Stimulus-response Pairs Research Articles

Exploring handedness asymmetries in the Simon effect.

Spatially corresponding stimulus-response pairings usually produce shorter reaction times (RTs) than do non-corresponding pairings, even when the spatial dimension of the stimulus is irrelevant to the task. This "Simon effect" for visual stimuli and manual responses is often larger for the stimulus location on the side to which the person's dominant hand is operating. The present study aimed at replicating and examining the nature of this asymmetry. To determine whether the Simon effect asymmetry is a function of the hand distinction or of conceptual spatial codes, performance with left and right manual key-presses was compared to that with vocal responses "left" and "right." Whether the asymmetric Simon effect pattern is restricted to spatial stimuli was tested by comparing effects obtained with left and right located squares to those found with the centered words Left and Right. The asymmetry was only replicated for the spatial stimulus-manual response Simon task, for which a second experiment showed similar results when the hands and response box were not visible during task performance. The analysis revealed a general dominant-hand RT advantage that similarly adds to both corresponding and non-corresponding trials and is rather independent from the Simon effect. This advantage yields an apparent asymmetry when the data are analyzed as a function of correspondence for each stimulus location because the corresponding and non-corresponding RTs that are compared come from different hands.

Electrophysiological correlates of motor sequence learning.

BackgroundThe Error-related negativity (ERN) is a component of the event-related brain potentials elicited by error commission. The ERN is thought to reflect cognitive control processes aiming to improve performance. As previous studies showed a modulation of the ERN amplitude throughout the execution of a learning task, this study aims to follow the ERN amplitude changes from early to late learning blocks in relation with concomitant motor sequence learning using a serial reaction time (SRT) task. Twenty-two healthy participants completed a SRT task during which continuous EEG activity was recorded. The SRT task consists of series of stimulus-response pairs and involves motor learning of a repeating sequence. Learning was computed as the difference in mean response time between the last sequence block and the last random blocks that immediately follows it (sequence-specific learning). Event-related potentials were analysed to measure ERN amplitude elicited by error commission.ResultsMean ERN amplitude difference between the first four learning blocks and the last four learning blocks of the SRT task correlated significantly with motor sequence learning as well as with overall response time improvement, such that those participants whose ERN amplitude most increased through learning blocks were also those who exhibited most SRT task improvements. In contrast, neither sequence-specific learning nor overall response time improvement across learning blocks were found to be related to averaged ERN amplitude from all learning blocks.ConclusionFindings from the present study suggest that the ERN amplitude changes from early to late learning blocks occurring over the course of the SRT task, as opposed to the averaged ERN amplitude from all learning blocks, is more closely associated with learning of a motor sequence. These findings propose an improved electrophysiological marker to index change in cognitive control efficiency during motor sequence learning.

To imitate or not: Avoiding imitation involves preparatory inhibition of motor resonance

Stimulus–response compatibility (SRC)—the fact that some stimulus–response pairs are faster than others—is attributed in part to automatic activation of the stimulus–compatible response representation. Cognitive models of SRC propose that automatic response activation can be strategically suppressed if the automatic response is likely to interfere with behavior; in particular, suppression is thought to occur in preparation for incompatible responses and when the required stimulus–response mapping is unknown before stimulus presentation. We test this preparatory suppression hypothesis in the context of imitation, a special form of SRC particularly relevant to human social behavior. Using TMS, we measured muscle-specific corticospinal excitability during action observation (motor resonance) while human participants prepared to perform imitative and counterimitative responses to action videos. Motor resonance was suppressed during preparation to counterimitate and for unknown mappings, compared to preparation to imitate and a baseline measure of motor resonance. These results provide novel neurophysiological evidence that automatic activation of stimulus–compatible responses can be strategically suppressed when the automatic response is likely to interfere with task goals. Insofar as motor resonance measures mirror neuron system activity, these results also suggest that preparatory control of automatic imitative tendencies occurs through modulation of mirror neuron system activity.

