Object Naming Task Research Articles

Cortical time course of object naming investigated by repetitive navigated transcranial magnetic stimulation.

Human language organization models and language time course patterns are still predominantly derived from meta-analyses of numerous single publications, which only investigated scattered cortical regions. Moreover, there is not much literature available on the exact impact of repetitive navigated transcranial magnetic stimulation (rTMS) onset times on object naming. We, therefore, used a virtual lesion-based approach by mapping various cortical areas with rTMS to investigate the time course of object naming, and to specifically provide data on the pattern of rTMS language mapping results depending on different stimulation onset times. Ten healthy, right-handed subjects were enrolled, and rTMS in combination with an object-naming task was performed with different stimulation onset times (0ms, 100ms, 200ms, 300ms, 400ms, and 500ms). Subsequent to language mapping, all naming errors detected were systematically classified with respect to previous literature. The majority of errors was elicited within the opercular inferior frontal gyrus (opIFG) and ventral precentral gyrus (vPrG), and the spatial distribution of naming errors changed according to the time point of naming disruption by varying onset times. For instance, immediate rTMS onset led to a widespread cortical distribution of no responses, whereas performance and hesitation errors increased with higher stimulation onset times.

Visual naming deficits in dyslexia: An ERP investigation of different processing domains

Naming speed deficits are well documented in developmental dyslexia, expressed by slower naming times and more errors in response to familiar items. Here we used event-related potentials (ERPs) to examine at what processing level the deficits in dyslexia emerge during a discrete-naming task. Dyslexic and skilled adult control readers performed a primed object-naming task, in which the relationship between the prime and the target was manipulated along perceptual, semantic and phonological dimensions. A 3×2 design that crossed Relationship Type (Visual, Phonemic Onset, and Semantic) with Relatedness (Related and Unrelated) was used. An attenuated N/P190 – indexing early visual processing – and N300 – which index late visual processing – was observed to pictures preceded by perceptually related (vs. unrelated) primes in the control but not in the dyslexic group. These findings suggest suboptimal processing in early stages of object processing in dyslexia, when integration and mapping of perceptual information to a more form-specific percept in memory take place. On the other hand, both groups showed an N400 effect associated with semantically related pictures (vs. unrelated), taken to reflect intact integration of semantic similarities in both dyslexic and control readers. We also found an electrophysiological effect of phonological priming in the N400 range – that is, an attenuated N400 to objects preceded by phonemic related primes vs. unrelated – while it showed a more widespread distributed and more pronounced over the right hemisphere in the dyslexics. Topographic differences between groups might have originated from a word form encoding process with different characteristics in dyslexics compared to control readers.

Neurophysiologic markers of primary motor cortex for laryngeal muscles and premotor cortex in caudal opercular part of inferior frontal gyrus investigated in motor speech disorder: a navigated transcranial magnetic stimulation (TMS) study.

Transcranial magnetic stimulation studies have so far reported the results of mapping the primary motor cortex (M1) for hand and tongue muscles in stuttering disorder. This study was designed to evaluate the feasibility of repetitive navigated transcranial magnetic stimulation (rTMS) for locating the M1 for laryngeal muscle and premotor cortical area in the caudal opercular part of inferior frontal gyrus, corresponding to Broca's area in stuttering subjects by applying new methodology for mapping these motor speech areas. Sixteen stuttering and eleven control subjects underwent rTMS motor speech mapping using modified patterned rTMS. The subjects performed visual object naming task during rTMS applied to the (a) left M1 for laryngeal muscles for recording corticobulbar motor-evoked potentials (CoMEP) from cricothyroid muscle and (b) left premotor cortical area in the caudal opercular part of inferior frontal gyrus while recording long latency responses (LLR) from cricothyroid muscle. The latency of CoMEP in control subjects was 11.75±2.07ms and CoMEP amplitude was 294.47±208.87µV, and in stuttering subjects CoMEP latency was 12.13±0.75ms and 504.64±487.93µV CoMEP amplitude. The latency of LLR in control subjects was 52.8±8.6ms and 54.95±4.86 in stuttering subjects. No significant differences were found in CoMEP latency, CoMEP amplitude, and LLR latency between stuttering and control-fluent speakers. These results indicate there are probably no differences in stuttering compared to controls in functional anatomy of the pathway used for transmission of information from premotor cortex to the M1 cortices for laryngeal muscle representation and from there via corticobulbar tract to laryngeal muscles.

