Planning the potential future during multi-item visual working memory

Working memory allows us to retain visual information to guide upcoming future behavior. In line with this future-oriented purpose of working memory, recent studies have shown that action planning occurs during encoding and retention of a single visual item, for which the upcoming action is certain. We asked whether and how this extends to multi-item visual working memory, when visual representations serve the potential future. Human participants performed a visual working memory task with a memory-load manipulation (one/two/four items), and a delayed orientation-reproduction report (of one item). We measured EEG to track 15-25 Hz beta activity in electrodes contralateral to the required response hand - a canonical marker of action planning. We show an attenuation of beta activity, not only in load one (with one certain future action), but also in load two (with two potential future actions), compared to load four (with low prospective-action certainty). Moreover, in load two, potential action planning occurs regardless whether both visual items afford similar or dissimilar manual responses; and it predicts the speed of ensuing memory-guided behavior. This shows that potential action planning occurs during multi- item visual working memory, and brings the perspective that working memory helps us prepare for the potential future.

Task-specific contribution of the right posterior cerebellum to language processing in healthy individuals

Clinical and neuroscientific studies in healthy volunteers have established that the cerebellum contributes to language comprehension and production. Yet most evidence is correlational and the exact role of the cerebellum remains unclear. The aim of this study was to investigate the role of the right cerebellum in unimpaired language comprehension and production using non-invasive brain stimulation. In this double-blind, sham-controlled experiment, thirty-six healthy participants received anodal or sham transcranial direct current (tDCS) stimulation to the right cerebellum while performing a lexical decision, sentence comprehension, verbal fluency and language-unrelated control task. Results showed that anodal relative to sham tDCS caused faster manual responses in the lexical decision task. Additional exploratory analyses suggest load-specific performance modulation in the sentence comprehension and lexical decision task, with tDCS improving performance in low-load trials of the sentence comprehension task and high-load trials in the lexical decision task. Overall, our findings provide evidence for the involvement of the right posterior cerebellum in comprehension-based language tasks requiring a manual response. Further research is needed to dissociate the influence of task difficulty and timing of the underlying cognitive processes.

Eye movements through space interfere with visual processing of time-related words

When people make lexical decisions to words referring to the past or the future, they are faster when their manual responses are compatible with the mental timeline (MTL). That is, future words are responded to faster on the right than the left, while past words are responded to faster on the left than the right. This space-time congruency effect is interpreted to suggest that time words are represented along a spatial continuum that goes from left to right (past to future), at least in Western cultures that use reading-writing systems operating from left to right. All previous experiments used lateralized hand movements to register responses, which would evoke the directionality of writing. To evoke the directionality of reading, we investigated whether the space-time congruency effect would be replicated in a language task when responses were given using the eyes rather than the hand. Thus, participants were asked to make lateralized eye movements to indicate whether letter stimuli were real words or not (lexical decision). Eye movements were perturbed for responses incompatible with the direction of the MTL, both in terms of decision time and motor amplitude. These results confirm that time-related words are embodied through spatial movement in effector-independent motor networks and suggests that the spatial representation of time operates in a body-centered reference frame.

Is Face Age Mapped Asymmetrically onto Space? Insights from a SNARC-like Task

The magnitude associated with a stimulus can be spatially connoted, with relatively smaller and larger magnitudes that would be represented on the left and on the right side of space, respectively. According to recent evidence, this space–magnitude association could reflect specific brain asymmetries. In this study, we explored whether such an association can also emerge for face age, assuming that responders should represent relatively younger and older adult faces on the left and on the right, respectively. A sample of young adults performed a speeded binary classification task aimed at categorising the age of a centrally placed adult face stimulus as either younger or older than the age of a reference face. A left-side and a right-side response key were used to collect manual responses. Overall, older faces were categorised faster than younger faces, and response latencies decreased with the absolute difference between the age of the target stimulus and the age of the reference, in line with a distance effect. However, no evidence of a left-to-right spatial representation of face age emerged. Taken together, these results suggest that face age is mapped onto space differently from other magnitudes.

EEG beta-modulations reflect age-specific motor resource allocation during dual-task walking

The parallel execution of two motor tasks can lead to performance decrements in either one or both of the tasks. Age-related declines can further magnify the underlying competition for cognitive resources. However, little is known about the neural dynamics underlying motor resource allocation during dual-task walking. To better understand motor resource conflicts, this study investigated sensorimotor brain rhythms in younger and older adults using a dual-task protocol. Time-frequency data from two independent component motor clusters were extracted from electroencephalography data during sitting and walking with an additional task requiring manual responses. Button press-related desynchronization in the alpha and beta frequency range were analyzed for the impact of age (< 35 years, ≥ 70 years) and motor task (sitting, walking). Button press-related desynchronization in the beta band was more pronounced for older participants and both age groups demonstrated less pronounced desynchronizations in both frequency bands during walking compared to sitting. Older participants revealed less power modulations between sitting and walking, and less pronounced changes in beta and alpha suppression were associated with greater slowing in walking speed. Our results indicate age-specific allocations strategies during dual-task walking as well as interdependencies of concurrently performed motor tasks reflected in modulations of sensorimotor rhythms.

