Cortical Networking Research Articles

Neuroplasticity in Motor Learning Under Variable and Constant Practice Conditions-Protocol of Randomized Controlled Trial.

BackgroundThere is numerous literature on mechanisms underlying variability of practice advantages. Literature includes both behavioral and neuroimaging studies. Unfortunately, no studies are focusing on practice in constant conditions to the best of our knowledge. Hence it is essential to assess possible differences in mechanisms of neuroplasticity between constant vs. variable practice conditions. The primary objectives of the study described in this protocol will be: (1) to determine the brain’s structural and functional changes following constant and variable practice conditions in motor learning (structural and functional magnetic resonance imaging, MRI); (2) to determine the EEG activation and connectivity between cognitive, sensory, and motor cerebral cortex areas (central, temporal, parietal, occipital) in constant and variable practice conditions and as a function of practice time.MethodsThe study will follow the interventional (experimental) design with two arms (parallel groups). Fifty participants will be randomly assigned to two groups practicing in constant (CG) and variable conditions (VG). CG will be practicing only one pattern of step isometric contractions during unimanual index finger abduction, i.e., 90 trials in all training sessions, whereas VG will practice three different patterns. Each will be practiced 30 times per session in variable conditions. Resting-state fMRI, EEG (cortical networking), and motor task proficiency will be examined before (pre-) and after practice (post- and retentions tests).DiscussionFindings will enhance our understanding of structural and functional neural changes following practice in constant and variable conditions. Therefore, the study can be considered pure (basic) research (clinical research in healthy individuals).Clinical Trial RegistrationStudy registered at clinicaltrials.gov (ID# NCT04921072) on 9 June 2021. Last version update: 21 December 2021.The protocol has been prepared according to the complete SPIRIT checklist (http://www.spirit-statement.org/), although the item order has been modified in order to comply with the manuscript structure.

Haemodynamic activity characterization of resting state networks by fractal analysis and thalamocortical morphofunctional integrity in chronic migraine

BackgroundChronic migraine (CM) can be associated with aberrant long-range connectivity of MRI-derived resting-state networks (RSNs). Here, we investigated how the fractal dimension (FD) of blood oxygenation level dependent (BOLD) activity may be used to estimate the complexity of RSNs, reflecting flexibility and/or efficiency in information processing in CM patients respect to healthy controls (HC).MethodsResting-state MRI data were collected from 20 untreated CM without history of medication overuse and 20 HC. On both groups, we estimated the Higuchi’s FD. On the same subjects, fractional anisotropy (FA) and mean diffusivity (MD) values of bilateral thalami were retrieved from diffusion tensor imaging and correlated with the FD values.ResultsCM showed higher FD values within dorsal attention system (DAS) and the anterior part of default-mode network (DMN), and lower FD values within the posterior DMN compared to HC. Although FA and MD were within the range of normality, both correlated with the FD values of DAS.ConclusionsFD of DAS and DMN may reflect disruption of cognitive control of pain in CM. Since the normal microstructure of the thalamus and its positive connectivity with the cortical networking found in our CM patients reminds similar results obtained assessing the same structures but with the methods of neurophysiology, in episodic migraine during an attack, this may be yet another evidence in supporting CM as a never-ending migraine attack.

Physical Fitness and Apolipoprotein E Genotype Influence Cortical Networking and Intelligence in Adolescents

This study examined the interactive effect of physical fitness and Apolipoprotein e4 on intelligence and cortical networking in adolescents. Participants were middle school students consisting of 10 and 8 high- and low-fit e4 carriers (e4+), respectively, and 14 and 10 high- and low-fit non-carriers (e4-), respectively. Inter- and intra-hemispheric coherences were calculated to examine cortico-cortical communication during intelligence test. Coherence in low-fit e4+ was lower than in high-fit e4+, while coherence in low-fit e4- was similar to or higher than in high-fit e4-. the presence of the e4 allele can decrease neural networking 50-60 years before Alzheimer's disease onset: however, physical fitness may compensate for the negative impact of genotype. Moreover, the beneficial effects of physical fitness may differ depending on functional states of the adolescent brain according to the presence of the e4 allele.

