Key points
We performed a prospective electrostimulation study, based on 50 operated intact patients, to acquire accurate MNI coordinates of the functional areas of the somatosensory homunculus.
In ...the contralateral BA1, the hand representation displayed not only medial‐to‐lateral, little‐finger‐to‐thumb, but also rostral‐to‐caudal discrete somatotopy, with the tip of each finger located more caudally than the proximal phalanx.
The analysis of the MNI body coordinates showed rare inter‐individual variations in the medial‐to‐lateral somatotopic organization in these patients with rather different intensity thresholds needed to elicit sensations in different body parts.
We found some similarities but also substantial differences with the previous, seminal works of Penfield and his colleagues.
We propose a new drawing of the human somatosensory homunculus according to MNI space.
In this prospective electrostimulation study, based on 50 operated patients with no sensory deficit and no brain lesion in the postcentral gyrus, we acquired coordinates in the standard MNI space of the functional areas of the somatosensory homunculus. The 3D brain volume of each patient was normalized to that space to obtain the MNI coordinates of the stimulation site locations. For 647 sites stimulated on Brodmann Area 1 (and 1025 in gyri nearby), 258 positive points for somatosensory response (40%) were found in the postcentral gyrus. In the contralateral BA1, the hand representation displayed not only medial‐to‐lateral and little‐finger‐to‐thumb somatotopy, but also rostral‐to‐caudal discrete somatotopy, with the tip of each finger located more caudally than the proximal phalanx. We detected a medial‐to‐lateral, tip‐to‐base tongue organization but no rostral‐to‐caudal functional organization. The analysis of the MNI body coordinates showed rare inter‐individual variations in the medial‐to‐lateral somatotopic organization in these patients with intact somatosensory cortex. Positive stimulations were detected through the ‘on/off’ outbreak effect and discriminative touch sensations were the sensations reported almost exclusively by all patients during stimulation. Mean hand (2.39 mA) and tongue (2.60 mA) positive intensity thresholds were lower (P < 0.05) than the intensities required to elicit sensations in the other parts of the body. Unlike the previous, seminal works of Penfield and colleagues, we detected no sensations such as sense of movement or desire to move, no somatosensory responses outside the postcentral gyrus, and no bilateral responses for face/tongue stimulations. We propose a rationalization of the standard drawing of the somatosensory homunculus according to MNI space.
Key points
We performed a prospective electrostimulation study, based on 50 operated intact patients, to acquire accurate MNI coordinates of the functional areas of the somatosensory homunculus.
In the contralateral BA1, the hand representation displayed not only medial‐to‐lateral, little‐finger‐to‐thumb, but also rostral‐to‐caudal discrete somatotopy, with the tip of each finger located more caudally than the proximal phalanx.
The analysis of the MNI body coordinates showed rare inter‐individual variations in the medial‐to‐lateral somatotopic organization in these patients with rather different intensity thresholds needed to elicit sensations in different body parts.
We found some similarities but also substantial differences with the previous, seminal works of Penfield and his colleagues.
We propose a new drawing of the human somatosensory homunculus according to MNI space.
Key points
We performed a prospective electrostimulation study of the motor homunculus in 100 patients without motor deficit or brain lesion in the precentral gyrus in order to acquire accurate ...Montreal Neurological Institute (MNI) coordinates of the functional areas.
The analysis of 248 body coordinates in the precentral gyrus showed rare inter‐individual variations in the medial‐to‐lateral somatotopic movement organization with quite similar intensity thresholds. Electrostimulation only induced basic and stereotyped movements.
We detected a relative medial‐to‐lateral somatotopy of the wrist/hand/global/individual fingers, with sometimes different sites for an individual muscle or movement.
We found some similarities to, but also substantial differences from, the seminal work of Penfield and colleagues.
We propose an updated version of the human motor homunculus and of its correlation with the somatosensory homunculus, previously defined in MNI space with a similar brain mapping technique.
