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Human Brain Mapping Jun 2013Posterior parahippocampal gyrus (PPHG) is strongly involved during scene recognition and spatial cognition. How PPHG electrophysiological activity could underlie these...
Posterior parahippocampal gyrus (PPHG) is strongly involved during scene recognition and spatial cognition. How PPHG electrophysiological activity could underlie these functions, and whether they share similar timing mechanisms is unknown. We addressed this question in two intracerebral experiments which revealed that PPHG neural activity dissociated an early stimulus-driven effect (>200 and <500 ms) and a late task-related effect (>600 and <800 ms). Strongest PPHG gamma band (50-150 Hz) activities were found early when subjects passively viewed scenes (scene selectivity effect) and lately when they had to estimate the position of an object relative to the environment (allocentric effect). Based on single trial analyses, we were able to predict when patients viewed scenes (compared to other visual categories) and when they performed allocentric judgments (compared to other spatial judgments). The anatomical location corresponding to the strongest effects was in the depth of the collateral sulcus. Our findings directly affect current theories of visual scene processing and spatial orientation by providing new timing constraints and by demonstrating the existence of separable information processing stages in the functionally defined parahippocampal place area.
Topics: Adult; Brain Mapping; Electroencephalography; Female; Humans; Parahippocampal Gyrus; Recognition, Psychology; Signal Processing, Computer-Assisted; Space Perception; Time; Visual Perception
PubMed: 22287281
DOI: 10.1002/hbm.21515 -
Hippocampus Jul 2021The hippocampus and parahippocampal region are essential for representing episodic memories involving various spatial locations and objects, and for using those memories... (Review)
Review
The hippocampus and parahippocampal region are essential for representing episodic memories involving various spatial locations and objects, and for using those memories for future adaptive behavior. The "dual-stream model" was initially formulated based on anatomical characteristics of the medial temporal lobe, dividing the parahippocampal region into two streams that separately process and relay spatial and nonspatial information to the hippocampus. Despite its significance, the dual-stream model in its original form cannot explain recent experimental results, and many researchers have recognized the need for a modification of the model. Here, we argue that dividing the parahippocampal region into spatial and nonspatial streams a priori may be too simplistic, particularly in light of ambiguous situations in which a sensory cue alone (e.g., visual scene) may not allow such a definitive categorization. Upon reviewing evidence, including our own, that reveals the importance of goal-directed behavioral responses in determining the relative involvement of the parahippocampal processing streams, we propose the Goal-directed Interaction of Stimulus and Task-demand (GIST) model. In the GIST model, input stimuli such as visual scenes and objects are first processed by both the postrhinal and perirhinal cortices-the postrhinal cortex more heavily involved with visual scenes and perirhinal cortex with objects-with relatively little dependence on behavioral task demand. However, once perceptual ambiguities are resolved and the scenes and objects are identified and recognized, the information is then processed through the medial or lateral entorhinal cortex, depending on whether it is used to fulfill navigational or non-navigational goals, respectively. As complex sensory stimuli are utilized for both navigational and non-navigational purposes in an intermixed fashion in naturalistic settings, the hippocampus may be required to then put together these experiences into a coherent map to allow flexible cognitive operations for adaptive behavior to occur.
Topics: Entorhinal Cortex; Goals; Hippocampus; Neural Pathways; Parahippocampal Gyrus; Perirhinal Cortex; Temporal Lobe
PubMed: 33394547
DOI: 10.1002/hipo.23295 -
Annals of the New York Academy of... Jun 2000The anatomical organization of the parahippocampal-hippocampal network indicates that it consists of different parallel circuits. Considering the topographical... (Review)
Review
The anatomical organization of the parahippocampal-hippocampal network indicates that it consists of different parallel circuits. Considering the topographical distribution of sensory cortical inputs, the hypothesis is that the major parallel circuits carry functionally different information. These functionally different parallel routes reach different portions of the hippocampal network along the longitudinal axis of all fields as well as along the perpendicularly oriented transverse axis of CA1 and the subiculum. In the remaining fields of the hippocampal formation, that is, the dentate gyrus and CA2/CA3, separation along the transverse axis is not present. By contrast, here the functionally different pathways converge onto the same neuronal population. The entorhinal cortex holds a pivotal position among the cortices that make up the parahippocampal region. By way of the networks of the superficial and deep layers, it mediates, respectively, the input and output streams of the hippocampal formation. Moreover, the intrinsic entorhinal network, particularly the interconnections between the deep and superficial layers, may mediate the comparison of hippocampal input and output signals. As such, the entorhinal cortex may form part of a novelty detection network. In addition, the organization of the entorhinal-hippocampal network may facilitate the holding of information. Finally, the terminal organization of the presubicular input to the medial entorhinal cortex indicates that the interactions between the deep and superficial entorhinal layers may be influenced by this input.
