Spatiotemporal and spectral dynamics of multi-item working memory as revealed by the n-back task using MEG

Multi‐item working memory (WM) is a complex cognitive function thought to arise from specific frequency band oscillations and their interactions. While some theories and consistent findings have been established, there is still a lot of unclarity about the sources, temporal dynamics, and roles of event‐related fields (ERFs) and theta, alpha, and beta oscillations during WM activity. In this study, we performed an extensive whole‐brain ERF and time‐frequency analysis on n‐back magnetoencephalography data from 38 healthy controls. We identified the previously unknown sources of the n‐back M300, the right inferior temporal and parahippocampal gyrus and left inferior temporal gyrus, and frontal theta power increase, the orbitofrontal cortex. We shed new light on the role of the precuneus during n‐back activity, based on an early ERF and theta power increase, and suggest it to be a crucial link between lower‐level and higher‐level information processing. In addition, we provide strong evidence for the central role of the hippocampus in multi‐item WM behavior through the dynamics of theta and alpha oscillatory changes. Almost simultaneous alpha power decreases observed in the hippocampus and occipital fusiform gyri, regions known to be involved in letter processing, suggest that these regions together enable letter recognition, encoding and storage in WM. In summary, this study offers an extensive investigation into the spatial, temporal, and spectral characteristics of n‐back multi‐item WM activity.

The metabolic clinical risk score as a new prognostic model for surgical decision-making in patients with colorectal liver metastases

BACKGROUND AND OBJECTIVES

Selection for surgery in patients with colorectal liver metastases (CRLM) remains inaccurate. We evaluated if CRLM baseline metabolic characteristics, assessed by [18]F-fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸ FDG-PET/CT), could predict postoperative outcomes.

METHODS

In a retrospective series of patients undergoing surgery for CRLM, we defined two groups: the long-term survival (LTS) and early relapse (ER) groups, where the postoperative recurrence-free survivals were ≥5 years or <1 year, respectively. We analyzed the patients in whom baseline ¹⁸ FDG-PET/CT was available. Clinicopathologic parameters, clinical risk score (CRS), and baseline ¹⁸ FDG-PET/CT characteristics were compared between LTS and ER groups. A metabolic CRS (mCRS) was implemented, adding one point to the standard five-point CRS when the highest tumor standardized uptake values (SUV_max )/normal liver mean SUV (SUV_mean(liver) ) ratios were >4.3, defining low- and high-risk mCRS by scores of 0 to 2 and 3 to 6, respectively.

RESULTS

From a series of 450 patients operated for CRLM (mean follow-up of 58 months), we included for analysis 23 and 30 patients in the LTS and ER groups, respectively. Clinicopathologic parameters and CRS were similar in the LTS and ER groups. Median SUV_max /SUV_mean(liver) ratios were higher in ER vs LTS patients (4.2 and 2.8, P = .008, respectively). mCRS was increased in ER patients (P = .024); 61% of LTS patients had low-risk mCRS and 73% of the ER patients had high-risk mCRS (P = .023).

CONCLUSIONS

¹⁸ FDG-PET/CT characteristics combined with traditional CRS may represent a new tool to improve selection for surgery in patients with CRLM.

Tracking the Effects of Top-Down Attention on Word Discrimination Using Frequency-tagged Neuromagnetic Responses

Discrimination of words from nonspeech sounds is essential in communication. Still, how selective attention can influence this early step of speech processing remains elusive. To answer that question, brain activity was recorded with magnetoencephalography in 12 healthy adults while they listened to two sequences of auditory stimuli presented at 2.17 Hz, consisting of successions of one randomized word (tagging frequency = 0.54 Hz) and three acoustically matched nonverbal stimuli. Participants were instructed to focus their attention on the occurrence of a predefined word in the verbal attention condition and on a nonverbal stimulus in the nonverbal attention condition. Steady-state neuromagnetic responses were identified with spectral analysis at sensor and source levels. Significant sensor responses peaked at 0.54 and 2.17 Hz in both conditions. Sources at 0.54 Hz were reconstructed in supratemporal auditory cortex, left superior temporal gyrus (STG), left middle temporal gyrus, and left inferior frontal gyrus. Sources at 2.17 Hz were reconstructed in supratemporal auditory cortex and STG. Crucially, source strength in the left STG at 0.54 Hz was significantly higher in verbal attention than in nonverbal attention condition. This study demonstrates speech-sensitive responses at primary auditory and speech-related neocortical areas. Critically, it highlights that, during word discrimination, top-down attention modulates activity within the left STG. This area therefore appears to play a crucial role in selective verbal attentional processes for this early step of speech processing.