Pre-trial Gaze Stability Predicts Momentary Slips of Attention

Our ability to maintain focus on a task waxes and wanes. Recent research suggests that eye-tracking may be a useful tool to capture the momentary slips of attention. In this paper, we show that pre-trial gaze stability predicted momentary slips of attention on the upcoming trial. In two visual search tasks, we asked participants to stabilize their gaze on a fixation cross before the search array appeared. We recorded participants’ manual responses and eye movements as they searched for the target. We also occasionally presented thought probes to examine whether participants were mind-wandering on a subset of trials. Results from the two tasks revealed a converging pattern: lower pre-trial gaze stability predicted worse performance in the upcoming trial. Specifically, participants had longer response times, were more influenced by distractors, and inspected the target for a longer duration. Participants also reported greater mind-wandering at the end of the trial if they had low pre-trial gaze stability. Overall, these findings suggest that pre-trial gaze stability is a simple and objective measure that can predict moments of inattention, which may be used to proactively curb its negative effects before the actual task starts.

The effects of input and output modalities on language switching between Chinese and English

Language control is important for bilinguals to produce words in the right language. While most previous studies investigated language control using visual stimuli with vocal responses, language control regarding auditory stimuli and manual responses was rarely examined. In the present study, an alternating language switching paradigm was used to investigate language control mechanism under two input modalities (visual and auditory) and two output modalities (manual and vocal) by measuring switch costs in both error percentage and reaction time (RT) in forty-eight Cantonese–English early bilinguals. Results showed that higher switch costs in RT were found with auditory stimuli than visual stimuli, possibly due to shorter preparation time with auditory stimuli. In addition, switch costs in RT and error percentage could be obtained not only in speaking, but also in handwriting. Therefore, language control mechanisms, such as inhibition of the non-target language, may be shared between speaking and handwriting.

Dynamic signatures of the Eureka effect: An EEG study

The Eureka effect refers to the common experience of suddenly solving a problem. Here we study this effect in a pattern recognition paradigm that requires the segmentation of complex scenes and recognition of objects on the basis of Gestalt rules and prior knowledge. In the experiments both sensory evidence and prior knowledge were manipulated in order to obtain trials that do or do not converge towards a perceptual solution. Subjects had to detect objects in blurred scenes and signal recognition with manual responses. Neural dynamics were analyzed with high-density Electroencephalography (EEG) recordings. The results show significant changes of neural dynamics with respect to spectral distribution, coherence, phase locking, and fractal dimensionality. The Eureka effect was associated with increased coherence of oscillations in the alpha and theta band over widely distributed regions of the cortical mantle predominantly in the right hemisphere. This increase in coherence was associated with a decrease of beta band activity over parietal and central regions, and with a decrease of alpha power over frontal and occipital areas. In addition, there was a lateralized reduction of fractal dimensionality for activity recorded from the right hemisphere. These results suggest that the transition towards the solution of a perceptual task is mainly associated with a change of network dynamics in the right hemisphere that is characterized by enhanced coherence and reduced complexity. We propose that the Eureka effect requires cooperation of cortical regions involved in working memory, creative thinking, and the control of attention.

Spatiotemporal dynamics of human attention revealed by intracerebral recording

ABSTRACTAttention allows us to rapidly respond to unexpected events, a fundamental capacity for survival. We recorded brain activity from 28 individuals with a total of 1,403 intracortical contacts, while they produced faster manual responses to visual targets preceded by non-predictive attentional cues, which engage exogenous spatial attention. Using a novel spatiotemporal clustering approach, we identified three distinct brain networks: an early visual cluster; an intermediate, predominantly right-hemisphere caudal temporoparietal-prefrontal cluster, sensitive to attentional effects; and a late, predominantly left-hemisphere rostral temporoparietal-prefrontal cluster, sensitive to response-requiring targets. Activity in temporoparietal-prefrontal clusters suggested neural integration of temporally close cues and targets, and was closely related to behavioral responses. These results reveal how cortical networks govern the psychological construct of exogenous attention.One-sentence summaryThe neural basis of human exogenous attention lies in the nexus between perception and action