In this prospective electrostimulation study, based on 100 operated patients without motor deficit or brain lesion in the precentral gyrus, we acquired coordinates of the functional areas of the motor homunculus and normalized them to standard MNI space. Among 608 sites stimulated in the precentral gyrus (and 1937 in gyri nearby), 248 positive points (40%) for motor response were detected – 245 in the precentral gyrus. Positive stimulations were detected through the ‘on/off’ outbreak effect, and only basic movements were detected. We found no significant difference in mean intensity threshold between the motor representations of the fingers (1.94 mA), tongue and lower limbs (both 2.0 mA), or face (2.25 mA). In the precentral gyrus, the evoked body movements displayed a medial‐to‐lateral somatotopy in very small (often <10 mm2) areas. The hand region displayed multiple areas for a specific movement, with areas inducing either global or single‐finger movement (with a relative medial‐to‐lateral somatotopy). Among these tested patients, the somatotopic organization of the intact motor cortex showed little inter‐individual variations. Unlike Penfield and collaborators, we evoked no sensations such as sense of movement or desire to move, and only 2% of motor responses outside the precentral gyrus. We propose a rationalization of the standard drawing of the motor homunculus according to MNI space. We found a somatotopic correlation perpendicular to the central sulcus when matching our motor data to those previously obtained for the somatosensory homunculus.
Key points
We performed a prospective electrostimulation study of the motor homunculus in 100 patients without motor deficit or brain lesion in the precentral gyrus in order to acquire accurate Montreal Neurological Institute (MNI) coordinates of the functional areas.
The analysis of 248 body coordinates in the precentral gyrus showed rare inter‐individual variations in the medial‐to‐lateral somatotopic movement organization with quite similar intensity thresholds. Electrostimulation only induced basic and stereotyped movements.
We detected a relative medial‐to‐lateral somatotopy of the wrist/hand/global/individual fingers, with sometimes different sites for an individual muscle or movement.
We found some similarities to, but also substantial differences from, the seminal work of Penfield and colleagues.
We propose an updated version of the human motor homunculus and of its correlation with the somatosensory homunculus, previously defined in MNI space with a similar brain mapping technique.
Handwriting is a modality of language production whose cerebral substrates remain poorly known although the existence of specific regions is postulated. The description of brain damaged patients with ...agraphia and, more recently, several neuroimaging studies suggest the involvement of different brain regions. However, results vary with the methodological choices made and may not always discriminate between “writing-specific” and motor or linguistic processes shared with other abilities.
We used the “Activation Likelihood Estimate” (ALE) meta-analytical method to identify the cerebral network of areas commonly activated during handwriting in 18 neuroimaging studies published in the literature. Included contrasts were also classified according to the control tasks used, whether non-specific motor/output-control or linguistic/input-control. These data were included in two secondary meta-analyses in order to reveal the functional role of the different areas of this network.
An extensive, mainly left-hemisphere network of 12 cortical and sub-cortical areas was obtained; three of which were considered as primarily writing-specific (left superior frontal sulcus/middle frontal gyrus area, left intraparietal sulcus/superior parietal area, right cerebellum) while others related rather to non-specific motor (primary motor and sensorimotor cortex, supplementary motor area, thalamus and putamen) or linguistic processes (ventral premotor cortex, posterior/inferior temporal cortex).
This meta-analysis provides a description of the cerebral network of handwriting as revealed by various types of neuroimaging experiments and confirms the crucial involvement of the left frontal and superior parietal regions. These findings provide new insights into cognitive processes involved in handwriting and their cerebral substrates.
Time‐to‐contact perception in the brain Baurès, Robin; Fourteau, Marie; Thébault, Salomé ...