Age of onset determines intrinsic functional brain architecture in Friedreich ataxia

OBJECTIVE

Friedreich ataxia (FRDA) is the commonest hereditary ataxia in Caucasians. Most patients are homozygous for expanded GAA triplet repeats in the first intron of the frataxin (FXN) gene, involved in mitochondrial iron metabolism. Here, we used magnetoencephalography (MEG) to characterize the main determinants of FRDA-related changes in intrinsic functional brain architecture.

METHODS

Five minutes of MEG signals were recorded at rest from 18 right-handed FRDA patients (mean age 27 years, 9 females; mean SARA score: 21.4) and matched healthy individuals. The MEG connectome was estimated as resting-state functional connectivity (rsFC) matrices involving 37 nodes from six major resting state networks and the cerebellum. Source-level rsFC maps were computed using leakage-corrected broad-band (3-40 Hz) envelope correlations. Post hoc median-split was used to contrast rsFC in FRDA patients with different clinical characteristics. Nonparametric permutations and Spearman rank correlation test were used for statistics.

RESULTS

High rank correlation levels were found between rsFC and age of symptoms onset in FRDA mostly between the ventral attention, the default-mode, and the cerebellar networks; patients with higher rsFC developing symptoms at an older age. Increased rsFC was found in FRDA with later age of symptoms onset compared to healthy subjects. No correlations were found between rsFC and other clinical parameters.

CONCLUSION

Age of symptoms onset is a major determinant of FRDA patients' intrinsic functional brain architecture. Higher rsFC in FRDA patients with later age of symptoms onset supports compensatory mechanisms for FRDA-related neural network dysfunction and position neuromagnetic rsFC as potential marker of FRDA neural reserve.

P14.98 Improving the targeting of Gamma-Knife radiosurgery for recurrent high-grade gliomas (WHO grades III and IV) with 11C-Methionine PET/CT

BACKGROUND

The survival of the patients with high-grade gliomas may be improved through a multidisciplinary approach including stereotactic re-irradiation such as Gamma-Knife at recurrence in a selected population. We report our experience in targeting the hypermetabolic areas of high-grade gliomas using 11C-Methionine PET/CT in selected patients.

MATERIAL AND METHODS

We retrospectively evaluated the local response in patients treated by Gamma-Knife for recurrent high-grade gliomas in our Institution between 2000 and 2018, targeting the hypermetabolic area with Methionine PET/CT.

RESULTS

We included 25 patients bearing high-grade gliomas (14 female, 11 male) with a median age of 45 years (5–64). There were 11 WHO grade III gliomas (6 astrocytomas, 5 oligodendrogliomas) and 14 glioblastomas. A total number of 33 Gamma-Knife procedures were performed. In all patients, the targeting was based on the hypermetabolic area as defined by Methionine PET/CT. Four patients were treated concomitantly on 2 or more targets. One patient was treated twice on different targets. We observed a positive response in 29 Gamma-Knife procedures, after a median interval of 2 months (1–33) and no response after 4 procedures (4 glioblastomas). In most cases, progression after Gamma-Knife was observed 4 months after irradiation.

CONCLUSION

Targeting the hypermetabolic areas with Methionine PET/CT was associated with favorable response in most patients treated by Gamma-Knife radiosurgery for local high-grade gliomas recurrence. Our results must be confirmed by a prospective study with regular and homogeneous morphological and metabolic monitoring.

Altered transient brain dynamics in multiple sclerosis: Treatment or pathology?

Multiple sclerosis (MS) is a demyelinating, neuroinflammatory, and -degenerative disease that affects the brain's neurophysiological functioning through brain atrophy, a reduced conduction velocity and decreased connectivity. Currently, little is known on how MS affects the fast temporal dynamics of activation and deactivation of the different large-scale, ongoing brain networks. In this study, we investigated whether these temporal dynamics are affected in MS patients and whether these changes are induced by the pathology or by the use of benzodiazepines (BZDs), an important symptomatic treatment that aims at reducing insomnia, spasticity and anxiety and reinforces the inhibitory effect of GABA. To this aim, we employed a novel method capable of detecting these fast dynamics in 90 MS patients and 46 healthy controls. We demonstrated a less dynamic frontal default mode network in male MS patients and a reduced activation of the same network in female MS patients, regardless of BZD usage. Additionally, BZDs strongly altered the brain's dynamics by increasing the time spent in the deactivating sensorimotor network and the activating occipital network. Furthermore, BZDs induced a decreased power in the theta band and an increased power in the beta band. The latter was strongly expressed in those states without activation of the sensorimotor network. In summary, we demonstrate gender-dependent changes to the brain dynamics in the frontal DMN and strong effects from BZDs. This study is the first to characterise the effect of multiple sclerosis and BZDs in vivo in a spatially, temporally and spectrally defined way.

