Temporal lobe regions essential for preserved picture naming after left temporal epilepsy surgery

A Rose by Any Other Name: Mapping Taxonomic and Thematic Naming Errors Poststroke

Understanding the neurobiology of semantic knowledge is a major goal of cognitive neuroscience. Taxonomic and thematic semantic knowledge are represented differently within the brain's conceptual networks, but the specific neural mechanisms remain unclear. Some neurobiological models propose that the anterior temporal lobe is an important hub for taxonomic knowledge, whereas the TPJ is especially involved in the representation of thematic knowledge. However, recent studies have provided divergent evidence. In this context, we investigated the neural correlates of taxonomic and thematic confrontation naming errors in 79 people with aphasia. We used three complementary lesion-symptom mapping (LSM) methods to investigate how structure and function in both spared and impaired brain regions relate to taxonomic and thematic naming errors. Voxel-based LSM mapped brain damage, activation-based LSM mapped BOLD signal in surviving tissue, and network-based LSM mapped white matter subnetwork integrity to error type. Voxel- and network-based lesion symptom mapping provided converging evidence that damage/disruption of the left mid-to-anterior temporal lobe was associated with a greater proportion of thematic naming errors. Activation-based lesion symptom mapping revealed that higher BOLD signal in the left anterior temporal lobe during an in-house naming task was associated with a greater proportion of taxonomic errors on the Philadelphia Naming Test administered outside of the scanner. A lower BOLD signal in the bilateral angular gyrus, precuneus, and right inferior frontal cortex was associated with a greater proportion of taxonomic errors. These findings provide novel evidence that damage to the anterior temporal lobe is especially related to thematic naming errors.

Dissociation of reading and naming in ventral occipitotemporal cortex

Lesions in the language-dominant ventral occipitotemporal cortex (vOTC) can result in selective impairment of either reading or naming, resulting in alexia or anomia. Yet, functional imaging studies that show differential activation for naming and reading do not reveal activity exclusively tuned to one of these inputs. To resolve this dissonance in the functional architecture of the vOTC, we used focused stimulation to the vOTC in 49 adult patients during reading and naming, and generated a population-level, probabilistic map to evaluate if reading and naming are clearly dissociable within individuals. Language mapping (50 Hz, 2829 stimulations) was performed during passage reading (216 positive sites) and visual naming (304 positive sites). Within the vOTC, we isolated sites that selectively disrupted reading (24 sites in 11 patients) or naming (27 sites in 12 patients), and those that disrupted both processes (75 sites in 21 patients). The anteromedial vOTC had a higher probability of producing naming disruption, while posterolateral regions resulted in greater reading-specific disruption. Between them lay a multi-modal region where stimulation disrupted both reading and naming. This work provides a comprehensive view of vOTC organization-the existence of a heteromodal cortex critical to both reading and naming, along with a causally dissociable unimodal naming cortex, and a reading-specific visual word form area in the vOTC. Their distinct roles as associative regions may thus relate to their connectivity within the broader language network that is disrupted by stimulation, more than to highly selective tuning properties. Our work also implies that pre-surgical mapping of both reading and naming is essential for patients requiring vOTC resections, as these functions are not co-localized, and such mapping may prevent the occurrence of unexpected deficits.

Naming fMRI-guided white matter language tract volumes influence naming decline after temporal lobe resection

OBJECTIVE

The aim of this study was to explore the relation of language functional MRI (fMRI)-guided tractography with postsurgical naming decline in people with temporal lobe epilepsy (TLE).

METHODS

Twenty patients with unilateral TLE (9 left) were studied with auditory and picture naming functional MRI tasks. Activation maxima in the left posterobasal temporal lobe were used as seed regions for whole-brain fibre tractography. Clinical naming performance was assessed preoperatively, 4 months, and 12 months following temporal lobe resection. Volumes of white matter language tracts in both hemispheres as well as tract volume laterality indices were explored as moderators of postoperative naming decline using Pearson correlations and multiple linear regression with other clinical variables.

RESULTS

Larger volumes of white matter language tracts derived from auditory and picture naming maxima in the hemisphere of subsequent surgery as well as stronger lateralization of picture naming tract volumes to the side of surgery correlated with greater language decline, which was independent of fMRI lateralization status. Multiple regression for picture naming tract volumes was associated with a significant decline of naming function with 100% sensitivity and 93% specificity at both short-term and long-term follow-up.

INTERPRETATION

Naming fMRI-guided white matter language tract volumes relate to postoperative naming decline after temporal lobe resection in people with TLE. This can assist stratification of surgical outcome and minimize risk of postoperative language deficits in TLE.

Stimulation of caudal inferior and middle frontal gyri disrupts planning during spoken interaction

Turn-taking is a central feature of conversation across languages and cultures.1,2,3,4 This key social behavior requires numerous sensorimotor and cognitive operations1,5,6 that can be organized into three general phases: comprehension of a partner's turn, preparation of a speaker's own turn, and execution of that turn. Using intracranial electrocorticography, we recently demonstrated that neural activity related to these phases is functionally distinct during turn-taking.7 In particular, networks active during the perceptual and articulatory stages of turn-taking consisted of structures known to be important for speech-related sensory and motor processing,8,9,10,11,12,13,14,15,16,17 while putative planning dynamics were most regularly observed in the caudal inferior frontal gyrus (cIFG) and the middle frontal gyrus (cMFG). To test if these structures are necessary for planning during spoken interaction, we used direct electrical stimulation (DES) to transiently perturb cortical function in neurosurgical patient-volunteers performing a question-answer task.7,18,19 We found that stimulating the cIFG and cMFG led to various response errors9,13,20,21 but not gross articulatory deficits, which instead resulted from DES of structures involved in motor control8,13,20,22 (e.g., the precentral gyrus). Furthermore, perturbation of the cIFG and cMFG delayed inter-speaker timing-consistent with slowed planning-while faster responses could result from stimulation of sites located in other areas. Taken together, our findings suggest that the cIFG and cMFG contain critical preparatory circuits that are relevant for interactive language use.

