Reward learning gives rise to strong attentional biases. Stimuli previously associated with rewar... more Reward learning gives rise to strong attentional biases. Stimuli previously associated with reward automatically capture visual attention regardless of intention [1-12]. Dopamine signaling within the ventral striatum plays an important role in reward learning, representing the expected reward initiated by a cue [13, 14]. How dopamine and the striatum may be involved in maintaining behaviors that have been shaped by reward learning, even after reward expectancies have changed, is less well understood [15]. Nonspecific measures of brain activity have implicated the striatum in value-based attention [11, 12, 16-18]. However, the neurochemical mechanisms underlying the attentional priority of learned reward cues remain unexplored. Here, we investigated the contribution of dopamine to value-based attention using positron emission tomography (PET) with [(11)C]raclopride. We show that, in the explicit absence of reward, the magnitude of attentional capture by previously reward-associated b...
The physiological functioning of the brain is not well-known in current day medicine and the path... more The physiological functioning of the brain is not well-known in current day medicine and the pathologies of many neuropsychiatric disorders are still not yet fully understood. With our aging population and better life expectancies, it has become imperative to find better biomarkers for disease progression as well as receptor target engagements. In the last decade, these major advances in the field of molecular CNS imaging have been made available with tools such as functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy (MRS), single photon emission computed tomography (SPECT), and neuroreceptor-targeted positron emission tomography (PET). These tools have given researchers, pharmaceutical companies, and clinical physicians a better method of understanding CNS dysfunctions, and the ability to employ improved therapeutic agents. This review is intended to provide an update on brain imaging agents that are currently used in clinical and translational research toward treatment of CNS disorders. The review begins with amyloid and tau imaging, the former of which has at least three [(18)F] agents that have been recently approved and will soon be available for clinical use for specific indications in the USA and elsewhere. Other prevalent PET and SPECT neurotransmitter system agents, including those newly US FDA-approved imaging agents related to the dopaminergic system, are included. A review of both mature and potentially growing PET imaging agents, including those targeting serotonin and opiate receptor systems, is also provided.
Molecular imaging and biology : MIB : the official publication of the Academy of Molecular Imaging, 2014
Using the α7-nAChR radiotracer, [(18)F]ASEM, we present the first successful human positron emiss... more Using the α7-nAChR radiotracer, [(18)F]ASEM, we present the first successful human positron emission tomography (PET) studies. Rodent occupancy with three clinically employed α7-nAChR drugs confirms the specificity of the radiotracer. Five healthy male subjects were imaged for 90 min following IV [(18)F]ASEM. Two subjects were scanned for the second time (test/retest; TRV). Mouse biodistribution of [(18)F]ASEM was carried out in CD1 mice injected with using human equivalent doses of DMXB-A, EVP-6124, and varenicline to block specific binding. [(18)F]ASEM readily entered the brain and peaked at 15 min post-injection with reversible kinetics and a peak %SUV of about 400 %. The regional human brain distribution of [(18)F]ASEM matched previous in vitro data and baboon PET results. The precuneus, parietal, occipital, cingulate cortexes, putamen, and thalamus showed high values of distribution volume (>20 ml/ml) and binding potentials >1 with TRV averaged 10.8 ± 5.1 %. In mouse dist...
ABSTRACT The gauge theory for the Poincaré -Weyl group is constructed. It is shown that tetrads a... more ABSTRACT The gauge theory for the Poincaré -Weyl group is constructed. It is shown that tetrads are not true gauge fields, but are functions of the true gauge fields: rotational, translational and dilatational ones. The equations of gauge fields, whose sources are an energy-momentum tensor, orbital and spin momemta as well as a dilatational current of an external field, are obtained. A new direct interaction of the rotational gauge field with the orbital momentum of an external field appears, which describes some new effects connected with the space gyroscope Probe B experiment.
