Temporal Lobe Anatomy Research Articles

Long-term abacus training gains in children are predicted by medial temporal lobe anatomy and circuitry.

Abacus-based mental calculation (AMC) is a widely used educational tool for enhancing math learning, offering an accessible and cost-effective method for classroom implementation. Despite its universal appeal, the neurocognitive mechanisms that drive the efficacy of AMC training remain poorly understood. Notably, although abacus training relies heavily on the rapid recall of number positions and sequences, the role of memory systems in driving long-term AMC learning remains unknown. Here, we sought to address this gap by investigating the role of the medial temporal lobe (MTL) memory system in predicting long-term AMC training gains in second-grade children, who were longitudinally assessed up to fifth grade. Leveraging multimodal neuroimaging data, we tested the hypothesis that MTL systems, known for their involvement in associative memory, are instrumental in facilitating AMC-induced improvements in math skills. We found that gray matter volume in bilateral MTL, along with functional connectivity between the MTL and frontal and ventral temporal-occipital cortices, significantly predicted learning gains. Intriguingly, greater gray matter volume but weaker connectivity of the posterior parietal cortex predicted better learning outcomes, offering a more nuanced view of brain systems at play in AMC training. Our findings not only underscore the critical role of the MTL memory system in AMC training but also illuminate the neurobiological factors contributing to individual differences in cognitive skill acquisition. RESEARCH HIGHLIGHTS: We investigated the role of medial temporal lobe (MTL) memory system in driving children's math learning following abacus-based mental calculation (AMC) training. AMC training improved math skills in elementary school children across their second and fifth grade. MTL structural integrity and functional connectivity with prefrontal and ventral temporal-occipital cortices predicted long-term AMC training-related gains.

Intrinsic neural timescales in the temporal lobe support an auditory processing hierarchy.

During rest, intrinsic neural dynamics manifest at multiple timescales, which progressively increase along visual and somatosensory hierarchies. Theoretically, intrinsic timescales are thought to facilitate processing of external stimuli at multiple stages. However, direct links between timescales at rest and sensory processing, as well as translation to the auditory system are lacking. Here, we measured intracranial electroencephalography in 11 human patients with epilepsy (4 women), while listening to pure tones. We show that in the auditory network, intrinsic neural timescales progressively increase, while the spectral exponent flattens, from temporal to entorhinal cortex, hippocampus, and amygdala. Within the neocortex, intrinsic timescales exhibit spatial gradients that follow the temporal lobe anatomy. Crucially, intrinsic timescales at baseline can explain the latency of auditory responses: as intrinsic timescales increase, so do the single-electrode response onset and peak latencies. Our results suggest that the human auditory network exhibits a repertoire of intrinsic neural dynamics, which manifest in cortical gradients with millimeter resolution and may provide a variety of temporal windows to support auditory processing.SIGNIFICANCE STATEMENT:Endogenous neural dynamics are often characterized by their intrinsic timescales. These are thought to facilitate processing of external stimuli. However, a direct link between intrinsic timing at rest and sensory processing is missing. Here, with intracranial electroencephalography (iEEG), we show that intrinsic timescales progressively increase from temporal to entorhinal cortex, hippocampus, and amygdala. Intrinsic timescales at baseline can explain the variability in the timing of iEEG responses to sounds: cortical electrodes with fast timescales also show fast and short-lasting responses to auditory stimuli, which progressively increase in the hippocampus and amygdala. Our results suggest that a hierarchy of neural dynamics in the temporal lobe manifests across cortical and limbic structures and can explain the temporal richness of auditory responses.

