An impaired attentional dwell time after parietal and frontal lesions related to impaired selective attention not unilateral neglect

The attentional blink, a measure of the temporal dynamics of visual processing, has been documented to be more pronounced following brain lesions that are associated with visual neglect. This suggests that, in addition to their spatial bias in attention, neglect patients may have a prolonged dwell time for attention. Here the attentional dwell time was examined in patients with damage focused on either posterior parietal or frontal cortices. In three experiments, we show that there is an abnormally pronounced attentional dwell time, which does not differ in patients with posterior parietal and with frontal lobe lesions, and this is associated with a measure of selective attention but not with measures of spatial bias in selection. These data occurred both when we attempted to match patients and controls for overall differences in performance and when a single set stimulus exposure was used across participants. In Experiments 1 and 2, requiring report of colour–form conjunctions, there was evidence that the patients were also impaired at temporal binding, showing errors in feature combination across stimuli and in reporting in the correct temporal order. In Experiment 3, requiring only the report of features but introducing task switching led to similar results. The data suggest that damage to a frontoparietal network can compromise temporal selection of visual stimuli; however, this is not necessarily related to a deficit in hemispatial visual attention but it is to impaired target selection. We discuss the implications for understanding visual selection.     

Conjoint activity of anterior insular and anterior cingulate cortex: awareness and response

There is now a wealth of evidence that anterior insular and anterior cingulate cortices have a close functional relationship, such that they may be considered together as input and output regions of a functional system. This system is typically engaged across cognitive, affective, and behavioural contexts, suggesting that it is of fundamental importance for mental life. Here, we review the literature and reinforce the case that these brain regions are crucial, firstly, for the production of subjective feelings and, secondly, for co-ordinating appropriate responses to internal and external events. This model seeks to integrate higher-order cortical functions with sensory representation and autonomic control: it is argued that feeling states emerge from the raw data of sensory (including interoceptive) inputs and are integrated through representations in conscious awareness. Correspondingly, autonomic nervous system reactivity is particularly important amongst the responses that accompany conscious experiences. Potential clinical implications are also discussed.     

Visual field asymmetries in selective attention: evidence from a modified search paradigm

The present study investigated visual field differences in selective attention. Five stimuli were briefly presented and subjects were asked to identify a predefined target. The target/distractor physical similarity varied systematically (low, medium or high) in order to encourage attentional resolving. Right/left hemifield differences were examined in Experiment 1, temporal/nasal hemifield differences in Experiment 2, and upper/lower hemifield differences in Experiment 3. Visual field differences were found only in Experiment 1 suggesting a left/right hemispheric asymmetry in selective attention. These asymmetries appear with increasing stimuli similarity, and suggest that each hemisphere gets involved when attentional selection cannot be carried out without the mode of information processing that characterizes that hemisphere. The absence of other hemifield asymmetries is not in favor of neither a subcortical, nor a specific superior occipito-parietal involvement in attentional resolving and selectivity.     

Prenatal cocaine exposure impairs selective attention: evidence from serial reversal and extradimensional shift tasks

This study assessed the effects of prenatal cocaine exposure on cognitive functioning, using an intravenous (IV) rodent model that closely mimics the pharmacokinetics seen in humans after smoking or IV injection and that avoids maternal stress and undernutrition. Cocaine-exposed males were significantly impaired on a 3-choice, but not 2-choice, olfactory serial reversal learning task. Both male and female cocaine-exposed rats were significantly impaired on extradimensional shift tasks that required shifting from olfactory to spatial cues; however, they showed no impairment when required to shift from spatial to olfactory cues. In-depth analyses of discrete learning phases implicated deficient selective attention as the basis of impairment in both tasks. These data provide clear evidence that prenatal cocaine exposure produces long-lasting cognitive dysfunction, but they also underscore the specificity of the impairment.     

Age differences in task switching and response monitoring: evidence from ERPs

This study investigates age differences in the flexible adaptation to changing demands on task switching and conflict processing. We applied a cued task-switching version of the Stroop task and manipulated the ratio of conflict trials. During task preparation, the P300 varied as a function of conflict ratio and a later positive component was larger for switch than non-switch trials. Stimulus-related conflict processing as indicated by a negativity for incompatible trials (Ni) was delayed for older adults. Moreover, the Ni varied as a function of conflict ratio and was larger for switch than for non-switch trials. Age differences were also obtained in the correct response negativity (CRN). CRN was larger on incompatible trials and this CRN-compatibility effect was enhanced when incompatible trials were infrequent in younger, but not in older adults. Our findings suggest impairments of older adults primarily in response-related conflict processing and in the flexible adaptation to changing task contexts.     

