前置线索对动作准备不同阶段的影响

以动作准备的左右手线索和方向线索为对象,结合LRP(单侧化预备电位)潜伏期和CNV(伴随性负变化)振幅等脑电指标,探讨不同前置线索对动作准备各个阶段的影响。结果发现:(1)当两个线索相继呈现时,"方向线索 手线索"诱发的CNV振幅大于"手线索 方向线索",说明在前一情景下,方向线索呈现时,被试同时对左右两手的运动程序做准备;(2)在"手线索 方向线索"情景下,LRP的启动先于方向线索的呈现。上述结果与"动作准备的层次假设"相符合,说明动作参数的具体化过程遵循手、手指、方向、力等的顺序进行。此外,本研究没有发现支持"方向线索的准备可易化LRP启动后的运动阶段"的证据。     

Parallel central processing between tasks: Evidence from lateralized readiness potentials

The present dual-task study used lateralized readiness potentials (LRPs) and behavioral measures to determine whether response activation for Task 1 and Task 2 can occur in parallel. We also examined whether task similarity (known as dimensional overlap) increases parallel central processing by making it difficult to selectively activate one task set. With dimensional overlap, the behavioral data replicated previous findings of backward correspondence effects: The Task 1 response was influenced by its compatibility with the Task 2 response. This finding suggests parallel response activation. The LRP data supported this conclusion: Task 2 response activation (indexed by the LRP) began before Task 1 central operations had finished. When there was no dimensional overlap, backward correspondence effects could not be measured, but the LRP data confirmed that parallel response activation still occurred. We argue that parallel response activation does occur, perhaps due to accidental activation of Task 2 mapping rules when the intention is to selectively execute Task 1 mapping rules.     

The lateralized readiness potential as an on-line measure of central response activation processes

The lateralized readiness potential (LRP) is an electrophysiological indicator of the central activation of motor responses. Procedures for deriving the LRP on the basis of event-related brain potential (ERP) waveforms obtained over the left and right motor cortices are described, and some findings are summarized that show that the LRP is likely to reflect activation processes within the motor cortex. Two experiments investigating spatial S-R compatibility effects are reported that demonstrate that, because of systematic overlaps of motor and nonmotor asymmetries, LRP waveforms derived by the double subtraction method cannot always be interpreted unequivocally in terms of response activation. Such confounds can be detected when LRP waveforms are compared with difference waveforms obtained by the double subtraction method from ERPs elicited at other lateral scalp sites.     

Localizing practice effects in dual-task performance

Practice effects on dual-task processing are of interest in current research because they may reveal the scope and limits of parallel task processing. Here we used onsets of the lateralized readiness potential (LRP), a time marker for the termination of response selection, to assess processing changes after five consecutive dual-task sessions with three stimulus onset asynchronies (SOAs) and priority on Task 1. Practice reduced reaction times in both tasks and the interference between tasks. As indicated by the LRP, the reduction of dual-task costs can be explained most parsimoniously by a shortening of the temporal demands of central bottleneck stages, without assuming parallel processing. However, the LRP also revealed a hitherto unreported early activation over the parietal scalp after practice in the short SOA condition, possibly indicating the isolation of stimulus–response translation from other central processing stages. In addition, further evidence was obtained from the LRP for a late motoric bottleneck, which is robust against practice.     

Time pressure effects on information processing in overlapping tasks: evidence from the lateralized readiness potential

Information processing is impaired when two tasks are performed concurrently. The interference between the tasks is commonly attributed to structural bottlenecks or strategic scheduling of information processing. The present experiment investigated the effects of time pressure for the second of two responses on information processing in overlapping tasks by recording the lateralized readiness potential (LRP). Time pressure shortened the latency of the second response by diminishing the time devoted to motoric processing. In addition, task interference decreased under time pressure, which is probably due to the relatively early availability of the central bottleneck stage rather than to increased overlap of central stages. The LRP also provided direct evidence for an additional bottleneck following response selection, possibly due to supramodal refractoriness of response initiation.     

Sequential effects of foreperiod duration and conditional probability of the signal in a choice reaction time task

The aim of the present study was to determine whether the negative relationship usually found between reaction time and foreperiod duration in the variable foreperiod paradigm is entirely due to sequential foreperiod effects. It has been shown that when a particular foreperiod has been preceded by a longer one on the previous trial, reaction time is longer than when the preceding foreperiod was equal or shorter. This may be sufficient to explain the increase in reaction time observed for short foreperiods in variable foreperiod conditions.The present results show that, when sequential effects were controlled by the elimination of all trials where the foreperiod was shorter than the preceding one, the negative slope of the reaction time-foreperiod function diminished but did not disappear. The results suggest an interpretation of the role of conditional probability of stimulus arrival in terms of variation in the tendency to reprepare when the moment initially chosen for preparation appears to fall short of the moment at which the stimulus is actually presented.     

