ABSTRACT
Objective We aimed to investigate whether antagonism of the cannabinoid CB1 receptor (CB1R) could affect novel object recognition (NOR) memory in chronically rapid eye movement sleep-deprived (RSD) rats.Methods The animals were examined for recognition memory following a 7-day chronic partial RSD paradigm using the multiple platform technique. The CB1R antagonist rimonabant (1 or 3 mg/kg, i.p.) was administered either at one hour prior to the sample phase for acquisition, or immediately after the sample phase for consolidation, or at one hour before the test phase for retrieval of NOR memory. For the reconsolidation task, rimonabant was administered immediately after the second sample phase.Results The RSD episode impaired acquisition, consolidation, and retrieval, but it did not affect the reconsolidation of NOR memory. Rimonabant administration did not affect acquisition, consolidation, and reconsolidation; however, it attenuated impairment of the retrieval of NOR memory induced by chronic RSD.Conclusions These findings, along with our previous report, would seem to suggest that RSD may affect different phases of recognition memory based on its duration. Importantly, it seems that the CB1R may, at least in part, be involved in the adverse effects of chronic RSD on the retrieval, but not in the acquisition, consolidation, and reconsolidation, of NOR memory.
Subject(s)
Rats , Animals , Rimonabant/pharmacology , Memory , Sleep, REM , Receptors, Cannabinoid , Cannabinoids/pharmacologyABSTRACT
Resumo Conformidade de memória é o fenômeno em que relatos de memória de uma pessoa são modificados após exposição aos relatos de outra pessoa. Estudos sobre conformidade de memória são importantes tanto no âmbito puro quanto aplicado, especialmente quando os estímulos são carregados emocionalmente. No entanto, estudos de conformidade de memória com estímulos emocionais ainda são escassos. Além disso, os poucos estudos sobre o tema apresentam resultados contraditórios. Nesta revisão, apresentamos um breve resumo de pesquisas sobre conformidade de memória em tarefas de reconhecimento e avaliamos o papel moderador da emocionalidade na conformidade. Sugerimos como possível direção de pesquisas futuras a avaliação de duas variáveis, intervalo de retenção e distintividade dos estímulos, que podem ser cruciais para elucidar as inconsistências empíricas.
Abstract Memory conformity refers to the phenomenon in which memory reports from one person are modified by memory reports from another person. The study of memory conformity is important both in basic and applied settings, especially when the stimuli are emotionally-laden. Research on memory conformity for emotional stimuli, however, is surprisingly scarce. Here we briefly review research on memory conformity in recognition tasks and assess the modulatory role of emotionality on conformity effects. We also propose further research based on the manipulation of two variables, retention interval and stimulus distinctiveness, that could help to reconcile the discrepant findings in the literature.
ABSTRACT
OBJECTIVE: To observe the influence of different courses of electroacupuncture (EA) intervention on recognition memory and the proliferation and differentiation of hippocampal neural stem cells in mice with radiation-induced brain injury, so as to explore its mechanisms underlying improving radiation-induced brain injury. METHODS: Se-venty 30-day old C57BL/6J mice were randomly divided into control, model and EA groups, and the latter two groups were further divided into 1 week (W), 2 W and 3 W subgroups (n=10 in the control group and each subgroup). The ra-diation-induced brain injury model was established by radiating the mouse' left head at a dose of 8 Gy for 10 min by using a radiation linear accelerator. EA (1.5 V, 2 Hz/10 Hz) was applied to "Baihui" (GV20), "Fengfu" (GV14) and bilateral "Shenshu" (BL23) for 30 min, once daily for 1, 2 and 3 weeks, respectively. The learning-cognition memory ability was detected by using novel object recognition test in an open test box to record the time for exploring a novel object (TN) and a familiar object and to calculate the recognition index (RI). The neural stem cells' proliferation and differentiation in the hippocampus tissues were evaluated by counting the number of bromodeoxyuridine (BrdU)-labeled cells, neuronal nuclei (NeuN)/BrdU-positive cells and BrdU/glia fibrillary acidic protein (GFAP)-positive cells under microscope after immunofluorescence stain. RESULTS: After modeling, the TN at 90 min and 24 h and RI of the model subgroup 3 W at 90 min and RI of the model subgroup 1, 2 and 3 W at 24 h were significantly decreased in comparison with those of the control group (P<0.01, P<0.05). Moreover, the number of BrdU-positive cells in the model subgroup 1 W and 2 W, the BrdU/NeuN double-labeled cells in the 3 model subgroups and BrdU/GFAP double-labeled cells in the model subgroup 1 W and 3 W were significantly decreased (P<0.01, P<0.05). Following EA interventions, the TN in the 3 EA subgroups at both 90 min and 24 h, and RI of EA subgroup 3 W at 90 min and EA subgroup 2 W and 3 W at 24 h were considerably increased compared with those of the corresponding 3 model subgroups (P<0.05, P<0.01). The numbers of BrdU-positive cells as well as BrdU/NeuN and BrdU/GFAP double-labeled cells were significantly increased in the 3 EA subgroups (P<0.05, P<0.01, P<0.001). CONCLUSION: EA of GV20, GV14 and BL23 can improve the recognition memory ability of mice with radiation-induced brain injury, which may be related to its effect in promoting the proliferation and differentiation of stem cells in the hippocampus.