Nonspatial intermodal selective attention is mediated by sensory brain areas: evidence from event-related potentials

The present study focuses on the question of whether inter- and intramodal forms of attention are reflected in activation of the same or different brain areas. ERPs were recorded while subjects were presented a random sequence of visual and auditory stimuli. They were instructed to attend to nonspatial attributes of either auditory or visual stimuli and to detect occasional target stimuli within the attended channel. An occipital selection negativity was found for intramodal attention to visual stimuli. Visual intermodal attention was also manifested in a similar negativity. A symmetrical dipole pair in the medial inferior occipital areas could account for the intramodal effects. Dipole pairs for the intermodal attention effect had a slightly more posterior location compared to the dipole pair for the intramodal effect. Auditory intermodal attention was manifested in an early enhanced negativity overlapping with the N1 and P2 components, which was localized using a symmetrical dipole pair in the lateral auditory cortex. The onset of the intramodal attention effect was somewhat later (around 200 ms), and was reflected in a frontal processing negativity. The present results indicate that intra- and intermodal forms of attention were indeed similar for visual stimuli. Auditory data suggest the involvement of multiple brain areas.     

Shifting the focus of attention modulates amygdala and anterior cingulate cortex reactivity to emotional faces

Functional neuroimaging studies have largely established the prominence of amygdala during emotion processing and prefrontal areas such as anterior cingulate cortex (ACC) during attentional modulation. In general, emotion processing paradigms known to probe amygdala have not been adapted to recruit prefrontal areas. In this study we used a well-known perceptual face matching paradigm, designed to elicit amygdala response, and asked volunteers to shift their focus in order to recruit regions responsible for attentional control. Stimuli comprised a trio of geometric shapes (circles, rectangles, triangles) presented alongside a trio of emotional faces (angry, fear, or happy) within the same field of view, and subjects were instructed to Match Faces or Match Shapes, as a means of attending to and away from the emotional content, respectively. We observed greater amygdala reactivity to Match Faces (>Match Shapes), and greater rostral ACC response to Match Shapes (>Match Faces). Results indicate that simply and volitionally directing attention toward or away from emotional content correspondingly modulates amygdala and ACC activity.     

Attentional effects of lesions to the anterior cingulate cortex: how prior reinforcement influences distractibility

Morphological changes in the anterior cingulate cortex are found in subjects with schizophrenia, attention deficit hyperactivity disorder, and obsessive-compulsive disorder. These changes are hypothesized to underlie the impairments these individuals show on tasks that require cognitive control. The anterior cingulate cortex has previously been shown to be active in situations involving high conflict, presentation of salient, distracting stimuli, and error processing, that is, situations that occur when a shift in attention or responding is required. However, there is some uncertainty as to what specific role the anterior cingulate cortex plays in these situations. The current study used converging evidence from two behavioral paradigms to determine the effects of excitotoxic lesions in the anterior cingulate cortex on executive control. The first assay tests reversal learning, attentional set formation and shifting. The second assesses sustained attention with and without distractors. Animals with anterior cingulate cortex lesions were impaired during reinforcement reversals, discriminations that required subjects to disregard previously relevant stimulus attributes and showed a more rapid decline in attentional ability than Sham-Lesioned subjects when maintaining sustained attention for extended periods of time. These results are consistent with the hypothesis that the anterior cingulate cortex is involved in attending to stimulus attributes that currently predict reinforcement in the presence of previously relevant, salient distractors and maintaining sustained attention over prolonged time on task.     

Bilateral parietal lesions disrupt the beneficial effects of prism adaptation: evidence from a patient with optic ataxia

Prism adaptation (PA) alleviates some neglect symptoms, however, the mechanisms underlying these effects are unclear. One brain area that may be important in generating these beneficial effects is the superior parietal lobe (SPL), a region not typically damaged in neglect, and known to be important for attention, visuomotor control, and eye movements. We examined the effects of rightward PA on covert attention in CF, a patient with bilateral SPL lesions, compared to a group of controls (N = 26) who underwent sham adaptation. In contrast to previous work in neglect, there was no reduction in CF’s leftward disengage deficit, or rightward attentional bias following PA. These results suggest that the SPL plays an important role in generating the beneficial after-effects of prisms on attention. Both Laure Pisella and James Danckert have contributed equally to this work.     

Case mixing and the right parietal cortex: evidence from rTMS

We investigated the necessary role of the right parietal lobe in visual word recognition using transcranial magnetic stimulation (TMS). TMS was applied to the right posterior parietal lobe and to a control area as participants read aloud words presented either in lower case or in mIxEd-cAsE. The words were presented either with unlimited duration and high contrast (Experiment 1), or with brief presentation and low-contrast (Experiments 2 and 3). In all three experiments, TMS over the parietal area disrupted reading, and in Experiments 2 and 3 this effect was most pronounced for mIxEd-cAsE words. This suggests that the right parietal lobe mediates the recognition of words in unfamiliar formats.     

