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Ceskoslovenska Fysiologie 2010In the introduction we summarized basic information about memory and indicated studies, which were milestones in the study of memory. Basic studies of memory are... (Review)
Review
In the introduction we summarized basic information about memory and indicated studies, which were milestones in the study of memory. Basic studies of memory are reviewed and neurobiological approach is highlighted. The aim of this investigation is to find the relationship among basic facts about memory and what are the underlying mechanisms. This study deals with the participating brain structures, what happens on the synapses and how neurons are influenced. Substantial part of the review is devoted to synaptic plasticity and long-lasting potentiation (LTP). They represent the in vitro approaches, which help to discover mechanisms that participate in memory. The decisive role of AMPA and NMDA receptors and signaling cascades for memory are presented. The role of hippocampus and parahippocampal formation for memory storage is described in more details. Processes of memory consolidation and reconsolidation are presented as well as mechanisms, which modulate memory processes. The review is closed by the index theory, which explains complicated situation in storage and retrieval of memory.
Topics: Animals; Hippocampus; Humans; Learning; Long-Term Potentiation; Memory; Neuronal Plasticity; Parahippocampal Gyrus
PubMed: 21254659
DOI: No ID Found -
Nature Reviews. Neuroscience Oct 2012Although the perirhinal cortex (PRC), parahippocampal cortex (PHC) and retrosplenial cortex (RSC) have an essential role in memory, the precise functions of these areas... (Review)
Review
Although the perirhinal cortex (PRC), parahippocampal cortex (PHC) and retrosplenial cortex (RSC) have an essential role in memory, the precise functions of these areas are poorly understood. Here, we review the anatomical and functional characteristics of these areas based on studies in humans, monkeys and rats. Our Review suggests that the PRC and PHC-RSC are core components of two separate large-scale cortical networks that are dissociable by neuroanatomy, susceptibility to disease and function. These networks not only support different types of memory but also appear to support different aspects of cognition.
Topics: Animals; Cerebral Cortex; Humans; Memory; Nerve Net; Neural Pathways; Parahippocampal Gyrus
PubMed: 22992647
DOI: 10.1038/nrn3338 -
Epilepsia Dec 2009Lesion-negative refractory partial epilepsy is a major challenge in the assessment of patients for potential surgery. Finding a potential epileptogenic lesion simplifies... (Comparative Study)
Comparative Study
PURPOSE
Lesion-negative refractory partial epilepsy is a major challenge in the assessment of patients for potential surgery. Finding a potential epileptogenic lesion simplifies assessment and is associated with good outcome. Here we describe imaging features of subtle parahippocampal dysplasia in five cases that were initially assessed as having imaging-negative frontal or temporal lobe epilepsy.
METHODS
We analyzed the clinical and imaging features of five patients with seizures from the parahippocampal region.
RESULTS
Five patients had subtle but distinctive magnetic resonance imaging (MRI) abnormalities in the parahippocampal gyrus. This was a unilateral signal abnormality in the parahippocampal white matter extending into gray matter on heavily T(1)- and T(2)-weighted images with relative preservation of the gray-white matter boundary on T(1)-weighted volume sequences. Only one of these patients had typical electroclinical unilateral temporal lobe epilepsy (TLE); one mimicked frontal lobe epilepsy, two showed bitemporal seizures, and one had unlocalized partial seizures. All have had surgery; four are seizure-free (one has occasional auras only, follow-up 6 months to 10 years), and one has a >50% seizure reduction. Histopathologic evaluation suggested dysplastic features in the surgical specimens in all.
DISCUSSION
In patients with lesion-negative partial epilepsy with frontal or temporal semiology, or in cases with apparent bitemporal seizures, subtle parahippocampal abnormalities should be carefully excluded. Recognizing the MRI findings of an abnormal parahippocampal gyrus can lead to successful surgery without invasive monitoring, despite apparently incongruent electroclinical features.
Topics: Adult; Disease-Free Survival; Electroencephalography; Entorhinal Cortex; Epilepsies, Partial; Epilepsy, Frontal Lobe; Epilepsy, Temporal Lobe; Female; Functional Laterality; Humans; Magnetic Resonance Imaging; Male; Malformations of Cortical Development; Middle Aged; Neuropsychological Tests; Parahippocampal Gyrus
PubMed: 19453720
DOI: 10.1111/j.1528-1167.2009.02103.x -
ELife Aug 2016Anticipating the future is a key motif of the brain, possibly supported by mental simulation of upcoming events. Rodent single-cell recordings suggest the ability of...
