ResearchPad - rapid-communications https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Spontaneous repulsion in the A+B→0 reaction on coupled networks]]> https://www.researchpad.co/article/elastic_article_8193 We study the transient dynamics of an A+B→0 process on a pair of randomly coupled networks, where reactants are initially separated. We find that, for sufficiently small fractions q of cross couplings, the concentration of A (or B) particles decays linearly in a first stage and crosses over to a second linear decrease at a mixing time tx. By numerical and analytical arguments, we show that for symmetric and homogeneous structures tx∝(〈k〉/q)log(〈k〉/q) where 〈k〉 is the mean degree of both networks. Being this behavior is in marked contrast with a purely diffusive process, where the mixing time would go simply like 〈k〉/q, we identify the logarithmic slowing down in tx to be the result of a spontaneous mechanism of repulsion between the reactants A and B due to the interactions taking place at the networks' interface. We show numerically how this spontaneous repulsion effect depends on the topology of the underlying networks.

]]>
<![CDATA[Emergence of power laws in noncritical neuronal systems]]> https://www.researchpad.co/article/elastic_article_8183 Experimental and computational studies provide compelling evidence that neuronal systems are characterized by power-law distributions of neuronal avalanche sizes. This fact is interpreted as an indication that these systems are operating near criticality, and, in turn, typical properties of critical dynamical processes, such as optimal information transmission and stability, are attributed to neuronal systems. The purpose of this Rapid Communication is to show that the presence of power-law distributions for the size of neuronal avalanches is not a sufficient condition for the system to operate near criticality. Specifically, we consider a simplistic model of neuronal dynamics on networks and show that the degree distribution of the underlying neuronal network may trigger power-law distributions for neuronal avalanches even when the system is not in its critical regime. To certify and explain our findings we develop an analytical approach based on percolation theory and branching processes techniques.

]]>
<![CDATA[Role of hubs in the synergistic spread of behavior]]> https://www.researchpad.co/article/elastic_article_7194 The spread of behavior in a society has two major features: the synergy of multiple spreaders and the dominance of hubs. While strong synergy is known to induce mixed-order transitions (MOTs) at percolation, the effects of hubs on the phenomena are yet to be clarified. By analytically solving the generalized epidemic process on random scale-free networks with the power-law degree distribution pk∼k−α, we clarify how the dominance of hubs in social networks affects the conditions for MOTs. Our results show that, for α<4, an abundance of hubs drive MOTs, even if a synergistic spreading event requires an arbitrarily large number of adjacent spreaders. In particular, for 2<α<3, we find that a global cascade is possible even when only synergistic spreading events are allowed. These transition properties are substantially different from those of cooperative contagions, which are another class of synergistic cascading processes exhibiting MOTs.

]]>
<![CDATA[Middle East respiratory syndrome coronavirus experimental transmission using a pig model]]> https://www.researchpad.co/article/Na9f625c9-d241-427b-a971-5d683abb3e4c

Summary

Dromedary camels are the main reservoir of Middle East respiratory syndrome coronavirus (MERS‐CoV), but other livestock species (i.e., alpacas, llamas, and pigs) are also susceptible to infection with MERS‐CoV. Animal‐to‐animal transmission in alpacas was reported, but evidence for transmission in other species has not been proved. This study explored pig‐to‐pig MERS‐CoV transmission experimentally. Virus was present in nasal swabs of infected animals, and limited amounts of viral RNA, but no infectious virus were detected in the direct contact pigs. No virus was detected in the indirect contact group. Furthermore, direct and indirect contact pigs did not develop specific antibodies against MERS‐CoV. Therefore, the role of pigs as reservoir is probably negligible, although it deserves further confirmation.

]]>
<![CDATA[Prevalence, complete genome sequencing and phylogenetic analysis of porcine deltacoronavirus in South Korea, 2014-2016]]> https://www.researchpad.co/article/Nf026479f-4241-49a4-a546-d8ef5ee1b6ab

