Integrated Calendar

What are the sources of trial-to-trial variability in neural responses in early sensory cortical areas and how does this variability affect perceptual decisions? In this talk I will describe results from two studies that aim to address these questions. In the first study, we examined co-variations between behavioral choices of monkeys performing a threshold visual detection task and neural population responses recorded simultaneously from their V1. We found that fluctuations in V1 responses to the same visual stimulus are correlated with fluctuations in perceptual decisions. Our results provide insight regarding the decoding mechanisms that mediate behavior based on V1 responses and suggest that most choice-related variability is already present in V1. Top-down modulations from higher visual cortical areas are one potential source for these decision related signals in V1. The goal of the second study was to characterize two forms of top-down effects in V1: modulations by spatial uncertainty and by stimulus relevance. We found that V1 responses are unaffected by spatial uncertainty, suggesting that target sensitivity is not a limited resource that can be improved by focal attention in V1. Conversely, V1 responses were significantly modulated by stimulus relevance. These modulations are likely to contribute to spatial gating of task-irrelevant information. However, the spatial and temporal characteristics of this top-down signal suggest that it is not a major source of choice-related variability in V1. Our results are therefore consistent with a predominantly bottom-up source of decision related activity in V1.

The main interest of our lab is the process of neuronal migration that occurs during embryonic brain development. In the developing brain neurons are born in one position and have to migrate to their final destination by active cell migration. This is a very dynamic process that is regulated via the concerted action of multiple gene products. In humans this process occurs over the period of several months.

Aberrant neuronal migration may result in devastating consequences, such as severe brain malformation, mental retardation, epileptic seizures and early death. We have concentrated on one severe form of brain malformation, known as lissencephaly, which means "smooth brain". Abnormal neuronal migration has been also associated with mental retardation, Schizophrenia and autism. Our studies have demonstrated that regulation of microtubule dynamics through microtubule associated proteins, microtubule dependent motors and tubulin subunits plays a pivot role in regulation of neuronal migration in the developing brain. An overview of previous and ongoing studies will be presented.

Graphene: From Continuous Layers to Nanostructures

Graphene is a material of great interest in part due to its electronic and thermal transport, mechanical properties, high specific surface area, and that it can act as an atom thick layer barrier or membrane. Application of graphene-based devices utilizing its superior properties, however, requires a method of forming uniform single-layer graphene film on dielectric substrates on a large scale.
In this talk I will review the synthetic methods used so far and will outline the main challenges in achieving large-scale and high quality graphene. Then I will describe our results on the direct chemical vapor deposition of graphene on dielectric surfaces. The main principle of this new approach is the synthesis of graphene on thin metal films pre-deposited on dielectric substrates followed by the dewetting and evaporation of the metal film catalyst leaving the graphene on the bare surface. The use of iso- and anisotropic dewetting of the metal catalyst film for the self-assembly of graphene nanostructures will be discussed. I will also describe our attempts to control the electronic properties of graphene by nanopatterning using nanoimprint and block-copolymers.

The absence of fossil records of prebiologicalsystems strongly hinders our understanding of how life first appeared on Earth. The discovery of catalytic RNA molecules and their key role in central biological processes are consistent with existence of an early RNA World. An alternative, metabolism-first view may be supported by studies such as that proposing a prebiotic role for metalloproteins, based on putative transition metal binding sites in protein components of the translation machinery in hyperthermophiles(Wächtershäuser, Phil Trans R Soc LondB 2006). Exemplifying the power of present-day biology to decide such issues, we have analyzed all fully sequenced genomes of bacteria, archaeaand eukarya and showed lack of support for Wächtershäuser’smodel (Rivas et al., OrigLife EvolBiosph. 2011). More generally, addressing the metabolic-and genetic-first origin-of-life proposals, we show that many of the observations used to argue in favor of one scenario are equally consistent with the other (Lazcano, OrigLife EvolBiosph. 2010). Yet, current biology may well indicate that life could not have evolved in the absence of a genetic replicating mechanisms. Furthermore, I argue that although comparative genomics and deep phylogenies provide important information on early biological evolution, they contribute little to our understanding of the very first transition from the non-living to living. In this respect, complementary insights arise from prebiotic chemistry simulations, as exemplified by our recent analyses of archived samples of an H2S-rich spark discharge experiment of Stanley Miller (1958). They show for the first time the synthesis of sulfur-containing amino acids in an imitated primordial environment (Parker et al., PNAS 2011).


Antonio Lazcanowas twice President of the International Society for the Study of the Origin of Life. He has studied the origin and early evolution of life for over 30 years and is author of several books (in Spanish), including The Origin of Life, with over 650,000 copies sold. Lazcanopromotes the study of evolutionary biology and the origins of life worldwide, and was professor-in-residence or visiting scientist in France, Spain, Cuba, Switzerland, Russia, and the United States.