Target processing is facilitated by motivationally relevant cues

The effect that motivationally relevant stimuli have on processes of attentional engagement and disengagement was investigated during two modified peripheral cueing paradigms. Sexual, mutilation, threatening, and neutral stimuli served as peripheral cues in both experiments. Responses were made to target location in Experiment 1 (N=19 female) and target identity in Experiment 2 (N=18 female). As indexed by enhanced target-evoked P1 and P3b component amplitudes, target processing was facilitated by the presentation of sexual and mutilation stimuli in both experiments. This facilitation in response to targets cued by sexual and mutilation stimuli occurred regardless of whether cueing was valid or invalid as demonstrated by the non-significant cue validity x picture-type interaction. As such, the processes of attentional engagement (as inferred by responses to validly cued targets) and attentional disengagement (as inferred by responses to invalidly cued targets) were not differentially affected by the motivational relevance of the preceding cue. These results indicate that in a non-clinical sample, participants can shift attention rapidly to process information following the onset of motivationally relevant stimuli at attended (valid) and unattended (invalid) locations and that target processing is facilitated by the presence of appetitive and aversive cues.     

The effect of attentional cueing on conscious awareness of stimulus and response

Attending to a cued location in space leads to faster reaction times when a stimulus is presented there. The reasons for this attentional effect, and its specific locus in the information-processing chain between stimulus and response, remain unclear. One suggestion is that attention speeds the conscious detection of stimuli. Surprisingly, this possibility appears not to have been tested directly. To resolve this question, we asked subjects to make simple responses to lateralised targets that followed either a valid, invalid or neutral cue, and to judge the perceived time of the target onset, or of their response, by delayed report of the position of a clock hand. Our results showed that only a small and non-significant part of the attentional effect is due to delayed conscious awareness of the stimulus. The greater part of the attentional effect is localised either subsequent to conscious detection of stimuli or occurs in a separate, parallel processing stream from that which generates the motor response. Electronic Publication     

Spatial attention modulates sound localization in barn owls

Attentional influence on sound-localization behavior of barn owls was investigated in a cross-modal spatial cuing paradigm. After being cued to the most probable target side with a visual cuing stimulus, owls localized upcoming auditory target stimuli with a head turn toward the position of the sound source. In 80% of the trials, cuing stimuli pointed toward the side of the upcoming target stimulus (valid configuration), and in 20% they pointed toward the opposite side (invalid configuration). We found that owls initiated the head turns by a mean of 37.4 ms earlier in valid trials, i.e., mean response latencies of head turns were reduced by 16% after a valid cuing stimulus. Thus auditory stimuli appearing at the cued side were processed faster than stimuli appearing at the uncued side, indicating the influence of a spatial-selective attention mechanism. Turning angles were not different when owls turned their head toward a cued or an uncued location. Other types of attention influencing sound localization, e.g., a reduction of response latency as a function of the duration of cue-target delay, could not be observed. This study is the first attempt to investigate attentional influences on sound localization in an animal model.     

Developmental Changes in Measures of Hierarchical Stimulus Recognition in Conditions of Directed Attention in Children Aged 5–10 Years

Reaction times and the accuracy of recognition of hierarchical letter stimuli at the local and global levels were studied in 95 children of four age groups (5–6, 6–7, 7–8, and 9–10 years) and 10 adults. Overall, children of all age groups and adults recognized hierarchical stimuli at the global level more accurately and rapidly than at the local level (the global advantage effect) and showed slowing of reactions on recognition of incongruent stimuli at the local level (the global interference effect). At younger ages (5–6 years), there were significant individual differences in measures of recognition of hierarchical letters – in some children of this age (seven of 37), the global advantage effect on recognition of incongruent stimuli was absent. Significant progressive changes in the accuracy of recognition of hierarchical stimuli at both the local and global levels were seen on development from 6–7 to 7–8 years, as well as in adults a compared with children aged 9–10 years. Different developmental dynamics in the speed of recognition of hierarchical stimuli were seen at the local and global levels: the speed of recognition of small letters increased significantly in each sequential age group, starting from 6–7 years, while recognition of large letters showed no significant decrease in reaction times in children aged 9–10 years as compared with those aged 7–8 years. In the two youngest age groups (5–6 and 6–7 years), the type of hierarchical stimulus was found to influence recognition speed: reaction times increased significantly, independently of the level of recognition, using both target (incongruent stimuli) and neutral elements at the irrelevant level. It is suggested that the nonlinear developmental dynamics of measures of the recognition of hierarchical stimuli at preschool and early school age are determined by the maturation of the mechanisms processing sense-specific information and by the formation of executive functions, especially those associated with selective extraction of significant signals.     