Topics: Animals; Hippocampus; Humans; Nerve Net; Neural Pathways; Parahippocampal Gyrus; Synaptic Transmission
PubMed: 10911864
DOI: 10.1111/j.1749-6632.2000.tb06716.x -
The American Journal of Psychiatry Jan 2000Anomalies of structure and asymmetry of the parahippocampal gyrus (origin of the perforant path input to the hippocampal formation in the medial temporal lobe) have been... (Comparative Study)
Comparative Study
OBJECTIVE
Anomalies of structure and asymmetry of the parahippocampal gyrus (origin of the perforant path input to the hippocampal formation in the medial temporal lobe) have been shown in some postmortem studies of schizophrenia, but previous studies have not included the fusiform gyrus (which may have a role in facial recognition and naming), adjacent to the parahippocampal gyrus on the ventral occipitotemporal surface.
METHOD
The volumes of gray matter in the left and right parahippocampal and fusiform gyri were assessed with a stereological point-counting technique in the temporal lobes from formalin-fixed brains of 27 comparison subjects and 31 patients with schizophrenia. Age was a covariate and gender was a factor in the analysis.
RESULTS
In relation to the comparison subjects, the schizophrenic patients (both sexes) had lower volumes of both the parahippocampal and fusiform gyri on the left side. For both structures a left-greater-than-right volume asymmetry was present in the comparison subjects, but this asymmetry was reversed in the parahippocampal and fusiform gyri of the schizophrenic patients. A sex difference was present with respect to age at onset-degree of anomaly of asymmetry for both gyri increased with age at onset in men but not in women.
CONCLUSIONS
The findings add substance to the view that the sex-related dimension of symmetry/asymmetry is integral to the disease process in schizophrenia and draw attention to the fusiform gyrus as a structure of particular interest in relation to disturbances of identification and naming in psychosis.
Topics: Adult; Age Factors; Age of Onset; Aged; Autopsy; Female; Functional Laterality; Humans; Male; Middle Aged; Neural Pathways; Parahippocampal Gyrus; Perforant Pathway; Schizophrenia; Schizophrenic Psychology; Sex Factors; Temporal Lobe
PubMed: 10618011
DOI: 10.1176/ajp.157.1.40 -
Trends in Cognitive Sciences Oct 2008Spatial navigation is a core cognitive ability in humans and animals. Neuroimaging studies have identified two functionally defined brain regions that activate during... (Review)
Review
Spatial navigation is a core cognitive ability in humans and animals. Neuroimaging studies have identified two functionally defined brain regions that activate during navigational tasks and also during passive viewing of navigationally relevant stimuli such as environmental scenes: the parahippocampal place area (PPA) and the retrosplenial complex (RSC). Recent findings indicate that the PPA and RSC have distinct and complementary roles in spatial navigation, with the PPA more concerned with representation of the local visual scene and RSC more concerned with situating the scene within the broader spatial environment. These findings are a first step towards understanding the separate components of the cortical network that mediates spatial navigation in humans.
Topics: Animals; Brain Mapping; Cerebral Cortex; Humans; Parahippocampal Gyrus; Recognition, Psychology; Space Perception; Spatial Behavior; Visual Pathways
PubMed: 18760955
DOI: 10.1016/j.tics.2008.07.004 -
Neurobiology of Aging Feb 2015Neuropathology suggests an important role for the locus coeruleus (LC) in Alzheimer's disease (AD) pathophysiology. Neuropathology and structural damage in the LC...
