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Feng Y, Diego KS, Dong Z, Wick ZC, Page-Harley L, Page-Harley V, Schnipper J, Lamsifer SI, Pennington ZT, Vetere LM, Philipsberg PA, Soler I, Jurkowski A, Rosado CJ, Khan NN, Cai DJ, Shuman T. Distinct changes to hippocampal and medial entorhinal circuits emerge across the progression of cognitive deficits in epilepsy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.12.584697. [PMID: 38559224 PMCID: PMC10979962 DOI: 10.1101/2024.03.12.584697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Temporal lobe epilepsy (TLE) causes pervasive and progressive memory impairments, yet the specific circuit changes that drive these deficits remain unclear. To investigate how hippocampal-entorhinal dysfunction contributes to progressive memory deficits in epilepsy, we performed simultaneous in vivo electrophysiology in hippocampus (HPC) and medial entorhinal cortex (MEC) of control and epileptic mice 3 or 8 weeks after pilocarpine-induced status epilepticus (Pilo-SE). We found that HPC synchronization deficits (including reduced theta power, coherence, and altered interneuron spike timing) emerged within 3 weeks of Pilo-SE, aligning with early-onset, relatively subtle memory deficits. In contrast, abnormal synchronization within MEC and between HPC-MEC emerged later, by 8 weeks after Pilo-SE, when spatial memory impairment was more severe. Furthermore, a distinct subpopulation of MEC layer 3 excitatory neurons (active at theta troughs) was specifically impaired in epileptic mice. Together, these findings suggest that hippocampal-entorhinal circuit dysfunction accumulates and shifts as cognitive impairment progresses in TLE.
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Affiliation(s)
- Yu Feng
- Icahn School of Medicine at Mount Sinai, New York, NY
| | | | - Zhe Dong
- Icahn School of Medicine at Mount Sinai, New York, NY
| | | | | | | | | | | | | | | | | | - Ivan Soler
- Icahn School of Medicine at Mount Sinai, New York, NY
| | | | | | - Nadia N Khan
- Icahn School of Medicine at Mount Sinai, New York, NY
| | - Denise J Cai
- Icahn School of Medicine at Mount Sinai, New York, NY
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2
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Zare M, Rezaei M, Nazari M, Kosarmadar N, Faraz M, Barkley V, Shojaei A, Raoufy MR, Mirnajafi‐Zadeh J. Effect of the closed-loop hippocampal low-frequency stimulation on seizure severity, learning, and memory in pilocarpine epilepsy rat model. CNS Neurosci Ther 2024; 30:e14656. [PMID: 38439573 PMCID: PMC10912795 DOI: 10.1111/cns.14656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 01/22/2024] [Accepted: 02/05/2024] [Indexed: 03/06/2024] Open
Abstract
AIMS In this study, the anticonvulsant action of closed-loop, low-frequency deep brain stimulation (DBS) was investigated. In addition, the changes in brain rhythms and functional connectivity of the hippocampus and prefrontal cortex were evaluated. METHODS Epilepsy was induced by pilocarpine in male Wistar rats. After the chronic phase, a tripolar electrode was implanted in the right ventral hippocampus and a monopolar electrode in medial prefrontal cortex (mPFC). Subjects' spontaneous seizure behaviors were observed in continuous video recording, while the local field potentials (LFPs) were recorded simultaneously. In addition, spatial memory was evaluated by the Barnes maze test. RESULTS Applying hippocampal DBS, immediately after seizure detection in epileptic animals, reduced their seizure severity and duration, and improved their performance in Barnes maze test. DBS reduced the increment in power of delta, theta, and gamma waves in pre-ictal, ictal, and post-ictal periods. Meanwhile, DBS increased the post-ictal-to-pre-ictal ratio of theta band. DBS decreased delta and increased theta coherences, and also increased the post-ictal-to-pre-ictal ratio of coherence. In addition, DBS increased the hippocampal-mPFC coupling in pre-ictal period and decreased the coupling in the ictal and post-ictal periods. CONCLUSION Applying closed-loop, low-frequency DBS at seizure onset reduced seizure severity and improved memory. In addition, the changes in power, coherence, and coupling of the LFP oscillations in the hippocampus and mPFC demonstrate low-frequency DBS efficacy as an antiepileptic treatment, returning LFPs to a seemingly non-seizure state in subjects that received DBS.
