Dysregulation of the dopamine system is a well-established component of schizophrenia pathophysiology, with regional differences in dopamine targets thought to shape disease symptoms. Increased presynaptic striatal dopamine synthesis and release are among the most consistent findings in patients. These alterations seem to occur early in the disease and are also observed in prodromal subjects that are at clinically high risk for developing schizophrenia. This article is a commentary on the study by Schifani and colleagues (Brain 141(7):2213-2224, 2018) which found the first direct evidence for disrupted prefronto-cortical dopamine stress regulation in schizophrenia.

Gomes FV and Grace AA: Cortical dopamine dysregulation in schizophrenia and its link to stress. Brain 141(7): 1897-1899 (2018).


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Abstract: “Heart valve disease (HVD) is a complex entity made by different pathological processes that ultimately lead to the abnormal structure and disorganization of extracellular matrix proteins resulting to dysfunction of the leaflets. At its final evolutionary step, treatments are limited to the percutaneous or surgical valve replacement, whatever the original cause of the degeneration. Understanding early molecular mechanisms that regulate valve interstitial cells remodeling and disease progression is challenging and could pave the way for future drugs aiming to prevent and/or reverse the process. Some valve degenerative processes such as the carcinoid heart disease, drug-induced valvulopathy and degenerative mitral valve disease in small-breed dogs are clearly linked to serotonin. The carcinoid heart is typically characterized by a right-sided valve dysfunction, observed in patients with carcinoid tumors developed from serotonin-producing gut enterochromaffin cells. Fenfluramine or ergot derivatives were linked to mitral and aortic valve dysfunction and share in common the pharmacological property of being 5-HT2B receptor agonists. Finally, some small-breed dogs, such as the Cavalier King Charles Spaniel are highly prone to degenerative mitral valve disease with a prevalence of 40% at 4 years-old, 70% at 7 years-old and 100% in 10-year-old animals. This degeneration has been linked to high serum serotonin, 5-HT2B receptor overexpression and SERT downregulation. Through the comprehension of serotonergic mechanisms involved into these specific situations, new therapeutic approaches could be extended to HVD in general.” Evidence also exists for pergolide and cabergoline being associated with a higher risk of cardiac valve regurgitation and pramipexole and cabergoline being associated with a higher risk of heart failure in patients with Parkinson’s disease. “This review summarizes clinical and molecular mechanisms linking the serotonergic system and heart valve disease, opening the way for future pharmacological research in the field.”

Ayme-Dietrich E, Lawson R, Da-Silva S, Mazzucotelli JP, Monassier L: Serotonin contribution to cardiac valve degeneration: new insights for novel therapies? Pharmacol. Res.  [Epub ahead of print, Sept. 9, 2018;  pii: S1043-6618(18)30587-5. doi: 10.1016/j.phrs.2018.09.009].


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Abstract: “Strong evidence has emerged recently for the concept that herpes simplex virus type 1 (HSV1) is a major risk for Alzheimer’s disease. This concept proposes that latent HSV1 in brain of carriers of the type 4 allele of the apolipoprotein E gene (APOE-ε4) is reactivated intermittently by events such as immunosuppression, peripheral infection, and inflammation, the consequent damage accumulating, and culminating eventually in the development of Alzheimer’s. Population data to investigate this epidemiologically, e.g., to find if subjects treated with antivirals might be protected from developing dementia—are available in Taiwan, from the National Health Insurance Research Database, in which 99.9% of the population has been enrolled. This is being extensively mined for information on microbial infections and disease. Three publications have now appeared describing data on the development of senile dementia, and the treatment of those with marked overt signs of disease caused by varicella zoster virus (VZV), or by HSV. The striking results show that the risk of senile dementia is much greater in those who are HSV-seropositive than in seronegative subjects, and that antiviral treatment causes a dramatic decrease in number of subjects who later develop senile dementia. It should be stressed that these results apply only to those with severe cases of HSV1 or VZV infection, but when considered with the over 150 publications that strongly support an HSV1 role in Alzheimer’s, they greatly justify usage of antiherpes antivirals to treat Alzheimer’s. ….. Three indirectly relevant studies deal respectively with schizophrenia, relating to antiviral treatment to target HSV1, with the likelihood that HSV1 is a cause of fibromyalgia, and with fibromyalgia being associated with later development of senile dementia. Studies on the link between epilepsy, Alzheimer’s and herpes simplex encephalitis (HSE) are described also, as are the possible roles of APOE-ε4, HHV6 and HSV1 in epilepsy.”

Itzhaki RF: Corroboration of a Major Role for Herpes Simplex Virus Type 1 in Alzheimer’s Disease. Frontiers in Aging Neurosci., 19 October 2018 | https://doi.org/10.3389/fnagi.2018.00324


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Summary:  Light exerts a range of powerful biological effects beyond image vision, including effects on mood and learning. While the source of photic information affecting mood and cognitive functions is well established, via intrinsically photosensitive retinal ganglion cells (ipRGCs), the central mediators are unknown. Here, Fernandez and colleagues show that ipRGCs projections to the suprachiasmatic nucleus mediate the effects of light on learning, independently of the suprachiasmatic nucleus pacemaker function. However, mood regulation by light requires a suprachiasmatic nucleus-independent pathway linking ipRGCs to a previously unrecognized thalamic region, termed perihabenular nucleus. The perihabenular nucleus is integrated in a distinct circuitry with mood-regulating centers and is both necessary and sufficient for driving the effects of light on affective behavior. “Together, these results provide new insights into the neural basis required for light to influence mood and learning.”