Evidence for genetically determined degeneration of proprioceptive tracts in Friedreich ataxia

OBJECTIVE

To assess with magnetoencephalography the developmental vs progressive character of the impairment of spinocortical proprioceptive pathways in Friedreich ataxia (FRDA).

METHODS

Neuromagnetic signals were recorded from 16 right-handed patients with FRDA (9 female patients, mean age 27 years, mean Scale for the Assessment and Rating Of ataxia [SARA] score 22.25) and matched healthy controls while they performed right finger movements either actively or passively. The coupling between movement kinematics (i.e., acceleration) and neuromagnetic signals was assessed by the use of coherence at sensor and source levels. Such coupling, that is, the corticokinematic coherence (CKC), specifically indexes proprioceptive afferent inputs to the contralateral primary sensorimotor (cSM1) cortex. Nonparametric permutations and Spearman rank correlation test were used for statistics.

RESULTS

In both groups of participants and movement conditions, significant coupling peaked at the cSM1 cortex. Coherence levels were 70% to 75% lower in patients with FRDA than in healthy controls in both movement conditions. In patients with FRDA, coherence levels correlated with genotype alteration (i.e., the size of GAA1 triplet expansion) and the age at symptom onset but not with disease duration or SARA score.

CONCLUSION

This study provides electrophysiologic evidence demonstrating that proprioceptive impairment in FRDA is mostly genetically determined and scarcely progressive after symptom onset. It also positions CKC as a reliable, robust, specific marker of proprioceptive impairment in FRDA.

Abstract 1610: Getting under the skin: Fat quality in esophageal cancer prognosis

INTRODUCTION

The last few years have seen an increased interest in the role of body mass composition parameters in cancer survival. this study sought to assess the impact of the body mass composition (BMC) on prognosis of locally advanced esophageal cancer (EC) patients beyond the usual quantitative weight loss associated with this condition.

METHODS

Diagnostic CT scans were assessed for BMC in 155 all-stage EC patients at diagnosis. The index (area/height2) of skeletal muscle (SMI), subcutaneous (SFI) and visceral fat (VFI) were delineated on two adjacent slides at the third lumbar vertebra level by two independent investigators using PLANET ONCO® software (DOSIsoft, France). Mean attenuation (or density) of fat tissue was measuring to assess the quality of adipose compartments. Survival and relapse free survival (RFS) were calculated from date of baseline CT-scan.

RESULTS

Interobserver correlations were excellent for all BMC parameters measured (r = 0.94 to 0.99). Remarkably, low subcutaneous fat density (SFD) was associated to better outcome, as were low disease stages. Low C-reactive protein (CRP) levels were also associated with better overall survival (OS). In contrast, low BMI did not affect the patients’ outcome. Relapse free survival (RFS) analysis showed that only high disease stages and SFD remained associated with poor RFS. Stepwise regression showed that the combination of SFD, stage and CRP was an effective model for OS prediction. No parameter was retained for RFS in the multivariate analysis. Detailed results are shown in Table 1.

CONCLUSION

SFD, stages and CRP appeared as robust prognostic factors of OS in EC patients, in contrast with BMI. While SFD and stages were significant in RFS univariate analysis, none of these two parameters were retained in multivariate analyses. These results confirm the validity of BMC assessment for evaluating patient prognosis and show for the first time that adipose tissues and inflammation may have a preponderant impact on cancer prognosis.

ParametersThresholdOSmalefemalep valueHR (95 CI)Low SFD&lt; -95,7&lt; -99,40,000282,2 (1,4-3,5)Low disease stages1+2A vs 2B+3+40,00472,2 (1,2-3,7)Low CRP&lt; 3,200,00532,2 (1,2-3,8)Low BMI&lt;250,130,71 (0,46-1,1)ParametersThresholdRFSmalefemalep valueHR (95 CI)Low SFD&lt; -95,7&lt; -99,40,041,6 (1-2,6)Low disease stages1+2A vs 2B+3+40,0441,8 (1-3,1)N.B. Thresholds for SFD are the sex-specific medians. Thresholds for CRP is the median

Citation Format: Maelle Anciaux, Lieveke Ameye, Thomas Guiot, Patrick Flamen, Serge Goldman, Pieter Demetter, Amélie Deleporte, André Van Gossum, Marianne Paesmans, Vincent Donckier, Alain Hendlisz, Caroline Vandeputte. Getting under the skin: Fat quality in esophageal cancer prognosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1610.