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Affiliation(s)
- Meysam Zare
- Department of Physiology, Faculty of Medical SciencesTarbiat Modares UniversityTehranIran
| | - Mahmoud Rezaei
- Department of Physiology, Faculty of Medical SciencesTarbiat Modares UniversityTehranIran
| | - Milad Nazari
- Department of Technology, Electrical EngineeringSharif UniversityTehranIran
| | - Nastaran Kosarmadar
- Department of Physiology, Faculty of Medical SciencesTarbiat Modares UniversityTehranIran
| | - Mona Faraz
- Department of Physiology, Faculty of Medical SciencesTarbiat Modares UniversityTehranIran
| | - Victoria Barkley
- Department of Anesthesia and Pain Management, Toronto General HospitalUniversity Health NetworkTorontoOntarioCanada
| | - Amir Shojaei
- Department of Physiology, Faculty of Medical SciencesTarbiat Modares UniversityTehranIran
| | - Mohammad Reza Raoufy
- Department of Physiology, Faculty of Medical SciencesTarbiat Modares UniversityTehranIran
| | - Javad Mirnajafi‐Zadeh
- Department of Physiology, Faculty of Medical SciencesTarbiat Modares UniversityTehranIran
- Institute for Brain Sciences and CognitionTarbiat Modares UniversityTehranIran
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McDonald AJ, Mott DD. Functional neuroanatomy of amygdalohippocampal interconnections and their role in learning and memory. J Neurosci Res 2016; 95:797-820. [PMID: 26876924 DOI: 10.1002/jnr.23709] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 12/01/2015] [Accepted: 12/14/2015] [Indexed: 01/31/2023]
Abstract
The amygdalar nuclear complex and hippocampal/parahippocampal region are key components of the limbic system that play a critical role in emotional learning and memory. This Review discusses what is currently known about the neuroanatomy and neurotransmitters involved in amygdalo-hippocampal interconnections, their functional roles in learning and memory, and their involvement in mnemonic dysfunctions associated with neuropsychiatric and neurological diseases. Tract tracing studies have shown that the interconnections between discrete amygdalar nuclei and distinct layers of individual hippocampal/parahippocampal regions are robust and complex. Although it is well established that glutamatergic pyramidal cells in the amygdala and hippocampal region are the major players mediating interconnections between these regions, recent studies suggest that long-range GABAergic projection neurons are also involved. Whereas neuroanatomical studies indicate that the amygdala only has direct interconnections with the ventral hippocampal region, electrophysiological studies and behavioral studies investigating fear conditioning and extinction, as well as amygdalar modulation of hippocampal-dependent mnemonic functions, suggest that the amygdala interacts with dorsal hippocampal regions via relays in the parahippocampal cortices. Possible pathways for these indirect interconnections, based on evidence from previous tract tracing studies, are discussed in this Review. Finally, memory disorders associated with dysfunction or damage to the amygdala, hippocampal region, and/or their interconnections are discussed in relation to Alzheimer's disease, posttraumatic stress disorder (PTSD), and temporal lobe epilepsy. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Alexander J McDonald
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, South Carolina
| | - David D Mott
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, South Carolina
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Mauguière F, Corkin S. H.M. never again! An analysis of H.M.’s epilepsy and treatment. Rev Neurol (Paris) 2015; 171:273-81. [DOI: 10.1016/j.neurol.2015.01.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 01/01/2015] [Accepted: 01/27/2015] [Indexed: 12/01/2022]
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5
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Guimãraes CA, Rzezak P, Fuentes D, Franzon RC, Montenegro MA, Cendes F, Valente KD, Guerreiro MM. Memory in children with symptomatic temporal lobe epilepsy. ARQUIVOS DE NEURO-PSIQUIATRIA 2014; 72:184-9. [PMID: 24676434 DOI: 10.1590/0004-282x20130223] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 09/03/2013] [Indexed: 11/21/2022]
Abstract
In children with temporal lobe epilepsy (TLE), memory deficit is not so well understood as it is in adults. The aim of this study was to identify and describe memory deficits in children with symptomatic TLE, and to verify the influence of epilepsy variables on memory. We evaluated 25 children with TLE diagnosed on clinical, EEG and MRI findings. Twenty-five normal children were compared with the patients. All children underwent a neuropsychological assessment to estimate intellectual level, attention, visual perception, handedness, and memory processes (verbal and visual: short-term memory, learning, and delayed recall). The results allowed us to conclude: besides memory deficits, other neuropsychological disturbances may be found in children with TLE such as attention, even in the absence of overall cognitive deficit; the earlier onset of epilepsy, the worse verbal stimuli storage; mesial lesions correlate with impairment in memory storage stage while neocortical temporal lesions correlate with retrieval deficits.