Basal temporal language area revisited in Japanese language with a language function density map

We revisited the anatomo-functional characteristics of the basal temporal language area (BTLA), first described by Lüders et al. (1986), using electrical cortical stimulation (ECS) in the context of Japanese language and semantic networks. We recruited 11 patients with focal epilepsy who underwent chronic subdural electrode implantation and ECS mapping with multiple language tasks for presurgical evaluation. A semiquantitative language function density map delineated the anatomo-functional characteristics of the BTLA (66 electrodes, mean 3.8 cm from the temporal tip). The ECS-induced impairment probability was higher in the following tasks, listed in a descending order: spoken-word picture matching, picture naming, Kanji word reading, paragraph reading, spoken-verbal command, and Kana word reading. The anterior fusiform gyrus (FG), adjacent anterior inferior temporal gyrus (ITG), and the anterior end where FG and ITG fuse, were characterized by stimulation-induced impairment during visual and auditory tasks requiring verbal output or not, whereas the middle FG was characterized mainly by visual input. The parahippocampal gyrus was the least impaired of the three gyri in the basal temporal area. We propose that the BTLA has a functional gradient, with the anterior part involved in amodal semantic processing and the posterior part, especially the middle FG in unimodal semantic processing.

An inclusive multivariate approach to neural localization of language components

To determine how language is implemented in the brain, it is important to know which brain areas are primarily engaged in language processing and which are not. Existing protocols for localizing language are typically univariate, treating each small unit of brain volume as independent. One prominent example that focuses on the overall language network in functional magnetic resonance imaging (fMRI) uses a contrast between neural responses to sentences and sets of pseudowords (pronounceable nonwords). This contrast reliably activates peri-sylvian language areas but is less sensitive to extra-sylvian areas that are also known to support aspects of language such as word meanings (semantics). In this study, we assess areas where a multivariate, pattern-based approach shows high reproducibility across multiple measurements and participants, identifying these areas as multivariate regions of interest (mROI). We then perform a representational similarity analysis (RSA) of an fMRI dataset where participants made familiarity judgments on written words. We also compare those results to univariate regions of interest (uROI) taken from previous sentences > pseudowords contrasts. RSA with word stimuli defined in terms of their semantic distance showed greater correspondence with neural patterns in mROI than uROI. This was confirmed in two independent datasets, one involving single-word recognition, and the other focused on the meaning of noun-noun phrases by contrasting meaningful phrases > pseudowords. In all cases, areas of spatial overlap between mROI and uROI showed the greatest neural association. This suggests that ROIs defined in terms of multivariate reproducibility can help localize components of language such as semantics. The multivariate approach can also be extended to focus on other aspects of language such as phonology, and can be used along with the univariate approach for inclusively mapping language cortex.

Naming assessment in bilinguals for epilepsy surgery-adaptation and standardization of Boston Naming Test in India

PURPOSE

Naming difficulty is associated with temporal lobe epilepsy and a decline in naming ability is reported following dominant temporal lobe resections. The Boston Naming Test (BNT) is the most frequently used test for assessing naming ability. Evaluating naming ability in bilingual/multilingual populations is a challenge when participants are restricted to responding in one language. The study aimed to adapt and standardize the BNT as a valid clinical tool for evaluating bilingual/multilingual people undergoing epilepsy surgery in urban India.

RESULTS

Culture-appropriate adaptations were done, and participants were allowed to respond in any language. Data from 197 participants showed a strong education effect. The adaptation showed strong internal consistency, reliability, construct validity, and high sensitivity to left temporal lobe epilepsy performance.

CONCLUSIONS

The adapted version that allowed for flexible use of more than one language is a useful clinical tool for evaluating bilingual people undergoing epilepsy surgery.

Semantic representations in inferior frontal and lateral temporal cortex during picture naming, reading, and repetition

Reading, naming, and repetition are classical neuropsychological tasks widely used in the clinic and psycholinguistic research. While reading and repetition can be accomplished by following a direct or an indirect route, pictures can be named only by means of semantic mediation. By means of fMRI multivariate pattern analysis, we evaluated whether this well-established fundamental difference at the cognitive level is associated at the brain level with a difference in the degree to which semantic representations are activated during these tasks. Semantic similarity between words was estimated based on a word association model. Twenty subjects participated in an event-related fMRI study where the three tasks were presented in pseudo-random order. Linear discriminant analysis of fMRI patterns identified a set of regions that allow to discriminate between words at a high level of word-specificity across tasks. Representational similarity analysis was used to determine whether semantic similarity was represented in these regions and whether this depended on the task performed. The similarity between neural patterns of the left Brodmann area 45 (BA45) and of the superior portion of the left supramarginal gyrus correlated with the similarity in meaning between entities during picture naming. In both regions, no significant effects were seen for repetition or reading. The semantic similarity effect during picture naming was significantly larger than the similarity effect during the two other tasks. In contrast, several regions including left anterior superior temporal gyrus and left ventral BA44/frontal operculum, among others, coded for semantic similarity in a task-independent manner. These findings provide new evidence for the dynamic, task-dependent nature of semantic representations in the left BA45 and a more task-independent nature of the representational activation in the lateral temporal cortex and ventral BA44/frontal operculum.

Neuropsychological Testing in Autoimmune Encephalitis: A Scoping Review

BACKGROUND AND OBJECTIVES

Identifying optimal methods for evaluation and monitoring of cognitive outcomes in AE is important for clinical care and research. This scoping review aimed to evaluate neuropsychological tests (NPT) that are most frequently impaired in AE cohorts to provide recommendations for a standardized NPT battery for AE outcome.

METHODS

PubMed search for studies examining NPT in patients with AE was conducted on June 9, 2023. Studies were screened for inclusion/exclusion criteria as follows: at least 1 NPT, individual NPT test scores with comparison with healthy controls or normative data and neural-IgG status, total sample size ≥5, and English manuscript available.

RESULTS

The search yielded 5,393 studies, of which 3,359 were screened, 107 were full text reviewed, and 32 met inclusion/exclusion criteria, anti-NMDA-R (k = 18), anti-LGI1 (k = 10), anti-GABAB-R (k = 2), anti-GAD-65 (k = 4), and anti-CASPR2 (k = 3). The cognitive domains most frequently impaired were visual and verbal episodic memory, attention/working memory, processing speed, and aspects of executive functions.

DISCUSSION

Given the dearth of literature examining NPT in AE in combination with small sample sizes and methodological differences, more research in this area is needed. However, we provide recommendations for a test battery to be used in future studies, with the aim of standardizing research in this area. Based on the available literature, we recommend the use of comprehensive NPT batteries, spanning all cognitive domains. The highest yield measures may include the tests of (1) visual and verbal learning/memory, (2) basic and sustained attention, (3) processing speed, and (4) executive functions.

