Sulcal Anatomy Research Articles

Neuroanatomical and Functional Dissociations between Variably Present Anterior Lateral Prefrontal Sulci.

The lateral prefrontal cortex (LPFC) is an evolutionarily expanded region in humans that is critical for numerous complex functions, many of which are largely hominoid specific. Although recent work shows that the presence or absence of specific sulci in anterior LPFC is associated with cognitive performance across age groups, it is unknown whether the presence of these structures relates to individual differences in the functional organization of LPFC. To fill this gap in knowledge, we leveraged multimodal neuroimaging data from two samples encompassing 82 young adult humans (aged 22-36 years) and show that the dorsal and ventral components of the paraintermediate frontal sulcus, or pimfs, present distinct morphological (surface area), architectural (thickness and myelination), and functional (resting-state connectivity networks) properties. We further contextualize the pimfs components within classic and modern cortical parcellations. Taken together, the dorsal and ventral pimfs components mark transitions in LPFC anatomy and function, across metrics and parcellations. These results emphasize that the pimfs is a critical structure to consider when examining individual differences in the anatomical and functional organization of LPFC and suggest that future individual-level parcellations could benefit from incorporating sulcal anatomy when delineating LPFC cortical regions.

Anatomo-functional correspondence in the voice-selective regions of human prefrontal cortex

Group level analyses of functional regions involved in voice perception show evidence of 3 sets of bilateral voice-sensitive activations in the human prefrontal cortex, named the anterior, middle and posterior Frontal Voice Areas (FVAs). However, the relationship with the underlying sulcal anatomy, highly variable in this region, is still unknown. We examined the inter-individual variability of the FVAs in conjunction with the sulcal anatomy. To do so, anatomical and functional MRI scans from 74 subjects were analyzed to generate individual contrast maps of the FVAs and relate them to each subject's manually labeled prefrontal sulci. We report two major results. First, the frontal activations for the voice are significantly associated with the sulcal anatomy. Second, this correspondence with the sulcal anatomy at the individual level is a better predictor than coordinates in the MNI space. These findings offer new perspectives for the understanding of anatomical-functional correspondences in this complex cortical region. They also shed light on the importance of considering individual-specific variations in subject's anatomy.

Suprafloccular transhorizontal fissure approach to the cerebellopontine angle: an anatomical study with case series.

The suprafloccular transhorizontal fissure approach is a modified variant of the classical retrosigmoid approach option to be chosen for cerebellopontine angle lesions. In this study, we aimed to demonstrate a previously described but not widely used method, the suprafloccular transhorizontal fissure approach with anatomical dissection on the cadaver, accompanied by a case presentation with the largest clinical series in the literature. Klingler's protocol was used to prepare 8 silicone injected and 8 non-silicone injected human hemispheres. A total of 210 patients who underwent surgery in the cerebellopontine angle between 2019 and 2022 were evaluated in our clinic. Of these, the suprafloccular transhorizontal fissure approach was applied in 33 patient, and it was successful in 26 patient, but this approach could not be achieved in 7 patients. The transhorizontal fissure is a fissure in the cerebellum located between the superior semilunar lobule and the inferior semilunar lobule. In the 26 patients we operated with the suprafloccular transhorizontal fissure approach, there was no need for retraction and no complications developed. However, in 7 patients, this fissure could not be dissected due to adhesions. Suprafloccular approach is an alternative to the classical retrosigmoid approach in tumours smaller than 2 cm, medially localised with little cerebellar oedema and neurovascular compression syndrome. Because in this approach, no cerebellum retraction is required, vascular structures are better preserved and the surgical time is shortened. This approach can be applied in smaller tumours than 2 cm when the sulcal anatomy is appropriate.

Cortical Morphology and White Matter Tractography of Three Phylogenetically Distant Primates: Evidence for a Simian Elaboration.