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Affiliation(s)
- Catarina A Guimãraes
- Departamento de Neurologia, Universidade Estadual de Campinas, Campinas, SP, Brazil
| | - Patricia Rzezak
- Instituto de Psiquiatria, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Daniel Fuentes
- Instituto de Psiquiatria, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Renata C Franzon
- Departamento de Neurologia, Universidade Estadual de Campinas, Campinas, SP, Brazil
| | | | - Fernando Cendes
- Departamento de Neurologia, Universidade Estadual de Campinas, Campinas, SP, Brazil
| | - Kette D Valente
- Instituto de Psiquiatria, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Marilisa M Guerreiro
- Departamento de Neurologia, Universidade Estadual de Campinas, Campinas, SP, Brazil
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Pearson JN, Schulz KM, Patel M. Specific alterations in the performance of learning and memory tasks in models of chemoconvulsant-induced status epilepticus. Epilepsy Res 2014; 108:1032-40. [PMID: 24842343 DOI: 10.1016/j.eplepsyres.2014.04.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 04/02/2014] [Accepted: 04/19/2014] [Indexed: 11/29/2022]
Abstract
Cognitive impairment is a common comorbidity in patients with Temporal Lobe Epilepsy (TLE). These impairments, particularly deficits in learning and memory, can be recapitulated in chemoconvulsant models of TLE. Here, we used two relatively low-stress behavioral paradigms, the novel object recognition task (NOR) and a spatial variation, the novel placement recognition task (NPR) to reveal deficits in short and long term memory, in both kainic acid (KA) and pilocarpine (Pilo) treated animals. We found that both KA- and Pilo-induced significant deficits in long term recognition memory but not short term recognition memory. Additionally, KA impaired spatial memory as detected by both NPR and Morris water maze. These deficits were present 1 week after SE. The characterization of memory performance of two chemoconvulsant-models, one of which is considered a surrogate organophosphate, provides an avenue for which targeted cognitive therapeutics can be tested.
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Affiliation(s)
- Jennifer N Pearson
- Neuroscience Program, University of Colorado Anschutz Medical Campus, United States
| | - Kalynn M Schulz
- Department of Psychiatry, University of Colorado Anschutz Medical Campus, United States; Medical Research Service, Veterans Affairs Medical Center, Denver, CO, United States
| | - Manisha Patel
- Neuroscience Program, University of Colorado Anschutz Medical Campus, United States; Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, United States.
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Warren DE, Duff MC, Magnotta V, Capizzano AA, Cassell MD, Tranel D. Long-term neuropsychological, neuroanatomical, and life outcome in hippocampal amnesia. Clin Neuropsychol 2012; 26:335-69. [PMID: 22401298 DOI: 10.1080/13854046.2012.655781] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Focal bilateral hippocampal damage typically causes severe and selective amnesia for new declarative information (facts and events), a cognitive deficit that greatly impacts the ability to live a normal, fully independent life. We describe the case of 1846, a 48-year-old woman with profound hippocampal amnesia following status epilepticus and an associated anoxic episode at age 30. Patient 1846 has undergone extensive neuropsychological testing on many occasions over the 18 years since her injury, and we present data indicating that her memory impairment has remained severe and stable during that time. New, high-resolution, structural MRI studies of 1846's brain reveal substantial bilateral hippocampal atrophy resembling that of other well-known amnesic patients. In spite of severe amnesia 1846 lives a full and mostly independent adult life, facilitated by an extensive social support network of family and friends. Her case provides an example of a rare and unlikely positive outcome in the face of severe memory problems.
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Affiliation(s)
- David E Warren
- Department of Neurology, University of Iowa College of Medicine, Iowa City, IA 52242, USA.