High-resolution MEG source imaging approach to accurately localize Broca's area in patients with brain tumor or epilepsy.

Localizing expressive language function has been challenging using the conventional magnetoencephalography (MEG) source modeling methods. The present MEG study presents a new accurate and precise approach in localizing the language areas using a high-resolution MEG source imaging method. In 32 patients with brain tumors and/or epilepsies, an object-naming task was used to evoke MEG responses. Our Fast-VESTAL source imaging method was then applied to the MEG data in order to localize the brain areas evoked by the object-naming task. The Fast-VESTAL results showed that Broca's area was accurately localized to the pars opercularis (BA 44) and/or the pars triangularis (BA 45) in all patients. Fast-VESTAL also accurately localized Wernicke's area to the posterior aspect of the superior temporal gyri in BA 22, as well as several additional brain areas. Furthermore, we found that the latency of the main peak of the response in Wernicke's area was significantly earlier than that of Broca's area. In all patients, Fast-VESTAL analysis established accurate and precise localizations of Broca's area, as well as other language areas. The responses in Wernicke's area were also shown to significantly precede those of Broca's area. The present study demonstrates that using Fast-VESTAL, MEG can serve as an accurate and reliable functional imaging tool for presurgical mapping of language functions in patients with brain tumors and/or epilepsies.

Language function distribution in left-handers: A navigated transcranial magnetic stimulation study

Recent studies suggest that in left-handers, the right hemisphere (RH) is more involved in language function when compared to right-handed subjects. Since data on lesion-based approaches is lacking, we aimed to investigate language distribution of left-handers by repetitive navigated transcranial magnetic stimulation (rTMS). Thus, rTMS was applied to the left hemisphere (LH) and RH in 15 healthy left-handers during an object-naming task, and resulting naming errors were categorized. Then, we calculated error rates (ERs=number of errors per number of stimulations) for both hemispheres separately and defined a laterality score as the quotient of the LH ER – RH ER through the LH ER + RH ER (abbreviated as (L−R)/(L+R)). In this context, (L−R)/(L+R)>0 indicates that the LH is dominant, whereas (L−R)/(L+R)<0 shows that the RH is dominant.No significant difference in ERs was found between hemispheres (all errors: mean LH 18.0±11.7%, mean RH 18.1±12.2%, p=0.94; all errors without hesitation: mean LH 12.4±9.8%, mean RH 12.9±10.0%, p=0.65; no responses: mean LH 9.3±9.2%, mean RH 11.5±10.3%, p=0.84). However, a significant difference between the results of (L−R)/(L+R) of left-handers and right-handers (source data of another study) for all errors (mean 0.01±0.14 vs. 0.19±0.20, p=0.0019) and all errors without hesitation (mean −0.02±0.20 vs. 0.19±0.28, p=0.0051) was revealed, whereas the comparison for no responses did not show a significant difference (mean: −0.004±0.27 vs. 0.09±0.44, p=0.64). Accordingly, left-handers present a comparatively equal language distribution across both hemispheres with language dominance being nearly equally distributed between hemispheres in contrast to right-handers.

P63. Cortical time course of object naming investigated by repetitive navigated transcranial magnetic stimulation

Objective Various studies already explored cortical language function. However, language organization models and time course patterns are still derived from meta-analyses of numerous single publications, which only investigated scattered cortical regions. Yet, there is no systematic investigation on the distinct role and time course of the perisylvian cortex in language processing. Methods Ten right-handed volunteers (7 females & 3 males, mean age 27.2 ± 2.3 years) underwent rTMS language mapping of 12 predefined, left-hemispheric cortical regions known to be involved in language function. During investigation of each subject, rTMS pulses were applied with different picture-to-trigger intervals (PTIs) (0 ms, 100 ms, 200 ms, 300 ms, 400 ms, and 500 ms) in combination with an object naming task. Naming errors elicited by rTMS were categorized into six different error types (no-response error, performance error, hesitation, neologism, semantic error, and phonological error), and error rates (= number of errors/number of stimulations) and ratios (= number of errors of one category/total number of errors) for each category were calculated. Then, a predominant error type was defined, which represents the category with the highest error ratio per cortical region. Results The distribution of rTMS-induced naming errors changed according to the time point of naming disruption by varying PTIs: Immediate rTMS onset (PTI = 0 ms) led to a widespread cortical distribution of no responses, whereas performance and hesitation errors increased with PTIs, reaching their peak at 400 ms (performance errors) and 300 ms (hesitations). Conclusion In general, we were able to provide a time course of language processing by rTMS. Furthermore, the present study showed that the occurrence of different naming errors is significantly linked to the onset time of rTMS, and the time points of language subfunctions could be demonstrated.

