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Human Brain Mapping Feb 2024The hippocampus and parahippocampal gyrus have been implicated as part of a tinnitus network by a number of studies. These structures are usually considered in the... (Review)
Review
The hippocampus and parahippocampal gyrus have been implicated as part of a tinnitus network by a number of studies. These structures are usually considered in the context of a "limbic system," a concept typically invoked to explain the emotional response to tinnitus. Despite this common framing, it is not apparent from current literature that this is necessarily the main functional role of these structures in persistent tinnitus. Here, we highlight a different role that encompasses their most commonly implicated functional position within the brain-that is, as a memory system. We consider tinnitus as an auditory object that is held in memory, which may be made persistent by associated activity from the hippocampus and parahippocampal gyrus. Evidence from animal and human studies implicating these structures in tinnitus is reviewed and used as an anchor for this hypothesis. We highlight the potential for the hippocampus/parahippocampal gyrus to facilitate maintenance of the memory of the tinnitus percept via communication with auditory cortex, rather than (or in addition to) mediating emotional responses to this percept.
Topics: Animals; Humans; Tinnitus; Hippocampus; Parahippocampal Gyrus; Limbic System; Auditory Cortex
PubMed: 38376166
DOI: 10.1002/hbm.26627 -
Annals of the New York Academy of... Jun 2000The human parahippocampal gyrus forms a large part of the limbic lobe along the ventromedial part of the temporal cortical mantle. It is a variable and complicated... (Review)
Review
The human parahippocampal gyrus forms a large part of the limbic lobe along the ventromedial part of the temporal cortical mantle. It is a variable and complicated cortex in terms of structure, and the latter is aggravated further by interfaces with the anterior insula anteriorly and the cingulate gyrus and occipital lobe posteriorly. Additional complications relate to its lateral border with the temporal cortex and especially the sulcal configurations that define this junction. The rhinal sulcus, which separates parahippocampal and temporal cortices in other species, including the anthropoid apes, is either lacking or rudimentary in the human brain. Thus, defining this junction requires cytoarchitectural examination and precludes the use of mere inspection of sulcal existing patterns. The cortical areas that form the parahippocampal gyrus are vulnerable to pathological changes in Alzheimer's disease (AD), and its entorhinal and perirhinal subdivisions are both the most heavily damaged cortical areas and the focus for disease onset. The neurons that acquire neurofibrillary tangles (NFTs) occupy the junction of the isocortical mantle with the limbic cortical mantle, but share, or partially share, a vulnerability phenotype with large neurons in both domains. The differential expression of this phenotype across time creates the false impression of NFT spread in cross-sectional comparisons of AD brains. The questions of what this phenotype is and why it is expressed first in the perirhinal and entorhinal cortices of the parahippocampal gyrus are the central molecular biological/neuroanatomical questions in understanding the etiology of AD.
Topics: Alzheimer Disease; Animals; Humans; Parahippocampal Gyrus; Reference Values; Terminology as Topic
PubMed: 10911879
DOI: 10.1111/j.1749-6632.2000.tb06731.x -
Annual Review of Neuroscience 2004The medial temporal lobe includes a system of anatomically related structures that are essential for declarative memory (conscious memory for facts and events). The... (Review)
Review
The medial temporal lobe includes a system of anatomically related structures that are essential for declarative memory (conscious memory for facts and events). The system consists of the hippocampal region (CA fields, dentate gyrus, and subicular complex) and the adjacent perirhinal, entorhinal, and parahippocampal cortices. Here, we review findings from humans, monkeys, and rodents that illuminate the function of these structures. Our analysis draws on studies of human memory impairment and animal models of memory impairment, as well as neurophysiological and neuroimaging data, to show that this system (a) is principally concerned with memory, (b) operates with neocortex to establish and maintain long-term memory, and (c) ultimately, through a process of consolidation, becomes independent of long-term memory, though questions remain about the role of perirhinal and parahippocampal cortices in this process and about spatial memory in rodents. Data from neurophysiology, neuroimaging, and neuroanatomy point to a division of labor within the medial temporal lobe. However, the available data do not support simple dichotomies between the functions of the hippocampus and the adjacent medial temporal cortex, such as associative versus nonassociative memory, episodic versus semantic memory, and recollection versus familiarity.
