Inhibition and Interference in Selective Attention: Some Tests of a Neural Network Model

Individual Differences in Working Memory Capacity Modulate Electrophysiological Correlates of Semantic Negative Priming From Single Words

In the present study, event-related potentials (ERPs) were registered during a semantic negative priming (NP) task in participants with higher and lower working memory capacity (WMC). On each trial participants had to actively ignore a briefly presented single prime word, which was followed either immediately or after a delay by a mask. Thereafter, either a semantically related or an unrelated target word was presented, to which participants made a semantic categorization judgment. The ignored prime produced a behavioral semantic NP in delayed (but not in immediate) masking trials, and only for participants with a higher-WMC. Both masking type and WMC also modulated ERP priming effects. When the ignored prime was immediately followed by a mask (which impeded its conscious identification) a reliable N400 modulation was found irrespective of participants' WMC. However, when the mask onset following the prime was delayed (thus allowing its conscious identification), an attenuation of a late positive ERP (LPC) was observed in related compared to unrelated trials, but only in the higher-WMC group showing reliable behavioral NP. The present findings demonstrate for the first time that individual differences in WMC modulate both behavioral measures and electrophysiological correlates of semantic NP.

The level of representation of irrelevant stimuli-Distractor-response 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.

Brightness versus darkness: The influence of stimulus intensity on the distractor-response binding effect

The intensity of a stimulus has been found to have a distinct impact upon response processes (e.g., response speed, response force, & response selection). For instance, reaction times are faster to bright than to dim stimuli (e.g., Kohfeld, 1971). In the present study, we investigated the possible influence of stimulus intensity on binding processes. According to binding theories, stimulus and response features are integrated together in short-lived memory traces, called event files (Hommel, 1998). Any re-encounter with one of these integrated features leads to the automatic retrieval of the previously constructed event file and thus of the response. Thereby bindings between stimuli (relevant and irrelevant) and responses have a direct impact on behavior. In the present experiment, we presented distractors with increasing stimulus intensity and found that intensity did exert an influence on binding processes. However, our results suggest that distractor intensity per se has no direct influence on the binding effect (the more intense a distractor is, the larger the binding effect), but that distractor intensity has an indirect effect on binding via grouping due to similarity between target and distractor intensity.

Semantic Negative Priming From an Ignored Single-Prime Depends Critically on Prime-Mask Inter-Stimulus Interval and Working Memory Capacity

The aim of this study is to examine the link between working memory capacity and the ability to exert cognitive control. Here, participants with either high or low working memory capacity (WMC) performed a semantic negative priming (NP) task as a measure of cognitive control. They were required to ignore a single prime word followed by a pattern mask appearing immediately or after a delay. The prime could be semantically related or unrelated to an upcoming target word where a forced-choice categorization was required. Each type of mask (immediate vs. delayed) appeared randomly from trial to trial. Results demonstrated that, when the ignored prime was immediately followed by the mask, neither of the groups (high or low WMC) showed reliable NP. In clear contrast, when the mask onset was delayed responses latencies were reliably slower for semantically related trials than for unrelated trials (semantic NP), but only for the high WMC group. The present results clearly demonstrate that semantic NP from single ignored primes depends on both the masking pattern that follows the prime (immediate vs. delayed mask), and on working memory capacity.

Separating after-effects of target and distractor processing in the tactile sensory modality

The present study investigated the cognitive mechanisms underlying aftereffects of tactile target and distractor processing. In our experiment, participants selected tactile target stimuli against simultaneously presented tactile distractor stimuli in prime-probe sequences. Tactile distractors in each prime/probe trial were either response incompatible (i.e., interfering at the response level) or response neutral (i.e., noninterfering at the response level), manipulated between participants. Furthermore, distractor relation (repetition vs. change) and response relation (repetition vs. change) across prime-probe sequences were orthogonally varied within participants. Thus, independent estimates of distractor repetition main effects (that are attributable to distractor-specific prime processing and have previously been interpreted in terms of inhibition or episodic retrieval processes) and the modulation of distractor repetition effects due to response relation (that is target specific and can only be explained in terms of event-file retrieval) were assessed (see Giesen, Frings, & Rothermund, Memory & Cognition, 40, 373-387, 2012). Replicating previous studies with visual stimuli, simple distractor repetition effects were stronger for response-incompatible compared with response-neutral tactile distractors. In contrast, event-file retrieval as reflected in distractor-response binding retrieval effects was not modulated by whether the distractors were response incompatible or response neutral. Together, these findings highlight that in tactile tasks, prime-distractor and prime-target processing both hold the potential to cause aftereffects during probe performance.

