Electrocortical correlates of attention differentiate individual capacity in associative learning.

Associative learning abilities vary considerably among individuals, with attentional processes suggested to play a role in these variations. However, the relationship between attentional processes and individual differences in associative learning remains unclear, and whether these variations reflect in event-related potentials (ERPs) is unknown. This study aimed to investigate the relationship between attentional processes and associative learning by recording electrocortical activity of 38 young adults (18-32 years) during an associative learning task. Learning performance was assessed using the signal detection index d'. EEG topographic analyses and source localizations were applied to examine the neural correlates of attention and associative learning. Results revealed that better learning scores are associated with (1) topographic differences during early (126-148 ms) processing of the stimulus, coinciding with a P1 ERP component, which corresponded to a participation of the precuneus (BA 7), (2) topographic differences at 573-638 ms, overlapping with an increase of global field power at 530-600 ms, coinciding with a P3b ERP component and localized within the superior frontal gyrus (BA11) and (3) an increase of global field power at 322-507 ms, underlay by a stronger participation of the middle occipital gyrus (BA 19). These insights into the neural mechanisms underlying individual differences in associative learning suggest that better learners engage attentional processes more efficiently than weaker learners, making more resources available and displaying increased functional activity in areas involved in early attentional processes (BA7) and decision-making processes (BA11) during an associative learning task. This highlights the crucial role of attentional mechanisms in individual learning variability.

Interindividual variations in associative visual learning: Exploration, description, and partition of response characteristics.

Relying on existing literature to identify suitable techniques for characterizing individual differences presents practical and methodological challenges. These challenges include the frequent absence of detailed descriptions of raw data, which hinders the assessment of analysis appropriateness, as well as the exclusion of data points deemed outliers, or the reliance on comparing only extreme groups by categorizing continuous variables into upper and lower quartiles. Despite the availability of algorithmic modeling in standard statistical software, investigations into individual differences predominantly focus on factor analysis and parametric tests. To address these limitations, this application-oriented study proposes a comprehensive approach that leverages behavioral responses through the use of signal detection theory and clustering techniques. Unlike conventional methods, signal detection theory considers both sensitivity and bias, offering insights into the intricate interplay between perceptual ability and decision-making processes. On the other hand, clustering techniques enable the identification and classification of distinct patterns within the dataset, allowing for the detection of singular behaviors that form the foundation of individual differences. In a broader framework, these combined approaches prove particularly advantageous when analyzing large and heterogeneous datasets provided by data archive platforms. By applying these techniques more widely, our understanding of the cognitive and behavioral processes underlying learning can be expedited and enhanced.

Cardiorespiratory fitness modulates prestimulus EEG microstates during a sustained attention task.

Higher cardiorespiratory fitness is associated with an increased ability to perform sustained attention tasks and detect rare and unpredictable signals over prolonged periods. The electrocortical dynamics underlying this relationship were mainly investigated after visual stimulus onset in sustained attention tasks. Prestimulus electrocortical activity supporting differences in sustained attention performance according to the level of cardiorespiratory fitness have yet to be examined. Consequently, this study aimed to investigate EEG microstates 2 seconds before the stimulus onset in 65 healthy individuals aged 18-37, differing in cardiorespiratory fitness, while performing a psychomotor vigilance task. The analyses showed that a lower duration of the microstate A and a higher occurrence of the microstate D correlated with higher cardiorespiratory fitness in the prestimulus periods. In addition, increased global field power and occurrence of microstate A were associated with slower response times in the psychomotor vigilance task, while greater global explained variance, coverage, and occurrence of microstate D were linked to faster response times. Our collective findings showed that individuals with higher cardiorespiratory fitness exhibit typical electrocortical dynamics that allow them to allocate their attentional resources more efficiently when engaged in sustained attention tasks.

Electrocortical correlates of the association between cardiorespiratory fitness and sustained attention in young adults.