Human cortical networking by probabilistic and frequency-specific coupling

Large-scale cortical networking patterns have been established based on the correlation of slow fluctuations of resting fMRI signals. However, the electrophysiological mechanism of cortical networking remained to be elucidated. With large-scale human ECoG recording, we developed a novel approach for functional network parcellation on the basis of probabilistic co-activation of cortical sites in spatio-temporal microstates. The parcellated networks were verified by electrical cortical stimulation (ECS) and somatosensory evoked potentials recording, which showed significantly higher accuracy than the traditional long-term correlation method. This provides direct electrophysiological evidence supporting the dynamic nature of cortical networking. Further analysis revealed that the brain-wide connectivity is likely established on the coupling of ECoG power envelop over a common carrier frequency ranging from alpha to low-beta (8–32Hz). Surprisingly, the cortical networking pattern over this specific frequency was found to be consistent across various tasks, which resembles the resting networks. The high similarity between the above functional network parcellation and the fMRI resting network atlas in individuals also suggested the slow power-envelope coupling of band-limited neural oscillations as the electrophysiological basis of spontaneous BOLD signals. Collectively, our findings on direct human recording revealed a probabilistic and frequency specific coupling mechanism for large-scale cortical networking shared by task and resting brain.

What Does Electroencephalography Coherence Tell Us about Memory Encoding in Adolescents at High Risk of Suicide?

Background: Suicide is known to be closely related to depression, which is accompanied by cognitive decline. Objective: This study examined whether memory performance and cortical networking differ between high suicide risk and control groups depending on task difficulty. Methods: The participants were 28 high school students consisting of 14 suicide risk and 14 control subjects. Real-time electroencephalography signals were collected during a working memory task. Inter- and intrahemispheric coherences were analyzed. Results: Higher cortical networking during memory encoding was found in suicide risk adolescents compared to the control group. An increase in task difficulty heightened interhemispheric coherence. Conclusions: Higher cortical networking in suicide risk adolescents seems to reflect activation of compensatory mechanisms in an attempt to minimize behavioral decline.

Cerebral cortical networking for mental workload assessment under various demands during dual-task walking.

While several studies have examined attentional reserve (via event-related potentials) and mental effort (via EEG spectral content) from various cortical regions during dual-task walking, none have assessed changes in the magnitude of interregional (cortico-cortical) communication as a measure of mental workload. Therefore, by deploying a traditional montage of electrode sites centered over the motor planning region as well as a more comprehensive graph theory-based approach encompassing the entire scalp, this study aimed to systematically examine changes in the magnitude of functional connectivity underlying cortico-cortical communication to assess changes in mental workload under various levels of challenge. Specifically, the Weighted Phase Lag Index (WPLI) was computed to assess the changes in magnitude of functional connectivity as participants performed a cognitive task under two demands (low and high) and two conditions (seated and walking). The results revealed enhanced fronto-centro-temporo-parietal theta connectivity during dual-task walking relative to being seated as well as a reduced inhibition of fronto-centro-temporo-parieto-occipital alpha networking as the demand on the secondary cognitive task increased. Collectively, these findings may reflect greater recruitment of task relevant processes to respond to increased cognitive-motor demands and thus an elevation of mental workload in an effort to maintain performance under varying levels of challenge. This work has the potential to inform future mental workload assessment applications in patient populations, including those who employ prostheses during cognitive-motor performance under various taskdemands.

Preserved sleep microstructure in blind individuals

The loss of vision, particularly when it occurs early in life, is associated with compensatory cortical plasticity not only in the visual cortical areas, but throughout the entire brain. The absence of visual input to the retina can also induce changes in entrainment of the circadian rhythm, as light is the primary zeitgeber of the master biological clock found in the suprachiasmatic nucleus of the hypothalamus. In addition, a greater number of sleep disturbances is often reported in blind individuals. Here, we examined various electroencephalographic microstructural components of sleep, both during rapid-eye-movement (REM) sleep and non-REM (NREM) sleep, between blind individuals, including both of early and late onset, and normal-sighted controls. During wakefulness, occipital alpha oscillations were lower, or absent in blind individuals. During sleep, differences were observed across electrode derivations between the early and late blind samples, which may reflect altered cortical networking in early blindness. Despite these differences in power spectra density, the electroencephalography microstructure of sleep, including sleep spindles, slow wave activity, and sawtooth waves, remained present in the absence of vision.