P72. Impairment of non-invasive language mapping by lesion location a fMRI, rTMS, and DCS study

Objective Language mapping by repetitive navigated transcranial magnetic stimulation (rTMS) is in-creasingly used and already replaces functional magnetic resonance imaging (fMRI) in some institutions for preoperative mapping of neurosurgical patients. However, some factors affect the concordance of both methods with the gold standard direct cortical stimulation (DCS). We therefore analyze the impairment of rTMS and fMRI by intraparenchymal lesions as compared to the results of DCS during awake surgery. Methods We performed language mapping in 27 patients with left-sided perisylvian lesions by DCS, rTMS, and fMRI using an object-naming task, and assigned the obtained language eloquent sites of each method to Corina’s cortical parcellation system (CPS). Subsequently, we calculated the receiver operating characteristics for rTMS and fMRI compared to DCS, and analyzed different subgroups with (W) and with-out (WO) lesion in the mapped areas. Results Within the W subgroup we revealed an overall sensitivity of 100% (WO: 100%), a specificity of 8% (WO: 5%), a PPV of 34% (WO: 53%), and a NPV of 100% (WO: 100%) for the comparison of rTMS with DCS. For the comparison of fMRI with DCS within the W subgroup we obtained an overall sensitivity of 32% (WO: 62%), a specificity of 88% (WO: 60%), a PPV of 56% (WO: 62%), and a NPV of 73% (WO: 60%). Conclusion With this study we were able to show that rTMS is less affected by a brain lesion than fMRI, particularly when performing mapping of language-negative cortical regions based on sensitivity and NPV. With this in mind, rTMS could be useful for the language mapping assessment prior to the gold standard DCS.

Electrical stimulation mapping of nouns and verbs in Broca’s area

Electric stimulation mapping (ESM) is frequently used during brain surgery to localise higher cognitive functions to avoid post-chirurgical disabilities. Experiments with brain imaging techniques and neuropsychological studies showed differences in the cortical representation and processing of nouns and verbs. The goal of the present study was to investigate whether electric stimulation in specific sites in the frontal cortex disrupted noun and verb production selectively. We found that most of the stimulated areas showed disruption of both verbs and nouns at the inferior frontal gyrus. However, when selective effects were obtained, verbs were more prone to disruption than nouns with important individual differences. The overall results indicate that selective impairments can be observed at inferior and middle frontal regions and the action naming task seems to be more suitable to avoid post-chirurgical language disabilities, as it shows a greater sensitivity to disruption with ESM than the classical object naming task.

Cortical distribution of speech and language errors investigated by visual object naming and navigated transcranial magnetic stimulation.

Navigated transcranial magnetic stimulation (nTMS) gains increasing importance in presurgical language mapping. Although bipolar direct cortical stimulation (DCS) is regarded as the gold standard for intraoperative mapping of language-related areas, it cannot be used to map the healthy human brain due to its invasive character. Therefore, the present study employed a non-invasive virtual-lesion modality to provide a causality-confirmed cortical language map of the healthy human brain by repetitive nTMS (rTMS) with functional specifications beyond language-positive/language-negative distinction. Fifty right-handed healthy volunteers underwent rTMS language mapping of the left hemisphere combined with an object-naming task. The induced errors were categorized and frequency maps were calculated. Moreover, a principal component analysis (PCA) was performed on the basis of language-positive cortical regions for each error category. The left hemisphere was stimulated at 258-789 sites (median: 361.5 sites), and 12-241 naming errors (median: 72.5 errors) were observed. In male subjects, a total number of 2091 language errors were elicited by 9579 stimulation trains, which is equal to an error rate of 21.8%. Within females, 10,238 stimulation trains elicited 2032 language errors (19.8%). PCA revealed that the inferior parietal lobe (IPL) and middle frontal gyrus (MFG) were causally involved in object naming as a semantic center and an executive control center. For the first time, this study provides causality-based data and a model that approximates the distribution of language-related cortical areas grouped for different functional aspects of single-word production processes by PCA.