Dorsal anterior cingulate cortex shows fMRI response to internal and external error signals

In our event-related functional magnetic resonance imaging (fMRI) experiment, participants learned to select between two response options by trial-and-error, using feedback stimuli that indicated monetary gains and losses. The results of the experiment indicate that error responses and error feedback activate the same region of dorsal anterior cingulate cortex, suggesting that this region is sensitive to both internal and external sources of error information.     

Performance monitoring local field potentials in the medial frontal cortex of primates: anterior cingulate cortex

We describe intracranial local field potentials (LFP) recorded in the anterior cingulate cortex (ACC) of macaque monkeys performing a saccade countermanding task. The most prominent feature at approximately 70% of sites was greater negative polarity after errors than after rewarded correct trials. This negative polarity was also evoked in unrewarded correct trials. The LFP evoked by the visual target was much less polarized, and the weak presaccadic modulation was insufficient to control the initiation of saccades. When saccades were cancelled, LFP modulation decreased slightly with the magnitude of response conflict that corresponds to the coactivation of gaze-shifting and -holding neurons estimated from the probability of canceling. However, response time adjustments on subsequent trials were not correlated with LFP polarity on individual trials. The results provide clear evidence that error- and feedback-related, but not conflict-related, signals are carried by the LFP in the macaque ACC. Finding performance monitoring field potentials in the ACC of macaque monkeys establishes a bridge between event-related potential and functional brain-imaging studies in humans and neurophysiology studies in non-human primates.     

Electrophysiological evidence of sustained spatial attention effects over anterior cortex: Possible contribution of the anterior insula

Spatial attention can improve performance in terms of speed and accuracy; this advantage may be mediated by brain processes at both poststimulus (reactive) and prestimulus (proactive) stages. Here, we studied how visuospatial attention affects both proactive and reactive brain functions using event‐related potentials (ERPs). At reactive stage, effects of attention on parietal‐occipital components are well documented; little data are available on anterior components. Seventeen participants performed simple and discriminative response tasks, while voluntarily and steadily attending either the left or right visual hemifield throughout one block. Response speed was faster for the attended side. At ERP level, attending to one hemifield did not produce lateralization of proactive components—that is, the BP and the pN. As for poststimulus components, we confirmed the well‐known amplitude effects on the P1, N1, and P3. More interesting are results for the prefrontal components previously neglected in tasks modulating spatial attention. Previous studies suggest that these components reflect perceptual and sensory‐motor awareness (pN1 and pP1 components), and stimulus‐response mapping (pP2 component) associated to anterior insular activity. Spatial attention enhanced the pN1 and the pP1 amplitude but had no effect on the pP2. Overall, results extend knowledge on spatial attention, showing that sustained spatial attention affects the activity of anterior areas, such as the anterior insula, in addition to the known influence on occipital‐parietal areas. Top‐down spatial attention is likely mediated by increased sensory and sensory‐motor awareness for attended events; this effect is evident in reactive, not proactive, brain activity.     

Anticipatory errors after unilateral lesions of the subthalamic nucleus in the rat: evidence for a failure of response inhibition

The nature of anticipatory responding in rats with unilateral subthalamic nucleus lesions was examined. Rats were trained to respond toward visual targets that were preceded by 1 of 4 different cues. For normal rats, a cue invokes an involuntary attentional orienting that enhances processing of the target at the location of attention. The cue is also a salient stimulus to which a response must be suppressed. Therefore, this task was used to investigate possible attentional impairments, as well as the ability of a lesioned rat to suppress competing motor programs. Responding under target control was not affected by the lesion. There was an increase in anticipatory responses before target onset, which could be accounted for by a failure to inhibit contralateral responses.     

Enduring effects of prenatal cocaine exposure on selective attention and reactivity to errors: evidence from an animal model

Adult Long-Evans rats, exposed prenatally to 1 of 4 doses of cocaine (0.0,0.5,1.0, or 3.0 mg/kg iv), were tested on a 3-choice visual attention task with an olfactory distractor presented unpredictably on one third of the trials. The performance of all 3 cocaine-exposed groups was significantly more disrupted than that of controls by the presentation of distractors. Results demonstrate that prenatal cocaine exposure increases susceptibility to distractors, using a task specifically designed to measure this function. In addition, the present study revealed that individuals exposed to cocaine in utero exhibit greater performance disruption after an error than controls, in certain types of tasks. Both areas of dysfunction, impaired selective attention and impaired arousal regulation, have important functional consequences in humans, possibly affecting the school performance and social development of cocaine-exposed children.     