ABSTRACT Based on the requirement that the gauge invariance principle for the Poincaré-Weyl group... more ABSTRACT Based on the requirement that the gauge invariance principle for the Poincaré-Weyl group be satisfied for the space-time manifold, we construct a model of space-time with the geometric structure of a Weyl-Cartan space. We show that three types of fields must then be introduced as the gauge (“compensating”) fields: Lorentz, translational, and dilatational. Tetrad coefficients then become functions of these gauge fields. We propose a geometric interpretation of the Dirac scalar field. We obtain general equations for the gauge fields, whose sources can be the energy-momentum tensor, the total momentum, and the total dilatation current of an external field. We consider the example of a direct coupling of the gauge field to the orbital momentum of the spinor field. We propose a gravitational field Lagrangian with gauge-invariant transformations of the Poincaré-Weyl group.
ABSTRACT Based on the Lie derivative technique in a general space with affine connection (L4, g),... more ABSTRACT Based on the Lie derivative technique in a general space with affine connection (L4, g), we show that in the metric-affine theory of gravitation, the law of conservation of the energy-momentum tensor for matter and consequently also the equations of motion for matter stemming from this law are (as in the general theory of relativity) a consequence of the gravitational field equations. We derive the hydrodynamic equation of motion for an ideal Weyssenhoff---Raabe spin fluid in Weyl space. We discuss the possibilities for observation of space---time nonmetricity.
The solution of the field equations of the conformal theory of gravitation with Dirac scalar fiel... more The solution of the field equations of the conformal theory of gravitation with Dirac scalar field in Cartan-Weyl spacetime at the very early Universe is obtained. In this theory dark energy (described by an effective cosmological constant) is a function of the Dirac scalar fieldβ. This solution describes the exponential decreasing ofβat the inflation stage and has a limit to a constant value of the dark energy at large time. This can give a way to solving the fundamental cosmological constant problem as a consequence of the fields dynamics in the early Universe.
The existence of the Pontryagin and Euler forms in a Weyl-Cartan space on the basis of the variat... more The existence of the Pontryagin and Euler forms in a Weyl-Cartan space on the basis of the variational method with Lagrange multipliers are established. It is proved that these forms can be expressed via the exterior derivatives of the corresponding Chern-Simons terms in a Weyl-Cartan space with torsion and nonmetricity.
The variational theory of the perfect hypermomentum fluid is developed. The new type of the gener... more The variational theory of the perfect hypermomentum fluid is developed. The new type of the generalized Frenkel condition is considered. The Lagrangian density of such fluid is stated, and the equations of motion of the fluid and the Weyssenhoff-type evolution equation of the hypermomentum tensor are derived. The expressions of the matter currents of the fluid (the canonical energy-momentum 3-form, the metric stress-energy 4-form and the hypermomentum 3-form) are obtained. The special case of the dilaton-spin fluid with intrinsic spin and dilatonic charge is considered.
On the basis of the Lie derivative method in a metric-affine space-time it is shown that in the m... more On the basis of the Lie derivative method in a metric-affine space-time it is shown that in the metric-affine gravitational theory the energy-momentum conservation law and therefore the equations of the matter motion are the consequence (as in the GR) of the gravitational field equations. The possi- bility of the detection of the space-time non-metric properties is discussed.
The ionization front induced by a relativistic high-density electron beam in gas was studied in 1... more The ionization front induced by a relativistic high-density electron beam in gas was studied in 1D approximation. We extended the approach of [1] to the relativistic beam energies and calculated the ionization front velocity for a wide range of beam energies and gas densities. The asymptotic expressions for the ionization front velocity were found in the limits of small and
Afterglow stage of plasma/gas temporal evolution in the ife chamber plays very important role bot... more Afterglow stage of plasma/gas temporal evolution in the ife chamber plays very important role both for protection of the chamber first wall from plasma impact damage and for favorable conditions of next pellet injection which will follow in a time scale 0.1s [1]. In this report we analyze main physics processes leading to residual gas/plasma cooling and plasma recombination. We develop a time dependent numerical model to study the effects of large convective cells, plasma/gas radiation opacity on cooling and recombination processes. We discuss the impact of residual plasma and radiation field on the heat flux to the target. [1] S. I. Krasheninnikov, "IFE Dry Wall Chamber Physics Issues", 29th EPS Conference on Plasma Physics and Controlled Fusion, 17-21 June 2002, Montreux, Switzerland
Reward learning gives rise to strong attentional biases. Stimuli previously associated with rewar... more Reward learning gives rise to strong attentional biases. Stimuli previously associated with reward automatically capture visual attention regardless of intention [1-12]. Dopamine signaling within the ventral striatum plays an important role in reward learning, representing the expected reward initiated by a cue [13, 14]. How dopamine and the striatum may be involved in maintaining behaviors that have been shaped by reward learning, even after reward expectancies have changed, is less well understood [15]. Nonspecific measures of brain activity have implicated the striatum in value-based attention [11, 12, 16-18]. However, the neurochemical mechanisms underlying the attentional priority of learned reward cues remain unexplored. Here, we investigated the contribution of dopamine to value-based attention using positron emission tomography (PET) with [(11)C]raclopride. We show that, in the explicit absence of reward, the magnitude of attentional capture by previously reward-associated b...
