[The role played by the parietooccipital cortex in the process of sensory-motor integration: an electroencephalographic study]. / Participación de la corteza parietooccipital en el proceso de integración sensoriomotora: estudio electroencefalográfico.

INTRODUCTION: A fundamental aspect of planning future actions is the performance and control of motor tasks. This behaviour is done through sensory-motor integration. AIM: To explain the electrophysiological mechanisms in the cortex (modifications to the alpha band) that are involved in anticipatory actions when individuals have to catch a free-falling object. SUBJECTS AND METHODS: The sample was made up of 20 healthy subjects of both sexes (11 males and 9 females) with ages ranging between 25 and 40 years (32.5 +/- 7.5) who were free of mental or physical diseases (previous medical history); the subjects were right-handed (Edinburgh Inventory) and were not taking any psychoactive or psychotropic substances at the time of the study. The experiment consisted in a task in which subjects had to catch freely falling objects. The experiment was made up of six blocks of 15 tests, each of which lasted 2 minutes and 30 seconds, with a break of one minute between blocks. Data were captured by means of a quantitative electroencephalogram two seconds before and two seconds after each ball was dropped. RESULTS: An interaction of the factors moment and position was only observed for the right parietooccipital cortex, in the combination of electrodes P4-O2. CONCLUSION: These findings suggest that the right parietooccipital cortex plays an important role in increasing expectation and swiftness in the processes of preparing for a motor task.

[Learning and implicit memory: mechanisms and neuroplasticity]. / Aprendizaje y memoria implícita: mecanismos y neuroplasticidad.

INTRODUCTION: Learning and memory are complex processes that researchers have been attempting to unravel for over a century in order to gain a clear view of the underlying mechanisms. AIMS: To review the basic cellular and molecular mechanisms involved in the process of procedural retention, to offer an overall view of the fundamental mechanisms involved in storing information by means of theories and models of memory, and to discuss the different types of memory and the role played by the cerebellum as a modulator of procedural memory. DEVELOPMENT: Experimental results from recent decades have opened up new areas of study regarding the participation of the biochemical and cellular processes related to the consolidation of information in the nervous system. CONCLUSIONS: The neuronal circuits involved in acquiring and consolidating memory are still not fully understood and the exact location of memory in the nervous system remains unknown. A number of intrinsic and extrinsic factors interfere in these processes, such as molecular (long-term potentiation and depression) and cellular mechanisms, which respond to communication and transmission between nerve cells. There are also factors that have their origin in the outside environment, which use the association of events to bring about the formation of new memories or may divert the subject from his or her main focus. Memory is not a singular occurrence; it is sub-divided into declarative and non-declarative or, when talking about the time it lasts, into short and long-term memory. Moreover, given its relation with neuronal mechanisms of learning, memory cannot be said to constitute an isolated process.

Bis(acylsilanes) and trifluoromethyltrimethylsilane: a useful system for the synthesis of cyclic 2,2-difluoro-3-trialkylsilyl-1,3-ketols and cyclic 2-fluoro-1,3-diketones(1).

We report a one-pot reaction of bis(acylsilanes) with trifluoromethyltrimethylsilane (TFMTMS) leading to a new family of 2,2-difluoro-3-trialkylsilylketols 4. These compounds were submitted to a facile and effective defluorosilylation. The overall process constitutes a new synthesis of cyclic six- and seven-membered 2-fluoro-1,3-diketones 8, with regiospecific introduction of fluorine. The keto-enol equilibrium of cyclic 1,3-diketones and the mechanism of the defluorosilylation reaction were also studied.

Acetyltrimethylsilane, trifluoromethyltrimethylsilane, and prenyl esters: a three-component system for the synthesis of gem-difluoroanalogues of monoterpenes.