A frontal cortical network is critical for language planning during spoken interaction

Many brain areas exhibit activity correlated with language planning, but the impact of these dynamics on spoken interaction remains unclear. Here we use direct electrical stimulation to transiently perturb cortical function in neurosurgical patient-volunteers performing a question-answer task. Stimulating structures involved in speech motor function evoked diverse articulatory deficits, while perturbations of caudal inferior and middle frontal gyri - which exhibit preparatory activity during conversational turn-taking - led to response errors. Perturbation of the same planning-related frontal regions slowed inter-speaker timing, while faster responses could result from stimulation of sites located in other areas. Taken together, these findings further indicate that caudal inferior and middle frontal gyri constitute a critical planning network essential for interactive language use.

Anterolateral temporal lobe localization of dysnomia after temporal lobe epilepsy surgery

Objectives

To evaluate what factors influence naming ability after temporal lobectomy in patients with drug-resistant epilepsy.

Methods

85 participants with drug-resistant epilepsy who underwent temporal lobe (TL) resective surgery were retrospectively identified (49 left TL and 36 right TL). Naming ability was assessed before and >3 months post-surgery using the Boston Naming Test (BNT).Multivariate lesion-symptom mapping was performed to evaluate whether lesion location related to naming deficits. Multiple regression analyses were conducted to examine if other patient characteristics were significantly associated with pre-to post-surgery changes in naming ability.

Results

Lesion laterality and location were important predictors of post-surgical naming performance. Naming performance significantly improved after right temporal lobectomy ( p = 0.015) while a decrement in performance was observed following left temporal lobectomy ( p = 0.002). Lesion-symptom mapping showed the decline in naming performance was associated with surgical resection of the anterior left middle temporal gyrus (Brodmann area 21, r =0.41, p = <.001). For left hemisphere surgery, later onset of epilepsy was associated with a greater reduction in post-surgical naming performance ( p = 0.01).

Significance

There is a wide range of variability in outcomes for naming ability after temporal lobectomy, from significant improvements to decrements observed. If future studies support the association of left anterior middle temporal gyrus resection and impaired naming this may help in surgical planning and discussions of prognosis.

Age of epilepsy onset as modulating factor for naming deficit after epilepsy surgery: a voxel-based lesion-symptom mapping study

Age at onset of epilepsy is an important predictor of deterioration in naming ability following epilepsy surgery. In 141 patients with left hemispheric epilepsy and language dominance who received epilepsy surgery at the Epilepsy Centre Erlangen, naming of objects (Boston naming test, BNT) was assessed preoperatively and 6 months postoperatively. Surgical lesions were plotted on postoperative MRI and normalized for statistical analysis using voxel-based lesion-symptom mapping (VBLSM). The correlation between lesion and presence of postoperative naming deterioration was examined varying the considered age range of epilepsy onsets. The VBLSM analysis showed that volumes of cortex areas in the left temporal lobe, which were associated with postoperative decline of naming, increased with each year of later epilepsy onset. In patients with later onset, an increasing left posterior temporobasal area was significantly associated with a postoperative deficit when included in the resection. For late epilepsy onset, the temporomesial expansion also included the left hippocampus. The results underline that early onset of epilepsy is a good prognostic factor for unchanged postoperative naming ability following epilepsy surgery. For later age of epilepsy onset, the extent of the area at risk of postoperative naming deficit at 6 months after surgery included an increasing left temporobasal area which finally also comprised the hippocampus.

Interindividual variability and consistency of language mapping paradigms for presurgical use

Most functional MRI studies of language processing have focussed on group-level inference, but for clinical use, the aim is to predict outcomes at an individual patient level. This requires being able to identify atypical activation and understand how differences relate to language outcomes. A language mapping paradigm that selectively activates left hemisphere language regions in healthy individuals allows atypical activation in a patient to be more easily identified. We investigated the interindividual variability and consistency of language activation in 12 healthy participants using three tasks-verb generation, responsive naming, and sentence comprehension-for future presurgical use. Responsive naming produced the most consistent left-lateralised activation across participants in frontal and temporal regions that postsurgical voxel-based lesion-symptom mapping studies suggest are most critical for language outcomes. Studies with a long-term clinical aim of predicting language outcomes in neurosurgical patients and stroke patients should first establish paradigm validity at an individual level in healthy participants.

Functional connectivity explains how neuronavigated TMS of posterior temporal subregions differentially affect language processing

BACKGROUND

"Wernicke's area" is most often used to describe the posterior superior temporal gyrus (STG) and refers to a region traditionally thought to support language comprehension. However, the posterior STG additionally plays a critical role in language production. The purpose of the current study was to determine to what extent regions within the posterior STG are selectively recruited during language production.

METHODS

23 healthy right-handed participants completed an auditory fMRI localizer task, resting-state fMRI and underwent neuronavigated TMS language mapping. We applied repetitive TMS bursts during a picture naming paradigm to probe speech disruptions of different categories (anomia, speech arrest, semantic paraphasia and phonological paraphasia). We combined an in-house built high precision stimulation software suite with E-field modeling to map the naming errors to cortical regions and revealed a dissociation of language functions within the temporal gyrus. Resting state fMRI was used to explain how E-field peaks of different categories differentially affected language production.

RESULTS

Peaks for phonological and semantic errors were found in the STG while those for anomia and speech arrest were located in the MTG. Seed-based connectivity analysis revealed a local connectivity pattern for phonological and semantic errors, while anomia and speech arrest seeds resulted in a larger network between IFG and posterior MTG.

CONCLUSIONS

Our study provides important insights into the functional neuroanatomy of language production and might help to increase the current understanding of specific language production difficulties on a causal level.

