Probe Response Time Research Articles

Concurrent maintenance of both veridical and transformed working memory representations within unique coding schemes

Abstract In the dynamic environment we live in, the already limited information that human working memory can maintain needs to be constantly updated to optimally guide behaviour. Indeed, previous studies showed that leading up to a response, representations maintained in working memory representations are transformed continuously. This goes hand-in-hand with the removal of task-irrelevant items. However, does such removal also include the representations of stimuli as they were originally, prior to transformation? Here, we assessed the neural representation of task-relevant transformed representations, and the no-longer-relevant veridical representations they originated from. We applied multivariate pattern analysis to electroencephalographic data during maintenance of orientation gratings with and without mental rotation. During maintenance, we perturbed the representational network by means of a visual impulse stimulus, and were thus able to successfully decode veridical as well as imaginary, transformed orientation gratings from impulse-driven activity. The impulse response reflected only task-relevant (cued), but not task-irrelevant (uncued) items, suggesting that the latter were quickly discarded from working memory. By contrast, even though the original cued orientation gratings were also no longer task-relevant after mental rotation, these items continued to be represented next to the rotated ones, in different representational formats. This seemingly inefficient use of scarce working memory capacity was associated with reduced probe response times and may thus serve to increase precision and flexibility in guiding behaviour in dynamic environments.

Two lingering delays in a go/no-go task: mind wandering and caution/uncertainty slow down thought probe response times

ABSTRACT In a go/no-go task, lengthening the inter-trial interval (ITI) or decreasing the press percentage (PP) are known to have decelerating effects on both reaction time and on thought probe response time. The mental causes of these delays remain obscure. We performed an 18-minute online experiment with 60 participants who each performed 8 versions of an attention task (Test of Variables of Attention, ToVA) with different ITIs and PPs. After each block there were mind wandering (MW) thought probes and rating scales for subjective effort and awareness. A version of the ToVA with zero no-go-stimuli spontaneously and implicitly accelerated mean reaction time significantly. That version also quickened three subsequent response times for rating tasks by hundreds of milliseconds, which suggests that the basis of this effect is a lingering mental state. None of the subjective ratings measured were strongly related to the reaction time delay, although MW seems to delay the thought probe response. We conclude that there may be another lingering state besides MW. To perform different tasks participants make mental speed-accuracy trade-offs whereby the participant adopts a lingering mental strategy that speeds up thinking by reducing caution/uncertainty, quickening both reaction times and thought probe response times.

High-Speed Temperature Measurement

In certain applications where temperature changes rapidly, e.g., compressor cylinder or explosion chamber, it is necessary to obtain temperature data with a sample rate high enough to register the change, i.e., the temperature probe response time must be very low. Type E coaxial thermocouples with response time in the range of µs can be an example of such a temperature probe. This paper describes several approaches for high-frequency temperature data obtained using coaxial thermocouples. Individual approaches are described together, as well as their shortcomings. Furthermore, the possible method of data evaluation is discussed.

The level of representation of irrelevant stimuli\u2014Distractor\u2013response binding within and between the senses

Binding theories assume that features of stimuli and executed responses can be integrated together in one event file (Hommel, Visual Cognition, 5, 183–216, 1998; Hommel, Cognitive Sciences, 8, 494–500, 2004). Every reencounter with one or more of the stored features leads to an automatic retrieval of the previously constructed event file and hence of the response—even the repetition of a task-irrelevant distractor stimulus can retrieve a previously encoded response. This so-called distractor–response binding effect is typically investigated using a sequential prime-probe design that allows the orthogonal variation of response relation (response repetition vs. resporrevertnse change) and distractor relation (distractor repetition vs. distractor change), while probe response times and error rates are measured as dependent variable. Previous research has shown that task-relevant stimuli can be represented at different levels (e.g., perceptual and conceptual; see Henson et al., Trends in Cognitive Sciences, 18, 376–384, 2014), yet it is not clear at which level of representation distractor stimuli are processed. In the present study, we focused on the level of representation of response-irrelevant distractor stimuli. To this end, a crossmodal distractor–response binding paradigm was used that enables the differentiation between the perceptual and conceptual representation of the distractor by allowing the systematic repetition and change of conceptual distractor features independent of perceptual repetitions. The results suggest that the repetition of perceptual distractor features is indispensable for the initiation of the retrieval process while the sole repetition of conceptual distractor features is not sufficient to start the retrieval process.