Comparative neuroimaging has been used to identify changes in white matter architecture across primate species phylogenetically close to humans, but few have compared the phylogenetically distant species. Here, we acquired postmortem diffusion imaging data from ring-tailed lemurs (Lemur catta), black-capped squirrel monkeys (Saimiri boliviensis), and rhesus macaques (Macaca mulatta). We were able to establish templates and surfaces allowing us to investigate sulcal, cortical, and white matter anatomy. The results demonstrate an expansion of the frontal projections of the superior longitudinal fasciculus complex in squirrel monkeys and rhesus macaques compared to ring-tailed lemurs, which correlates with sulcal anatomy and the lemur’s smaller prefrontal granular cortex. The connectivity of the ventral pathway in the parietal region is also comparatively reduced in ring-tailed lemurs, with the posterior projections of the inferior longitudinal fasciculus not extending toward parietal cortical areas as in the other species. In the squirrel monkeys we note a very specific occipito-parietal anatomy that is apparent in their surface anatomy and the expansion of the posterior projections of the optical radiation. Our study supports the hypothesis that the connectivity of the prefrontal-parietal regions became relatively elaborated in the simian lineage after divergence from the prosimian lineage.

The Paracingulate Sulcus Is a Unique Feature of the Medial Frontal Cortex Shared by Great Apes and Humans

Primate brains display a wide range of variation in size and cerebral gyrification, leading to the appearance of novel sulci in particular groups of species. We investigated sulcal organization in the medial frontal cortex of great apes, with a particular focus on the paracingulate sulcus (PCGS). Until recently, the presence of the PCGS was thought to be a structural feature unique to the human brain. However, upon closer examination, the PCGS has been observed as a variable feature that also may appear in chimpanzee brains. To understand the evolutionary origins of the sulcal anatomy in the medial frontal cortex of apes, we examined high-resolution MRI scans for the presence or absence of the PCGS and, when present, measured its length in a sample of ape brains (chimpanzees, bonobos, gorillas, orangutans, gibbons, and siamangs). We found that the PCGS is variable in its appearance among these species, being present in 23 to 50% of great ape individuals depending on the species, but not present in gibbons or siamangs. We did not find population level hemispheric lateralization patterns or sex differences in PCGS presence across species, and we did not detect a relationship between cerebral volume and PCGS occurrence or length. Our data suggest that the PCGS is a common sulcal variant present in great apes and humans due to a shared evolutionary ancestry.

Skin landmarks to main cerebral structures: how to identify the main cerebral sulci? An anatomical study.

Neuronavigation is used in neurosurgical practice to locate the cortical structures. If this tool is unavailable, basic anatomical knowledge should be used. Craniometry has been rarely detailed in recent literature, systematically using bony landmarks. The aim of this study is to describe skin landmarks for neurosurgical practice. Dissection of 10 hemispheres with insertion of radio-opaque markers within the limits of lateral sulcus, central and pre-central sulci, and preoccipital notch. Computed tomography was performed in all cases and multiplanar reconstructions were performed. Maximal intensity projection (MIP) fusion images were used for measurements between known skin landmarks and sulci of interests. The Anterior Sylvian Point is measured 31.8 ± 2.8mm behind the orbital wall, 36.9 ± 3mm above the zygomatic arch. The horizontal part of the lateral sulcus is measured 59 ± 6mm above the tragus. The Superior Rolandic Point is measured 190.7 ± 4.5mm behind the nasion. The Pre-occipital Notch is measured 37.0 ± 6.9mm above the tragus and 67.1 ± 6.4mm behind. The Ideal Entry Points (IEP) for ventricular punctures are measured 120.2 ± 7mm behind the nasion and 33.8 ± 3mm laterally for the frontal IEP, and 61.3mm ± 2.5mm above and 64.7 ± 6.8mm behind the tragus for the parieto-occipital IEP. In this study, we described simple skin landmarks for lateral sulcus, central sulcus, preoccipital notch, and an IEP for ventricular drainage. Precise knowledge of brain sulcal anatomy will guide patient's positioning, skin incision, and craniotomies; and permits checking of imaging data provided by neuronavigation systems.