Response Inhibition as a Function of Movement Complexity and Movement Type Selection

This study aims to determine whether response inhibition shows the same degree of effectiveness for two sources of motor complexity: (1) Movement complexity, which is measured through two actions with different motor requirements (simple lifting action vs. complex reaching action), and (2) Movement type selection, which is measured in movements performed separately (no active-movement type selection) vs. selectively (active-movement type selection). Activation–suppression model was tested in three experiments to measure activation of the preponderant responses and subsequent suppression in a Simon task. More errors and higher magnitude of congruence effect (which reflects greater effectiveness of response suppression) were expected for more difficult motor conditions. Reaction time, movement time, kinematic errors, and movement errors were recorded. Results of Experiment 1, in which movement type selection was not active, showed that both movements did not differ in their activation and suppression, as they presented similar kinematic error rates and Simon effects. Experiment 2, in which movement type selection was active, resulted in a higher kinematic error rate and higher magnitude of Simon effect in lifting. These results were confirmed in Experiment 3, in which participants performed all experimental motor complexity conditions. Finally, Experiment 4 showed that responses with similar movement complexity did not differ in their activation and suppression, even when movement type selection was active. Thus, the present study provides evidence on the varying effectiveness of response inhibition as a function of movement complexity, but only in demanding situations in which movement type selection is active. These results can be attributed to a top-down strategy to minimize error for actions most prone to develop kinematic error.

Distractor-based retrieval in action control: the influence of encoding specificity

If a target stimulus is presented together with a response irrelevant distractor stimulus, both stimuli can be encoded together with the response in an event file [see Hommel (Trends Cogn Sci 8:494-500, 2004)]. The repetition of the distractor can retrieve the encoded response. This kind of distractor-based retrieval is an important mechanism in action control. In the present experiment, we investigate whether and how distractor-based retrieval of event files is influenced by encoding specificity-a retrieval principle that has been suggested to affect retrieval in short-term and long-term memory. Using a prime-probe design, the number of identical distractors on each display was varied. The results showed that the distractor-based retrieval process is modulated by encoding specificity, in that only high (low) number of distractors retrieves former event files with high (low) number of distractors. Taken together, distractor-based retrieval in action control follows principles known from short-term memory and long-term memory retrieval.

Inhibitory Tagging of Stimulus Properties in Inhibition of Return: Effects on Semantic Priming and Flanker Interference

In this study we examine the level at which inhibition of return (IOR) affects the processing of visual stimuli. Experiments 1 and 2 examined the effect of IOR on semantic priming. Experiments 3 and 4 examined the effect on flanker interference. In both cases IOR could reverse the standard effects. We suggest that when attention is drawn away from a location, there is temporary inhibitory tagging of stimuli that are presented there. This tagging extends to the semantic and response-relevant properties of stimuli, helping to bias attention away from old and towards new events. Due to inhibitory tagging, responses to new targets can be slowed down when targets are semantically related (Experiments 1 and 2) or require the same response (Experiments 3 and 4) as inhibited primes.

Identity and semantic negative priming in rapid serial visual presentation streams

In selective attention tasks, the efficiency of processing concurrently presented target and distractor stimuli in a given display is often influenced by the relationship these stimuli have with those in the previous display. When a to-be-attended target on a current trial (the probe trial) matches the ignored, non-target distractor on a previous trial (the prime trial), a response to the target is typically delayed compared with when the two stimuli are not associated. This negative priming (NP) phenomenon has been observed in numerous studies with traditional NP tasks presenting the target and distractor simultaneously in both the prime and probe trial couplets. Here, however, in four experiments using a mixture of stimulus types (letters, digits, English number words, and logographic Chinese number words), target and distractor stimuli were temporally separated in two rapid serial visual presentation (RSVP) streams instead of concurrently presented. The findings provide a conceptual replication and substantial extension of a recent study by Wong (Plos One, 7, e37023, 2012), and suggest that active suppression of irrelevant distracting information is a more ubiquitous form of cognitive control than previously thought.

Target-distractor synchrony affects performance in a novel motor task for studying action selection

The study of action selection in humans can present challenges of task design since our actions are usually defined by many degrees of freedom and therefore occupy a large action-space. While saccadic eye-movement offers a more constrained paradigm for investigating action selection, the study of reach-and-grasp in upper limbs has often been defined by more complex scenarios, not easily interpretable in terms of such selection. Here we present a novel motor behaviour task which addresses this by limiting the action space to a single degree of freedom in which subjects have to track (using a stylus) a vertical coloured target line displayed on a tablet computer, whilst ignoring a similarly oriented distractor line in a different colour. We ran this task with 55 subjects and showed that, in agreement with previous studies, the presence of the distractor generally increases the movement latency and directional error rate. Further, we used two distractor conditions according to whether the distractor’s location changes asynchronously or synchronously with the location of the target. We found that the asynchronous distractor yielded poorer performance than its synchronous counterpart, with significantly higher movement latencies and higher error rates. We interpret these results in an action selection framework with two actions (move left or right) and competing ‘action requests’ offered by the target and distractor. As such, the results provide insights into action selection performance in humans and supply data for directly constraining future computational models therein.