Summary

Porcine deltacoronavirus (PDCoV) is a newly emerged enterotropic swine coronavirus that causes enteritis and diarrhoea in piglets. Here, a nested reverse transcription (RT)‐PCR approach for the detection of PDCoV was developed to identify and characterize aetiologic agent(s) associated with diarrhoeal diseases in piglets in South Korea. A PCR‐based method was applied to investigate the presence of PDCoV in 683 diarrhoeic samples collected from 449 commercial pig farms in South Korea from January 2014 to December 2016. The molecular‐based survey indicated a relatively high prevalence of PDCoV (19.03%) in South Korea. Among those, the monoinfection of PDCoV (9.66%) and co‐infection of PDCoV (6.30%) with porcine epidemic diarrhoea (PEDV) were predominant in diarrhoeal samples. The full‐length genomes or the complete spike genes of the most recent strains identified in 2016 (KNU16‐07, KNU16‐08 and KNU16‐11) were sequenced and analysed to characterize PDCoV currently prevalent in South Korea. We found a single insertion‐deletion signature and dozens of genetic changes in the spike (S) genes of the KNU16 isolates. Phylogenetic analysis based on the entire genome and spike protein sequences of these strains indicated that they are most closely related to other Korean isolates grouped with the US strains. However, Korean PDCoV strains formed different branches within the same cluster, implying continuous evolution in the field. Our data will advance the understanding of the molecular epidemiology and evolutionary characteristics of PDCoV circulating in South Korea.

]]>
<![CDATA[Organ distribution of severe acute respiratory syndrome(SARS) associated coronavirus(SARS-CoV) in SARS patients: implications for pathogenesis and virus transmission pathways]]> https://www.researchpad.co/article/N453bcd21-28da-47ee-a9ec-5a0c4b2e7ef6

Abstract

We previously identified the major pathological changes in the respiratory and immune systems of patients who died of severe acute respiratory syndrome (SARS) but gained little information on the organ distribution of SARS‐associated coronavirus (SARS‐CoV). In the present study, we used a murine monoclonal antibody specific for SARS‐CoV nucleoprotein, and probes specific for a SARS‐CoV RNA polymerase gene fragment, for immunohistochemistry and in situ hybridization, respectively, to detect SARS‐CoV systematically in tissues from patients who died of SARS. SARS‐CoV was found in lung, trachea/bronchus, stomach, small intestine, distal convoluted renal tubule, sweat gland, parathyroid, pituitary, pancreas, adrenal gland, liver and cerebrum, but was not detected in oesophagus, spleen, lymph node, bone marrow, heart, aorta, cerebellum, thyroid, testis, ovary, uterus or muscle. These results suggest that, in addition to the respiratory system, the gastrointestinal tract and other organs with detectable SARS‐CoV may also be targets of SARS‐CoV infection. The pathological changes in these organs may be caused directly by the cytopathic effect mediated by local replication of the SARS‐CoV; or indirectly as a result of systemic responses to respiratory failure or the harmful immune response induced by viral infection. In addition to viral spread through a respiratory route, SARS‐CoV in the intestinal tract, kidney and sweat glands may be excreted via faeces, urine and sweat, thereby leading to virus transmission. This study provides important information for understanding the pathogenesis of SARS‐CoV infection and sheds light on possible virus transmission pathways. This data will be useful for designing new strategies for prevention and treatment of SARS. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

]]>
<![CDATA[Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus. A first step in understanding SARS pathogenesis]]> https://www.researchpad.co/article/N0c9678ff-4ab5-452f-9b6b-f58dfc676819

Abstract

Severe acute respiratory syndrome (SARS) is an acute infectious disease that spreads mainly via the respiratory route. A distinct coronavirus (SARS‐CoV) has been identified as the aetiological agent of SARS. Recently, a metallopeptidase named angiotensin‐converting enzyme 2 (ACE2) has been identified as the functional receptor for SARS‐CoV. Although ACE2 mRNA is known to be present in virtually all organs, its protein expression is largely unknown. Since identifying the possible route of infection has major implications for understanding the pathogenesis and future treatment strategies for SARS, the present study investigated the localization of ACE2 protein in various human organs (oral and nasal mucosa, nasopharynx, lung, stomach, small intestine, colon, skin, lymph nodes, thymus, bone marrow, spleen, liver, kidney, and brain). The most remarkable finding was the surface expression of ACE2 protein on lung alveolar epithelial cells and enterocytes of the small intestine. Furthermore, ACE2 was present in arterial and venous endothelial cells and arterial smooth muscle cells in all organs studied. In conclusion, ACE2 is abundantly present in humans in the epithelia of the lung and small intestine, which might provide possible routes of entry for the SARS‐CoV. This epithelial expression, together with the presence of ACE2 in vascular endothelium, also provides a first step in understanding the pathogenesis of the main SARS disease manifestations. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

