TMS Trains Research Articles

Neural effects of TMS trains on the human prefrontal cortex

How does a train of TMS pulses modify neural activity in humans? Despite adoption of repetitive TMS (rTMS) for the treatment of neuropsychiatric disorders, we still do not understand how rTMS changes the human brain. This limited understanding stems in part from a lack of methods for noninvasively measuring the neural effects of a single TMS train—a fundamental building block of treatment—as well as the cumulative effects of consecutive TMS trains. Gaining this understanding would provide foundational knowledge to guide the next generation of treatments. Here, to overcome this limitation, we developed methods to noninvasively measure causal and acute changes in cortical excitability and evaluated this neural response to single and sequential TMS trains. In 16 healthy adults, standard 10 Hz trains were applied to the dorsolateral prefrontal cortex in a randomized, sham-controlled, event-related design and changes were assessed based on the TMS-evoked potential (TEP), a measure of cortical excitability. We hypothesized that single TMS trains would induce changes in the local TEP amplitude and that those changes would accumulate across sequential trains, but primary analyses did not indicate evidence in support of either of these hypotheses. Exploratory analyses demonstrated non-local neural changes in sensor and source space and local neural changes in phase and source space. Together these results suggest that single and sequential TMS trains may not be sufficient to modulate local cortical excitability indexed by typical TEP amplitude metrics but may cause neural changes that can be detected outside the stimulation area or using phase or source space metrics. This work should be contextualized as methods development for the monitoring of transient noninvasive neural changes during rTMS and contributes to a growing understanding of the neural effects of rTMS.

2108. In-vitro Activity of Five Novel Anti-Fungal Compounds Against Thirty-Two Strains of Talaromyces marneffei

Abstract Background Talaromyces marneffei (Tm) is a thermally dimorphic fungus causing invasive mycosis in human immunodeficiency virus (HIV) infected patients in Southeast Asia and is a leading cause of AIDS-related deaths in this region with mortality on anti-fungal therapy as high as 30%. The limited options, routes of administration, and toxicity of antifungals with established efficacy against Tm calls for assessment of efficacy for additional antifungals against Tm. Here we evaluate the in-vitro efficacy of 5 novel anti-fungal agents against 32 clinical strains of Tm. The agents tested include ibrexafungerp, two manogepix compounds (APX001A and APX2039), olorofim, and oteseconazole. Methods 32 Tm isolates were cultured from clinical samples from patients in Vietnam and identified as Tm by standard morphological characteristics. Inocula were prepared from these clinical samples in conjunction with CLSI standards and plated onto 96-well microplates. Concentrations for each drug ranged from 0.008 µg/mL to 4 µg/mL. AlamarBlueTM, a resazurin-based cell viability indicator dye, was added to the drug-inoculum solution. Use of this reagent enabled utilization of a microplate fluorescence intensity(FI) reader to objectively identify the designated MIC endpoint of 50% inhibition of growth. Methods (Figure 1). MIC endpoint determination using AlamarBlue indicator dye method. Clinical Tm isolates were thawed and plated on Yeast Peptone Dextrose (YPD) agar and grown for 3-5 days at 37°C. Isolates were then sub-cultured on fresh YPD agar and allowed to grow for 3 days prior to inoculum preparation. Inocula were prepared according to CLSI standards. Following suspension in solution, inocula were diluted in PBS until an optical density (OD) of 0.5 to 0.6 was achieved. Inocula were further diluted in RPMI + MOPS and added to the drug-dilution microplates to achieve a final concentration of 1000-5000 cells/mL. After incubation at 37°C for 24 hours, AlamarBlue was added to all wells. Following incubation for an additional 48 hours, fluorescence intensity (FI) was measured using a microplate reader to determine the MIC endpoint of 50% inhibition of fungal growth. Results Of the drugs tested, olorofim showed the highest activity against the 32 isolates, with MICs consistently ≤ 0.008 µg/mL. This was followed by oteseconazole with MICs between ≤ 0.008 and 0.031 µg/mL APX001A with MICs between 0.031 and 0.25 µg/mL and APX2039 with MICs between 0.25 and 4 µg/mL. Ibrexafungerp had the broadest MIC distribution with MICs between 0.063 and 4 µg/mL. Figure 2/Table 1. MIC Endpoint Distribution. Figure 2 shows a scatter plot of MIC endpoints for each drug. Error bars demonstrate the geometric mean and 95% confidence intervals. Table 1 illustrates the MIC endpoint distribution in a graded heat map format. In addition, the absolute values of the geometric mean (GM), mode, MIC50, and MIC90 are displayed at the right side of the table. Both Figure 2 and Table 1 illustrate high efficacy for olorofim and oteseconazole, with low MIC endpoints consistent across the 32 isolates. The manogepix compounds(APX001A and APX2039) demonstrate surprisingly contrasted performance against Tm, despite the similar chemical structure and identical mechanism of action of the drugs. APX001A had significantly lower MIC endpoints compared to APX2039. Ibrexafungerp had the broadest range of MIC endpoints from 0.063 to 4µg/mL and the highest MIC50 and MIC90 of all the drugs. However, a significant proportion of isolates were highly susceptible to the drug. Conclusion In-vitro activity of the 5 drugs tested against the 32 Tm strains was variable, but all should be considered potential candidates for treating Tm infection. To further evaluate the potential role of each drug in treating Tm infection, the next step should be to evaluate each in in-vivo models. Disclosures All Authors: No reported disclosures