The Gauss-Bonnet type identity is derived in a Weyl-Cartan space on the basis of the variational ... more The Gauss-Bonnet type identity is derived in a Weyl-Cartan space on the basis of the variational method.
The harmonicity condition of the curvature 2-form of a pseudo- Riemannian manifold is formulated ... more The harmonicity condition of the curvature 2-form of a pseudo- Riemannian manifold is formulated on the basis of annulment of this form by the de Rham-Lichnerowicz Laplacian. The following theorem is proved: The curvature 2-form of any Einstein manifold is harmonic.
ABSTRACT We have developed new methods of using symbolic computer calculations for four- and high... more ABSTRACT We have developed new methods of using symbolic computer calculations for four- and higher-dimensional, geometrically generalized spaces. In particular, we work with differential identities in order to check the variational field equations of a conformal theory of gravity with a scalar field in Weyl-Cartan space. To simplify the navigation, we have worked out a graphic user interface, making it possible to solve problems of a post-Riemannian theory of gravity in Weyl-Cartan space, as well as those of the Kaluza-Klein five-dimensional unified theory of gravity and electromagnetism, in particular, in the external form formalism.
Reward learning gives rise to strong attentional biases. Stimuli previously associated with rewar... more Reward learning gives rise to strong attentional biases. Stimuli previously associated with reward automatically capture visual attention regardless of intention [1-12]. Dopamine signaling within the ventral striatum plays an important role in reward learning, representing the expected reward initiated by a cue [13, 14]. How dopamine and the striatum may be involved in maintaining behaviors that have been shaped by reward learning, even after reward expectancies have changed, is less well understood [15]. Nonspecific measures of brain activity have implicated the striatum in value-based attention [11, 12, 16-18]. However, the neurochemical mechanisms underlying the attentional priority of learned reward cues remain unexplored. Here, we investigated the contribution of dopamine to value-based attention using positron emission tomography (PET) with [(11)C]raclopride. We show that, in the explicit absence of reward, the magnitude of attentional capture by previously reward-associated b...
The physiological functioning of the brain is not well-known in current day medicine and the path... more The physiological functioning of the brain is not well-known in current day medicine and the pathologies of many neuropsychiatric disorders are still not yet fully understood. With our aging population and better life expectancies, it has become imperative to find better biomarkers for disease progression as well as receptor target engagements. In the last decade, these major advances in the field of molecular CNS imaging have been made available with tools such as functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy (MRS), single photon emission computed tomography (SPECT), and neuroreceptor-targeted positron emission tomography (PET). These tools have given researchers, pharmaceutical companies, and clinical physicians a better method of understanding CNS dysfunctions, and the ability to employ improved therapeutic agents. This review is intended to provide an update on brain imaging agents that are currently used in clinical and translational research toward treatment of CNS disorders. The review begins with amyloid and tau imaging, the former of which has at least three [(18)F] agents that have been recently approved and will soon be available for clinical use for specific indications in the USA and elsewhere. Other prevalent PET and SPECT neurotransmitter system agents, including those newly US FDA-approved imaging agents related to the dopaminergic system, are included. A review of both mature and potentially growing PET imaging agents, including those targeting serotonin and opiate receptor systems, is also provided.