Stimulus Array Onset as a Preparatory Signal in Attentional Selection

Warning signals enhance psychomotor performance by optimising preparation for the arrival of an event. Recent evidence, however, suggests that a warning signal can also disrupt attentional preparation by interfering with the process of preparing. It was hypothesised that a warning signal consisting of a change to the task-relevant items (array onset) may be more effective than a traditional warning signal consisting of the arrival, or removal, of a bar-cue which is independent of the task array. In three experiments array onset was a more effective warning signal than the bar-cue because reaction times were significantly faster without an increase in errors. In addition, an auditory warning signal resulted in faster reaction time than the bar-cue but in performance equivalent to that with an onset warning signal. Thus, the superiority of an auditory warning signal, reported by Davis and Green, was not found, when the interference of the visual warning signal with preparation was reduced. These results suggest that a visual warning signal consisting of a change to the stimulus array is more effective than an event independent from the stimulus array.

Individual Differences in Working Memory Capacity Modulates Semantic Negative Priming from Single Prime Words

The present study investigated whether semantic negative priming from single prime words depends on the availability of cognitive control resources. Participants with high vs. low working memory capacity (as assessed by their performance in complex span and attentional control tasks) were instructed to either attend to or ignore a briefly presented single prime word that was followed by either a semantically related or unrelated target word on which participants made a lexical decision. Individual differences in working memory capacity (WMC) mainly affected the processing of the ignored primes, but not the processing of the attended primes: While the latter produced reliable positive semantic priming for both high- and low-WMC participants, the former gave rise to reliable semantic negative priming only for high WMC participants, with low WMC participants showing the opposite positive priming effect. The present results extend previous findings in demonstrating that (a) single negative priming can reliably generalize to semantic associates of the prime words, and (b) a differential availability of cognitive control resources can reliably modulate the negative priming effect at a semantic level of representation.

Dissociable effects of salience on attention and goal-directed action

Everyday behavior frequently involves encounters with multiple objects that compete for selection. For example, driving a car requires constant shifts of attention between oncoming traffic, rearview mirrors, and traffic signs and signals, among other objects. Behavioral goals often drive this selection process [1, 2]; however, they are not the sole determinant of selection. Physically salient objects, such as flashing, brightly colored hazard signs, or objects that are salient by virtue of learned associations with reward, such as pictures of food on a billboard, often capture attention regardless of the individual's goals [3-6]. It is typically thought that strongly salient distractor objects capture more attention and are more disruptive than weakly salient distractors [7, 8]. Counterintuitively, though, we found that this is true for perception, but not for goal-directed action. In a visually guided reaching task [9-11], we required participants to reach to a shape-defined target while trying to ignore salient distractors. We observed that strongly salient distractors produced less disruption in goal-directed action than weakly salient distractors. Thus, a strongly salient distractor triggers suppression during goal-directed action, resulting in enhanced efficiency and accuracy of target selection relative to when weakly salient distractors are present. In contrast, in a task requiring no goal-directed action, we found greater attentional interference from strongly salient distractors. Thus, while highly salient stimuli interfere strongly with perceptual processing, increased physical salience or associated value attenuates action-related interference.

Intentional and Reactive Inhibition During Spoken-Word Stroop Task Performance in People With Aphasia

PURPOSE

The integrity of selective attention in people with aphasia (PWA) is currently unknown. Selective attention is essential for everyday communication, and inhibition is an important part of selective attention. This study explored components of inhibition-both intentional and reactive inhibition-during spoken-word production in PWA and in controls who were neurologically healthy (HC). Intentional inhibition is the ability to suppress a response to interference, and reactive inhibition is the delayed reactivation of a previously suppressed item.

METHOD

Nineteen PWA and 20 age- and education-matched HC participated in a Stroop spoken-word production task. This task allowed the examination of intentional and reactive inhibition by evoking and comparing interference, facilitation, and negative priming effects in different contexts.

RESULTS

Although both groups demonstrated intentional inhibition, PWA demonstrated significantly more interference effects. PWA demonstrated no significant facilitation effects. HC demonstrated significant reverse facilitation effects. Neither group showed significant evidence of reactive inhibition, though both groups showed similar individual variability.

CONCLUSIONS

These results underscore the challenge interference presents for PWA during spoken-word production, indicating diminished intentional inhibition. Although reactive inhibition was not different between PWA and HC, PWA showed difficulty integrating and adapting to contextual information during language tasks.