Unsupervised machine learning can delineate central sulcus by using the spatiotemporal characteristic of somatosensory evoked potentials

Objective. Somatosensory evoked potentials (SSEPs) recorded with electrocorticography (ECoG) for central sulcus (CS) identification is a widely accepted procedure in routine intraoperative neurophysiological monitoring. Clinical practices test the short-latency SSEPs for the phase reversal over strip electrodes. However, assessments based on waveform morphology are susceptible to variations in interpretations due to the hand area’s localized nature and usually require multiple electrode placements or electrode relocation. We investigated the feasibility of unsupervised delineation of the CS by using the spatiotemporal patterns of the SSEP captured with the ECoG grid. Approach. Intraoperatively, SSEPs were recorded from eight patients using ECoG grids placed over the sensorimotor cortex. Neurosurgeons blinded to the electrophysiology identified the sensory and motor gyri using neuronavigation based on sulcal anatomy. We quantified the most discriminatory time points in SSEPs temporal profile between the primary motor (M1) and somatosensory (S1) cortex using the Fisher discrimination criterion. We visualized the amplitude gradient of the SSEP over a 2D heat map to provide visual feedback for the delineation of the CS based on electrophysiology. Subsequently, we employed spectral clustering using the entire the SSEP waveform without selecting any time points and grouped ECoG channels in an unsupervised fashion. Main results. Consistently in all patients, two different time points provided almost equal discrimination between anterior and posterior channels, which vividly outlined the CS when we viewed the SSEP amplitude distribution as a spatial 2D heat map. The first discriminative time point was in proximity to the conventionally favored ∼20 ms peak (N20), and the second time point was slightly later than the markedly high ∼30 ms peak (P30). Still, the location of these time points varied noticeably across subjects. Unsupervised clustering approach separated the anterior and posterior channels with an accuracy of 96.3% based on the time derivative of the SSEP trace without the need for a subject-specific time point selection. In contrast, the raw trace resulted in an accuracy of 88.0%. Significance. We show that the unsupervised clustering of the SSEP trace assessed with subdural electrode grids can delineate the CS automatically with high precision, and the constructed heat maps can localize the motor cortex. We anticipate that the spatiotemporal patterns of SSEP fused with machine learning can serve as a useful tool to assist in surgical planning.

Brain morphometric abnormalities in boys with attention-deficit/hyperactivity disorder revealed by sulcal pits-based analyses.

AimAttention‐deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder associated with widespread brain morphological abnormalities. Here, we utilized a sulcal pits‐based method to provide new insight into the atypical cortical folding morphology in ADHD.MethodsSulcal pits, the locally deepest points in each fold, were first extracted from magnetic resonance imaging data of 183 boys with ADHD (10.62 ± 1.96 years) and 167 age‐ and gender‐matched typically developing controls (10.70 ± 1.73 years). Then, the geometrical properties of sulcal pits were statistically compared between ADHD and controls.ResultsOur results demonstrated that the number of sulcal pits was reduced and confined to the superficial secondary sulci in the ADHD group relative to controls (P < .05). We also found that ADHD boys were associated with significantly increased pit depth in the left superior frontal junction, circular insular sulcus, right inferior frontal junction, and bilateral cingulate sulcus, as well as significantly decreased pit depth in the bilateral orbital sulcus (P < .05, corrected).ConclusionThe experimental findings reveal atypical sulcal anatomy in boys with ADHD and support the feasibility of sulcal pits as anatomic landmarks for disease diagnosis.

The telencephalon of the Göttingen minipig, cytoarchitecture and cortical surface anatomy.

During the last 20years pigs have become increasingly popular in large animal translational neuroscience research as an economical and ethical feasible substitute to non-human primates. The anatomy of the pig telencephalon is, however, not well known. We present, accordingly, a detailed description of the surface anatomy and cytoarchitecture of the Göttingen minipig telencephalon based on macrophotos and consecutive high-power microphotographs of 15μm thick paraffin embedded Nissl-stained coronal sections. In 1-year-old specimens the formalin perfused brain measures approximately 55×47×36mm (length, width, height) and weighs around 69g. The telencephalic part of the Göttingen minipig cerebrum covers a large surface area, which can be divided into a neocortical gyrencephalic part located dorsal to the rhinal fissure, and a ventral subrhinal part dominated by olfactory, amygdaloid, septal, and hippocampal structures. This part of the telencephalon is named the subrhinal lobe, and based on cytoarchitectural and sulcal anatomy, can be discerned from the remaining dorsally located neocortical perirhinal/insular, pericallosal, frontal, parietal, temporal, and occipital lobes. The inner subcortical structure of the minipig telencephalon is dominated by a prominent ventricular system and large basal ganglia, wherein the putamen and the caudate nucleus posterior and dorsally are separated into two entities by the internal capsule, whereas both structures ventrally fuse into a large accumbens nucleus. The presented anatomical data is accompanied by surface renderings and high-power macrophotographs illustrating the telencephalic sulcal pattern, and the localization of the identified lobes and cytoarchitectonic areas. Additionally, 24 representative Nissl-stained telencephalic coronal sections are presented as supplementary material in atlas form on http://www.cense.dk/minipig_atlas/index.html and referred to as S1-S24 throughout the manuscript.

