Anterior prefrontal cortex contributions to attention control

In a series of event-related functional magnetic resonance studies, we consistently found activation in anterior prefrontal cortex related to visual dimension changes in singleton search tasks. I review these data and discuss possible contributions of anterior prefrontal cortex to attention control in visual search. It is proposed that anterior prefrontal cortex may detect task-relevant stimulus changes when the target is ambiguously defined. This process may occur in the absence of awareness and may support visual dimension weighting by inhibition of the old relevant dimension in favor of the new dimension.     

Temporal contextual cuing of visual attention

Previous research has shown how spatial attention is guided to a target location, but little is understood about how attention is allocated to an event in time. The authors introduce a paradigm to manipulate the sequential structure of visual events independent of responses. They asked whether this temporal context could be implicitly learned and used to guide attention to a relative point in time or location, or both, in space. Experiments show that sequentially structured event durations, event identities, and spatiotemporal event sequences can guide attention to a point in time as well as to a target event's identity and location. Cuing was found to rely heavily on the element immediately preceding the target, although cuing from earlier items also was evident. Learning was implicit in all cases. These results show that the sequential structure of the visual world plays an important role in guiding visual attention to target events.     

初级视觉皮层在注意振荡中的作用

注意离散性是注意间歇性地采集外界信息的特性, 这种特性在行为中的表现被称为注意振荡。尽管有研究使用经典的线索靶子范式和视觉搜索范式发现行为数据中存在注意振荡, 证明了注意是离散的, 但其相应的神经机制, 即注意离散性与哪些脑区有关, 尚不明确。研究采用高时间分辨率的线索靶子范式和双眼分视技术, 基于人眼视觉通路的解剖学特性, 比较了线索靶子出现在双眼(实验1)、同眼和异眼(实验2)条件下的注意振荡, 考察初级视觉皮层对注意振荡的影响。结果发现：1)双眼分视会对注意振荡发生的频段产生影响, 非双眼分视条件下, 注意振荡出现在低频(2 Hz和8 Hz)。而双眼分视条件下, 注意振荡则出现在更高的频段(12.5 Hz)。2)无论线索靶子出现在同眼还是异眼, 注意振荡的频段无显著差异。结果表明V1区双眼视觉通路或者更高级的视觉区可能参与注意振荡, 为探明注意振荡的神经机制提供了重要的行为学证据。     

Implicit memory influences the allocation of attention in visual cortex

The visual environment is highly regular, with particular objects frequently appearing in specific locations. Previous studies of visual search have shown that people take advantage of such regularities, detecting targets more quickly when they appear at a predictable location within a given spatial configuration. Moreover, this effect depends on implicit rather than explicit memory for the configurations. These studies have suggested that implicit long-term memory for contextual information influences the allocation of attention, modulating the flow of information through visual cortex. The present study used event-related potentials to provide the first direct support for this proposal. We suggest that this guidance of attention by implicit memory is important in the natural environment because it allows environmental regularities to influence perception without the intervention of limited-capacity conscious processes.     

The role of the human extrastriate visual cortex in mirror symmetry discrimination: a TMS-adaptation study

The human visual system is able to efficiently extract symmetry information from the visual environment. Prior neuroimaging evidence has revealed symmetry-preferring neuronal representations in the dorsolateral extrastriate visual cortex; the objective of the present study was to investigate the necessity of these representations in symmetry discrimination. This was accomplished by the use of state-dependent transcranial magnetic stimulation, which combines the fine resolution of adaptation paradigms with the assessment of causality. Subjects were presented with adapters and targets consisting of dot configurations that could be symmetric along either the vertical or horizontal axis (or they could be non-symmetric), and they were asked to perform a symmetry discrimination task on the targets while fixating the center of the screen. TMS was applied during the delay between the adapter and the test stimulus over one of four different sites: Left or Right V1/V2, or left or right dorsolateral extrastriate cortex (DLO). TMS over both Left and Right DLO reduced the adaptation effect in detecting vertical and horizontal symmetry, although the Left DLO effect on horizontal symmetry and the Right DLO effect on both vertical and horizontal symmetry were present only when considering subjects who showed a behavioral adaptation effect in the baseline No-TMS condition. Application of TMS over the Left or Right V1/V2 did not modulate the adaptation effect. Overall, these data suggest that both the Left and Right DLO contain neuronal representations tuned to mirror symmetry which play a causal role in symmetry discrimination.     

跨通道语义启动对视觉注意的影响

采用生活中的真实客体,考察了跨通道语义相关性对视觉注意的影响以及跨通道促进的时程。结合启动范式和点探测范式,实验1发现在听觉启动600ms后,被试对高相关视觉刺激的反应比对低相关刺激的反应更快,而在视觉启动下没有发现启动效应。实验2发现在启动刺激呈现900ms后跨通道启动效应消失。研究证明了基于先前经验的视、听语义相关能够促进视觉的选择性注意。     

Persistent activity in the prefrontal cortex during working memory

The dorsolateral prefrontal cortex (DLPFC) plays a crucial role in working memory. Notably, persistent activity in the DLPFC is often observed during the retention interval of delayed response tasks. The code carried by the persistent activity remains unclear, however. We critically evaluate how well recent findings from functional magnetic resonance imaging studies are compatible with current models of the role of the DLFPC in working memory. These new findings suggest that the DLPFC aids in the maintenance of information by directing attention to internal representations of sensory stimuli and motor plans that are stored in more posterior regions.     