Anticipating the future is a key motif of the brain, possibly supported by mental simulation of upcoming events. Rodent single-cell recordings suggest the ability of spatially tuned cells to represent subsequent locations. Grid-like representations have been observed in the human entorhinal cortex during virtual and imagined navigation. However, hitherto it remains unknown if grid-like representations contribute to mental simulation in the absence of imagined movement. Participants imagined directions between building locations in a large-scale virtual-reality city while undergoing fMRI without re-exposure to the environment. Using multi-voxel pattern analysis, we provide evidence for representations of absolute imagined direction at a resolution of 30° in the parahippocampal gyrus, consistent with the head-direction system. Furthermore, we capitalize on the six-fold rotational symmetry of grid-cell firing to demonstrate a 60° periodic pattern-similarity structure in the entorhinal cortex. Our findings imply a role of the entorhinal grid-system in mental simulation and future thinking beyond spatial navigation.
Topics: Action Potentials; Adolescent; Adult; Entorhinal Cortex; Grid Cells; Humans; Imagination; Magnetic Resonance Imaging; Male; Models, Neurological; Parahippocampal Gyrus; Space Perception; Spatial Memory; Spatial Navigation; Young Adult
PubMed: 27572056
DOI: 10.7554/eLife.17089 -
The American Journal of Psychiatry Feb 2003Neuropathological evidence suggests that the earliest changes in Alzheimer's disease selectively affect the parahippocampal regions of the brain. This study was... (Comparative Study)
Comparative Study
OBJECTIVE
Neuropathological evidence suggests that the earliest changes in Alzheimer's disease selectively affect the parahippocampal regions of the brain. This study was conducted to determine if otherwise healthy elderly subjects with mild cognitive impairment had structural volume deficits affecting the parahippocampal gyrus.
METHOD
Magnetic resonance imaging (MRI) was used to compare global and regional brain volumes in 21 subjects with mild cognitive deficits defined according to the criteria for aging-associated cognitive decline, 22 cognitively intact comparison subjects, and 12 patients with Alzheimer's disease.
RESULTS
Compared with the cognitively intact subjects, the subjects with aging-associated cognitive decline had a significantly smaller mean volume of the right parahippocampal gyrus. The subjects with aging-associated cognitive decline had a mean parahippocampal volume that was intermediate between that of the Alzheimer's disease patients and that of the cognitively intact subjects.
CONCLUSIONS
Parahippocampal atrophy underlies the observed cognitive deficits in aging-associated cognitive decline. These findings support the hypothesis that aging-associated cognitive decline represents a preclinical stage of Alzheimer's disease.
Topics: Age Factors; Aged; Aging; Alzheimer Disease; Atrophy; Brain; Cognition Disorders; Functional Laterality; Geriatric Assessment; Humans; Magnetic Resonance Imaging; Middle Aged; Parahippocampal Gyrus
PubMed: 12562591
DOI: 10.1176/appi.ajp.160.2.379 -
NMR in Biomedicine Dec 2015Previous investigations have indicated that the default-mode network (DMN) is highly involved in memory processing in the parahippocampal gyrus (PHC). However, because...
Previous investigations have indicated that the default-mode network (DMN) is highly involved in memory processing in the parahippocampal gyrus (PHC). However, because of susceptibility-related signal loss, parahippocampal activation in the DMN is difficult to detect in resting-state functional MRI experiments that are conducted using a 3.0-T MRI scanner. This study investigated the magnetic field gradients of various brain regions and attempted to compensate for signal loss in the PHC using an optimized slice orientation. The field gradients, signal intensities and DMN functional connectivity (FC) of the PHC were investigated using datasets acquired from 18 healthy volunteers. The results show that the field gradient component parallel to the main magnetic field dominates the PHC. The results indicate that the signal intensities and FC of the DMN are significantly low in the PHC when the slice orientation of the imaging plane is transversal. Whether the voxel dimension is isotropic or anisotropic exerts a minimal effect in altering the slice orientation dependence. In conclusion, the results of this study support the selection of the coronal or sagittal planes for imaging of the DMN.
Topics: Adult; Algorithms; Brain Mapping; Female; Humans; Image Enhancement; Imaging, Three-Dimensional; Magnetic Resonance Imaging; Male; Nerve Net; Parahippocampal Gyrus; Reproducibility of Results; Rest; Sensitivity and Specificity; Signal-To-Noise Ratio
PubMed: 26510634
DOI: 10.1002/nbm.3435 -
Current Biology : CB Aug 2011Two recent imaging studies have shed new light on information representation in human parahippocampal cortex. Despite their different approaches, the two studies both...
Two recent imaging studies have shed new light on information representation in human parahippocampal cortex. Despite their different approaches, the two studies both support the view that this brain region represents space at an elementary level.
Topics: Humans; Magnetic Resonance Imaging; Parahippocampal Gyrus; Vision, Ocular
PubMed: 21820624
DOI: 10.1016/j.cub.2011.06.023 -
NeuroImage May 2008Temporal lobe epilepsy (TLE) is associated with disrupted memory function. The structural changes underlying this memory impairment have not been demonstrated previously...
