Spectral and Anatomical Patterns of Large-Scale Synchronization Predict Human Attentional Capacity

The capacity of visual attention determines how many visual objects may be perceived at any moment. This capacity can be investigated with multiple object tracking (MOT) tasks, which have shown that it varies greatly between individuals. The neuronal mechanisms underlying capacity limits have remained poorly understood. Phase synchronization of cortical oscillations coordinates neuronal communication within the fronto-parietal attention network and between the visual regions during endogenous visual attention. We tested a hypothesis that attentional capacity is predicted by the strength of pretarget synchronization within attention-related cortical regions. We recorded cortical activity with magneto- and electroencephalography (M/EEG) while measuring attentional capacity with MOT tasks and identified large-scale synchronized networks from source-reconstructed M/EEG data. Individual attentional capacity was correlated with load-dependent strengthening of theta (3-8 Hz), alpha (8-10 Hz), and gamma-band (30-120 Hz) synchronization that connected the visual cortex with posterior parietal and prefrontal cortices. Individual memory capacity was also preceded by crossfrequency phase-phase and phase-amplitude coupling of alpha oscillation phase with beta and gamma oscillations. Our results show that good attentional capacity is preceded by efficient dynamic functional coupling and decoupling within brain regions and across frequencies, which may enable efficient communication and routing of information between sensory and attentional systems.Peer reviewe

Subthalamic nucleus gamma activity increases not only during movement but also during movement inhibition.

Gamma activity in the subthalamic nucleus (STN) is widely viewed as a pro-kinetic rhythm. Here we test the hypothesis that rather than being specifically linked to movement execution, gamma activity reflects dynamic processing in this nucleus. We investigated the role of gamma during fast stopping and recorded scalp electroencephalogram and local field potentials from deep brain stimulation electrodes in 9 Parkinson's disease patients. Patients interrupted finger tapping (paced by a metronome) in response to a stop-signal sound, which was timed such that successful stopping would occur only in ~50% of all trials. STN gamma (60-90 Hz) increased most strongly when the tap was successfully stopped, whereas phase-based connectivity between the contralateral STN and motor cortex decreased. Beta or theta power seemed less directly related to stopping. In summary, STN gamma activity may support flexible motor control as it did not only increase during movement execution but also during rapid action-stopping

Thermostat or thermometer? A Finnish perspective on the overloaded role of sustainability indicators in societal transition

Various expectations are placed on national-level sustainability indicators. Ideally, they should serve as efficient tools for transformations, leading societies to sustainable paths by creating a comprehensive, reliable, timely, and easy-to-understand picture of the key ecological, socio-cultural, and economic trends. Most, if not all, indicator initiatives so far have been unable to meet such grandiose expectations. This has evoked criticism of and scepticism towards the indicator approach, but has also motivated improvement of indicator sets and knowledge brokerage processes. This article discusses the role of sustainability indicators in societal transition by examining the experiences gained from the preparation and launch of a sustainable development indicator set specifically aimed at supporting national-level policymaking in Finland. It is concluded that better recognition of the tensions between attempts to improve the quality of indicators and attempts to enhance their use in policy is key to meeting the expectations placed upon sustainability indicators

Redox dysregulation, neuroinflammation, and NMDA receptor hypofunction: A "central hub" in schizophrenia pathophysiology?

Accumulating evidence points to altered GABAergic parvalbumin-expressing interneurons and impaired myelin/axonal integrity in schizophrenia. Both findings could be due to abnormal neurodevelopmental trajectories, affecting local neuronal networks and long-range synchrony and leading to cognitive deficits. In this review, we present data from animal models demonstrating that redox dysregulation, neuroinflammation and/or NMDAR hypofunction (as observed in patients) impairs the normal development of both parvalbumin interneurons and oligodendrocytes. These observations suggest that a dysregulation of the redox, neuroimmune, and glutamatergic systems due to genetic and early-life environmental risk factors could contribute to the anomalies of parvalbumin interneurons and white matter in schizophrenia, ultimately impacting cognition, social competence, and affective behavior via abnormal function of micro- and macrocircuits. Moreover, we propose that the redox, neuroimmune, and glutamatergic systems form a "central hub" where an imbalance within any of these "hub" systems leads to similar anomalies of parvalbumin interneurons and oligodendrocytes due to the tight and reciprocal interactions that exist among these systems. A combination of vulnerabilities for a dysregulation within more than one of these systems may be particularly deleterious. For these reasons, molecules, such as N-acetylcysteine, that possess antioxidant and anti-inflammatory properties and can also regulate glutamatergic transmission are promising tools for prevention in ultra-high risk patients or for early intervention therapy during the first stages of the disease

