Past events

A fundamental question in systems neuroscience is: What are the organization principles of human visual cortex? Visual cortex originates in primary visual cortex and extends through a hierarchy of early, intermediate, and high-level visual regions separated across two processing streams (dorsal and ventral). While much is known about the organization of early visual cortex, much less is known about the organization of high-level visual regions in the ventral stream, which are thought to be involved in visual recognition. Current theories suggest functional distinctions between early and high-level regions in the ventral processing stream: early and intermediate visual regions contain a systematic representation of the visual field across a series of multiple maps (Wandell and Winawer, 2011), whereas higher-level regions are thought to be specialized for processing specific types of stimuli such as objects, faces, body parts, words, and places (Kanwisher, 2010). Several alternative theories suggest other principles for the organization of the ventral stream, including expertise (Tarr and Gauthier, 2000), eccentricity biases (Malach et al., 2002), or distributed representations (Haxby et al., 2001; Kriegeskorte et al., 2008). Nevertheless, two notions are common to these theories. First, it is widely accepted that different rules underlie the functional organization of high-level and early visual cortex. Second, the profile of activations in high-level visual cortex is thought to be more variable across individuals compared to early visual cortex. Contrary to the prevailing view, we propose common organization principles throughout early and high-level visual cortex, where functional regions have consistent anatomical locations and preserved spatial relationships to neighboring regions as well as retinotopic maps. Employing these principles enables the first framework for consistent parcellation of high-level visual regions, which can also be applied to other sensory and nonsensory cortical systems.

In my talk I will present a generalized view of dendritic function in neocortical pyramidal neurons summarizing a decade of research. Later I will present two yet unpublished works. The first will describe dendritic integration in layer 4 spiny stellate neurons and the role of dendritic spikes in-vivo. The second work will present coding of texture in layer 2-3 neurons in the rat barrel cortex using two photon imaging methods.

Adolescence is a period of major physical, hormonal and psychological change. It is also characterized by a significant increase in the incidence of psychopathologies and this increase is gender-specific. Likewise, stress during adolescence is associated with the development of psychiatric disorders later in life. Here, we study the immediate impact of psychogenic stress before and during puberty (postnatal days 28-42) on behavior (novelty seeking, risk taking, anxiety and depression) and hypothalamus-pituitary-adrenocortical (HPA) axis activation and brain metabolism during late adolescence (postnatal days 45-51). Peri-pubertal stress: a) decreased anxiety-like behavior and increased risk taking and novelty seeking behaviors during late adolescence; b) did not affect depressive-like behavior; c) decreased fear memories (freezing in response to a tone associated with electrical shock) only in females; d) did not affect brain activation on basal conditions (home cage) but increase activation of hippocampus, basal amygdala, cingulated and motor cortices when the animals underwent recall of a tone associated to electrical shock; and e) did not affect acute HPA response to stress (blood corticosterone and glucose). Interestingly, when controlling for the basal anxiety of the mothers, animals exposed to peri-pubertal stress showed a significant decrease in corticosterone levels right after an acute stressor. The results from this study suggest that exposure to mild stressors during the peri-pubertal period induces a broad spectrum of behavioral and brain activation changes in late adolescence, which seems to exacerbate the independence-building behaviors naturally happening during this transitional period (increase in curiosity, sensation-seeking and risk taking behaviors).