Visual processing is not determined solely by retinal inputs. Attentional modulation can arise when the internal attentional state (current task) of the observer alters visual processing of the same ...stimuli. This can influence visual cortex, boosting neural responses to an attended stimulus. Emotional modulation can also arise, when affective properties (emotional significance) of stimuli, rather than their strictly visual properties, influence processing. This too can boost responses in visual cortex, as for fear-associated stimuli. Both attentional and emotional modulation of visual processing may reflect distant influences upon visual cortex, exerted by brain structures outside the visual system per se. Hence, these modulations may provide windows onto causal interactions between distant but interconnected brain regions. We review recent evidence, noting both similarities and differences between attentional and emotional modulation. Both can affect visual cortex, but can reflect influences from different regions, such as fronto-parietal circuits versus the amygdala. Recent work on this has developed new approaches for studying causal influences between human brain regions that may be useful in other cognitive domains. The new methods include application of functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) measures in brain-damaged patients to study distant functional impacts of their focal lesions, and use of transcranial magnetic stimulation concurrently with fMRI or EEG in the normal brain. Cognitive neuroscience is now moving beyond considering the putative functions of particular brain regions, as if each operated in isolation, to consider, instead, how distinct brain regions (such as visual cortex, parietal or frontal regions, or amygdala) may mutually influence each other in a causal manner.
We examined visual search for color singleton targets, whose shape was discriminated. Critically, we varied the reward priority of singleton colors (correct fast performance was worth more bonus ...points for red singletons than for green singletons, or vice versa) to test whether event-related potential signatures of visual selection can be affected by distinct reward priorities for different target types, even when every target has to be selected for report. The N2pc component was earlier and larger for high- than for low-reward targets. This influence of reward on the N2pc correlated with the subject-by-subject impact of reward level on efficiency of behavioral performance. Later postselection processing was also affected by reward level. These results demonstrate that visual selection of task-relevant items is rapidly modulated by reward-related priorities, even when every target has to be selected for response.
Dorsolateral prefrontal cortex (DLPFC) is recruited during visual working memory (WM) when relevant information must be maintained in the presence of distracting information. The mechanism by which ...DLPFC might ensure successful maintenance of the contents of WM is, however, unclear; it might enhance neural maintenance of memory targets or suppress processing of distracters. To adjudicate between these possibilities, we applied time-locked transcranial magnetic stimulation (TMS) during functional MRI, an approach that permits causal assessment of a stimulated brain region's influence on connected brain regions, and evaluated how this influence may change under different task conditions. Participants performed a visual WM task requiring retention of visual stimuli (faces or houses) across a delay during which visual distracters could be present or absent. When distracters were present, they were always from the opposite stimulus category, so that targets and distracters were represented in distinct posterior cortical areas. We then measured whether DLPFC-TMS, administered in the delay at the time point when distracters could appear, would modulate posterior regions representing memory targets or distracters. We found that DLPFC-TMS influenced posterior areas only when distracters were present and, critically, that this influence consisted of increased activity in regions representing the current memory targets. DLPFC-TMS did not affect regions representing current distracters. These results provide a new line of causal evidence for a top-down DLPFC-based control mechanism that promotes successful maintenance of relevant information in WM in the presence of distraction.
Incoming signals from different sensory modalities are initially processed in separate brain regions. But because these different signals can arise from common events or objects in the external ...world, integration between them can be useful. Such integration is subject to spatial and temporal constraints, presumably because a common source is more likely for information arising from around the same place and time. This review focuses on recent neuroimaging data concerning spatial aspects of multisensory integration in the human brain. These findings indicate not only that multisensory integration involves anatomical convergence from sensory-specific (‘unimodal’) cortices into multisensory (‘heteromodal’) brain areas, but also that multisensory spatial interactions can affect even so-called ‘unimodal’ brain regions. Such findings call for a revision of traditional assumptions about multisensory processing in the brain.
Research on attention is concerned with selective processing of incoming sensory information. To some extent, our awareness of the world depends on what we choose to attend, not merely on the ...stimulation entering our senses. British psychologists have made substantial contributions to this topic in the past century. Celebrated examples include Donald Broadbent's filter theory of attention, which set the agenda for most subsequent work; and Anne Treisman's revisions of this account, and her later feature‐integration theory. More recent contributions include Alan Allport's prescient emphasis on the relevance of neuroscience data, and John Duncan's integration of such data with psychological theory. An idiosyncratic but roughly chronological review of developments is presented, some practical and clinical implications are briefly sketched, and future directions suggested. One of the biggest changes in the field has been the increasing interplay between psychology and neuroscience, which promises much for the future. A related change has been the realization that selection attention is best thought of as a broad topic, encompassing a range of selective issues, rather than as a single explanatory process.
