Concurrent Signals Research Articles

EEG spatiospectral patterns and their link to fMRI BOLD signal via variable hemodynamic response functions

BackgroundSpatial and temporal resolution of brain network activity can be improved by combining different modalities. Functional Magnetic Resonance Imaging (fMRI) provides full brain coverage with limited temporal resolution, while electroencephalography (EEG), estimates cortical activity with high temporal resolution. Combining them may provide improved network characterization. New MethodWe examined relationships between EEG spatiospectral pattern timecourses and concurrent fMRI BOLD signals using canonical hemodynamic response function (HRF) with its 1st and 2nd temporal derivatives in voxel-wise general linear models (GLM). HRF shapes were derived from EEG-fMRI time courses during “resting-state”, visual oddball and semantic decision paradigms. ResultsThe resulting GLM F-maps self-organized into several different large-scale brain networks (LSBNs) often with different timing between EEG and fMRI revealed through differences in GLM-derived HRF shapes (e.g., with a lower time to peak than the canonical HRF). We demonstrate that some EEG spatiospectral patterns (related to concurrent fMRI) are weakly task-modulated. Comparison with existing method(s)Previously, we demonstrated 14 independent EEG spatiospectral patterns within this EEG dataset, stable across the resting-state, visual oddball and semantic decision paradigms. Here, we demonstrate that their time courses are significantly correlated with fMRI dynamics organized into LSBN structures. EEG-fMRI derived HRF peak appears earlier than the canonical HRF peak, which suggests limitations when assuming a canonical HRF shape in EEG-fMRI. ConclusionsThis is the first study examining EEG-fMRI relationships among independent EEG spatiospectral patterns over different paradigms. The findings highlight the importance of considering different HRF shapes when spatiotemporally characterizing brain networks using EEG and fMRI.

Age Effects on Concurrent Speech Segregation by Onset Asynchrony.

Purpose For elderly listeners, it is more challenging to listen to 1 voice surrounded by other voices than for young listeners. This could be caused by a reduced ability to use acoustic cues-such as slight differences in onset time-for the segregation of concurrent speech signals. Here, we study whether the ability to benefit from onset asynchrony differs between young (18-33 years) and elderly (55-74 years) listeners. Method We investigated young (normal hearing, N = 20) and elderly (mildly hearing impaired, N = 26) listeners' ability to segregate 2 vowels with onset asynchronies ranging from 20 to 100 ms. Behavioral measures were complemented by a specific event-related brain potential component, the object-related negativity, indicating the perception of 2 distinct auditory objects. Results Elderly listeners' behavioral performance (identification accuracy of the 2 vowels) was considerably poorer than young listeners'. However, both age groups showed the same amount of improvement with increasing onset asynchrony. Object-related negativity amplitude also increased similarly in both age groups. Conclusion Both age groups benefit to a similar extent from onset asynchrony as a cue for concurrent speech segregation during active (behavioral measurement) and during passive (electroencephalographic measurement) listening.

Age-Related Effects on Cross-Modal Duration Perception.

Reliable duration perception of external events is necessary to coordinate perception with action, precisely discriminate speech, and for other daily functions. Visual duration perception can be heavily influenced by concurrent auditory signals; however, age-related effects on this process have received minimal attention. In the present study, we examined the effect of aging on duration perception by quantifying (1)duration discrimination thresholds, (2)auditory temporal dominance, and (3)visual duration expansion/compression percepts induced by an accompanying auditory stimulus of longer/shorter duration. Duration discrimination thresholds were significantly greater for visual than auditory tasks in both age groups, however there was no effect of age. While the auditory modality retained dominance in duration perception with age, older adults still performed worse than young adults when comparing durations of two target stimuli (e.g., visual) in the presence of distractors from the other modality (e.g., auditory). Finally, both age groups perceived similar visual duration compression, whereas older adults exhibited visual duration expansion over a wider range of auditory durations compared to their younger counterparts. Results are discussed in terms of multisensory integration and possible decision strategies that change with age.

