Long-term social recognition memory in adult male rats: factor analysis of the social and non-social behaviors

A modified version of the intruder-resident paradigm was used to investigate if social recognition memory lasts at least 24 h. One hundred and forty-six adult male Wistar rats were used. Independent groups of rats were exposed to an intruder for 0.083, 0.5, 2, 24, or 168 h and tested 24 h after the first encounter with the familiar or a different conspecific. Factor analysis was employed to identify associations between behaviors and treatments. Resident rats exhibited a 24-h social recognition memory, as indicated by a 3- to 5-fold decrease in social behaviors in the second encounter with the same conspecific compared to those observed for a different conspecific, when the duration of the first encounter was 2 h or longer. It was possible to distinguish between two different categories of social behaviors and their expression depended on the duration of the first encounter. Sniffing the anogenital area (49.9 percent of the social behaviors), sniffing the body (17.9 percent), sniffing the head (3 percent), and following the conspecific (3.1 percent), exhibited mostly by resident rats, characterized social investigation and revealed long-term social recognition memory. However, dominance (23.8 percent) and mild aggression (2.3 percent), exhibited by both resident and intruders, characterized social agonistic behaviors and were not affected by memory. Differently, sniffing the environment (76.8 percent of the non-social behaviors) and rearing (14.3 percent), both exhibited mostly by adult intruder rats, characterized non-social behaviors. Together, these results show that social recognition memory in rats may last at least 24 h after a 2-h or longer exposure to the conspecific.

Financial support of graduate programs in Brazil: quo vadis?

Graduate programs provide the highest level of formal education and thus are crucial for the development of any country. However, official Brazilian data clearly show a dramatic decrease in the number and values of scholarships available to graduate programs in Brazil over the last few years, despite the importance and growth of such programs. Between 1995 and 2004, investment by the Coordenadoria de Aperfeiçoamento de Pessoal do Ensino Superior (CAPES, subordinate to the Ministry of Education and Culture) in funding scholarships, corrected for inflation in the period, actually decreased by 51 percent. In addition, during the period between 1994 and 2004, there was a loss of about 60 percent in the purchasing power of the graduate scholarships provided by CAPES and the National Council for Science and Technology (CNPq). To reverse this trend, we propose the development of sectorial funding for Brazilian graduate programs to guarantee the availability and continuity of financial support for this strategic activity.

Rats do react to stimulus omission

1. The great majority of data supporting the hypothesis of a systemcapable of compararing current sensorial imputs with and internal representation of the environment comes from studies about exploratory activity to new stimuli or to manipulation of features of a familiar stimulus. On the other hand, these data could also be explained simply by arousal constructs. In this context, demonstrations of exploratory behavior to the absence of a previously presented stimulus (i.e., stimulus omission) would provide stronger support for the idea of a comparator. 2. To test the reaction of rats to the absence of a stimulus, rats were submitted to 7 exploratory trials in an open-field. In the 1st trial there were only two patterns on the apparatus wall. In trials 2-6 a stimulus was presented in a designated area of the field. Finally, in the 7th trial this stimulus was omitted. Results showed that the animals reacted to the stimulus omission by spending more time in the stimulus presentation place during the 7th trial than 1) in the 1st trial (also without stimulus), 2) in the 6th trial (last trial with a stimulus present), and 3) in 3 neutral sectors of the same size as the stimulus presentation place, during the 7th trial. 3. These data indicated thath rats do react to the absence of a familiar stimulus and provide strong support for the existence of a Comparator System since the rats responded to "something that wasn't there anymore", a response that could only be due to a reaction triggered by a mismatch between internal representation of the environment and its present state