The two-factor structure of cognitive flexibility : tempo of switching and overcoming of prepotent responses

Prezentowane badanie miało na celu odkrycie struktury procesów latentnych leżących u podstaw wykonania kilku zadań, które hipotetycznie mierzą spontaniczną i adaptacyjną giętkość poznawczą, dostarczając dowodów na ich trafność zbieżną. Grupa zdrowych ochotników (N = 121) ukończyła dwa zestawy zadań do oceny spontanicznej i adaptacyjnej giętkości poznawczej. Spontaniczna giętkość poznawcza obejmowała test myślenia dywergencyjnego (do oceny płynności i giętkości myślenia) oraz werbalny test płynności. Miary giętkości adaptacyjnej obejmowały test przełączania się między zadaniami jako miarę kosztów przełączania oraz test przerzucania uwagi jako miarę wyuczonej nieistotności i perseweracji. Natomiast test znajomości słownictwa dostarczył zastępczej miary inteligencji skrystalizowanej . Analiza klastrów hierarchicznych analiza metodą Warda wykazała istnienie dwóch odrębnych podgrup zmiennych. Pierwsza grupa obejmowała płynność i giętkość myślenia, inteligencję skrystalizowaną, płynność werbalną oraz koszty przełączania się. Druga grupa obejmowała zmienne z zadania wymagającego przełączania uwagi, czyli wyuczoną nieadekwatność i persewerację. Uważamy, że te wyniki są znaczące i wskazują na udział dwóch oddzielnych czynników kształtujących giętkość poznawczą: (a) tempo przełączania i (b) przezwyciężanie dominujących reakcji. W podsumowaniu omówiono implikacje tych wyników dla oceny giętkości poznawczej.The current study aimed to uncover the structure of common latent processes underlying the execution of several tasks that hypothetically measure spontaneous and adaptive cognitive flexibility, providing evidence for their convergent validity. A group of healthy volunteers (N = 121) completed two sets of tasks to assess spontaneous and adaptive cognitive flexibility. Spontaneous flexibility measures included a divergent thinking test (to assess fluency and flexibility of thinking) and a verbal fluency test. Adaptive flexibility measures involved a set-switching test as a measure of switch costs and an attentional set-shifting test as a measure of learned irrelevance and perseveration). A vocabulary knowledge test provided a proxy measure of crystallized intelligence. Hierarchical cluster analysis using Ward's method revealed the existence of two separate subgroups of variables. The first group comprised fluency and flexibility of thinking, crystallized intelligence, verbal fluency, and switch costs. The second group included attentional shift variables, that is, learned irrelevance and perseveration. We consider these results meaningful and indicative of two separate factors contributing to cognitive flexibility: (a) speed of switching and (b) overcoming of prepotent responses. We discuss the implications of our results for the assessment of cognitive flexibility

Synthesis of cyclic carbonates from diols and CO2 catalyzed by carbenes

The synthesis of cyclic carbonates from epoxides and CO2 is a well-established reaction, whereas the synthesis of cyclic carbonates from diols and CO2 is considerably more challenging, and few efficient catalysts are available. Here, we describe heterocyclic carbene catalysts, including one derived from a cheap and efficient thiazolium salt, for this latter reaction. The reaction proceeds at atmospheric pressure in the presence of an alkyl halide and Cs2CO3. Reaction mechanisms for the transformations involved are also proposed

Multimetallic main group prophenol catalysts for homo- and multi-block polyester synthesis and depolymerisation