Cell-wide mapping of Orai1 channel activity reveals functional heterogeneity in STIM1-Orai1 puncta.

Upon Ca2+ store depletion, Orai1 channels cluster and open at endoplasmic reticulum-plasma membrane (ER-PM) junctions in signaling complexes called puncta. Little is known about whether and how Orai1 channel activity may vary between individual puncta. Previously, we developed and validated optical recording of Orai channel activity, using genetically encoded Ca2+ indicators fused to Orai1 or Orai3 N or C termini. We have now combined total internal reflection fluorescence microscopy with whole-cell recording to map functional properties of channels at individual puncta. After Ca2+ store depletion in HEK cells cotransfected with mCherry-STIM1 and Orai1-GCaMP6f, Orai1-GCaMP6f fluorescence increased progressively with increasingly negative test potentials and robust responses could be recorded from individual puncta. Cell-wide fluorescence half-rise and -fall times during steps to -100 mV test potential indicated probe response times of <50 ms. The in situ Orai1-GCaMP6f affinity for Ca2+ was 620 nM, assessed by monitoring fluorescence using buffered Ca2+ solutions in "unroofed" cells. Channel activity and temporal activation profile were tracked in individual puncta using image maps and automated puncta identification and recording. Simultaneous measurement of mCherry-STIM1 fluorescence uncovered an unexpected gradient in STIM1/Orai1 ratio that extends across the cell surface. Orai1-GCaMP6f channel activity was found to vary across the cell, with inactive channels occurring in the corners of cells where the STIM1/Orai1 ratio was lowest; low-activity channels typically at edges displayed a slow activation phase lasting hundreds of milliseconds. Puncta with high STIM1/Orai1 ratios exhibited a range of channel activity that appeared unrelated to the stoichiometric requirements for gating. These findings demonstrate functional heterogeneity of Orai1 channel activity between individual puncta and establish a new experimental platform that facilitates systematic comparisons between puncta composition and activity.

Real-time quality control of data from Sea-Wing underwater glider installed with Glider Payload CTD sensor

Profiles observed by Sea-Wing underwater gliders are widely applied in scientific research. However, the quality control (QC) of these data has received little attention. The mismatch between the temperature probe and conductivity cell response times generates erroneous salinities, especially across a strong thermocline. A sensor drift may occur owing to biofouling and biocide leakage into the conductivity cell when a glider has operated for several months. It is therefore critical to design a mature real-time QC procedure and develop a toolbox for the QC of Sea-Wing glider data. On the basis of temperature and salinity profiles observed by several Sea-Wing gliders each installed with a Sea-Bird Glider Payload CTD sensor, a real-time QC method including a thermal lag correction, Argo-equivalent real-time QC tests, and a simple post-processing procedure is proposed. The method can also be adopted for Petrel gliders.

Response inhibition is more effortful than response activation: behavioral and electrophysiological evidence.

The present study aimed to measure the response inhibition by embedding a secondary probe task within a Go/NoGo paradigm. The response time for the probe and the time course of the discrimination process for the probe shown by event-related potentials were measured to investigate the effect of response inhibition. The results showed that the probe response time were longer for the NoGo-probes versus Go-probes, indicating a more cognitively demanding process in processing NoGo stimuli. The event-related potential results showed that the NoGo stimuli evoked a more positive frontal P3 component relative to the Go stimuli. Compared with the NoGo-probes, the Go-probes evoked enhanced N1, but decreased P2 and P3 components over frontocentral scalps, indicating increased orienting process, but decreased selective attention process for the Go-probes. These results indicated that response inhibition (NoGo) was more cognitively demanding than the response activation (Go).