Topics: Animals; Entorhinal Cortex; Hippocampus; Humans; Memory; Memory Disorders; Models, Animal; Models, Neurological; Neural Pathways; Parahippocampal Gyrus; Temporal Lobe
PubMed: 15217334
DOI: 10.1146/annurev.neuro.27.070203.144130 -
Epilepsy Research Aug 2022Intraoperative electrocorticography (ECoG) in the parahippocampal gyrus is sometimes used as a substitute for intraoperative ECoG in the hippocampus. This study aimed to...
PURPOSE
Intraoperative electrocorticography (ECoG) in the parahippocampal gyrus is sometimes used as a substitute for intraoperative ECoG in the hippocampus. This study aimed to elucidate the validity of parahippocampal ECoG as an indicator of hippocampal epileptogenicity.
METHODS
We retrospectively identified 10 patients with drug-resistant unilateral mesial temporal lobe epilepsy who achieved Engel class I or II after anteromedial temporal lobectomy. Intraoperative ECoG was recorded in the parahippocampal gyrus and hippocampal alveus at sevoflurane concentrations of 1.5-3.0%. We sought to identify the sevoflurane proconvulsant effects on spikes and high-frequency oscillations (HFOs) on spikes in the epileptogenic area. The number of spikes and number of HFOs superimposed on spikes were counted in ECoG recordings of the parahippocampal gyrus, hippocampal alveus, and lateral temporal lobe, and analyzed using two-way repeated-measures analysis of variance.
RESULTS
The number of spikes and number of HFOs superimposed on spikes significantly increased as the sevoflurane concentration increased in both the hippocampal alveus and parahippocampal gyrus (spike, p < 0.001; ripple, p < 0.001; Fast ripple (FR), p < 0.001), and the pattern of increase was similar in these two areas. The number of spikes and number of HFOs on spikes were statistically higher in the hippocampal alveus than in the parahippocampal gyrus (spike, p = 0.004; ripple, p = 0.005; FR, p = 0.001). There were almost no spikes or HFOs on spikes in the lateral temporal lobe at sevoflurane concentrations in the range of 1.5-2.5%.
CONCLUSIONS
Intraoperative ECoG in the parahippocampal gyrus can serve as an indicator of hippocampal epileptogenicity.
Topics: Drug Resistant Epilepsy; Electrocorticography; Electroencephalography; Epilepsy, Temporal Lobe; Hippocampus; Humans; Parahippocampal Gyrus; Retrospective Studies; Sevoflurane
PubMed: 35661574
DOI: 10.1016/j.eplepsyres.2022.106950 -
World Neurosurgery Apr 2021The parahippocampal gyrus is understood to have a role in high cognitive functions including memory encoding and retrieval and visuospatial processing. A detailed...
BACKGROUND
The parahippocampal gyrus is understood to have a role in high cognitive functions including memory encoding and retrieval and visuospatial processing. A detailed understanding of the exact location and nature of associated white tracts could significantly improve postoperative morbidity related to declining capacity. Through diffusion tensor imaging-based fiber tracking validated by gross anatomic dissection as ground truth, we have characterized these connections based on relationships to other well-known structures.
METHODS
Diffusion imaging from the Human Connectome Project for 10 healthy adult controls was used for tractography analysis. We evaluated the parahippocampal gyrus as a whole based on connectivity with other regions. All parahippocampal gyrus tracts were mapped in both hemispheres, and a lateralization index was calculated with resultant tract volumes.
RESULTS
We identified 2 connections of the parahippocampal gyrus: inferior longitudinal fasciculus and cingulum. Lateralization of the cingulum was detected (P < 0.05).
CONCLUSIONS
The parahippocampal gyrus is an important center for memory processing. Subtle differences in executive functioning following surgery for limbic tumors may be better understood in the context of the fiber-bundle anatomy highlighted by this study.
Topics: Adult; Connectome; Diffusion Tensor Imaging; Female; Humans; Male; Middle Aged; Nerve Net; Parahippocampal Gyrus; White Matter
PubMed: 33412321
DOI: 10.1016/j.wneu.2020.12.136 -
Annals of the New York Academy of... Jun 2000Limbic seizures have often been attributed to pathology in the hippocampus, such as the well described condition termed Ammon's Horn sclerosis, in which many of the... (Review)
Review
Limbic seizures have often been attributed to pathology in the hippocampus, such as the well described condition termed Ammon's Horn sclerosis, in which many of the hippocampal principal cells have degenerated. However, several studies in both the clinical and basic literature indicate that the parahippocampal region may also play an important role. This region sustains a characteristic pattern of damage in most animal models of epilepsy that is similar to that identified in humans with intractable temporal lobe epilepsy. Perhaps the most striking aspect of parahippocampal pathology is the marked loss of neurons in layer III of the entorhinal cortex. The similarity of cell loss in layer III and cell loss in the hilus of the dentate gyrus is compared, as is the characteristic resistance of layer II neurons and dentate granule cells. Cellular electrophysiological results are used as a basis for the hypothesis that synaptic inhibition plays a role in the relative vulnerability of these neurons. Studies of neurogenesis in both areas is also discussed. It is proposed that this may be an additional factor that influences vulnerability in these areas.