Mapping Optogenetically Driven Single-Vessel fMRI with Concurrent Neuronal Calcium Recordings in the Rat Hippocampus

The hippocampus plays critical roles in learning and memory, as well as pathological states such as epilepsy and Alzheimer’s disease. To better understand its neural network function, the multi-modality methodology has been implemented in both in vitro and in vivo conditions. However, the large-scale hippocampal vascular hemodynamic responses linked to specific neural activity remains to be elucidated at the single-vessel level through the hippocampus. We merged the fiber optic calcium recording with optogenetically driven single-vessel fMRI to obtain concurrent neuronal calcium signal with blood-oxygen-level-dependent and cerebral-blood-volume (CBV) signal from individual venules and arterioles, respectively, which are aligned in an interleaved pattern to circulate blood through the hippocampus. This multi-modal fMRI platform detects specific spatiotemporal hemodynamic patterns from hippocampal vasculature correlated with physiologically evoked and spreading depression-like calcium events. The calcium event-related single-vessel fMRI hemodynamic modeling reveals significantly reduced neurovascular coupling efficiency upon spreading depression-like events, providing a direct measure of the hippocampal vascular function at varied states in animal models.

Efficient Multisignal 2–4-GHz Power Amplifier With Power Tracking

The goal of the work presented in this paper is to demonstrate an efficient method of amplifying multiple concurrent signals over a large bandwidth using a supply modulation approach. A single-stage octave bandwidth (2–4 GHz) power amplifier (PA) with greater than 10-W output power and drain efficiency ranging from 48%–60% is presented. The amplifier is tested with several reduced-bandwidth supply modulation trajectories that are constructed as an even-termed power series of a 10-MHz LTE signal envelope. A greater than 30% point increase in $\eta _{D}$ is achieved while maintaining less than −45-dB ACPR with digital predistortion (DPD). Two 10-MHz LTE signals with 800-MHz spacing are then amplified using a similar bandwidth-reduction technique. A greater than 20% point increase in $\eta _{D}$ is seen with an improvement in linearity through the use of multidimensional DPD. The method presented here can be extended to more than two concurrent signals of arbitrary spacing for a PA with large RF bandwidth.

A FHD 1080, 120 fps CMOS image sensor with two step SS-ADC

This paper presents a full high definition 1920 × 1080 pixel, 120 frames/s CMOS image sensor with two-step single-slope (TS-SS) ADC. The column-parallel TS-SS ADC and binary subtractor are used to convert photodiode voltage to the final 10-bit digital data. Therefore, there is no need for the pixel readout, noise suppression or comparator offset cancellation circuits to be used in the columns. A new ramp signal generator is proposed to generate 32 concurrent and identical ramp signals. TS-SS ADC improves the conversion speed while reducing the power consumption level as well. The proposed image sensor has been designed using TSMC 0.18 μm 1-poly 4-metal standard process. The simulation results show that the total comparator referred noise to the FD node in 1 Hz–100 MHz range is 0.574 mV and, also the total power consumption is about 100 mW.

Auditor Industry Specialization and Accounting Estimates: Evidence from Asset Impairments

SUMMARYThis study examines whether auditor competencies developed through industry specialization play a role in monitoring client firms' accounting estimates. Specifically, I focus on asset impairment decisions as a key accounting estimate given managers incentives to hide these losses and the PCAOB's criticisms of auditors' testing in this area. Impairments examined in this study relate to goodwill and intangibles, other long-lived assets, and investment securities. Using the portfolio share approach to measure office level specialization, I find that client firms engaging industry specialist auditors exhibit a greater propensity to record, and record larger, impairments relative to client firms engaging auditors with less specialization. The results also demonstrate that impairments recognized by clients of specialist auditors are more positively associated with concurrent bad news signals, suggesting that these losses are recognized on a more timely basis. This evidence enhances our understanding of the factors affecting auditors' ability to evaluate complex accounting estimates.Data Availability: Data are available from the public sources cited in the text.

Functional optical coherence tomography of neurovascular coupling interactions in the retina.

Quantitative evaluation of retinal neurovascular coupling is essential for a better understanding of visual function and early detection of eye diseases. However, there is no established method to monitor coherent interactions between stimulus-evoked neural activity and hemodynamic responses at high resolution. Here, we report a multimodal functional optical coherence tomography (OCT) imaging methodology to enable concurrent intrinsic optical signal (IOS) imaging of stimulus-evoked neural activity and hemodynamic responses at capillary resolution. OCT angiography guided IOS analysis was used to separate neural-IOS and hemodynamic-IOS changes in the same retinal image sequence. Frequency flicker stimuli evoked neural-IOS changes in the outer retina; that is, photoreceptor layer, first and then in the inner retina, including outer plexus layer (OPL), inner plexiform layer (IPL), and ganglion cell layer (GCL), which were followed by hemodynamic-IOS changes primarily in the inner retina; that is, OPL, IPL, and GCL. Different time courses and signal magnitudes of hemodynamic-IOS responses were observed in blood vessels with various diameters.