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Abstract
This article focuses on an important neurosurgical problem for which functional imaging may have a role. Temporal lobe epilepsy surgery typically involves removal of much of the anterior medial temporal lobe, which is critical for encoding and retrieval of long-term episodic memories. Verbal episodic memory decline after left anterior temporal lobe resection occurs in 30% to 60% of such patients. Recent studies show that preoperative fMRI can predict the degree of verbal memory change that will occur, and that fMRI improves prediction accuracy when combined with other routine tests. The predictive power of fMRI appears to be at least as good as the Wada memory test, making fMRI a viable noninvasive alternative to the Wada for preoperative assessment.
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Abstract
Partial removal of the anterior temporal lobe (ATL) is a highly effective surgical treatment for intractable temporal lobe epilepsy, yet roughly half of patients who undergo left ATL resection show a decline in language or verbal memory function postoperatively. Two recent studies demonstrate that preoperative fMRI can predict postoperative naming and verbal memory changes in such patients. Most importantly, fMRI significantly improves the accuracy of prediction relative to other noninvasive measures used alone. Addition of language and memory lateralization data from the intracarotid amobarbital (Wada) test did not improve prediction accuracy in these studies. Thus, fMRI provides patients and practitioners with a safe, noninvasive, and well-validated tool for making better-informed decisions regarding elective surgery based on a quantitative assessment of cognitive risk.
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Affiliation(s)
- Jeffrey R Binder
- Department of Neurology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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Binder JR, Sabsevitz DS, Swanson SJ, Hammeke TA, Raghavan M, Mueller WM. Use of preoperative functional MRI to predict verbal memory decline after temporal lobe epilepsy surgery. Epilepsia 2008; 49:1377-94. [PMID: 18435753 DOI: 10.1111/j.1528-1167.2008.01625.x] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Verbal memory decline is a frequent complication of left anterior temporal lobectomy (L-ATL). The goal of this study was to determine whether preoperative language mapping using functional magnetic resonance imaging (fMRI) is useful for predicting which patients are likely to experience verbal memory decline after L-ATL. METHODS Sixty L-ATL patients underwent preoperative language mapping with fMRI, preoperative intracarotid amobarbital (Wada) testing for language and memory lateralization, and pre- and postoperative neuropsychological testing. Demographic, historical, neuropsychological, and imaging variables were examined for their ability to predict pre- to postoperative memory change. RESULTS Verbal memory decline occurred in over 30% of patients. Good preoperative performance, late age at onset of epilepsy, left dominance on fMRI, and left dominance on the Wada test were each predictive of memory decline. Preoperative performance and age at onset together accounted for roughly 50% of the variance in memory outcome (p < 0.001), and fMRI explained an additional 10% of this variance (p <or= 0.003). Neither Wada memory asymmetry nor Wada language asymmetry added additional predictive power beyond these noninvasive measures. DISCUSSION Preoperative fMRI is useful for identifying patients at high risk for verbal memory decline prior to L-ATL surgery. Lateralization of language is correlated with lateralization of verbal memory, whereas Wada memory testing is either insufficiently reliable or insufficiently material-specific to accurately localize verbal memory processes.
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Affiliation(s)
- Jeffrey R Binder
- Department of Neurology, Compreshensive Epilepsy Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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Djordjevic J, Jones-Gotman M, De Sousa K, Chertkow H. Olfaction in patients with mild cognitive impairment and Alzheimer's disease. Neurobiol Aging 2007; 29:693-706. [PMID: 17207898 DOI: 10.1016/j.neurobiolaging.2006.11.014] [Citation(s) in RCA: 247] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 11/10/2006] [Accepted: 11/19/2006] [Indexed: 12/30/2022]
Abstract
Understanding of olfactory dysfunction in Alzheimer's disease (AD) remains limited. In particular, it is not known how early in the course of the disease olfactory deficits occur, and whether they are restricted to identification or involve other aspects of olfaction. We studied olfactory (odor detection thresholds, quality discrimination, and identification) and cognitive (attention, reasoning, memory, naming and fluency) functioning in patients with AD, with mild cognitive impairment (MCI), and in normal elderly control (NEC) participants. MCI patients were impaired in olfactory sensitivity and identification, while a discrimination deficit was accounted for by abnormal thresholds. AD patients were impaired in all three domains, and were worse than the MCI group. Odor discrimination (OD) and identification performance correlated more prominently than detection thresholds with performance on neuropsychological tests. We concluded that deficits in olfactory detection thresholds and identification occur early in AD, before clinical symptoms are fully developed, and decline further over the course of the disease. High detection thresholds, together with impaired identification, may be useful as an early indicator of AD.