Effects of pH probe lag on bioreactor mixing time estimation

Mixing time is one of the most important characteristics of bioreactors used to validate computational fluid dynamics (CFD) models in bioprocess. The pH tracer based method is commonly used to estimate mixing time by monitoring the pH change after perturbation to the system. However, pH probe lag is known to introduce errors in the test results. To determine the impact of probe lag on the measurement, pH probe response times were investigated. A second order mathematical model was established to describe the probe response profile and calculate the probe transfer function which was used to correct the empirical results. The corrected mixing time was used to validate the CFD models and also showed that the impact of pH probe response time on mixing time measurement is significant even in larger (pilot and manufacturing) scales. In addition, comparison with a conductance based tracer method is also discussed in this paper.

A Molecular Voltmeter Based on Fluorescence Dynamics

In this issue, Hou et al. (1) introduce an elegant method for measuring the absolute voltage across a cell membrane with an accuracy of 10 mV. Their study presents an incisive approach to voltage imaging in which the voltage value is encoded in the temporal dynamics of fluorescence rather than in the raw fluorescence intensity. Together with an engineered microbial rhodopsin with properties amenable to the approach, the method provides a genetically encoded optical read-out independent of the reporter’s expression level and insensitive to variations in common experimental parameters. Their work presents a conceptually new avenue toward developing probes for membrane voltage useful for myriad systems from bacteria to mammalian tissue.

Detection of Steps in Single Molecule Data

Over the past few decades, single molecule investigations employing optical tweezers, AFM and TIRF microscopy have revealed that molecular behaviors are typically characterized by discrete steps or events that follow changes in protein conformation. These events, that manifest as steps or jumps, are short-lived transitions between otherwise more stable molecular states. A major limiting factor in determining the size and timing of the steps is the noise introduced by the measurement system. To address this impediment to the analysis of single molecule behaviors, step detection algorithms incorporate large records of data and provide objective analysis. However, existing algorithms are mostly based on heuristics that are not reliable and lack objectivity. Most of these step detection methods require the user to supply parameters that inform the search for steps. They work well, only when the signal to noise ratio (SNR) is high and stepping speed is low. In this report, we have developed a novel step detection method that performs an objective analysis on the data without input parameters, and based only on the noise statistics. The noise levels and characteristics can be estimated from the data providing reliable results for much smaller SNR and higher stepping speeds. An iterative learning process drives the optimization of step-size distributions for data that has unimodal step-size distribution, and produces extremely low false positive outcomes and high accuracy in finding true steps. Our novel methodology, also uniquely incorporates compensation for the smoothing affects of probe dynamics. A mechanical measurement probe typically takes a finite time to respond to step changes, and when steps occur faster than the probe response time, the sharp step transitions are smoothed out and can obscure the step events. To address probe dynamics we accept a model for the dynamic behavior of the probe and invert it to reveal the steps. No other existing method addresses the impact of probe dynamics on step detection. Importantly, we have also developed a comprehensive set of tools to evaluate various existing step detection techniques. We quantify the performance and limitations of various step detection methods using novel evaluation scales. We show that under these scales, our method provides much better overall performance. The method is validated on different simulated test cases, as well as experimental data.

Enabling faster and smoother handoffs in AP-dense 802.11 wireless networks

Nowadays, 802.11-based wireless networks have gained greater popularity as they cover more schools, restaurants, offices, and cities. Unlike static wireless connections, people expect user-friendly features from 802.11 wireless networking infrastructures such as support for seamless roaming. In this paper, we study the handoff process in large AP-dense 802.11 networks, which are among the most commonly used forms of 802.11 networks. To enable faster and smoother handoffs in these AP-dense networks, we focus on improving the AP scan process, which is a bottleneck to such handoffs. We carry out a series of field experiments and evaluate critical handoff parameters through extensive analysis of the acquired data. From these experiments, we discover two key features, differentiated probe response time and rich AP information hidden in wireless traffic, which can improve the AP scan process. We present our solution, Scan in AP-dense 802.11 Networks (D-Scan for short), that leverages these features to do so. We conduct real-world experiments that show D-Scan’s strong performance compared with current AP scan solutions.