Topics: Animals; Dentate Gyrus; Epilepsy; Humans; Neurons; Parahippocampal Gyrus; Reference Values
PubMed: 10911882
DOI: 10.1111/j.1749-6632.2000.tb06734.x -
Journal of Behavioral Addictions Mar 2022Problematic mobile phone use (PMPU) is prevalent and increases the risk for a variety of health problems. However, few studies have explored the neural mechanisms that...
Functional connectivity between the parahippocampal gyrus and the middle temporal gyrus moderates the relationship between problematic mobile phone use and depressive symptoms: Evidence from a longitudinal study.
BACKGROUND AND AIM
Problematic mobile phone use (PMPU) is prevalent and increases the risk for a variety of health problems. However, few studies have explored the neural mechanisms that might render adolescents more or less vulnerable. Here, we aimed to identify whether PMPU is associated with depressive symptoms and whether this relationship is moderated by intrinsic functional connectivity (iFC) which is associated with PMPU.
METHODS
In this longitudinal study, we included 238 students (mean age = 19.05, SD = 0.81) that came from a university in Hefei, China. They all finished MRI scans at baseline and completed questionnaires both at baseline and 1 year later. A self-rating questionnaire for adolescent problematic mobile phone use and depression anxiety stress scale-21 were used to assess PMPU and depressive symptoms. We first assessed the relationship between PMPU and depressive symptoms using an autoregressive cross-lagged model. Then, we detected the brain regions that were associated with PMPU. Moreover, the neuroimaging results were extracted to explore whether the iFC of these brain regions moderated the relationship between PMPU and depression.
RESULTS
Consistent with our hypotheses, PMPU was positively associated with depressive symptoms, and the relationship between PMPU and depressive symptoms was moderated by iFC of the left parahippocampal gyrus-right middle temporal gyrus both at baseline and after 1 year (β = 0.554, P = 0.003; β = 0.463, P = 0.016, respectively).
CONCLUSIONS
These results advance the understanding of PMPU and suggest that iFC of the left parahippocampal gyrus-right middle temporal gyrus may be a neurobiological contributor to its relationship with depressive symptoms.
Topics: Adolescent; Adult; Cell Phone Use; Depression; Humans; Longitudinal Studies; Parahippocampal Gyrus; Temporal Lobe; Young Adult
PubMed: 35049522
DOI: 10.1556/2006.2021.00090 -
Brain Structure & Function Jan 2011The main aim of the present study was to compare volume differences in the hippocampus and parahippocampal gyrus as biomarkers of Alzheimer's disease (AD). Based on the...
The main aim of the present study was to compare volume differences in the hippocampus and parahippocampal gyrus as biomarkers of Alzheimer's disease (AD). Based on the previous findings, we hypothesized that there would be significant volume differences between cases of healthy aging, amnestic mild cognitive impairment (aMCI), and mild AD. Furthermore, we hypothesized that there would be larger volume differences in the parahippocampal gyrus than in the hippocampus. In addition, we investigated differences between the anterior, middle, and posterior parts of both structures. We studied three groups of participants: 18 healthy participants without memory decline, 18 patients with aMCI, and 18 patients with mild AD. 3 T T1-weighted MRI scans were acquired and gray matter volumes of the anterior, middle, and posterior parts of both the hippocampus and parahippocampal gyrus were measured using a manual tracing approach. Volumes of both the hippocampus and parahippocampal gyrus were significantly different between the groups in the following order: healthy>aMCI>AD. Volume differences between the groups were relatively larger in the parahippocampal gyrus than in the hippocampus, in particular, when we compared healthy with aMCI. No substantial differences were found between the anterior, middle, and posterior parts of both structures. Our results suggest that parahippocampal volume discriminates better than hippocampal volume between cases of healthy aging, aMCI, and mild AD, in particular, in the early phase of the disease. The present results stress the importance of parahippocampal atrophy as an early biomarker of AD.