]]>
<![CDATA[Detection of bovine coronavirus in nasal swab of non-captive wild water deer, Korea]]> https://www.researchpad.co/article/N72cb6648-7dc1-4aa7-97d9-fff382bb6e2f

Summary

Bovine coronavirus (BCoV) is a causative agent of respiratory and enteric diseases in cattle and calves. BCoV infection was also evident in captive wild ruminants. Recently, water deer are recognized as the most common wildlife to approach farmhouses and livestock barns in Korea. Therefore, we investigated 77 nasal swab samples from non‐captive wild water deer (Hydropotes inermis) between November 2016 and September 2017 and identified three samples positive for coronavirus, indicating potential for respiratory shedding. The full genomic sequences of the water deer coronavirus were closely related to BCoV (>98%). Therefore, effective biosecurity system in bovine farms would be necessary to prevent contact between farm ruminants and free‐ranging wild water deer.

]]>
<![CDATA[Characterization of a Novel Chimeric Swine Enteric Coronavirus from Diseased Pigs in Central Eastern Europe in 2016]]> https://www.researchpad.co/article/Nc0ecc99b-d737-4810-b919-8cacb9b8c49c

Summary

During a severe outbreak of diarrhoea and vomiting in a pig herd in Central Eastern Europe, faecal samples were tested positive for porcine epidemic diarrhoea virus (PEDV) and negative for transmissible gastroenteritis virus (TGEV) using a commercial RTqPCR assay that can detect both of these coronaviruses. However, further analyses, using other TGEV‐ and PEDV‐specific RTqPCR assays, provided results inconsistent with infection by either of these viruses. Sequencing of an amplicon (ca. 1.6 kb), generated by an RTPCR specific for the PEDV S‐gene, indicated a very close similarity (ca. 99% identity) to recently described chimeric viruses termed swine enteric coronaviruses (SeCoVs). These viruses (with an RNA genome of ca. 28 kb) were first identified in Italy in samples from 2009 but have not been detected there since 2012. A closely related virus was detected in archived samples in Germany from 2012, but has not been detected subsequently. Building on the initial sequence data, further amplicons were generated and over 9 kb of sequence corresponding to the 3′‐terminus of the new SeCoV genome was determined. Sequence comparisons showed that the three known SeCoVs are ≥98% identical across this region and contain the S‐gene and 3a sequences from PEDV within a backbone of TGEV, but the viruses are clearly distinct from each other. It is demonstrated, for the first time, that pigs from within the SeCoV‐infected herd seroconverted against PEDV but tested negative in a TGEV‐specific ELISA that detects antibodies against the S protein. These results indicate that SeCoV is continuing to circulate in Europe and suggest it can cause a disease that is very similar to PED. Specific detection of the chimeric SeCoVs either requires development of a new diagnostic RTqPCR assay or the combined use of assays targeting the PEDV S‐gene and another part of the TGEV genome.

]]>
<![CDATA[Different Lineage of Porcine Deltacoronavirus in Thailand, Vietnam and Lao PDR in 2015]]> https://www.researchpad.co/article/Nde1108df-e36a-492c-8925-d70a937ede26

Summary

Porcine deltacoronavirus (PDCoV) was detected by RTPCR in 12 of 97 (12.4%) intestinal samples collected during 2015 from piglets with diarrhoea in Thailand, Vietnam and Lao PDR. Spike, membrane and nucleocapsid genes were characterized, and phylogenetic analyses demonstrated that PDCoV isolates from Thai and Lao PDR form a novel cluster, separated from US and China isolates, but relatively were more closely related to China PDCoV than US isolates. Vietnam PDCoVs, however, were grouped together with US PDCoV. The analyses of amino acid changes suggested that they were from different lineage.

