Extensive empirical evidence suggests that there is a maximal number of people with whom an individual can maintain stable social relationships (the Dunbar number). We argue that this arises as a ...consequence of a natural phase transition in the dynamic selforganization among N individuals within a social system. We present the calculated size dependence of the scaling properties of complex social network models to argue that this collective behavior is an enhanced form of collective intelligence. Direct calculation establishes that the complexity of social networks as measured by their scaling behavior is nonmonotonic, peaking around 150, thereby providing a theoretical basis for the value of the Dunbar number. Thus, we establish a theory-based bridge spanning the gap between sociology and psychology.
Compensatory reorganization of the nigrostriatal system is thought to delay the onset of symptoms in early Parkinson disease (PD). Here we sought evidence that compensation may be a part of a more ...widespread functional reorganization in sensorimotor networks, including primary motor cortex.
Several neurophysiologic measures known to be abnormal in the motor cortex (M1) of patients with advanced PD were tested on the more and less affected side of 16 newly diagnosed and drug-naive patients with PD and compared with 16 age-matched healthy participants. LTP-like effects were probed using a paired associative stimulation protocol. We also measured short interval intracortical inhibition, intracortical facilitation, cortical silent period, and input/output curves.
The less affected side in patients with PD had preserved intracortical inhibition and a larger response to the plasticity protocol compared to healthy participants. On the more affected side, there was no response to the plasticity protocol and inhibition was reduced. There was no difference in input/output curves between sides or between patients with PD and healthy participants.
Increased motor cortical plasticity on the less affected side is consistent with a functional reorganization of sensorimotor cortex and may represent a compensatory change that contributes to delaying onset of clinical symptoms. Alternatively, it may reflect a maladaptive plasticity that provokes symptom onset. Plasticity deteriorates as the symptoms progress, as seen on the more affected side. The rate of change in paired associative stimulation response over time could be developed into a surrogate marker of disease progression in PD.
Corticobasal degeneration (CBD) is a neurodegenerative condition characterized by 4R tau protein deposition in several brain regions that clinically manifests itself as a heterogeneous atypical ...parkinsonism typically expressed in adulthood. The prototypical clinical phenotype of CBD is corticobasal syndrome (CBS). Important insights into the pathophysiological mechanisms underlying motor and higher cortical symptoms in CBS have been gained by using advanced neuroimaging and neurophysiological techniques. Structural and functional neuroimaging studies often show asymmetric cortical and subcortical abnormalities, mainly involving perirolandic and parietal regions and basal ganglia structures. Neurophysiological investigations including electroencephalography and somatosensory evoked potentials provide useful information on the origin of myoclonus and on cortical sensory loss. Transcranial magnetic stimulation demonstrates heterogeneous and asymmetric changes in the excitability and plasticity of primary motor cortex and abnormal hemispheric connectivity. Neuroimaging and neurophysiological abnormalities in multiple brain areas reflect asymmetric neurodegeneration, leading to asymmetric motor and higher cortical symptoms in CBS.
Background and purpose
Essential tremor (ET) is a movement disorder primarily characterized by upper limb postural and kinetic tremor. Although still under‐investigated, bradykinesia may be part of ...the phenotypic spectrum of ET. The aim was to evaluate bradykinesia features in ET through clinical examination and kinematic analysis of repetitive finger movements. Data collected in ET patients were compared with those recorded in Parkinson’s disease patients and healthy controls.
Methods
Overall, 258 subjects participated in the study (90 ET patients, 84 Parkinson’s disease patients and 84 healthy controls). Repetitive finger tapping was kinematically recorded using a motion analysis system. Movement velocity, amplitude and decrement (sequence effect) were measured. The three groups were first compared by one‐way analysis of variance. A cluster analysis was also performed to better address the data variability observed in ET patients. Possible relationships between kinematic and clinical data were assessed in ET patients.
Results
Essential tremor patients were slower than healthy controls. Movement slowness in ET did not correlate with postural or kinetic tremor severity. It was also found that movement slowness in ET was not associated with a sequence effect, which instead is a common feature in Parkinson’s disease. Cluster analysis showed that a proportion of ET patients may have movement abnormalities similar to those observed in Parkinson’s disease.
Conclusions
Movement slowness without sequence effect is a common feature in ET patients. The present findings are relevant when interpreted in the context of the new tremor classification system and in the development of a more accurate bradykinesia definition.
Background and purpose
Hypomimia is a prominent clinical feature in people with Parkinson’s disease (PD), but it remains under‐investigated. We aimed to examine the clinical correlates of hypomimia ...in PD and to determine whether this is a levodopa‐responsive sign.
Methods
We included 89 people with PD. Hypomimia was assessed from digital video recordings by movement disorder specialists. Clinical evaluation included use of the Unified Parkinson’s Disease Rating Scale part III (UPDRS‐III), and assessment of motor and non‐motor symptoms using standardized clinical scales. The relationships between hypomimia and other clinical data were analysed using Mann–Whitney U‐tests and regression analysis.
Results
Hypomimia occurred in up to 70% of patients with PD. Patients with hypomimia had worse UPDRS‐III 'off‐medication' scores, mainly driven by bradykinesia and rigidity subscores. Patients with hypomimia also had worse apathy than patients without hypomimia. Finally, we found that hypomimia was levodopa‐responsive and its improvement mirrored the change by levodopa in axial motor symptoms.
