Synchronization of fronto-parietal beta and theta networks as a signature of visual awareness in neglect.

In the neglect syndrome, the perceptual deficit for contra-lesional hemi-space is increasingly viewed as a dysfunction of fronto-parietal cortical networks, the disruption of which has been described in neuroanatomical and hemodynamic studies. Here we exploit the superior temporal resolution of electroencephalography (EEG) to study dynamic transient connectivity of fronto-parietal circuits at early stages of visual perception in neglect. As reflected by inter-regional phase synchronization in a full-field attention task, two functionally distinct fronto-parietal networks, in beta (15-25Hz) and theta (4-8Hz) frequency bands, were related to stimulus discrimination within the first 200 ms of visual processing. Neglect pathology was specifically associated with significant suppressions of both beta and theta networks engaging right parietal regions. These connectivity abnormalities occurred in a pattern that was distinctly different from what was observed in right-hemisphere lesion patients without neglect. Also, both beta and theta abnormalities contributed additively to visual awareness decrease, quantified in the Behavioural Inattention Test. These results provide evidence for the impairment of fast dynamic fronto-parietal interactions during early stages of visual processing in neglect pathology. Also, they reveal that different modes of fronto-parietal dysfunction contribute independently to deficits in visual awareness at the behavioural level.

Is insight a godsend? Explicit knowledge in the serial response-time task has precursors in EEG potentials already at task onset.

Whether, and how, explicit knowledge about some regularity arises from implicit sensorimotor learning by practice has been a matter of long-standing debate. Previously, we had found in the number reduction task that participants who will acquire explicit knowledge differ from other participants in their event-related potentials (ERPs) already at task onset. In the present study, we investigated such ERP precursors and correlates both of explicit and of sensorimotor knowledge (response speeding) about the regular sequence in a large sample of participants (n≈100) in the serial response time task. Already when perceiving random sequences at task onset, those participants had largest P3 amplitudes who would later gain explicit knowledge but whose responses were not speeded. Later in the task, sensorimotor knowledge was reflected in increased fronto-central negativity in irregular blocks, overlapping the early part of P3, and participants with later explicit knowledge generally had increased P3 amplitudes. These results support the notion that explicit knowledge about covert regularities is acquired in two ways: on the one hand by a particular subgroup of participants possibly independently of sequence-specific response speeding, and on the other hand by transforming such sensorimotor to explicit knowledge through practice.

Simultaneous EEG and fMRI reveals a causally connected subcortical-cortical network during reward anticipation.

Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) have been used to study the neural correlates of reward anticipation, but the interrelation of EEG and fMRI measures remains unknown. The goal of the present study was to investigate this relationship in response to a well established reward anticipation paradigm using simultaneous EEG-fMRI recording in healthy human subjects. Analysis of causal interactions between the thalamus (THAL), ventral-striatum (VS), and supplementary motor area (SMA), using both mediator analysis and dynamic causal modeling, revealed that (1) THAL fMRI blood oxygenation level-dependent (BOLD) activity is mediating intermodal correlations between the EEG contingent negative variation (CNV) signal and the fMRI BOLD signal in SMA and VS, (2) the underlying causal connectivity network consists of top-down regulation from SMA to VS and SMA to THAL along with an excitatory information flow through a THAL→VS→SMA route during reward anticipation, and (3) the EEG CNV signal is best predicted by a combination of THAL fMRI BOLD response and strength of top-down regulation from SMA to VS and SMA to THAL. Collectively, these findings represent a likely neurobiological mechanism mapping a primarily subcortical process, i.e., reward anticipation, onto a cortical signature.

Can Brief Listening to Mozart's Music Improve Visual Working Memory? An Update on the Role of Cognitive and Emotional Factors.