The time course of spatial orienting elicited by central and peripheral cues: evidence from event-related brain potentials

To study differences in the time course of attentional orienting triggered by salient peripheral events and by central symbolic precues, event-related brain potentials (ERPs) were recorded in response to letter stimuli following spatially informative symbolic or peripheral precues after a cue-target interval (CTI) of either 200 or 700 ms. Stimuli at cued (attended) locations elicited an enhanced negativity relative to stimuli at uncued locations. With short CTIs, these effects started around 150 ms post-stimulus for peripheral cues. They were delayed by about 100 ms for central cues. This latency difference is assumed to reflect fast exogenous orienting elicited by peripheral, but not by central cues. Beyond 200 ms post-stimulus, attentional negativities were larger with long CTIs than with short CTIs for both cue types, presumably related to the gradual build-up of endogenous orienting triggered by spatially predictive events.     

Instability in the latency of P3a/P3b brain potentials and cognitive function in aging

Instability in performance is a prominent feature of aging. In this study, 133 participants evenly distributed across the adult lifespan underwent a three-stimulus event-related potentials (ERPs) paradigm, and instability in P3a/P3b latency and reaction time (RT) were measured. P3a is related to alertness or reorientation of attention and it was elicited by distractor stimuli. P3b is related to controlled attentional processes and it was triggered by target stimuli. Maximum-likelihood estimation (MLE) was used to quantify the level of variability in latency across the single sweep ERPs. The results revealed increased variability in RT but not in P3a/P3b latency with age. Variability in P3a/P3b latency was related to executive functions, and variability in RT to speed. Generally, the relationships tended to increase with age. It can be concluded that increased variability in RT with age is caused by instability in processes related to response execution and possibly response selection, but not stimulus classification. Further, the results indicate that intraindividual variability is not a uniform concept, but has unique explanatory value at the neurophysiological and behavioral level.     

Event-related potential evidence for a dual-locus model of global/local processing

We investigated the perceptual time course of global/local processing using event-related potentials (ERPs). Participants discriminated the global or local level of hierarchical letters of different sizes and densities. Participants were faster to discriminate the local level of large/sparse letters and the global level of small/dense letters. This was mirrored in early ERP components: The N1/N2 had smaller peak amplitudes when participants made discriminations at the level that took precedence. Only global discriminations for large/sparse letters led to amplitude enhancement of the later P3 component, suggesting that additional attention-demanding processes are involved in discriminating the global level of these stimuli. Our findings suggest a dual-locus time course for global/local processing: (a) Level precedence occurs early in visual processing; (b) extra processing is required at a later stage, but only for global discriminations of large, sparse, stimuli, which may require additional attentional resources for active grouping.     

Electrophysiological Study of Intrahemispheric S-R Compatibility Effects Elicited by Visual Directional Cues

The effects of stimulus-response (S-R) spatial compatibility on reaction time (RT) and P300 component latency were studied, in order to determine whether spatial conflict effects can occur within a single cerebral hemisphere, and whether there are differences between hemispheres regarding such effects. Two choice RT experimental conditions were employed: I) an extrafoveal condition, in which stimuli (small arrows pointing either to the right or to the left) appeared laterally in one visual hemifield, the responses being given with the hand situated on the same side; likewise with the opposite hemifield and hand (cond. I); and II) a foveal condition, in which the same type of stimuli appeared centrally on the fovea, the response being given successively with both hands (cond. II). In either case, the color of the stimuli (cue information) determined which finger (forefinger or ring finger) of the same hand would deliver the response. Thus, the cue was either compatible, or not, with the stimulus orientation (arrows). In each condition, the four possible stimulus combinations, according to direction and color of the arrows, were presented at random. Results showed that: 1) in the extrafoveal condition, S-R compatibility effects were observed in each single hemisphere, and were reflected both by RT and by P300 latency; 2) both hemispheres reacted in the same way to the spatial conflict; and 3) foveal vision increased the overall effect of the conflict on both P300 latency and RT.     