The preparation of 3,3-difluoro-6-methylhept-5-en-2-one 1, a key intermediate for the synthesis of 4,4-difluoroterpenes, and applications in linalool and geraniol series are described. The process involves 1,1-difluoro-2-trimethylsilyoxypropene, an enol silyl ether prepared from acetyltrimethylsilane and trifluoromethyltrimethylsilane, and its reaction in situ with prenyl benzoate, under catalysis by trimethylsilyl trifluoromethanesulfonate. Optimized conditions leading to either the desired enol silyl ether or the unprecedented methyl(trifluoromethyl)trimethylsilyl carbinol 4 have been achieved. The prenylation of the enol silyl ether gives a 9/1 mixture of regioisomers, in favor of the expected ketone 1. Treatment of 1 with vinylmagnesium bromide leads to (+/-)-4,4-difluorolinalool 7. Reaction with the lithium enolate of ethyl diethylphosphonoacetate, and then LAH reduction, converts 1 to 4,4-difluorogeraniol 11, with complete stereoselectivity.

Reactions of difluoroenoxysilanes with glycosyl donors: synthesis of difluoro-C-glycosides and difluoro-C-disaccharides.

Difluoroenoxysilanes, prepared from acylsilanes and trifluoromethyltrimethylsilane under fluoride activation, were glycosylated with some glycosyl donors (acylglycosides, glycals) to yield difluoro-C-glycosides with a difluoromethylene group in the place of the anomeric oxygen. This reaction strongly depends on the substituent in the 2-position of the glycosyl donor. Application of this methodology to a xylose-derived acylsilane led to the formation of difluoro-C-disaccharides as an isosteric O-glycosyl mimetic.

Mixed organofluorine-organosilicon chemistry. 13. One-pot synthesis of difluoroaldols from acylsilanes and trifluoromethyltrimethylsilane. application to the synthesis of a difluoro analogue of egomaketone.

Difluoroaldol compounds 3 were synthesized in a one-pot procedure involving an acylsilane 1, trifluoromethyltrimethylsilane (TFMTMS), and an aldehyde. The key intermediate of this reaction is a difluoroenoxysilane 2. Ytterbium triflate proved to be a very efficient catalyst for promoting the aldol type reaction under very mild conditions. The potential of this reaction for the convergent synthesis of difluorinated compounds was illustrated by the synthesis of difluoroegomaketone 7d through dehydration of the corresponding aldol compound 3d.

Theoretical study of intramolecular aldol condensation of 1, 6-diketones: trimethylsilyl substituent effect

Diastereoselective intramolecular aldol condensations are investigated in an experimental and computational study of 1, 6-diketones. Ab initio results show the importance of the acid medium and disapprove the possibility of a spontaneous cyclization, even for silylated compounds. The combination of both experimental and computational approaches brings valuable information on the mechanism and on the selectivity of the aldol reaction. It is found that the enolization of the diketone is a key step in acid-catalyzed mechanism. The cyclization step bears a very small activation energy. The dehydration of the aldols are discussed.

C-Difluoromethylene-containing, C-trifluoromethyl and C-perfluoroalkyl carbohydrates. Synthesis by carbohydrate transformation or building block methods.

The synthetic methods for preparing carbohydrates bearing a C-branched substituent of the type CF2-Y, with Y = F, Y = CnF(2n + 1) or Y = a carbon-attached or heteroatom-attached nonfluorinated residues, are reviewed. Both direct introduction of C-branched fluorinated substituents (direct trifluoromethylation, perfluoroalkylation or difluoromethylenation) and building block methods from fluorinated synthons are considered.

Formation and properties of Langmuir and Gibbs monolayers: a comparative study using hydrogenated and partially fluorinated amphiphilic derivatives of mannitol.

The synthesis and surface behavior of a series of nine new hydrogenated nonionic surfactants and their fluorinated analogs, derived from D-mannitol are described. Adsorption monolayers (Gibbs monolayers) were studied by surface pressure (H) measurements as a function of time. For the spread monolayers (Langmuir monolayers), the measurements of surface pressure versus molecular area (A) were performed. For the most hydrophobic amphiphiles at low concentrations, the adsorption at the air/water interface from the bulk solution required extremely long times to attain equilibrium. The A values for two compounds which could be studied in both adsorbed and spread monolayers provided data allowing a direct comparison of the properties of the two types of films formed at the air/water interface. In spite of different mechanisms of formation of Langmuir and Gibbs monolayers, their characteristic parameters were identical, proving the equivalence of these two types of structures.