The central role of the left inferior longitudinal fasciculus in the face-name retrieval network

Unsuccessful retrieval of proper names (PNs) is commonly observed in patients suffering from neurological conditions such as stroke or epilepsy. While a large body of works has suggested that PN retrieval relies on a cortical network centered on the left anterior temporal lobe (ATL), much less is known about the white matter connections underpinning this process. Sparse studies provided evidence for a possible role of the uncinate fasciculus, but the inferior longitudinal fasciculus (ILF) might also contribute, since it mainly projects into the ATL, interconnects it with the posterior lexical interface and is engaged in common name (CN) retrieval. To ascertain this hypothesis, we assessed 58 patients having undergone a neurosurgery for a left low-grade glioma by means of a famous face naming (FFN) task. The behavioural data were processed following a multilevel lesion approach, including location-based analyses, voxel-based lesion-symptom mapping (VLSM) and disconnection-symptom mapping. Different statistical models were generated to control for sociodemographic data, familiarity, biographical knowledge and control cognitive performances (i.e., semantic and episodic memory and CN retrieval). Overall, VLSM analyses indicated that damage to the mid-to-anterior part of the ventro-basal temporal cortex was especially associated with PN retrieval deficits. As expected, tract-oriented analyses showed that the left ILF was the most strongly associated pathway. Our results provide evidence for the pivotal role of the ILF in the PN retrieval network. This novel finding paves the way for a better understanding of the pathophysiological bases underlying PN retrieval difficulties in the various neurological conditions marked by white matter abnormalities.

Critical role of the ventral temporal lobe in naming

OBJECTIVE

Lexical retrieval deficits are characteristic of a variety of different neurological disorders. However, the exact substrates responsible for this are not known. We studied a large cohort of patients undergoing surgery in the dominant temporal lobe for medically intractable epilepsy (n = 95) to localize brain regions that were associated with anomia.

METHODS

We performed a multivariate voxel-based lesion-symptom mapping analysis to correlate surgical lesions within the temporal lobe with changes in naming ability. Additionally, we used a surface-based mixed-effects multilevel analysis to estimate group-level broadband gamma activity during naming across a subset of patients with electrocorticographic recordings and integrated these results with lesion-deficit findings.

RESULTS

We observed that ventral temporal regions, centered around the middle fusiform gyrus, were significantly associated with a decline in naming. Furthermore, we found that the ventral aspect of temporal lobectomies was linearly correlated to a decline in naming, with a clinically significant decline occurring once the resection extended 6 cm from the anterior tip of the temporal lobe on the ventral surface. On electrocorticography, the majority of these cortical regions were functionally active following visual processing. These loci coincide with the sites of susceptibility artifacts during echoplanar imaging, which may explain why this region has been previously underappreciated as the locus responsible for postoperative naming deficits.

SIGNIFICANCE

Taken together, these data highlight the crucial contribution of the ventral temporal cortex in naming and its important role in the pathophysiology of anomia following temporal lobe resections. As such, surgical strategies should attempt to preserve this region to mitigate postoperative language deficits.

Machine Learning for Precision Epilepsy Surgery

Brain surgery offers the best chance of seizure-freedom for patients with focal drug-resistant epilepsy, but only 50% achieve sustained seizure-freedom. With the explosion of data collected during routine presurgical evaluations and recent advances in computational science, we now have a tremendous potential to achieve precision epilepsy surgery: a data-driven tailoring of surgical planning. This review highlights the clinical need, the relevant computational science focusing on machine learning, and discusses some specific applications in epilepsy surgery.

Concordance of Lateralization Index for Brain Asymmetry Applied to Identify a Reliable Language Task

How can we determine which language task is relevant for examining functional hemispheric asymmetry? A problem in measuring brain asymmetry using functional magnetic resonance imaging lies in the uncertain reliability of the computed index regarding the “true” asymmetry degree. Strictly speaking, the results from the Wada test or direct cortical stimulation cannot be an exact “ground truth”, specifically for the degree of asymmetry. Therefore, we developed a method to evaluate task performance using reproducibility independent of the phenomenon of functional lateralization. Kendall’s coefficient of concordance (W) was used as the statistical measure. The underlying idea was that although various algorithms to compute the lateralization index show considerably different index values for the same data, a superior language task would reproduce similar individual ranking sequences across the algorithms; the high reproducibility of rankings across various index types would indicate a reliable task to investigate functional asymmetry regardless of index computation algorithms. Consequently, we found specificity for brain locations; a verb-generation task demonstrated the highest concordance across index types along with sufficiently high index values in the inferior frontal gyrus, whereas a narration–listening task demonstrated the highest concordance in the posterior temporo-parietal junction area.

Multimodal Triplet Attention Network for Brain Disease Diagnosis

Multi-modal imaging data fusion has attracted much attention in medical data analysis because it can provide complementary information for more accurate analysis. Integrating functional and structural multi-modal imaging data has been increasingly used in the diagnosis of brain diseases, such as epilepsy. Most of the existing methods focus on the feature space fusion of different modalities but ignore the valuable high-order relationships among samples and the discriminative fused features for classification. In this paper, we propose a novel framework by fusing data from two modalities of functional MRI (fMRI) and diffusion tensor imaging (DTI) for epilepsy diagnosis, which effectively captures the complementary information and discriminative features from different modalities by high-order feature extraction with the attention mechanism. Specifically, we propose a triple network to explore the discriminative information from the high-order representation feature space learned from multi-modal data. Meanwhile, self-attention is introduced to adaptively estimate the degree of importance between brain regions, and the cross-attention mechanism is utilized to extract complementary information from fMRI and DTI. Finally, we use the triple loss function to adjust the distance between samples in the common representation space. We evaluate the proposed method on the epilepsy dataset collected from Jinling Hospital, and the experiment results demonstrate that our method is significantly superior to several state-of-the-art diagnosis approaches.

Roles of fMRI and Wada tests in the presurgical evaluation of language functions in temporal lobe epilepsy

Surgical treatment of pharmacoresistant temporal lobe epilepsy (TLE) carries risks for language function that can significantly affect the quality of life. Predicting the risks of decline in language functions before surgery is, consequently, just as important as predicting the chances of becoming seizure-free. The intracarotid amobarbital test, generally known as the Wada test (WT), has been traditionally used to determine language lateralization and to estimate their potential decline after surgery. However, the test is invasive and it does not localize the language functions. Therefore, other noninvasive methods have been proposed, of which functional magnetic resonance (fMRI) has the greatest potential. Functional MRI allows localization of language areas. It has good concordance with the WT for language lateralization, and it is of predictive value for postsurgical naming outcomes. Consequently, fMRI has progressively replaced WT for presurgical language evaluation. The objective of this manuscript is to review the most relevant aspects of language functions in TLE and the current role of fMRI and WT in the presurgical evaluation of language. First, we will provide context by revising the language network distribution and the effects of TLE on them. Then, we will assess the functional outcomes following various forms of TLE surgery and measures to reduce postoperative language decline. Finally, we will discuss the current indications for WT and fMRI and the potential usefulness of the resting-state fMRI technique.

fMRI to Predict Naming Decline: Can We Improve the Grade From a C to an A?