Molecular imaging and biology : MIB : the official publication of the Academy of Molecular Imaging, 2014
Using the α7-nAChR radiotracer, [(18)F]ASEM, we present the first successful human positron emiss... more Using the α7-nAChR radiotracer, [(18)F]ASEM, we present the first successful human positron emission tomography (PET) studies. Rodent occupancy with three clinically employed α7-nAChR drugs confirms the specificity of the radiotracer. Five healthy male subjects were imaged for 90 min following IV [(18)F]ASEM. Two subjects were scanned for the second time (test/retest; TRV). Mouse biodistribution of [(18)F]ASEM was carried out in CD1 mice injected with using human equivalent doses of DMXB-A, EVP-6124, and varenicline to block specific binding. [(18)F]ASEM readily entered the brain and peaked at 15 min post-injection with reversible kinetics and a peak %SUV of about 400 %. The regional human brain distribution of [(18)F]ASEM matched previous in vitro data and baboon PET results. The precuneus, parietal, occipital, cingulate cortexes, putamen, and thalamus showed high values of distribution volume (>20 ml/ml) and binding potentials >1 with TRV averaged 10.8 ± 5.1 %. In mouse dist...
ABSTRACT The gauge theory for the Poincaré -Weyl group is constructed. It is shown that tetrads a... more ABSTRACT The gauge theory for the Poincaré -Weyl group is constructed. It is shown that tetrads are not true gauge fields, but are functions of the true gauge fields: rotational, translational and dilatational ones. The equations of gauge fields, whose sources are an energy-momentum tensor, orbital and spin momemta as well as a dilatational current of an external field, are obtained. A new direct interaction of the rotational gauge field with the orbital momentum of an external field appears, which describes some new effects connected with the space gyroscope Probe B experiment.
ABSTRACT Based on the requirement that the gauge invariance principle for the Poincaré-Weyl group... more ABSTRACT Based on the requirement that the gauge invariance principle for the Poincaré-Weyl group be satisfied for the space-time manifold, we construct a model of space-time with the geometric structure of a Weyl-Cartan space. We show that three types of fields must then be introduced as the gauge (“compensating”) fields: Lorentz, translational, and dilatational. Tetrad coefficients then become functions of these gauge fields. We propose a geometric interpretation of the Dirac scalar field. We obtain general equations for the gauge fields, whose sources can be the energy-momentum tensor, the total momentum, and the total dilatation current of an external field. We consider the example of a direct coupling of the gauge field to the orbital momentum of the spinor field. We propose a gravitational field Lagrangian with gauge-invariant transformations of the Poincaré-Weyl group.
ABSTRACT Based on the Lie derivative technique in a general space with affine connection (L4, g),... more ABSTRACT Based on the Lie derivative technique in a general space with affine connection (L4, g), we show that in the metric-affine theory of gravitation, the law of conservation of the energy-momentum tensor for matter and consequently also the equations of motion for matter stemming from this law are (as in the general theory of relativity) a consequence of the gravitational field equations. We derive the hydrodynamic equation of motion for an ideal Weyssenhoff---Raabe spin fluid in Weyl space. We discuss the possibilities for observation of space---time nonmetricity.
The solution of the field equations of the conformal theory of gravitation with Dirac scalar fiel... more The solution of the field equations of the conformal theory of gravitation with Dirac scalar field in Cartan-Weyl spacetime at the very early Universe is obtained. In this theory dark energy (described by an effective cosmological constant) is a function of the Dirac scalar fieldβ. This solution describes the exponential decreasing ofβat the inflation stage and has a limit to a constant value of the dark energy at large time. This can give a way to solving the fundamental cosmological constant problem as a consequence of the fields dynamics in the early Universe.
The existence of the Pontryagin and Euler forms in a Weyl-Cartan space on the basis of the variat... more The existence of the Pontryagin and Euler forms in a Weyl-Cartan space on the basis of the variational method with Lagrange multipliers are established. It is proved that these forms can be expressed via the exterior derivatives of the corresponding Chern-Simons terms in a Weyl-Cartan space with torsion and nonmetricity.