Subdivision of Broca's region based on individual‐level functional connectivity

Broca's region is composed of two adjacent cytoarchitectonic areas, 44 and 45, which have distinct connectivity to superior temporal and inferior parietal regions in both macaque monkeys and humans. The current study aimed to make use of prior knowledge of sulcal anatomy and resting-state functional connectivity, together with a novel visualization technique, to manually parcellate areas 44 and 45 in individual brains invivo. One hundred and one resting-state functional magnetic resonance imaging datasets from the Human Connectome Project were used. Left-hemisphere surface-based correlation matrices were computed and visualized in brainGL. By observation of differences in the connectivity patterns of neighbouring nodes, areas 44 and 45 were manually parcellated in individual brains, and then compared at the group-level. Additionally, the manual labelling approach was compared with parcellation results based on several data-driven clustering techniques. Areas 44 and 45 could be clearly distinguished from each other in all individuals, and the manual segmentation method showed high test-retest reliability. Group-level probability maps of areas 44 and 45 showed spatial consistency across individuals, and corresponded well to cytoarchitectonic probability maps. Group-level connectivity maps were consistent with previous studies showing distinct connectivity patterns of areas 44 and 45. Data-driven parcellation techniques produced clusters with varying degrees of spatial overlap with the manual labels, indicating the need for further investigation and validation of machine learning cortical segmentation approaches. The current study provides a reliable method for individual-level cortical parcellation that could be applied to regions distinguishable by even the most subtle differences in patterns of functional connectivity.

Training for brain tumour resection: a realistic model with easy accessibility.

Resection of intrinsic and extrinsic brain tumours requires an understanding of sulcal and gyral anatomy, familiarity with tissue consistency and tissue manipulation. As yet, these skills are acquired by observation and supervised manipulation during surgery, thus accepting a potential learning curve at the expense of the patient in a live surgical situation. A brain tumour model could ensure optimised manual skills and understanding of surgical anatomy acquired in an elective and relaxed teaching situation. We report and evaluate a brain tumour model, regarding availability, realistic representation of sulcal and gyral anatomy and tissue consistency. Freshly prepared agar-agar solution with different concentrations was added with highlighter ink and injected into fresh sheep brains. Hardened agar-agar solution formed masses comparable to malignant brain tumours. Variation of the agar-agar concentration influenced diffusion of agar-agar solution in the adjacent brain tissue. Higher concentrated agar-agar solutions formed sharply delimitated masses mimicking cerebral metastases and lower concentrated agar-agar solutions tended to diffuse into the adjacent cerebral tissue. Adding highlighter ink to the agar-agar solution produced fluorescence after blue light excitation comparable to the 5-ALA induced fluorescence of malignant glioma. The described in vitro sheep brain tumour model is simple and realistic, available practically everywhere and cheap. Therefore, it could be useful for young neurosurgical residents to acquire basic neuro-oncological skills, experiencing properties of the cerebral brain texture and its haptic perception and to learn handling of neurosurgical equipment.

Middle short gyrus of the insula implicated in speech production: Intracerebral electric stimulation of patients with epilepsy by an oblique approach using a robotized arm