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Affiliation(s)
- Jelena Djordjevic
- Montreal Neurological Institute, 3801 University Street, Department of Neurology and Neurosurgery, McGill University, Montreal, H3A 2B4, Québec, Canada.
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Siwak-Tapp CT, Head E, Muggenburg BA, Milgram NW, Cotman CW. Region specific neuron loss in the aged canine hippocampus is reduced by enrichment. Neurobiol Aging 2006; 29:39-50. [PMID: 17092609 PMCID: PMC2198929 DOI: 10.1016/j.neurobiolaging.2006.09.018] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 09/20/2006] [Accepted: 09/30/2006] [Indexed: 11/12/2022]
Abstract
Neuron loss within the hippocampus and entorhinal cortex occurs as a function of age in humans. We first tested the hypothesis that neuron loss occurs in the aged dog. The total unilateral number of neurons in the canine entorhinal cortex and subdivisions of the hippocampus from the left hemisphere were estimated using the optical fractionator. The brains from 5 old (13.0-15.0 years old) and 5 young (3.4-4.5 years old) beagle dogs were analyzed. The hilus of the hippocampus showed a significant loss of neurons (approximately 30%) in the aged dog brain compared to young. Differences were not detected in the remaining hippocampal subfields and entorhinal cortex. We further tested the hypothesis that an antioxidant fortified food or behavioral enrichment would reduce the age-related loss of hilar neurons. Behaviorally enriched aged dogs had more neurons in the hilus (approximately 18%) compared to aged controls. These results suggest that the aged canine hippocampus in the left hemisphere shows selective neuron loss and that behavioral enrichment may reduce this loss.
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Affiliation(s)
- Christina T Siwak-Tapp
- Institute for Brain Aging and Dementia, University of California, 1226 Gillespie Neuroscience Research Facility, Irvine, CA 92697-4540, USA.
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Martins S, Guillery-Girard B, Jambaqué I, Dulac O, Eustache F. How children suffering severe amnesic syndrome acquire new concepts? Neuropsychologia 2006; 44:2792-805. [PMID: 16870216 DOI: 10.1016/j.neuropsychologia.2006.05.022] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2005] [Revised: 03/21/2006] [Accepted: 05/21/2006] [Indexed: 10/24/2022]
Abstract
Recent studies revealed that children with developmental amnesia acquired new semantic information. However, they failed to investigate the growth of such knowledge during childhood, and they did not bring evidence concerning the putative role of residual episodic memory in semantic acquisition. This prospective study sought to clarify this issue by assessing both semantic and episodic memory in two amnesic children (RH and KF) with different neuropsychological profiles. We thus applied errorless semantic learning and vanishing cues methods, together with assessments of episodic memory using original recognition tasks within the same protocol. Results demonstrated learning and long-lasting maintenance of multicomponent concepts (comprising labels, categories and features) in both amnesic children. Importantly, episodic memory assessments revealed differential residual abilities in these children, which may account for their respective profiles of semantic acquisition. Thus, RH, who demonstrated residual episodic abilities, acquired normally. However, the learning of KF, who had a massive impairment of episodic memory, remained slower than her controls. In conclusion, even though an episodic impairment may slacken new semantic learning, our research provides new evidence for the de novo acquisition of semantic concepts in childhood amnesic syndrome and strengthens the idea that semantic learning can occur without any recruitment of episodic memory.