Journal of neuroscience research,
February 2021, Letnik:
99, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Time‐to‐contact (TTC) perception refers to the ability of an observer to estimate the remaining time before an object reaches a point in the environment, and is of crucial importance in daily life. ...Noninvasive correlational approaches have identified several brain areas sensitive to TTC information. Here we report the results of two studies, including one during an awake brain surgery, that aimed to identify the specific areas causally engaged in the TTC estimation process. In Study 1, we tested 40 patients with brain tumor in a TTC estimation task. The results showed that four of the six patients with impaired performance had tumors in right upper parietal cortex, although this tumoral location represented only six over 40 patients. In Study 2, 15 patients underwent awake brain surgery electrostimulation mapping to examine the implication of various brain areas in the TTC estimation process. We acquired and normalized to MNI space the coordinates of the functional areas that influenced task performance. Our results seem to demonstrate that the early stage of the TTC estimation process involved specific cortical territories in the ventral region of the right intraparietal sulcus. Downstream processing of TTC could also involve the frontal eye field (middle frontal gyrus) related to ocular search. We also found that deactivating language areas in the left hemisphere interfered with the TTC estimation process. These findings demonstrate a fine grained, cortical representation of TTC processing close to the ventral right intraparietal sulcus and complement those described in other human studies.
What are the brain areas engaged when estimating the time to contact of an approaching ball? Patients undergoing an awake brain surgery performed the task while various areas were stimulated. The performances were assessed compared to a presurgery baseline. Results showed a direct and causal involvement of areas near the intraparietal sulcus, and indirect involvement of areas related to the language.
We investigated the challenging diagnostic case of a ventricular cystic glioneuronal tumor with papillary features, by RNA sequencing using the Illumina TruSight RNA Fusion panel. We did not retrieve ...the SLC44A1‐PRKCA fusion gene specific for papillary glioneuronal tumor, but an EWSR1‐PATZ1 fusion transcript. RT‐PCR followed by Sanger sequencing confirmed the EWSR1‐PATZ1 fusion. It matched with canonic EWSR1 fusion oncogene, juxtaposing the entire N‐terminal transcriptional activation domain of EWSR1 gene and the C‐terminal DNA binding domain of a transcription factor gene, PATZ1. PATZ1 protein belongs to the BTB‐ZF (broad‐complex, tramtrack and bric‐à‐brac ‐zinc finger) family. It directly regulates Pou5f1 and Nanog and is essential to maintaining stemness by inhibiting neural differentiation. EWSR1‐PATZ1 fusion is a rare event in tumors: it was only reported in six round cell sarcomas and in three gliomas of three exclusively molecular studies. The first reported glioma was a BRAFV600E negative ganglioglioma, the second a BRAFV600E negative glioneuronal tumor, not otherwise specified and the third, very recently reported, a high grade glioma, not otherwise specified. In our study, forty BRAFV600E negative gangliogliomas were screened by FISH using EWSR1 break‐apart probes. We performed methylation profiling for the index case and for seven out of the ten FISH positive cases. The index case clustered apart from other pediatric low grade glioneuronal entities, and specifically from the well‐defined ganglioglioma methylation group. An additional pediatric intraventricular ganglioglioma clustered slightly more closely with ganglioglioma, but showed differences from the main ganglioglioma group and similarities with the index case. Both cases harbored copy number variations at the PATZ1 locus. EWSR1‐PATZ1 gene fusion might define a new type of glioneuronal tumors, distinct from gangliogliomas.
The use of an awake craniotomy in the treatment of supratentorial lesions is a challenge for both patients and staff in the operation theater.
To assess the safety and effectiveness of an awake ...craniotomy with brain mapping in comparison with a craniotomy performed under general anesthesia.
We prospectively compared 2 groups of patients who underwent surgery for supratentorial lesions: those in whom an awake craniotomy with intraoperative brain mapping was used (AC group, n = 214) and those in whom surgery was performed under general anesthesia (GA group, n = 361, including 72 patients with lesions in eloquent areas). The AC group included lesions in close proximity to the eloquent cortex that were surgically treated on an elective basis.
Globally, the 2 groups were comparable in terms of sex, age, American Society of Anesthesiologists score, pathology, size of lesions, quality of resection, duration of surgery, and neurological outcome, and different in tumor location and preoperative neurological deficits (higher in the AC group). However, specific data analysis of patients with lesions in eloquent areas revealed a significantly better neurological outcome and quality of resection (P < .001) in the AC group than the subgroup of GA patients with lesions in eloquent areas. Surgery was uneventful in AC patients and they were discharged home sooner.