]]>
<![CDATA[ORF3a deletion in field strains of porcine-transmissible gastroenteritis virus in China: A hint of association with porcine respiratory coronavirus]]> https://www.researchpad.co/article/N05e38efa-e5f1-47a1-b017-7b4e8090643a

Summary

Porcine‐transmissible gastroenteritis virus (TGEV) is a pathogenic coronavirus responsible for high diarrhoea‐associated morbidity and mortality in suckling piglets. We analysed the TGEV ORF3 gene using nested polymerase chain reaction and identified an ORF3a deletion in three field strains of TGEV collected from piglets in China in 2015. Eight TGEV ORF3 sequences were obtained in this study. Phylogenetic tree analysis of ORF3 showed that the eight TGEV ORF3 genes all belonged to the Miller cluster. CHLNCT and CHMZL were closely correlated with Miller M6, while CHSH was correlated with Miller M60. These results thus indicate that the existence of Miller, as well as the Purdue cluster, in Chinese field strains of TGEV. Furthermore, we found the first evidence for a large deletion in ORF3 resulting in the loss of ORF3a, previously reported in porcine respiratory coronavirus, in three field strains (CHLNCT, CHMZL, and CHSH) of TGEV. The results of the present study thus provide important information regarding the underlying evolution mechanisms of coronaviruses.

]]>
<![CDATA[Newly Emerged PorcineDeltacoronavirusAssociated With Diarrhoea in Swine in China: Identification, Prevalence and Full-Length Genome Sequence Analysis]]> https://www.researchpad.co/article/N8e5eaeec-b85f-404d-87c1-376475ea9953

Summary

To identify and characterize aetiologic agent(s) associated with an outbreak of a severe diarrhoea in piglets in Jiangxi, China, in March 2015, a nested reverse transcription–polymerase chain reaction (RTPCR) for the detection of porcine deltacoronavirus (PDCoV) was developed. A survey based on the nested RTPCR established indicated that the monoinfection of PDCoV (33.71%) and coinfection of PDCoV (19.66%) with porcine epidemic diarrhoea virus (PEDV) were common in diarrhoeal pigs in Jiangxi, China. A high prevalence of PDCoV (58.33%) in diarrhoeal samples which were PEDV negative was observed. The complete genome sequence of a representative PDCoV strain, PDCoV/CHJXNI2/2015, was determined. Phylogenetic analysis of complete genome and S protein sequences of PDCoV/CHJXNI2/2015 demonstrated that it was most closely related to Hong Kong and US PDCoVs. To our knowledge, this is the first report on the identification, prevalence, complete genome sequencing and molecular characterizations of PDCoV in diarrhoeal samples in pigs in China.

]]>
<![CDATA[Detection and genetic characterization of porcine deltacoronavirus in Tibetan pigs surrounding the Qinghai-Tibet Plateau of China]]> https://www.researchpad.co/article/N2e8d2e7a-abda-411c-9871-fd959e29b227

Summary

Porcine deltacoronavirus (PDCoV) is a recently discovered RNA virus that belongs to the family Coronaviridae and genus Deltacoronavirus. This virus causes enteric disease in piglets that is characterized by enteritis and diarrhoea. In our present investigation, 189 diarrhoeic samples were collected between July 2016 and May 2017 from Tibetan pigs inhabiting in three different provinces surrounding the Qinghai–Tibet Plateau of China. We then applied the molecular‐based method of reverse transcription polymerase chain reactions (RTPCRs) to detect the presence of PDCoV in collected samples, and RTPCR indicated that the prevalence of PDCoV was 3.70% (7/189) in Tibetan pigs. Four of 7 PDCoV‐positive pigs were monoinfections of PDCoV, three samples were co‐infections of PDCoV with porcine epidemic diarrhoea virus (PEDV), and 52 (27.51%) samples were positive for PEDV. Four strains with different full‐length genomes were identified (CHN/GS/2016/1, CHN/GS/2016/2, CHN/GS‐/2017/1 and CHN/QH/2017/1), and their genomes were used to analyse the characteristics of PDCoV currently prevalent in Tibetan pigs. We found a 3‐nt insertion in the spike gene in four strains in Tibetan pigs. Phylogenetic analysis of the complete genome and spike and nucleocapsid gene sequences revealed that these strains shared ancestors with the strain CHNAH‐2004, which was found in pigs from the Anhui province of China mainland. However, PDCoV strains from Tibetan pigs formed different branches within the same cluster, implying continuous evolution in the field. Our present findings highlight the importance of epidemiologic surveillance to limit the spread of PDCoV in livestock at high altitudes in China.

