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Annals of Neurology Feb 2015Patients with Parkinson disease (PD) and mild cognitive impairment (MCI) are vulnerable to dementia and frequently experience memory deficits. This could be the result...
OBJECTIVE
Patients with Parkinson disease (PD) and mild cognitive impairment (MCI) are vulnerable to dementia and frequently experience memory deficits. This could be the result of dopamine dysfunction in corticostriatal networks (salience, central executive networks, and striatum) and/or the medial temporal lobe. Our aim was to investigate whether dopamine dysfunction in these regions contributes to memory impairment in PD.
METHODS
We used positron emission tomography imaging to compare D2 receptor availability in the cortex and striatal (limbic and associative) dopamine neuron integrity in 4 groups: memory-impaired PD (amnestic MCI; n = 9), PD with nonamnestic MCI (n = 10), PD without MCI (n = 11), and healthy controls (n = 14). Subjects were administered a full neuropsychological test battery for cognitive performance.
RESULTS
Memory-impaired patients demonstrated more significant reductions in D2 receptor binding in the salience network (insular cortex and anterior cingulate cortex [ACC] and the right parahippocampal gyrus [PHG]) compared to healthy controls and patients with no MCI. They also presented reductions in the right insula and right ACC compared to nonamnestic MCI patients. D2 levels were correlated with memory performance in the right PHG and left insula of amnestic patients and with executive performance in the bilateral insula and left ACC of all MCI patients. Associative striatal dopamine denervation was significant in all PD patients.
INTERPRETATION
Dopaminergic differences in the salience network and the medial temporal lobe contribute to memory impairment in PD. Furthermore, these findings indicate the vulnerability of the salience network in PD and its potential role in memory and executive dysfunction.
Topics: Aged; Dopamine; Dopaminergic Neurons; Female; Humans; Male; Memory Disorders; Middle Aged; Nerve Net; Parahippocampal Gyrus; Parkinson Disease; Positron-Emission Tomography; Protein Binding; Receptors, Dopamine D2
PubMed: 25448687
DOI: 10.1002/ana.24323 -
Psychiatry Research Dec 2009Emotional liability and mood dysregulation characterize bipolar disorder (BD), yet no study has examined effective connectivity between parahippocampal gyrus and...
Emotional liability and mood dysregulation characterize bipolar disorder (BD), yet no study has examined effective connectivity between parahippocampal gyrus and prefrontal cortical regions in ventromedial and dorsal/lateral neural systems subserving mood regulation in BD. Participants comprised 46 individuals (age range: 18-56 years): 21 with a DSM-IV diagnosis of BD, type I currently remitted; and 25 age- and gender-matched healthy controls (HC). Participants performed an event-related functional magnetic resonance imaging paradigm, viewing mild and intense happy and neutral faces. We employed dynamic causal modeling (DCM) to identify significant alterations in effective connectivity between BD and HC. Bayes model selection was used to determine the best model. The right parahippocampal gyrus (PHG) and right subgenual cingulate gyrus (sgCG) were included as representative regions of the ventromedial neural system. The right dorsolateral prefrontal cortex (DLPFC) region was included as representative of the dorsal/lateral neural system. Right PHG-sgCG effective connectivity was significantly greater in BD than HC, reflecting more rapid, forward PHG-sgCG signaling in BD than HC. There was no between-group difference in sgCG-DLPFC effective connectivity. In BD, abnormally increased right PHG-sgCG effective connectivity and reduced right PHG activity to emotional stimuli suggest a dysfunctional ventromedial neural system implicated in early stimulus appraisal, encoding and automatic regulation of emotion that may represent a pathophysiological functional neural mechanism for mood dysregulation in BD.