Complement Deficiencies Result in Surrogate Pathways of Complement Activation in Novel Polygenic Lupus-like Models of Kidney Injury.

Lupus nephritis (LN) is a major contributor to morbidity and mortality in lupus patients, but the mechanisms of kidney damage remain unclear. In this study, we introduce, to our knowledge, novel models of LN designed to resemble the polygenic nature of human lupus by embodying three key genetic alterations: the Sle1 interval leading to anti-chromatin autoantibodies; Mfge8-/- , leading to defective clearance of apoptotic cells; and either C1q-/- or C3-/- , leading to low complement levels. We report that proliferative glomerulonephritis arose only in the presence of all three abnormalities (i.e., in Sle1.Mfge8 -/- C1q -/- and Sle1.Mfge8 -/- C3 -/- triple-mutant [TM] strains [C1q -/-TM and C3-/- TM, respectively]), with structural kidney changes resembling those in LN patients. Unexpectedly, both TM strains had significant increases in autoantibody titers, Ag spread, and IgG deposition in the kidneys. Despite the early complement component deficiencies, we observed assembly of the pathogenic terminal complement membrane attack complex in both TM strains. In C1q-/- TM mice, colocalization of MASP-2 and C3 in both the glomeruli and tubules indicated that the lectin pathway likely contributed to complement activation and tissue injury in this strain. Interestingly, enhanced thrombin activation in C3-/- TM mice and reduction of kidney injury following attenuation of thrombin generation by argatroban in a serum-transfer nephrotoxic model identified thrombin as a surrogate pathway for complement activation in C3-deficient mice. These novel mouse models of human lupus inform the requirements for nephritis and provide targets for intervention.