ABSTRACT
As the elderly population is increasing, Alzheimer's disease (AD) has become a global issue and many clinical trials have been conducted to evaluate treatments for AD. As these clinical trials have been conducted and have failed, the development of new theraphies for AD with fewer adverse effects remains a challenge. In this study, we examined the effects of Theracurmin on cognitive decline using 5XFAD mice, an AD mouse model. Theracurmin is more bioavailable form of curcumin, generated with submicron colloidal dispersion. Mice were treated with Theracurmin (100, 300 and 1,000 mg/kg) for 12 weeks and were subjected to the novel object recognition test and the Barnes maze test. Theracurmin-treated mice showed significant amelioration in recognition and spatial memories compared those of the vehicle-treated controls. In addition, the antioxidant activities of Theracurmin were investigated by measuring the superoxide dismutase (SOD) activity, malondialdehyde (MDA) and glutathione (GSH) levels. The increased MDA level and decreased SOD and GSH levels in the vehicle-treated 5XFAD mice were significantly reversed by the administration of Theracurmin. Moreover, we observed that Theracurmin administration elevated the expression levels of synaptic components, including synaptophysin and post synaptic density protein 95, and decreased the expression levels of ionized calcium-binding adapter molecule 1 (Iba-1), a marker of activated microglia. These results suggest that Theracurmin ameliorates cognitive function by increasing the expression of synaptic components and by preventing neuronal cell damage from oxidative stress or from the activation of microglia. Thus, Theracurmin would be useful for treating the cognitive dysfunctions observed in AD.
Subject(s)
Aged , Animals , Humans , Mice , Alzheimer Disease , Cognition , Colloids , Curcumin , Glutathione , Malondialdehyde , Microglia , Neurons , Oxidative Stress , Post-Synaptic Density , Spatial Memory , Superoxide Dismutase , SynaptophysinABSTRACT
Objective: To evaluate the effects of Hypericum perforatum (hypericum) on cognitive behavior and neurotrophic factor levels in the brain of male and female rats. Methods: Male and female Wistar rats were treated with hypericum or water during 28 days by gavage. The animals were then subjected to the open-field test, novel object recognition and step-down inhibitory avoidance test. Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and glial cell-line derived neurotrophic factor (GDNF) levels were evaluated in the hippocampus and frontal cortex. Results: Hypericum impaired the acquisition of short- and long-term aversive memory in male rats, evaluated in the inhibitory avoidance test. Female rats had no immediate memory acquisition and decreased short-term memory acquisition in the inhibitory avoidance test. Hypericum also decreased the recognition index of male rats in the object recognition test. Female rats did not recognize the new object in either the short-term or the long-term memory tasks. Hypericum decreased BDNF in the hippocampus of male and female rats. Hypericum also decreased NGF in the hippocampus of female rats. Conclusions: The long-term administration of hypericum appears to cause significant cognitive impairment in rats, possibly through a reduction in the levels of neurotrophic factors. This effect was more expressive in females than in males.