Topics: Aged; Alzheimer Disease; Atrophy; Biomarkers; Brain Mapping; Hippocampus; Humans; Magnetic Resonance Imaging; Male; Memory Disorders; Middle Aged; Parahippocampal Gyrus
PubMed: 20957494
DOI: 10.1007/s00429-010-0283-8 -
PloS One 2018A large body of literature links risk of cognitive decline, mild cognitive impairment (MCI) and dementia with Type 2 Diabetes (T2D) or pre-diabetes. Accumulating...
Parahippocampal gyrus expression of endothelial and insulin receptor signaling pathway genes is modulated by Alzheimer's disease and normalized by treatment with anti-diabetic agents.
A large body of literature links risk of cognitive decline, mild cognitive impairment (MCI) and dementia with Type 2 Diabetes (T2D) or pre-diabetes. Accumulating evidence implicates a close relationship between the brain insulin receptor signaling pathway (IRSP) and the accumulation of amyloid beta and hyperphosphorylated and conformationally abnormal tau. We showed previously that the neuropathological features of Alzheimer's disease (AD were reduced in patients with diabetes who were treated with insulin and oral antidiabetic medications. To understand better the neurobiological substrates of T2D and T2D medications in AD, we examined IRSP and endothelial cell markers in the parahippocampal gyrus of controls (N = 30), of persons with AD (N = 19), and of persons with AD and T2D, who, in turn, had been treated with anti-diabetic drugs (insulin and or oral agents; N = 34). We studied the gene expression of selected members of the IRSP and selective endothelial cell markers in bulk postmortem tissue from the parahippocampal gyrus and in endothelial cell enriched isolates from the same brain region. The results indicated that there are considerable abnormalities and reductions in gene expression (bulk tissue homogenates and endothelial cell isolates) in the parahippocampal gyri of persons with AD that map directly to genes associated with the microvasculature and the IRSP. Our results also showed that the numbers of abnormally expressed microvasculature and IRSP associated genes in diabetic AD donors who had been treated with anti-diabetic agents were reduced significantly. These findings suggest that anti-diabetic treatments may reduce or normalize compromised microvascular and IRSP functions in AD.
Topics: Aged, 80 and over; Alzheimer Disease; Cohort Studies; Endothelial Cells; Female; Gene Expression; Humans; Hypoglycemic Agents; Male; Microvessels; Parahippocampal Gyrus; RNA, Messenger; Receptor, Insulin
PubMed: 30383799
DOI: 10.1371/journal.pone.0206547 -
BMC Psychiatry Jul 2023Brain entropy reveals complexity and irregularity of brain, and it has been proven to reflect brain complexity alteration in disease states. Previous studies found that...
BACKGROUND
Brain entropy reveals complexity and irregularity of brain, and it has been proven to reflect brain complexity alteration in disease states. Previous studies found that bipolar disorder adolescents showed cognitive impairment. The relationship between complexity of brain neural activity and cognition of bipolar II disorder (BD-II) adolescents remains unclear.
METHODS
Nineteen BD-II patients (14.63 ±1.57 years old) and seventeen age-gender matched healthy controls (HCs) (14.18 ± 1.51 years old) were enlisted. Entropy values of all voxels of the brain in resting-state functional MRI data were calculated and differences of them between BD-II and HC groups were evaluated. After that, correlation analyses were performed between entropy values of brain regions showing significant entropy differences and clinical indices in BD-II adolescents.
RESULTS
Significant differences were found in scores of immediate visual reproduction subtest (VR-I, p = 0.003) and Stroop color-word test (SCWT-1, p = 0.015; SCWT-2, p = 0.004; SCWT-3, p = 0.003) between the two groups. Compared with HCs, BD-II adolescents showed significant increased brain entropy in right parahippocampal gyrus and right inferior occipital gyrus. Besides, significant negative correlations between brain entropy values of right parahippocampal gyrus, right inferior occipital gyrus and immediate visual reproduction subtest scores were observed in BD-II adolescents.
CONCLUSIONS
The findings of the present study suggested that the disrupted function of corticolimbic system is related with cognitive abnormality of BD-II adolescents. And from the perspective temporal dynamics of brain system, the current study, brain entropy may provide available evidences for understanding the underlying neural mechanism in BD-II adolescents.
Topics: Humans; Adolescent; Child; Bipolar Disorder; Entropy; Magnetic Resonance Imaging; Brain; Parahippocampal Gyrus; Occipital Lobe
PubMed: 37464363
DOI: 10.1186/s12888-023-05012-3