Impairment of preoperative language mapping by lesion location: a functional magnetic resonance imaging, navigated transcranial magnetic stimulation, and direct cortical stimulation study.

Language mapping by repetitive navigated transcranial magnetic stimulation (rTMS) is increasingly used and has already replaced functional MRI (fMRI) in some institutions for preoperative mapping of neurosurgical patients. Yet some factors affect the concordance of both methods with direct cortical stimulation (DCS), most likely by lesions affecting cortical oxygenation levels. Therefore, the impairment of the accuracy of rTMS and fMRI was analyzed and compared with DCS during awake surgery in patients with intraparenchymal lesions. Language mapping was performed by DCS, rTMS, and fMRI using an object-naming task in 27 patients with left-sided perisylvian lesions, and the induced language errors of each method were assigned to the cortical parcellation system. Subsequently, the receiver operating characteristics were calculated for rTMS and fMRI and compared with DCS as ground truth for regions with (w/) and without (w/o) the lesion in the mapped regions. The w/ subgroup revealed a sensitivity of 100% (w/o 100%), a specificity of 8% (w/o 5%), a positive predictive value of 34% (w/o: 53%), and a negative predictive value (NPV) of 100% (w/o: 100%) for the comparison of rTMS versus DCS. Findings for the comparison of fMRI versus DCS within the w/ subgroup revealed a sensitivity of 32% (w/o: 62%), a specificity of 88% (w/o: 60%), a positive predictive value of 56% (w/o: 62%), and a NPV of 73% (w/o: 60%). Although strengths and weaknesses exist for both rTMS and fMRI, the results show that rTMS is less affected by a brain lesion than fMRI, especially when performing mapping of language-negative cortical regions based on sensitivity and NPV.

Cortical regions involved in semantic processing investigated by repetitive navigated transcranial magnetic stimulation and object naming

BackgroundKnowledge about the cortical representation of semantic processing is mainly derived from functional magnetic resonance imaging (fMRI) or direct cortical stimulation (DCS) studies. Because DCS is regarded as the gold standard in terms of language mapping but can only be used during awake surgery due to its invasive character, repetitive navigated transcranial magnetic stimulation (rTMS)—a non-invasive modality that uses a similar technique as DCS—seems highly feasible for use in the investigation of semantic processing in the healthy human brain. MethodsA total number of 100 (50 left-hemispheric and 50 right-hemispheric) rTMS-based language mappings were performed in 50 purely right-handed, healthy volunteers during an object-naming task. All rTMS-induced semantic naming errors were then counted and evaluated systematically. Furthermore, since the distribution of stimulations within both hemispheres varied between individuals and cortical regions stimulated, all elicited errors were standardized and subsequently related to their cortical sites by projecting the mapping results into the cortical parcellation system (CPS). ResultsOverall, the most left-hemispheric semantic errors were observed after targeting the rTMS to the posterior middle frontal gyrus (pMFG; standardized error rate: 7.3‰), anterior supramarginal gyrus (aSMG; 5.6‰), and ventral postcentral gyrus (vPoG; 5.0‰). In contrast to that, the highest right-hemispheric error rates occurred after stimulation of the posterior superior temporal gyrus (pSTG; 12.4‰), middle superior temporal gyrus (mSTG; 6.2‰), and anterior supramarginal gyrus (aSMG; 6.2‰). ConclusionsAlthough error rates were low, the rTMS-based approach of investigating semantic processing during object naming shows convincing results compared to the current literature. Therefore, rTMS seems a valuable, safe, and reliable tool for the investigation of semantic processing within the healthy human brain.

The relation of object naming and other visual speech production tasks: a large scale voxel-based morphometric study.