The variational theory of the perfect hypermomentum fluid is developed. The new type of the gener... more The variational theory of the perfect hypermomentum fluid is developed. The new type of the generalized Frenkel condition is considered. The Lagrangian density of such fluid is stated, and the equations of motion of the fluid and the Weyssenhoff-type evolution equation of the hypermomentum tensor are derived. The expressions of the matter currents of the fluid (the canonical energy-momentum 3-form, the metric stress-energy 4-form and the hypermomentum 3-form) are obtained. The special case of the dilaton-spin fluid with intrinsic spin and dilatonic charge is considered.
On the basis of the Lie derivative method in a metric-affine space-time it is shown that in the m... more On the basis of the Lie derivative method in a metric-affine space-time it is shown that in the metric-affine gravitational theory the energy-momentum conservation law and therefore the equations of the matter motion are the consequence (as in the GR) of the gravitational field equations. The possi- bility of the detection of the space-time non-metric properties is discussed.
The ionization front induced by a relativistic high-density electron beam in gas was studied in 1... more The ionization front induced by a relativistic high-density electron beam in gas was studied in 1D approximation. We extended the approach of [1] to the relativistic beam energies and calculated the ionization front velocity for a wide range of beam energies and gas densities. The asymptotic expressions for the ionization front velocity were found in the limits of small and
Afterglow stage of plasma/gas temporal evolution in the ife chamber plays very important role bot... more Afterglow stage of plasma/gas temporal evolution in the ife chamber plays very important role both for protection of the chamber first wall from plasma impact damage and for favorable conditions of next pellet injection which will follow in a time scale 0.1s [1]. In this report we analyze main physics processes leading to residual gas/plasma cooling and plasma recombination. We develop a time dependent numerical model to study the effects of large convective cells, plasma/gas radiation opacity on cooling and recombination processes. We discuss the impact of residual plasma and radiation field on the heat flux to the target. [1] S. I. Krasheninnikov, "IFE Dry Wall Chamber Physics Issues", 29th EPS Conference on Plasma Physics and Controlled Fusion, 17-21 June 2002, Montreux, Switzerland
Reward learning gives rise to strong attentional biases. Stimuli previously associated with rewar... more Reward learning gives rise to strong attentional biases. Stimuli previously associated with reward automatically capture visual attention regardless of intention [1-12]. Dopamine signaling within the ventral striatum plays an important role in reward learning, representing the expected reward initiated by a cue [13, 14]. How dopamine and the striatum may be involved in maintaining behaviors that have been shaped by reward learning, even after reward expectancies have changed, is less well understood [15]. Nonspecific measures of brain activity have implicated the striatum in value-based attention [11, 12, 16-18]. However, the neurochemical mechanisms underlying the attentional priority of learned reward cues remain unexplored. Here, we investigated the contribution of dopamine to value-based attention using positron emission tomography (PET) with [(11)C]raclopride. We show that, in the explicit absence of reward, the magnitude of attentional capture by previously reward-associated b...
The Gauss-Bonnet type identity is derived in a Weyl-Cartan space on the basis of the variational ... more The Gauss-Bonnet type identity is derived in a Weyl-Cartan space on the basis of the variational method.
The harmonicity condition of the curvature 2-form of a pseudo- Riemannian manifold is formulated ... more The harmonicity condition of the curvature 2-form of a pseudo- Riemannian manifold is formulated on the basis of annulment of this form by the de Rham-Lichnerowicz Laplacian. The following theorem is proved: The curvature 2-form of any Einstein manifold is harmonic.
ABSTRACT We have developed new methods of using symbolic computer calculations for four- and high... more ABSTRACT We have developed new methods of using symbolic computer calculations for four- and higher-dimensional, geometrically generalized spaces. In particular, we work with differential identities in order to check the variational field equations of a conformal theory of gravity with a scalar field in Weyl-Cartan space. To simplify the navigation, we have worked out a graphic user interface, making it possible to solve problems of a post-Riemannian theory of gravity in Weyl-Cartan space, as well as those of the Kaluza-Klein five-dimensional unified theory of gravity and electromagnetism, in particular, in the external form formalism.
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Papers by Boris Frolov