Mariana Arismendi

Extensive enriched environments protect old rats from the aging dependent impairment of spatial cognition, synaptic plasticity and nitric oxide production.

In aged rodents, neuronal plasticity decreases while spatial learning and working memory (WM) deficits increase. As it is well known, rats reared in enriched environments (EE) show better cognitive performances and an increased neuronal plasticity than rats reared in standard environments (SE). We hypothesized that EE could preserve the aged animals from cognitive impairment through NO dependent mechanisms of neuronal plasticity. WM performance and plasticity were measured in 27-month-old rats from EE and SE. EE animals showed a better spatial WM performance (66% increase) than SE ones. Cytosolic NOS activity was 128 and 155% higher in EE male and female rats, respectively. Mitochondrial NOS activity and expression were also significantly higher in EE male and female rats. Mitochondrial NOS protein expression was higher in brain submitochondrial membranes from EE reared rats. Complex I activity was 70-80% increased in EE as compared to SE rats. A significant increase in the area of NADPH-d reactive neurons was observed in the parietotemporal cortex and CA1 hippocampal region of EE animals.

On the learnability of frequent and infrequent word orders: An artificial language learning study

Most languages have a basic or “canonical” word order, which determines the relative positions of the subject (S), the verb (V), and the object (O) in a typical declarative sentence. The frequency of occurrence of the six possible word orders among world languages is not distributed uniformly. While SVO and SOV represent around 85% of world languages, orders like VSO (9%) or OSV (0.5%) are much less frequent or extremely rare. One possible explanation for this asymmetry is that biological and cognitive constraints for structured sequence processing make some word orders easier to be processed than others. Therefore, the high frequency of these word orders would be related to their higher learnability. The aim of the present study was to compare the learnability of different word orders between groups of adult subjects. Four artificial languages with different word orders were trained: two frequent (SVO, SOV) and two infrequent (VSO, OSV). In a test stage, subjects were asked to discriminate between new correct sentences and syntax or semantic violations. Higher performance rates and faster responses were observed for more frequent word orders. The results support the hypothesis that more frequent word orders are more easily learned.