Localizing practice effects in dual-task performance

Practice effects on dual-task processing are of interest in current research because they may reveal the scope and limits of parallel task processing. Here we used onsets of the lateralized readiness potential (LRP), a time marker for the termination of response selection, to assess processing changes after five consecutive dual-task sessions with three stimulus onset asynchronies (SOAs) and priority on Task 1. Practice reduced reaction times in both tasks and the interference between tasks. As indicated by the LRP, the reduction of dual-task costs can be explained most parsimoniously by a shortening of the temporal demands of central bottleneck stages, without assuming parallel processing. However, the LRP also revealed a hitherto unreported early activation over the parietal scalp after practice in the short SOA condition, possibly indicating the isolation of stimulus-response translation from other central processing stages. In addition, further evidence was obtained from the LRP for a late motoric bottleneck, which is robust against practice.     

Implicit and explicit learning of event sequences: evidence for distinct coding of perceptual and motor representations

Event-related brain potentials (ERPs) of 21 subjects were recorded in a choice reaction time task with a repeating eight-element long stimulus sequence. The regular event sequence was sometimes interrupted by 'perceptual' or by 'motor deviants' which both replaced an expected stimulus but either preserved or violated the sequence of motor responses. Response times confirmed that all subjects had acquired some knowledge of the sequential dependencies. By means of a post-experimental free recall and recognition test, subjects were classified as having either explicit or implicit knowledge of the event sequence. The ERPs showed different effects for different types of stimuli and the two groups. In the group of explicit learners, a larger N200 component was evoked by both types of deviants and a larger P300 by motor deviants only. In the group of implicit learners these 'perceptual components' remained unaffected. In contrast, in both groups of subjects the lateralized readiness potential (LRP) which accompanied motor deviants revealed a partial activation of the to be expected but incorrect response, i.e. motor learning. These results suggest that explicit learners acquire knowledge about both, stimulus and response dependencies while implicit learners acquire knowledge about response dependencies only.     

Differences in the transmission of sensory input into motor output between introverts and extraverts: Behavioral and psychophysiological analyses

The present study was designed to investigate extraversion-related individual differences in the speed of transmission of sensory input into motor output. In a sample of 16 introverted and 16 extraverted female volunteers, event-related potentials, lateralized readiness potentials (LRPs), and electromyogram (EMG) were recorded as participants performed a visual choice reaction time task. As additional behavioral indicators of performance, measures of reaction time (RT) and response dynamics were obtained. Although extraversion-related differences were found neither for behavioral measures nor for the N1 and P3 components of the evoked potential, introverts showed a reliably shorter latency in stimulus-locked LRP than extraverts. This latter finding supports the notion of faster stimulus analysis in introverts compared to extraverts. Furthermore, there was no indication of extraversion-related individual differences in speed of response organization and response execution as indicated by response-locked LRP and EMG latencies, respectively. However, a significantly higher EMG amplitude observed with introverts pointed to a less accurately adjusted motor output system of introverts compared to extraverts.     

Locus of the intensity effect in simple reaction time tasks

Evidence is still inconclusive regarding the locus of the stimulus intensity effect on information processing in reaction tasks. Miller, Ulrich, and Rinkenauer (1999) addressed this question by assessing the intensity effect on stimulus- and response-locked lateralized readiness potentials (LRPs) as indices of the sensory and motor parts of reaction time (RT). In the case of visual stimuli, they observed that application of brighter stimuli resulted in a shortening of RT and stimulus-locked LRP (S-LRP), but not of response-locked LRP (R-LRP). The results for auditory stimuli, however, were unclear. In spite of a clear RT reduction due to increased loudness, neither S-LRP nor R-LRP onset was affected. A reason for this failure might have been a relatively small range of intensity variation and the type of task. To check for this possibility, we performed three experiments in which broader ranges of stimulus intensities and simple, rather than choice, response tasks were used. Although the intensity effect on the R-LRP was negligible, S-LRP followed RT changes, irrespective of stimulus modality. These findings support the conclusion that stimulus intensity exerts its effect before the start of motoric processes. Finally, S-LRP and R-LRP findings are discussed within a broader information-processing perspective to check the validity of the claim that S-LRP and R-LRP can, indeed, be considered as pure estimates of the duration of sensory and motor processes.     