Prediction of Naming Outcome With fMRI Language Lateralization in Left Temporal Epilepsy Surgery

Gross WL, Helfand AI, Swanson SJ, Conant LL, Humphries CJ, Raghavan M, Mueller WM, Busch RM, Allen L, Anderson CT, Carlson CE, Lowe MJ, Langfitt JT, Tivarus ME, Drane DL, Loring DW, Jacobs M, Morgan VL, Allendorfer JB, Szaflarski JP, Bonilha L, Bookheimer S, Grabowski T, Vannest J, Binder JR; FMRI in Anterior Temporal Epilepsy Surgery (FATES) Study. Neurology. 2022;98(23):e2337-e2346. doi:10.1212/WNL.0000000000200552. PMID: 35410903; PMCID: PMC9202528.

Background and Objectives:

Naming decline after left temporal lobe epilepsy (TLE) surgery is common and difficult to predict. Preoperative language fMRI may predict naming decline, but this application is still lacking evidence. We performed a large multicenter cohort study of the effectiveness of fMRI in predicting naming deficits after left TLE surgery.

Methods:

At 10 US epilepsy centers, 81 patients with left TLE were prospectively recruited and given the Boston Naming Test (BNT) before and ≈7 months after anterior temporal lobectomy. An fMRI language laterality index (LI) was measured with an auditory semantic decision-tone decision task contrast. Correlations and a multiple regression model were built with a priori chosen predictors.

Results:

Naming decline occurred in 56% of patients and correlated with fMRI LI (r = −0.41, p < 0.001), age at epilepsy onset (r = −0.30, p = 0.006), age at surgery (r = −0.23, p = 0.039), and years of education (r = 0.24, p = 0.032). Preoperative BNT score and duration of epilepsy were not correlated with naming decline. The regression model explained 31% of the variance, with fMRI contributing 14%, with a 96% sensitivity, and 44% specificity for predicting meaningful naming decline. Cross-validation resulted in an average prediction error of 6 points.

Discussion:

An fMRI-based regression model predicted naming outcome after left TLE surgery in a large, prospective multicenter sample, with fMRI as the strongest predictor. These results provide evidence supporting the use of preoperative language fMRI to predict language outcome in patients undergoing left TLE surgery.

Precision medicine in pediatric temporal epilepsy surgery: optimization of outcomes through functional MRI memory tasks and tailored surgeries

OBJECTIVE

The goal of epilepsy surgery is both seizure cessation and maximal preservation of function. In temporal lobe (TL) cases, the lack of functional MRI (fMRI) tasks that effectively activate mesial temporal structures hampers preoperative memory risk assessment, especially in children. This study evaluated pediatric TL surgery outcome optimization associated with tailored resection informed by an fMRI memory task.

METHODS

The authors identified focal onset TL epilepsy patients with 1) TL resections; 2) viable fMRI memory scans; and 3) pre- and postoperative neuropsychological (NP) evaluations. They retrospectively evaluated preoperative fMRI memory scans, available Wada tests, pre- and postoperative NP scores, postoperative MRI scans, and postoperative Engel class outcomes. To assess fMRI memory task outcome prediction, the authors 1) overlaid preoperative fMRI activation onto postoperative structural images; 2) classified patients as having "overlap" or "no overlap" of activation and resection cavities; and 3) compared these findings with memory improvement, stability, or decline, based on Reliable Change Index calculations.

RESULTS

Twenty patients met the inclusion criteria. At a median of 2.1 postoperative years, 16 patients had Engel class IA outcomes and 1 each had Engel class IB, ID, IIA, and IID outcomes. Functional MRI activation was linked to NP memory outcome in 19 of 20 cases (95%). Otherwise, heterogeneity characterized the cohort.

CONCLUSIONS

Functional MRI memory task activation effectively predicted individual NP outcomes in the context of tailored TL resections. Patients had excellent seizure and overall good NP outcomes. This small study adds to extant literature indicating that pediatric TL epilepsy does not represent a single clinical syndrome. Findings support individualized surgical intervention using fMRI memory activation to help guide this precision medicine approach.

A Spatiotemporal Map of Reading Aloud

Reading words aloud is a fundamental aspect of literacy. The rapid rate at which multiple distributed neural substrates are engaged in this process can only be probed via techniques with high spatiotemporal resolution. We probed this with direct intracranial recordings covering most of the left hemisphere in 46 humans (26 male, 20 female) as they read aloud regular, exception and pseudo-words. We used this to create a spatiotemporal map of word processing and to derive how broadband γ activity varies with multiple word attributes critical to reading speed: lexicality, word frequency, and orthographic neighborhood. We found that lexicality is encoded earliest in mid-fusiform (mFus) cortex, and precentral sulcus, and is represented reliably enough to allow single-trial lexicality decoding. Word frequency is first represented in mFus and later in the inferior frontal gyrus (IFG) and inferior parietal sulcus (IPS), while orthographic neighborhood sensitivity resides solely in IPS. We thus isolate the neural correlates of the distributed reading network involving mFus, IFG, IPS, precentral sulcus, and motor cortex and provide direct evidence for parallel processes via the lexical route from mFus to IFG, and the sublexical route from IPS and precentral sulcus to anterior IFG.SIGNIFICANCE STATEMENT Reading aloud depends on multiple complex cerebral computations: mapping from a written letter string on a page to a sequence of spoken sound representations. Here, we used direct intracranial recordings in a large cohort while they read aloud known and novel words, to track, across space and time, the progression of neural representations of behaviorally relevant factors that govern reading speed. We find, concordant with cognitive models of reading, that known and novel words are differentially processed through a lexical route, sensitive to frequency of occurrence of known words in natural language, and a sublexical route, performing letter-by-letter construction of novel words.

Prediction of Naming Outcome With fMRI Language Lateralization in Left Temporal Epilepsy Surgery

BACKGROUND AND OBJECTIVES

Naming decline after left temporal lobe epilepsy (TLE) surgery is common and difficult to predict. Preoperative language fMRI may predict naming decline, but this application is still lacking evidence. We performed a large multicenter cohort study of the effectiveness of fMRI in predicting naming deficits after left TLE surgery.

