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remote memory [keywords]
- The relationship between NMDA receptors and microwave induced learning and memory impairment: a long term observation on Wistar rats. [JOURNAL ARTICLE]
- Int J Radiat Biol 2014 Nov 26.:1-25.
Abstract Purpose: In the present study, we intended to investigate whether the high power microwave could cause the continuous disorders of learning and memory in Wistar rats and to explore the underlying mechanisms. Materials and methods: 80 Wistar rats were exposed to a 2.856 GHz pulsed microwave source at a power density of 0 mW/cm(2) and 50 mW/cm(2) microwave for 6 min. The spatial memory ability, the structure of the hippocampus, contents of amino acids neurotransmitters in hippocampus and the expression of N-methyl-D-aspartic acid receptors (NMDAR) subunit 1, 2A and 2B (NR1, NR2A and NR2B) were detected at 1 m, 3 m, 6 m, 9 m, 12 m and 18 m after microwave exposure. Results: Our results showed that the microwave exposed rats showed consistent deficiencies in spatial learning and memory. The level of amino acid neurotransmitters also decreased after microwave radiation. The ratio of glutamate (Glu) and gammaaminobutyric acid (GABA) significantly decreased at 6 m. Besides, the hippocampus showed varying degrees of degeneration of neurons, increased postsynaptic density and blurred synaptic clefts in the exposure group. The NR1 and NR2B expression showed a significant decrease, especially the NR2B expression. Conclusions: This study indicated that the content of amino acids neurotransmitters, the expression of NMDAR subunits and the variation of hippocampal structure might contribute to the long term cognitive impairment after microwave exposure.
- Laminar activity in the hippocampus and entorhinal cortex related to novelty and episodic encoding. [Journal Article]
- Nat Commun 2014.:5547.
The ability to form long-term memories for novel events depends on information processing within the hippocampus (HC) and entorhinal cortex (EC). The HC-EC circuitry shows a quantitative segregation of anatomical directionality into different neuronal layers. Whereas superficial EC layers mainly project to dentate gyrus (DG), CA3 and apical CA1 layers, HC output is primarily sent from pyramidal CA1 layers and subiculum to deep EC layers. Here we utilize this directionality information by measuring encoding activity within HC/EC subregions with 7 T high resolution functional magnetic resonance imaging (fMRI). Multivariate Bayes decoding within HC/EC subregions shows that processing of novel information most strongly engages the input structures (superficial EC and DG/CA2-3), whereas subsequent memory is more dependent on activation of output regions (deep EC and pyramidal CA1). This suggests that while novelty processing is strongly related to HC-EC input pathways, the memory fate of a novel stimulus depends more on HC-EC output.
- Transcriptional Evidence for the Role of Chronic Venlafaxine Treatment in Neurotrophic Signaling and Neuroplasticity Including also Glutatmatergic- and Insulin-Mediated Neuronal Processes. [JOURNAL ARTICLE]
- PLoS One 2014; 9(11):e113662.
Venlafaxine (VLX), a serotonine-noradrenaline reuptake inhibitor, is one of the most commonly used antidepressant drugs in clinical practice for the treatment of major depressive disorder (MDD). Despite being more potent than its predecessors, similarly to them, the therapeutical effect of VLX is visible only 3-4 weeks after the beginning of treatment. Furthermore, recent papers show that antidepressants, including also VLX, enhance the motor recovery after stroke even in non depressed persons. In the present, transcriptomic-based study we looked for changes in gene expressions after a long-term VLX administration.Osmotic minipumps were implanted subcutaneously into Dark Agouti rats providing a continuous (40 mg/kg/day) VLX delivery for three weeks. Frontal regions of the cerebral cortex were isolated and analyzed using Illumina bead arrays to detect genes showing significant chances in expression. Gene set enrichment analysis was performed to identify specific regulatory networks significantly affected by long term VLX treatment.Chronic VLX administration may have an effect on neurotransmitter release via the regulation of genes involved in vesicular exocytosis and receptor endocytosis (such as Kif proteins, Myo5a, Sv2b, Syn2 or Synj2). Simultaneously, VLX activated the expression of genes involved in neurotrophic signaling (Ntrk2, Ntrk3), glutamatergic transmission (Gria3, Grin2b and Grin2a), neuroplasticity (Camk2g/b, Cd47), synaptogenesis (Epha5a, Gad2) and cognitive processes (Clstn2). Interestingly, VLX increased the expression of genes involved in mitochondrial antioxidant activity (Bcl2 and Prdx1). Additionally, VLX administration also modulated genes related to insulin signaling pathway (Negr1, Ppp3r1, Slc2a4 and Enpp1), a mechanism that has recently been linked to neuroprotection, learning and memory.Our results strongly suggest that chronic VLX treatment improves functional reorganization and brain plasticity by influencing gene expression in regulatory networks of motor cortical areas. These results are consonant with the synaptic (network) hypothesis of depression and antidepressant-induced motor recovery after stroke.
- Cognitive function and social attainment in adult survivors of retinoblastoma: A report from the St. Jude Lifetime Cohort Study. [JOURNAL ARTICLE]
- Cancer 2014 Nov 24.