Topics: Adult; Bayes Theorem; Bipolar Disorder; Brain Mapping; Case-Control Studies; Emotions; Female; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; Models, Statistical; Neural Pathways; Neuropsychological Tests; Nonlinear Dynamics; Oxygen; Parahippocampal Gyrus; Prefrontal Cortex; Young Adult
PubMed: 19910166
DOI: 10.1016/j.pscychresns.2009.04.015 -
Annual Review of Neuroscience 2007The ability to recognize a previously experienced stimulus is supported by two processes: recollection of the stimulus in the context of other information associated... (Review)
Review
The ability to recognize a previously experienced stimulus is supported by two processes: recollection of the stimulus in the context of other information associated with the experience, and a sense of familiarity with the features of the stimulus. Although familiarity and recollection are functionally distinct, there is considerable debate about how these kinds of memory are supported by regions in the medial temporal lobes (MTL). Here, we review evidence for the distinction between recollection and familiarity and then consider the evidence regarding the neural mechanisms of these processes. Evidence from neuropsychological, neuroimaging, and neurophysiological studies of humans, monkeys, and rats indicates that different subregions of the MTL make distinct contributions to recollection and familiarity. The data suggest that the hippocampus is critical for recollection but not familiarity. The parahippocampal cortex also contributes to recollection, possibly via the representation and retrieval of contextual (especially spatial) information, whereas perirhinal cortex contributes to and is necessary for familiarity-based recognition. The findings are consistent with an anatomically guided hypothesis about the functional organization of the MTL and suggest mechanisms by which the anatomical components of the MTL interact to support the phenomenology of recollection and familiarity.
Topics: Animals; Evoked Potentials; Hippocampus; Humans; Memory; Models, Animal; Models, Neurological; Neural Pathways; Parahippocampal Gyrus; Recognition, Psychology; Temporal Lobe
PubMed: 17417939
DOI: 10.1146/annurev.neuro.30.051606.094328 -
Hippocampus Apr 2020Grid cells provide a compelling example of a link between cellular activity and an abstract and difficult to define concept like space. Accordingly, a representational... (Review)
Review
Grid cells provide a compelling example of a link between cellular activity and an abstract and difficult to define concept like space. Accordingly, a representational perspective on grid coding argues that neural grid coding underlies a fundamentally spatial metric. Recently, some theoretical proposals have suggested extending such a framework to nonspatial cognition as well, such as category learning. Here, we provide a critique of the frequently employed assumption of an isomorphism between patterns of neural activity (e.g., grid cells), mental representation, and behavior (e.g., navigation). Specifically, we question the strict isomorphism between these three levels and suggest that human spatial navigation is perhaps best characterized by a wide variety of both metric and nonmetric strategies. We offer an alternative perspective on how grid coding might relate to human spatial navigation, arguing that grid coding is part of a much larger conglomeration of neural activity patterns that dynamically tune to accomplish specific behavioral outputs.
Topics: Animals; Entorhinal Cortex; Grid Cells; Humans; Models, Neurological; Spatial Navigation
PubMed: 31742364
DOI: 10.1002/hipo.23175 -
Neuron Mar 2021Human brain pathways supporting language and declarative memory are thought to have differentiated substantially during evolution. However, cross-species comparisons are...
Human brain pathways supporting language and declarative memory are thought to have differentiated substantially during evolution. However, cross-species comparisons are missing on site-specific effective connectivity between regions important for cognition. We harnessed functional imaging to visualize the effects of direct electrical brain stimulation in macaque monkeys and human neurosurgery patients. We discovered comparable effective connectivity between caudal auditory cortex and both ventro-lateral prefrontal cortex (VLPFC, including area 44) and parahippocampal cortex in both species. Human-specific differences were clearest in the form of stronger hemispheric lateralization effects. In humans, electrical tractography revealed remarkably rapid evoked potentials in VLPFC following auditory cortex stimulation and speech sounds drove VLPFC, consistent with prior evidence in monkeys of direct auditory cortex projections to homologous vocalization-responsive regions. The results identify a common effective connectivity signature in human and nonhuman primates, which from auditory cortex appears equally direct to VLPFC and indirect to the hippocampus. VIDEO ABSTRACT.