P 14 Motor component of speech errors in rTMS language mapping

Objective Using neuronavigated repetitive transcranial magnetic stimulation (rTMS) to disrupt language function during an online-task (e.g., picture naming) is a novel mapping technique which has recently been introduced for presurgical diagnostics in brain tumor patients. However, the method has some limitations due to its rather low specificity. Beyond its dependency on the task, the distinct error categories may have a major effect on the mapping results. We, here, studied the reliability and the spatial localization of rTMS-induced naming errors related to motor-speech function in contrast to semantic language errors. Methods 13 right-handed, healthy volunteers were investigated in 3 consecutive sessions (short-term: 2–5 days, long-term: 21–40 days) by 10 Hz-rTMS. First, the primary motor representation of the face (M1) was mapped by single-pulse TMS. Then, the minimal stimulation intensity which was required to disrupt rhythmic tongue movements by at least three out of five consecutive stimulations over the M1 hotspot was assessed by two independent observers. The “motor inhibition threshold” (MIT) determined the stimulation intensity for the following rTMS language mapping. Online-rTMS was then applied during a picture-naming task using black-and-white drawings of everyday objects which were presented simultaneously (triggered, delay = 0 ms) with the rTMS. The rTMS bursts lasted for 1.5 s (15 pulses). The continuous stimulated area of the left hemisphere had the following anatomical boundaries: middle temporal sulcus (caudal), angular gyrus/ middle parietal sulcus (mediodorsal), hand knob and middle frontal sulcus (medial), triangular part of the inferior frontal gyrus (rostral). Errors were rated by two independent raters by post hoc video analysis. The error frequency (number of errors per 100 TMS trains) as well as the spatial representation and the reliability of distinct motor-speech-related errors, i.e., speech arrest and dysarthria, were compared to language errors associated with semantic processing, i.e., anomia and semantic paraphasia. Test-retest-reliability was assessed by the average intraclass correlation coefficient for a fixed rater (ICC). Results Overall, speech/ language errors were rare events. Amongst the four analyzed error categories, dysarthria represented the most frequent error ( 4.0 ± 2.5 % ) whereas only very few semantic paraphasias were induced ( 0.5 ± 0.4 % ). Motor-speech errors were found significantly more often than semantic language errors ( p 0.01 ). In comparison to semantic errors, the test-retest-reliability of the error rates was lower for motor-speech errors (ICC = 0.45 vs. 0.64). By contrast, the spatial reliability was higher for motor speech errors and showed a strong clustering over M1 and the premotor cortex, especially for the category “arrest”. Conclusion RTMS language mapping is a promising novel technique but the results are still hard to interpret and highly variable. The great majority of errors seems to be at least partially due to motor network disruption rather than being induced by interference with language processing. Further studies, combining different neuroimaging techniques and online-EEG, are mandatory to gain further insight into the underlying mechanisms and the brain-state-dependency of rTMS during language tasks.

P231 The time course of functional recruitment of dorsolateral prefrontal cortex during interference control

Introduction On the basis of neuroimaging (fMRI) and electrophysiological (EEG) evidence, the cascade-of-control model developed for executive processing predicts an early involvement of the dorsolateral prefrontal cortex (DLPFC) in selecting task relevant information, whereas the dorsal anterior cingulate cortex would be involved at later-stages on response related processes. Notwithstanding, the time course of the functional recruitment of the DLPFC has not been causally verified. Here, we applied TMS to interfere DLPFC activity during top-down processing at different temporal windows. Objective To assess the critical time epochs characterizing the recruitment of DLPFC during interference control. Materials and methods On-line TMS was applied over left DLPFC or vertex of 19 healthy controls while performing a computerized Stroop task. TMS trains of 4 pulses every 50 ms (20 Hz) were delivered post-stimulus onset, at one of 3 different time points (50 ms, 250 ms or 450 ms). The active stimulation trials were interleaved with no TMS trials. The four pulses trains were selected to interfere with cognitive processing during a 200 ms critical period defined by prior EEG literature using a similar task. Three types of visual stimuli were presented: congruent (matching color-word), incongruent (non-matching color-word) and neutral (a series of X). Results On the left DLPFC, when TMS bursts were delivered at 250 and 450 ms after the onset of incongruent stimuli, reaction times were significantly longer compared to when these same patterns were applied 50 ms post stimulus onset. No other significant differences were observed when stimulation was applied on this site. In the vertex TMS condition we found significant differences for neutral stimuli when pulses where delivered 450 ms following stimulus onset, as compared to the other time windows and to no TMS stimulation trials. Conclusions In agreement with the cascade-of-control model and correlational EEG evidence, the DLPFC contributes causally to the management of cognitive conflict at early stages of processing (250 ms). Nevertheless, our results suggest that the DLPFC activity is also relevant 450 ms following the presentation of the stimulus. Stimulation over the vertex induced an interference likely on the execution of motor responses to neutral stimulus.

Granulocytes impose a tight bottleneck upon the gut luminal pathogen population during Salmonella typhimurium colitis.