Subject(s)
Animals , Male , Female , Plant Extracts/pharmacology , Cognition/drug effects , Hypericum , Frontal Lobe/metabolism , Hippocampus/metabolism , Nerve Growth Factors/analysis , Plant Extracts/administration & dosage , Random Allocation , Sex Factors , Treatment Outcome , Rats, Wistar , Models, Animal , Pattern Recognition, Physiological/drug effects , Dose-Response Relationship, Drug , Frontal Lobe/drug effects , Hippocampus/drug effects , Locomotion/drug effects , Memory/drug effects , Nerve Growth Factors/drug effectsABSTRACT
Objective To investigate the long-term effects of repeated neonatal administration of dizocipline maleate (MK-801),the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist,on recognition memory and hippocampal excitatory-inhibitory balance at the synaptic level in adult female rats.Methods Neonatal female Sprague-Dawley (SD) rats were randomly divided into model group and control group.Rats were administrated subcutaneously with MK-801 or normal saline from postnatal day (PND) 5 to PND14 (0.25 mg/kg,twice daily).(1) Object-in-context recognition test was performed on PND73-75.(2)The expression levels of vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter (VGAT) in hippocampus were detected by immunohistochemical staining.Results (1) The preference index of model group for new objects was significantly lower than that of the control group (t =-2.762,P=0.012).(2) There was no significant difference in the expression of VGLUT1 in hippocampus of MK-801 mode group(P＞0.05).Compared with control group(48.19±2.10),the VGAT level of model group in CA1 (39.60±2.19) was lower.Compared with control group (CA1:(0.99±0.05),CA3:(1.28±0.02),the ratio of VGLUT1/VGAT was significantly upregulated in CA1(1.16±0.05) and CA3(1.44±0.03) (P＜0.05).Conclusion Early NMDA receptor inhibition produces long-term deleterious effects on associative recognition memory and excitatory-inhibitory balance of hippocampus in female rats.These biochemical abnormalities may contribute to cognitive impairments observed in this study.
ABSTRACT
ABSTRACT The main aim of this paper was to provide new evidence on the effects of valence on recognition memory of emotional pictures, on the basis of rigorous experimental control of stimulus material. Valence was manipulated using pleasant and unpleasant pictures, keeping arousal constant at a high level. A reference condition with a neutral value in both dimensions was also included. We found greater discrimination and a more conservative response bias, as well as slower recognition decisions, for pleasant pictures. Also worthy of mention is the high positive correlation between response times and discrimination measures just for such pictures. These results would be consistent with an adaptive interpretation based on motivation and personal relevance of emotional information.
RESUMEN El principal objetivo del presente trabajo fue aportar nueva evidencia sobre los efectos de la valencia en el reconocimiento de imágenes de contenido emocional, a partir de un riguroso control experimental del material estimular. Se manipuló la valencia a niveles agradable y desagradable, manteniendo constante el arousal a un nivel alto. Se incluyó también una condición de referencia con un valor neutro en ambas dimensiones. Se encontró una mejor discriminación, un sesgo de respuesta más conservador y un reconocimiento más lento para las imágenes agradables. Además, solo para estas imágenes existió alta correlación positiva entre tiempos de respuesta y discriminación. Estos resultados serían consistentes con una interpretación de carácter adaptativo basada en la motivación y relevancia personal de la información emocional.
Subject(s)
Arousal , Imagery, Psychotherapy/classificationABSTRACT
OBJECTIVES: The deficit of recognition memory has been found as one of the common neurocognitive impairments in patients with schizophrenia. In addition, they were reported to fail to enhance the memory about emotional stimuli. Previous studies have shown that bilateral eye movements enhance the memory retrieval. Therefore, this study was conducted in order to investigate the memory enhancement of bilaterally alternating eye movements in schizophrenic patients. METHODS: Twenty one patients with schizophrenia participated in this study. The participants learned faces (angry or neutral faces), and then performed a recognition memory task in relation to the faces after bilateral eye movements and central fixation. Recognition accuracy, response bias, and mean response time to hits were compared and analysed. Two-way repeated measure analysis of variance was performed for statistical analysis. RESULTS: There was a significant effect of bilateral eye movements condition in mean response time(F=5.812, p<0.05) and response bias(F=10.366, p<0.01). Statistically significant interaction effects were not observed between eye movement condition and face emotion type. CONCLUSIONS: Irrespective of the emotional difference of facial stimuli, recognition memory processing was more enhanced after bilateral eye movements in patients with schizophrenia. Further study will be needed to investigate the underlying neural mechanism of bilateral eye movements-induced memory enhancement in patients with schizophrenia.