Synchrony, metastability, dynamic integration, and competition in the spontaneous functional connectivity of the human brain

The human brain is functionally organized into large-scale neural networks that are dynamically interconnected. Multiple short-lived states of resting-state functional connectivity (rsFC) identified transiently synchronized networks and cross-network integration. However, little is known about the way brain couplings covary as rsFC states wax and wane. In this magnetoencephalography study, we explore the synchronization structure among the spontaneous interactions of well-known resting-state networks (RSNs). To do so, we extracted modes of dynamic coupling that reflect rsFC synchrony and analyzed their spatio-temporal features. These modes identified transient, sporadic rsFC changes characterized by the widespread integration of RSNs across the brain, most prominently in the β band. This is in line with the metastable rsFC state model of resting-state dynamics, wherein our modes fit as state transition processes. Furthermore, the default-mode network (DMN) stood out as being structured into competitive cross-network couplings with widespread DMN-RSN interactions, especially among the β-band modes. These results substantiate the theory that the DMN is a core network enabling dynamic global brain integration in the β band.

The metabolic clinical risk score (mCRS) as a new prognostic model for surgical decision in patients with colorectal liver metastases

e15094

Background: Selection for surgery in patients with colorectal liver metastases (CRLM) remains poorly accurate. We evaluated if baseline metabolic characteristics of CRLM, as assessed by [18]-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18FDG-PET/CT), may predict the postoperative outcome in patients operated for CRLM. Methods: In a series of 450 patients operated for CRLM, we retrospectively identified 2 groups: The long-term survival (LTS), as defined by postoperative recurrence-free survival (RFS)≥5 years, and the early relapse groups (ER), as defined by RFS < 1 year. Clinicopathologic characteristics, Clinical Risk Score (CRS) and baseline 18FDG-PET/CT metabolic parameters were analyzed. Baseline 18FDG-PET/CT was performed at the time of diagnosis of CRLM, before any preoperative treatment. Low and high-risk CRS were defined by scores of 0 to 2 and 3 to 5, respectively. Metabolic CRS (mCRS) was implemented, using 1 additional point to the standard CRS when the highest tumor standardized uptake value (SUVmax) and normal liver mean SUV (SUVmean(liver)) ratio was > 4.3. Low and high-risk mCRS were defined by scores of 0 to 2 and 3 to 6, respectively. Results: We analyzed 53 patients. No difference was observed between LTS (n = 23) and ER (n = 30) groups for clinicopathologic parameters related to the primary tumor and CRLM, CRS and rates of low/high risk CRS. All metabolic parameters analyzed, including SUVmax and SUVpeak, at the exception of metabolic tumor volume, were significantly increased in ER group. Median SUVmax/SUVmean(liver) ratio was significantly increased in the ER vs LTS, respectively of 4.2 and 2.8 (p = 0.008). mCRS was significantly higher in ER as compared to LTS patients (p = 0.024), while 61% of the LTS patients had a low-risk mCRS and 73% of the ER patients had a high-risk mCRS (p = 0.023). Conclusions: Baseline 18FDG-PET/CT characteristics demonstrate an increased tumor glucose uptake in patients who rapidly recur after curative-intent surgery for CRLM. The introduction of these data into clinical risk model may represent a new tool to improve selection for surgery in patients with CRLM.

Absence of early metabolic response assessed by 18F-FDG PET/CT after initiation of antifibrotic drugs in IPF patients

Background

Idiopathic pulmonary fibrosis (IPF) is characterized by a progressive and irreversible respiratory failure. Non-invasive markers of disease activity are essential for prognosis and evaluation of early response to anti-fibrotic treatments.

Objectives

The aims of this study were to determine whether fluorodeoxyglucose ([18F]-FDG) lung uptake is reduced after initiation of pirfenidone or nintedanib and to assess its possible use as a prognostic factor.

Methods

[18F]-FDG PET/CT was performed in IPF patients and in a murine model of pulmonary fibrosis. PET/CTs were performed at day 8 and day 15 post-instillation of bleomycin in pirfenidone- or vehicule-treated mice. In IPF patients, PET-CT was performed before and 3 months after the initiation of pirfenidone or nintedanib.