Introduction Few data exist about of the role of the insula in the processing of speech. The data of this study suggests the involvement of the upper middle short gyrus in speech production. Materials and methods For this study, we included 25 patients suffering from severe drug refractory partial epilepsy were investigated by stereo-electroencephalography (SEEG). At least one electrode was used to explore the insular cortex using an oblique approach (trans-frontal or trans-parietal) and who had a normal insular region. In total, 313 stimulations were performed in 27 insula. Eighty-three responses induced by insular electrical stimulation (ES), eight (9.6%) were reported by five patients as speech arrest (5 responses) and a lowering of voice intensity (3 responses). The stereotactic approach allows us to identify the stimulation sites within the insular cortex in terms of its gyri and sulci. Also, the stimulation sites were anatomically localized via image fusion between pre-implantation 3D MRI and post-implantation 3D CT scans revealing the electrode contacts. Results Eight responses were reported as speech disturbances. 7 among them were evoked in 4 patients by stimulation in the middle short gyrus (8.4% of total responses, and 25.9% of responses evoked in the middle short gyrus). The site of the 8th response was in the post-central insular gyrus in the same insular region where the oropharyngeal responses induced by other ES (pharyngeal construction) in this study. The data suggest the involvement of the middle short gyrus of the insula in the procedures of language. These responses were evoked in the non-dominant side four times out of five. This study provides evidence that the middle short gyrus of the insula in both hemispheres responds to ES producing speech disturbances. Conclusion The results of this study are the first to report language disorders in humans evoked by electrical stimulation of the insular cortex during SEEG explorations by electrodes implanted by oblique approach in terms of gyral and sulcal anatomy.

Atypical sulcal anatomy in young children with autism spectrum disorder.

Autism spectrum disorder is associated with an altered early brain development. However, the specific cortical structure abnormalities underlying this disorder remain largely unknown. Nonetheless, atypical cortical folding provides lingering evidence of early disruptions in neurodevelopmental processes and identifying changes in the geometry of cortical sulci is of primary interest for characterizing these structural abnormalities in autism and their evolution over the first stages of brain development. Here, we applied state-of-the-art sulcus-based morphometry methods to a large highly-selective cohort of 73 young male children of age spanning from 18 to 108 months. Moreover, such large cohort was selected through extensive behavioral assessments and stringent inclusion criteria for the group of 59 children with autism. After manual labeling of 59 different sulci in each hemisphere, we computed multiple shape descriptors for each single sulcus element, hereby separating the folding measurement into distinct factors such as the length and depth of the sulcus. We demonstrated that the central, intraparietal and frontal medial sulci showed a significant and consistent pattern of abnormalities across our different geometrical indices. We also found that autistic and control children exhibited strikingly different relationships between age and structural changes in brain morphology. Lastly, the different measures of sulcus shapes were correlated with the CARS and ADOS scores that are specific to the autistic pathology and indices of symptom severity. Inherently, these structural abnormalities are confined to regions that are functionally relevant with respect to cognitive disorders in ASD. In contrast to those previously reported in adults, it is very unlikely that these abnormalities originate from general compensatory mechanisms unrelated to the primary pathology. Rather, they most probably reflect an early disruption on developmental trajectory that could be part of the primary pathology.

Comparative neuroanatomical parcellation of the human and nonhuman primate temporal pole

The temporal pole is unique to nonhuman and human primates, although other species also present temporal cortex. A clear distinction is made between the gross anatomical, macroscopic temporal pole, located at the tip of the temporal lobe, and the temporal polar cortex, which is a general term that encompasses all reported divisions and can be applied to both nonhuman and human primates. In the 19th century early neuroanatomists identified the temporal polar cortex as a different entity, independent from the remainder of the temporal lobe. More recently, the temporal polar cortex has been subdivided into different fields. The analysis of the different portions that make up the temporal polar cortex was first described in the nonhuman primate, and later on in humans. In this review we examine the historical course of the concepts about the extension, structure, and main cytoarchitectonic areas. The different descriptions are presented in chronological order and their relevance is discussed. In general, some common features arise in nonhuman and human primates temporopolar cortex, namely, an increased thickness of this cortical area, a predominant dysgranular type of cortex, and a more restricted extension in humans relative to earlier accounts. A common pattern of cytoarchitectonic areas results from the criteria of previous authors, although the sulcal anatomy of the human temporal pole has great variability. The understanding of the extension, composition, and limits of the temporal polar cortex is crucial for identification of separate regions in neuroimaging studies. J. Comp. Neurol. 521:4163-4176, 2013. © 2013 Wiley Periodicals, Inc.