Anatomical Subpial Resection of Tumors in the Amygdala and Hippocampus

Surgical techniques to achieve complete resection of mesial-basal temporal tumors should be pursued by neurosurgical oncologists. We describe the anatomical subpial amygdalohippocampectomy (SpAH) technique for tumor resection. The key anatomical landmarks and critical steps of the SpAH technique were outlined and emphasized with medical illustrations and intraoperative photographs. The senior author's 90-day surgical outcomes with this approach were reviewed. Twenty-five patients (men, 17 [68%]; women, 8 [32%]; median [range] age, 59 [23-80] years) with temporal tumors involving the amygdalohippocampal region were included. SpAH was performed selectively in 8 [32%] patients, whereas 17 [68%] patients underwent SpAH in conjunction with an anterior temporal lobectomy due to tumor involvement of the anterolateral temporal cortex. The subpial resection of the amygdala protected the critical structures of the suprasellar cistern and sylvian fissure. Identifying the choroidal fissure as the superior-most aspect of hippocampal resection protected the optic tract and the thalamus. Subpial resection of the parahippocampal gyrus inferiorly protected the brainstem and critical structures of the ambient cistern. Tumors in the amygdalohippocampal region were anatomically and completely resected in all 25 patients. Of the 15 patients who presented with seizures, 13 (87%) were seizure-free at the 90-day postsurgical follow-up. Permanent neurologic deficits occurred in 3 patients (12%). The SpAH technique permits complete resection of mesial-basal temporal tumors with an acceptable morbidity profile. An in-depth understanding of temporal lobe anatomy combined with a refined microsurgical technique allows for reproducible resection of tumor in the amygdalohippocampal region while protecting critical neurovascular structures.

The cortical origin and initial spread of medial temporal tauopathy in Alzheimer's disease assessed with positron emission tomography.

Advances in molecular positron emission tomography (PET) have enabled anatomic tracking of brain pathology in longitudinal studies of normal aging and dementia, including assessment of the central model of Alzheimer's disease (AD) pathogenesis, according to which TAU pathology begins focally but expands catastrophically under the influence of amyloid-β (Aβ) pathology to mediate neurodegeneration and cognitive decline. Initial TAU deposition occurs many years before Aβ in a specific area of the medial temporal lobe. Building on recent work that enabled focus of molecular PET measurements on specific TAU-vulnerable convolutional temporal lobe anatomy, we applied an automated anatomic sampling method to quantify TAU PET signal in 443 adult participants from several observational studies of aging and AD, spanning a wide range of ages, Aβ burdens, and degrees of clinical impairment. We detected initial cortical emergence of tauopathy near the rhinal sulcus in clinically normal people and, in a subset with longitudinal 2-year follow-up data (n = 104), tracked Aβ-associated spread of TAU from this site first to nearby neocortex of the temporal lobe and then to extratemporal regions. Greater rate of TAU spread was associated with baseline measures of both global Aβ burden and medial temporal lobe TAU. These findings are consistent with clinicopathological correlation studies of Alzheimer's tauopathy and enable precise tracking of AD-related TAU progression for natural history studies and prevention therapeutic trials.

Microanatomia cirúrgica relevante na amigdalohipocampectomia seletiva

Introdução: O lobo temporal é o mais heterogêneo do cérebro humano, tendo em sua composição alocórtex e estruturas do sistema límbico. Crises convulsivas parciais complexas com origem no lobo temporal correspondem a 70% dos pacientes refratários ao tratamento clínico que são encaminhados a centros de cirurgia de eplipsia. Os procedimentos cirúrgicos utilizados no tratamento da epilepsia do lobo temporal tiveram forte impacto na qualidade de vida dos pacientes. O conhecimento anatômico profundo é fundamental para ressecções cirúrgicas seguras das estruturs do lobo temporal. Ao serem estudados diferentes ângulos de visão, não somente e anatomia convencional, mas também a anatomia microcirúrgica e técnicas não convencionais de dissecção, como a dissecção de fibras brancas cerebrais, a segurança do procedimento é aumentada à medida que aumenta a chamada "visão de raios X" do cirurgião. O objetivo deste estudo é apresentar a anatomia relevante na amigdalohipocampectomia seletiva com técnicas de dissecção convencionais e não-convencionais, bem como documentar com fotografias convencionais e estereoscopia. Métodos: Vinte cérebros fixados em formalina e seis cadáveres fixados em Carolina's perfect solution (Carolina Biological Supply Company, Burlington, NC) foram dissecados com microscópio cirúrgico com aumentos de 3 a 40 vezes. Cada crânio foi colocado no fiador tipo Mayfield e a cabeça estendida e rodada para simular a posição cirúrgica. Craniotomia pterional e amigdalohipocampectomia seletiva transilviana foram realizados a seguir. As dissecções anatômicas foram documentadas com estereoscopia. Resultados: A amigdalohipocampectomia seletiva transilviana é documentada por etapas e a dissecção de fibras brancas utilizada para ilustrar esta antomia. A discussão é centralizada na comparação entre este procedimento com as vias transcorticais e lobectomia anterior. Conclusão: A complexa anatomia do lobo temporal relacionada à amigdalohipocampectomia seletiva e suas variantes podem ser totalmente entendidas mediante diferentes perspectivas anatômicas.