We report a lesion–symptom mapping analysis of visual speech production deficits in a large group (280) of stroke patients at the sub-acute stage (<120 days post-stroke). Performance on object naming was evaluated alongside three other tests of visual speech production, namely sentence production to a picture, sentence reading and nonword reading. A principal component analysis was performed on all these tests' scores and revealed a ‘shared’ component that loaded across all the visual speech production tasks and a ‘unique’ component that isolated object naming from the other three tasks. Regions for the shared component were observed in the left fronto-temporal cortices, fusiform gyrus and bilateral visual cortices. Lesions in these regions linked to both poor object naming and impairment in general visual–speech production. On the other hand, the unique naming component was potentially associated with the bilateral anterior temporal poles, hippocampus and cerebellar areas. This is in line with the models proposing that object naming relies on a left-lateralised language dominant system that interacts with a bilateral anterior temporal network. Neuropsychological deficits in object naming can reflect both the increased demands specific to the task and the more general difficulties in language processing.

A neural network for learning the meaning of objects and words from a featural representation

The present work investigates how complex semantics can be extracted from the statistics of input features, using an attractor neural network. The study is focused on how feature dominance and feature distinctiveness can be naturally coded using Hebbian training, and how similarity among objects can be managed. The model includes a lexical network (which represents word-forms) and a semantic network composed of several areas: each area is topologically organized (similarity) and codes for a different feature. Synapses in the model are created using Hebb rules with different values for pre-synaptic and post-synaptic thresholds, producing patterns of asymmetrical synapses. This work uses a simple taxonomy of schematic objects (i.e., a vector of features), with shared features (to realize categories) and distinctive features (to have individual members) with different frequency of occurrence.The trained network can solve simple object recognition tasks and object naming tasks by maintaining a distinction between categories and their members, and providing a different role for dominant features vs. marginal features. Marginal features are not evoked in memory when thinking of objects, but they facilitate the reconstruction of objects when provided as input. Finally, the topological organization of features allows the recognition of objects with some modified features.

Overt attention in natural scenes: Objects dominate features

Whether overt attention in natural scenes is guided by object content or by low-level stimulus features has become a matter of intense debate. Experimental evidence seemed to indicate that once object locations in a scene are known, salience models provide little extra explanatory power. This approach has recently been criticized for using inadequate models of early salience; and indeed, state-of-the-art salience models outperform trivial object-based models that assume a uniform distribution of fixations on objects. Here we propose to use object-based models that take a preferred viewing location (PVL) close to the centre of objects into account. In experiment 1, we demonstrate that, when including this comparably subtle modification, object-based models again are at par with state-of-the-art salience models in predicting fixations in natural scenes. One possible interpretation of these results is that objects rather than early salience dominate attentional guidance. In this view, early-salience models predict fixations through the correlation of their features with object locations. To test this hypothesis directly, in two additional experiments we reduced low-level salience in image areas of high object content. For these modified stimuli, the object-based model predicted fixations significantly better than early salience. This finding held in an object-naming task (experiment 2) and a free-viewing task (experiment 3). These results provide further evidence for object-based fixation selection – and by inference object-based attentional guidance – in natural scenes.

Language and its right-hemispheric distribution in healthy brains: An investigation by repetitive transcranial magnetic stimulation