Conclusion
Our study provides novel information regarding the clinical correlates of hypomimia in people with PD. A better understanding of hypomimia may be relevant for improving treatment and quality of life in PD.
Read the Commentaries on this Feature Paper: Institutional vertebratism hampers insect conservation generally; not just saproxylic beetle conservation; Knowledge gaps in protected area effectiveness
...Response from the authors: Possible directions in the protection of the neglected invertebrate biodiversity
Up to now, global conservation priorities are far from incorporating megadiverse invertebrate taxa. Thus, an important emerging field in biological conservation is how we might manage landscape to preserve insects. In this study, we analyze the efficacy of Italian reserve network for protecting multiple saproxylic beetles, considering both nationally designated areas and Natura 2000 sites. We selected 150 species inhabiting the Italian territory from the European Red List for saproxylic beetles, on the basis of distribution data availability. For each species, a vulnerability score was assigned according to their Red List status, and the species' distributions data were used to perform an irreplaceability analysis. Our analyses show that conservation targets based on geographic range extent are achieved for only 7% of the considered species. We find that 13 species are not represented in any protected area: among these, two click beetle species (Elateridae) are listed in the International Union for Conservation of Nature threatened categories (i.e. Ampedus quadrisignatus EN and Ampedus brunnicornis VU). Our analyses on protected area effectiveness for the conservation of saproxylic beetles showed that nationally designated protected areas are more irreplaceable than a random selection of cells. Surprisingly, the addition of Natura 2000 sites did not improve the species representation. Moreover, these reserves include sites that are not more irreplaceable than a random selection of cells. We identify some currently unprotected areas that protection could prevent from future extinctions and ensure a favorable conservation status of saproxylic beetles. In particular, we find an important stronghold for beetle conservation, which obtained a high irreplaceability score, in the Adige river basin. We recommend the designation of new reserves in this area to complement the existing network and to help guarantee invertebrate saproxylic fauna protection.
We conducted a magnetotelluric (MT) study from Paleoproterozoic Rio de la Plata Craton, in Uruguay, toward Paleozoic‐Mesozoic Paraná Basin, in Brazil. The 850‐km‐long MT transect comprises 35 evenly ...spaced broadband electromagnetic soundings sites. In the Paraná Basin, 11 additional long‐period measurements were acquired to extend the maximum depth of investigation. All data were inverted using two‐ and three‐dimensional approaches obtaining the electrical resistivity structure from the surface down to 200 km. The Rio de la Plata Craton is >200‐km thick and resistive (~2,000 Ωm). Its northern limit is electrically defined by a lithosphere scale lateral transition and lower crust conductive anomalies (1–10 Ωm) interpreted as a Paleoproterozoic suture at the southern edge of Rivera‐Taquarembó Block. The latter is characterized by an approximately 100‐km thick and moderate resistive (>500 Ωm) upper mantle. The Ibaré shear zone is another suture where an ocean‐ocean subduction generated the 120‐km thick and resistive (>1,000 Ωm) São Gabriel juvenile arc. Proceeding northward, a 70‐ to 80‐km thick, 150‐km wide, and inclined resistive zone is imaged. This zone could be remnant of an oceanic lithosphere or island arcs accreted at the southern border of Paraná Basin. The MT transect terminates within the southern Paraná Basin where a 150‐ to 200‐km‐thick less resistive lithosphere (<1,000 Ωm) may indicate refertilization processes during plate subduction and ocean closure in Neoproterozoic‐Cambrian time. Our MT data support a tectonic model of NNE–SSW convergence for this segment of SW Gondwanaland.
Key Points
Rio de la Plata and Paraná Basin lithospheres are at ~200‐km and 150‐ to 200‐km thick, respectively, and electrically distinct
Accreted Rivera‐Taquarembó‐São Gabriel blocks compose a heterogeneous and ~100‐km‐thick resistive lithosphere
Estimated geoelectrical strikes support NNE–SSW convergence and ocean closure during the amalgamation of SW Gondwanaland
Invasive alien species (IAS) are considered one of the largest drivers of biodiversity loss worldwide and the negative impacts of IAS can also affect human health and economy. More than 12,000 alien ...species occur in Europe. Terrestrial invertebrate species are the largest proportion of alien animal species and represents one of the most impacting groups in Europe. The most important European policy against alien species is the EU Regulation 1143/2014, which provides for the development of priority lists of IAS of relevant concern aimed to allow the optimization of intervention measures. Italian policy implemented the EU Regulation with the Legislative Decree No 230/2017 that provides the adoption of a list of IAS of national concern. Aim of this work is to present a preliminary prioritized list of alien terrestrial invertebrate species (ATIS) present in Italy, thus providing an useful tool to identify species to be included in the list of IAS of national concern. We defined criteria for assessing the species and ranking them in a prioritized list on the basis of the magnitude of their potential impact on wild native biodiversity. We identify 233 relevant ATIS, among the 1126 species included in the Italian Alien Terrestrial Invertebrate Database, on which the evaluation process started. After the evaluation process, 109 ATIS with considerable impacts on biodiversity were selected and prioritized. We ranked the species in four priority categories by matching their distribution in Italy with the magnitude of their possible impact on biodiversity.
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