Predicting patterns of failure in temporal lobe GBMs: possible implications on radiotherapy treatment portals

BackgroundCharacterise patterns of failure of Temporal Lobe (TL) Glioblastoma (GBM) following treatment with relation to normal temporal lobe anatomy and neural pathways.Methods335 GBM patients received radiotherapy between 03/2007 and 07/2014, 100 were located in TL. Site of initial tumour and subsequent relapse were subdivided into 5 local TL sites (anterior, lateral, medial, posterior and superior); 5 adjacent regional sites (occipital lobe, inferior frontal lobe, caudate/thalamus/internal/external capsules, fornix/ventricular trigone), and 5 distant failure sites (ventricles, contralateral hemisphere, brainstem, leptomeninges and spine). Extension along major neuroanatomical pathways at initial presentation and at first documented Magnetic Resonance Imaging (MRI) failure were categorised into anterior, superior, medial and posterior pathways.ResultsOf the 100 patients, 86 had radiological progress with a median survival of 17.3 months.At initial diagnosis, 74% of tumours were linked to one TL site and 94% were confined to the TL. 19% had neural pathway disease at initial pre-treatment MRI. At first recurrence locoregional site failure was 74%. 26% failed within distant sites and 53% patients were noted to have neural pathway involvement.Initial tumour location predicted for local site recurrence (p < 0.0001), regional site recurrence (p = 0.004) and neural pathway recurrence pattern (p = 0.005), but not for distant sites (p = 0.081).ConclusionMost GBMs fail at local or adjacent regional sites. Many of the recurrences occurred in a predictable pattern within a local or regional site, unique to initial TL site with more than half involving neural pathways. Knowledge of tumour infiltration and failure may improve target definition and radiotherapy.

A protocol for manual segmentation of medial temporal lobe subregions in 7Tesla MRI.

Recent advances in MRI and increasing knowledge on the characterization and anatomical variability of medial temporal lobe (MTL) anatomy have paved the way for more specific subdivisions of the MTL in humans. In addition, recent studies suggest that early changes in many neurodegenerative and neuropsychiatric diseases are better detected in smaller subregions of the MTL rather than with whole structure analyses. Here, we developed a new protocol using 7 Tesla (T) MRI incorporating novel anatomical findings for the manual segmentation of entorhinal cortex (ErC), perirhinal cortex (PrC; divided into area 35 and 36), parahippocampal cortex (PhC), and hippocampus; which includes the subfields subiculum (Sub), CA1, CA2, as well as CA3 and dentate gyrus (DG) which are separated by the endfolial pathway covering most of the long axis of the hippocampus. We provide detailed instructions alongside slice-by-slice segmentations to ease learning for the untrained but also more experienced raters. Twenty-two subjects were scanned (19–32 yrs, mean age = 26 years, 12 females) with a turbo spin echo (TSE) T2-weighted MRI sequence with high-resolution oblique coronal slices oriented orthogonal to the long axis of the hippocampus (in-plane resolution 0.44 × 0.44 mm2) and 1.0 mm slice thickness. The scans were manually delineated by two experienced raters, to assess intra- and inter-rater reliability. The Dice Similarity Index (DSI) was above 0.78 for all regions and the Intraclass Correlation Coefficients (ICC) were between 0.76 to 0.99 both for intra- and inter-rater reliability. In conclusion, this study presents a fine-grained and comprehensive segmentation protocol for MTL structures at 7 T MRI that closely follows recent knowledge from anatomical studies. More specific subdivisions (e.g. area 35 and 36 in PrC, and the separation of DG and CA3) may pave the way for more precise delineations thereby enabling the detection of early volumetric changes in dementia and neuropsychiatric diseases.