Neuropathology suggests an important role for the locus coeruleus (LC) in Alzheimer's disease (AD) pathophysiology. Neuropathology and structural damage in the LC appears to be one of the earliest changes. We hypothesize that reduced functional integration of the LC reflected by lower brain functional connectivity contributes to early memory dysfunction. To test this, we examined resting-state functional connectivity from the LC in 18 healthy older individuals and 18 mildly cognitively impaired patients with possible AD. Connectivity measures were correlated with memory scores. The left LC showed strong connectivity to the left parahippocampal gyrus that correlated with memory performance in healthy persons. This connectivity was reduced in aMCI patients. Lateralization of connectivity-memory correlations was altered in less impaired aMCI patients: greater right LC-left parahippocampal gyrus connectivity was associated with better memory performance, in particular for encoding. Our results provide new evidence that the LC, in interaction with the parahippocampal gyrus, may contribute to episodic memory formation. They suggest functional impairment and the possibility that associated compensatory changes contribute to preserved memory functions in early AD. Structural and functional LC-related measures may provide early AD markers.
Topics: Aged; Alzheimer Disease; Female; Humans; Locus Coeruleus; Magnetic Resonance Imaging; Male; Memory; Middle Aged; Neural Pathways; Neuropsychological Tests; Parahippocampal Gyrus; Rest; Severity of Illness Index; Temporal Lobe
PubMed: 25433457
DOI: 10.1016/j.neurobiolaging.2014.10.041 -
Schizophrenia Research Oct 2006Although several brain morphologic studies have suggested abnormalities in the temporal regions to be a common indicator of vulnerability for the schizophrenia spectrum,...
Although several brain morphologic studies have suggested abnormalities in the temporal regions to be a common indicator of vulnerability for the schizophrenia spectrum, less attention has been paid to temporal lobe structures other than the superior temporal gyrus or the medial temporal region. In this study, we investigated the volume of gray matter in the fusiform gyrus, the parahippocampal gyrus, the middle temporal gyrus, and the inferior temporal gyrus using magnetic resonance imaging in 39 schizotypal disorder patients, 65 schizophrenia patients, and 72 age and gender matched healthy control subjects. The anterior fusiform gyrus was significantly smaller in the schizophrenia patients than the control subjects but not in the schizotypal disorder patients, while the volume reduction of the posterior fusiform gyrus was common to both disorders. Volumes for the middle and inferior temporal gyri or the parahippocampal gyrus did not differ between groups. These findings suggest that abnormalities in the posterior region of the fusiform gyrus are, as have been suggested for the superior temporal gyrus or the amygdala/hippocampus, prominent among the temporal lobe structures as a common morphologic substrate for the schizophrenia spectrum, whereas more widespread alterations involving the anterior region might be associated with the development of full-blown schizophrenia.
Topics: Adult; Female; Functional Laterality; Humans; Magnetic Resonance Imaging; Male; Occipital Lobe; Parahippocampal Gyrus; Schizophrenia; Temporal Lobe
PubMed: 16750349
DOI: 10.1016/j.schres.2006.04.023 -
NeuroImage Jun 2004MR tractography techniques provide a method for noninvasively studying white matter pathways in vivo. In this study we have used diffusion tensor imaging (DTI) and the...
MR tractography techniques provide a method for noninvasively studying white matter pathways in vivo. In this study we have used diffusion tensor imaging (DTI) and the fast marching tractography (FMT) algorithm to plot the structural connectivity of the human parahippocampal gyrus (PHG) in 10 healthy subjects, using seed points selected in the anterior parahippocampal gyrus. Our results demonstrate connectivity between the parahippocampal gyrus and the anterior temporal lobe, orbitofrontal areas, posterior temporal lobe and extrastriate occipital lobe via the lingual and fusiform gyri. We also demonstrate for the first time noninvasively direct connectivity between the parahippocampal gyrus and the hippocampus itself. These results agree with previous histological tract-tracing studies in animals. The connections demonstrated between neocortical areas and the hippocampus via the parahippocampal gyrus may provide the structural basis for theoretical models of memory and higher visual processing.