ObjectRepetitive navigated transcranial magnetic stimulation (rTMS) is increasingly used for preoperative cortical language mapping. Unlike direct cortical stimulation (DCS), and due to its non-invasive character, this technique can provide a map of the distribution of human language in the healthy brain as well as a dysfunctional brain. Although functional magnetic resonance imaging (fMRI) studies have reported interhemispheric functional connectivity between language structures, the way in which the right hemisphere helps bring about language function remains only partially investigated. The present study therefore uses rTMS as a virtual lesion model to investigate the right hemisphere's contribution to language processing in the healthy human brain. MethodsFifty healthy right-handed volunteers (25 males, 25 females, mean age 25.9±5.4years) underwent language mapping of the right hemisphere by rTMS combined with an object naming task. All errors induced by rTMS were categorized into six different error groups (no-response error, hesitation, performance error, neologism, semantic error, and phonological error). Afterwards, the error rates for each category were calculated and visualized through the results' being projected into the cortical parcellation system (CPS). To reveal CPS regions having similar functional properties, an additional principal component analysis (PCA) was performed. ResultsrTMS induced 1485 naming errors out of the 9839 stimulation trains (error rate 15.1%). These errors were located mainly in the right hemisphere's homologues of the left hemisphere's visually cued overt speech area (middle superior temporal gyrus: mSTG) and in the sound-to-articulation dorsal pathway consisting of opercular inferior frontal gyrus (opIFG) and anterior and posterior supramarginal gyrus (aSMG, pSMG) in both male and female brains. In addition, rTMS caused many errors in the global language comprehension area in female brains (right posterior superior temporal gyrus: pSTG), in speech motor areas in the middle and ventral precentral and postcentral gyri (mPrG, vPrG, mPoG, vPoG), and in executive-function areas in the middle and posterior middle frontal gyri (mFMG, pMFG). ConclusionsFor the first time, the present study provides data on the right hemisphere's cortical regions causally related to single word production function (right opIFG, aSMG, pSMG, mSTG), and selectively in female brains (right pSTG), from a large sample of 50 healthy adult brains in a virtual-lesion design. Moreover, speech-motor control regions (right mPrG, vPrG, mPoG, vPoG) and cortical regions supporting language task performance (mMFG, pMFG) in the language-non-dominant right hemisphere are described.

Effects of navigated TMS on object and action naming.

Transcranial magnetic stimulation (TMS) has been used to induce speech disturbances and to affect speech performance during different naming tasks. Lately, repetitive navigated TMS (nTMS) has been used for non-invasive mapping of cortical speech-related areas. Different naming tasks may give different information that can be useful for presurgical evaluation. We studied the sensitivity of object and action naming tasks to nTMS and compared the distributions of cortical sites where nTMS produced naming errors. Eight healthy subjects named pictures of objects and actions during repetitive nTMS delivered to semi-random left-hemispheric sites. Subject-validated image stacks were obtained in the baseline naming of all pictures before nTMS. Thereafter, nTMS pulse trains were delivered while the subjects were naming the images of objects or actions. The sessions were video-recorded for offline analysis. Naming during nTMS was compared with the baseline performance. The nTMS-induced naming errors were categorized by error type and location. nTMS produced no-response errors, phonological paraphasias, and semantic paraphasias. In seven out of eight subjects, nTMS produced more errors during object than action naming. Both intrasubject and intersubject analysis showed that object naming was significantly more sensitive to nTMS. When the number of errors was compared according to a given area, nTMS to postcentral gyrus induced more errors during object than action naming. Object naming is apparently more easily disrupted by TMS than action naming. Different stimulus types can be useful for locating different aspects of speech functions. This provides new possibilities in both basic and clinical research of cortical speech representations.

A Conceptual Lemon: Theta Burst Stimulation to the Left Anterior Temporal Lobe Untangles Object Representation and Its Canonical Color

Object recognition benefits greatly from our knowledge of typical color (e.g., a lemon is usually yellow). Most research on object color knowledge focuses on whether both knowledge and perception of object color recruit the well-established neural substrates of color vision (the V4 complex). Compared with the intensive investigation of the V4 complex, we know little about where and how neural mechanisms beyond V4 contribute to color knowledge. The anterior temporal lobe (ATL) is thought to act as a "hub" that supports semantic memory by integrating different modality-specific contents into a meaningful entity at a supramodal conceptual level, making it a good candidate zone for mediating the mappings between object attributes. Here, we explore whether the ATL is critical for integrating typical color with other object attributes (object shape and name), akin to its role in combining nonperceptual semantic representations. In separate experimental sessions, we applied TMS to disrupt neural processing in the left ATL and a control site (the occipital pole). Participants performed an object naming task that probes color knowledge and elicits a reliable color congruency effect as well as a control quantity naming task that also elicits a cognitive congruency effect but involves no conceptual integration. Critically, ATL stimulation eliminated the otherwise robust color congruency effect but had no impact on the numerical congruency effect, indicating a selective disruption of object color knowledge. Neither color nor numerical congruency effects were affected by stimulation at the control occipital site, ruling out nonspecific effects of cortical stimulation. Our findings suggest that the ATL is involved in the representation of object concepts that include their canonical colors.

Language mapping with verbs and sentences in awake surgery: a review.