Individual differences in the effect of smoking on frontal-central distribution of the CNV: Some observations on smokers' control of attentional behaviour

A previous investigation of individual differences in cortical activation during smoking reported differential development of vertex CNV ‘O’ and ‘E’ wave components in introverted and extraverted smokers. In the present paper the frontal CNV recorded from 12 extraverted and 12 introverted smokers was analysed under simple and choice foreperiod conditions during sham and real smoking. Smokers were matched for age, sex and neuroticism. Analysis of variance revealed significant group by smoking session effects for the later ‘E’ wave component but not for the early ‘O’ wave component. ‘O’ wave negativity though more prominent in frontal regions particularly in extraverts tended to be more affected by foreperiod conditions than smoking sessions. In general smoking produced an increase in central negativity in extraverts, and a decrease in parietal positivity in introverts. These results challenge the stimulus-related/response-related separation of smoking effects made previously to account for early and late CNV component differences. It is suggested that a distinction of CNV components in terms of input (sensory) and output (motor) aspects may anyway be inappropriate.An attempt is made to relate CNV negativity/positivity topography differences to a motor model of attentional strategies differentially deployed during smoking. Extraverted smoker strategies may aim to relieve boredom, enhance readiness to act and so increase central negativity. Introverts may smoke to inhibit distraction, maintain a complex attentional set, and so these affect parietal positivity.It is further suggested that the pharmacological effects of nicotine are those of a generalized mild stressor which supplement the motor aspects of smoking in inducing more motivated performance. Some further predictions concerning the effect of smoking on cortical activity are discussed.     

Differential dynamics of spatial and non-spatial stimulus-response compatibility effects: a dual task LRP study

Choice reaction times are shorter when stimulus and response features are compatible rather than incompatible. Recent studies revealed that spatial compatibility effects in Simon tasks are strongly attenuated when there is temporal overlap with a different high-priority task. In contrast, non-spatial variants of the Simon task appear to be unaffected by task overlap. The present study used the lateralized readiness potential (LRP) within a dual task design to elucidate the dynamics underlying these differential effects for a color and a spatial variant of the Simon task. In the color version there was no sign of early response priming by irrelevant stimulus features in the LRP. The color compatibility effect was independent of task overlap and reflected in the LRP onset latency. In contrast, in the spatial version, priming by irrelevant stimulus location showed up and was mirrored by early LRP activation. Response priming and the corresponding Simon effect, however, were present only in case of little temporal overlap with the primary task. The absence of spatial compatibility effects at strong temporal overlap suggests that response conflicts due to stimulus-related priming depend on the availability of processing resources.     

Identification of sensorimotor components accounting for individual variability in Zahlen–Verbindungs-Test (ZVT) performance

The Zahlen–Verbindungs-Test (ZVT) represents a highly feasible measure of information-processing speed that correlates quite highly with standard psychometric tests of intelligence. The present study was designed to identify specific stages of the sensorimotor processing system that may account for individual differences in overall variability of ZVT performance. For this purpose, ZVT, reaction time (RT), lateralized readiness potential (LRP), and electromyogram (EMG) measures were obtained in 48 female participants. While faster RT, smaller intraindividual variability in RT, shorter response-locked LRP and EMG latencies were associated with superior ZVT performance, speed of stimulus analysis, as reflected by stimulus-locked LRP latency, was unrelated to ZVT performance. Additional commonality analyses suggested a functional relationship between ZVT performance and the time course of central aspects of response organization rather than the time required for execution of the overt motor response. These findings provide converging evidence for the general notion of an association between speed of motor processing and intelligence.     

单侧化准备电位的含义和应用

单侧化准备电位（Lateralized readiness potential, LRP）是指在随意运动中,反应效应器方位所对应的对侧大脑皮层出现的准备电位。LRP分析的关键是确定启动时间点。LRP可以揭示刺激-反应不同阶段的认知加工时间特性。可以从反应准备的抽象性或具体性以及大脑控制运动输出的“中枢”机制或“外周”机制这两个思路去验证LRP。LRP在阈下知觉和内隐学习、运动准备和反应执行、西蒙效应等方面的认知心理学研究以及新兴的脑-机界面工程心理学研究得到了广泛的应用,但LRP的应用存在着某些限制因素,如：脑电干扰、测量的低信噪比和其本身对反应效应器的要求等     

Effects of Response Probability on Response Force in Simple RT

Response force (RF) was measured in a simple reaction time (RT) experiment varying response uncertainty by cuing the probability of the response on each trial. In all cases, RF decreased as response probability increased. The dependence of RF on response probability was insensitive to foreperiod length and to the use of loud auditory response signals, although the dependence of RT on response probability was sensitive to both of these manipulations. In combination with previous findings, these results provide evidence that RT and RF can be dissociated. We describe an extension of Naatanen's readiness model that can account for the effects of response probability on RF and RT. According to this model, the distance between motor activation and a threshold for action is relatively large when subjects are unprepared, and a large increment is needed to exceed this threshold, resulting in slow but foreceful responses. A possible neurophysiological implementation of this model is suggested.     