Topological, chemical and immunological barriers are thought to limit infection by enteropathogenic bacteria. However, in many cases these barriers and their consequences for the infection process remain incompletely understood. Here, we employed a mouse model for Salmonella colitis and a mixed inoculum approach to identify barriers limiting the gut luminal pathogen population. Mice were infected via the oral route with wild type S. Typhimurium (S. Tm) and/or mixtures of phenotypically identical but differentially tagged S. Tm strains (“WITS”, wild-type isogenic tagged strains), which can be individually tracked by quantitative real-time PCR. WITS dilution experiments identified a substantial loss in tag/genetic diversity within the gut luminal S. Tm population by days 2–4 post infection. The diversity-loss was not attributable to overgrowth by S. Tm mutants, but required inflammation, Gr-1+ cells (mainly neutrophilic granulocytes) and most likely NADPH-oxidase-mediated defense, but not iNOS. Mathematical modelling indicated that inflammation inflicts a bottleneck transiently restricting the gut luminal S. Tm population to approximately 6000 cells and plating experiments verified a transient, inflammation- and Gr-1+ cell-dependent dip in the gut luminal S. Tm population at day 2 post infection. We conclude that granulocytes, an important clinical hallmark of S. Tm-induced inflammation, impose a drastic bottleneck upon the pathogen population. This extends the current view of inflammation-fuelled gut-luminal Salmonella growth by establishing the host response in the intestinal lumen as a double-edged sword, fostering and diminishing colonization in a dynamic equilibrium. Our work identifies a potent immune defense against gut infection and reveals a potential Achilles' heel of the infection process which might be targeted for therapy.

Effects of Parietal TMS on Visual and Auditory Processing at the Primary Cortical Level – A Concurrent TMS-fMRI Study

Accumulating evidence suggests that multisensory interactions emerge already at the primary cortical level. Specifically, auditory inputs were shown to suppress activations in visual cortices when presented alone but amplify the blood oxygen level-dependent (BOLD) responses to concurrent visual inputs (and vice versa). This concurrent transcranial magnetic stimulation-functional magnetic resonance imaging (TMS-fMRI) study applied repetitive TMS trains at no, low, and high intensity over right intraparietal sulcus (IPS) and vertex to investigate top-down influences on visual and auditory cortices under 3 sensory contexts: visual, auditory, and no stimulation. IPS-TMS increased activations in auditory cortices irrespective of sensory context as a result of direct and nonspecific auditory TMS side effects. In contrast, IPS-TMS modulated activations in the visual cortex in a state-dependent fashion: it deactivated the visual cortex under no and auditory stimulation but amplified the BOLD response to visual stimulation. However, only the response amplification to visual stimulation was selective for IPS-TMS, while the deactivations observed for IPS- and Vertex-TMS resulted from crossmodal deactivations induced by auditory activity to TMS sounds. TMS to IPS may increase the responses in visual (or auditory) cortices to visual (or auditory) stimulation via a gain control mechanism or crossmodal interactions. Collectively, our results demonstrate that understanding TMS effects on (uni)sensory processing requires a multisensory perspective.

TMS of the right angular gyrus modulates priming of pop-out in visual search: combined TMS-ERP evidence

During priming of pop-out, performance at discriminating a pop-out feature target in visual search is affected by whether the target on the previous trial was defined by the same feature as on the upcoming trial. Recent studies suggest that priming of pop-out relies on attentional processes. With the use of simultaneous, combined transcranial magnetic stimulation and event-related potential recording (TMS-ERP), we tested for any critical role of the right angular gyrus (rANG) and left and right frontal eye fields (FEFs)-key attentional sites-in modulating both performance and the ERPs evoked by such visual events. Intertrial TMS trains were applied while participants discriminated the orientation of a color pop-out element in a visual search array. rANG TMS disrupted priming of pop-out, reducing reaction time costs on switch trials and speeding responses when the color of the pop-out target switched. rANG TMS caused a negativity in the ERP elicited in response to the visual stimulus array, starting 210 ms after stimulus onset. Both behavioral and ERP effects were apparent only after rANG TMS, on switch trials, and when the target in the visual search array was presented in the left visual field, with no effects after left or right FEF TMS. These results provide evidence for an attentional reorienting mechanism, which originates in the rANG and is modulated by the implicit memory of the previous trial. The rANG plays a causal role on switch trials during priming of pop-out by interacting with visual processing, particularly in the ipsilateral hemisphere representing the contralateral hemifield.