METHODS

At 10 US epilepsy centers, 81 patients with left TLE were prospectively recruited and given the Boston Naming Test (BNT) before and ≈7 months after anterior temporal lobectomy. An fMRI language laterality index (LI) was measured with an auditory semantic decision-tone decision task contrast. Correlations and a multiple regression model were built with a priori chosen predictors.

RESULTS

Naming decline occurred in 56% of patients and correlated with fMRI LI (r = -0.41, p < 0.001), age at epilepsy onset (r = -0.30, p = 0.006), age at surgery (r = -0.23, p = 0.039), and years of education (r = 0.24, p = 0.032). Preoperative BNT score and duration of epilepsy were not correlated with naming decline. The regression model explained 31% of the variance, with fMRI contributing 14%, with a 96% sensitivity and 44% specificity for predicting meaningful naming decline. Cross-validation resulted in an average prediction error of 6 points.

DISCUSSION

An fMRI-based regression model predicted naming outcome after left TLE surgery in a large, prospective multicenter sample, with fMRI as the strongest predictor. These results provide evidence supporting the use of preoperative language fMRI to predict language outcome in patients undergoing left TLE surgery.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that fMRI language lateralization can help in predicting naming decline after left TLE surgery.

Standardization of presurgical language fMRI in Greek population: Mapping of six critical regions

BACKGROUND

Mapping the language system has been crucial in presurgical evaluation especially when the area to be resected is near relevant eloquent cortex. Functional magnetic resonance imaging (fMRI) proved to be a noninvasive alternative of Wada test that can account not only for language lateralization but also for localization when appropriate tasks and MRI sequences are being used. The tasks utilized during the fMRI acquisition are playing a crucial role as to which areas will be activated. Recent studies demonstrated that key language regions exist outside the classical model of "Wernicke-Lichtheim-Geschwind," but sensitive tasks must take place in order to be revealed. On top of that, the tasks should be in mother tongue for appropriate language mapping to be possible.

METHODS

For that reason, in this study, we adopted an English protocol that can reveal six language critical regions even in clinical setups and we translated it into Greek to prove its efficacy in Greek population. Twenty healthy right-handed volunteers were recruited and performed the fMRI acquisition in a standardized manner.

RESULTS

Results demonstrated that all six language critical regions were activated in all subjects as well as the group mean map. Furthermore, activations were found in the thalamus, the caudate, and the contralateral cerebellum.

CONCLUSION

In this study, we standardized an fMRI protocol in Greek and proved that it can reliably activate six language critical regions. We have validated its efficacy for presurgical language mapping in Greek patients capable to be adopted in clinical setup.

Structure and function of language networks in temporal lobe epilepsy

Individuals with temporal lobe epilepsy (TLE) may have significant language deficits. Language capabilities may further decline following temporal lobe resections. The language network, comprising dispersed gray matter regions interconnected with white matter fibers, may be atypical in individuals with TLE. This review explores the structural changes to the language network and the functional reorganization of language abilities in TLE. We discuss the importance of detailed reporting of patient's characteristics, such as, left- and right-sided focal epilepsies as well as lesional and nonlesional pathological subtypes. These factors can affect the healthy functioning of gray and/or white matter. Dysfunction of white matter and displacement of gray matter function could concurrently impact their ability, in turn, producing an interactive effect on typical language organization and function. Surgical intervention can result in impairment of function if the resection includes parts of this structure-function network that are critical to language. In addition, impairment may occur if language function has been reorganized and is included in a resection. Conversely, resection of an epileptogenic zone may be associated with recovery of cortical function and thus improvement in language function. We explore the abnormality of functional regions in a clinically applicable framework and highlight the differences in the underlying language network. Avoidance of language decline following surgical intervention may depend on tailored resections to avoid critical areas of gray matter and their white matter connections. Further work is required to elucidate the plasticity of the language network in TLE and to identify sub-types of language representation, both of which will be useful in planning surgery to spare language function.

Intraoperative localization and preservation of reading in ventral occipitotemporal cortex

OBJECTIVE

Resective surgery in language-dominant ventral occipitotemporal cortex (vOTC) carries the risk of causing impairment to reading. Because it is not on the lateral surface, it is not easily accessible for intraoperative mapping, and extensive stimulation mapping can be time-consuming. Here the authors assess the feasibility of using task-based electrocorticography (ECoG) recordings intraoperatively to help guide stimulation mapping of reading in vOTC.

METHODS

In 11 patients undergoing extraoperative, intracranial seizure mapping, the authors recorded induced broadband gamma activation (70-150 Hz) during a visual category localizer. In 2 additional patients, whose pathologies necessitated resections in language-dominant vOTC, task-based functional mapping was performed intraoperatively using subdural ECoG alongside direct cortical stimulation.

RESULTS

Word-responsive cortex localized using ECoG showed a high sensitivity (72%) to stimulation-induced reading deficits, and the confluence of ECoG and stimulation-positive sites appears to demarcate the visual word form area. Intraoperative task-based ECoG mapping was possible in < 3 minutes, providing a high signal quality, and initial intraoperative data analysis took < 3 minutes, allowing for rapid assessment of broad areas of cortex. Cortical areas critical for reading were mapped and successfully preserved, while also enabling pathological tissue to be completely removed.

CONCLUSIONS

Eloquent cortex in ventral visual cortex can be rapidly mapped intraoperatively using ECoG. This method acts to guide high-probability targets for stimulation with limited patient participation and can be used to avoid iatrogenic dyslexia following surgery.