INTRODUCTION
Temporal lobe epilepsy (TLE) is associated with disrupted memory function. The structural changes underlying this memory impairment have not been demonstrated previously with tractography.
METHODS
We performed a tractography analysis of diffusion magnetic resonance imaging scans in 18 patients with unilateral TLE undergoing presurgical evaluation, and in 10 healthy controls. A seed region in the anterior parahippocampal gyrus was selected from which to trace the white matter connections of the medial temporal lobe. A correlation analysis was carried out between volume and mean fractional anisotropy (FA) of the connections, and pre-operative material specific memory performance.
RESULTS
There was no significant difference between the left and right sided connections in controls. In the left TLE patients, the connected regions ipsilateral to the epileptogenic region were found to be significantly reduced in volume and mean FA compared with the contralateral region, and left-sided connections in control subjects. Significant correlations were found in left TLE patients between left and right FA, and verbal and non-verbal memory respectively.
CONCLUSION
Tractography demonstrated the alteration of white matter pathways that may underlie impaired memory function in TLE. A detailed knowledge of the integrity of these connections may be useful in predicting memory decline in chronic temporal lobe epilepsy.
Topics: Adult; Data Interpretation, Statistical; Diffusion Magnetic Resonance Imaging; Electroencephalography; Epilepsy, Temporal Lobe; Female; Functional Laterality; Humans; Magnetic Resonance Imaging; Male; Memory Disorders; Middle Aged; Neuropsychological Tests; Parahippocampal Gyrus; Seizures
PubMed: 18314352
DOI: 10.1016/j.neuroimage.2007.12.046 -
Hippocampus 2004There has been growing interest in the differential role of medial temporal lobe structures in learning and memory. The goal of the present study was to clarify how...
There has been growing interest in the differential role of medial temporal lobe structures in learning and memory. The goal of the present study was to clarify how lesions of hippocampus, parahippocampal gyrus, and amygdala interfere with associative learning and memory. Thirty subjects with pharmacoresistant medial temporal lobe epilepsy (TLE) and temporal lobe removal were compared with 30 matched healthy control subjects. A set of neuropsychological test measures and an associative learning task requiring the learning and recall of objects and faces were administered. The lesions of hippocampus, parahippocampal gyrus, amygdala, and fusiform gyrus of TLE subjects were determined by three-dimensional magnetic resonance imaging (3-D MRI) volumetric assessment. The results indicate that TLE subjects with combined large hippocampal lesions, large parahippocampal gyrus (i.e., perirhinal/entorhinal) lesions, and large amygdala lesions learned and recalled the associative task significantly worse than control subjects or subjects with small lesions of the hippocampus, parahippocampal gyrus, and amygdala. Regression analysis revealed that larger lesions of the parahippocampal gyrus (i.e., perirhinal/entorhinal cortices) were significantly related to increasing deficits on the task, and that hippocampal and amygdala lesion size did not significantly improve the prediction. Our results suggest that perirhinal and entorhinal cortices may contribute predominantly to the associative learning and recall of objects and faces.
Topics: Adult; Amygdala; Association Learning; Epilepsy, Temporal Lobe; Female; Hippocampus; Humans; Imaging, Three-Dimensional; Magnetic Resonance Imaging; Male; Memory; Memory Disorders; Models, Neurological; Neural Pathways; Neuropsychological Tests; Parahippocampal Gyrus; Recognition, Psychology
PubMed: 15318335
DOI: 10.1002/hipo.10216 -
Brain and Cognition Mar 2010Working memory is devoted to the temporary storage and on-line manipulation of information. Recently, an integrative system termed the episodic buffer has been proposed...
Working memory is devoted to the temporary storage and on-line manipulation of information. Recently, an integrative system termed the episodic buffer has been proposed to integrate and hold information being entered or retrieved from episodic memory. Although the brain system supporting such an integrative buffer is still in debate, the medial temporal lobe appears to be a promising candidate for the maintenance of bound information. In the current work, binding was assessed by comparing two conditions in which participants had to retain three letters and three spatial locations presented either bound or separate. At the behavioral level, lower performance was found for bound information than for separate information. When contrasting the two conditions, activation in the right parahippocampal gyrus was greater for the encoding and maintenance of bound information. No activation was observed in the medial temporal lobe during the retrieval of bound information. Together, our results suggest that the parahippocampal gyrus may underlie the integrative and maintenance functions of the episodic buffer.
Topics: Adult; Female; Functional Laterality; Humans; Magnetic Resonance Imaging; Male; Memory, Short-Term; Neuropsychological Tests; Parahippocampal Gyrus; Young Adult
PubMed: 19837500
DOI: 10.1016/j.bandc.2009.09.009