Cardiorespiratory fitness is thought to be positively related to sustained attention. However, the underlying mechanisms of this relationship have yet to be fully elucidated. The objective of this study was to i) explore the relationship between cardiorespiratory fitness and sustained attention in 72 young adults (18-37 years old) and ii) provide insight on the electrocortical dynamics supporting sustained attention performance in individuals differing in cardiorespiratory fitness by means of EEG topographic analyses and source localization. Behaviorally, cardiorespiratory fitness was related to faster response times and higher accuracy in the psychomotor vigilance task even when adjusting the model with confounding variables such as age, body mass index and chronic physical activity. However, there was no relationship between cardiorespiratory fitness and the classic vigilance decrement observed in the sustained attention task. At the electrocortical level, higher cardiorespiratory fitness was related to increased global field power (310-333 ms poststimulus) localized in the posterior cingulate cortex (BA 30) followed by changes in scalp topographies around the P3b ERP component (413-501 ms poststimulus), which corresponded to earlier activation of the supplementary motor areas (BA 6). This is the first study using high-density EEG, which harnesses the whole spatiotemporal dynamics of the relationship between cardiorespiratory fitness and sustained attention in young adults.

Interindividual differences in brain dynamics of early visual processes: Impact on score accuracy in the mental rotation task.

Interindividual variations in the ability to perform visuospatial mental transformations have been investigated extensively, in particular through mental rotation tasks. However, the impact of early visual processes on performance has been largely ignored. To clarify this issue, we explored the time-course of early visual processing (from 0 to 450 ms poststimulus) using event-related potentials topographic analyses. The main findings demonstrated a significant link between early attentional processes and accuracy scores occurring more than five seconds later, as well as a strong association between spatial covariance and microstate topographies exhibiting substantial gender differences. More specifically, the results indicated that, in a classical mental rotation task, the male brain expends more time processing visual-spatial information resulting in a longer bilateral positive potential at posterior-occipital sites. In comparison, the female brain initiates earlier processing of non-spatial information resulting in a faster transition from a bilateral positive potential of posterior-occipital sites to a negative potential at central-frontal sites. These findings illustrate how a more complete utilization of the spatiotemporal information contained in EEG recordings can provide important insights about the impact of early visual processes on interindividual differences, particularly across gender, and thus shed new light on alternate cognitive strategies.

Temporal regularity of cerebral activity at rest correlates with slowness of reaction times in intellectual disability.

OBJECTIVE: Intellectual disability (ID) is described as a general slowness in behavior and an inadequacy in adaptive skills. The present study examines whether behavioral slowness in ID could originate from abnormal complexity in brain signals. METHODS: Participants (N = 29) performed a reaction times (RTs) task assessing their individual information processing speeds. Half of the participants had moderate intellectual disability (intelligence quotient (IQ) < 70). Continuous electroencephalogram recording during the resting period was used to quantify brain signal complexity by approximate entropy estimation (ApEn). RESULTS: For all participants, a negative correlation between RTs and IQ was found, with longer RTs coinciding with lower IQ. This behavioral slowness in ID was associated with increased temporal regularity in electrocortical brain signals. CONCLUSIONS: Behavioral slowness in ID subjects is closely related to lower brain signal complexity. SIGNIFICANCE: Brain signal ApEn is shown to correspond with processing speed for the first time: in ID participants, the higher the regularity in brain signals at rest, the slower RTs will be in the active state. ID should be understood as a lack of lability in the cortical transition to the active state, weakening the efficiency of adaptive behavior.

A fine-grained time course investigation of brain dynamics during conflict monitoring.