B-18Correlation of Mesial Temporal Lobe Anatomy with Neuropsychological Performance in Epilepsy Patients Undergoing Evaluation for Laser Thermal Ablation

B-18Correlation of Mesial Temporal Lobe Anatomy with Neuropsychological Performance in Epilepsy Patients Undergoing Evaluation for Laser Thermal Ablation

A Largest Case Series of Stapled Transanal Rectal Resection (STARR) in the Management of Incomplete Rectal Prolapse

Recent advances in MRI and increasing knowledge on the characterization and anatomical variability of medial temporal lobe (MTL) anatomy have paved the way for more specific subdivisions of the MTL in humans. In addition, recent studies suggest that early changes in many neurodegenerative and neuropsychiatric diseases are better detected in smaller subregions of the MTL rather than with whole structure analyses. Here, we developed a new protocol using 7 Tesla (T) MRI incorporating novel anatomical findings for the manual segmentation of entorhinal cortex (ErC), perirhinal cortex (PrC; divided into area 35 and 36), parahippocampal cortex (PhC), and hippocampus; which includes the subfields subiculum (Sub), CA1, CA2, as well as CA3 and dentate gyrus (DG) which are separated by the endfolial pathway covering most of the long axis of the hippocampus. We provide detailed instructions alongside slice-by-slice segmentations to ease learning for the untrained but also more experienced raters. Twenty-two subjects were scanned (19–32 yrs, mean age = 26 years, 12 females) with a turbo spin echo (TSE) T2-weighted MRI sequence with high-resolution oblique coronal slices oriented orthogonal to the long axis of the hippocampus (in-plane resolution 0.44 × 0.44 mm2) and 1.0 mm slice thickness. The scans were manually delineated by two experienced raters, to assess intra- and inter-rater reliability. The Dice Similarity Index (DSI) was above 0.78 for all regions and the Intraclass Correlation Coefficients (ICC) were between 0.76 to 0.99 both for intra- and inter-rater reliability. In conclusion, this study presents a fine-grained and comprehensive segmentation protocol for MTL structures at 7 T MRI that closely follows recent knowledge from anatomical studies. More specific subdivisions (e.g. area 35 and 36 in PrC, and the separation of DG and CA3) may pave the way for more precise delineations thereby enabling the detection of early volumetric changes in dementia and neuropsychiatric diseases.

Temporal lobe anatomy: eight imaging signs to facilitate interpretation of MRI.

The temporal lobe is anatomically and functionally complex. However, relatively few radiologic signs are described to facilitate recognition of temporal lobe sulci and gyri in clinical practice. We devised and tested 8 radiologic signs of temporal lobe anatomy. Images from volumetric magnetization-prepared rapid gradient-echo imaging were analyzed of 100 temporal lobes from 26 female and 24 male patients. Patient age ranged from 1 to 79years (mean 19years; standard deviation 16years). Standardized axial, coronal, and sagittal planes were evaluated and cross-referenced. Eight signs to delineate the superior temporal gyrus, Heschl gyrus (HG), parahippocampal gyrus, rhinal sulcus, collateral sulcus proper, or the occipitotemporal sulcus, or a combination, were evaluated in the sagittal or axial plane. Two neuroradiologists independently evaluated each sign; the sign was considered present only with positive reader agreement. All 8 signs were present in most patients. The most frequent signs were the posterior insular corner to identify HG in the axial plane (100%), pointed STG to identify STG in the axial plane (98%), and parahippocampal Y to identify the posterior parahippocampal gyrus in the sagittal plane (98%). The frequencies were similar between the right and left cerebral hemispheres. Temporal lobe gyri and sulci can be reliably identified in multiple planes using anatomic signs.

