Classic studies of lateral geniculate nucleus (LGN) and visual cortex (V1) in carnivores and primates have found that a majority of neurons in LGN exhibit a center-surround organization, while V1 neurons exhibit strong orientation selectivity and, in many species, direction selectivity. This has led to the prevailing model that orientation and direction selectivity are computed anew in the cort...

R e s u m e n En un artículo reciente, Eastwick, Finkel, Mochon y Ariely (2007) reportaron datos que indicaban que la selectividad podría ser un factor importante para determinar el deseo romántico. Usando un paradigma de citas rápidas, se encontró que los individuos que en promedio calificaron posibles citas como altamente deseables eran los que recibían más bajas calificaciones en promedio de...

Let A be a quaternion algebra over a number field K and assume that A satisfies the Eichler condition; that is, there exists an archimedean prime of K which does not ramify in A. Let Ω be a commutative, quadratic OK-order and let R ⊂ A be an order. We determine the isomorphism classes in the genus of R which admit an embedding of Ω. In particular, we show that the proportion of the genus of R a...

Selectivity to visual stimulus orientation is a basic cortical functional property believed to be crucial for normal vision. Maturation of this neuronal property requires neural activity. Still, it is unclear what might be the molecular basis for such activity-dependent processes and whether activity has an instructive or permissive role in development of orientation selectivity. There is stron...

Pharmacological block of inhibition is often used to determine if inhibition contributes to spike selectivity, in which a preferred stimulus evokes more spikes than a null stimulus. When inhibitory block reduces spike selectivity, a common interpretation is that differences between the preferred- and null-evoked inhibitions created the selectivity from less-selective excitatory inputs. In model...

We introduce a generalization of Selman's P-selectivity that yields a more exible notion of selectivity, called (polynomial-time) multi-selectivity, in which the selector is allowed to operate on multiple input strings. Since our introduction of this class, it has been used [HJRW96] to prove the rst known (and optimal) lower bounds for generalized selectivity-like classes in terms of EL2, the s...

Lattice supports single bilayer he spherical membrane surrounding the poxvirus genome begins to form as an open, cup-like structure. Some have argued that the edge of the cup must be composed of two closely apposed membranes (imagine a collapsed vesicle); otherwise, the hydrophobic edges of a single membrane would be exposed to the cytoplasm. But on page 269, John Heuser confirms that poxvirus ...

Lactococcus lactis metabolizes glucose homofermentatively to lactate. However, after disruption of the gene coding for lactate dehydrogenase, LDH , a key enzyme in NAD regeneration, the glycolytic flux shifts from homolactic to mixed-acid fermentation with the redirection of pyruvate towards production of formate, acetate, ethanol and CO2. A mathematical model of the pyruvate metabolism pathway...

Given two sets S1, S2 of moving objects, a future timestamp tq, and a distance threshold d, a spatio-temporal join retrieves all pairs of objects that are within distance d at tq. The selectivity of a join equals the number of retrieved pairs divided by the cardinality of the Cartesian product S1 S2. This paper develops a model for spatio-temporal join selectivity estimation based on rigorous p...

In a variety of settings from relational databases to LDAP to Web applications, there is an increasing need to quickly and accurately estimate the count of tuples (LDAP entries, Web documents, etc.) matching Boolean substring queries. In providing such selectivity estimates, the correlation between different occurrences of substrings is crucial. Selectivity estimation for generalized Boolean qu...