ERPs associated with visual duration discriminations in prefrontal and parietal cortex

An event-related potentials (ERP) study was undertaken to examine the role of prefrontal and parietal association cortices on selective attention and short-term memory functions in a duration discrimination task. Subjects performed better when discriminating the first stimulus relative to the second and not the reverse. Two contingent negative variations (CNV) were obtained for each stimulus duration at prefrontal regions, as well as two P300s at parietal regions. The CNV(S1) component recorded during the first stimulus (S1) appeared to be involved in selective attention at bilateral sites, while the P300(S1) component in the left hemisphere may be implicated in retaining it. The CNV(S2) wave, displayed during the second stimulus (S2), at bilateral sites and the right-sided P300(S2) wave seem to be implicated in working memory. The results indicate that recorded activity at prefrontal and parietal association cortices is tightly linked to task parameters and behavioral performances.     

Serial deployment of attention during visual search

This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks.     

右侧背外侧前额叶在视觉工作记忆中的因果性作用

以往的影像学研究表明右侧背外侧前额叶皮层(DLPFC)在视觉工作记忆中发挥重要作用, 然而缺乏因果性的证据。本研究旨在考察右侧DLPFC的激活与视觉工作记忆容量的因果关系, 并探讨这一关系受到记忆负荷的调节及其神经机制。被试接受经颅直流电刺激之后完成视觉工作记忆变化检测任务, 根据被试在虚假刺激情况下从负荷4到负荷6任务记忆容量的增量将被试分为低记忆增长潜力组(简称低潜力组)和高记忆增长潜力组(简称高潜力组), 结果发现正性电刺激右侧DLPFC相对于虚假电刺激显著提升了高潜力组被试在低记忆负荷(负荷4)下的记忆容量及其对应的提取阶段的脑电指标SPCN成分。表明右侧DLPFC在视觉工作记忆的提取阶段发挥重要的因果性作用; 正性经颅直流电刺激右侧DLPFC可使工作记忆容量高潜力被试获得更多的脑活动增益, 并导致更好的行为提升效果。     

The role of prefrontal cortex during tests of episodic memory

Recent studies of episodic memory using functional neuroimaging techniques indicate that right prefrontal cortex (PFC) is activated while people remember events. Our review suggests that left PFC is also activated during remembering, depending on the reflective demands of the task. As more, or more complex, reflective processes are required (e.g. when criteria for evaluation have to be established and maintained, when the complexity of the evaluation required increases, and when retrieval of additional information is required beyond that activated by an initial cue), left PFC activity is more likely to occur. Our `cortical asymmetry of reflective activity' (CARA) hypothesis summarizes available findings and suggests directions for future research.     

Behold the voice of wrath: cross-modal modulation of visual attention by anger prosody

Emotionally relevant stimuli are prioritized in human information processing. It has repeatedly been shown that selective spatial attention is modulated by the emotional content of a stimulus. Until now, studies investigating this phenomenon have only examined within-modality effects, most frequently using pictures of emotional stimuli to modulate visual attention. In this study, we used simultaneously presented utterances with emotional and neutral prosody as cues for a visually presented target in a cross-modal dot probe task. Response times towards targets were faster when they appeared at the location of the source of the emotional prosody. Our results show for the first time a cross-modal attentional modulation of visual attention by auditory affective prosody.     

Medial prefrontal cortex is selectively involved in response selection using visual context in the background

The exact roles of the medial prefrontal cortex (mPFC) in conditional choice behavior are unknown and a visual contextual response selection task was used for examining the issue. Inactivation of the mPFC severely disrupted performance in the task. mPFC inactivations, however, did not disrupt the capability of perceptual discrimination for visual stimuli. Normal response selection was also observed when nonvisual cues were used as conditional stimuli. The results strongly suggest that the mPFC is not necessarily involved in the inhibition of response or flexible response selection in general, but is rather critical when response selection is required conditionally using visual context in the background.     

Self-recognition and the right prefrontal cortex

Although the anatomical and functional substrates subserving face recognition have been subject to extensive investigation, the underpinnings of self-face recognition are not well understood. Given the evidence that own-face recognition has been demonstrated by a select number of species, it is intriguing to speculate whether self-face recognition is accomplished via a 'self-network' or simply a 'face-network' within the brain. Furthermore, the relationship of self-recognition to other self-processes, such as self-evaluation and autobiographical retrieval, are not clearly defined. However, data from fMRI, ERPs and repetitive transcranial magnetic stimulation as well as from split-brain studies and patients with focal lesions, indicate that the prefrontal cortex, with possible right hemisphere lateralization, may be a preferential component in self-recognition. Studies using these methods, as well as PET, have indicated that the self-processes of self-evaluation and autobiographical memory preferentially engage networks within the right fronto-temporal region. Although it is highly improbable that there is a 'self-recognition' or 'self' center, it appears that there may be a bias for the processing of 'self' within the right prefrontal cortex.     

The locus of spatial attention during the temporal integration of visual memories and visual percepts

Temporal integration is a process by which two serially presented visual stimuli are mentally integrated to form a composite representation. In the present research, we explored how spatial selective attention is used during the delay separating stimuli, in order to determine the contents of spatial working memory in this task. A two-task situation was created. On the primary task, two dot arrays were serially presented within a grid, leaving one space empty, which subjects identified. On the secondary task, instead of the second array, a discrimination probe was presented. Integration accuracy increased through delays of 1,500 msec, revealing an estimate of the time required to form an optimal memory trace for integration. Once the memory trace was formed (but not before), response time to the probe was faster if it was presented in a location previously occupied by a dot from Array 1. This indicates that during the delay separating the arrays, the subjects assigned spatial attention to the locations occupied by the first array and actively maintained the leading array in working memory. Implications for theories of visual processing and memory are discussed.