrolateral (VL) and centrolateral (CL) thalamic nuclei using electrophysiological recording in vivo and trans-synaptic viral tracing. We found that IpN stimulation induced mono-synaptic evoked potentials (EPs) in the VL but not the CL region. Furthermore, both the EPs induced by the IpN and the innervation of IpN projections displayed substantial heterogeneity across the VL region in three-dimensional space. These findings indicate that the recipient zones of IpN inputs vary between and within thalamic nuclei and may differentially control thalamo-cortical networks.

Three-Dimensional Heterogeneity of Cerebellar Interposed Nucleus-Recipient Zones in the Thalamic Nuclei / 神经科学通报·英文版

The cerebellum is conceptualized as a processor of complex movements and is also endowed with roles in cognitive and emotional behaviors. Although the axons of deep cerebellar nuclei are known to project to primary thalamic nuclei, macroscopic investigation of the characteristics of these projections, such as the spatial distribution of recipient zones, is lacking. Here, we studied the output of the cerebellar interposed nucleus (IpN) to the ventrolateral (VL) and centrolateral (CL) thalamic nuclei using electrophysiological recording in vivo and trans-synaptic viral tracing. We found that IpN stimulation induced mono-synaptic evoked potentials (EPs) in the VL but not the CL region. Furthermore, both the EPs induced by the IpN and the innervation of IpN projections displayed substantial heterogeneity across the VL region in three-dimensional space. These findings indicate that the recipient zones of IpN inputs vary between and within thalamic nuclei and may differentially control thalamo-cortical networks.

Role of SARS-CoV-2 neurotropism and neuroinvasion in COVID-19 patients disease severity / Papel del neurotropismo y neuroinvasión de SARS-CoV-2 en la gravedad de los pacientes con COVID-19

Abstract The disease caused by the new SARS-CoV-2 coronavirus (COVID-19) spread rapidly from China to the entire world. Approximately one third of SARS-CoV-2-infected patients have neurological disorders, especially those classified as severe cases and that require mechanical ventilation. On the other hand, almost nine out of 10 patients admitted to an Intensive Care Unit could not breathe spontaneously, thus requiring invasive and non-invasive ventilatory support. So far, whether early neurological disorders such as hyposmia or anosmia, dysgeusia or ageusia, headache and vertigo are significant in the progression to the severe form of the disease or whether they are related to entry to the central nervous system via peripheral nerves has not been determined. Considering the great similarity between SARS-CoV and SARS-CoV-2, and that the severity of the condition that leads to death cannot be explained solely by lung involvement, it is important to determine whether SARS-CoV-2 potential invasion to the central nervous system is partially responsible for the severe respiratory component observed in patients with COVID-19.

Resumen La enfermedad (COVID-19) producida por el nuevo coronavirus SARS-CoV-2 se extendió rápidamente desde China a todo el mundo. Aproximadamente una tercera parte de los pacientes infectados de SARS-CoV-2 presenta alteraciones neurológicas, con mayor frecuencia los clasificados como graves que requirieron ventilación mecánica. Por otro lado, casi nueve de cada 10 pacientes admitidos en una unidad de cuidados intensivos no podían respirar espontáneamente, por lo que ameritaron apoyo ventilatorio invasivo y no invasivo. Hasta el momento no se ha determinado si las alteraciones neurológicas tempranas como la hiposmia o anosmia, disgeusia o ageusia, cefalea y vértigo son significativas en la progresión a la forma grave de la enfermedad y se relacionan con la entrada al sistema nervioso central a través de los nervios periféricos. Considerando la gran similitud entre SARS-CoV y SARS-CoV-2 y que la severidad del cuadro que conduce a la muerte no puede ser explicado únicamente por la afección pulmonar, es importante determinar si la invasión potencial del SARS-CoV-2 al sistema nervioso central es parcialmente responsable del componente respiratorio severo que presentan los pacientes con COVID-19.

Trans-synaptic Neural Circuit-Tracing with Neurotropic Viruses / 神经科学通报·英文版

A central objective in deciphering the nervous system in health and disease is to define the connections of neurons. The propensity of neurotropic viruses to spread among synaptically-linked neurons makes them ideal for mapping neural circuits. So far, several classes of viral neuronal tracers have become available and provide a powerful toolbox for delineating neural networks. In this paper, we review the recent developments of neurotropic viral tracers and highlight their unique properties in revealing patterns of neuronal connections.