The aim of this research was to enhance understanding of the relationship between brief music listening and working memory (WM) functions. The study extends a previous large-scale experiment in which the effects of brief exposure to music on verbal WM were explored. In the present second phase of the experiment, these effects were assessed for the visuospatial subcomponent of WM. For that aim, visuospatial WM was measured using the Corsi blocks task-backwards and Visual Patterns Test in a large sample of 311 young and older adults after being exposed to musical excerpts coming from different music composers (Mozart, Vivaldi, Glass). To account for possible effects of arousal, a silence condition was used. Individual preference for music excerpts and emotional reactions to each condition were also subjectively rated using the Positive and Negative Affect Schedule (PANAS) to account for the role of emotional reactions in shaping subsequent cognitive performance. Results showed that music affected the visuospatial sketchpad of WM. In line with the previously described Mozart effect, only Mozart's music had a significant positive impact on visuospatial WM in the two age groups, regardless of preferences, and on overall age-related WM decline in older adults. The Mozart effect was more prominent for the VPT than the Corsi task and was also expressed for the prevailing positive effect. These observations are in contrast to the selective influence of Vivaldi's music on verbal WM that was detected in our first study. Together, the results demonstrate a differential music influence on the phonological loop and on the visuospatial sketchpad. They thus contribute to the debate of whether music has the potential to affect distinct processes within working memory in an excerpt- or composer-specific manner. Also, they suggest that emotional activation and central executive attention are essentially involved in modulating the influence of music on subsequent cognition. These findings can assist in the selection of music excerpts used in cognitive rehabilitation programs that focus on visuospatial skills.

Motor oscillations reveal new correlates of error processing in the human brain.

It has been demonstrated that during motor responses, the activation of the motor cortical regions emerges in close association with the activation of the medial frontal cortex implicated with performance monitoring and cognitive control. The present study explored the oscillatory neurodynamics of response-related potentials during correct and error responses to test the hypothesis that such continuous communication would modify the characteristics of motor potentials during performance errors. Electroencephalogram (EEG) was recorded at 64 electrodes in a four-choice reaction task and response-related potentials (RRPs) of correct and error responses were analysed. Oscillatory RRP components at extended motor areas were analysed in the theta (3.5-7 Hz) and delta (1-3 Hz) frequency bands with respect to power, temporal synchronization (phase-locking factor, PLF), and spatial synchronization (phase-locking value, PLV). Major results demonstrated that motor oscillations differed between correct and error responses. Error-related changes (1) were frequency-specific, engaging delta and theta frequency bands, (2) emerged already before response production, and (3) had specific regional topographies at posterior sensorimotor and anterior (premotor and medial frontal) areas. Specifically, the connectedness of motor and sensorimotor areas contra-lateral to the response supported by delta networks was substantially reduced during errors. Also, there was an error-related suppression of the phase stability of delta and theta oscillations at these areas. This synchronization reduction was accompanied by increased temporal synchronization of motor theta oscillations at bi-lateral premotor regions and by two distinctive error-related effects at medial frontal regions: (1) a focused fronto-central enhancement of theta power and (2) a separable enhancement of the temporal synchronization of delta oscillations with a localized medial frontal focus. Together, these observations indicate that the electrophysiological signatures of performance errors are not limited to the medial frontal signals, but they also involve the dynamics of oscillatory motor networks at extended cortical regions generating the movement. Also, they provide a more detailed picture of the medial frontal processes activated in relation to error processing.

A distributed theta network of error generation and processing in aging.

Based on previous concepts that a distributed theta network with a central "hub" in the medial frontal cortex is critically involved in movement regulation, monitoring, and control, the present study explored the involvement of this network in error processing with advancing age in humans. For that aim, the oscillatory neurodynamics of motor theta oscillations was analyzed at multiple cortical regions during correct and error responses in a sample of older adults. Response-related potentials (RRPs) of correct and incorrect reactions were recorded in a four-choice reaction task. RRPs were decomposed in the time-frequency domain to extract oscillatory theta activity. Motor theta oscillations at extended motor regions were analyzed with respect to power, temporal synchronization, and functional connectivity. Major results demonstrated that errors had pronounced effects on motor theta oscillations at cortical regions beyond the medial frontal cortex by being associated with (1) theta power increase in the hemisphere contra-lateral to the movement, (2) suppressed spatial and temporal synchronization at pre-motor areas contra-lateral to the responding hand, (2) inhibited connections between the medial frontal cortex and sensorimotor areas, and (3) suppressed connectivity and temporal phase-synchronization of motor theta networks in the posterior left hemisphere, irrespective of the hand, left, or right, with which the error was made. The distributed effects of errors on motor theta oscillations demonstrate that theta networks support performance monitoring. The reorganization of these networks with aging implies that in older individuals, performance monitoring is associated with a disengagement of the medial frontal region and difficulties in controlling the focus of motor attention and response selection. Supplementary Information: The online version contains supplementary material available at 10.1007/s11571-023-10018-4.