The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies

An experiment was conducted to relate individual components of the event-related brain potential to specific stages of information processing in a two-choice reaction time (RT) task in a group of undergraduate students. Specifically, the latency of the P300 component and the lateralized readiness potential (LRP) were studied as a function of variations in stimulus degradation and response complexity. It was hypothesized that degrading the stimulus would delay the P300 and LRP to the same extent as RT, and that increasing response complexity would affect RT but not P300 latency. The extant literature did not permit any hypothesis regarding the effect of response complexity on LRP latency. The two task variables were found to have additive effects on RT. As predicted, variations in stimulus degradation influenced the latencies of both components, whereas alterations in response complexity had no effect on P300 latency. A significant new finding was that the onset latency of the LRP remained unchanged across levels of response complexity. The overall pattern of results supports the notion of temporal selectivity of stage manipulations that is derived from discrete stage models of human information processing. Furthermore, these results refine the functional interpretation of the LRP by indicating that within the conceptual framework of a stage model the processes this component indexes succeed the start of response choice but precede the start of motor programming.     

Partial response activation to masked primes is not dependent on response readiness

Masked primes presented foveally prior to a target trigger an initial partial activation of their corresponding response, followed by an inhibition of the same response. The latter phase results in performance costs on compatible trials and performance benefits on incompatible trials relative to neutral trials (negative compatibility effect). The present study investigated whether this activation-follow-by-inhibition process depends on the overall or specific state of response readiness. In two masked priming experiments, response readiness was manipulated by varying the relative frequency of Go-trials in a Go/NoGo task (Exp. 1) and the relative frequency of left- and right-hand responses in a 2-alternative choice reaction time task (Exp. 2). In both experiments, mean reaction times were longer for infrequent responses than for frequent responses. However, negative compatibility effects were not affected by response frequency. This result indicates that neither the general ability of masked primes to elicit a partial motor activation nor the specific time course of this process is dependent on response readiness. It is concluded that response readiness affects the execution of an overt response rather than the initial activation of this response.     

Do's and don'ts with lateralized event-related brain potentials

K. Wiegand and E. Wascher (2005) used the lateralized readiness potential (LRP) to investigate the mechanisms underlying spatial stimulus-response (S-R) correspondence. The authors compared spatial S-R correspondence effects obtained with horizontal and vertical S-R arrangements. In some relevant previous investigations on spatial S-R correspondence with the LRP, researchers preferred to use the vertical S-R layout to circumvent methodological issues related to the LRP and horizontal S-R layouts. K. Wiegand and E. Wascher (2005) do not address these complications, and they make comparisons between electroencephalographic (EEG) data collected with horizontal and vertical S-R arrangements that do not take into account the limitations inherent to the LRP derivation. This methodological weakness renders unsound the neurophysiological support for their views on the nature of spatial S-R compatibility effects. In this article, the author discusses the limitations and possibilities of lateralized event-related potentials (ERPs) in the investigation of spatial S-R correspondence effects.     

Inhibition of return from stimulus to response

In a standard inhibition-of-return (IOR) paradigm using a manual key-press response, we examined the effect of IOR both on the amplitude of early sensory event-related brain potential (ERP) components and on the motor-related lateralized readiness potential (LRP). IOR was associated with a delay of premotor processes (target-locked LRP latency) and reduced sensory ERP activity. No effect of IOR was found on motor processes (response-locked LRP latency). Thus, IOR must arise at least in part from changes in perceptual processes, and, at least when measured with manual key presses, IOR does not arise from inhibition of motor processes. These results are consistent with the results of attention-orienting studies and provide support for an inhibition-of-attention explanation for IOR.     

Extroversion-related differences in speed of premotor and motor processing as revealed by lateralized readiness potentials

To further elucidate extroversion-related differences in speed of sensorimotor processing, the authors obtained behavioral and psychophysiological measures as participants (16 introverts and 16 extroverts) performed a visual go/no-go task. Although no extroversion-related differences in reaction time emerged, introverts showed faster premotor processing but slower central and peripheral motor processing--as indicated by latencies of the lateralized readiness potential (LRP) and electromyographic (EMG) data, respectively--than extroverts did. Additional regression analyses revealed that stimulus-locked LRP latency, response-locked LRP latency, and Nl EMG amplitude accounted for 40% of overall variability in individual extroversion scores. On the basis of the present results, the authors introduce a compensation hypothesis that accounts for the common failure of researchers to demonstrate extroversion-related differences in reaction time. The present results challenge J. Brebner and C. Cooper's (1985) model of extroversion in which stimulus analysis is not slower in introverts than in extroverts. However, the present findings support the assumption of faster motor processing in extroverts.