Dual representation of item positions in verbal short-term memory: Evidence for two access modes

Memory sets of N=1 ~ 5 digits were exposed sequentially from left-to-right across the screen, followed by N recognition probes. Probes had to be compared to memory list items on identity only (Sternberg task) or conditional on list position. Positions were probed randomly or in left-to-right order. Search functions related probe response times to set size. Random probing led to ramped, “Sternbergian” functions whose intercepts were elevated by the location requirement. Sequential probing led to flat search functions—fast responses unaffected by set size. These results suggested that items in STM could be accessed either by a slow search-on-identity followed by recovery of an associated location tag, or in a single step by following item-to-item links in study order. It is argued that this dual coding of location information occurs spontaneously at study, and that either code can be utilised at retrieval depending on test demands.

Identical elements model of arithmetic memory: Extension to addition and subtraction

The identical elements (IE) model of arithmetic fact representation (Rickard, 2005; Rickard & Bourne, 1996) was developed and tested with multiplication and division. In Experiment 1, we demonstrated that the model also applies to addition and subtraction by examining transfer of response time (RT) savings between prime and probe problems tested in the same block of trials. As is predicted by the IE model, there were equivalent probe RT savings for addition with identical repetition (prime 6 + 9 --> probe 6 + 9) or an order change (9 + 6 --> 6 + 9), but much greater savings for subtraction with identical repetition (15 - 6 --> 15 - 6) than with an order change (15 - 9 --> 15 - 6), and no savings with an operation change (15 - 9 --> 6 + 9 or 6 + 9 --> 4 15 - 6). In Experiment 2, we examined transfer in simple multiplication and division and demonstrated symmetrical transfer between operations. Cross-operation RT savings were eliminated, however, when the RT analysis included only trials on which both the prime and the probe problems were reportedly solved by direct retrieval. An IE model extended to accommodate savings associated with procedural strategies provides a coherent account of facilitative transfer effects in simple arithmetic.

Does a salient distractor capture attention early in processing?

Kim and Cave (1999) used spatial probes in order to measure the effects of bottom-up and top-down factors on the allocation of spatial attention over time. Subjects searched for a target with a unique shape, with a uniquely colored distractor present on each trial. The singleton distractor captured attention early in processing, whereas attention homed in on the target's location later on. Kim and Cave (1999) concluded that top-down factors cannot prevent the presence of a salient distractor from delaying target selection. The present study tested the idea that such results were obtained only because subjects adopted the strategy of searching for the most salient item. Kim and Cave's (1999) finding was replicated in Experiment 1. In Experiment 2, instead of a feature search, subjects performed a conjunction search-that is, a task that could not be performed using a salience-based strategy. Probe response times were longest at the salient distractor's location at both the short and the long stimulus onset asynchronies. These results suggest that, early in processing, top-down factors can exert their influence and prevent the capture of attention by a salient distractor.

Top-down and bottom-up attentional control: on the nature of interference from a salient distractor.

In two experiments using spatial probes, we measured the temporal and spatial interactions between top-down control of attention and bottom-up interference from a salient distractor in visual search. The subjects searched for a square among circles, ignoring color. Probe response times showed that a color singleton distractor could draw attention to its location in the early stage of visual processing (before a 100-msec stimulus onset asynchrony [SOA]), but only when the color singleton distractor was located far from the target. Apparently the bottom-up activation of the singleton distractor's location is affected early on by local interactions with nearby stimulus locations. Moreover, probe results showed that a singleton distractor did not receive attention after extended practice. These results suggest that top-down control of attention is possible at an early stage of visual processing. In the long-SOA condition (150-msec SOA), spatial attention selected the target location over distractor locations, and this tendency occurred with or without extended practice.