Effects of hypoxia on swimming and sensing in a weakly electric fish.

Low dissolved oxygen (hypoxia) can severely limit fish performance, especially aerobically expensive behaviours including swimming and acquisition of sensory information. Fishes can reduce oxygen requirements by altering these behaviours under hypoxia, but the underlying mechanisms can be difficult to quantify. We used a weakly electric fish as a model system to explore potential effects of hypoxia on swim performance and sensory information acquisition, which enabled us to non-invasively record electric signalling activity used for active acquisition of sensory information during swimming. To quantify potential effects of hypoxia, we measured critical swim speed (Ucrit) and concurrent electric signalling activity under high- and low-dissolved oxygen concentrations in a hypoxia-tolerant African mormyrid fish, Marcusenius victoriae Fish were maintained under normoxia for 6 months prior to experimental treatments, and then acclimated for 8 weeks to normoxia or hypoxia and tested under both conditions (acute: 4 h exposure). Acute hypoxia exposure resulted in a significant reduction in both Ucrit and electric signalling activity in fish not acclimated to hypoxia. However, individuals acclimated to chronic hypoxia were characterized by a higher Ucrit under both hypoxia and normoxia than fish acclimated to normoxia. Following a 6 month re-introduction to normoxia, hypoxia-acclimated individuals still showed increased performance under acute hypoxic test conditions, but not under normoxia. Our results highlight the detrimental effects of hypoxia on aerobic swim performance and sensory information acquisition, and the ability of fish to heighten aerobic performance through acclimation processes that can still influence performance even months after initial exposure.

Abstract 5046: Bisphenol AF promotes ER+ breast cancer through amphiregulin-mediated ER-RTK signaling crosstalk

Abstract Bisphenol AF (BPAF), a BPA analog, is widely used in the manufacturing of plastics, and has been detected in the environment and in human urine samples. Since BPAF may exhibit more potent endocrine-disrupting activities than BPA, the potential effect of BPAF exposure on breast cancer risk is a health concern. Previous reports highlight the interaction of BPAF with estrogen receptors (ERs), but the molecular pathways of BPAF-mediated cellular activities remain unclear. Therefore, we investigated BPAF-mediated cellular responses in MCF-7 and T47D ER+ breast cancer cells. Results from MTT and clonogenic assays indicated that BPAF (0.01 – 5 µM) induces cell proliferation in a concentration-dependent manner. Cell cycle analysis showed that BPAF (0.5 – 1 µM) significantly increased the percentage of cells in S phase and decreased cells in G0/G1 phase. Data from luciferase reporter assays indicated that BPAF potently activated estrogen response element (ERE)-mediated transcription, which was accompanied by the upregulation and activation/phosphorylation of ERα and ERβ. These data demonstrate that BPAF is a potent endocrine disruptor. Importantly, we also found that BPAF induces ErbB3 phosphorylation, and significantly activates downstream PI3K/Akt and MAPK pathways in both cell lines, as indicated by increased Akt, Erk1/2, and Src phosphorylation. We next examined the mRNA levels of key regulators downstream of ER and receptor tyrosine kinase (RTK) pathways, including AREG, TFF1, MYC, IGF1R/2R, NRG1, EGFR, ERRB3, ESR1/2, and CCND1, in BPAF-treated cells. We found that the most significantly upregulated gene by BPAF was AREG (Amphiregulin), an ER-targeted gene that encodes an RTK ligand protein. Concurrent ER and RTK signaling activation with AREG upregulation suggests that BPAF induces ER-RTK crosstalk through AREG-mediated signaling. To demonstrate the impact of ER signaling on BPAF-induced ER-RTK crosstalk, we blocked estrogen signaling with ICI-182,780 (Fulvestrant) in BPAF-treated cells, and found that estrogen signaling inhibition significantly suppressed BPAF-associated cell growth, ERE-mediated transcriptional activity, and signaling in ER and RTK pathways. We next examined the effect of AREG knockdown on the signaling in both RTK and ER pathways to determine the role of AREG in BPAF-induced ER-RTK crosstalk. Our data indicated that AREG knockdown not only markedly inhibited BPAF-induced proliferation and RTK signaling, but also significantly downregulated ER-mediated transcription. Overall, we demonstrated that ER-RTK crosstalk is essential for BPAF-induced oncogenic cellular responses. Importantly, we identified AREG as a critical mediator of the BPAF-induced signaling interactions. These novel findings highlight the potential clinical implications of BPAF-associated ER+ breast cancer risk and underscore the necessity to further evaluate BPAF as an endocrine disruptor. Citation Format: Qingxia Zhao, Amanda B. Parris, Erin W. Howard, Ying Xing, Xiaohe Yang. Bisphenol AF promotes ER+ breast cancer through amphiregulin-mediated ER-RTK signaling crosstalk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5046.