Anterior cingulate morphology in people at genetic high-risk of schizophrenia

BackgroundMorphological abnormalities of the anterior cingulate (AC) occur in patients with schizophrenia and in symptomatic high-risk individuals, and may be predictive of subsequent psychosis. We investigated AC sulcal morphology in the Edinburgh High Risk Study cohort to see if such abnormalities are evident and predict psychosis in patients’ relatives. We also investigated the association of the cingulate sulcus (CS) and paracingulate sulcus (PCS) variants with intelligence quotient (IQ). Patients and methodsWe compared cingulate and paracingulate sulcal anatomy, using reliable standardised measurements, blind to group membership, in those at high genetic risk (n=146), first episode patients (n=34) and healthy controls (n=36); and compared high-risk subjects who did (n=17) or did not develop schizophrenia. ResultsInterruptions of the cingulate sulcus were more common in high-risk individuals and in those with schizophrenia, in both hemispheres, compared to controls. When separated by gender, these results were only present in males in the left hemisphere and only in females in the right hemisphere. A well-formed paracingulate sulcus was less common in high-risk participants and patients with schizophrenia, compared to controls; but this association was only present in males. These morphological variants of the paracingulate sulcus and the continuous cingulate sulcus were also associated with the higher IQ in male high-risk individuals. ConclusionsAn interrupted cingulate sulcus pattern in both males and females and paracingulate morphology in males are associated with increased genetic risk of schizophrenia. Associations between cingulate and paracingulate morphology and premorbid IQ scores provide evidence that intellectual ability could be related to particular cytoarchitectural brain regions. Given that these sulci develop in early fetal life, such findings presumably reflect early neurodevelopmental abnormalities of genetic origin, although environmental effects and interactions cannot be ruled out.

Neural activity underlying the integration of trajectory information

The perception of optic flow relies on the integration of many local pieces of information to generate a global percept of motion direction. This processing of motion requires mechanisms that can integrate information over space and time. Here we investigate the temporal integration of motion direction across early visual areas using EEG source-imaging and participants who each had fMRI-mapped retinotopic and functionally defined visual areas. These individually defined regions of interest allowed us to average data across participants in a way that respects individual differences in sulcal anatomy and electrode placement. We used a random-dot motion stimulus with individual dots updating at 30 Hz that alternated between globally coherent motion and incoherent motion at 1 Hz. During the incoherent interval, each dot had a random direction on each update, but during the coherent interval we systematically varied the duration any single dot spent on a consistent trajectory before being extinguished and replaced with a dot in a new random location. The local information provided by the individual dots was tagged with 30 Hz while the global alternation from coherent flow to incoherent boil was tagged at 1 Hz. These tags enable us to distinguish responses associated with global and local information. We find that activity in dorsal visual areas increased monotonically with longer dot trajectories. While activity from human MT complex differentiates coherent from incoherent global flow, its response does not grow with increasing consistency of trajectory. In addition we find a signature of nonlinear coupling between local information updates and the presence of coherent motion. Specifically, in dorsal visual areas the response at the frequency tagged by the local dot refresh rate increases during the coherent motion interval. These results suggest that dorsal visual areas such as V3A are responsible for the integration of motion information over extended trajectories.

Reoperation after selective amygdalohippocampectomy: an MRI analysis of the extent of temporomesial resection in ten cases

Selective amygdalohippocampectomy (SAHE) yields 60-80% of patients with medically refractory mesial temporal lobe epilepsy seizure-free and seems to be equally effective compared to the more extended temporal lobe resections. The resection of the entire entorhinal cortex (EC) is of crucial importance to warrant complete seizure control for those patients. Thus, evidence of residual EC could be a predictor of a potentially successful reoperation in patients with recurrent seizures after SAHE. We performed an analysis of preoperative and postoperative magnetic resonance imaging (MRI) in patients who underwent a reoperation after an unsuccessful transsylvian SAHE to assess the presence of residual EC before reoperation and to determine whether certain anatomical variants may dispose patients to incomplete resection of EC. Ten patients who underwent reoperation after SAHE for the recurrence of medically refractory seizures were studied. MRI after SAHE was assessed for the presence of residual EC using T2-weighted and inversion recovery sequences perpendicularly to the main axis of the hippocampus. The results were compared with a control group of ten patients who became seizure-free after SAHE. In the nine patients of the study group, the sulcal anatomy of the basal temporal lobe was graphically outlined and analysed on MRI scans performed before SAHE to characterise the sulcal boundaries of the EC. Residual EC was found in nine of ten patients and was absent in the control group. After reoperation (median follow-up of 36.5 months), eight out of ten patients were completely seizure-free. In seven out of nine patients, a discontinuous course of the lateral sulcal boundaries of the EC was determined. Careful analysis of MRI verified residual mesiotemporal structures in the majority of patients who became seizure-free after reoperation. Certain temporobasal sulcal patterns might dispose for a higher risk of incomplete resection of the EC. The study confirms that reoperation is an effective treatment modality for patients with recurrent seizures after transsylvian SAHE.