Global processing of compound lettersin a patient with Balint's syndrome

We report data on the ability of a patient with Balint's syndrome (GK) to process global information from compound letters. As with other patients with Balint's syndrome, GK was impaired at respond-ing to large, global letters. In Experiment 1 we show that this was due to local capture rather than the absolute size of the stimuli. Also, despite his impairment with global letters, GK showed global inter-ference on local judgements, indicating that some implicit processing took place at the global level. Interestingly, the inability to perceive large global letters was overcome when GK identified a solid, large prime letter prior to the onset of the compound figure (Experiment 2). This priming effect was temporary, and decreased as the interval between the prime and the compound letter increased (Experiment 3). When the prime was an English letter, the effect was maintained even when GK only had to identify the prime's colour, provided a colour-identification block of trials followed rather than preceded a block of trials where prime shapes had to be identified (Experiment 4). In contrast, there was no priming when GK had to identify the colour of English letter primes in a trial block following a block where the task was to identify the colour of Hebrew letter primes (Experiment 5). Overall the data indicate that local capture in Balint's syndrome can be overcome by actively priming a wide attentional window. The results can be interpreted in terms of an interaction between spatial attention and grouping processes that subserves the perception of global compound letters.     

Global processing of compound lettersin a patient with Balint's syndrome( )

We report data on the ability of a patient with Balint's syndrome (GK) to process global information from compound letters. As with other patients with Balint's syndrome, GK was impaired at respond-ing to large, global letters. In Experiment 1 we show that this was due to local capture rather than the absolute size of the stimuli. Also, despite his impairment with global letters, GK showed global inter-ference on local judgements, indicating that some implicit processing took place at the global level. Interestingly, the inability to perceive large global letters was overcome when GK identified a solid, large prime letter prior to the onset of the compound figure (Experiment 2). This priming effect was temporary, and decreased as the interval between the prime and the compound letter increased (Experiment 3). When the prime was an English letter, the effect was maintained even when GK only had to identify the prime's colour, provided a colour-identification block of trials followed rather than preceded a block of trials where prime shapes had to be identified (Experiment 4). In contrast, there was no priming when GK had to identify the colour of English letter primes in a trial block following a block where the task was to identify the colour of Hebrew letter primes (Experiment 5). Overall the data indicate that local capture in Balint's syndrome can be overcome by actively priming a wide attentional window. The results can be interpreted in terms of an interaction between spatial attention and grouping processes that subserves the perception of global compound letters.     

Tobacco smoking and event-related brain potentials in a Stroop task.

Behavioral and event-related brain potential (ERP) measures were used to assess the effects of tobacco smoking on selective attention. Two groups of abstinent smokers performed a Stroop color-naming task. The display color of a stimulus word determined the correct response, whereas word meaning was irrelevant. Meaning was congruent, neutral, or incongruent with respect to color. After completing two blocks of trials under abstinent conditions, subjects received a 15-min break before performing two more blocks. Subjects in the Smoking group (N=12) smoked two cigarettes during the break. Matched Control subjects (N=12) did not smoke during the break. Typical Stroop effects were found, as reaction time (RT) was shortest to congruent words, intermediate to neutral words, and longest to incongruent words. Overall RT decreased after the break equally for the Smoking and Control groups, whereas the magnitude of the Stroop effect was unchanged for either group. P300 amplitude decreased after the break for the Smoking group but not for the Control group, which implied that smoking rather than practice produced component decline. Error rate and P300 latency did not change after the break for either group. The results suggest that tobacco smoking may decrease the availability of general attentional resources required to evaluate colored word stimuli, whereas the specific stimulus processing mechanisms responsible for the Stroop effect are relatively unaffected.     

Reactivity and event-related potentials during attentional tests in athletes

A series of attentional tests involving reaction times (RTs) was administered to 12 high-level young (age 17–18 years) volleyball players. During the tests, event-related potentials were recorded by electroencephalogram. In a simple reaction-time test (SRT), the subjects had to respond to a letter that appeared on a white screen. Other tests (attentional shifting tests) consisted of a go/no-go reaction time and a choice reaction time (CRT), divided into a short-latency CRT and a long-latency CRT. In the pre-stimulus period of these tests, there is a shift from broad attention to selective attention, represented by a crowding of black points on the computer screen, followed by the appearance of a letter in the centre of the crowding. The results show that RT increased from SRT to CRT. In the attentional shifting tests, averaged waves of event-related potentials showed a contingent-negative-variation-like wave that was closely related to selective attention (selective attention wave, SAW) before the onset of the stimulus. After the stimulus, a P3 complex was recorded. Correlations were found between the SAW amplitude and P3 latency and amplitude, and between these parameters and RT and its variability. Higher SAW and P3 amplitudes were accompanied by a shorter RT and a lower variability. The characteristics and the correlations that exist between the various parameters are consistent with a possible use of these tests in the analysis of the attentional styles of athletes, and in the evaluation of their progress with training.     