Subject(s)
Humans , Bias , Eye Movements , Memory , Reaction Time , SchizophreniaABSTRACT
Os objetivos deste estudo foram desenvolver uma versão computadorizada para um teste de reconhecimento associativo, desenvolver itens para a construção e informatização de um teste de reconhecimento de itens, utilizando o modelo de Rasch. Também foi objetivo deste estudo testar as hipóteses dos níveis de dificuldade dos itens e buscar evidência de validade para os instrumentos, averiguando se as mulheres obtêm desempenho superior ao dos homens. Participaram 217 estudantes universitários, homens e mulheres, com idade média de 25 anos. Os resultados indicaram que os testes se ajustaram ao modelo de Rasch, apresentaram índices de fidedignidade adequados e não apresentaram funcionamento diferencial dos itens (DIF). Obteve-se empiricamente a ordem esperada de dificuldade das categorias de itens do teste individual e uma alta correlação entre a ordem de dificuldade esperada dos pares e a ordem obtida dos pares. As mulheres apresentaram um desempenho significativamente superior ao dos homens, que não se deve ao DIF.
The objectives of this study were to develop items for a computerized version of an associative recognition memory test and to develop items for the construction and computerization of an individual recognition memory test, using the Rasch model. This study also aimed to test the hypothesis related to the item difficulty levels and to search for validity evidences for the instruments investigating if there are differences between male and female performance. Two hundred and seventeen college students, male and female, with average age of 25 years, participated in the study. Results indicated that the tests fit the Rasch model, presented adequate reliability index and did not present differential item functioning (DIF). The expected difficulty order of item categories from the individual subtest as well as a large correlation between the pairs expected difficulty order and the pairs obtained order were found. Women presented significantly higher performance than men and it is not due to DIF.
Subject(s)
Humans , Male , Female , Young Adult , Computers , Memory , Psychometrics , Recognition, Psychology , Surveys and QuestionnairesABSTRACT
The initial period of postnatal life is critical for brain development in both rodents and humans. Protein malnutrition imposed during this period produces irreversible consequences that include structural, neurochemical, and functional changes in the central nervous system, leading to long-term alterations in behavioral and cognitive parameters, such as memory. In this work, previously malnourished rats were evaluated in recognition memory procedures. Male Wistar rats (n = 132) were given isocaloric diets that contained 6% (malnourished) or 16% (control) protein until 49 days of life. A nutritional recovery period with standard lab chow was imposed from 50 to 70 days of age when the experiments began. Four different procedures of recognition memory were conducted. The analysis showed that malnourished rats had lower body weight compared with control rats from the first week of life until the end of the experiments (p < .05). In the memory procedures, malnourished rats had lower recognition indices compared with controls (p < .05). Well-nourished rats had a tendency to direct their exploration toward novelty, whereas malnourished rats explored the objects in the same proportion, demonstrating that they did not recognize the novelty. Protein malnutrition imposed early in life is suggested to affect hippocampal formation, the development of which is concentrated during this developmental period, and thus impair memory consolidation...
Subject(s)
Animals , Rats , Memory, Short-TermABSTRACT
OBJECTIVES: Previous studies have shown that bilateral eye movements enhance episodic memory retrieval. However, few studies on the effect of bilateral eye movements on emotional memory have been reported. Therefore, this study was conducted in order to investigate the differences in memory retrieval between neutral and angry stimuli after bilaterally alternating eye movements. METHODS: Twenty seven healthy right-handed subjects participated in this study. The participants learned faces (angry or neutral face), and then performed a recognition memory task in relation to the faces after bilateral eye movements and central fixation. Recognition accuracy, response bias, and mean response time to hits were compared and analyzed. Two-way repeated measure analysis of variance was performed for statistical analysis. RESULTS: There was a significant effect of bilateral eye movement conditions in recognition accuracy (F=13.833, p<0.01). Statistically significant interaction effects were observed between eye movement condition and face emotion type (F=6.253, p=0.02). CONCLUSION: In this study, recognition memory for angry faces was more enhanced than that for neutral faces after bilateral eye movements. This finding suggests that bilateral eye movements can improve recognition memory for emotional stimuli more than that for neutral stimuli.
