Reduced posterior parietal cortex activation after training on a visual search task

Visual search training benefits from the integrative effect of enhanced covert attention and optimized overt eye movements

Training serves as an effective approach to improve visual search performance when the target does not automatically pop out from the distractors. In the present study, we trained participants on a conjunction visual search task and examined the training effects in behavior and eye movement. The results of Experiments 1 to 4 showed that training improved behavioral performance and reduced the number of saccades and overall scanning time. Training also increased the search initiation time before the first saccade and the proportion of trials in which the participants correctly identified the target without any saccade, but these effects were modulated by stimulus’ parameters. In Experiment 5, we simultaneously recorded eye movements and electroencephalography signals and the results revealed significant N2 posterior contralateral (N2pc) components after the stimulus onset (i.e., stimulus-locked) and before the first saccade (i.e., saccade-locked) when the search target was the trained one. These N2pc components can be considered as the neural signatures for the enhanced covert attention to the trained target. Together with the training-induced increase in functional visual field, these mechanisms could support the beneficial effects of increased search initiation time and reduced number of saccades. These findings suggest that visual search training enhanced covert attention to target and optimized overt eye movements to facilitate search performance.

Neural Efficiency in Athletes: A Systematic Review

According to the neural efficiency hypothesis (NEH), professionals have more effective cortical functions in cognitive tasks. This study is focusing on providing a systematic review of sport-related NEH studies with functional neuroimaging or brain stimulation while performing a sport-specific task, with the aim to answer the question: How does long-term specialized training change an athlete's brain and improve efficiency? A total of 28 studies (N = 829, Experimental Group n = 430) from 2001 to 2020 (Median = 2014, SD = 5.43) were analyzed and results were organized into four different sections: expert-novice samples, perceptual-cognitive tasks and neuroimaging technologies, efficiency paradox, and the cluster analysis. Researchers examined a wide range of sport-specific videos and multiple object tracking (MOT) specific to 18 different sports and utilized blood oxygenation-level dependent (BOLD) functional magnetic resonance imaging (fMRI), functional near-infrared spectroscopy (fNIRS), and electroencephalogram (EEG). Expert-novice comparisons were often adopted into investigations about the variations in general about optimal-controlled performance, neurophysiology, and behavioral brain research. Experts tended to perform at faster speeds, more accurate motor behavior, and with greater efficiency than novices. Experts report lower activity levels in the sensory and motor cortex with less energy expenditure, experts will possibly be more productive. These findings generally supported the NEH across the studies reviewed. However, an efficiency paradox and proficient brain functioning were revealed as the complementary hypothesis of the NEH. The discussion concentrates on strengths and key limitations. The conclusion highlights additional concerns and recommendations for prospective researchers aiming to investigate a broader range of populations and sports.

Waking experience modulates sleep need in mice

BACKGROUND

Homeostatic regulation of sleep is reflected in the maintenance of a daily balance between sleep and wakefulness. Although numerous internal and external factors can influence sleep, it is unclear whether and to what extent the process that keeps track of time spent awake is determined by the content of the waking experience. We hypothesised that alterations in environmental conditions may elicit different types of wakefulness, which will in turn influence both the capacity to sustain continuous wakefulness as well as the rates of accumulating sleep pressure. To address this, we compared the effects of repetitive behaviours such as voluntary wheel running or performing a simple touchscreen task, with wakefulness dominated by novel object exploration, on sleep timing and EEG slow-wave activity (SWA) during subsequent NREM sleep.

RESULTS

We find that voluntary wheel running is associated with higher wake EEG theta-frequency activity and results in longer wake episodes, as compared with exploratory behaviour; yet, it does not lead to higher levels of EEG SWA during subsequent NREM sleep in either the frontal or occipital derivation. Furthermore, engagement in a touchscreen task, motivated by food reward, results in lower SWA during subsequent NREM sleep in both derivations, as compared to exploratory wakefulness, even though the total duration of wakefulness is similar.

CONCLUSION

Overall, our study suggests that sleep-wake behaviour is highly flexible within an individual and that the homeostatic processes that keep track of time spent awake are sensitive to the nature of the waking experience. We therefore conclude that sleep dynamics are determined, to a large degree, by the interaction between the organism and the environment.