维持注意与选择注意具有不同的脑机制：来自事件相关电位的证据

BACKGROUND: At present, researches about attention mainly concentrate on the relationship between attention and other psychological phenomena, but studies concerning different types of attention itself (sustained attention versus selective attention) are few. OBJECTIVE: To investigate the brain mechanisms of sustained and selective attentions which have different roles in the cognitive process. METHODS: Event-related potentials (ERPs) were measured when 18 college students’ participants (half male and half female) were performing selective and sustained attention tasks. The program was written in E-Prime and displayed on a computer, and the experimental task was adapted from Karl et al. reported experimental paradigm, including selective attention and sustained attention tasks. The time of fixation point given was 500 ms, and the time of three randomly abreast pictures given was 300 ms. All the participants were asked to make rapid and accurate response as much as possible. RESULTS AND CONCLUSION: The ERPs elicited by the two attention tasks were different in the aspects of time process, wave crest and latency. The brain regions activated by the sustained attention were wider than those by selective attention. The ERPs elicited by the sustained attention mainly presents as positive waves, whereas those elicited by the selective attention were reflected as both positive and negative waves. The EPRs elicited by the sustained attention were N100 and N250, but in the metaphase, selective attention elicited the P180. These may indicate that event choice appears in the middle stage of the task. Besides, the reversion of EPRs elicited by the two attention tasks in the anterior and posterior scalp is likely to be a generality of all attentions. 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

MMN and attention: competition for deviance detection

We addressed the question of whether the mismatch negativity (MMN) event-related potential reflects an attention-independent process. Previous studies have shown that the MMN response to intensity deviation was significantly reduced or even abolished when attention was highly focused on a concurrent sound channel, whereas no conclusive evidence of attentional sensitivity has been obtained for frequency deviation. We tested a new hypothesis suggesting that competition between detection of identical deviations in attended and unattended channels and the biasing of this competition induced by the subject's task account for the observed MMN effects. In a fast-paced dichotic paradigm, we set up competition for frequency MMN and removed it for intensity MMN. We found that frequency MMN was now abolished in the unattended channel, whereas the amplitude of the intensity MMN was unaffected. These results support the competition hypothesis and suggest that selective attention in and of itself does not affect the MMN. Top-down processes can determine what information reaches the deviance-detection process when changes in multiple channels vie for the same MMN resource and one of the competing changes is relevant for the subject's task.     

Effects of selective excitotoxic lesions of the nucleus accumbens core,anterior cingulate cortex,and central nucleus of the amygdala on autoshaping performance in rats

The nucleus accumbens core (AcbC), anterior cingulate cortex (ACC), and central nucleus of the amygdala (CeA) are required for normal acquisition of tasks based on stimulus-reward associations. However, it is not known whether they are involved purely in the learning process or are required for behavioral expression of a learned response. Rats were trained preoperatively on a Pavlovian autoshaping task in which pairing a visual conditioned stimulus (CS+) with food causes subjects to approach the CS+ while not approaching an unpaired stimulus (CS-). Subjects then received lesions of the AcbC, ACC, or CeA before being retested. AcbC lesions severely impaired performance; lesioned subjects approached the CS+ significantly less often than controls, failing to discriminate between the CS+ and CS-. ACC lesions also impaired performance but did not abolish discrimination entirely. CeA lesions had no effect on performance. Thus, the CeA is required for learning, but not expression, of a conditioned approach response, implying that it makes a specific contribution to the learning of stimulus-reward associations.     

Blink reflex modification by selective attention: evidence for the modulation of 'automatic' processing

Probe stimuli which elicit activity reflexly provide a means of assessing 'top-down' effects of attentional manipulations while minimizing the perhaps insolvable problem of determining whether effects are due to post-perceptual selection or to changes in the input pathway. Parallel experiments on adults and infants presented acoustic and visual probes unpredictably while subjects attended to acoustic and visual foregrounds: Attention was indexed by heart rate deceleration. When probe and foreground modality matched, probe-elicited reflex blinks were significantly facilitated in magnitude (infants) or latency (adults) relative to reflexes elicited when probe and foreground modality mismatched. Further, facilitation was greater when modality-matching probes were presented over foregrounds judged a priori to be more 'interesting' than 'dull' foregrounds. Because acoustic and visual blink reflexes have a common efferent path, modulating effects must have occurred earlier, in modality-specific paths. As such, the results suggest that attention can influence 'automatic' sensory-perceptual analysis.     

Natural selective attention: orienting and emotion

The foundations of orienting and attention are hypothesized to stem from activation of defensive and appetitive motivational systems that evolved to protect and sustain the life of the individual. Motivational activation initiates a cascade of perceptual and motor processes that facilitate the selection of appropriate behavior. Among these are detection of significance, indexed by a late centro-parietal positivity in the event-related potential, enhanced perceptual processing, indexed by a initial cardiac deceleration, and preparation for action, indexed by electrodermal changes. Data exploring the role of stimulus novelty and significance in orienting are presented that indicate different components of the orienting response habituate at different rates. Taken together, it is suggested that orienting is mediated by activation of fundamental motivational systems that have evolved to support survival.