Inhibitory mechanisms in single negative priming from ignored and briefly flashed primes: the key role of the inter-stimulus interval

The influence of interstimulus intervals (ISIs) on priming effects was investigated using a single-prime negative priming (NP) paradigm. In all experiments, a brief (16ms), centrally displayed prime (a Chinese character, to be ignored) appeared, followed by a pattern mask and then a centrally displayed target (another semantically related or unrelated Chinese character); the task required semantic categorization (animate/inanimate) of the target. An ISI could occur either between prime and mask (Experiments 1 and 5) or between mask and target (Experiments 2-4). The results revealed NP when a 470ms ISI occurred between prime and mask (Experiments 1 and 5) and when a 700ms ISI occurred between mask and target (Experiments 3 and 4). In contrast, when a long prime-target SOA was maintained but the mask-target ISI was shortened, NP disappeared (Experiment 4). The results indicated that a persisting mask/distractor (without ISI) located in the same position as the following target interfered with the buildup of inhibition, but an ISI between prime and mask or mask and target eliminated this interference, and that inhibition processes induced by an ignore instruction were implemented faster with an ISI placed between prime and mask than with an ISI placed between mask and target.

Effects of spatial response coding on distractor processing: evidence from auditory spatial negative priming tasks with keypress, joystick, and head movement responses

Prior studies of spatial negative priming indicate that distractor-assigned keypress responses are inhibited as part of visual, but not auditory, processing. However, recent evidence suggests that static keypress responses are not directly activated by spatially presented sounds and, therefore, might not call for an inhibitory process. In order to investigate the role of response inhibition in auditory processing, we used spatially directed responses that have been shown to result in direct response activation to irrelevant sounds. Participants localized a target sound by performing manual joystick responses (Experiment 1) or head movements (Experiment 2B) while ignoring a concurrent distractor sound. Relations between prime distractor and probe target were systematically manipulated (repeated vs. changed) with respect to identity and location. Experiment 2A investigated the influence of distractor sounds on spatial parameters of head movements toward target locations and showed that distractor-assigned responses are immediately inhibited to prevent false responding in the ongoing trial. Interestingly, performance in Experiments 1 and 2B was not generally impaired when the probe target appeared at the location of the former prime distractor and required a previously withheld and presumably inhibited response. Instead, performance was impaired only when prime distractor and probe target mismatched in terms of location or identity, which fully conforms to the feature-mismatching hypothesis. Together, the results suggest that response inhibition operates in auditory processing when response activation is provided but is presumably too short-lived to affect responding on the subsequent trial.

An attentional-adaptation account of spatial negative priming: evidence from event-related potentials

Negative priming (NP) refers to a slower response to a target stimulus if it has been previously ignored. To examine theoretical accounts of spatial NP, we recorded behavioral measures and event-related potentials (ERPs) in a target localization task. A target and distractor briefly appeared, and the participant pressed a key corresponding to the target's location. The probability of the distractor appearing in each of four locations varied, whereas the target appeared with equal probabilities in all locations. We found that response times (RTs) were fastest when the prime distractor appeared in its most probable (frequent) location and when the prime target appeared in the location that never contained a distractor. Moreover, NP effects varied as a function of location: They were smallest when targets followed distractors in the frequent distractor location-a finding not predicted by episodic-retrieval or suppression accounts of NP. The ERP results showed that the P2, an ERP component associated with attentional orientation, was smaller in prime displays when the distractor appeared in its frequent location. Moreover, no differences were apparent between negative-prime and control trials in the N2, which is associated with suppression processes, nor in the P3, which is associated with episodic retrieval processes. These results indicate that the spatial NP effect is caused by both short- and long-term adaptation in preferences based on the history of inspecting unsuccessful locations. This article is dedicated to the memory of Edward E. Smith, and we indicate how this study was inspired by his research career.

Evidence inhibition responds reactively to the salience of distracting information during focused attention

Along with target amplification, distractor inhibition is regarded as a major contributor to selective attention. Some theories suggest that the strength of inhibitory processing is proportional to the salience of the distractor (i.e., inhibition reacts to the distractor intensity). Other theories suggest that the strength of inhibitory processing does not depend on the salience of the distractor (i.e., inhibition does not react to the distractor intensity). The present study aimed to elucidate the relationship between the intensity of a distractor and its subsequent inhibition during focused attention. A flanker task with a variable distractor-target stimulus-onset asynchrony (SOA) was used to measure both distractor interference and distractor inhibition. We manipulated the intensity of the distractor in two separate ways, by varying its distance from the target (Experiment 1) and by varying its brightness (Experiment 2). The results indicate that more intense distractors were associated with both increased interference and stronger distractor inhibition. The latter outcome provides novel support for the reactive inhibition hypothesis, which posits that inhibition reacts to the strength of distractor input, such that more salient distractors elicit stronger inhibition.