Functional connectivity at rest captures individual differences in visual search

Brain functional connectivity is supposed to capture personal and lifetime learning experiences and contribute to generating individual differences in cognitive abilities. We tested this possibility using the visual search task as a measure of visual information processing and the functioning of the visual attention control system. Forty-two undergraduate students completed a functional MRI study with a resting-state session and a visual search task scan. The visual attention and control systems were studied by investigating the functional connectivity of the primary visual area, the posterior parietal cortex, the dorsolateral prefrontal cortex, and the dorsal anterior cingulate cortex because these areas have been closely related to the visual search task. A pairwise resting-state functional connectivity analysis was conducted between these regions, followed by a correlation analysis with the behavioral measures from the visual search task. Results showed that higher connectivity values between the posterior parietal cortex and the dorsal anterior cingulate cortex were positively correlated with faster response speed. The posterior parietal cortex has been related to the formation of priority maps and the integration of sensory and executive information. Inhibitory control, performance monitoring during top-down cognitive tasks, and target detection have been associated with the dorsal anterior cingulate cortex. In light of these results, we suggest that a priori enhanced connectivity between these regions defines individual differences in visual information processing and the ability to adapt to cognitive demands.

Resting-state fMRI detects the effects of learning in short term: A visual search training study

Can resting-state functional connectivity (rs-FC) detect the impact of learning on the brain in the short term? To test this possibility, we have combined task-FC and rs-FC tested before and after a 30-min visual search training. Forty-two healthy adults (20 men) divided into no-contact control and trained groups completed the study. We studied the connectivity between four different regions of the brain involved in visual search: the primary visual area, the right posterior parietal cortex (rPPC), the right dorsolateral prefrontal cortex (rDLPFC), and the dorsal anterior cingulate cortex (dACC). Task-FC showed increased connectivity between the rPPC and rDLPFC and between the dACC and rDLPFC from pretraining to posttraining for both the control group and the trained group, suggesting that connectivity between these areas increased with task repetition. In rs-FC, we found enhanced connectivity between these regions in the trained group after training, especially in those with better learning. Whole brain independent component analyses did not reveal any change in main networks after training. These results imply that rs-FC may not only predict individual differences in task performance, but rs-FC might also serve to monitor the impact of learning on the brain after short periods of cognitive training, localizing them in brain areas specifically involved in training.

Volitional modulation of higher-order visual cortex alters human perception

Can we change our perception by controlling our brain activation? Awareness during binocular rivalry is shaped by the alternating perception of different stimuli presented separately to each monocular view. We tested the possibility of causally influencing the likelihood of a stimulus entering awareness. To do this, participants were trained with neurofeedback, using realtime functional magnetic resonance imaging (rt-fMRI), to differentially modulate activation in stimulus-selective visual cortex representing each of the monocular images. Neurofeedback training led to altered bistable perception associated with activity changes in the trained regions. The degree to which training influenced perception predicted changes in grey and white matter volumes of these regions. Short-term intensive neurofeedback training therefore sculpted the dynamics of visual awareness, with associated plasticity in the human brain.

Visual search task immediate training effects on task-related functional connectivity

Brain plasticity occurs over the course of the human lifetime. Learning and training modify our neuronal synapses and adapt our brain activity, from priming effects in modal areas to higher-order changes in the association cortex. The current state of the art suggests that learning and training effects might induce large-scale brain connectivity changes. Here, we used task-fMRI data and graph-based approaches to study the immediate brain changes in functional connections associated with training on a visual search task, and the individual differences in learning were studied by means of brain-behavior correlations. In a previous work, we found that trained participants improved their response speed on a visual search task by 31%, whereas the control group hardly changed. In the present study, we showed that trained individuals changed regional connections (local links) in cortical areas devoted to the specific visual search processes and to areas that support information integration, and largely modified distributed connections (distant links) linking primary visual areas to specific attentional and cognitive control areas. In addition, we found that the individuals with the most enhanced connectivity in the dorsolateral prefrontal cortex performed the task faster after training. The observed behavioral and brain connectivity findings expand our understanding of large-scale dynamic readjustment of the human brain after learning experiences.

Reading without words or target detection? A re-analysis and replication fMRI study of the Landolt paradigm

The Landolt paradigm is a visual scanning task intended to evoke reading-like eye-movements in the absence of orthographic or lexical information, thus allowing the dissociation of (sub-) lexical vs. visual processing. To that end, all letters in real word sentences are exchanged for closed Landolt rings, with 0, 1, or 2 open Landolt rings as targets in each Landolt sentence. A preliminary fMRI block-design study (Hillen et al. in Front Hum Neurosci 7:1-14, 2013) demonstrated that the Landolt paradigm has a special neural signature, recruiting the right IPS and SPL as part of the endogenous attention network. However, in that analysis, the brain responses to target detection could not be separated from those involved in processing Landolt stimuli without targets. The present study presents two fMRI experiments testing the question whether targets or the Landolt stimuli per se, led to the right IPS/SPL activation. Experiment 1 was an event-related re-analysis of the Hillen et al. (Front Hum Neurosci 7:1-14, 2013) data. Experiment 2 was a replication study with a new sample and identical procedures. In both experiments, the right IPS/SPL were recruited in the Landolt condition as compared to orthographic stimuli even in the absence of any target in the stimulus, indicating that the properties of the Landolt task itself trigger this right parietal activation. These findings are discussed against the background of behavioural and neuroimaging studies of healthy reading as well as developmental and acquired dyslexia. Consequently, this neuroimaging evidence might encourage the use of the Landolt paradigm also in the context of examining reading disorders, as it taps into the orientation of visual attention during reading-like scanning of stimuli without interfering sub-lexical information.