]]>
<![CDATA[First report and phylogenetic analysis of porcine deltacoronavirus in Mexico]]> https://www.researchpad.co/article/Na90e4bc9-eee7-44c0-a33b-923c9302c99f

Abstract

Porcine deltacoronavirus has caused great economic losses in the swine industry worldwide. In this study, we carried out the first detection, sequencing and characterization of this virus in Mexico. We analysed 885 rectal samples by multiplex RT‐PCR to determine coinfections. In addition, the Spike gene was amplified, sequenced and analysed phylogenetically. We found 85 positive samples for porcine deltacoronavirus, representing 9.6% of the total samples, and we determined that the most frequent coinfection was with porcine epidemic diarrhoea virus (54.1%). Four sequences of Mexican isolates were most closely related to those of the United States. The antigenic regions and the glycosylation site of the strains obtained coincide with those previously reported. This relationship is probably related to the commercial exchange of pigs between the US and Mexico and the geographical proximity of these two countries.

]]>
<![CDATA[Detection of Severe Acute Respiratory Syndrome-Like, Middle East Respiratory Syndrome-Like Bat Coronaviruses and Group H Rotavirus in Faeces of Korean Bats]]> https://www.researchpad.co/article/Na9ee93a1-f8d0-435c-b381-489e15c291c0

Summary

Bat species around the world have recently been recognized as major reservoirs of several zoonotic viruses, such as severe acute respiratory syndrome coronavirus (SARS‐CoV), Middle East respiratory syndrome coronavirus (MERS‐CoV), Nipah virus and Hendra virus. In this study, consensus primer‐based reverse transcriptase polymerase chain reactions (RTPCRs) and high‐throughput sequencing were performed to investigate viruses in bat faecal samples collected at 11 natural bat habitat sites from July to December 2015 in Korea. Diverse coronaviruses were first detected in Korean bat faeces, including alphacoronaviruses, SARS‐CoV‐like and MERS‐CoV‐like betacoronaviruses. In addition, we identified a novel bat rotavirus belonging to group H rotavirus which has only been described in human and pigs until now. Therefore, our results suggest the need for continuing surveillance and additional virological studies in domestic bat.

]]>
<![CDATA[First Case of Systemic Coronavirus Infection in a Domestic Ferret (Mustela putorius furo) in Peru]]> https://www.researchpad.co/article/Na35d2cd8-7a46-458e-952f-22c4fb3152f7

Summary

A domestic ferret from Lima, Peru, died after ten days of non‐specific clinical signs. Based on pathology, immunohistochemistry and molecular analysis, ferret systemic coronavirus (FRSCV)‐associated disease was diagnosed for the first time in South America. This report highlights the potential spread of pathogens by the international pet trade.

]]>
<![CDATA[Detection and Phylogenetic Analysis of Porcine Deltacoronavirus in Korean Swine Farms, 2015]]> https://www.researchpad.co/article/N68db6076-cbf0-412d-8531-23595b4dbab5

Summary

This study applied molecular‐based method to investigate the presence of porcine deltacoronavirus (PDCoV) in 59 commercial pig farms in South Korea. The results of RTPCR screening on a relatively large collection of faeces samples (n = 681) from January 2013 to March 2015 did not reveal the presence of PDCoV until the end of 2014. However, on March 2015, PDCoV‐positive samples (SL2, SL5) were detected from SL swine farm in Gyeongbuk province. The phylogenetic trees based on the complete spike‐ and nucleocapsid protein‐coding genes showed that SL2 and SL5 closely related to the US PDCoV strains rather than those in China. Thought Korean strains of PDCoV isolated in 2014 (KNU14.04) and in 2015 (SL2 and SL5) grouped within US PDCoV cluster, the reconstruction of ancestral amino acid changes suggested that they are different.

]]>
<![CDATA[The clinical pathology of severe acute respiratory syndrome (SARS): a report from China]]> https://www.researchpad.co/article/N789e4c00-2cdb-44af-b97b-f9ff2f3d1f5a