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Affiliation(s)
- Sylvie Martins
- Inserm, EPHE, Université de Caen, Unité E0218, GIP Cyceron, CHU Côte de Nacre, 14033 Caen Cedex, France
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Jambaqué I, Hertz-Pannier L, Mikaeloff Y, Martins S, Peudenier S, Dulac O, Chiron C. Severe memory impairment in a child with bihippocampal injury after status epilepticus. Dev Med Child Neurol 2006; 48:223-6. [PMID: 16483400 DOI: 10.1017/s0012162206000478] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/17/2005] [Indexed: 11/06/2022]
Abstract
Epilepsy may contribute to memory deficits in children, but these deficits are generally mild. We describe the neuropsychological profile of a female who had prolonged status epilepticus at 5 years of age, and then developed temporal lobe epilepsy. Brain magnetic resonance imaging 1 month after the onset of status epilepticus showed marked bilateral hippocampal atrophy that seemed disproportionate to the mild cortico-subcortical atrophy. At the age of 7 years, this child had cognitive impairment (an IQ of 62), which particularly affected her memory. This included short-term memory, and immediate and delayed memory deficits for verbal and visual materials that had a profound impact on everyday life. This observation demonstrates that severe status epilepticus can cause predominant bilateral hippocampal atrophy in childhood. In contrast with children who develop such damage after anoxia, this may result in general cognitive impairment but also in more severe episodic memory deficit.
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Affiliation(s)
- Isabelle Jambaqué
- Laboratoire Cognition et Développement, Institut de Psychologie, Université Paris Descartes, Paris V, CNRS UMR 8605, 92774 Boulogne Billancourt, France.
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Detour J, Schroeder H, Desor D, Nehlig A. A 5-month period of epilepsy impairs spatial memory, decreases anxiety, but spares object recognition in the lithium-pilocarpine model in adult rats. Epilepsia 2005; 46:499-508. [PMID: 15816943 DOI: 10.1111/j.0013-9580.2005.38704.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE In temporal lobe epilepsy (TLE), interictal behavioral disorders affect patients' quality of life. Therefore we studied long-term behavioral impairments in the lithium-pilocarpine (li-pilo) model of TLE. METHODS Eleven li-pilo adult rats exhibiting spontaneous recurrent seizures (SRSs) during 5 months were compared with 11 li-saline rats. Spatial working memory was tested in a radial arm maze (RAM), anxiety in an elevated plus-maze (EPM), and nonspatial working memory in an object-recognition paradigm. Neuronal loss was assessed on thionine brain sections after behavioral testing. RESULTS In the RAM, the time to complete each session and the number of errors per session decreased over a 5-day period in li-saline rats but remained constant and significantly higher in li-pilo rats. In the EPM, the number of entries in and time spent on open arms were significantly higher in li-pilo than li-saline rats. In the object-recognition task, the two groups exhibited a comparable novelty preference for the new object. Neuronal loss reached 47-90% in hilus, CA1, amygdala, and piriform and entorhinal cortex. CONCLUSIONS In li-pilo rats having experienced SRS for 5 months, performance in the object-recognition task is spared, which suggests that object discrimination remains relatively intact despite extensive damage. Neuronal loss in regions mediating memory and anxiety, such as hippocampus, entorhinal cortex, and amygdala, may relate to impaired spatial orientation and decreased anxiety.
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Affiliation(s)
- Julien Detour
- INSERM U398, Faculty of Medicine, Strasbourg, France.
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Abstract
Temporal lobe epilepsy (TLE) patients are frequently afflicted with deficits in spatial and other forms of declarative memory. This impairment is likely associated with the medial temporal lobe, which suffers widespread damage in the disease. Physiological and lesion studies, as well as examinations of the complex connectivity of the medial temporal lobe in animals and humans, have identified the entorhinal cortex (EC) as a key structure in the function and dysfunction of this brain region. Lesions in EC layer III, which normally provides monosynaptic input to area CA1 of the hippocampus, frequently occur in TLE and may be causally related to the memory impairments seen in the disease. Lesions that are initially largely restricted to EC layer III can be produced in rats by focal intra-entorhinal injections of 'indirect excitotoxins' such as aminooxyacetic acid or gamma-acetylenic GABA. These animals eventually show more extensive neurodegeneration in temporal lobe structures and, after a latent period, exhibit spontaneously recurring seizure activity. These progressive features, which may mimic events that occur in TLE, provide new opportunities to explore the role of the EC in memory deficits associated with TLE. These animals will also be useful for evaluating new treatment strategies that focus on the prevention of pathological events in the EC.
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Affiliation(s)
- Robert Schwarcz
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, P.O. Box 21247, Baltimore, MD 21228, USA.
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