Effects of Stress and Task Difficulty on Working Memory and Cortical Networking.

This study investigated interactive effects of stress and task difficulty on working memory and cortico-cortical communication during memory encoding. Thirty-eight adolescent participants (mean age of 15.7 ± 1.5 years) completed easy and hard working memory tasks under low- and high-stress conditions. We analyzed the accuracy and reaction time (RT) of working memory performance and inter- and intrahemispheric electroencephalogram coherences during memory encoding. Working memory accuracy was higher, and RT shorter, in the easy versus the hard task. RT was shorter under the high-stress (TENS) versus low-stress (no-TENS) condition, while there was no difference in memory accuracy between the two stress conditions. For electroencephalogram coherence, we found higher interhemispheric coherence in all bands but only at frontal electrode sites in the easy versus the hard task. On the other hand, intrahemispheric coherence was higher in the left hemisphere in the easy (versus hard task) and higher in the right hemisphere (with one exception) in the hard (versus easy task). Inter- and intracoherences were higher in the low- versus high-stress condition. Significant interactions between task difficulty and stress condition were observed in coherences of the beta frequency band. The difference in coherence between low- and high-stress conditions was greater in the hard compared with the easy task, with lower coherence under the high-stress condition relative to the low-stress condition. Stress seemed to cause a decrease in cortical network communications between memory-relevant cortical areas as task difficulty increased.

Inter- and Intrahemispheric EEG Coherence and Visuomotor Performance During Shooting Competition and Practice.

This study compared inter- and intrahemispheric cortical networking and visuomotor performance during practice and competition in 14 air pistol athletes (mean age of 17.8 years). Participants self-reported their competitiveness, stress, confidence, and relaxation through visual analog scales; shooting score and aiming time were measured by the SCATT program. Inter- and intrahemispheric coherences during aiming were analyzed. Under competition following the practice condition, self-reported competitiveness and stress were higher, but confidence was lower. Aiming time during competition was longer than during practice; but there were no significant shooting score differences between conditions, perhaps due to only low-grade competitive anxiety. Through coherence analysis, interhemispheric coherence during aiming was higher under competition, relative to practice. Competitive anxiety seems to result in reduced neural efficiency and regional cortical autonomy, though there was no intrahemispheric electroencephalogram coherence difference between competition and practice conditions.

Default Mode Network alterations in alexithymia: an EEG power spectra and connectivity study.

Recent neuroimaging studies have shown that alexithymia is characterized by functional alterations in different brain areas [e.g., posterior cingulate cortex (PCC)], during emotional/social tasks. However, only few data are available about alexithymic cortical networking features during resting state (RS). We have investigated the modifications of electroencephalographic (EEG) power spectra and EEG functional connectivity in the default mode network (DMN) in subjects with alexithymia. Eighteen subjects with alexithymia and eighteen subjects without alexithymia matched for age and gender were enrolled. EEG was recorded during 5 min of RS. EEG analyses were conducted by means of the exact Low Resolution Electric Tomography software (eLORETA). Compared to controls, alexithymic subjects showed a decrease of alpha power in the right PCC. In the connectivity analysis, compared to controls, alexithymic subjects showed a decrease of alpha connectivity between: (i) right anterior cingulate cortex and right PCC, (ii) right frontal lobe and right PCC, and (iii) right parietal lobe and right temporal lobe. Finally, mediation models showed that the association between alexithymia and EEG connectivity values was directed and was not mediated by psychopathology severity. Taken together, our results could reflect the neurophysiological substrate of some core features of alexithymia, such as the impairment in emotional awareness.