Results

In bleomycin-treated mice, pirfenidone significantly reduced the [18F]-FDG uptake compared to vehicule-treated mice at day 15 (p < 0.001), whereas no difference was observed at day 8 after bleomycin administration. In IPF patients, [18F]-FDG lung uptake before and after 3 months of treatment by nintedanib (n = 11) or pirfenidone (n = 14) showed no significant difference regardless the antifibrotic treatment. Moreover, no difference was noticed between patients with progressive or non-progressive disease at one year of follow up.

Conclusions

Pirfenidone significantly reduces the lung [18F]-FDG uptake during the fibrotic phase in a mouse model of IPF. However, these preclinical data were not confirmed in IPF patients 3 months after the initiation of antifibrotic therapy. [18F]-FDG seems therefore not useful in clinical practice to assess the early response of IPF patients to nintedanib or pirfenidone.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-0974-5) contains supplementary material, which is available to authorized users.

Current Imaging Techniques for Lymph Node Staging in Prostate Cancer: A Review

Introduction: Lymph node metastases (LNM) represent a proven prognostic factor for biochemical recurrence (BCR)-free survival, metastatic free survival and overall survival in prostate cancer (PCa). Although pelvic node dissection remains the gold standard for the detection of LNM, novel imaging techniques are entering clinical practice, in the effort to improve LNM detection and spare unnecessary surgeries. Aim of the current review is to describe such imaging techniques and explore their advantages and limitations.

Evidence Acquisition: The National Library of Medicine Database was searched for relevant articles published between January 2013 and August 2018. A wide search was performed including the combination of following words: “Prostate” and “Cancer” and “staging” and “Lymph Node” and “imaging” and (“MRI” or “PET”). The initial list of selected papers was enriched by individual suggestions of the authors of the present review.

Evidence Synthesis: DWI-MRI in detection of lymph node invasion has a sensitivity and specificity of 41 and 94%, respectively. For SPIO MRI using ferumoxtran-10, the sensitivity for detection of LNM with short axis diameter of 5–10 mm is reported at 96.4%, compared to 28.5% with MRI alone. PSMA PET/CT is growing exponentially, both in the initial detection of LNM and for BCR evaluation. Fluciclovine PET could improve detection of subcentimetric pathologic lymph nodes. Sentinel lymph node techniques remain experimental and not validated in the field of PCa.

Conclusions: Molecular imaging, particularly PSMA ligand PET imaging, present interesting diagnostic accuracy in LN diagnosis even in subcentimetric LN. DWI-MRI yields good results in LN involvement evaluation and the use of contrast agent such SPIO may improve the detection rate. The SLN technique is limited to experimental protocols and for intermediate or high-risk PCa. Prospective trials are awaited to evaluate the true clinical impact of these imaging techniques on PCa oncologic outcomes.

Neuromagnetic Cerebellar Activity Entrains to the Kinematics of Executed Finger Movements

This magnetoencephalography (MEG) study aims at characterizing the coupling between cerebellar activity and the kinematics of repetitive self-paced finger movements. Neuromagnetic signals were recorded in 11 right-handed healthy adults while they performed repetitive flexion-extensions of right-hand fingers at three different movement rates: slow (~ 1 Hz), medium (~ 2 Hz), and fast (~ 3 Hz). Right index finger acceleration was monitored with an accelerometer. Coherence analysis was used to index the coupling between right index finger acceleration and neuromagnetic signals. Dynamic imaging of coherent sources was used to locate coherent sources. Coupling directionality between primary sensorimotor (SM1), cerebellar, and accelerometer signals was assessed with renormalized partial directed coherence. Permutation-based statistics coupled with maximum statistic over the entire brain volume or restricted to the cerebellum were used. At all movement rates, maximum coherence peaked at SM1 cortex contralateral to finger movements at movement frequency (F0) and its first harmonic (F1). Significant (statistics restricted to the cerebellum) coherence consistently peaked at the right posterior lobe of the cerebellum at F0 with no influence of movement rate. Coupling between Acc and cerebellar signals was significantly stronger in the afferent than in the efferent direction with no effective contribution of cortico-cerebellar or cerebello-cortical pathways. This study demonstrates the existence of significant coupling between finger movement kinematics and neuromagnetic activity at the posterior cerebellar lobe ipsilateral to finger movement at F0. This coupling is mainly driven by spinocerebellar, presumably proprioceptive, afferences.