Aging alters functional connectivity of motor theta networks during sensorimotor reactions.

OBJECTIVE: Both cognitive and primary motor networks alter with advancing age in humans. The networks activated in response to external environmental stimuli supported by theta oscillations remain less well explored. The present study aimed to characterize the effects of aging on the functional connectivity of response-related theta networks during sensorimotor tasks. METHODS: Electroencephalographic signals were recorded in young and middle-to-older age adults during three tasks performed in two modalities, auditory and visual: a simple reaction task, a Go-NoGo task, and a choice-reaction task. Response-related theta oscillations were computed. The phase-locking value (PLV) was used to analyze the spatial synchronization of primary motor and motor control theta networks. RESULTS: Performance was overall preserved in older adults. Independently of the task, aging was associated with reorganized connectivity of the contra-lateral primary motor cortex. In younger adults, it was synchronized with motor control regions (intra-hemispheric premotor/frontal and medial frontal). In older adults, it was only synchronized with intra-hemispheric sensorimotor regions. CONCLUSIONS: Motor theta networks of older adults manifest a functional decoupling between the response-generating motor cortex and motor control regions, which was not modulated by task variables. The overall preserved performance in older adults suggests that the increased connectivity within the sensorimotor network is associated with an excessive reliance on sensorimotor feedback during movement execution compensating for a deficient cognitive regulation of motor regions during sensorimotor reactions. SIGNIFICANCE: New evidence is provided for the reorganization of motor networks during sensorimotor reactions already at the transition from middle to old age.

Event-related oscillations reflect functional asymmetry in children with attention deficit/hyperactivity disorder.

Previous studies have found that event-related theta and gamma oscillations elicited in an auditory selective attention task are deviant in children with attention deficit/hyperactivity disorder (ADHD). It has been suggested that these deviations are associated with deficient motor inhibition in ADHD, which may lead to increased excitability of not only the motor generation networks but also the networks involved in sensory and cognitive processing of the stimulus requiring motor response. Within this suggestion, the present study used the same experimental database to compare the motor cortical activation of healthy controls and children with ADHD during the performance of the auditory selective attention task. Electroencephalography mu (8-12 Hz) activity at C3 and C4 electrodes was used as a measure of motor cortical activation. Mu power was analyzed for four stimulus conditions of the task (attended target, unattended target, attended nontarget, and unattended nontarget). It was found that motor cortical activation as reflected by mu power suppression was not overall greater in ADHD than healthy children. However, stimuli that possessed only partial target features and did not require motor responding (unattended target and attended nontarget) produced a significant reduction of mu activity in ADHD patients. These results suggest that motor cortical excitability is not generally increased in ADHD children. Rather, the co-existence of conflict features in complex stimuli induces task-irrelevant motor activation in these children. The deficient inhibition of motor cortical networks contralateral to the response may therefore be responsible for the functional asymmetry in stimulus processing in ADHD.

Establishment and development of the Center of Plant Systems Biology and Biotechnology in Plovdiv, Bulgaria.

The Bulgarian research landscape, presented mainly by the research institutes that are part of the Bulgarian Academy of Sciences and the Agricultural Academy, needs diversification to match the research and innovation potential of the other European Union (EU) countries. This article describes the establishment of the Center of Plant Systems Biology and Biotechnology (CPSBB), a new innovative type of independent research organization that is changing the research landscape in Bulgaria. Supported by the EU Commission, Bulgarian Government, and Plovdiv Municipality, CPSBB has quickly become the leading plant science institute in Bulgaria, creating knowledge in diverse fields such as bioinformatics, biotechnology, genetics and genomics, metabolomics, and systems biology. We outline the organizational structure of CPSBB, the development of its infrastructure, and its scientific productivity. Finally, we compare CPSBB with other similar research establishments in Europe and we conclude that such new types of institutes have a bright future in Bulgaria due to their operational flexibility, productivity, and connections with academia and industry.

Increased alpha (8-12 Hz) activity during slow wave sleep as a marker for the transition from implicit knowledge to explicit insight.