Cognitive Improvement and Brain Changes after Real-Time Functional MRI Neurofeedback Training in Healthy Elderly and Prodromal Alzheimer's Disease

BACKGROUND

Cognitive decline is characteristic for Alzheimer's disease (AD) and also for healthy ageing. As a proof-of-concept study, we examined whether this decline can be counteracted using real-time fMRI neurofeedback training. Visuospatial memory and the parahippocampal gyrus (PHG) were targeted.

METHODS

Sixteen healthy elderly subjects (mean age 63.5 years, SD = 6.663) and 10 patients with prodromal AD (mean age 66.2 years, SD = 8.930) completed the experiment. Four additional healthy subjects formed a sham-feedback condition to validate the paradigm. The protocol spanned five examination days (T1-T5). T1 contained a neuropsychological pre-test, the encoding of a real-world footpath, and an anatomical MRI scan of the brain. T2-T4 included the fMRI neurofeedback training paradigm, in which subjects learned to enhance activation of the left PHG while recalling the path encoded on T1. At T5, the neuropsychological post-test and another anatomical MRI brain scan were performed. The neuropsychological battery included the Montreal Cognitive Assessment (MoCA); the Visual and Verbal Memory Test (VVM); subtests of the Wechsler Memory Scale (WMS); the Visual Patterns Test; and Trail Making Tests (TMT) A and B.

RESULTS

Healthy elderly and patients with prodromal AD showed improved visuospatial memory performance after neurofeedback training. Healthy subjects also performed better in a working-memory task (WMS backward digit-span) and in the MoCA. Both groups were able to elicit parahippocampal activation during training, but no significant changes in brain activation were found over the course of the training. However, Granger-causality-analysis revealed changes in cerebral connectivity over the course of the training, involving the parahippocampus and identifying the precuneus as main driver of activation in both groups. Voxel-based morphometry showed increases in grey matter volumes in the precuneus and frontal cortex. Neither cognitive enhancements, nor parahippocampal activation were found in the control group undergoing sham-feedback.

CONCLUSION

These findings suggest that cognitive decline, either related to prodromal AD or healthy ageing, could be counteracted using fMRI-based neurofeedback. Future research needs to determine the potential of this method as a treatment tool.

Automatized smoking-related action schemata are reflected by reduced fMRI activity in sensorimotor brain regions of smokers

In the later stages of addiction, automatized processes play a prominent role in guiding drug-seeking and drug-taking behavior. However, little is known about the neural correlates of automatized drug-taking skills and drug-related action knowledge in humans. We employed functional magnetic resonance imaging (fMRI) while smokers and non-smokers performed an orientation affordance task, where compatibility between the hand used for a behavioral response and the spatial orientation of a priming stimulus leads to shorter reaction times resulting from activation of the corresponding motor representations. While non-smokers exhibited this behavioral effect only for control objects, smokers showed the affordance effect for both control and smoking-related objects. Furthermore, smokers exhibited reduced fMRI activation for smoking-related as compared to control objects for compatible stimulus-response pairings in a sensorimotor brain network consisting of the right primary motor cortex, supplementary motor area, middle occipital gyrus, left fusiform gyrus and bilateral cingulate gyrus. In the incompatible condition, we found higher fMRI activation in smokers for smoking-related as compared to control objects in the right primary motor cortex, cingulate gyrus, and left fusiform gyrus. This suggests that the activation and performance of deeply embedded, automatized drug-taking schemata employ less brain resources. This might reduce the threshold for relapsing in individuals trying to abstain from smoking. In contrast, the interruption or modification of already triggered automatized action representations require increased neural resources.

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We measured smokers and non-smokers with fMRI and a behavioral affordance task.

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Smoking paraphernalia and control objects were employed as stimuli.

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Automatized smoking schemata employ less brain resources in sensorimotor regions.

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This might reduce the motor threshold in smokers trying to abstain from smoking.

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Interruption of triggered action representations requires more neural resources.