Involvement of frontal cortex in successive negative contrast

RAFI KLIGER; RUBÉN NÉSTOR MUZIO; MAURICIO ROBERTO PAPINI; MARÍA INÉS SOTELO

Montevideo

Congreso; XII International Congress of Neuroethology; 2016

International Society of Neuroethology

When animals trained to receive a large reward experience a surprising decrease in reward magnitude, their performance deteriorates below the level of a control group always exposed to the small reward magnitude. This phenomenon, called successive negative contrast (SNC) has been found in both consummatory (cSNC) and instrumental (iSNC) procedures. Some authors postulate that the neural mechanisms involved in the cSNC and iSNC are not the same. While there is evidence for the involvement of prefrontal cortex areas in cSNC, no such cortical participation has been reported for iSNC. Lesions in the ventrolateral orbital cortex and the insular cortex suppress the cSNC effect, whereas lesions in the anterior cingulate cortex delay the recovery (i.e., facilitate the cSNC). The goal of this research is to study the role of these areas in an instrumental situation of contrast (iSNC) measuring neural activity. Two groups of rats received one trial per day in a runway situation: 32-4 (rewarded with 32 pellets during 12 daily trials and 4 pellets during other 12 daily trials) and 4-4 (rewarded always with 4 pellets). When animals showed the iSNC effect they were sacrificed. This protocol took place twice. First, brain slices were stained with silver nitrate and nucleolar organizer regions (NORs) sizes were compared. The second time, the c-Fos technique was used to register the neural activation of immediate early genes. Activity between brain areas was compared. The difference between procedures and techniques is discussed.