The visual context of seeing the body can reduce the experience of acute pain, producing a multisensory analgesia. Here we investigated the neural correlates of this "visually induced analgesia" ...using fMRI. We induced acute pain with an infrared laser while human participants looked either at their stimulated right hand or at another object. Behavioral results confirmed the expected analgesic effect of seeing the body, while fMRI results revealed an associated reduction of laser-induced activity in ipsilateral primary somatosensory cortex (SI) and contralateral operculoinsular cortex during the visual context of seeing the body. We further identified two known cortical networks activated by sensory stimulation: (1) a set of brain areas consistently activated by painful stimuli (the so-called "pain matrix"), and (2) an extensive set of posterior brain areas activated by the visual perception of the body ("visual body network"). Connectivity analyses via psychophysiological interactions revealed that the visual context of seeing the body increased effective connectivity (i.e., functional coupling) between posterior parietal nodes of the visual body network and the purported pain matrix. Increased connectivity with these posterior parietal nodes was seen for several pain-related regions, including somatosensory area SII, anterior and posterior insula, and anterior cingulate cortex. These findings suggest that visually induced analgesia does not involve an overall reduction of the cortical response elicited by laser stimulation, but is consequent to the interplay between the brain's pain network and a posterior network for body perception, resulting in modulation of the experience of pain.
Neural networks underlying visual perception exhibit oscillations at different frequencies (e.g., 1–6). But how these map onto distinct aspects of visual perception remains elusive. Recent ...electroencephalography data indicate that theta or beta frequencies at parietal sensors increase in amplitude when conscious perception is dominated by global or local features, respectively, of a reversible visual stimulus 6. But this provides only correlative, noninterventional evidence. Here we show via transcranial magnetic stimulation (TMS) interventions that short rhythmic bursts of right-parietal TMS at theta or beta frequency can causally benefit processing of global or local levels, respectively, for hierarchical visual stimuli, especially in the context of salient incongruent distractors. This double dissociation between theta and beta TMS reveals distinct causal roles for particular frequencies in processing global versus local visual features.
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► Rhythmic TMS causally targets particular brain processes in a frequency-specific way ► Right-parietal TMS at beta-frequency selectively enhances local visual processing ► Right-parietal TMS at theta-frequency selectively enhances global visual processing ► Rhythmic TMS is a powerful tool for frequency-specific interventions in brain function
There has been a recent and dramatic growth of interest in the psychological and neural mechanisms of multisensory integration between different sensory modalities. Much of this recent research has ...focused specifically on how multisensory representations of body parts and of the ‘peripersonal’ space immediately around them, are constructed. Research has also focused on how this may lead to multisensorially determined perceptions of body parts, to action execution, and even to attributions of agency and self-ownership for the body parts in question. Converging evidence from animal and human studies suggests that the primate brain constructs various body-part-centred representations of space, based on the integration of visual, tactile and proprioceptive information. These representations can plastically change following active tool-use that extends reachable space and also modifies the representation of peripersonal space. These new results indicate that a modern cognitive neuroscience approach to the classical concept of the ‘body schema’ may now be within reach.
It is well established that the frontal eye-fields (FEF) in the dorsal attention network (DAN) guide top-down selective attention. In addition, converging evidence implies a causal role for the FEF ...in attention shifting, which is also known to recruit the ventral attention network (VAN) and fronto-striatal regions. To investigate the causal influence of the FEF as (part of) a central hub between these networks, we applied thetaburst transcranial magnetic stimulation (TBS) off-line, combined with functional magnetic resonance (fMRI) during a cued visuo-spatial attention shifting paradigm.
We found that TBS over the right FEF impaired performance on a visual discrimination task in both hemifields following attention shifts, while only left hemifield performance was affected when participants were cued to maintain the focus of attention. These effects recovered ca. 20min post stimulation. Furthermore, particularly following attention shifts, TBS suppressed the neural signal in bilateral FEF, right inferior and superior parietal lobule (IPL/SPL) and bilateral supramarginal gyri (SMG). Immediately post stimulation, functional connectivity was impaired between right FEF and right SMG as well as right putamen. Importantly, the extent of decreased connectivity between right FEF and right SMG correlated with behavioural impairment following attention shifts.
The main finding of this study demonstrates that influences from right FEF on SMG in the ventral attention network causally underly attention shifts, presumably by enabling disengagement from the current focus of attention.
•Thetaburst stimulation to the right FEF temporarily impairs bilateral attention shifts.•Lateralised behavioural deficits in the contralateral hemifield are observed when cued to maintain attention.•These effects recover ca. 20min post stimulation.•During shifts, neural activity is suppressed following right FEF TBS in the dorsal attention network and supramarginal gyri.•Influences from right FEF to SMG causally underlie attention shifts, presumably by enabling disengagement from current focus.
Transcranial magnetic stimulation (TMS) is increasingly used in Cognitive Neuroscience to study functional contributions of a stimulated brain region to cognitive and perceptual processing. ...TMS-related behavioural effects are often interpreted as reflecting selective disruption of processing primarily within the stimulated region itself. This approach is now being extended by studies that combine TMS with concurrent neuroimaging measures, such as functional magnetic resonance imaging (fMRI). We discuss some recent combined TMS–fMRI studies and their implications for TMS investigations of cognition and perception. An emerging theme is that TMS does not affect only the stimulated region, but can also influence remote brain areas interconnected with the stimulation site. Such ‘network’ effects of TMS can be anatomically specific, but also context-dependent, changing with the current functional state of the targeted network rather than simply reflecting just fixed, context-invariant anatomical connectivity. Perceptual and behavioural effects of TMS may correspondingly involve TMS influences on remote interconnected brain regions, not solely on the stimulated region itself. Thus, TMS can now be used to study the consequences of functional interactions between the stimulated region and other parts of the network. This may lead beyond strictly modular views of brain function, that emphasize functional properties of single brain areas, towards new perspectives on how functional interactions between remote but interconnected brain regions may support perception and cognition.
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