Topics: Adolescent; Adult; Animals; Auditory Cortex; Brain Mapping; Electric Stimulation; Female; Frontal Lobe; Humans; Macaca mulatta; Magnetic Resonance Imaging; Male; Middle Aged; Neural Pathways; Parahippocampal Gyrus; Prefrontal Cortex; Species Specificity; Temporal Lobe; Young Adult
PubMed: 33482086
DOI: 10.1016/j.neuron.2020.12.026 -
Human Brain Mapping Jan 2021Insomnia disorder is the most common sleep disorder and has drawn increasing attention. Many studies have shown that hyperarousal plays a key role in the pathophysiology...
Insomnia disorder is the most common sleep disorder and has drawn increasing attention. Many studies have shown that hyperarousal plays a key role in the pathophysiology of insomnia disorder. However, the specific brain mechanisms underlying insomnia disorder remain unclear. To elucidate the neuropathophysiology of insomnia disorder, we investigated the brain functional networks of patients with insomnia disorder and healthy controls across the sleep-wake cycle. EEG-fMRI data from 33 patients with insomnia disorder and 31 well-matched healthy controls during wakefulness and nonrapid eye movement sleep, including N1, N2 and N3 stages, were analyzed. A medial and anterior thalamic region was selected as the seed considering its role in sleep-wake regulation. The functional connectivity between the thalamic seed and voxels across the brain was calculated. ANOVA with factors "group" and "stage" was performed on thalamus-based functional connectivity. Correlations between the misperception index and altered functional connectivity were explored. A group-by-stage interaction was observed at widespread cortical regions. Regarding the main effect of group, patients with insomnia disorder demonstrated decreased thalamic connectivity with the left amygdala, parahippocampal gyrus, putamen, pallidum and hippocampus across wakefulness and all three nonrapid eye movement sleep stages. The thalamic connectivity in the subcortical cluster and the right temporal cluster in N1 was significantly correlated with the misperception index. This study demonstrated the brain functional basis in insomnia disorder and illustrated its relationship with sleep misperception, shedding new light on the brain mechanisms of insomnia disorder and indicating potential therapeutic targets for its treatment.
Topics: Adult; Amygdala; Connectome; Corpus Striatum; Electroencephalography; Female; Hippocampus; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Nerve Net; Parahippocampal Gyrus; Polysomnography; Sleep Initiation and Maintenance Disorders; Sleep Stages; Thalamus; Wakefulness
PubMed: 33048406
DOI: 10.1002/hbm.25221 -
Neurology Mar 2010To report 4 cases of hyperfamiliarity for faces (HFF) and review 5 previously reported cases.
OBJECTIVE
To report 4 cases of hyperfamiliarity for faces (HFF) and review 5 previously reported cases.
METHODS
We identified cases of HFF from PubMed search and references in prior reports.
RESULTS
Three of our 4 cases had pathologic findings that were most extensive in the left temporal lobe. HFF occurred after a tonic-clonic seizure (cases 1 and 3), during simple partial seizures (case 2), and in the setting of an increase in simple partial seizure frequency but not during seizures (case 4). All 9 cases were adults with 1 or more seizures; symptoms first occurred after seizures in 5 cases and during seizures in 1 case. Ictal symptoms lasted from seconds to minutes and from 2 days to more than 7 years in the other 6 cases. The duration of HFF was not associated with the presence or extent of a structural lesion. While in several cases HFF appears to result from a postictal Todd paralysis, the mechanism underlying persistent cases is uncertain.
CONCLUSIONS
This modality (visual)-specific and stimulus (face)-specific syndrome is associated with diverse structural, functional imaging, and neurophysiologic findings. Lesions are more often left-sided and involve the temporal lobe. Epilepsy and seizures were present in all 9 cases, suggesting a pathophysiologic relationship, which likely varies among cases. Although only reported in 9 patients, HFF is probably much more common than it is diagnosed.
Topics: Arousal; Attention Deficit Disorder with Hyperactivity; Cognition Disorders; Epilepsy, Tonic-Clonic; Face; Humans; Magnetic Resonance Imaging; Male; Memory Disorders; Middle Aged; Neuropsychological Tests; Parahippocampal Gyrus; Pattern Recognition, Physiological; Recognition, Psychology; Syndrome; Temporal Lobe
PubMed: 20308681
DOI: 10.1212/WNL.0b013e3181d5dc22 -
Behavioural Brain Research Oct 2013Available evidence suggests there is functional differentiation among hippocampal and parahippocampal subregions and along the dorsoventral (septotemporal) axis of the...