P300-based Stroop study with low probability and target Stroop oddballs: The evidence still favors the response selection hypothesis

This paper addresses the issue of the locus of action in cognitive processing during Stroop effects. It uses the P300 latency to assess stimulus processing effects, but, for the first time, under conditions in which Stroop stimuli are rare and target stimuli. The study was also concerned with demonstrating that apparent P300s during verbal responding are in fact uninterpretable due to contamination of EEG by speech-related artifact. Three studies were presented. In Study 1, there were 3 blocks, each containing 1 of 3 types of rare Stroop stimuli (p = .15), congruent, neutral, and incongruent. There were also 3 response modes: button press (BUTTON), speaking aloud (VERBAL), and speaking to self (SILENT). Three sessions were used, each for a different response style. The only task was to name the color on each trial. In the 2 non-verbal blocks, Reaction Time (RT) varied by stimulus type; congruent < neutral < incongruent. P300 latency was the same across blocks in these non-verbal conditions in which one saw the classic Pz > Cz > Fz distribution. The much larger, speech artifact-contaminated “P300s” in the VERBAL blocks did suggest a Stroop effect, especially at Fz and Cz, where “P300s” were larger than at Pz. In Study 2, there were 2 response modes, VERBAL and SILENT, and only two rare Stroop stimuli; neutral and incongruent, 1 per block. In each of these blocks, one word–color combination was a designated target requiring a unique response. The subject was to name the color followed by a yes or no to categorize the target or non-target. Again the RT for incongruents was greater than RT for neutrals, without a parallel effect in P300 latency. Again, the rostral ERPs appeared artifactual in the VERBAL condition. Study 3 was a replication of the second study, except that motivated subjects, versus Psychology pool recruits, were used. The latency–RT correlation still failed to obtain. Thus, using classic P300-eliciting antecedents–rare and target (Stroop) stimuli–this study supports the view that the locus of Stroop interference is in response processing.     

Effects of response delays and of unknown stimulus‐response mappings on the oddball effect on P3

P3b is a prominent component of human event‐related EEG potentials. P3b has been related to consciousness, encoding into memory, and updating of strategic schemata, among others, yet evidence has also been provided for its close relationship with deciding how to respond to the presented stimuli. P3b is large with rarely occurring stimuli and small with frequent ones. Here, we investigate the extent to which this oddball effect depends on selecting and executing responses. Participants pressed one of two keys in response to one of two letters, one of which was presented rarely and one frequently. Information about letter‐key mapping was provided by a second stimulus. In different blocks, this mapping stimulus was either constant across trials or varied randomly, and either preceded or followed the letter. The oddball effect was reduced when responses were delayed (by waiting for the constant mapping stimulus following the letter) and was further reduced when responses could not be assigned to the letters (because letters were followed by varying mapping stimuli). This evidence suggests that P3b is closely related to decision processes, possibly reflecting reactivation of stimulus‐response links.     

Influence of odor cueing on the retrieval processes for autobiographical memories

This study investigated the influence of odor cueing on the retrieval process for autobiographical memories. In Experiment 1, forty two participants were asked to retrieve autobiographical memories in response to a label cue only, or a label cue with a congruent odor cue, or label cue with an incongruent odor cue. The results showed that in the label cue only condition and the incongruent odor cue condition, the latency with a concurrent task was slower than with no concurrent task. However, this was not observed in the congruent odor cue condition. In order to verify the results of Experiment 1, in Experiment 2, twenty participants were investigated with regard to autobiographical memories cued by odors having a high or low rate of identification. The results showed that memories cued by odors with a high rate of identification were retrieved faster. These results suggest that dual processing by odor and label promotes retrieval processes for autobiographical memories.     