(Pro)renin receptor: Involvement in diabetic retinopathy and development of molecular targeted therapy.

The renin–angiotensin system (RAS), a crucial regulator of systemic blood pressure (circulatory RAS), plays distinct roles in pathological angiogenesis and inflammation in various organs (tissue RAS), such as diabetic microvascular complications. Using ocular clinical samples and animal disease models, we elucidated molecular mechanisms in which tissue RAS excites the expression of vascular endothelial growth factor (VEGF)‐A responsible for retinal inflammation and angiogenesis, the two major pathological events in diabetic retinopathy (DR). Furthermore, we showed the involvement of (pro)renin receptor [(P)RR] in retinal RAS activation and its concurrent intracellular signal transduction (e.g., extracellular signal‐regulated kinase); namely, the (P)RR‐induced dual pathogenic bioactivity referred to as the receptor‐associated prorenin system. Indeed, neovascular endothelial cells in the fibrovascular tissue collected from eyes with proliferative DR were immunoreactive for the receptor‐associated prorenin system components including prorenin, (P)RR, phosphorylated extracellular signal‐regulated kinase and VEGF‐A. Protein levels of soluble (P)RR increased with its positive correlations with prorenin, renin enzymatic activity and VEGF in the vitreous of proliferative DR eyes, suggesting a close link between (P)RR and VEGF‐A‐driven angiogenic activity. Furthermore, we revealed an unsuspected, PAPS‐independent role of (P)RR in glucose‐induced oxidative stress. Recently, we developed an innovative single‐strand ribonucleic acid interference molecule selectively targeting human and mouse (P)RR, and confirmed its efficacy in suppressing diabetes‐induced retinal inflammation in mice. Our data using clinical samples and animal models suggested the significant implication of (P)RR in the pathogenesis of DR, and the potential usefulness of the ribonucleic acid interference molecule as a therapeutic agent to attenuate ocular inflammation and angiogenesis.

Exploiting the synergistic effect of concurrent data signals: Low-level fusion of liquid chromatographic with dual detection data

A low-level data fusion strategy was developed and implemented for data processing of second-order liquid chromatographic data with dual detection, i.e. absorbance and fluorescence monitoring. The synergistic effect of coupling individual information provided by two different detectors was evaluated by analyzing the results gathered after the application of a series of data preprocessing steps and chemometric resolution. The chemometric modeling involved data analysis by MCR-ALS, PARAFAC and N-PLS. Their ability to handle the new data block was assessed through the estimation of the analytical figures of merits achieved in the prediction of a validation set containing fifteen fluorescent and non-fluorescent veterinary active ingredients that can be found in poultry litter. Eventually, the feasibility of the application of the fusion strategy to real poultry litter samples containing the studied compounds was verified.

What You Don't Notice Can Harm You: Age-Related Differences in Detecting Concurrent Visual, Auditory, and Tactile Cues.