Fernandez DC, Fogerson PM, Lazzerini Ospri L, Thomsen MB et al: Light Affects Mood and Learning through Distinct Retina-Brain Pathways. Cell 175(1): 71-84 (2018).


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“…Immune cells normally pounce on intruding bacteria and viruses. But in multiple sclerosis (MS), immune cells target the nervous system instead. Now, researchers may have pinpointed a long-sought molecule called a self-antigen that provokes these attacks, pointing a way toward potential new treatments.”


Specifically, guanosine diphosphate (GDP)-l-fucose synthase has been found to be an autoantigen that is recognized by cerebrospinal fluid-infiltrating CD4+ T cells from HLA-DRB3*-positive patients. Significant associations were found between reactivity to GDP-l-fucose synthase peptides and DRB3*02:02 expression, along with reactivity against an immunodominant myelin basic protein peptide. “These results, coupled with the cross-recognition of homologous peptides from gut microbiota, suggest a possible role of this antigen as an inducer or driver of pathogenic autoimmune responses in multiple sclerosis.”

Planas R, Santos R, Tomas-Ojer P, Cruciani C, Lutterotti A, Faigle W, Schaeren-Wiemers N, Espejo C, Eixarch H, Pinilla C, Martin R and Sospedra M: GDP-l-fucose synthase is a CD4+ T cell-specific autoantigen in DRB3*02:02 patients with multiple sclerosis. Science Transl. Med. 10(462). pii: eaat4301. doi: 10.1126/scitranslmed.aat4301; Oct. 10, 2018.


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Abstract: “Persistence is central to outcomes across a range of domains: the harder you try, the further you get. Yet relatively little is known about the developmental origins of persistence. Here, (Lucca and Sommerville) highlight key reasons for a surge of interest in persistence in infancy and early childhood.”

Lucca K and Sommerville JA: the Little Engine That Can: Infants’ Persistence Matters. Trends Cognitive Sci. [Epub ahead of print, August 16, 2018; pii: S1364-6613(18)30174-8. doi: 10.1016/j.tics.2018.07.012].


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Abstract: “Some research suggests that 40% of people in the vegetative state are misdiagnosed. This review investigates the frequency, nature and causes of reported misdiagnosis of patients in the vegetative state, focusing on the nature of the error. It is a systematic review of all relevant literature, using references from key papers identified. The data are summarized in tables. Five clinical studies of the rate of misdiagnosis in practice were identified, encompassing 236 patients in the vegetative state of whom 80 (34%) were reclassified as having some awareness, often minimal. The studies often included patients in the recovery phase after acute injury, and were poorly reported. Five systematic reviews of signs and technologically based neurophysiological tests were identified, and they showed that most studies were small, lacked accurate or important details, and were subject to bias. Studies were not replicated. Many signs and tests did not differ between people in the vegetative state and in the minimally conscious state, and those that did were unable to diagnose an individual patient. The few single case reports suggest that failure to ensure an accurate diagnosis of the underlying neurological damage and dysfunction could, rarely, lead to significant misdiagnosis usually in patients who had brain-stem damage with little thalamic or cortical damage. Significant misdiagnosis of awareness, with an apparently ‘vegetative’ patient having good awareness, is rare. Careful neurological assessment of the cause and routine measurement of awareness using the Coma Recovery Scale – Revised should further reduce mistakes.”

Wade DT: How often is the diagnosis of the permanent vegetative state incorrect? A review of the evidence. Eur. J. Neurol. 25(4): 619-625 (2018).


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Structured Abstract


“In 1853, Sydney Whiting wrote in his classic Memoirs of a Stomach, “…and between myself and that individual Mr. Brain, there was established a double set of electrical wires, by which means I could, with the greatest ease and rapidity, tell him all the occurrences of the day as they arrived, and he also could impart to me his own feelings and impressions.” Historically, it is known that the gut must communicate with the brain, but the underlying neural circuits and transmitters mediating gut-brain sensory transduction still remain unknown. In the gut, there is a single layer of epithelial cells separating the lumen from the underlying tissue. Dispersed within this layer reside electrically excitable cells termed enteroendocrine cells, which sense ingested nutrients and microbial metabolitesLike taste or olfactory receptor cells, enteroendocrine cells fire action potentials in the presence of stimuli. However, unlike other sensory epithelial cells, no synaptic link between enteroendocrine cells and a cranial nerve has been described. The cells are thought to act on nerves only indirectly through the slow endocrine action of hormones, like cholecystokinin. Despite its role in satiety, circulating concentrations of cholecystokinin peak only several minutes after food is ingested and often after the meal has ended. Such a discrepancy suggests that the brain perceives gut sensory cues through faster neuronal signaling. Using a mouse model, we sought to identify the underpinnings of this neural circuit that transduces a sense from gut to brain.