The number reduction task (NRT) allows us to study the transition from implicit knowledge of hidden task regularities to explicit insight into these regularities. To identify sleep-associated neurophysiological indicators of this restructuring of knowledge representations, we measured frequency-specific power of EEG while participants slept during the night between two sessions of the NRT. Alpha (8-12 Hz) EEG power during slow wave sleep (SWS) emerged as a specific marker of the transformation of presleep implicit knowledge to postsleep explicit knowledge (ExK). Beta power during SWS was increased whenever ExK was attained after sleep, irrespective of presleep knowledge. No such EEG predictors of insight were found during Sleep Stage 2 and rapid eye movement sleep. These results support the view that it is neuronal memory reprocessing during sleep, in particular during SWS, that lays the foundations for restructuring those task-related representations in the brain that are necessary for promoting the gain of ExK.

Methylphenidate (MPH) promotes visual cortical activation in healthy adults in a cued visuomotor task.

Seeking for the mechanisms by which methylphenidate (MPH) improves behavior has demonstrated that MPH modulates excitability in the primary motor cortex. However, little is known about the influence of MPH on top-down controlled mechanisms in the sensory domain. The present study explored the effects of MPH on the activation of visual cortices in healthy adults who performed a cued visuo-motor task in a double-blind placebo-controlled crossover design. Two distinct measures, posterior alpha power and occipital slow cortical potentials (SCPs), were used to reflect raise in excitability and attention-based activation of visual cortical areas. According to the results, performance parameters (reaction time, response variance and error rate) were not affected by MPH. At the neurophysiologic level reflected by reduced alpha power, MPH increased the overall excitability of the occipital cortex, but not the parietal cortex. Before the cued response, MPH reduced alpha power and increased SCPs only before right hand responses, mostly at the right occipital location. It can be concluded that in visuo-motor tasks, MPH has the potency of adjusting the background excitation/inhibition balance of visual areas. Additionally, MPH may raise the attention controlled activation of visual cortical regions, especially during increased response control.

Independent oscillatory patterns determine performance fluctuations in children with attention deficit/hyperactivity disorder.

The maintenance of stable goal-directed behaviour is a hallmark of conscious executive control in humans. Notably, both correct and error human actions may have a subconscious activation-based determination. One possible source of subconscious interference may be the default mode network that, in contrast to attentional network, manifests intrinsic oscillations at very low (<0.1 Hz) frequencies. In the present study, we analyse the time dynamics of performance accuracy to search for multisecond periodic fluctuations of error occurrence. Attentional lapses in attention deficit/hyperactivity disorder are proposed to originate from interferences from intrinsically oscillating networks. Identifying periodic error fluctuations with a frequency<0.1 Hz in patients with attention deficit/hyperactivity disorder would provide a behavioural evidence for such interferences. Performance was monitored during a visual flanker task in 92 children (7- to 16-year olds), 47 with attention deficit/hyperactivity disorder, combined type and 45 healthy controls. Using an original approach, the time distribution of error occurrence was analysed in the frequency and time-frequency domains in order to detect rhythmic periodicity. Major results demonstrate that in both patients and controls, error behaviour was characterized by multisecond rhythmic fluctuations with a period of ∼12 s, appearing with a delay after transition to task. Only in attention deficit/hyperactivity disorder, was there an additional 'pathological' oscillation of error generation, which determined periodic drops of performance accuracy each 20-30 s. Thus, in patients, periodic error fluctuations were modulated by two independent oscillatory patterns. The findings demonstrate that: (i) attentive behaviour of children is determined by multisecond regularities; and (ii) a unique additional periodicity guides performance fluctuations in patients. These observations may re-conceptualize the understanding of attentive behaviour beyond the executive top-down control and may reveal new origins of psychopathological behaviours in attention deficit/hyperactivity disorder.

The sleeping brain and the neural basis of emotions.

In addition to active wake, emotions are generated and experienced in a variety of functionally different states such as those of sleep, during which external stimulation and cognitive control are lacking. The neural basis of emotions can be specified by regarding the multitude of emotion-related brain states, as well as the distinct neuro- and psychodynamic stages (generation and regulation) of emotional experience.

The Primacy of Beauty in Music, Visual Arts and Literature: Not Just a Replication Study in the Greek Language Exploring the Effects of Verbal Fluency, Age and Gender.