AC with brain mapping is safe and allows maximal removal of lesions close to functional areas with low neurological complication rates. It provides an excellent alternative to craniotomy under GA.
Objective
In 1881, Exner first described a “graphic motor image center” in the middle frontal gyrus. Current psycholinguistic models of handwriting involve the conversion of , orthographic ...representations into motor representations before a sequence of appropriate hand movements is produced. Direct cortical stimulation and functional magnetic resonance imaging (fMRI) were used to study the human frontal areas involved in writing.
Methods
Cortical electrical stimulation mapping was used intraoperatively in 12 patients during the removal of brain tumors to identify the areas involved in oral language (sentence reading and naming) and writing, and to spare them during surgery. The fMRI activation experiment involved 12 right‐handed and 12 left‐handed healthy volunteers using word dictation (without visual control) and 2 control tasks.
Results
Direct cortical electrical stimulation of restricted areas rostral to the primary motor hand area (Brodmann area BA 6) impaired handwriting in 6 patients, without disturbing hand movements or oral language tasks. In 6 other patients, stimulation of lower frontal regions showed deficits combining handwriting with other language tasks. fMRI also revealed selective activation during word handwriting in left versus right BA6 depending on handedness. This area was anatomically matched to those areas that affected handwriting on electrical stimulation.
Interpretation
An area in middle frontal gyrus (BA6) that we have termed the graphemic/motor frontal area supports bridging between orthography and motor programs specific to handwriting. Ann Neurol 2009;66:537–545
Abstract
From the 1930s through the early 1960s, Wilder Penfield12 collected a large number of memories induced by electrical brain stimulation (EBS) during awake craniotomy. As a result, he was a ...major contributor to several neuroscientific and neuropsychological concepts of long-term memory. His 1963 paper, which recorded all the cases of memories he induced in his operating room, remains a substantial point of reference in neuroscience in 2019, although some of his interpretations are now debatable.
However, it is highly surprising that, since Penfield's12 reports, there has been no other surgical publication on memories induced during awake surgery. In this review, we explore this phenomenon and analyze some of the reasons that might explain it. We hypothesize that the main reasons for lack of subsequent reports are related to changes in operative procedures (ie, use of anesthetics, time constraints, and insufficient debriefings) and changes in EBS parameters, rather than to the sites that are stimulated, the pathology treated, or the tasks used. If reminiscences are still induced, they should be reported in detail to add valuable contributions to the understanding of long-term memory networks, especially memories that are difficult to reproduce in the laboratory, such as autobiographical memories.
Abstract
OBJECTIVE
Surgical resection of mass lesions in Broca's area is controversial. To demonstrate that pathology may influence the localization of functional areas and language performance, we ...reviewed our experience of awake craniotomies in Broca's area.
METHODS
Sixteen consecutive patients who underwent awake craniotomy and direct brain mapping for resective surgery in Broca's area were analyzed. Six patients had well-circumscribed lesions, whereas 10 patients had infiltrative gliomas. A short version of the Boston Diagnostic Aphasia Examination test was used for language assessment.
RESULTS
Inferior frontal language sites were found in all but 4 patients. In patients with cavernomas or well-circumscribed tumors, 9 of 9 (100%) of the positive sites were located in the classic Broca's area (BA 44/45). By contrast, in those patients with gliomas, only 5 of 20 (25%) of the positive sites were located in BA 44/45. Patients with infiltrative gliomas demonstrated more deficits in the pre and postoperative periods than those with well-circumscribed mass lesions. All patients returned to their baseline abilities within 6 months.
CONCLUSION
Intraoperative language maps generated in cases with well-circumscribed lesions are different from those generated in cases with infiltrative gliomas. This supports the view that interindividual language variability and displacement of critical structures by mass effect should first be considered for circumscribed lesions, whereas reshaping should largely be attributed to brain plasticity in gliomas. Surgery in Broca's area can be safely conducted using awake craniotomy and brain mapping.
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