Perceptual Sequence Learning Is More Severely Impaired than Motor Sequence Learning in Patients with Chronic Cerebellar Stroke

Patients with cerebellar stroke are impaired in procedural learning. Several different learning mechanisms contribute to procedural learning in healthy individuals. The aim was to compare the relative share of different learning mechanisms in patients and healthy controls. Ten patients with cerebellar stroke and 12 healthy controls practiced a visuomotor serial reaction time task. Learning blocks with high stimulus-response compatibility were exercised repeatedly; in between these, participants performed test blocks with the same or a different (mirror-inverted or unrelated) stimulus sequence and/or the same or a different (mirror-inverted) stimulus-response allocation. This design allowed to measure the impact of motor learning and perceptual learning independently and to separate both mechanisms from the learning of stimulus-response pairs. Analysis of the learning blocks showed that, as expected, both patients and controls improved their performance over time, although patients remained significantly slower. Analysis of the test blocks revealed that controls showed significant motor learning as well as significant visual perceptual learning, whereas cerebellar patients showed only significant motor learning. Healthy participants were able to use perceptual information for procedural learning even when the rule linking stimuli and responses had been changed, whereas patients with cerebellar lesions could not recruit this perception-based mechanism. Therefore, the cerebellum appears involved in the accurate processing of perceptual information independent from prelearned stimulus-response mappings.

Distinct Roles of Three Frontal Cortical Areas in Reward-Guided Behavior

Functional magnetic resonance imaging was used to measure activity in three frontal cortical areas, the lateral orbitofrontal cortex (lOFC), medial orbitofrontal cortex (mOFC)/ventromedial frontal cortex (vmPFC), and anterior cingulate cortex (ACC), when expectations about type of reward, and not just reward presence or absence, could be learned. Two groups of human subjects learned 12 stimulus-response pairings. In one group (Consistent), correct performances of a given pairing were always reinforced with a specific reward outcome, whereas in the other group (Inconsistent), correct performances were reinforced with randomly selected rewards. The mOFC/vmPFC and lOFC were not distinguished by simple differences in relative preference for positive and negative outcomes. Instead lOFC activity reflected updating of reward-related associations specific to reward type; lOFC was active whenever informative outcomes allowed updating of reward-related associations, regardless of whether the outcomes were positive or negative, and the effects were greater when consistent stimulus-outcome and response-outcome mappings were present. A psychophysiological interaction analysis demonstrated changed coupling between lOFC and brain areas for visual object representation, such as perirhinal cortex, and reward-guided learning, such as the amygdala, ventral striatum, and habenula/mediodorsal thalamus. In contrast, mOFC/vmPFC activity reflected expected values of outcomes and occurrence of positive outcomes, regardless of consistency of outcome mappings. The third frontal cortical region, the ACC, reflected the use of reward type information to guide response selection. ACC activity reflected the probability of selecting the correct response, was greater when consistent outcome mappings were present, and was related to individual differences in propensity to select the correct response.

Perceptual recovery of phonetic features in blanked segments of disyllabic words

Spondees, both true disyllabic words and concatenated monosyllabic word pairs, had their middle section replaced by silence that extended from the midpoint of the first to the midpoint of the second vowel; the silence thus included the final consonant(s) of the first and the initial consonant(s) of the second syllable. These stimuli were presented to normal-hearing young listeners instructed to guess both monosyllabic half words. Input and response spondees were orthographically aligned and analyzed as confusion matrices. Articulatory gestures were estimated for each token via the Haskins Laboratories TADA articulatory synthesis. After time alignment, articulatory distances were calculated for each stimulus-response pair. In the blanked middle of the spondee, phoneme-based confusions of place-of-articulation were high (39% accuracy), while gestural distances underlying this feature (location and degree of tongue tip constriction, lip aperture, and velar constriction) were under 10%. These results suggest that acoustic traces of a significant portion of gesture trajectories underlying consonantal place-of-articulation that start before and/or terminate after the silence, are perceived by the listener. An articulatory phonology might thus be more robust to degradation. [Work supported by NSF, AFOSR, and the VA Medical Research.]