Intraoperative language mapping in awake surgery is typically conducted by asking the patient to produce automatic speech and to name objects. These tasks might not map language with sufficient accuracy, as some linguistic processes can only be triggered by tasks that use verbs and sentences. Verb and sentence processing tasks are currently used during surgery, albeit sparsely. Medline, PubMed, and Web of Science records were searched to retrieve studies focused on language mapping with verbs/sentences in awake surgery. We review the tasks reported in the published literature, spell out the language processes assessed by each task, list the cortical and subcortical regions whose stimulation inhibited language processing, and consider the types of errors elicited by stimulation in each region. We argue that using verb tasks allows a more thorough evaluation of language functions. We also argue that verb tasks are preferable to object naming tasks in the case of frontal lesions, as lesion and neuroimaging data demonstrate that these regions play a critical role in verb and sentence processing. We discuss the clinical value of these tasks and the current limitations of the procedure, and provide some guidelines for their development. Future research should aim toward a differentiated approach to language mapping - one that includes the administration of standardized and customizable tests and the use of longitudinal neurocognitive follow-up studies. Further work will allow researchers and clinicians to understand brain and language correlates and to improve the current surgical practice.

Neurophysiologic markers in laryngeal muscles indicate functional anatomy of laryngeal primary motor cortex and premotor cortex in the caudal opercular part of inferior frontal gyrus

ObjectiveThe aim of this study was to identify neurophysiologic markers generated by primary motor and premotor cortex for laryngeal muscles, recorded from laryngeal muscle. MethodsTen right-handed healthy subjects underwent navigated transcranial magnetic stimulation (nTMS) and 18 patients underwent direct cortical stimulation (DCS) over the left hemisphere, while recording neurophysiologic markers, short latency response (SLR) and long latency response (LLR) from cricothyroid muscle. Both healthy subjects and patients were engaged in the visual object-naming task. In healthy subjects, the stimulation was time-locked at 10–300ms after picture presentation while in the patients it was at zero time. ResultsThe latency of SLR in healthy subjects was 12.66±1.09ms and in patients 12.67±1.23ms. The latency of LLR in healthy subjects was 58.5±5.9ms, while in patients 54.25±3.69ms. SLR elicited by the stimulation of M1 for laryngeal muscles corresponded to induced dysarthria, while LLR elicited by stimulation of the premotor cortex in the caudal opercular part of inferior frontal gyrus, recorded from laryngeal muscle, corresponded to speech arrest in patients and speech arrest and/or language disturbances in healthy subjects. ConclusionIn both groups, SLR indicated location of M1 for laryngeal muscles, and LLR location of premotor cortex in the caudal opercular part of inferior frontal gyrus, recorded from laryngeal muscle, while stimulation of these areas in the dominant hemisphere induced transient speech disruptions. SignificanceDescribed methodology can be used in preoperative mapping, and it is expected to facilitate surgical planning and intraoperative mapping, preserving these areas from injuries.

Inducing transient language disruptions by mapping of Broca's area with modified patterned repetitive transcranial magnetic stimulation protocol

Until now there has been no reliable stimulation protocol for inducing transient language disruptions while mapping Broca's area. Despite the promising data of only a few studies in which speech arrest and language disturbances have been induced, certain concerns have been raised. The purpose of this study was to map Broca's area by using event-related navigated transcranial magnetic stimulation (nTMS) to generate a modified patterned nTMS protocol. Eleven right-handed subjects underwent nTMS to Broca's area while engaged in a visual object-naming task. Navigated TMS was triggered 300 msec after picture presentation. The modified patterned nTMS protocol consists of 4 stimuli with an interstimulus interval of 6 msec; 8 or 16 of those bursts were repeated with a burst repetition rate of 12 Hz. Prior to mapping of Broca's area, the primary motor cortices (M1) for hand and laryngeal muscles were mapped. The Euclidian distance on MRI was measured between cortical points eliciting transient language disruptions and M1 for the laryngeal muscle. On stimulating Broca's area, transient language disruptions were induced in all subjects. The mean Euclidian distance between cortical spots inducing transient language disruptions and M1 for the laryngeal muscle was 17.23 ± 4.73 mm. The stimulation paradigm with the modified patterned nTMS protocol was shown to be promising and might gain more widespread use in speech localization in clinical and research applications.