Brain responses evoked by high-frequency repetitive transcranial magnetic stimulation: An event-related potential study

Many recent studies have used repetitive transcranial magnetic stimulation (rTMS) to study brain-behavior relationships. However, the pulse-to-pulse neural effects of rapid delivery of multiple TMS pulses are unknown largely because of TMS-evoked electrical artifacts limiting recording of brain activity.ObjectiveIn this study, TMS-related artifacts were removed with independent component analysis (ICA), which allowed for the investigation of the neurophysiologic effects of rTMS with simultaneous electroencephalographic (EEG) recordings. Repetitive TMS trains of 10 Hz, 3 seconds (110% of motor threshold) were delivered to the postcentral gyrus and superior parietal lobule in 16 young adults. Simultaneous EEG recordings were made with a TMS-compatible system. The stereotypical pattern of TMS-related electrical artifacts was identified by ICA. Removal of artifacts allowed for identification of a series of five evoked brain potentials occurring within 100 milliseconds of each TMS pulse. With the exception of the first potential, for both areas targeted, there was a quadratic relationship between potential peak amplitude and pulse number within the TMS train. This was characterized by a decrease, followed by a rise in amplitude. ICA is an effective method for removal of TMS-evoked electrical artifacts in EEG data. With the use of this procedure we found that the physiologic responses to TMS pulses delivered in a high-frequency train of pulses are not independent. The sensitivity of the magnitude of these responses to recent stimulation history suggests a complex recruitment of multiple neuronal events with different temporal dynamics.

Absence of linkage between the retinoblastoma gene and hts gene in the LEC rat: a model of human Wilson's disease.

The LEC rat is an authentic model of human Wilson's disease (WD) with an autosomal recessively inherited hepatitis. We investigated linkage between the hepatitis gene (hts) and the rat retinoblas‐toma gene (RB), that is closely linked to the WD gene in humans, to see whether or not the hts gene is located on the syntenic region of WD and is the counterpart of the WD gene. Polymerase chain reaction‐single strand conformation polymorphism analysis with backcross progenies from LEC and TM strains showed that the recombination rate between these two loci was 55.6%, demonstrating that the hts and RB genes are not linked to each other. These data indicate that the hts gene is not the counterpart of the WD gene and that the human syntenic region on which the WD locus and human RB gene are located, is not conserved in the rat genome.

ラットにおけるpepsinogenの新しい多型遺伝子座 (<I>Pg-2</I>)

Only two types of pepsinogens, which are products of the Pg-1 locus, are present in rat urine. In gastric mucosa, however, additional pepsinogen isozymes are expressed. We have found a polymorphism for rat gastric mucosa pepsinogen using agarose gel electrophoresis. Some inbred rat strains expressed a pepsinogen band, while others did not. The trait was found to be controlled by a single autosomal locus. We tentatively designated the locus as Pg-2 with two alleles, Pg-2a for the one controlling presence of the band and Pg-2o for the one controlling absence. Linkage analysis using BN and TM strains revealed that Pg-2 was closely linked to Pg-1 (3.7 +/- 1.8 cM), and that it did not belong to LG I (Hbb and p), LG II (Acon-1 and Mup-1), LG IV (Hao-1 and Svp-1), LG V (Es-1 and Es-3), LG VI (Gc and h), LG IX (RT1), LG X (Fh and Pep-3), nor a LG containing Ahd-2 (as yet undetermined).

Growth characteristics of atypical mycobacteria in water and their comparative resistance to disinfectants.

With the increasing significance of group IV atypical mycobacteria as etiological agents in a variety of infections, studies were conducted to determine their growth capabilities in water and their comparative resistance to disinfectants used to decontaminate hospital equipment. Isolates of Mycobaterium chelonei (TM strains) from peritoneal fluids of patients and peritoneal dialysis machines were able to multiply in commercial distilled water, with generation times at 25 degrees C ranging from 8 to 15 h. Levels of 10(5) to 10(6) cells per ml were attained, and these stationary-phase populations declined only slightly over a 1-year period. Results of studies to determine resistance to disinfectants showed the following. (i) TM strains of M. chelonei cultured in commercial distilled water showed survivors in 2% aqueous formaldehyde (HCHO) solutions up to 24 h; in 8% HCHO, only a 2-log reduction in viable counts was observed over a 2-h sampling period. Reference ATCC strains of M. chelonei and M. fortuitum were rapidly inactivated, with no survivors after 2 h of exposure to 2% HCHO or 15 min of exposure to 8% HCHO. (ii) In 2% alkaline glutaraldehyde, TM strains survived 60 min. whereas ATCC strains showed no survivors after 2 min of contact time. (iii) All M. chelonei and M. fortuitum strains survived 60 min of exposure to concentrations of 0.3 and 0.7 microgram of free chlorine per ml at pH 7.