Differences in the strength of distractor inhibition do not affect distractor-response bindings

Distractor inhibition and distractor-response binding were investigated in two experiments by analyzing distractor repetition benefits and their interaction with response repetition effects in a sequential-priming paradigm. Distractor repetition benefits were larger for distractors that were incompatible with the to-be-executed response (task-related distractors) than for distractors that were not assigned to a response (neutral distractors), indicating that the strength of distractor inhibition was a function of response interference for the distractors. In contrast, the distractor-response bindings were found to be of equal strength for both task-related and neutral distractors. Thus, differences in the strengths of distractor inhibition did not affect the integration of distractors with responses into event files. Instead, our results suggest that distractor-response binding and distractor inhibition are independent mechanisms that are recruited for the automatization of behavior and action control.

Identity-based inhibitory processing during focused attention

Recent data suggest that the operating principles governing inhibition of distractor-related activity may deviate from dominant models describing inhibitory processing during selective attention. Here we aimed to gain a better understanding of these data in order to determine whether they actually defy premises of current models. In addition to providing evidence against noninhibitory accounts of the data (see especially Experiment 6), the results support three main novel findings that challenge current theories. First, the data provide evidence that inhibition overpowered excitation from ongoing external input (Experiments 1-4), which suggests that inhibitory control processes are more powerful than current models indicate. Second, negative effects emerged even when targets appeared alone (Experiment 5), which suggests that selection does not play an essential role in triggering inhibitory processing. Third, relatively early distractor-related activity was affected, which supports a role for inhibition prior to action control (Experiment 3). These findings suggest a need to revise current models describing inhibition of distracting information during selective attention.

Negative priming under rapid serial visual presentation

Negative priming (NP) was examined under a new paradigm wherein a target and distractors were temporally separated using rapid serial visual presentation (RSVP). The results from the two experiments revealed that (a) NP was robust under RSVP, such that the responses to a target were slower when the target served as a distractor in a previous trial than when it did not; (b) NP was found regardless of whether the distractors appeared before or after the targets; and (c) NP was stronger when the distractor was more distinctive. These findings are generally similar to those on NP in the spatial search task. The implications for the processes causing NP under RSVP are discussed in the current paper.

Identity negative priming: a phenomenon of perception, recognition or selection?

The present study addresses the problem whether negative priming (NP) is due to information processing in perception, recognition or selection. We argue that most NP studies confound priming and perceptual similarity of prime-probe episodes and implement a color-switch paradigm in order to resolve the issue. In a series of three identity negative priming experiments with verbal naming response, we determined when NP and positive priming (PP) occur during a trial. The first experiment assessed the impact of target color on priming effects. It consisted of two blocks, each with a different fixed target color. With respect to target color no differential priming effects were found. In Experiment 2 the target color was indicated by a cue for each trial. Here we resolved the confounding of perceptual similarity and priming condition. In trials with coinciding colors for prime and probe, we found priming effects similar to Experiment 1. However, trials with a target color switch showed such effects only in trials with role-reversal (distractor-to-target or target-to-distractor), whereas the positive priming (PP) effect in the target-repetition trials disappeared. Finally, Experiment 3 split trial processing into two phases by presenting the trial-wise color cue only after the stimulus objects had been recognized. We found recognition in every priming condition to be faster than in control trials. We were hence led to the conclusion that PP is strongly affected by perception, in contrast to NP which emerges during selection, i.e., the two effects cannot be explained by a single mechanism.

On the decay of distractor-response episodes

Distractor-to-distractor repetition effects can be explained by retrieval and/or inhibitory processes. Interestingly, the two accounts predict different effects from repeated distractors: Inhibition theories always predict benefits, whereas stimulus-response-retrieval theories predict an interaction of response repetition and distractor repetitions, resulting in benefits with response repetitions and costs with response changes. In the present experiment the time-course and the temporal separability of a stimulus-response episode on distractor-to-distractor repetitions were analyzed. The results showed that the interaction of response repetition and distractor repetitions was affected by a simple decay function. In addition, distractor repetition effects were affected by the temporal separability. In concert, the data yield evidence for retrieval-based explanations of distractor-to-distractor repetitions.

Motor inhibition associated with the affordance of briefly displayed objects

Research has demonstrated that left- and right-hand responses are facilitated when they are performed with the hand compatible with the orientation of a viewed object. This suggests that graspable objects automatically activate the motor representations that correspond to their orientation. It has recently been proposed that similar positive stimulus–response compatibility effects (PCE) may turn into negative compatibility effects (NCE) when a prime object is displayed very briefly. These NCEs are suggested to reflect motor inhibition mechanisms—motor activation triggered by briefly viewed objects may be treated by the motor system as unwanted, and thus it is rapidly inhibited. We examined whether the motor activation triggered by the orientation of a task-irrelevant object is similarly inhibited when the object is displayed briefly. In Experiment 1, a NCE was observed between the orientation of an object and the responding hand when the object was displayed for 30 or 70 ms. The effect turned into a PCE when the object was displayed for 370 ms. Experiment 2 confirmed that this motor inhibition effect was produced by the handle affordance of the object rather than some abstract visual properties of the object.