Controversy over the temporal cortical terminations of the left arcuate fasciculus: a reappraisal

The arcuate fasciculus has been considered a major dorsal fronto-temporal white matter pathway linking frontal language production regions with auditory perception in the superior temporal gyrus, the so-called Wernicke's area. In line with this tradition, both historical and contemporary models of language function have assigned primacy to superior temporal projections of the arcuate fasciculus. However, classical anatomical descriptions and emerging behavioural data are at odds with this assumption. On one hand, fronto-temporal projections to Wernicke's area may not be unique to the arcuate fasciculus. On the other hand, dorsal stream language deficits have been reported also for damage to middle, inferior and basal temporal gyri which may be linked to arcuate disconnection. These findings point to a reappraisal of arcuate projections in the temporal lobe. Here, we review anatomical and functional evidence regarding the temporal cortical terminations of the left arcuate fasciculus by incorporating dissection and tractography findings with stimulation data using cortico-cortical evoked potentials and direct electrical stimulation mapping in awake patients. Firstly, we discuss the fibers of the arcuate fasciculus projecting to the superior temporal gyrus and the functional rostro-caudal gradient in this region where both phonological encoding and auditory-motor transformation may be performed. Caudal regions within the temporoparietal junction may be involved in articulation and associated with temporoparietal projections of the third branch of the superior longitudinal fasciculus, while more rostral regions may support encoding of acoustic phonetic features, supported by arcuate fibres. We then move to examine clinical data showing that multimodal phonological encoding is facilitated by projections of the arcuate fasciculus to superior, but also middle, inferior and basal temporal regions. Hence, we discuss how projections of the arcuate fasciculus may contribute to acoustic (middle-posterior superior and middle temporal gyri), visual (posterior inferior temporal/fusiform gyri comprising the visual word form area) and lexical (anterior-middle inferior temporal/fusiform gyri in the basal temporal language area) information in the temporal lobe to be processed, encoded and translated into a dorsal phonological route to the frontal lobe. Finally, we point out surgical implications for this model in terms of the prediction and avoidance of neurological deficit.

The importance of basal-temporal white matter to pre- and post-surgical naming ability in temporal lobe epilepsy

OBJECTIVE

Emerging research highlights the importance of basal-temporal cortex, centered on the fusiform gyrus, to both pre-surgical naming ability and post-surgical naming outcomes in temporal lobe epilepsy (TLE). In this study, we investigate whether integrity of the white matter network that interconnects this basal region to the distributed language network affects naming ability and risk for post-surgical naming decline.

METHODS

Patients with drug-resistant TLE were recruited from two epilepsy centers in a prospective longitudinal study. The pre-surgical dataset included 50 healthy controls, 47 left TLE (L-TLE), and 41 right TLE (R-TLE) patients. All participants completed pre-surgical T1- and diffusion-weighted MRI (dMRI), as well as neuropsychological tests of auditory and visual naming. Nineteen L-TLE and 18 R-TLE patients underwent anterior temporal lobectomy (ATL) and also completed post-surgical neuropsychological testing. Pre-surgical fractional anisotropy (FA) of the white matter directly beneath the fusiform neocortex (i.e., superficial white matter; SWM) and of deep white matter tracts with connections to the basal-temporal cortex [inferior longitudinal fasciculus (ILF) and inferior frontal occipital fasciculus (IFOF)] was calculated. Clinical variables, hippocampal volume, and FA of each white matter tract or region were examined in linear regressions with naming scores, or change in naming scores, as the primary outcomes.

RESULTS

Pre-surgically, higher FA in the bilateral ILF, bilateral IFOF, and left fusiform SWM was associated with better visual and auditory naming scores (all ps < 0.05 with FDR correction). In L-TLE, higher pre-surgical FA was also associated with less naming decline post-surgically, but results varied across tracts. When including only patients with typical language dominance, only integrity of the right fusiform SWM was associated with less visual naming decline (p = .0018).

DISCUSSION

Although a broad network of white matter network matter may contribute to naming ability pre-surgically, the reserve capacity of the contralateral (right) fusiform SWM may be important for mitigating visual naming decline following ATL in L-TLE. This shows that the study of the structural network interconnecting the basal-temporal region to the wider language network has implications for understanding both pre- and post-surgical naming in TLE.

Resection of dominant fusiform gyrus is associated with decline of naming function when temporal lobe epilepsy manifests after the age of five: A voxel-based lesion-symptom mapping study

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Resection in the dominant fusiform gyrus is associated with an increased risk of postoperative decline in picture naming.

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More temporo-posterior resections in this area results in a greater degree of naming decline.

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Risk of significant naming decline after left temporal surgery increased by 5% with every year of later seizure onset.

Objective

To determine patients’ characteristics and regions in the temporal lobe where resections lead to a decline in picture naming.

Methods

311 patients with left hemispheric dominance for language were included who underwent epilepsy surgery at the Epilepsy Center of Erlangen and whose picture naming scores (Boston Naming Test, BNT) were available preoperatively and 6-months postoperatively. Surgical lesions were mapped to an averaged template based on preoperative and postoperative MRI using voxel-based lesion-symptom mapping (VBLSM). Postoperative brain shifts were corrected. The relationship between lesioned brain areas and the presence of a postoperative naming decline was examined voxel-wise while controlling for effects of overall lesion size at first in the total cohort and then restricted to temporal lobe resections.

Results

In VBLSM in the total sample, a decline in BNT score was significantly related to left temporal surgery. When only considering patients with left temporal lobe resections (n = 121), 40 (33.1%) significantly worsened in BNT postoperatively. VBLSM including all patients with left temporal resections generated no significant results within the temporal lobe. However, naming decline of patients with epilepsy onset after 5 years of age was significantly associated with resections in the left inferior temporal (extent of BNT decline range: 10.8− 14.4%) and fusiform gyrus (decline range: 12.1−18.4%).

Significance

Resections in the posterior part of the dominant fusiform and inferior temporal gyrus was associated with a risk of deterioration in naming performance at six months after surgery in patients with epilepsy onset after 5 years of age but not with earlier epilepsy onset.

Functional Approaches to the Surgery of Brain Gliomas

In the surgery of gliomas, recent years have witnessed unprecedented theoretical and technical development, which extensively increased indication to surgery. On one hand, it has been solidly demonstrated the impact of gross total resection on life expectancy. On the other hand, the paradigm shift from classical cortical localization of brain function towards connectomics caused by the resurgence of awake surgery and the advent of tractography has permitted safer surgeries focused on subcortical white matter tracts preservation and allowed for surgical resections within regions, such as Broca's area or the primary motor cortex, which were previously deemed inoperable. Furthermore, new asleep electrophysiological techniques have been developed whenever awake surgery is not an option, such as operating in situations of poor compliance (including paediatric patients) or pre-existing neurological deficits. One such strategy is the use of intraoperative neurophysiological monitoring (IONM), enabling the identification and preservation of functionally defined, but anatomically ambiguous, cortico-subcortical structures through mapping and monitoring techniques. These advances tie in with novel challenges, specifically risk prediction and the impact of neuroplasticity, the indication for tumour resection beyond visible borders, or supratotal resection, and most of all, a reappraisal of the importance of the right hemisphere from early psychosurgery to mapping and preservation of social behaviour, executive control, and decision making.Here we review current advances and future perspectives in a functional approach to glioma surgery.