Research on aesthetic descriptors of art in different languages is scarce. The aim of the present study was to elucidate the conceptual structure of aesthetic experiences of three forms of art (music, visual arts and literature) in the Greek language, which has not been explored so far. It was further aimed to study if biological and cognitive factors such as age and gender might produce differences in art appreciation. A total of 467 younger and older individuals from Greece were asked to generate verbal descriptors (adjectives) in free word-listing conditions in order to collect terms reflecting the aesthetics-related semantic field of art. The capacity of verbal memory was controlled by using a battery of neuropsychological tests. Analysis of generated adjectives' frequency and salience revealed that 'beautiful' was the most prominent descriptor that was selected with a distinctive primacy for all three forms of arts. The primacy of 'beautiful' was significantly more pronounced for visual arts relative to music and literature. Although the aging-related decline of verbal capacity was similar for males and females, the primacy of 'beautiful' depended on age and gender by being more emphasized for young females than males, and for old males than females. Analysis of secondary descriptors and pairs of adjectives revealed that affective and hedonic experiences are essentially fixed in the semantic field of art reflection. It is concluded that although the concept of the aesthetics seems to be diversified and rich, a clear primacy of beauty is found for the Greek cultural environment and across different forms of art. The results also highlight the presence of complex influences of biological and cognitive factors on aesthetic art experiences.

The role of the BDNF Val66Met polymorphism for the synchronization of error-specific neural networks.

Behavioral adaptation depends on the recognition of response errors and processing of this error-information. Error processing is a specific cognitive function crucial for behavioral adaptation. Neurophysiologically, these processes are reflected by an event-related potential (ERP), the error negativity (Ne/ERN). Even though synchronization processes are important in information processing, its role and neurobiological foundation in behavioral adaptation are not understood. The brain-derived neurotrophic factor (BDNF) strongly modulates the establishment of neural connectivity that determines neural network dynamics and synchronization properties. Therefore altered synchronization processes may constitute a mechanism via which BDNF affects processes of error-induced behavioral adaptation. We investigate how variants of the BDNF gene regulate EEG-synchronization processes underlying error processing. Subjects (n=65) were genotyped for the functional BDNF Val66Met polymorphism (rs6265). We show that Val/Val genotype is associated with stronger error-specific phase-locking, compared with Met allele carriers. Posterror behavioral adaptation seems to be strongly dependent on these phase-locking processes and efficacy of EEG-phase-locking-behavioral coupling was genotype dependent. After correct responses, neurophysiological processes were not modulated by the polymorphism, underlining that BDNF becomes especially necessary in situations requiring behavioral adaptation. The results suggest that alterations in neural synchronization processes modulated by the genetic variants of BDNF Val66Met may be the mechanism by which cognitive functions are affected.

Neural Correlates of Aging-Related Differences in Pro-active Control in a Dual Task.

Background: Multi-tasking is usually impaired in older people. In multi-tasking, a fixed order of sub-tasks can improve performance by promoting a time-structured preparation of sub-tasks. How proactive control prioritizes the pre-activation or inhibition of complex tasks in older people has received no sufficient clarification so far. Objective: To explore the effects of aging on neural proactive control mechanisms in a dual task. Methodology: To address this question, the psychological refractory period (PRP) paradigm was used. Two 2-alternative-forced-choice reaction tasks with a predefined order (T1 and T2) signaled by a cue had to be executed simultaneously or consecutively by young (mean age 25.1 years, n = 36) and old subjects (mean age 70.4 years, n = 118). Performance indices of dual-task preparation were used to assess the focused preparation of T1 and T2. To compare preparatory mechanisms at the neurophysiologic level, multi-channel electroencephalogram (EEG) was recorded and negative slow cortical potentials (SCPs) were analyzed as objective markers of the amount and localization of cortical pre-activation before sub-task presentation. Results: Dual-task performance was significantly slower in old adults. T1 performance was facilitated in both age groups, but T2 processing in old adults was not optimized by the temporal structure as efficiently as in young adults. Also, only young adults manifested a stable pattern of focused of negative slow-wave activity increase at medial frontal and right-hemisphere posterior regions, which was associated with a coordinated preparatory T1 pre-activation and T2 deferment, while old adults manifested a broad topographic distribution of negative SCPs associated with a pre-activation of sensory and motor processes. Conclusions: These observations demonstrate that the proactive preparation for dual tasking is altered with aging. It is suggested that in young adults, attention-based pre-activation of working memory and inhibitory networks in the right hemisphere synchronizes the simultaneous preparation of the two sub-tasks, whereas in old adults, sensory and motor networks appear to be non-specifically pre-activated for subsequent deferred mode of processing.

