No abstract

We studied primary-somatosensory cortical plasticity due to selective stimulation of the sensory periphery by two procedures of active exploration in adult rats. Subjects, left with only three adjacent whiskers, were trained in a roughness discrimination task or maintained in a tactile enriched environment. Either training or enrichment produced 3-fold increases in the barrel cortex areas of behaviorally-engaged whisker representations, in their zones of overlap. While the overall areas of representation expanded dramatically, the domains of exclusive principal whisker responses were virtually identical in enriched vs normal rats and were significantly smaller than either group in roughness discrimination-trained rats. When animals were trained or exposed to enriched environments with the three whiskers arrayed in an arc or row, very equivalent overlaps in representations were recorded across their greatly-enlarged whisker representation zones. This equivalence in distortion in these behavioral preparations is in contradistinction to the normal rat, where overlap is strongly biased only along rows, probably reflecting the establishment of different relations with the neighboring cortical columns. Overall, plasticity phenomena are argued to be consistent with the predictions of competitive Hebbian network plasticity.

Risk perception has been largely examined in studies that have aimed to explain and predict preparedness behavior in the context of natural hazards. Findings from studies on the relationship between previous experience, preparedness, and risk perception in disaster situations have been inconsistent. Hence, the main goal of this work was to explore the influence of physical and emotional experience on risk perception regarding natural hazards. This study was conducted in a statistically representative sample of the city of Iquique, in northern Chile (n = 701), who completed a survey one month after the occurrence of an earthquake and tsunami (8.2 Mw). The survey assessed the experience and preparation actions of survivors in relation to this event. Using a structural equation model, we examined nine proposed relationships, six of which were significant. The final model had an adequate fit (χ ² = 752.23, df = 283, comparative fit index [CFI] = 0.90, root mean square error of approximation [RMSEA] = 0.049). Direct experience showed the greatest influence on risk perception: while direct physical experience (i.e., the physical and material consequences associated with the earthquake) maintained a direct positive effect on risk perception, direct emotional experience (i.e., the fear of experiencing an earthquake) produced an indirect positive effect (through worry). Emotional experience, however, did not directly influence current preparedness and risk perception. Implications for understanding the relationship between risk perception and direct experience are discussed.

(Rev Med Chile 2014; 142: 27-33)

(Rev Med Chile 2014; 142: 716-722)