Modeling fast stimulus–response association learning along the occipito-parieto-frontal pathway following rule instructions

On the basis of instructions, humans are able to set up associations between sensory and motor areas of the brain separated by several neuronal relays, within a few seconds. This paper proposes a model of fast learning along the dorsal pathway, from primary visual areas to pre-motor cortex. A new synaptic learning rule is proposed where synaptic efficacies converge rapidly toward a specific value determined by the number of active inputs of a neuron, respecting a principle of resource limitation in terms of total synaptic input efficacy available to a neuron. The efficacies are stable with regards to repeated arrival of spikes in a spike train. This rule reproduces the inverse relationship between initial and final synaptic efficacy observed in long-term potentiation (LTP) experiments. Simulations of learning experiments are conducted in a multilayer network of leaky integrate-and-fire (LIF) spiking neuron models. It is proposed that cortical feedback connections convey a top-down learning-enabling signal that guides bottom-up learning in “hidden” neurons that are not directly exposed to input or output activity. Simulations of repeated presentation of the same stimulus–response pair, show that, under conditions of fast learning with probabilistic synaptic transmission, the networks tend to recruit a new sub-network at each presentation to represent the association, rather than re-using a previously trained one. This increasing allocation of neural resources results in progressively shorter execution times, in line with experimentally observed reduction in response time with practice.This article is part of a Special Issue entitled: Neural Coding.

The development of theories of second language acquisition

Second language acquisition (SLA) is a relatively new field of enquiry. Before the late 1960s, educators did write about L2 learning, but very much as an adjunct of language teaching pedagogy, underpinned by behaviourism, the then-dominant learning theory in psychology. In this view, the task facing learners of foreign languages was to rote-learn and practise the grammatical patterns and vocabulary of the language to be learnt, in order to form new ‘habits’, that is to create new stimulus–response pairings which would become stronger with reinforcement. In order for the ‘old habits’ of the L1 not to interfere with this process by being ‘copied’, or transferred, into the L2, researchers embarked on thorough descriptions of pairs of languages to be learnt, in order to identify areas that are different and would thus be difficult.

Study on auditory semantic priming effects in patients with aphasia

Objective To explore the characteristics of semantic priming effects in Chinese words with different association strength in patients with aphasia by auditory stimulation.Method Stimulus-response word pairs with different association strength including strong,moderate,weak,and no association categories were chosen from word association thesaurus as experiment materials.Both patients with aphasia(n=11)and normal subjects (n=16)were requested to finish an auditory lexical decision task for target words.Semantic priming effects were investigated by means of measuring reaction time(RT)and error rate of each word-pair.Results In patients with aphasia and normal subjects,the mean RTs were significantly shorter in strong,moderate and weak association strength words than in no association strength words(patients with aphasia(1270.20±47.70)ms,(1340.50±266.25)ms,(1429.70±317.07)ms vs(1549.00±325.87)ms,P＜0.05 and normal subjects(1140.2±274.48)ms,(1196.50±284.06)ms,(1262.10±274.31)ms vs(1391.20±315.68)ms,P＜0.05).In strong,moderate,and no association strength words,the mean RTs were no significant differences between two groups.In the weak association strength words,mean RTs were significantly longer in patients with aphasia than in normal subjects((1429.70±317.07)ms vs(1262.10±274.31)ms,P＜0.05).In two groups,mean error rates were significantly less in strong,moderate and weak association strength words than in no association strength words(patients with aphasia:7.73±6.07,4.55±7.23,6.82±8.15 vs 14.09±12.41,P＜0.05 and normal subjects:3.44±4.37,2.81±3.64,5.31±5.91 vs 10.94±11.14,P＜0.05).However,in strong association strength words,mean error rates were significantly higher in patients with aphasia than in normal subjects(7.73±6.07 vs 3.44±4.37,P＜0.05).In moderate,weak and no association strength words,there were no significant differences between two groups.Conclusion The patients with aphasia follow gradient of the association strength words like normal subjects and have semantic priming effects in the strong,moderate association strength words. Key words: Association strength; Semantic priming; Aphasia; Reaction time

Using natural stimuli to estimate receptive fields in neurons that employ sparse coding