Focused attention modulates visual responses in the primate prefrontal cortex

Several current models propose an important role of the prefrontal cortex (PFC) in attention. To test the effects of attention in PFC, we recorded from PFC neurons in monkeys performing a task in which they had to attend to one hemifield and wait for a single stimulus that matched a previously presented cue. Neurons exhibited a slight decrease in their initial response and an enhanced activity late in the response to a stimulus at the cued location. The data demonstrate attentional effects on the activity of PFC neurons but they also show that single visual stimuli are initially represented in the activity of PFC neurons even when they are behaviorally irrelevant.     

Intensity expectation modifies gustatory evoked potentials to sweet taste: Evidence of bidirectional assimilation in early perceptual processing

Expectations can affect subjective sensory and hedonic ratings of tastes, but it is unclear whether they also shape sensory experience at a perceptual level. The neural correlates of the taste‐expectancy relationship were explored through EEG analysis. Using a trial‐by‐trial cueing paradigm, lingual delivery of 0.05 M or 0.3 M sucrose solutions was preceded by congruent or incongruent visual cues designed to promote anticipation of either a low‐sweet or high‐sweet solution. When participants were cued to expect low‐sweet, but received high‐sweet (incongruent cue), intensity ratings for high‐sweet decreased. Likewise, expectation of high‐sweet increased intensity ratings of low‐sweet solutions. Taste‐dependent, right central‐parietal gustatory ERPs were detected, with greater P1 (associated with greater right insula activation) and P2 peak amplitudes for high‐sweet tastes. Valid cue‐taste pairings led to specific reduced right‐lateralized N400 responses (associated with an attenuation in right insula activation) compared with invalid cue‐taste pairings. Finally, P1 amplitudes following invalidly cued low‐sweet tastes closely matched those generated by expected high‐sweet tastes, and P1 amplitudes for invalidly cued high‐sweet tastes resembled those generated by low‐sweet tastes. We conclude that, as well as modifying subjective ratings toward the anticipated intensity level, expectations affect cortical activity in a top‐down manner to induce bidirectional assimilation in the early perceptual processing of sweet taste and modulate N400 ERP components not previously associated with gustatory stimulation.     

Support for the interruption and protection hypotheses of prepulse inhibition of startle: Evidence from a modified Attention Network Test

The startle response may interrupt information processing (interruption hypothesis), and prepulse inhibition of startle (PPI) may protect that processing from interruption (protection hypothesis). These hypotheses were tested by measuring startle eyeblinks during an Attention Network Test (ANT), a combined flanker and cue reaction time (RT) task that measures the efficiency of multiple attentional networks. ANT trials with and without startle stimuli presented in the interval between the visual cue (prepulse) and target were compared. Results showed that the startle stimulus served as an alerting stimulus, speeding RT in the ANT. However, this reaction time speeding was most pronounced on trials with no startle response (100% PPI). This suggests that the alerting effect of the startle stimulus was attenuated by the startle response, and that PPI decreased the degree of this interference, in support of the interruption and protection hypotheses.     

Age-dependent impairment of auditory processing under spatially focused and divided attention: An electrophysiological study

By using event-related potentials (ERPs) the present study examines if age-related differences in preparation and processing especially emerge during divided attention. Binaurally presented auditory cues called for focused (valid and invalid) or divided attention to one or both ears. Responses were required to subsequent monaurally presented valid targets (vowels), but had to be suppressed to non-target vowels or invalidly cued vowels. Middle-aged participants were more impaired under divided attention than young ones, likely due to an age-related decline in preparatory attention following cues as was reflected in a decreased CNV. Under divided attention, target processing was increased in the middle-aged, likely reflecting compensatory effort to fulfill task requirements in the difficult condition. Additionally, middle-aged participants processed invalidly cued stimuli more intensely as was reflected by stimulus ERPs. The results suggest an age-related impairment in attentional preparation after auditory cues especially under divided attention and latent difficulties to suppress irrelevant information.     

Control of voluntary and reflexive saccades

The latency of 'reflexive' saccades (made in response to peripheral visual stimuli) was compared to that of 'voluntary' saccades performed in anti-saccade and symbolically cued paradigms. Manipulation of visual events at fixation was carefully controlled across all conditions. Reflexive saccade latency was significantly faster than the latency of all forms of voluntary saccades. Importantly, the latency of saccades made after presentation of a symbolic cue at central fixation (voluntary arrow-cue condition) was greater than that made in the anti-saccade paradigm that requires suppression of a reflexive response. It is suggested that the increase in latency of saccades made in the voluntary arrow-cue condition may reflect differences in programming a 'When' trigger signal for saccades made in the absence of a peripheral stimulus.