Cyclic ester ring-opening polymerisation (ROP) is an efficient route to prepare biodegradable polyesters, such as poly(lactide) (PLA), poly(ε-caprolactone) (PCL), poly(3-hydroxybutyrate) (PHB) and poly(δ-valerolactone) (PVL). The material properties of these polyesters can be further expanded via the formation of block copolymers such as PCL-block-PLA. Suitable catalysis is key to controlling the (co)polymer microstructure and thus the material properties and applications. Bimetallic complexes have been especially efficient at combining high catalytic activities with exquisite polymerisation control, most of which are homometallic with dimeric structures. Both homobimetallic systems based on dinucleating ligands and cooperative heterometallic complexes can offer equally or even more promising activity and selectivity enhancements in cyclic ester ROP, yet remain underexplored. Based on a dinucleating ProPhenol ligand, this work investigates the influence of the (hetero)metal upon the activity and selectivity in cyclic ester ROP and polyester depolymerisation. The in situ generation of metal-alkoxide ROP catalysts from metal-alkyl precursors is often a “black box”, where the species so generated are assumed to be the same as the isolated alkoxide complexes. The work described in Chapter 2 shows that this is not always the case. These studies show that the catalyst aggregation state can significantly impact the activity, with the isolated bis-Zn benzoxide complex displaying a 10-fold activity enhancement in rac-lactide (rac-LA) ROP compared to the in situ generated analogue. The bis-Zn ProPhenol catalyst also offers excellent activities and control over the homopolymerisation of ε-caprolactone (ε-CL) and rac-β-butyrolactone (rac-β-BL). The stability of this isolated catalyst controls chain exchange and back-biting, enabling the one-pot synthesis of multi-block polyesters and the first selective preparation of a PCL-block-PLA-block-PHB terpolymer. The synthesis, characterisation and polymerisation studies of the first heterotrimetallic Na/Zn2 and K/Zn2 ProPhenol complexes are reported in Chapter 3. These complexes deliver “best of both” in cyclic ester ROP, combining the outstanding activity (Na/K) and good control (Zn2) of homometallic analogues. Detailed NMR studies and density-functional theory (DFT) calculations show that the Na/Zn2 and K/Zn2 complexes retain their heterometallic structures in the solution-state. The K/Zn2 analogue displays exceptional activity in rac-LA ROP (kobs = 1.7 x 10-2 s-1), giving activities five times greater than the Na/Zn2 complex. These versatile catalysts also display outstanding performance in ε-CL and δ-valerolactone (δ-VL) ROP. Chapter 4 builds upon the work in Chapter 3 and extends heterometallic cooperativity in ROP to unexplored divalent metal heterocombinations. The Mg/Zn and Ca/Zn ProPhenol complexes outperform their homobimetallic counterparts in rac-LA and ε-CL, with the Ca/Zn analogue exhibiting the highest activity, converting 48 equiv. rac-LA in 5 s and 380 equiv. ε-CL in 30 s at room temperature. The activity enhancements are credited to “ate”-type activation, concurrently amplifying the polarity of the Zn-ethyl/benzoxide bond and Lewis acidity of the Ca centre, thus accelerating the nucleophilic attack and monomer coordination in ROP. These heterometallic complexes also display unusual two-step kinetic plots in rac-LA ROP, which are attributed to catalyst preference for coordination and insertion of L-LA and D-LA stereoisomers of rac-LA, based on detailed kinetic and DFT studies. The concept of accessing heterometallic cooperativity via incorporation of Group 2 inorganic salts into Group 1 homometallic ROP catalysts is demonstrated for the first time in Chapter 5. This methodology provides a simple yet effective strategy for accessing heterometallic cooperativity in ROP. The activity enhancements obtained with salt additives are compared to isolated heterometallic ProPhenol catalysts. Both approaches display similar activity trends, with the K/Mg and K/Ca heterocombinations converting > 85 equiv. rac-LA in just 5 s at room temperature. To the best of our knowledge, these systems are the most active heterometallic rac-LA ROP catalysts reported to date. NMR spectroscopy is employed to probe the catalyst solution-state structures, highlighting the complexity of heterometallic cooperativity in solution. Chapter 6 describes the preliminary results for the selective depolymerisation of polyesters using the Na/Zn2, Ca/Zn, Mg/Zn and bis-Mg ProPhenol complexes. These systems depolymerise PCL and PVL to reform monomers in the presence of just one equivalent of rac-LA or rac-β-BL. The selective depolymerisation is attributed to the combined effect of ligand-mediated transesterification of the inserted PLA or PHB, and the presence of highly Lewis acidic metals (Na, Ca, Mg) that can coordinate the propagating PCL or PVL chains. A depolymerisation mechanism is tentatively proposed based on experimental and NMR spectroscopic studies

Is running a state of mind? : sports training as a potential method for developing cognitive flexibility

Badanie miało na celu sprawdzenie znaczenia uprawiania sportu jako potencjalnego środka poprawy funkcji poznawczych funkcji, w szczególności giętkości poznawczej. W oparciu o cechy biegu na orientację, takie jak częste zmiany strategii behawioralnych w odpowiedzi na zmiany sytuacji lub równoczesne wykonywanie kilku czynności umysłowych, założyliśmy, że uprawianie tego sportu może sprzyjać rozwojowi giętkości poznawczej. Porównano dwie grupy ochotników: 50 biegaczy średnio- i długodystansowych oraz 50 biegaczy na orientację pod względem ich wyników w następujących miarach giętkości poznawczej: zadanie na myślenie rozbieżne, komputerowe zadanie giętkości, Skala Gięktkości Poznawczej i Test Fluencji Werbalnej. Biegacze na orientację osiągnęli lepsze wyniki we wszystkich wskaźnikach z wyjątkiem Skali Giętkości Poznawczej. Ponadto stwierdziliśmy, że cechy treningu (regularność, częstotliwość, udział w zawodach) były związane z poziomy giętkości poznawczej, szczególnie wśród biegaczy na orientację, gdzie wyjaśniały od 38% do 39% ogólnej wariancji giętkości. Nasze wyniki sugerują, że giętkość poznawczą można rozwijać poprzez trening sportowy wymagający efektywnego radzenia sobie w zmieniającym się, złożonym otoczeniu. Omówiono również implikacje prezentowanych wyników badań dotyczących treningu poznawczego.The study aimed to test the significance of sports participation as a potential means of improving cognitive function, particularly cognitive flexibility. Based on the characteristics of orienteering, such as frequent changes of behavioural strategies in response to changes in the situation or the simultaneous performance of several mental activities, we assumed that practising this sport could foster the development of cognitive flexibility. Two groups of volunteers were compared: 50 middle and long-distance runners and 50 orienteering runners in terms of their performance on the following measures of cognitive flexibility: a divergent thinking task, a computer flexibility task, Cognitive Flexibility Scale, and Verbal Fluency Test as a measure of executive function. Orienteering runners outperformed others on all measures except the Cognitive Flexibility Scale. Furthermore, we found that training characteristics (regularity, frequency, participation in competitions) were associated with levels of cognitive flexibility, particularly among orienteering runners, where they explained between 38% and 39% of the overall flexibility variance. Our results suggest that cognitive flexibility can be developed through sports training requiring effective dealing in a changing, complex environment. We also discuss the implications of our results for cognitive training research