Functional integration across oscillation frequencies by cross-frequency phase synchronization

Neuronal oscillations and their inter-areal synchronization may be instrumental in regulating neuronal communication in distributed networks. Several lines of research have, however, shown that cognitive tasks engage neuronal oscillations simultaneously in multiple frequency bands that have distinct functional roles in cognitive processing. Gamma oscillations (30-120Hz) are associated with bottom-up processing, while slower oscillations in delta (1-4Hz), theta (4-7Hz), alpha (8-14Hz) and beta (14-30Hz) frequency bands may have roles in executive or top-down controlling functions, although also other distinctions have been made. Identification of the mechanisms that integrate such spectrally distributed processing and govern neuronal communication among these networks is crucial for understanding how cognitive functions are achieved in neuronal circuits. Cross-frequency interactions among oscillations have been recognized as a likely candidate mechanism for such integration. We advance here the hypothesis that phase-phase synchronization of neuronal oscillations in two different frequency bands, cross-frequency phase synchrony (CFS), could serve to integrate, coordinate and regulate neuronal processing distributed into neuronal assemblies concurrently in multiple frequency bands. A trail of studies over the past decade has revealed the presence of CFS among cortical oscillations and linked CFS with roles in cognitive integration. We propose that CFS could connect fast and slow oscillatory networks and thereby integrate distributed cognitive functions such as representation of sensory information with attentional and executive functions.Peer reviewe