The conflict monitoring model predicting higher anterior cingulate cortex (ACC) neuronal activity on incongruent trials has been recently challenged by a model predicting longer neuronal activity in incongruent trials characterized by longer RTs. To clarify this issue, brain dynamics were explored through event-related-potential (ERP) recordings during a Stroop task. We assessed differences between experimental conditions by combining complementary methods sensitive to the temporality of events including microstate, TANOVA and source localization analysis. The analysis demonstrated the same electrical dynamics only differed in duration towards the end of information processing in the incongruent condition. Specifically, the activation strength of the ACC region did not differ significantly between congruent and incongruent conditions but lasted longer in the incongruent condition. Taken together, our results support the model predicting longer neuronal activity in incongruent trials characterized by longer RTs. They highlight that brain dynamics can dramatically change through periods of interest and that caution is required when interpreting fMRI results. To conclude, these results indicate how time-sensitive measures can contribute to a better understanding of the mechanisms underlying information processing, and thus offer new venues to explore conflict monitoring.

Allocentric spatial learning and memory deficits in Down syndrome.

Studies have shown that persons with Down syndrome (DS) exhibit relatively poor language capacities, and impaired verbal and visuoperceptual memory, whereas their visuospatial memory capacities appear comparatively spared. Individuals with DS recall better where an object was previously seen than what object was previously seen. However, most of the evidence concerning preserved visuospatial memory comes from tabletop or computerized experiments which are biased toward testing egocentric (viewpoint-dependent) spatial representations. Accordingly, allocentric (viewpoint-independent) spatial learning and memory capacities may not be necessary to perform these tasks. Thus, in order to more fully characterize the spatial capacities of individuals with DS, allocentric processes underlying real-world navigation must also be investigated. We tested 20 participants with DS and 16 mental age-matched, typically developing (TD) children in a real-world, allocentric spatial (AS) memory task. During local cue (LC) trials, participants had to locate three rewards marked by local color cues, among 12 locations distributed in a 4 m × 4 m arena. During AS trials, participants had to locate the same three rewards, in absence of LCs, based on their relations to distal environmental cues. All TD participants chose rewarded locations in LC and AS trials at above chance level. In contrast, although all but one of the participants with DS exhibited a preference for the rewarded locations in LC trials, only 50% of participants with DS chose the rewarded locations at above chance level in AS trials. As a group, participants with DS performed worse than TD children on all measures of task performance. These findings demonstrate that individuals with DS are impaired at using an AS representation to learn and remember discrete locations in a controlled environment, suggesting persistent and pervasive deficits in hippocampus-dependent memory in DS.

As the world turns: short-term human spatial memory in egocentric and allocentric coordinates.

We aimed to determine whether human subjects' reliance on different sources of spatial information encoded in different frames of reference (i.e., egocentric versus allocentric) affects their performance, decision time and memory capacity in a short-term spatial memory task performed in the real world. Subjects were asked to play the Memory game (a.k.a. the Concentration game) without an opponent, in four different conditions that controlled for the subjects' reliance on egocentric and/or allocentric frames of reference for the elaboration of a spatial representation of the image locations enabling maximal efficiency. We report experimental data from young adult men and women, and describe a mathematical model to estimate human short-term spatial memory capacity. We found that short-term spatial memory capacity was greatest when an egocentric spatial frame of reference enabled subjects to encode and remember the image locations. However, when egocentric information was not reliable, short-term spatial memory capacity was greater and decision time shorter when an allocentric representation of the image locations with respect to distant objects in the surrounding environment was available, as compared to when only a spatial representation encoding the relationships between the individual images, independent of the surrounding environment, was available. Our findings thus further demonstrate that changes in viewpoint produced by the movement of images placed in front of a stationary subject is not equivalent to the movement of the subject around stationary images. We discuss possible limitations of classical neuropsychological and virtual reality experiments of spatial memory, which typically restrict the sensory information normally available to human subjects in the real world.

Brain morphology in autism and fragile X syndrome correlates with social IQ: first report from the Canadian-Swiss-Egyptian Neurodevelopmental Study.