Paracingulate sulcus asymmetry; Sex difference, correlation with semantic fluency and change over time in adolescent onset psychosis

The left paracingulate sulcus (PCS) is longer than the right and the adjacent cortex is activated by the generation of words. In adult patients with chronic schizophrenia the anatomical asymmetry is reduced. In 35 controls and 38 adolescents with schizophrenia or schizoaffective disorder (mean age = 16 years) we found that semantic verbal fluency correlated with leftward PCS asymmetry in controls but not in patients. At intake, PCS length did not differ between patients and controls, but at follow-up (13 controls, 10 patients, mean age = 18 years) PCS asymmetry (comprising both increasing left and decreasing right length) increased significantly, the increase was greater in males than in females, and there was a trend for a diagnosis ⁎ sex ⁎ side ⁎ time interaction such that in controls leftward PCS asymmetry increased, while in patients of both sexes there was convergence toward symmetry. Thus sulcal anatomy develops differentially in the two sexes during adolescence, and the pattern of asymmetric sex-dependent change over time may distinguish patients with psychosis from controls. Greater change in asymmetry during adolescence may explain earlier age of onset in males and greater deficits in verbal fluency.

A possible human homologue of the macaque V6A

We have recently mapped the retinotopic organization of the area V6 in the human parieto-occipital sulcus thanks to a wide-field retinotopic stimulation, up to 168 degrees (Pitzalis et al., 2004). In monkey, dorsal and anterior to V6 there is the visuomotor area V6A. Monkey V6A is retinotopically less organized than V6, showing only a rough tendency for the eccentricity to increase dorso-ventrally in both the anterior bank of POS and the precuneate cortex (Galletti et al. 1996, 1999a). Visuomotor neurons in V6A have been found to respond more during reaches than during saccades to visual targets. Here we used phase-encoded fMRI, cortical flattening and wide-filed retinotopic mapping to detect the presence in the human POS of a visual area having retinotopic properties similar to those of the macaque area V6A. We also combined event-related fMRI with cortical surface reconstruction, in order to isolate movement-related activity for reaching and saccades in relation to the individual sulcal anatomy. We found an area in the POS located just anteriorly to V6 and medial to V3A which has an inconsistent polar angle representation but a clear trend in the eccentricity maps. In agreement with functional data on monkey V6A, this region of the human brain shows a marginal effect of cue location (contralateral side slightly preferred) and a transient activity during reaching trials stronger than during saccade trials. We propose that this region may be the putative homologous of area V6A.

Sulcal and gyral anatomy of the orbitofrontal cortex in relation to the recurrent artery of Heubner: an anatomical study

The aim of this study is to investigate the sulcal and the gyral anatomy of the orbitofrontal cortex with its arterial supply. Ten gross formaline fixed adult brains (20 hemispheres) were used to show the gyral and sulcal anatomy of the inferior frontal lobe, and its arterial supply. The arteries were investigated with special attention to the relationship between the recurrent artery of Heubner (RAH) and the gyrus rectus (GR). Medial and lateral orbital sulci were connected in 4 right hemispheres, and in 7 of the left. The orbital sulci were connected with olfactory sulcus in one right hemispheres, but not in the left. In the right hemispheres, the RAH traveled across the GR in 7 hemispheres and looped over the posterior aspect of the GR in 3 hemispheres. In the left hemispheres, RAH crossed the GR in 8 and looped over the posterior aspect of the GR before entering the anterior perforating substance in 2 hemispheres. There are considerable variations among the gyri and sulci of the orbitofrontal cortex and it is difficult to describe a precise architectural pattern. The RAH demands special attention during GR resection in aneurysm surgery.