Our understanding of brain neural circuits is being propelled forward by the emergence of molecular tools that have high topographical and temporal precision. We adapted them for use in the gut. Single-cell quantitative real-time polymerase chain reaction and single-cell Western blot enabled the assessment of synaptic proteins. A monosynaptic rabies virus revealed the neural circuit’s synapse. The neural circuit was recapitulated in vitro by using nodose neurons cocultured with either minigut organoids or purified enteroendocrine cells. This system, coupled to optogenetics and whole-cell patch-clamp recording, served to determine the speed of transduction. Whole-nerve electrophysiology, along with optical excitation and silencing, helped to uncover the neurotransmission properties of the circuit in vivo. The underlying neurotransmitter was revealed by using receptor pharmacology and a fluorescent reporter called iGluSnFR.


Single-cell analyses showed that a subset of enteroendocrine cells contains presynaptic adhesion proteins, including some necessary for synaptic adhesion. Monosynaptic rabies tracing revealed that enteroendocrine cells synapse with vagal nodose neurons. This neuroepithelial circuit connects the intestinal lumen with the brainstem in one synapse. In coculture, this connection was sufficient to transduce a sugar stimulus from enteroendocrine cells to vagal neurons. Optogenetic activation of enteroendocrine cells elicited excitatory postsynaptic potentials in connected nodose neurons within milliseconds. In vivo recordings showed that enteroendocrine cells are indeed necessary and sufficient to transduce a sugar stimulus to the vagus. By using iGluSnFR, we found that enteroendocrine cells synthesize the neurotransmitter glutamate, and pharmacological inactivation of cholecystokinin and glutamate receptors revealed that these cells use glutamate as a neurotransmitter to transduce fast, sensory signals to vagal neurons.


We identified a type of gut sensory epithelial cell that synapses with vagal neurons. This cell has been referred to as the gut endocrine cell, but its ability to form a neuroepithelial circuit calls for a new name. We term this gut epithelial cell that forms synapses the neuropod cell. By synapsing with the vagus nerve, neuropod cells connect the gut lumen to the brainstem. Neuropod cells transduce sensory stimuli from sugars in milliseconds by using glutamate as a neurotransmitter. The neural circuit they form gives the gut the rapidity to tell the brain of all the occurrences of the day, so that he, too, can make sense of what we eat.”


Kaelberer MM, Buchanan KL, Klein ME, Barth BB, Montoya MM, Shen X, Bohórquez DV: A gut-brain neural circuit for nutrient sensory transduction. Science 361(6408): pii: eaat5236. doi: 10.1126/science.aat5236 (2018).




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Abstract: “Physical exercise has beneficial effects on neurocognitive function, including hippocampus-dependent episodic memory. Exercise intensity level can be assessed according to whether it induces a stress response; the most effective exercise for improving hippocampal function remains unclear. Our prior work using a special treadmill running model in animals has shown that stress-free mild exercise increases hippocampal neuronal activity and promotes adult neurogenesis in the dentate gyrus (DG) of the hippocampus, improving spatial memory performance. However, the rapid modification, from mild exercise, on hippocampal memory function and the exact mechanisms for these changes, in particular the impact on pattern separation acting in the DG and CA3 regions, are yet to be elucidated. To this end, we adopted an acute-exercise design in humans, coupled with high-resolution functional MRI techniques, capable of resolving hippocampal subfields. A single 10-min bout of very light-intensity exercise (30%[Formula: see text]) results in rapid enhancement in pattern separation and an increase in functional connectivity between hippocampal DG/CA3 and cortical regions (i.e., parahippocampal, angular, and fusiform gyri). Importantly, the magnitude of the enhanced functional connectivity predicted the extent of memory improvement at an individual subject level. These results suggest that brief, very light exercise rapidly enhances hippocampal memory function, possibly by increasing DG/CA3-neocortical functional connectivity.”

Suwabe K, Byun K, Hyodo K, Reagh ZM, Roberts JM, Matsushita A, Saotome K, Ochi G, Fukuie T, Suzuki K, Sankai Y, Yassa MA and Soya H: Rapid stimulation of human dentate gyrus function with acute mild exercise. Proc. Natl. Acad. Sci. USA [Epub ahead of print, Sept. 24, 2018; doi: 10.1073/pnas.1805668115].


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Abstract: “This paper examines the effect of both cumulative and transitory exposures to air pollution for the same individuals over time on cognitive performance by matching a nationally representative longitudinal survey and air quality data in China according to the exact time and geographic locations of the cognitive tests. [The authors] find that long-term exposure to air pollution impedes cognitive performance in verbal and math tests. [They] provide evidence that the effect of air pollution on verbal tests becomes more pronounced as people age, especially for men and the less educated. The damage on the aging brain by air pollution likely imposes substantial health and economic costs, considering that cognitive functioning is critical for the elderly for both running daily errands and making high-stake decisions.”

Zhang X, Chen X and Zhang X: The impact of exposure to air pollution on cognitive performance. Proc. Natl. Acad. Sci. USA 115(37): 9193-9197 (2018).


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