Attention modulates motor system activation during action observation: evidence for inhibitory rebound

Perceiving another individual’s actions activates the human motor system. We investigated whether this effect is stronger when the observed action is relevant to the observer’s task. The mu rhythm (oscillatory activity in the 8- to 13-Hz band over sensorimotor cortex) was measured while participants watched videos of grasping movements. In one of two conditions, the participants had to later report how many times they had seen a certain kind of grasp. In the other condition, they viewed the identical videos but had to later report how many times they had seen a certain colour change. The colour change and the grasp always occurred simultaneously. Results show mu rhythm attenuation when watching the videos relative to baseline. This attenuation was stronger when participants later reported the grasp rather than the colour, suggesting that the motor system is more strongly activated when the observed grasping actions were relevant to the observer’s task. Moreover, when the graspable object disappeared after the offset of the video, there was subsequent mu rhythm enhancement, reflecting a post-stimulus inhibitory rebound. This enhancement was again stronger when making judgments about the grasp than the colour, suggesting that the stronger activation is followed by a stronger inhibitory rebound.

A repetition-suppression account of between-trial effects in a modified Stroop paradigm

Theories that postulate cognitive inhibition are very common in psychology and cognitive neuroscience [e.g., Hasher, L., Lustig, C., & Zacks, R. T. (2007). Inhibitory mechanisms and the control of attention. In A. Conway, C. Jarrold, M. Kane, A. Miyake, A. Towse, & J. Towse (Eds.), Variation in working memory (pp. 227-249). New York, NY: Oxford, University Press], although they have recently been severely criticized [e.g., MacLeod, C. M., Dodd, M. D., Sheard, E. D., Wilson, D. E., & Bibi, U. (2003). In opposition to inhibition. In H. Ross (Ed.), The psychology of learning and motivation (Vol. 43, pp. 163-214). Elsevier Science]. This paper poses and attempts to answer the question whether a research program with cognitive inhibition as its main theoretical assumption is still worth pursuing. We present a set of empirical data from a modified Stroop paradigm that replicates previously reported findings. These findings refer to between-trial effects previously described in the literature on Stroop, negative priming, and inhibition-of-return. Existing theoretical accounts fail to explain all these effects in an integrated way. A repetition-suppression mechanism is proposed in order to account for these data. This mechanism is instantiated as a computational cognitive model. The theoretical implications of this model are discussed.

A reassessment of negative priming within the inhibition framework of cognitive aging: there is more in it than previously believed

Three negative-priming studies were carried out to examine whether this paradigm allows a separation of the effects of aging on access, deletion, and restraint control of inhibition. In each study 24 younger (18 to 35 years old) and 24 older (57 to 82 years old) adults were asked to identify pictures. The results reveal difficulties among older adults in preventing the access of distracting perceptual input into responses; however, the ability to restrain inappropriate answers and the ability to delete once-relevant information are not affected by age.

An fMRI investigation into the neural mechanisms of spatial attentional selection in a location-based negative priming task

Selective attention enables us to respond to objects and events that are relevant to our goals for adaptive interactions with the environment. Despite evidence from research addressing the selection of a target location, little is known about the neural mechanisms of attentional selection in situations in which the selection is biased in favor of the information in the irrelevant location. In this study, we combined event-related fMRI and a location-based negative priming paradigm with a prime-probe-trial design to investigate the neural mechanisms of spatial attentional selection. Participants were instructed to respond to the location of a pre-specified target while ignoring a distractor at an irrelevant location. The goal of this study was twofold. First, we identified brain regions that are linked to conflict resolution situations, in which the selection bias puts the irrelevant information in the probe trial on a selection advantage over the target. Second, we determined the mechanism of conflict resolution when the encoding conditions of stimuli are manipulated by presenting stimuli either abruptly (onset) or masked (no-onset). The results showed that the bottom-up-induced competition among stimuli in the target selection is stronger for onset than no-onset stimuli. The superior parietal lobule was sensitive to those changes in bottom-up-induced competition. Furthermore, the dorsolateral prefrontal cortex and inferior parietal lobe were activated to resolve the additional processing effort necessary to select the negatively biased target. In conclusion, the present study identified dissociable neural components needed to resolve the negative selection bias, which attentional modulation can be addressed in future studies by examining changes in the functional connectivity.

Prime display offset modulates negative priming only for easy-selection tasks

Responses to probe targets that have been distractors in a prime display are slower than responses to new targets, a finding called negative priming (NP). The selective attention model, which attributes NP to lingering inhibition of the prime distractor, predicts that NP should occur only when the prime display has disappeared before the probe display is processed. The present study tested this prediction both in easy- and in difficult selection tasks. In Experiments 1, 2, and 3A, target selection was easy, and NP was observed only after prime display offset, regardless of whether offset was manipulated between or within participants. In Experiment 3B, target selection was difficult, and NP was found with and without prime display offset. Experiment 4 replicated the finding of NP without prime display offset in a difficult-selection task. A modified version of the selective attention model can explain the results of the present study. However, we also discuss the results in light of episodic retrieval theory and temporal discrimination theory.