Event Abstract Back to Event Using natural stimuli to estimate receptive fields in neurons that employ sparse coding Guy Isely1*, Christopher Hillar2 and Friedrich Sommer2 1 University of California at Berkeley, Redwood Center for Theoretical Neuroscience, United States 2 University of California, United States Estimating receptive fields with natural stimuli has become an important approach for analyzing response properties of sensory neurons. It has been noted that natural stimuli contain correlations that have to be accounted for in analyzing receptive field properties. The appropriate correction has been worked out for the linear coding model [4] and there are methods to estimate receptive fields if the assumed coding model contains a pointwise nonlinearity [3]. Here we ask the question how one can estimate receptive fields if the underlying coding process is sparse coding, a model for sensory neurons that has been very successful in explaining the emergence of experimentally observed response properties [1, 2]. To explore this question we perform recording experiments on the sparse coding model, probing its activity with stimulus samples and determining the receptive fields of its neurons from stimulus response pairs. Naive reverse correlation with natural stimulus probes finds receptive fields that are similar in structure to the feed forward connections in the model. However, correcting for the autocorrelations in these probes corrupts that structure with high frequency noise. The linear generative mathematics inherent in the sparse coding model can explain why naive reverse correlation without the correction for stimulus autocorrelations provides a better estimate of the receptive field structure of sparse coding neurons. In particular, a mathematical analysis of sparse coding networks suggests a correction for the autocorrelations in the responses of their neurons rather than a correction for stimulus autocorrelations. Since these response autocorrelations are relatively small for a sparse coding network sampled with a sufficiently large natural stimulus ensemble, uncorrected naive reverse correlation with natural stimulus probes is a good approximation. More generally, an implication of our analysis is that the best linear predictor of a neuron’s firing rate is potentially not the best estimate of the spatial structure of connections that drive its stimulus response. Thus, surprisingly, under the assumption that the neurons one records from are performing sparse coding or similar computations involving later inhibition, naive reverse correlation may provide a better estimate of the structure their receptive fields than seemingly more rigorous techniques that correct for stimulus autocorrelations.

Distinguishing between the partial-mapping preparation hypothesis and the failure-to-engage hypothesis of residual switch costs.

Lien, Ruthruff, Remington, & Johnston (2005) reported residual switch cost differences between stimulus-response (S-R) pairs and proposed the partial-mapping preparation (PMP) hypothesis, which states that advance preparation will typically be limited to a subset of S-R pairs because of structural capacity limitations, to account for these differences. Alternatively, the failure-to-engage (FTE) hypothesis does not allow for differences in probability of advance preparation between S-R pairs within a set; it accounts for residual switch cost differences by assuming that benefits of advance preparation may differ between S-R pairs. Three Experiments were designed to test between these hypotheses. No capacity limitations of the type assumed by the PMP hypothesis were found for many participants in Experiment 1. In Experiments 2 and 3, no evidence was found for the dependency of residual switch cost differences between S-R pairs on response-stimulus interval that is predicted by the PMP hypothesis. Mixture-model analysis of reaction times distributions in Experiment 3 provided strong support for the FTE hypothesis over the PMP hypothesis. Simulation studies with a computational implementation of the FTE hypothesis showed that it is able to account in great detail for the results of the present study. Together, these results provide strong evidence against the PMP hypothesis and support the FTE hypothesis that advance preparation probabilistically fails or succeeds at the level of the task set.

Influence of stimulus–response assignment on the joint-action correspondence effect

Sebanz et al. (Cognition 88:B11-B21, 2003) have shown that spatial correspondence effects are observed even when the two-choice reaction time task is distributed between two people, such that each person is assigned only one of two possible stimulus-response (S-R) pairings. The effect is similar to when one person is assigned and responds to both S-R pairings. These results have been taken to suggest that two people performing a complementary task co-represent each other's response alternatives. In our experiment, we examined performance when paired participants responded to the same S-R alternative. We reasoned that co-representation would be of little advantage as the task alternatives would be the same for both participants. Correspondence effects were absent when paired participants responded to the same S-R alternative but emerged when they responded to different alternatives.

Adaptation of the precision grip orientation to a visual-haptic mismatch

Using a sequential-exposure approach, we examined sensorimotor adaptation of precision grip orientation to a visuo-haptic mismatch. Subjects (n = 41) were asked to grasp with thumb and index finger mirror-viewed objects. They could not see their hand due to the mirror, but they could feel an object located behind the mirror in the same place as the viewed object. When a -15 degrees orientation mismatch between viewed and felt object was introduced, subjects adapted to it by gradually modifying the orientation of their finger opposition axis. When the visuo-haptic mismatch further changed to -30 degrees or to +15 degrees , subjects continued to perform according to their pre-established adaptive state, and gradually modified it until it became adequate for the new mismatch. This outcome supports the existence of a continuously acting mechanism for grasping adaptation, similar to that previously described for pointing and tracking adaptation. Precision grip adaptation generalized to unpracticed object orientations, which suggests that adaptation was based on a sensorimotor recalibration rather than the learning of specific stimulus-response pairs. Transfer to pointing movements was found only when similarity to the grasp adaptation task was high.

