scholarly journals Dissecting the default mode network: direct structural evidence on the morphology and axonal connectivity of the fifth component of the cingulum bundle

2020 ◽  
pp. 1-12
Author(s):  
Georgios P. Skandalakis ◽  
Spyridon Komaitis ◽  
Aristotelis Kalyvas ◽  
Evgenia Lani ◽  
Chrysoula Kontrafouri ◽  
...  
Keyword(s):  
Temporal Lobe ◽  
Default Mode Network ◽  
Medial Temporal Lobe ◽  
Spatial Relationship ◽  
Distinct Group ◽  
Lateral Direction ◽  
Default Mode ◽  
Cingulum Bundle ◽  
Face Area ◽  
Close Spatial Relationship

OBJECTIVEAlthough a growing body of data support the functional connectivity between the precuneus and the medial temporal lobe during states of resting consciousness as well as during a diverse array of higher-order functions, direct structural evidence on this subcortical circuitry is scarce. Here, the authors investigate the very existence, anatomical consistency, morphology, and spatial relationships of the cingulum bundle V (CB-V), a fiber tract that has been reported to reside close to the inferior arm of the cingulum (CingI).METHODSFifteen normal, formalin-fixed cerebral hemispheres from adults were treated with Klingler’s method and subsequently investigated through the fiber microdissection technique in a medial to lateral direction.RESULTSA distinct group of fibers is invariably identified in the subcortical territory of the posteromedial cortex, connecting the precuneus and the medial temporal lobe. This tract follows the trajectory of the parietooccipital sulcus in a close spatial relationship with the CingI and the sledge runner fasciculus. It extends inferiorly to the parahippocampal place area and retrosplenial complex area, followed by a lateral curve to terminate toward the fusiform face area (Brodmann area [BA] 37) and lateral piriform area (BA35). Taking into account the aforementioned subcortical architecture, the CB-V allegedly participates as a major subcortical stream within the default mode network, possibly subserving the transfer of multimodal cues relevant to visuospatial, facial, and mnemonic information to the precuneal hub. Although robust clinical evidence on the functional role of this stream is lacking, the modern neurosurgeon should be aware of this tract when manipulating cerebral areas en route to lesions residing in or around the ventricular trigone.CONCLUSIONSThrough the fiber microdissection technique, the authors were able to provide original, direct structural evidence on the existence, morphology, axonal connectivity, and correlative anatomy of what proved to be a discrete white matter pathway, previously described as the CB-V, connecting the precuneus and medial temporal lobe.

scholarly journals Relationships between default-mode network connectivity, medial temporal lobe structure, and age-related memory deficits

2015 ◽  
Vol 36 (1) ◽  
pp. 265-272 ◽  
Author(s):  
Andrew M. Ward ◽  
Elizabeth C. Mormino ◽  
Willem Huijbers ◽  
Aaron P. Schultz ◽  
Trey Hedden ◽  
...  
Keyword(s):  
Temporal Lobe ◽  
Default Mode Network ◽  
Medial Temporal Lobe ◽  
Network Connectivity ◽  
Memory Deficits ◽  
Default Mode ◽  
Age Related

scholarly journals What can narratives tell us about the neural bases of human memory?

2020 ◽  
Author(s):  
Hongmi Lee ◽  
Buddhika Bellana ◽  
janice chen
Keyword(s):  
Temporal Lobe ◽  
Neural Activity ◽  
Default Mode Network ◽  
Medial Temporal Lobe ◽  
Activity Patterns ◽  
Human Memory ◽  
Memory System ◽  
Situation Models ◽  
Neural Synchrony ◽  
Default Mode

Narratives are increasingly used to study naturalistic human memory and its brain mechanisms. Narratives—audiovisual movies, spoken stories, and written stories—consist of multiple inter-related and temporally unfolding events which are rich in semantic and emotional content. These characteristics drive intersubject neural synchrony in the default mode network, where abstract situation models are represented and reinstated. Medial temporal lobe structures interact with the cortical sub-regions of the default mode network to support the encoding and recall of narrative events. Narrative memories are frequently communicated across individuals, resulting in the transmission of experiences and neural activity patterns between people. Recent advances in neuroimaging and naturalistic stimulus analysis provide valuable insights into narrative memory and the human memory system in general.

scholarly journals Increased posterior default mode network activity and structural connectivity in young adult APOE-ε4 carriers: a multi-modal imaging investigation