Attentional demand and memory retrieval in negative priming

Negative priming refers to delayed response to previous distractors, and can reflect the operation of attentional selection in prime trials. One important feature of negative priming is that it is modulated by the characteristics of probe trials. The current study manipulated competition from probe distractors and prime-probe similarity to examine the effects of attentional demand and memory retrieval in probe trials. The results demonstrated that the effects of attentional demand and memory retrieval on negative priming were dynamic. Distractor competition in probe trials affected negative priming in Experiment 1, and prime-probe similarity affected negative priming in Experiment 2. Moreover, negative priming in Experiment 3 was observed either when competition from probe distractors was strong or when identical spatial layouts were used in prime-probe couplets. Taken together, either competition from probe distractors or prime-probe similarity of spatial layouts was critical to the manifestation of negative priming at one time. Implications for distractor inhibition and memory retrieval in negative priming were discussed.

Negative Priming as a Memory Phenomenon

Abstract. Reactions to recently ignored stimuli are slowed down or more error prone when compared to reactions to control stimuli. This so-called negative priming effect has been traditionally investigated in the area of selective attention. More recent theory developments conceptualize the negative priming effect as a memory phenomenon. This review presents four models to explain the phenomenon as well as their essential empirical evidence. The review also considers several negative priming characteristics - that is stimulus modality, prime selection and prime response requirement, probe interference, stimulus repetition, aging and thought disorders, and physiological correlates. On these bases, it is concluded that only the distractor inhibition and the episodic retrieval models have survived empirical testing so far. Whereas evidence has increased that negative priming clearly obeys memory retrieval principles, the distractor inhibition model has lost much of its persuasiveness within recent years.

Dissociating local and global levels of perceptuo-motor control in masked priming

Masked prime stimuli presented near the threshold of conscious awareness affect responses to subsequent targets. The direction of these priming effects depends on the interval between masked prime and target. With short intervals, benefits for compatible trials (primes and targets mapped to the same response) and costs for incompatible trials are observed. This pattern reverses with longer intervals. We argue (a) that these effects reflect the initial activation and subsequent self-inhibition of the primed response, and the corresponding inhibition and subsequent disinhibition of the nonprimed response, and (b) that they are generated at dissociable local (within response channels) and global (between channels) levels of motor control. In two experiments, global-level priming effects were modulated by changing the number of response alternatives, whereas local-level effects remained unaffected. These experiments suggest that low-level motor control mechanisms can be successfully decomposed into separable subcomponents, operating at different levels within the motor system.

Cognitive conflict without explicit conflict monitoring in a dynamical agent

We examine mechanisms for resolving cognitive conflict in an embodied, situated, and dynamic agent, developed through an evolutionary learning process. The agent was required to solve problems of response conflict in a dual-target "catching" task, focusing response on one of the targets while ignoring the other. Conflict in the agent was revealed at the behavioral level in terms of increased latencies to the second target. This behavioral interference was correlated to peak violations of the network's stable state equation. At the level of the agent's neural network, peak violations were also correlated to periods of disagreement in source inputs to the agent's motor effectors. Despite observing conflict at these numerous levels, we did not find any explicit conflict monitoring mechanisms within the agent. We instead found evidence of a distributed conflict management system, characterized by competitive sources within the network. In contrast to the conflict monitoring hypothesis [Botvinick, M. M., Braver, T. S., Barch, D. M., Carter, C. S., & Cohen, J. D. (2001). Conflict monitoring and cognitive control. Psychological Review, 108(3), 624-652], this agent demonstrates that resolution of cognitive conflict does not require explicit conflict monitoring. We consider the implications of our results for the conflict monitoring hypothesis.

Negative priming is stronger for task-relevant dimensions: Evidence of flexibility in the selective ignoring of distractor information

The finding that in selective attention tasks responses to previously ignored stimuli are usually retarded is known as negative priming (NP). In previous studies it has been suggested that NP can depend on behavioural goals--that is, NP was observed only for task-relevant object dimensions. We extend these findings with two experiments demonstrating that stronger NP can be observed for task-relevant dimensions than for task-irrelevant dimensions (a) even if participants' tasks vary blockwise within an experiment and (b) if behavioural goals vary from trial to trial. These results suggest that selective NP is a much more flexible process than previously assumed.