Cortical Organization of Centrifugal Afferents to the Olfactory Bulb: Mono- and Trans-synaptic Tracing with Recombinant Neurotropic Viral Tracers / 神经科学通报·英文版

Sensory processing is strongly modulated by different brain and behavioral states, and this is based on the top-down modulation. In the olfactory system, local neural circuits in the olfactory bulb (OB) are innervated by centrifugal afferents in order to regulate the processing of olfactory information in the OB under different behavioral states. The purpose of the present study was to explore the organization of neural networks in olfactory-related cortices and modulatory nuclei that give rise to direct and indirect innervations to the glomerular layer (GL) of the OB at the whole-brain scale. Injection of different recombinant attenuated neurotropic viruses into the GL showed that it received direct inputs from each layer in the OB, centrifugal inputs from the ipsilateralanterior olfactory nucleus (AON), anterior piriform cortex (Pir), and horizontal limb of diagonal band of Broca (HDB), and various indirect inputs from bilateral cortical neurons in the AON, Pir, amygdala, entorhinal cortex, hippocampus, HDB, dorsal raphe, median raphe and locus coeruleus. These results provide a circuitry basis that will help further understand the mechanism by which olfactory information-processing in the OB is regulated.

Whole-Brain Mapping of Direct Inputs to and Axonal Projections from GABAergic Neurons in the Parafacial Zone / 神经科学通报·英文版

The GABAergic neurons in the parafacial zone (PZ) play an important role in sleep-wake regulation and have been identified as part of a sleep-promoting center in the brainstem, but the long-range connections mediating this function remain poorly characterized. Here, we performed whole-brain mapping of both the inputs and outputs of the GABAergic neurons in the PZ of the mouse brain. We used the modified rabies virus EnvA-ΔG-DsRed combined with a Cre/loxP gene-expression strategy to map the direct monosynaptic inputs to the GABAergic neurons in the PZ, and found that they receive inputs mainly from the hypothalamic area, zona incerta, and parasubthalamic nucleus in the hypothalamus; the substantia nigra, pars reticulata and deep mesencephalic nucleus in the midbrain; and the intermediate reticular nucleus and medial vestibular nucleus (parvocellular part) in the pons and medulla. We also mapped the axonal projections of the PZ GABAergic neurons with adeno-associated virus, and defined the reciprocal connections of the PZ GABAergic neurons with their input and output nuclei. The newly-found inputs and outputs of the PZ were also listed compared with the literature. This cell-type-specific neuronal whole-brain mapping of the PZ GABAergic neurons may reveal the circuits underlying various functions such as sleep-wake regulation.

Exofocal Anterograde Transsynaptic Neuronal Death in the Globus Pallidus: Two Case Reports

BACKGROUND: Exofocal neuronal death in the substantia nigra (SN) is a well-known form of anterograde transsynaptic cell death. Exofocal neuronal death could theoretically also occur in the globus pallidus (GP) after striatal injury. CASE REPORT: Case 1. A 70-year-old woman visited the emergency room because of decreased mentality. On admission, blood-gas analysis indicated that her oxygen tension was 69.1 mm Hg. The caudate nucleus, putamen, and temporooccipital cortex on both sides of the brain exhibited high-intensity diffusion-weighted magnetic resonance imaging (MRI) signals. At 10 days after admission, new high-intensity signals had developed in the SN and GP on both sides. Case 2. A 48-year-old man visited the emergency room because of right-sided weakness. Lesions were noted in the left caudate nucleus and putamen. At 4 days after admission, newly developed high-intensity MRI signals were observed in the left SN and GP. CONCLUSIONS: Exofocal neuronal death can occur in the GP as well as in the SN; these findings need to be clearly distinguished from those of recurrent ischemic injuries, such as recurrent stroke.

Degeneração olivar hipertrófica após ressecção de metástase cerebelar: relato de caso e revisão da literatura / Hypertrophic olivary degeneration secondary to resection of cerebellar metastasis: case report and literature review

Degeneração olivar hipertrófica resulta de lesão no circuito formado pelos núcleos denteado, rubro e olivar inferior (triângulo de Guillain e Mollaret). Pode ser secundária a hemorragias, trauma, neoplasias, entre outras causas que lesem estruturas desse circuito. Destaca-se a relevância deste relato de caso por apresentar um caso de degeneração olivar hipertrófica bilateral, secundária a insulto em ambos os núcleos denteados após ressecção de metástase.

Hypertrophic olivary degeneration represents the results of a lesionthat damages the neuronal connections between the dentate nucleus of the cerebellum, the red nucleus, and the inferior olivary nucleus (Guillain Mollaret triangle). This entity can occur secondary to hemorrhage, trauma, neoplasm and other causes that candamage structures of this pathway. This is an important case report because of its description of a bilateral hypertrophic olivary degeneration, secondary to injuries in both dentate nucleous after metastatic resection.