Topics: Adult; Algorithms; Brain; Female; Functional Laterality; Humans; Male; Middle Aged; Models, Neurological; Models, Statistical; Neural Pathways; Parahippocampal Gyrus; Reference Values
PubMed: 15193602
DOI: 10.1016/j.neuroimage.2004.01.011 -
The American Journal of Psychiatry Apr 2010Activation in a network of language-related regions has been reported during auditory verbal hallucinations. It remains unclear, however, how this activation is...
OBJECTIVE
Activation in a network of language-related regions has been reported during auditory verbal hallucinations. It remains unclear, however, how this activation is triggered. Identifying brain regions that show significant signal changes preceding auditory hallucinations might reveal the origin of these hallucinations.
METHOD
Twenty-four patients with a psychotic disorder indicated the presence of auditory verbal hallucinations during 3-Tesla functional magnetic resonance imaging by squeezing a handheld balloon. A one-sample t test was performed to reveal groupwise activation during hallucinations. To enable analysis of brain activation 6 to 0 seconds preceding hallucinations, a tailored 'selective averaging' method, without any a priori assumptions concerning the hemodynamic response profile, was performed. To control for motor-related activation, 15 healthy comparison subjects squeezed a balloon at matched time intervals.
RESULTS
Groupwise analysis during auditory verbal hallucinations revealed brain activation in bilateral (right more than left) language-related regions and bilateral motor regions. Prominent deactivation preceding these hallucinations was observed in the left parahippocampal gyrus. In addition, significant deactivation preceding hallucinations was found in the left superior temporal, right inferior frontal, and left middle frontal gyri as well as in the right insula and left cerebellum. No significant signal changes were revealed prior to the matched balloon squeezing among the comparison subjects.
CONCLUSION
Auditory verbal hallucinations in patients with a psychotic disorder are consistently preceded by deactivation of the parahippocampal gyrus. The parahippocampus has been hypothesized to play a central role in memory recollection, sending information from the hippocampus to the association areas. Dysfunction of this region could trigger inadequate activation of right language areas during auditory hallucinations.
Topics: Adult; Antipsychotic Agents; Brain; Cerebrovascular Circulation; Chronic Disease; Female; Functional Laterality; Hallucinations; Humans; Magnetic Resonance Imaging; Male; Parahippocampal Gyrus; Schizophrenia; Severity of Illness Index; Time Factors; Verbal Behavior
PubMed: 20123912
DOI: 10.1176/appi.ajp.2009.09040456 -
Annals of the New York Academy of... Jun 2000The transentorhinal and entorhinal regions of the human brain extend over the ambient gyrus and anterior portions of the parahippocampal gyrus. They are important... (Review)
Review
The transentorhinal and entorhinal regions of the human brain extend over the ambient gyrus and anterior portions of the parahippocampal gyrus. They are important components of the limbic loop which receives its major afferents from the neocortical sensory association areas and generates powerful efferent projections both directly and via intermediary relay stations to the prefrontal cortex. The bilateral structural preservation of limbic loop components is a prerequisite for the maintenance of intact memory functions. In progressive neurodegenerative diseases, such as Alzheimer's disease, argyrophilic grain disease, Pick's disease, idiopathic Parkinson syndrome, and Huntington's disease, the transentorhinal and entorhinal regions are particularly susceptible to severe pathological changes. The transentorhinal region typically registers the initial alterations and becomes the most severely involved. From this transitional region of the mesocortex, the alterations usually invade with decreasing severity both the entorhinal region and temporal proneocortex. Each type of lesion that develops in the above-mentioned neurodegenerative disorders hampers or even interrupts data-transport from the sensory neocortex to the prefrontal neocortex, thereby contributing to the insidious development of progressive changes in personality, cognitive decline, and, ultimately, dementia.
Topics: Alzheimer Disease; Dementia; Humans; Neurodegenerative Diseases; Parahippocampal Gyrus
PubMed: 10911877
DOI: 10.1111/j.1749-6632.2000.tb06729.x