Subject(s)
Bias , Eye Movements , Memory , Memory, Episodic , Reaction TimeABSTRACT
OBJECTIVES: Previous studies have shown that bilateral eye movements enhance episodic memory retrieval. However, few studies on the effect of bilateral eye movements on emotional memory have been reported. Therefore, this study was conducted in order to investigate the differences in memory retrieval between neutral and angry stimuli after bilaterally alternating eye movements. METHODS: Twenty seven healthy right-handed subjects participated in this study. The participants learned faces (angry or neutral face), and then performed a recognition memory task in relation to the faces after bilateral eye movements and central fixation. Recognition accuracy, response bias, and mean response time to hits were compared and analyzed. Two-way repeated measure analysis of variance was performed for statistical analysis. RESULTS: There was a significant effect of bilateral eye movement conditions in recognition accuracy (F=13.833, p<0.01). Statistically significant interaction effects were observed between eye movement condition and face emotion type (F=6.253, p=0.02). CONCLUSION: In this study, recognition memory for angry faces was more enhanced than that for neutral faces after bilateral eye movements. This finding suggests that bilateral eye movements can improve recognition memory for emotional stimuli more than that for neutral stimuli.
Subject(s)
Bias , Eye Movements , Memory , Memory, Episodic , Reaction TimeABSTRACT
Objective To observe the behavioral effects of acute administration of dizocilpine (MK-801) in rats,and to determine an appropriate doses of the drug to mimicking memory deficits of schizophrenia.Methods 192 rats were randomly divided into model groups and control group,and given different doses of MK-801 or saline.Locomotor activity,pre-pulse inhibition (PPI) test and novel object recognition test were studied respectively.Results The spontaneous activity increased in a dose-dependent manner after the treatment of MK-801.The total distances of locomotor activity in 0.3 mg/kg group((127.04 ± 32.35) m) exhibited a significant difference compared with control group((35.34 ± 12.81) m,P ＜ 0.05).MK-801 decreased PPI in dose-dependent manner(P ＜ 0.01).MK-801 0.1 mg/kg((103.45 ± 68.04) ％) and 0.3 mg/kg ((41.55 ± 62.93) ％) groups showed significant differences compared to control group ((200.39 ± 30.97) ％) in PPI.The discrimination index of 0.03 mg/kg group((15.78 ± 6.23) ％) and 0.1 mg/kg group((22.42 ± 3.85) ％) were lower than that in control group((39.42 ±3.86)％,P＜0.05).Conclusion It is necessary for select right doses for model different endophenotypes of schizophrenia by MK-801.0.03 mg/kg of MK-801 is a relatively appropriate dosage to cause recognition memory damage.
ABSTRACT
OBJECTIVES: Recently, Interest has been increase on the cognitive and emotional effects of bilateral eye movement. However, there is little research related to the subject in Korea. In this study, we evaluated the effects of bilateral eye movement to memory. METHODS: There were a total of 24 subjects between the ages of 18 and 45. All were right-handed. The subjects first studied words, and then performed recognition memory task about the words after bilateral eye movement and eye fixation. The results (recognition accuracy, response bias, mean response to hits) were compared and analyzed. In addition, We evaluated whether the results differ according to the type of word. Repeated measure analysis of variance was performed for statistical analysis. RESULTS: The main effects on condition [F(1, 23)=9.39, p<0.05] and word type [F(1, 23)=33.727, p<0.05] in recognition accuracy were statistically significant. Also main effect of mean response time to hits was observed [F(1, 23)=66.482, p<0.05]. CONCLUSION: These results suggest that bilateral eye movement enhance recognition accuracy than eye fixation. In this study, bilateral eye movement that affects cognition were investigated.
Subject(s)
Bias , Cognition , Eye , Eye Movements , Korea , Memory , Reaction Time , Task Performance and AnalysisABSTRACT
A modified version of the intruder-resident paradigm was used to investigate if social recognition memory lasts at least 24 h. One hundred and forty-six adult male Wistar rats were used. Independent groups of rats were exposed to an intruder for 0.083, 0.5, 2, 24, or 168 h and tested 24 h after the first encounter with the familiar or a different conspecific. Factor analysis was employed to identify associations between behaviors and treatments. Resident rats exhibited a 24-h social recognition memory, as indicated by a 3- to 5-fold decrease in social behaviors in the second encounter with the same conspecific compared to those observed for a different conspecific, when the duration of the first encounter was 2 h or longer. It was possible to distinguish between two different categories of social behaviors and their expression depended on the duration of the first encounter. Sniffing the anogenital area (49.9 percent of the social behaviors), sniffing the body (17.9 percent), sniffing the head (3 percent), and following the conspecific (3.1 percent), exhibited mostly by resident rats, characterized social investigation and revealed long-term social recognition memory. However, dominance (23.8 percent) and mild aggression (2.3 percent), exhibited by both resident and intruders, characterized social agonistic behaviors and were not affected by memory. Differently, sniffing the environment (76.8 percent of the non-social behaviors) and rearing (14.3 percent), both exhibited mostly by adult intruder rats, characterized non-social behaviors. Together, these results show that social recognition memory in rats may last at least 24 h after a 2-h or longer exposure to the conspecific.