Objective This research sought to determine whether people can perceive and process three nonredundant (and unrelated) signals in vision, hearing, and touch at the same time and how aging and concurrent task demands affect this ability. Background Multimodal displays have been shown to improve multitasking and attention management; however, their potential limitations are not well understood. The majority of studies on multimodal information presentation have focused on the processing of only two concurrent and, most often, redundant cues by younger participants. Method Two experiments were conducted in which younger and older adults detected and responded to a series of singles, pairs, and triplets of visual, auditory, and tactile cues in the absence (Experiment 1) and presence (Experiment 2) of an ongoing simulated driving task. Detection rates, response times, and driving task performance were measured. Results Compared to younger participants, older adults showed longer response times and higher error rates in response to cues/cue combinations. Older participants often missed the tactile cue when three cues were combined. They sometimes falsely reported the presence of a visual cue when presented with a pair of auditory and tactile signals. Driving performance suffered most in the presence of cue triplets. Conclusion People are more likely to miss information if more than two concurrent nonredundant signals are presented to different sensory channels. Application The findings from this work help inform the design of multimodal displays and ensure their usefulness across different age groups and in various application domains.

A New Approach to Design a Broadband Doherty Power Amplifier via Dual-Transformation Real Frequency Technique

A novel dual-transformation simplified real frequency technique is proposed in this paper to synthesize a broadband Doherty power amplifier (DPA). The proposed method can realize the co-design of the carrier and peaking output matching networks to achieve dual-impedance transformation at back-off (BO) and saturation simultaneously. To realize this method, a generalized driving point function with different loads of the matching network is proposed, and weight factors are adopted to combine the separate target functions to form a united one. Compared with conventional designs, no initial guess is required and additional compensating lines are eliminated to improve the performance of the DPA. Based on the proposed technique, a broadband DPA is designed and fabricated across 2.2-3.7 GHz (51% fractional bandwidth). The measurement results show that the designed DPA has a 6-dB BO efficiency of 45%-53% and a saturated output power of 43-44.6 dBm over 1.5 GHz bandwidth. Various modulated signals including 80-MHz long-term evolution-advanced signal and concurrent dual-band signal are employed to validate the DPA. In this way, the DPA can achieve an average efficiency of 45.3%-55.9% at 6.5-dB BO with the adjacent channel leakage ratio levels better than -48.6 dBc by utilizing digital predistortion.

Cognitive Full-Duplex Decode-and-Forward Relaying Networks With Usable Direct Link and Transmit-Power Constraints

The performance of an underlay cognitive radio network that coexists with a primary destination is studied in terms of the outage probability. The investigated secondary network comprises a source-destination pair communicating under the assistance of a full-duplex decode-and-forward relay. We consider the following key aspects pertinent to the underlay cognitive-radio approach and to the full-duplex operation at the relay: the transmit power constraint of the cognitive network by the maximum interference tolerated at the primary destination, as well as by the maximum-available transmit power at the cognitive terminals; the impact of the residual self-interference inherent to the relay; and the use of a joint-decoding technique at the destination in order to combine the concurrent signals coming from the source and relay, which enables the treatment of the direct-link transmission as information signal, rather than as interference. Herein, the joint effect of the maximum interference power constraint and the residual self-interference are both examined. To this end, an arbitrary power allocation between source and relay is allowed. Then, an accurate closed-form approximation to the outage probability is proposed, from which an asymptotic expression is derived for the high SNR ratio regime. Our analytical results are validated via Monte Carlo simulations. Importantly, we show that a maximum-available transmit power not only saves energy but also reduces the outage probability at medium to high SNR ratio.

Compositional Proteomics: Effects of Spatial Constraints on Protein Quantification Utilizing Isobaric Tags.

Mass spectrometry (MS) has become an accessible tool for whole proteome quantitation with the ability to characterize protein expression across thousands of proteins within a single experiment. A subset of MS quantification methods (e.g., SILAC and label-free) monitor the relative intensity of intact peptides, where thousands of measurements can be made from a single mass spectrum. An alternative approach, isobaric labeling, enables precise quantification of multiple samples simultaneously through unique and sample specific mass reporter ions. Consequently, in a single scan, the quantitative signal comes from a limited number of spectral features (≤11). The signal observed for these features is constrained by automatic gain control, forcing codependence of concurrent signals. The study of constrained outcomes primarily belongs to the field of compositional data analysis. We show experimentally that isobaric tag proteomics data are inherently compositional and highlight the implications for data analysis and interpretation. We present a new statistical model and accompanying software that improves estimation accuracy and the ability to detect changes in protein abundance. Finally, we demonstrate a unique compositional effect on proteins with infinite changes. We conclude that many infinite changes will appear small and that the magnitude of these estimates is highly dependent on experimental design.

