EEG microstates distinguish between cognitive components of fluid reasoning.

Fluid reasoning is considered central to general intelligence. How its psychometric structure relates to brain function remains poorly understood. For instance, what is the dynamic composition of ability-specific processes underlying fluid reasoning? We investigated whether distinct fluid reasoning abilities could be differentiated by electroencephalography (EEG) microstate profiles. EEG microstates specifically capture rapidly altering activity of distributed cortical networks with a high temporal resolution as scalp potential topographies that dynamically vary over time in an organized manner. EEG was recorded simultaneously with functional magnetic resonance imaging (fMRI) in twenty healthy adult participants during cognitively distinct fluid reasoning tasks: induction, spatial relationships and visualization. Microstate parameters successfully discriminated between fluid reasoning and visuomotor control tasks as well as between the fluid reasoning tasks. Mainly, microstate B coverage was significantly higher during spatial relationships and visualization, compared to induction, while microstate C coverage was significantly decreased during spatial relationships and visualization, compared to induction. Additionally, microstate D coverage was highest during spatial relationships and microstate A coverage was most strongly reduced during the same condition. Consistently, multivariate analysis with a leave-one-out cross-validation procedure accurately classified the fluid reasoning tasks based on the coverage parameter. These EEG data and their correlation with fMRI data suggest that especially the tasks most strongly relying on visuospatial processing modulated visual and default mode network activity. We propose that EEG microstates can provide valuable information about neural activity patterns with a dynamic and complex temporal structure during fluid reasoning, suggesting cognitive ability-specific interplays between multiple brain networks.

Electrophysiological indices of interference resolution covary with individual fluid intelligence: investigating reactive control processes in a 3-back working memory task.

It has been proposed that the well-established relationship between working memory (WM) and fluid intelligence (gf) is mediated by executive mechanisms underlying interference control. The latter relies upon the integrity of a frontoparietal brain network, whose activity is modulated by general cognition. In regards to the chronology of this activation, only few EEG studies investigated the topic, although none of them examined the regional interaction or the effects of individual differences in gf. The current investigation sought at extending previous research by characterizing the EEG markers (temporal activation and regional coupling) of interference control and the effects of the individual variation in gf. To this end, we recorded the EEG activity of 33 participants while performing verbal and spatial versions of a 3-back WM task. In a separate session, participants were administered with a test of fluid intelligence. Interference-inducing trials were associated with an increased negativity in the frontal scalp region occurring in two separate time windows and probably reflecting two different stages of the underlying cognitive process. In addition, we found that scalp distribution of such activity differed among individuals, being the strongest activation of the left and right frontolateral sites related to high gf level. Finally, high- and low-gf participants showed different patterns in the modulation of regional connectivity (electrodes coherence in the range of 4.5-7.5Hz) according to changes in attention load among types of trials. Our findings suggest that high-gf participants may rely upon effective engagement and modulation of attention resources to face interference.

Common and unique neuro-functional basis of induction, visualization, and spatial relationships as cognitive components of fluid intelligence.

Neuroimaging research of fluid intelligence (Gf) has mainly focused on the neural basis of abilities explaining performance on cognitive tasks. However, the neuro-functional basis of clearly defined theoretical cognitive components underlying Gf remains unclear. Induction, visualization, and spatial relationships have the highest relevance for Gf (Carroll, 1993). Here we report a functional magnetic resonance imaging (fMRI) study exploring the neural correlates of these abilities characterized by their unidimensionality and matched for task-difficulty, as evidenced by a psychometric calibration study. Twenty-two healthy young adult females, recruited from a large sample of 300 participants, with either below- or above-average Gf abilities underwent fMRI scanning during Gf task performance. The results reveal that these tasks activate a shared frontoparietal network. Specific activations were also observed, in particular for induction and visualization. The key findings suggest that Gf comprises distinguishable cognitive abilities, but the Gf construct is associated with a common network.

Behavioural assessment of dysexecutive syndrome in Parkinson's disease without dementia: a comparison with other clinical executive tasks.

The Behavioural Assessment of the Dysexecutive Syndrome (BADS) is a neuropsychological battery developed with the intent of measuring a wide range of executive impairments. Although the psychometric characteristics of BADS have previously been investigated in distinct neurological disorders, data on its validity in Parkinson's Disease (PD) without dementia are still lacking. The principal aim of the study was to address this issue. Twenty-five non-demented PD patients and 24 demographically-matched controls were administered BADS and other commonly used executive tools. Comparisons between groups indicated that two of the six BADS subtests (Temporal Judgement and Action Program) did not have sufficient sensitivity to executive impairments. However, when we explored group-predictive capabilities among the tests, the BADS total score was the most sensitive, followed by the Tower of London (TOL). We obtained similar results when we disentangled the sensitivity of the six BADS subtests. The BADS Six Elements task was the best group predictor followed by the TOL. Our findings showed that BADS is more sensitive to executive dysfunction than some of the tools commonly used to assess this construct in PD. However, we also demonstrated that, to assess executive impairments in PD without dementia adequately, this battery should be administered in combination with the TOL.