Subject(s)
Animals , Male , Rats , Agonistic Behavior/physiology , Recognition, Psychology/physiology , Social Behavior , Analysis of Variance , Principal Component Analysis , Rats, WistarABSTRACT
Objective To investigate cross-cultural differences in picture recognition memory of medical students. Methods Picture recognition memory were assessed by the classic new-old picture recognition,and behavioral results were recorded during the test. Results For new medical picture recognition, mean accuracy of Chinese medical students( 83.21 ± 8.95 )% was considerably higher than that of Indian medical students( 75.56 ±12.63)% (P＜0.05), while for old medical picture recognition, reaction time (RT) of Chinese medical students ( ( 887.57 ± 104.07 ) ms ) was longer than that of Indian medical students ( ( 840.93 ± 1 22.48 ) ms) (P＜0.05).Three way ANOVA suggested that cultural background and picture type significantly affected accuracy and RT,learning experience affected RT. In addition to picture type and learning experience, the interaction of each factors is not remarkable. Conclusion Cultural background, professional background and learning experiences have affected recognition memory. Medical students of different cultural background adopted difference strategies in picture recognition memory.
ABSTRACT
Object recognition memory allows discrimination between novel and familiar objects. This kind of memory consists of two components: recollection, which depends on the hippocampus, and familiarity, which depends on the perirhinal cortex (Pcx). The importance of brain-derived neurotrophic factor (BDNF) for recognition memory has already been recognized. Recent evidence suggests that DNA methylation regulates the expression of BDNF and memory. Behavioral and molecular approaches were used to understand the potential contribution of DNA methylation to recognition memory. To that end, rats were tested for their ability to distinguish novel from familiar objects by using a spontaneous object recognition task. Furthermore, the level of DNA methylation was estimated after trials with a methyl-sensitive PCR. We found a signifcant correlation between performance on the novel object task and the expression of BDNF, negatively in hippocampal slices and positively in perirhinal cortical slices. By contrast, methylation of DNA in CpG island 1 in the promoter of exon 1 in BDNF only correlated in hippocampal slices, but not in the Pxc cortical slices from trained animals. These results suggest that DNA methylation may be involved in the regulation of the BDNF gene during recognition memory, at least in the hippocampus.
Subject(s)
Animals , Male , Rats , Brain-Derived Neurotrophic Factor/metabolism , DNA Methylation/physiology , Hippocampus/metabolism , Memory/physiology , Recognition, Psychology/physiology , Brain-Derived Neurotrophic Factor/physiology , Hippocampus/physiology , Rats, Sprague-DawleyABSTRACT
Studies have shown a time-of-day of training effect on long-term explicit memory with a greater effect being shown in the afternoon than in the morning. However, these studies did not control the chronotype variable. Therefore, the purpose of this study was to assess if the time-of-day effect on explicit memory would continue if this variable were controlled, in addition to identifying the occurrence of a possible synchronic effect. A total of 68 undergraduates were classified as morning, intermediate, or afternoon types. The subjects listened to a list of 10 words during the training phase and immediately performed a recognition task, a procedure which they repeated twice. One week later, they underwent an unannounced recognition test. The target list and the distractor words were the same in all series. The subjects were allocated to two groups according to acquisition time: a morning group (N = 32), and an afternoon group (N = 36). One week later, some of the subjects in each of these groups were subjected to a test in the morning (N = 35) or in the afternoon (N = 33). The groups had similar chronotypes. Long-term explicit memory performance was not affected by test time-of-day or by chronotype. However, there was a training time-of-day effect [F (1,56) = 53.667; P = 0.009] with better performance for those who trained in the afternoon. Our data indicated that the advantage of training in the afternoon for long-term memory performance does not depend on chronotype and also that this performance is not affected by the synchronic effect.