Role of oscillations in visual perception : attention and working memory

People have large differences in their visual attentional and working memory (WM) abilities. Both attention and WM are thought to comprise of representation of sensory information and its attentional / executive control. A common finding is that people’s ability to attend to or to memorize several items concurrently ranges from 2 to 4 items. How attention and working memory functions arise from distributed brain activity and what mechanisms limit the attentional and working memory capacity are largely unknown. In this thesis, concurrent magnetoencephalography and electroencephalography (MEG and EEG) recordings of whole brain activity combined with source modeling were used to study the role of rhythmic cortical activity in attention and WM. Visual attention was studied with a multiple object tracking task (MOT), where the subjects tracked 1–4 moving target objects with and without distracter objects. The functional role local oscillations amplitudes as well as the significance of large-scale inter-areal synchronization in setting the capacity of visual attention were studied. We found a decrease in oscillation amplitudes at relatively lower frequencies (alpha–beta), and an increase at higher frequencies in the gamma band (30–90 Hz) as a function of attentional load. The load-dependent oscillation amplitude modulations differed in better and worse performing subjects (i.e. subjects with high and low attentional capacity, respectively). In high-capacity subjects, gamma amplitudes increased more strongly as a function of load in widespread cortical regions including lateral PFC, temporal and visual areas, whereas in the low capacity subjects load-dependent gamma amplitude increase was smaller. Large-scale inter-areal synchronization was found at low theta (4–5 Hz) and high-gamma (70–90 Hz) bands. The most robust connections were observed between the left and right PFCs and between visual areas and PFC. The load-dependent strengthening in inter-areal synchronization differed between high and low capacity subjects at several frequencies. These results suggest that both local and inter-areal rhythmic activity differences can explain differences in attentional capacity. Visual working memory was studied with a delayed match-to-sample WM task, where different visual features or their conjunctions were retained in WM. The functional role of load-dependent oscillation amplitudes in remembering different features were studied. Distinct load-dependent differences in local gamma-band amplitudes were found to reflect maintenance of specific visual features in WM. Gamma band oscillations were also increased for the memorizing the conjunction of features supporting their role in binding of visual features. These results suggest that especially rhythmic gamma activity is important in maintaining visual information WM. Taken together our results suggest common mechanisms for visual attention and VWM, and that gamma oscillations work in a highly task specific manner, and that gamma oscillations are critical for perception.Ihmisillä on huomattavia eroja heidän henkisissä ominaisuuksissa, kuten näkötarkkaavaisuudessa sekä työmuistissa. Kyky hallita huomion kohdentamista on tärkeää, jotta tarkkaavaisuus ei siirry tarpeettomiin asioihin (ooh perhonen!), ja toisaalta jotta pystyisi tarkkailemaan yhtä asiaa pitkän aikaa. Tätä kutsutaan tarkkaavaisuudeksi. Työmuisti on kyky pitää mielessä asioita ja niiden ominaisuuksia, sekä muuntaa näitä mielessä olevia asioita. Näkötyömuistin määritelmä tässä väitöskirjassa on teknisesti: sen hetkistä tehtävää palveleva näköinformaation aktiivinen pitäminen mielessä. Monissa kokeissa on arvioitu, että ihmiset pystyvät pitämään mielessään tai tarkkailemaan 2–4:ää asiaa yhtä aikaa. Määrä riippuu vahvasti sekä yksilöllisistä ominaisuuksista että kokeen haastavuudesta. Tässä väitöskirjassa tutkitaan yhtäaikaisella MEG- sekä EEG-aivokuvantamislaitteilla normaaleja koehenkilöitä, kun he tekevät näkötarkkaavaisuus- tai näkötyömuistikokeita. MEG- ja EEG-laitteilla voidaan mitata aivoperäisiä heikkoja signaaleja erittäin hyvällä ajallisella tarkkuudella. Yhdistämällä MEG-EEG -mittausten toiminnallisen signaalin sekä MRI:n anatomisen mallin voidaan arvioida, miltä aivoalueilta toiminnallinen signaali tulee. Väitöskirjassa tutkitaan näkötarkkaavaisuuskyvyn yksilöllisten erojen perustaa, sekä näkötyömuistitehtävän avulla erilaisten kohteiden ominaisuuksien mielessä pitämisen perustaa. Näitä perusteita tarkastellaan tutkien aivokuoren rytmistä toimintaa. Näkötarkkaavaisuuskokeessa hyvin pärjäävillä koehenkilöillä oli enemmän kokeen vaikeuden mukaan lisääntyvää korkeataajuista gamma-aktiivisuutta, kuin huonommin pärjäävillä koehenkilöillä. Tämä näkyi sekä paikallisena aktiivisuutena, että aivoalueiden välisenä synkronisaationa. Osa tuloksista vihjaa siihen, että keskitaajuinen ns. beta-aktiivisuus saattaa ohjata korkeampaa gamma-aktiivisuutta. Aiemmissa tutkimuksissa on havaittu, että gamma-aktiivisuus on tärkeää mm. näköhavaintojen tietoisessa aistimisessa. Lisäksi näkötarkkaavaisuuskokeessa havaittiin kaksijakoinen rooli matalahkolla ns. alfa-taajuudella. Paikallinen aktiivisuus madaltui, mutta synkronisaatio aivoalueiden välillä lisääntyi kokeen vaikeuden mukaan. Näkötyömuistikokeessa havaittiin, että näköärsykkeiden erilaisten ominaisuuksien mielessä pitäminen vastasi erilaisia paikallisia gamma-aktiivisuus -vasteita niin ajoituksen kuin aivoalueiden mukaan. Lisäksi havaittiin, että gamma-aktiivisuus on tärkeää erilaisten näköärsykeominaisuuksien yhdistämisessä. Nämä tulokset viittaavat siihen, että näkötarkkaavaisuudella sekä –työmuistilla on ainakin osittain sama perusta, rytminen gamma-aktiivisuus on hyvin tehtäväriippuvaista, ja että rytminen gamma-aktiivisuus on kriittistä havainnoimisessa