Retinoblastoma has a 5-year survival rate exceeding 95%, yet little is known about long-term functional outcomes for these patients.Sixty-nine adult survivors of retinoblastoma (mean age, 33 years; mean years post-diagnosis, 31) who had enrolled in the St. Jude Lifetime Cohort Study completed clinical cognitive evaluations and questionnaires assessing adult social attainment. Scores on all cognitive measures were converted to z-scores (M = 0, SD = 1) using age-adjusted normative data. Multivariable linear regression analyses, adjusted for age at diagnosis and disease laterality, were used to examine associations between disease and treatment exposures and cognitive outcomes.Retinoblastoma survivors performed within normative expectations across most cognitive domains. In multivariable models, adjusted for disease laterality, survivors diagnosed at ≤1 year of age performed significantly better on measures of short-term verbal memory (β = 0.87, P<.01), long-term verbal memory (β = 0.66, P = .02), verbal learning (β = 0.67, P = .02), and verbal reasoning abilities (β = 0.79, P<.01) compared with survivors diagnosed at >1 year of age. In multivariable models, restricted to bilateral survivors and adjusted for age at diagnosis, whole brain radiation exposure was significantly associated with poorer performance on tasks of short-term verbal memory (β = -0.003, P = .03) and long-term verbal memory (β = -0.003, P = .01). Reported social attainment was consistent with adult developmental expectations.Adult survivors of retinoblastoma demonstrate few cognitive or social attainment deficits decades following diagnosis and treatment. Findings suggest the potential for neural reorganization following early insult to the visual system as well as vulnerability of the developing brain to low dose radiation exposure. Early intervention and rehabilitation will be important for these patients. Cancer 2014. © 2014 American Cancer Society.
- The impact of cognitive load on delayed recall. [JOURNAL ARTICLE]
- Psychon Bull Rev 2014 Nov 25.
Recent studies have suggested that long-term retention of items studied in a working memory span task depends on the refreshing of memory items-more specifically, on the number of refreshing opportunities. However, it was previously shown that refreshing depends on the cognitive load of the concurrent task introduced in the working memory span task. Thus, cognitive load should determine the long-term retention of items assessed in a delayed-recall test if such retention relies on refreshing. In two experiments, while the amount of refreshing opportunities remained constant, we varied the cognitive load of the concurrent task by either introducing tasks differing in their attentional demands or varying the pace of the concurrent task. To verify that this effect was related to refreshing and not to any maintenance mechanism, we also manipulated the availability of subvocal rehearsal. Replicating previous results, increasing cognitive load reduced immediate recall. This increase also had a detrimental effect on delayed recall. Conversely, the addition of concurrent articulation reduced immediate but not delayed recall. This study shows that both working and episodic memory traces depend on the cognitive load of the concurrent task, whereas the use of rehearsal affects only working memory performance. These findings add further evidence of the dissociation between subvocal rehearsal and attentional refreshing.
- Dynamic relation between working memory capacity and speech recognition in noise during the first 6 months of hearing aid use. [Journal Article]
- Trends Hear 2014.
The present study aimed to investigate the changing relationship between aided speech recognition and cognitive function during the first 6 months of hearing aid use. Twenty-seven first-time hearing aid users with symmetrical mild to moderate sensorineural hearing loss were recruited. Aided speech recognition thresholds in noise were obtained in the hearing aid fitting session as well as at 3 and 6 months postfitting. Cognitive abilities were assessed using a reading span test, which is a measure of working memory capacity, and a cognitive test battery. Results showed a significant correlation between reading span and speech reception threshold during the hearing aid fitting session. This relation was significantly weakened over the first 6 months of hearing aid use. Multiple regression analysis showed that reading span was the main predictor of speech recognition thresholds in noise when hearing aids were first fitted, but that the pure-tone average hearing threshold was the main predictor 6 months later. One way of explaining the results is that working memory capacity plays a more important role in speech recognition in noise initially rather than after 6 months of use. We propose that new hearing aid users engage working memory capacity to recognize unfamiliar processed speech signals because the phonological form of these signals cannot be automatically matched to phonological representations in long-term memory. As familiarization proceeds, the mismatch effect is alleviated, and the engagement of working memory capacity is reduced.
- Banishing the Control Homunculi in Studies of Action Control and Behavior Change. [JOURNAL ARTICLE]
- Perspect Psychol Sci 2014 Sep; 9(5):497-524.
For centuries, human self-control has fascinated scientists and nonscientists alike. Current theories often attribute it to an executive control system. But even though executive control receives a great deal of attention across disciplines, most aspects of it are still poorly understood. Many theories rely on an ill-defined set of "homunculi" doing jobs like "response inhibition" or "updating" without explaining how they do so. Furthermore, it is not always appreciated that control takes place across different timescales. These two issues hamper major advances. Here we focus on the mechanistic basis for the executive control of actions. We propose that at the most basic level, action control depends on three cognitive processes: signal detection, action selection, and action execution. These processes are modulated via error-correction or outcome-evaluation mechanisms, preparation, and task rules maintained in working and long-term memory. We also consider how executive control of actions becomes automatized with practice and how people develop a control network. Finally, we discuss how the application of this unified framework in clinical domains can increase our understanding of control deficits and provide a theoretical basis for the development of novel behavioral change interventions.