Changes in medial temporal lobe anatomy quantified using probabilistic atlas construction and surface diffeomorphometry

Changes in medial temporal lobe anatomy quantified using probabilistic atlas construction and surface diffeomorphometry

Changes in medial temporal lobe anatomy quantified using probabilistic atlas construction and surface diffeomorphometry

Changes in medial temporal lobe anatomy quantified using probabilistic atlas construction and surface diffeomorphometry

Using the zygomatic root as a reference point in temporal lobe surgery

The zygomatic root (ZR) is an anatomic landmark routinely identified during cranial procedures. Traditionally, it has been used for identification of structures other than temporal lobe anatomy. The aim of this study was to define the structural relationship between the ZR and temporal lobe anatomy and provide a consistent landmark to guide surgical dissection. To our knowledge, there have been no studies demonstrating this relationship. Eighteen DICOM series were analyzed. 2 mm axial MRI slices were reconstructed with the x-axis centered along the zygoma. The posterior point of the ZR that marks the beginning of the groove between the zygoma and temporal bone was identified on all images. Several measures were taken to quantify the relationship of the zygomatic root to surgical landmarks used during temporal lobe surgery. The inferior temporal gyrus was always found just medial to the ZR. The mean distance between the ZR and temporal pole was 2.75 cm on the right and 2.78 cm on the left. The tip of the temporal horn was located on average 2.4 cm (left) and 2.31 cm (right) medial to the ZR. The tip of the temporal horn was found to be an average distance of 1 mm (left and right) posterior and 1.34 cm (left and right) superior to the ZR. All distances were measured orthogonally for each of the x, y, and z axes. The zygomatic root is an easily identifiable and consistent bony landmark that can serve as an adjuvant to neuronavigation for identification of temporal lobe surgical anatomy.

How I do it – selective amygdalohippocampectomy via subtemporal approach

Surgery is superior over medicamentous treatment of pharmacoresistant mesial temporal lobe epilepsy caused by hippocampal sclerosis. The armamentarium of surgical procedures comprises standard temporal lobectomy and more selective procedures. Selective amygdalohippocampectomy can be performed via transcortical, transsylvian or subtemporal approach. Describe the selective amygdalohippocampectomy through the subtemporal approach After the detailed preoperative epilepsy evaluation, surgery can be offered to pharmacoresistant epilepsy patient with hippocampal sclerosis. Selective amygdalohippocampectomy can be safely performed through the subtemporal approach. The good knowledge of the mesial temporal lobe anatomy is necessary when performing this procedure.

Stereotactic Atlas-Based Depth Electrode Localization in the Human Amygdala

Background: The efficacy of stereotactic neurosurgery procedures is critically dependent on the accuracy of the device placement procedure. The first step in this process involves correctly identifying the target location in three-dimensional brain space. In some clinical applications, this targeting process cannot be accomplished using MRI images of gross anatomical structures alone. The amygdala complex is a case in point, in that it consists of multiple histologically defined subnuclei with different functional characteristics. Methods: In this report, we describe an elastic atlas brain-morphing method that projects amygdala subnuclear anatomical information onto the MRI volumes of individual subjects. Results: The accuracy of this method was tested in 5 representative subjects using quantitative image-matching analytical techniques. The results demonstrate a high degree of intersubject variability in medial temporal lobe anatomy, and markedly superior anatomical matching performance by the elastic morphing method compared to Affine transformation. Conclusion: Nonlinear elastic morphing technique provides superior performance on fitting atlas templates to individual brain. The strengths and limitations of this and other atlas morphing methods are discussed in the context of emerging functional neurosurgery applications.

Mesial temporal lobe anatomy and its relationships with surrounding structures

To explore the anatomy of mesial temporal lobe and the relationships between the mesial temporal lobe and its surrounding structures. Twenty formalin-fixed adult cadaveric heads after perfusion of the arteries and veins with colored latex were studied under microscope, and photographs were taken. The hippocampus, fimbria, amygdala and choroidal fissure constituting the mesial temporal lobe were intraventricular structures, and uncus, parahippocampal gyrus, and dentate gyrus were extraventricular structures. The apex of the uncus pointed to the oculomotor nerve and posterior communicating artery. The anterior segment faced the cistern of Sylvius, ICA and MCA. The posterior segment faced the Crus cerebri. The uncus was related medially to the posterior cerebral artery, anterior choroidal artery, and optic tract. The structures of the mesial temporal lobe are complicated, so understanding of the mesial temporal lobe anatomy and the relationships between the mesial temporal lobe and its surrounding structures is conducive to the microsurgical operations of the mesial temporal lobe lesions.