Decreased gray matter volume and increased white matter volume in patients with neovascular age-related macular degeneration: a voxel-based morphometry study

OBJECTIVE

To measure white and gray matter volume (WMV, GMV) in patients with neovascular age-related macular degeneration (nAMD) using voxel-based morphometry (VBM).

MATERIAL

Eighteen patients (9 men, 9 women) with nAMD and 18 (9 men, 9 women) healthy controls (HCs) aligned were recruited. Functional magnetic resonance imaging (fMRI) and VBM of three-dimensional T1 brain images were analyzed. And we also apply t-tests to look for GMV and WMV differences between groups. Correlation analysis was utilized to probe the connection between observational GMV and WMV values of diverse brain areas and the severity of HADS (hospital anxiety and depression scale). Also, distinctions between nAMD and HCs in GMV can be presented with the help of a ROC (receiver operating characteristic) curve.

RESULTS

Compared with HCs, GMV values were significantly lower in patients with neovascular age-related macular degeneration in the right inferior frontal gyrus, temporal pole of left superior temporal gyrus, left superior temporal gyrus, left middle frontal gyrus, left anterior cingulate and para cingulate gyrus. While WMV was slightly increased in these areas. HADS (hospital anxiety and depression scale) scores portrayed a non-linear correlation with the GMV value of the right inferior frontal gyrus, left middle frontal gyrus, left anterior cingulate and paracingulate gyrus of the nAMD group (r=-0.6629, P=0.0027)(r=-0.9451, P<0.0001)(r=-0.6183, P=0.0062). Moreover, the ROC curve analysis of the mean VBM values for altered brain regions indicated high diagnostic accuracy.

CONCLUSION

These results indicated that patients with nAMD have abnormal GMV and WMV and formed a basis for future research on pathological mechanisms in this disease. Moreover, decreased gray matter volume in particular brain regions might be associated with choroidal neovascularization and abnormal HADS score. It might help to explain the pathological mechanism of anxiety and depression in patients with nAMD.

A Heteromodal Word-Meaning Binding Site in the Visual Word Form Area under Top-Down Frontoparietal Control

The integral capacity of human language together with semantic memory drives the linkage of words and their meaning, which theoretically is subject to cognitive control. However, it remains unknown whether, across different language modalities and input/output formats, there is a shared system in the human brain for word-meaning binding and how this system interacts with cognitive control. Here, we conducted a functional magnetic resonance imaging experiment based on a large cohort of subjects (50 females, 50 males) to comprehensively measure the brain responses evoked by semantic processing in spoken and written word comprehension and production tasks (listening, speaking, reading, and writing). We found that heteromodal word input and output tasks involved distributed brain regions within a frontal-parietal-temporal network and focally coactivated the anterior lateral visual word form area (VWFA), which is located in the basal occipitotemporal area. Directed connectivity analysis revealed that the VWFA was invariably under significant top-down modulation of the frontoparietal control network and interacts with regions related to attention and semantic representation. This study reveals that the VWFA is a key site subserving general semantic processes linking words and meaning, challenging the predominant emphasis on this area's specific role in reading or more general visual processes. Our findings also suggest that the dynamics between semantic memory and cognitive control mechanisms during word processing are largely independent of the modalities of input or output.SIGNIFICANCE STATEMENT Binding words and their meaning into a coherent whole during retrieval requires accessing semantic memory and cognitive control, allowing our thoughts to be expressed and comprehended through mind-external tokens in multiple modalities, such as written or spoken forms. However, it is still unknown whether multimodal language comprehension and production share a common word-meaning binding system in human brains and how this system is connected to a cognitive control mechanism. By systematically measuring brain activity evoked by spoken and written verbal input and output tasks tagging word-meaning binding processes, we demonstrate a general word-meaning binding site within the visual word form area (VWFA) and how this site is modulated by the frontal-parietal control network.

Cognitive and Emotional Mapping With SEEG

Mapping of cortical functions is critical for the best clinical care of patients undergoing epilepsy and tumor surgery, but also to better understand human brain function and connectivity. The purpose of this review is to explore existing and potential means of mapping higher cortical functions, including stimulation mapping, passive mapping, and connectivity analyses. We examine the history of mapping, differences between subdural and stereoelectroencephalographic approaches, and some risks and safety aspects, before examining different types of functional mapping. Much of this review explores the prospects for new mapping approaches to better understand other components of language, memory, spatial skills, executive, and socio-emotional functions. We also touch on brain-machine interfaces, philosophical aspects of aligning tasks to brain circuits, and the study of consciousness. We end by discussing multi-modal testing and virtual reality approaches to mapping higher cortical functions.

Chasing language through the brain: Successive parallel networks

OBJECTIVE

To describe the spatio-temporal dynamics and interactions during linguistic and memory tasks.

METHODS

Event-related electrocorticographic (ECoG) spectral patterns obtained during cognitive tasks from 26 epilepsy patients (aged: 9-60 y) were analyzed in order to examine the spatio-temporal patterns of activation of cortical language areas. ECoGs (1024 Hz/channel) were recorded from 1567 subdural electrodes and 510 depth electrodes chronically implanted over or within the frontal, parietal, occipital and/or temporal lobes as part of their surgical work-up for intractable seizures. Six language/memory tasks were performed, which required responding verbally to auditory or visual word stimuli. Detailed analysis of electrode locations allowed combining results across patients.

RESULTS

Transient increases in induced ECoG gamma power (70-100 Hz) were observed in response to hearing words (central superior temporal gyrus), reading text and naming pictures (occipital and fusiform cortex) and speaking (pre-central, post-central and sub-central cortex).

CONCLUSIONS

Between these activations there was widespread spatial divergence followed by convergence of gamma activity that reliably identified cortical areas associated with task-specific processes.

SIGNIFICANCE

The combined dataset supports the concept of functionally-specific locally parallel language networks that are widely distributed, partially interacting in succession to serve the cognitive and behavioral demands of the tasks.