Fragile X syndrome shares most of the behavioral phenotypic similarities with autism. How are these similarities reflected in brain morphology? A total of 10 children with autism and 7 with fragile X underwent morphological (T1) 1.5-T magnetic resonance imaging (MRI). The authors found no significant difference in total brain volumes, regional volumes, gyrification index, sulcul depth, and cerebral cortical thickness. However, children with autism showed significant decrease in the medial prefrontal bilaterally and the left anterior cingulate cortices. Regression analysis revealed positive correlation between the medial prefrontal cortical thickness and the social IQ. The authors suggest that the difference between the 2 groups in the medial prefrontal and anterior cingulate cortices thickness may entail an altered social cognitive style. Functional MRI studies directly differentiating between social indifference (autism) and social avoidance (fragile X) are needed to further characterize the spectrum of social abnormalities between these 2 groups.

Somatosensory-motor bodily representation cortical thinning in Tourette: effects of tic severity, age and gender.

INTRODUCTION: Tourette syndrome (TS) implicates the disinhibition of the cortico-striatal-thalamic-cortical circuitry (CSTC). Previous studies used a volumetric approach to investigate this circuitry with inconsistent findings. Cortical thickness may represent a more reliable measure than volume due to the low variability in the cytoarchitectural structure of the grey matter. METHODS: 66 magnetic resonance imaging scans were acquired from 34 TS subjects (age range 10-25, mean 17.19+/-4.1) and 32 normal controls (NC) (age range 10-20, mean 16.33+/-3.56). Brain morphology was assessed using the fully automated CIVET pipeline at the Montreal Neurological Institute. RESULTS: We report (1) significant cortical thinning in the fronto-parietal and somatosensory-motor cortices in TS relative to NC (p<.05); (2) TS boys showed thinner cortex relative to TS girls in the fronto-parietal cortical regions (p<.05); (3) significant decrease in the fronto-parietal mean cortical thickness in TS subjects with age relative to NC and in the pre-central cortex in TS boys relative to TS girls; (4) significant negative correlations between tic severity and the somatosensory-motor cortical thickness. CONCLUSIONS: TS revealed important thinning in brain regions particularly involved in the somatosensory/motor bodily representations which may play an important role in tics. Our findings are in agreement with Leckman et al. (1991) hypothesis stating that facial tics would be associated with dysfunction in an orofacial subset of the motor circuit, eye blinking with the occulo-motor circuit, whereas lack of inhibition to a dysfunction in the prefrontal cortex. Gender and age differences may reflect differential etiological factors, which have significant clinical relevance in TS and should be considered in developing and using diagnostic and therapeutic interventions.

Perinatal choline treatment modifies the effects of a visuo-spatial attractive cue upon spatial memory in naive adult rats.

The improvement in memory functions by choline supplementation is hypothesized to be due to increased synthesis and release of acetylcholine in the brain. We have found previously that combined pre- and postnatal choline supplementation results in long-lasting facilitation of spatial memory in juvenile rats when training was conducted in presence of a local salient cue. The present work aims to analyze the effects of peri- and postnatal choline supplementation on spatial abilities of naive adult rats. Treated rats were trained in various cued procedures of the Morris navigation task of 5 months of age. The treatment had a specific effect of reducing the escape latency of the rats when the platform was at a fixed location in space and indicated by a suspended cue. This effect was associated with an improved spatial memory when the cue and the platform were removed. In this condition, the control rats showed impaired spatial discrimination following the removal of the target cue, most likely due to an overshadowing of the distant environmental cues. This impairment was not observed in the treated rats. Further training with the suspended cue at unpredictable places in the pool revealed longer escape latencies in the control than in the treated rats suggesting that this procedure induced a selective perturbation of the normal but not of the treated rats. A special probe trial with the cue at an irrelevant location and no escape platform revealed a significant bias of the control rats towards the cue, but in treated rats towards the uncued spatial escape position. This behavioral dissociation suggests that a salient cue associated with the target induces an alternative "non spatial" guidance strategy in normal rats, with the risk of overshadowing attention towards more distant spatial cues. As a consequence, the improved escape in the presence of the cue in the treated rats is associated with a stronger memory of the spatial position following disappearance of the cue. This and previous observations suggest that a specific spatial attentional process relies on the buffering of highly salient visual cues to facilitate integration of their relative position in the environment.