Abstract

In order to investigate the clinical pathology of severe acute respiratory syndrome (SARS), the autopsies of three patients who died from SARS in Nan Fang Hospital Guangdong, China were studied retrospectively. Routine haematoxylin and eosin (H&E) staining was used to study all of the tissues from the three cases. The lung tissue specimens were studied further with Macchiavello staining, viral inclusion body staining, reticulin staining, PAS staining, immunohistochemistry, ultrathin sectioning and staining, light microscopy, and transmission electron microscopy. The first symptom was hyperpyrexia in all three cases, followed by progressive dyspnoea and lung field shadowing. The pulmonary lesions included bilateral extensive consolidation, localized haemorrhage and necrosis, desquamative pulmonary alveolitis and bronchitis, proliferation and desquamation of alveolar epithelial cells, exudation of protein and monocytes, lymphocytes and plasma cells in alveoli, hyaline membrane formation, and viral inclusion bodies in alveolar epithelial cells. There was also massive necrosis of splenic lymphoid tissue and localized necrosis in lymph nodes. Systemic vasculitis included oedema, localized fibrinoid necrosis, and infiltration of monocytes, lymphocytes, and plasma cells into vessel walls in the heart, lung, liver, kidney, adrenal gland, and the stroma of striated muscles. Thrombosis was present in small veins. Systemic toxic changes included degeneration and necrosis of the parenchyma cells in the lung, liver, kidney, heart, and adrenal gland. Electron microscopy demonstrated clusters of viral particles, consistent with coronavirus, in lung tissue. SARS is a systemic disease that injures many organs. The lungs, immune organs, and systemic small vessels are the main targets of virus attack, so that extensive consolidation of the lung, diffuse alveolar damage with hyaline membrane formation, respiratory distress, and decreased immune function are the main causes of death. Copyright © 2003 John Wiley & Sons, Ltd.

]]>
<![CDATA[Over-diagnosis of potential malignant behavior in MEN 2A-associated pheochromocytomas using the PASS and GAPP algorithms]]> https://www.researchpad.co/article/5c0e6a9ad5eed0c484e62886

Purpose

Pheochromocytomas (PCCs) exhibit malignant potential, but current histological modalities for the proper detection of aggressive behavior are debated. The two most widespread algorithms are the “Pheochromocytoma of the Adrenal Gland Scaled Score” (PASS) and the “Grading System for Adrenal Pheochromocytoma and Paraganglioma” (GAPP), both which mostly rely on histological parameters to identify PCC patients at risk of disseminated disease. Since the algorithms are derived from studies using predominantly sporadic PCCs, little is known whether the PASS or GAPP scores can predict malignant potential in hereditary cases.

Methods

PASS and GAPP were applied on 41 PCCs; 13 PCCs were diagnosed in ten multiple endocrine neoplasia type 2A (MEN 2A) patients carrying established germline RET proto-oncogene mutations, as well as 28 assumed sporadic PCCs.

Results

Six out of thirteen MEN 2A tumors (46%) exhibited PASS scores ≥ 4, indicative of a potential for aggressive behavior. In addition, 7/13 tumors (54%) exhibited GAPP scores ≥ 3, indicative of a “moderately differentiated type” with risk of future recurrence. All MEN 2A PCCs with an elevated PASS score also displayed an elevated GAPP score. In contrast, 4/28 (14%) sporadic PCCs demonstrated PASS scores ≥ 4, and 9/28 (32%) displayed GAPP scores ≥ 3. Follow-up found all cases in the study are free of metastatic or recurrent disease.

Conclusions

We conclude that the PASS and GAPP scoring systems might be suboptimal for determining true malignant potential in PCCs with constitutional RET mutations and advocate restrictive use of these scores in MEN 2A cases until the results are reproduced in larger numbers.

]]>
<![CDATA[The role of the hippocampus in generalizing configural relationships]]> https://www.researchpad.co/article/5b373aa3463d7e66650bd338

ABSTRACT

The hippocampus has been implicated in integrating information across separate events in support of mnemonic generalizations. These generalizations may be underpinned by processes at both encoding (linking similar information across events) and retrieval (“on‐the‐fly” generalization). However, the relative contribution of the hippocampus to encoding‐ and retrieval‐based generalizations is poorly understood. Using fMRI in humans, we investigated the hippocampal role in gradually learning a set of spatial discriminations and subsequently generalizing them in an acquired equivalence task. We found a highly significant correlation between individuals’ performance on a generalization test and hippocampal activity during the test, providing evidence that hippocampal processes support on‐the‐fly generalizations at retrieval. Within the same hippocampal region there was also a correlation between activity during the final stage of learning (when all associations had been learnt but no generalization was required) and subsequent generalization performance. We suggest that the hippocampus spontaneously retrieves prior events that share overlapping features with the current event. This process may also support the creation of generalized representations during encoding. These findings are supportive of the view that the hippocampus contributes to both encoding‐ and retrieval‐based generalization via the same basic mechanism; retrieval of similar events sharing common features. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.

]]>