2018 ◽  
Author(s):  
Carl J. Hodgetts ◽  
Jonathan P. Shine ◽  
Huw Williams ◽  
Mark Postans ◽  
Rebecca Sims ◽  
...  
Keyword(s):  
Young Adult ◽  
Default Mode Network ◽  
Medial Temporal Lobe ◽  
Structural Connectivity ◽  
Mean Diffusivity ◽  
Network Activity ◽  
Default Mode ◽  
Cingulum Bundle ◽  
Brain Changes ◽  
Increased Activity

AbstractYoung adult APOE-ε4 carriers show increased activity in posterior regions of the default mode network (pDMN), but how this is related to structural connectivity is unknown. Thirty young adults (half APOE-ε4 carriers, the other half APOE-ε3ε3/ε2ε3; mean age 20 years) were scanned using both diffusion and functional magnetic resonance imaging. Diffusion tractography was used to quantify the microstructure (mean diffusivity, MD; fractional anisotropy, FA) of the parahippocampal cingulum bundle (PHCB), which links pDMN and the medial temporal lobe. APOE-ε4 carriers had lower MD and higher FA relative to non-carriers in PHCB. Further, PHCB microstructure was selectively associated with pDMN activity during a scene discrimination task known to be sensitive to Alzheimer’s disease (AD). These findings are consistent with a lifespan view of AD risk, where early-life structural and functional brain changes in specific, vulnerable networks leads to increased neural activity that may ultimately trigger amyloid-ß deposition.

scholarly journals The retrosplenial cortex: A memory gateway between the cortical default mode network and the medial temporal lobe

2018 ◽  
Vol 39 (5) ◽  
pp. 2020-2034 ◽  
Author(s):  
Neda Kaboodvand ◽  
Lars Bäckman ◽  
Lars Nyberg ◽  
Alireza Salami
Keyword(s):  
Temporal Lobe ◽  
Default Mode Network ◽  
Medial Temporal Lobe ◽  
Retrosplenial Cortex ◽  
Default Mode

scholarly journals Differential medial temporal lobe and default-mode network functional connectivity and morphometric changes in Alzheimer’s Disease

2017 ◽  
Author(s):  
Kamil A. Grajski ◽  
Steven L. Bressler ◽  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cognitive Impairment ◽  
Mild Cognitive Impairment ◽  
Functional Connectivity ◽  
Temporal Lobe ◽  
Default Mode Network ◽  
Medial Temporal Lobe ◽  
Resting State Functional Connectivity ◽  
Default Mode

AbstractWe report group level differential detection of medial temporal lobe resting-state functional connectivity disruption and morphometric changes in the transition from cognitively normal to early mild cognitive impairment in an age-, education- and gender-matched 105 subjects Alzheimer’s Disease Neuroimaging Initiative dataset. In mild Alzheimer’s Disease, but not early mild cognitive impairment, characteristic brain atrophy was detected in FreeSurfer estimates of cortical thickness and subcortical and hippocampal subfield volumes. By contrast, functional connectivity analysis detected earlier significant changes. In early mild cognitive impairment these changes involved medial temporal lobe regions of transentorhinal, perirhinal and entorhinal cortices (associated with the earliest stages of neurofibrillary changes in Alzheimer’s Disease), hippocampus, parahippocampal gyrus and temporal pole, and cortical regions comprising or co-activated with the default-mode network, including rostral and medial prefrontal cortex, anterior cingulate cortex, precuneus and inferior temporal cortex. Key findings include: a) focal and bilaterally symmetric spatial organization of affected medial temporal lobe regions; b) mutual hyperconnectivity bilaterally involving ventral medial temporal lobe structures (temporal pole, uncus); and c) dorsal medial temporal lobe hypoconnectivity with anterior and posterior midline default-mode network nodes. These findings position medial temporal lobe resting state functional connectivity as a candidate biomarker of an Alzheimer’s Disease pathophysiological cascade, potentially in advance of clinical biomarkers, and coincident with biomarkers of the earliest stages of Alzheimer’s neuropathology. Our results indicate that medial temporal lobe resting-state functional connectivity should be further investigated as a potential biomarker in the diagnosis of Alzheimer’s Disease.HighlightsFunctional connectivity change seen before structural change in Alzheimer’s DiseaseMedial temporal lobes mutually hyper-connect in mild cognitive impairmentMedial temporal lobe and default mode network decouple in mild cognitive impairmentLoci of functional change in hippocampi are focal with bilaterally symmetric featuresNonmonotonic functional connectivity changes in Alzheimer’s Disease progression

Sign in / Sign up

Export Citation Format

Share Document