Determinants of the benefit for consistent stimulus-response mappings in dual-task performance of four-choice tasks

Reaction times are shorter when the stimulus-response mappings for pairs of three-choice tasks are consistent (both corresponding or both mirrored) than when they are inconsistent. The benefit for consistent mirrored mappings is evident at the side positions for each task, for which the responses are crossed, but not at the middle position, for which the response is corresponding. In the present study, we report experiments in which we tested implications of an emergent mapping-choice account of the consistency benefit using pairs of four-choice tasks. This procedure allows crossed responses for all positions when the mapping is mirrored and use of mixed mappings for which one pair of stimuli and responses within a task has a corresponding assignment and the other a crossed assignment. Results showed that when a pure corresponding or pure mirrored mapping was used, there was a consistency benefit for both the middle and side positions. However, when the mixed mapping was introduced, the consistency benefit for that mapping depended on the overall complexity of the set of individual stimulus-response pairings for the combined tasks. A mapping choice between Tasks 1 and 2 is only one of several emergent processes that contribute to response-selection efficiency in dual-task contexts.

Temporal characteristics of semantic perseverations induced by blocked-cyclic picture naming

When unimpaired participants name pictures quickly, they produce many perseverations that bear a semantic relation to the target, especially when the pictures are blocked by category. Evidence suggests that the temporal properties of these “semantic perseverations” may differ from typical lexical perseverations in aphasia. To explore this, we studied semantic perseverations generated by participants with aphasia on a naming task with semantic blocking [Schnur, T. T., Schwartz, M. F., Brecher, A., & Hodgson, C. (2006). Semantic interference during blocked-cyclic naming: Evidence from aphasia. Journal of Memory and Language, 54, 199–227]. The properties of these perseverations were investigated by analyzing how often they occurred at each lag (distance from prior occurrence) and how time (response-stimulus interval) influenced the lag function. Chance data sets were created by re-shuffling stimulus-response pairs in a manner that preserved unique features of the blocking design. We found that the semantic blocking manipulation did not eliminate the expected bias for short-lag perseverations (recency bias). However, immediate (lag 1) perseverations were not invariably the most frequent, which hints at a source of inconsistency within and across studies. Importantly, there was not a reliable difference between the lag functions for perseverations generated with a 5 s, compared to 1 s, response-stimulus interval. The combination of recency bias and insensitivity to elapsed time indicates that the perseveratory impetus in a named response does not passively decay with time but rather is diminished by interference from related trials. We offer an incremental learning account of these findings.

Conflict adaptation depends on task structure.

The dependence of the Simon effect on the correspondence of the previous trial can be explained by the conflict-monitoring theory, which holds that a control system adjusts automatic activation from irrelevant stimulus information (conflict adaptation) on the basis of the congruency of the previous trial. The authors report on 4 experiments showing that conflict adaptation is mediated by task structure as well as previous congruency. Experiment 1 showed that for 2 completely segregated sets of stimulus-response pairs there was no conflict adaptation across sets. However, if the stimulus sets overlapped for 2 separate response sets, conflict adaptation could be observed across the response sets. Experiment 2 showed that this effect was not due to the use of stimulus-response sets lateralized to 1 hemisphere each. Experiment 3 showed that if response sets are common for 2 separate stimulus sets, then conflict adaptation can again be observed across sets. Finally, Experiment 4 showed local control effects in the absence of confounding feature-overlap effects. These results indicate that deployment of control as evidenced by conflict adaptation reflects task structure.