Visual field deficits in conventional anterior temporal lobectomy versus amygdalohippocampectomy. Egan RA, Shults WT, So N, Burchiel K, Kellogg JX, Salinsky M. Neurology 2000;55:1818–1822.

Visual field defects occur frequently after temporal lobe surgery for epilepsy because of the location of the optic radiations in the temporal lobe. The traditional surgery employed is anterior temporal lobectomy (ATL), often resulting in contralateral homonymous superior quadrantanopias. Another surgical procedure, amygdalohippocampectomy (AH), solely removes the epileptogenic mesial temporal lobe structures including the hippocampus, uncus, and amygdala, presumably sparing the lateral temporal lobe anatomy and, hence, the optic radiations. The objective of this study was to evaluate and identify the incidence of visual field defects after ATL versus AH. All patients had intractable seizures and mesial temporal sclerosis, small tumors localized to only the uncus, amygdala, or hippocampus, or no known pathology. Post-operative kinetic field testing using the 14e isopter on a Goldmann perimeter was performed 30 days or more after surgery. Of 29 patients examined, 14 underwent AH and 15 had ATL. Four of 14 AH patients (28%) had a visual field defect at 10 degrees from center and 11 of 14 (78%) had a visual field defect at 40 degrees. One of 15 ATL patients (7%) had a visual field defect at 10 degrees from center and 11 of 15 (73%) had a visual field defect at 40 degrees. There was no significant difference between surgery types. Although it was hoped that AH would cause fewer or no visual field defects when compared with ATL, this was not the case. The mechanism of injury from both procedures is presumably direct trauma to the optic radiations while accessing the mesial temporal lobe structures. Interestingly, all patients in the study were asymptomatic for their visual field defects.—Nancy J. Newman

The Kraepelinian Dichotomy: Evidence From Developmental and Neuroimaging Studies

The Kraepelinian Dichotomy: Evidence From Developmental and Neuroimaging Studies

Microsurgical anatomy of the temporal lobe: part 1: mesial temporal lobe anatomy and its vascular relationships as applied to amygdalohippocampectomy.

We review the anatomy of the mesial temporal lobe region, establishing the relationships among the intraventricular, extraventricular, and surrounding vascular structures and their angiographic characterization. We also demonstrate the clinical application of these anatomic landmarks in an anatomic temporal lobectomy plus amygdalohippocampectomy. Fifty-two adult cadaveric hemispheres and 12 adult cadaveric heads were studied, using a magnification ranging from 3x to 40x, after perfusion of the arteries and veins with colored latex. The intraventricular elements are the hippocampus, fimbria, amygdala, and choroidal fissure; the extraventricular elements are the uncus and parahippocampal and dentate gyri. The uncus has an anterior segment, an apex, and a posterior segment that has an inferior and a posteromedial surface; the uncus is related medially to cisternal elements and laterally to intraventricular elements. The anterior segment is related to the proximal sylvian fissure, internal carotid artery, proximal M1 segment of the middle cerebral artery, proximal cisternal anterior choroidal artery, and amygdala. The apex is related to the oculomotor nerve, uncal recess, and amygdala; the posteromedial surface is related to the P2A segment of the posterior cerebral artery inferiorly, to the distal cisternal anterior choroidal artery superiorly, and to the head of the hippocampus and amygdala intraventricularly. The choroidal fissure is located between the thalamus and fimbria; it begins at the inferior choroidal point behind the head of the hippocampus and constitutes the medial wall of the posterior two-thirds of the temporal horn. Not only is the knowledge of these relations useful to angiographically characterize the mesial temporal region, but it has also proven to be of extreme value during microsurgeries involving this region.

Ventromedial temporal lobe anatomy, with comments on Alzheimer's disease and temporal injury.

The ventromedial temporal area has a complicated topography and neuroanatomy that has yielded secrets only grudgingly. The major features of surface topography are reviewed here as well as recent neuroanatomical findings that establish the ventromedial temporal area as both a recipient of cortical input and the origin for widespread output back to the cortex. The devastating involvement of all ventromedial temporal areas in Alzheimer's disease is highlighted, and comments are offered on the tentorium cerebelli and on mechanical injury to the area.