Spatial negative priming in early Alzheimer's disease: evidence for reduced cognitive inhibition

Some studies of negative priming and other tasks assumed to reflect inhibitory functions suggest a decline in inhibitory processes in Alzheimer's disease. However, none of the measures used in previous studies can be interpreted as an unambiguous reflection of distractor inhibition. The present study investigates whether reductions in negative priming associated with Alzheimer's disease reflect reduced distractor inhibition, rather than perceptual review processes. Individuals with early Alzheimer's disease were predicted to show reduced negative priming on a spatial localization task designed to provide an unambiguous measure of distractor inhibition. Sixteen clinical participants showed significantly less negative priming than old and young healthy control groups, which is interpreted as evidence for reduced distractor inhibition in early dementia. A second analysis indicated that, within the clinical sample only, negative priming effect size was significantly correlated with prime trial response speed. Clinical participants showing the least negative priming were slower to respond to an initial stimulus. The results may mean that people with early Alzheimer's disease have a reduced capacity to use excitatory as well as inhibitory processes in selection.

Existe-t-il un déficit d’inhibition lors du vieillissement ? Confrontation de l’hypothèse dorso-ventrale et de l’hypothèse frontale dans l’effet d’amorçage négatif

BACKGROUND

Over the past decades, cognitive psychology contribution to our understanding of aging relies on two major perspectives, focusing on the selective impact of age on either cognitive multiple-systems or global factors of cognition: slowing, working memory and inhibition. In the latter, reduction in inhibitory control during aging (in its access, deletion or restraint functions) is associated with poorer performance on a variety of tasks referring to memory, comprehension or language [Hasher, Zacks and May (16)]. The attractiveness of inhibition as an explanatory factor results in part in the absence of negative priming during aging. Negative priming refers to the slow down of latencies when individuals have to respond to recently ignored informations, compared to unrelated informations. The dissociation, between a preserved location negative priming and an absence of identity negative priming during aging, supports the dorsal-ventral model of inhibition which suggests that spatial and identity inhibition are supported by different and independent visual pathways. An alternative model, directly at odds, is that inhibitory mechanisms are supported by the frontal lobe. In this perspective, inhibition is not a central process responsible for the control of working memory contents, but an automatic and local mechanism whose triggering depends on controlled attention. Therefore, working memory drives efficient inhibition by sustaining task instructions and appropriate responses throughout task execution. This hypothesis is consistent with Houghton and Tipper's (17) architecture of selective attention. According to the authors, the presence or absence of automatic inhibition is very closely linked to a Match/Mismatch field whose function is to compare the present stimulus to an internal self-generated internal template. When an information fails to match the subject's current goals, the match/mismatch field causes an automatic inhibitory imbalance which reduces the to-be-ignored properties' responsiveness. In contrast, information matching subjects' goal is enhanced through an automatic excitatory imbalance. The accurate functioning of the Match/Mismatch field requires efficient executive functioning responsible for the uphold of goals and correct responses. In the case of negative priming, manipulating the efficiency of working memory is of interest as it should affect the triggering of slowing, ie, an indirect inhibitory deficit, when the task is resource demanding [Conwayet al. (6)]. Moreover, if inhibition, as reflected by negative priming, is mediated by individual resource capacity, then NP should disappear during aging only when individuals are engaged in a resource-demanding task.

OBJECTIVES

To address this issue, we examine whether cognitive control load in a gender decision task contributed to the presence or absence of NP during aging. According to the dorsal-ventral model, task complexity should not have any impact on performance, since gender decision task relies on a conceptual analysis of information. In turn, the frontal model predicts that age differences in performance profile will only differ when individual resource capacity is overloaded.

DESIGN OF THE STUDY

Sixty-four participants (32 young and 32 older adults) performed a gender categorisation task through two experiments. Trials involved two stimuli presented successively at the same location. A word served as a prime and a word as a target. Both prime and target could be male or female. When prime and target matched on gender, we talked about VALID pairs (or compatible). When prime and target mismatched on the manipulated features, we talked about INVALID pairs (or incompatible). Participants' task was to identify the gender of the target. They were explicitly instructed not to respond to primes but to read them silently. Our interest was in response latencies for valid versus invalid pairs. We manipulated task complexity by the absence (experiment 1) or presence (experiment 2) of a distractor during probe trials.

RESULTS

For younger adults, primes presented before targets gave rise to behavioural costs when pairs were mapped to the same response compared to pairs that were mapped to opposite ones. This slowing, called Negative Compatibility Effect (NCE), was independent of the presence or absence of a distractor. NCE was reliable for the elderly patients only under condition of no interfering information during the probe trial: pattern of performance of older participants was identical to that of young adults (experiment 1). This effect disappeared as task complexity increased (experiment 2).

DISCUSSION

This result suggests that NCE triggering is dependant on the amount of cognitive control engaged by the task, and therefore that the ability to inhibit irrelevant information is secondary to a general capacity of the working memory.

CONCLUSION

The implications of our data are consistent with the level of processing account, as well as the recent neuroimaging contributions which suggest, for example, the involvement of the dorso-lateral prefrontal cortex (sensitive to aging) when task demands are high, and a ventro-lateral prefrontal implication when demands are low [see Eenshuistra et al. for a review (10)].