Available evidence suggests there is functional differentiation among hippocampal and parahippocampal subregions and along the dorsoventral (septotemporal) axis of the hippocampus. The aim of this study was to characterize and compare the efferent and afferent connections of perirhinal areas 35 and 36, postrhinal cortex, and the lateral and medial entorhinal areas (LEA and MEA) with dorsal and ventral components of the hippocampal formation (dentate gyrus, hippocampus cornu ammonis fields, and subiculum) as well as the presubiculum, and the parasubiculum. The entorhinal connections were also characterized with respect to the LEA and MEA dentate gyrus-projecting bands. In general, the entorhinal connections with the hippocampal formation are much stronger than the perirhinal and postrhinal connections. The entorhinal cortex projects strongly to all components of the hippocampal formation, whereas the perirhinal and postrhinal cortices project weakly and only to CA1 and the subiculum. In addition, the postrhinal cortex preferentially targets the dorsal CA1 and subiculum, whereas the perirhinal cortex targets ventral subiculum. Similarly, the perirhinal cortex receives more input from ventral hippocampal formation structures and the postrhinal cortex receives more input from dorsal hippocampal structures. The LEA and the MEA medial band are more strongly interconnected with ventral hippocampal structures, whereas the MEA lateral band is more interconnected with dorsal hippocampal structures. With regard to the presubiculum and parasubiculum, the postrhinal cortex and the MEA lateral band receive stronger input from the dorsal presubiculum and caudal parasubiculum. In contrast, the LEA and MEA medial bands receive stronger input from the ventral presubiculum and rostral parasubiculum.
Topics: Afferent Pathways; Animals; Efferent Pathways; Entorhinal Cortex; Hippocampus; Male; Rats; Rats, Sprague-Dawley
PubMed: 23872326
DOI: 10.1016/j.bbr.2013.07.005 -
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 -
Psychopharmacology May 2021Prolonged use of cannabis, the most widely used illicit drug worldwide, has been consistently associated with impairment in memory and verbal learning. Although the...
RATIONALE
Prolonged use of cannabis, the most widely used illicit drug worldwide, has been consistently associated with impairment in memory and verbal learning. Although the neurophysiological underpinnings of these impairments have been investigated previously using functional magnetic resonance imaging (fMRI), while performing memory tasks, the results of these studies have been inconsistent and no clear picture has emerged yet. Furthermore, no previous studies have investigated trial-by-trial learning.
OBJECTIVES
We aimed to investigate the neural underpinnings of impaired verbal learning in cannabis users as estimated over repeated learning trials.
METHODS
We studied 21 adolescent-onset regular cannabis users and 21 non-users using fMRI performed at least 12 h after last cannabis use, while they performed a paired associate verbal learning task that allowed us to examine trial-by-trial learning. Brain activation during repeated verbal encoding and recall conditions of the task was indexed using the blood oxygen level-dependent haemodynamic response fMRI signal.
RESULTS
There was a significant improvement in recall score over repeated trials indicating learning occurring across the two groups of participants. However, learning was significantly slower in cannabis users compared to non-users (p = 0.032, partial eta-squared = 0.108). While learning verbal stimuli over repeated encoding blocks, non-users displayed progressive increase in recruitment of the midbrain, parahippocampal gyrus and thalamus (p = 0.00939, partial eta-squared = 0.180). In contrast, cannabis users displayed a greater but disrupted activation pattern in these regions, which showed a stronger correlation with new word-pairs learnt over the same blocks in cannabis users than in non-users.
CONCLUSIONS
These results suggest that disrupted medial temporal and midbrain function underlie slower learning in adolescent-onset cannabis users.
Topics: Adolescent; Adult; Female; Humans; Learning; Magnetic Resonance Imaging; Male; Marijuana Smoking; Memory; Mental Recall; Mesencephalon; Parahippocampal Gyrus; Verbal Learning; Young Adult
PubMed: 31814047
DOI: 10.1007/s00213-019-05407-9