Cerebral-cortical networking and activation increase as a function of cognitive-motor task difficulty

Excessive increases in task difficulty typically result in marked attenuation of cognitive-motor performance. The psychomotor efficiency hypothesis suggests that poor performance is mediated by non-essential neural activity and cerebral cortical networking (inefficient cortical dynamics). This phenomenon may underlie the inverse relationship between excessive task difficulty and performance. However, investigation of the psychomotor efficiency hypothesis as it relates to task difficulty has not been conducted. The present study used electroencephalography (EEG) to examine cerebral cortical dynamics while participants were challenged with both Easy and Hard conditions during a cognitive-motor task (Tetris®). In accord with the psychomotor efficiency hypothesis, it was predicted that with increases in task difficulty, participants would demonstrate greater ‘neural effort,’ as indexed by EEG spectral power and cortical networking (i.e., EEG coherence) between the premotor (motor planning) region and sensory, executive, and motor regions. Increases in neural activation and cortical networking were observed during the Hard condition relative to the Easy condition, thus supporting the psychomotor efficiency hypothesis. To further determine the unique contributions of cognitive versus sensory-motor demands, a control experiment was conducted in which cognitive demand was increased while sensory-motor demand was held constant. This experiment revealed that regionally specific neural activation was influenced by changes in cognitive demand, whereas cortical networking to the motor planning region was sensitive only to changes in sensory-motor demand. Crucially, the present study is the first, to our knowledge, to characterize the separate impact of cognitive versus sensory-motor demands on cerebral cortical dynamics. The findings further inform the dynamics of the cortical processes that underlie the quality of cognitive-motor performance particularly with regard to task difficulty. A broader understanding of the brain and muscle interactions during varying levels of challenge may inform the design of effective training protocols aimed at optimizing cognitive-motor performance.

Neuroscience today, Florence 25–27 March 2007: foreword

The emerging of the brain complex functional patterns and large-scale organization from the properties of its neuronal constituents is a major issue in today’s neuroscience. Experiments and computational models indicate the structural and functional diversity of cortical neurons as a key issue in the understanding how the robustness of neuronal components combines with weak and flexible linkages between regulatory processes to account for the adaptive tunable dynamics, coding schemes and complexity of developed nervous systems. Research has focused in recent years on the communication codes among neurons, neuronal assemblies and networks; the neural properties and processes allowing resonance to occur; the mechanisms on function-related, transient neuronal synchronization; the signal/noise interaction; stochastic resonance phenomena; the information carried on by oscillatory signals of the brain, especially in the ‘‘gamma’’ band; etc. The variability of cortical inhibitory interneurons, interneuron networking and GABAergic sites/synapses are possibly the most conspicuous source of neuronal diversity, also enabling virtually unlimited combinatorial effects at each time point. A close scrutiny of the available computational and non-conventional models derived from e.g. invertebrate and plant biology and their extension to higher-order neuronal operations (including ‘‘cognitive’’ processes) is now in order. The international Conference ‘‘Neuroscience today: neuronal functional diversity and collective behaviors’’ has been planned in the framework of the European Community COST ACTION B27 ‘‘Electric neuronal oscillations and cognition (ENOC)’’ and took place at the Accademia dei Georgofili in Firenze (Italy), March 26–28, 2007. The main goal of the COST Action B27 (see also: http://www.manu.edu.mk/costb27) is to increase the knowledge on electric neuronal oscillations correlated to memory and attention as the basis for neuronal regulation aimed at enhancing the human performance and health. Purposes of the Conference were to focus on the integration of diverse neurons (e.g. segregated and selective for sensory input or motor organization) into networks behaving as functional assemblies, set research guidelines for the combination of (sub)cellular and system brain research, promote integrated approaches, and disseminate cultural and research programs in the framework of the COST B27 project. In this regard, the conference has provided unique opportunities to discuss new trends in neuroscience and to focus on functional neuronal diversity. Thanks are due to all the participating scientists. The available evidence and models notwithstanding, the continuum from neuronal functional diversity to collective behaviors remains to a large extent incomplete and incompletely characterized—an open question, for which no comprehensive theory appears as yet conceivable. In this respect, it is our hope that the conference and its F. T. Arecchi Universita di Firenze, Florence, Italy