- Vocabulary acquisition in aphasia: Modality can matter. [JOURNAL ARTICLE]
- J Neurolinguistics 2014 Nov 1.:42-58.
The present case study investigated modality-specific aspects of novel word acquisition in aphasia. It was prompted by recent aphasia case studies indicating great interindividual variability in the ability to learn and maintain novel words in aphasia. Moreover, two previous case studies revealed a striking effect of input modality by showing effective word learning and re-learning via visual input only (Kohen, Sola, Tuomiranta, Laine, & Martin, 2012; Tuomiranta et al., 2014). The present participant TS with chronic nonfluent aphasia and post-semantic anomia was administered novel word-referent learning tasks. In the first experiment, the learning phase included simultaneous phonological and orthographic input, while the follow-up was probed separately for spoken and written responses. In the second experiment, we studied the effect of four different input and output modality combinations on her ability to learn to name the novel items. In the first experiment, TS's spoken naming performance during the learning phase was just within the range of healthy controls. Maintenance declined and remained outside that range during the whole 6-month follow-up. However, TS maintained the learned words better in written than in spoken naming throughout the follow-up, and in written naming, her maintenance stayed within the control's range up to 8 weeks post-training. The second experiment indicated that the best learning outcome was achieved with orthographic input. Orthographic input combined with orthographic output resulted in fast and accurate learning of the novel words. Interestingly, TS's test profile was opposite to her learning profile, as she repeated better than she read aloud in the linguistic background assessment. The results from the present case highlight the importance of multiple learning channels for word acquisition in individuals with aphasia. Probing the functionality of different input and output channels for learning may also prove valuable in tailoring effective treatment for persons with aphasia.
- Virtual water maze learning in human increases functional connectivity between posterior hippocampus and dorsal caudate. [JOURNAL ARTICLE]
- Hum Brain Mapp 2014 Nov 21.
Recent work has demonstrated that functional connectivity between remote brain regions can be modulated by task learning or the performance of an already well-learned task. Here, we investigated the extent to which initial learning and stable performance of a spatial navigation task modulates functional connectivity between subregions of hippocampus and striatum. Subjects actively navigated through a virtual water maze environment and used visual cues to learn the position of a fixed spatial location. Resting-state functional magnetic resonance imaging scans were collected before and after virtual water maze navigation in two scan sessions conducted 1 week apart, with a behavior-only training session in between. There was a large significant reduction in the time taken to intercept the target location during scan session 1 and a small significant reduction during the behavior-only training session. No further reduction was observed during scan session 2. This indicates that scan session 1 represented initial learning and scan session 2 represented stable performance. We observed an increase in functional connectivity between left posterior hippocampus and left dorsal caudate that was specific to scan session 1. Importantly, the magnitude of the increase in functional connectivity was correlated with offline gains in task performance. Our findings suggest cooperative interaction occurs between posterior hippocampus and dorsal caudate during awake rest following the initial phase of spatial navigation learning. Furthermore, we speculate that the increase in functional connectivity observed during awake rest after initial learning might reflect consolidation-related processing. Hum Brain Mapp, 2014. © 2014 Wiley Periodicals, Inc.
- Cognitive intervention through a training program for picture book reading in community-dwelling older adults: a randomized controlled trial. [JOURNAL ARTICLE]
- BMC Geriatr 2014 Nov 21; 14(1):122.
Non-pharmacological interventions are expected to be important strategies for reducing the age-adjusted prevalence of senile dementia, considering that complete medical treatment for cognitive decline has not yet been developed. From the viewpoint of long-term continuity of activity, it is necessary to develop various cognitive stimulating programs. The aim of this study is to examine the effectiveness of a cognitive intervention through a training program for picture book reading for community-dwelling older adults.Fifty-eight Japanese older participants were divided into the intervention and control groups using simple randomization (n =29 vs 29). In the intervention group, participants took part in a program aimed at learning and mastering methods of picture book reading as a form of cognitive training intervention. The control group listened to lectures about elderly health maintenance. Cognitive tests were conducted individually before and after the programs.The rate of memory retention, computed by dividing Logical Memory delayed recall by immediate recall, showed a significant interaction (p < .05) in analysis of covariance. Simple main effects showed that the rate of memory retention of the intervention group improved after the program completion (p < .05). In the participants with mild cognitive impairment (MCI) examined by Japanese version of the Montreal Cognitive Assessment (MoCA-J) (n =14 vs 15), significant interactions were seen in Trail Making Test-A (p < .01), Trail Making Test-B (p < .05), Kana pick-out test (p < .05) and the Mini-Mental State Examination (p < .05).The intervention effect was found in delayed verbal memory. This program is also effective for improving attention and executive function in those with MCI. The short-term interventional findings suggest that this program might contribute to preventing a decline in memory and executive function.Trial registration: UMIN-CTR: UMIN000014712 (Date of ICMJE and WHO compliant trial information disclosure: 30 July 2014).