Representations in human visual short-term memory: an event-related brain potential study

Behavioral measures and event-related potentials (ERPs) were recorded from 12 subjects while performing three delayed matching-to-sample tasks. The task instructions indicated whether stimulus locations, shapes or conjunctions of locations and shapes had to be memorized and matched against a probe. Memory load was varied trial-by-trial by cueing one or two of three stimuli for memorization, followed by one probe. ERPs during memorization and probe response times varied as a function of memory load (posterior negative and anterior positive ERP wave), but not between single-feature and conjunction of features, nor was an interaction found between them. The results support and extend hypotheses by Luck and Vogel (Luck, S.J. and Vogel, E.K., The capacity of visual working memory for features and conjunctions. Nature, 390 (1997) 279–281.) that visual short-term memory stores conjunctions of features rather than single features.

Determination of Damaged Starch in Wheat Flour Using an Electrochemical Bienzyme Maltose Probe

The development of an electrochemical biosensor based on a bienzyme maltose probe and a third enzyme α-amylase in solution is reported for the rapid and inexpensive determination of damaged starch. Analytical parameters, such as probe stability, pH, temperature and response time, were optimised. Damaged starch was measured in the range of 5 × 10−6 - 5 × 10−4 mol/L as maltose produced by the enzymatic reaction and the detection limit was calculated according with the free maltose and/or glucose in the sample. The damaged starch was determined in different wheat flours, and the data significantly correlated with those obtained using a reference procedure (r2 = 0.994; P ≤ 0.0001). In addition the results showed a comparable precision (CV < 5%). This method is rapid, inexpensive and friendly for unskilled operators.

Preschool Children's Attention to Television: Visual Attention and Probe Response Times

Moment-to-moment variations in the engagement of young children's cognitive capacity by televised material were examined using a secondary task paradigm. Thirty-five 5-year-olds watched a 35-minSesame Streetprogram containing three types of segments: normal segments, segments with scenes reordered, and segments with incomprehensible language audio tracks. While watching the program, children were to respond quickly to auditory probes distributed across all types of segments and positions within segments. Probe response times and visual attention were recorded. Major findings were: As indicated by longer probe response times, capacity was more effectively engaged if language was comprehensible, provided children were looking at television when probes were presented. If not looking, response times were equally fast across segment types. For normal segments only, there were increases in the engagement of cognitive capacity if a look at the television or the program content had been continuous for some time. The findings provide evidence for, but important refinements of, the hypothesis that young children's ongoing comprehension is a major determinant of their attention to television.

Determination of the volumetric mass transfer coefficient (kLa) using the dynamic “gas out–gas in” method: Analysis of errors caused by dissolved oxygen probes

There are many dynamic methods for measuring the volumetric mass transfer coefficient. The "gas out-gas in" method can directly determine the volumetric mass transfer coefficient in a bioreactor system and provide estimates of the volumetric microbial oxygen uptake rate and the average oxygen saturation concentration at the gas-liquid interface. The errors on these parameters are large if the dissolved oxygen probe response time is not considered. For reliable measurements, deconvolution of the oxygen probe measurements must be made. (c) 1995 John Wiley & Sons, Inc.

On-Line Diagnosis of Do-Probe Condition in the Activated Sludge Process

The dissolved oxygen (DO) probe is repeatedly subjected to a step change of the oxygen concentration with a time interval of 15-30 s. For this purpose an existing measuring technique was used in which the activated sludge was sampled continuously from the aeration tank. At each step the time constant of the probe response is estimated which provides a continuous diagnosis of the probe condition. Therefore the DO concentration measurements along the response are fitted to a first order response model of the probe. It was shown that the probe response time constant is a useful indicator for fouling of the probe membrane.