Spontaneous mechanical and electrical activities of human calf musculature at rest assessed by repetitive single-shot diffusion-weighted MRI and simultaneous surface electromyography.

Assessment of temporal and spatial relations between spontaneous mechanical activities in musculature (SMAM) at rest as revealed by diffusion-weighted imaging (DWI) and electrical muscular activities in surface EMG (sEMG). Potential influences of static and radiofrequency magnetic fields on muscular activity on sEMG measurements at rest were examined systematically. Series of diffusion-weighted stimulated echo planar imaging were recorded with concurrent sEMG measurements. Electrical activities in sEMG were analyzed by non-parametric Friedman and two-sample Kolmogorov-Smirnov test. Direct correlation of both modalities was investigated by temporal mapping of electrical activity in sEMG to DWI repetition interval. Electrical activities in sEMG and number of visible SMAMs in DWI showed a strong correlation (ρ = 0.9718). High accordance between sEMG activities and visible SMAMs in DWI in a near-surface region around sEMG electrodes was achieved. Characteristics of sEMG activities were almost similar under varying magnetic field conditions. Visible SMAMs in DWI have shown a close and direct relation to concurrent signals recorded by sEMG. MR-related magnetic fields had no significant effects on findings in sEMG. Hence, appearance of SMAMs in DWI should not be considered as imaging artifact or as effects originating from the special conditions of MR examinations. Spatial and temporal distributions of SMAMs indicate characteristics of spontaneous (microscopic) mechanical muscular action at rest. Therefore, DWI techniques should be considered as non-invasive tools for studying physiology and pathophysiology of spontaneous activities in resting muscle. Magn Reson Med 79:2784-2794, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Activating mutation of PDGFRB gene in a rare cardiac undifferentiated intimal sarcoma of the left atrium: a case report.

Cardiac sarcoma is a rare malignant tumor with undefined genetic mutations and no targeted therapy. Here in one rare case of undifferentiated cardiac intimal sarcoma (IS), a next-generation sequencing based assay, MSK-IMPACT (Memorial Sloan Kettering - Integrated Mutation Profiling of Actionable Cancer Targets), identified a somatic, activating mutation in PDGFRB, along with amplification of PDGFRA. This E472D mutation of PDGFRB was discovered for the first time in IS. These findings suggest that concurrent aberrant PDGFRA and PDGFRB signaling may be a diagnostic biomarker and molecular therapeutic target of IS of the heart.

Concurrent Dual-Band RF Signal Measurement With Adaptive Blind Feedforward Cancellation of Wideband Receiver Nonlinearities

This paper proposes a novel method for the digital blind cancellation of nonlinear distortion in the concurrent dual-band receiver, for the accurate acquisition and testing of dual-band radio frequency signal. The nonlinearities are incurred by the wideband low-noise amplifier when measuring two signals concurrently. The proposed blind algorithm extracts the nonlinearities in the two measured signals and then cancels out the nonlinear distortion by subtracting it from the two signals, using a feedforward scheme iteratively [blind feedforward cancellation (BFFC)], based on the state-of-the-art 2-D memoryless polynomial model. An extended application by reducing the model complexity using the 2-D modified memoryless polynomial model has also been evaluated to be effective. Experimental results have shown that the proposed method eliminates the nonlinearities in the dual-band and improves the signal quality significantly. The convergence behavior of the BFFC technique is further augmented by using a general iterative equation. All the results have been compared with the previous blind postcompensation methods and the results demonstrate the superiority of the new method.

The Spatiotemporal Limits of Developmental Erk Signaling

Animal development is characterized by signaling events that occur at precise locations and times within the embryo, but determining when and where such precision is needed for proper embryogenesis has been a long-standing challenge. Here we address this question for extracellular signal regulated kinase (Erk) signaling, a key developmental patterning cue. We describe an optogenetic system for activating Erk with high spatiotemporal precision in vivo. Implementing this system in Drosophila, we find that embryogenesis is remarkably robust to ectopic Erk signaling, except from 1 to 4 hr post-fertilization, when perturbing the spatial extent of Erk pathway activation leads to dramatic disruptions of patterning and morphogenesis. Later in development, the effects of ectopic signaling are buffered, at least in part, by combinatorial mechanisms. Our approach can be used to systematically probe the differential contributions of the Ras/Erk pathway and concurrent signals, leading to a more quantitative understanding of developmental signaling.