Learning-related changes in brain activity following errors and performance feedback in schizophrenia

In previous studies of self-monitoring in schizophrenia, patients have exhibited reductions in the amplitude of the error-related negativity (ERN), a component of the event-related brain potential (ERP) elicited most prominently immediately following the execution of incorrect responses. In the current study, we examined the ERN and a related component, the feedback negativity (FBN) in 26 schizophrenia outpatients and 27 psychiatrically healthy comparison subjects during a probabilistic learning task in which participants could learn stimulus–response pairs by attending to feedback indicating response accuracy. The validity of the feedback varied in three conditions. In one condition, accuracy feedback was entirely consistent (i.e., a left response to one of the stimuli in this condition was always correct and a right response was always incorrect). In the second condition, feedback was valid on only 80% of the trials, and in the third condition, accuracy feedback was random. Changes in ERP amplitudes accompanying learning of stimulus–response pairs were examined. Schizophrenia patients exhibited reduced ERN amplitude compared to healthy subjects in all conditions. This finding extends the previously reported impairment to include disruption of self-monitoring on a task in which participants learn stimulus–response mappings by trial and error, rather than being told the mappings explicitly. Schizophrenia patients also exhibited reduced FBN amplitude compared to healthy subjects in the 100% condition during early trials when the feedback was essential for accurate performance. These findings suggest that reward-related brain activity is weakened in schizophrenia, perhaps reflecting diminished sensitivity to whether ongoing events are better or worse than expected.

Orthographic Influences on Phoneme Deletion Response Times

The aim of this paper is to provide further evidence that orthography plays a central role in phonemic awareness, by demonstrating an orthographic congruency effect in phoneme deletion. In four initial phoneme deletion experiments, adult participants produced the correct response more slowly with orthographically mismatched stimulus-response pairs (e.g., worth-earth) than with matched pairs (e.g., wage-age). This orthographic effect occurred with or without specific instructions to ignore spelling and when stimuli were presented with or without the to-be-deleted sound. In a final experiment, participants made more errors on complex than simple onset items, but there was no interaction with orthographic mismatch. The repeated observation of this robust orthographic effect suggests that participants are at least aware of orthography during phonemic awareness tasks, and it supports the view that phonemic awareness is directly subserved by orthography.

Dissociating uncertainty responses and reinforcement signals in the comparative study of uncertainty monitoring.

Although researchers are exploring animals' capacity for monitoring their states of uncertainty, the use of some paradigms allows the criticism that animals map avoidance responses to error-causing stimuli not because of uncertainty monitored but because of feedback signals and stimulus aversion. The authors addressed this criticism with an uncertainty-monitoring task in which participants completed blocks of trials with feedback deferred so that they could not associate reinforcement signals to particular stimuli or stimulus-response pairs. Humans and 1 of 2 monkeys were able to make cognitive, decisional uncertainty responses that were independent of feedback or reinforcement history within a task. This finding unifies the comparative literature on uncertainty monitoring. The dissociation of performance from reinforcement has theoretical implications, and the deferred-feedback technique has many applications.

Dissociation between medial temporal lobe and basal ganglia memory systems in schizophrenia

The purpose of this study was to investigate basal ganglia (BG) and medial temporal lobe (MTL) dependent learning in patients with schizophrenia. Acquired equivalence is a phenomenon in which prior training to treat two stimuli as equivalent (if two stimuli are associated with the same response) increases generalization between them. The learning of stimulus–response pairs is related to the BG, whereas the MTL system participates in stimulus generalization. Forty-three patients with DSM-IV schizophrenia and 28 matched healthy controls participated. Volunteers received the Rutgers acquired equivalence task (face-fish task) by Myers et al. (2003) [Myers, C.E., Shohamy, D., Gluck, M.A. et al., 2003. Dissociating hippocampal versus basal ganglia contributions to learning and transfer. J. Cogn. Neurosci. 15, 185-193.], the California Verbal Learning Test (CVLT), and the n-back working memory test. The Rutgers acquired equivalence task investigates BG-dependent processes (stimulus–response learning) and MTL-dependent processes (stimulus generalization) with a single test. Results revealed that patients with schizophrenia showed a selective deficit on stimulus generalization, whereas stimulus–response learning was spared. The stimulus generalization deficit correlated with the CVLT performance (total scores from trials 1–5 and long-delay recall), but not with the n-back test performance. The number of errors during stimulus–response learning correlated with the daily chlorpromazine-equivalent dose of antipsychotics. In conclusion, this is the first study to show that patients with schizophrenia exhibit deficits during MTL-dependent learning, but not during BG-dependent learning within a single task. High-dose first generation antipsychotics may disrupt BG-dependent learning by blocking dopaminergic neurotransmission in the nigro-stiratal system.