Attentional and cognitive monitoring brain networks in long-term meditators depend on meditation states and expertise.

Meditation practice is suggested to engage training of cognitive control systems in the brain. To evaluate the functional involvement of attentional and cognitive monitoring processes during meditation, the present study analysed the electroencephalographic synchronization of fronto-parietal (FP) and medial-frontal (MF) brain networks in highly experienced meditators during different meditation states (focused attention, open monitoring and loving kindness meditation). The aim was to assess whether and how the connectivity patterns of FP and MF networks are modulated by meditation style and expertise. Compared to novice meditators, (1) highly experienced meditators exhibited a strong theta synchronization of both FP and MF networks in left parietal regions in all mediation styles, and (2) only the connectivity of lateralized beta MF networks differentiated meditation styles. The connectivity of intra-hemispheric theta FP networks depended non-linearly on meditation expertise, with opposite expertise-dependent patterns found in the left and the right hemisphere. In contrast, inter-hemispheric FP connectivity in faster frequency bands (fast alpha and beta) increased linearly as a function of expertise. The results confirm that executive control systems play a major role in maintaining states of meditation. The distinctive lateralized involvement of FP and MF networks appears to represent a major functional mechanism that supports both generic and style-specific meditation states. The observed expertise-dependent effects suggest that functional plasticity within executive control networks may underpin the emergence of unique meditation states in expert meditators.

Tuning the brain for novelty detection under emotional threat: the role of increasing gamma phase-synchronization.

Effective orienting of attention towards novel events is crucial for survival, particularly if they occur in a dangerous situation. This is why stimuli with emotional value are more efficient in capturing attention than neutral stimuli, and why the processing of unexpected novel stimuli is enhanced under a negative emotional context. Here we measured the phase-synchronization (PS) of gamma-band responses (GBR) from human EEG scalp-recordings during performance of a visual discrimination task in which task-irrelevant standard and novel sounds were presented in either a neutral or a negative emotional context, in order to elucidate the brain mechanisms by which emotion tunes the processing of novel events. Visual task performance was distracted by novel sounds, and this distraction was enhanced by the negative emotional context. Similarly, gamma PS was enhanced after novel as compared to standard sounds and it was also larger to auditory stimuli in the negative than in the neutral emotional context, reflecting the synchronization of neural networks for increasing of attentional processing. Remarkably, the larger PS increase of GBR after novel sounds in the negative as compared to the neutral emotional context over midline and right frontal regions reveals that a negative emotional context tunes novelty processing by means of the PS of brain activity in the gamma frequency band around 40 Hz in specific neural networks.

Functional 5-HT1a receptor polymorphism selectively modulates error-specific subprocesses of performance monitoring.

Our study investigates the dependence of response monitoring and error detection on genetic influences modulating the serotonergic system. This was done using the event-related potentials (ERPs) after error (Ne/ERN) and correct trials (Nc/CRN). To induce a sufficient amount of errors, a standard flanker task was used. The subjects (N = 94) were genotyped for the functional 5-HT1A C(-1019)G polymorphism. The results show that the 5-HT1A C(-1019)G polymorphism specifically modulates error detection. Neurophysiological modulations on error detection were paralleled by a similar modulation of response slowing after an error, reflecting the behavioral adaptation. The 5-HT1A -1019 CC genotype group showed a larger Ne and stronger posterror slowing than the CG and GG genotype groups. More general processes of performance monitoring, as reflected in the Nc/CRN, were not affected. The finding that error-specific processes, but not general response monitoring processes, are modulated by the 5-HT1A C(-1019)G polymorphism is underlined by a wavelet analysis. In summary, the results suggest a specific effect of the 5-HT1A C(-1019)G polymorphism on error monitoring, as reflected in the Ne, and suggest a neurobiological dissociation between processes of error monitoring and general response monitoring at the level of the serotonin 1A receptor system.