ole of the ventrolateral orbital cortex and medial prefrontal cortex in ncentive downshift situations

The present research evaluated the role of two prefrontal cortex areas, the ventrolateral orbital cortex (VLO) and the medial prefrontal cortex (mPFC), on two situations involving incentive downshifts, consummatory successive negative contrast (cSNC) with sucrose solutions and Pavlovian autoshaping following continuous vs. partial reinforcement with food pellets. Animals received electrolytic lesions and then were tested on cSNC, autoshaping, open-field activity, and sucrose sensitivity. Lesions of the VLO reduced suppression of consummatory behavior after the incentive downshift, but only during the first downshift trial, and also eliminated the enhancement of anticipatory behavior during partial reinforcement, relative to continuous reinforcement, in autoshaping. There was no evidence of specific effects entrolateral orbital cortex edial prefrontal cortex ats of mPFC lesions on incentive downshifts. Open-field activity was also reduced by VLO lesions, but only in the central area, whereas mPFC lesions had no observable effects on activity. Animals with mPFC lesions exhibited decreased consumption of the lowest sucrose concentration, whereas no effects were observed in animals with VLO lesions. These results suggest that the VLO may exert nonassociative (i.e., motivational, emotional) influences on behavior in situations involving incentive downshifts. No clear role on incentive downshift was revealed by mPFC lesions. The prefrontal cortex (PFC) is a structurally and functionally omplex cortical region. The limits of the PFC can be defined by idirectional connections to thalamic areas, which are relevant or PFC development [1]. Several cortical fields within the rat PFC an be roughly divided in three regions: dorsolateral, medial, and rbital. Not surprisingly, different areas within the PFC are associted to different behaviors and a particular area can be associated o more than one behavior. For instance, lesions of the ventromeial PFC (including infralimbic areas) retarded fear conditioning xtinction [2], while lesions of the orbitofrontal cortex impaired he formation of a negative incentive value for a conditioned ∗ Corresponding author at: Department of Psychology, Texas Christian University, ox 298920, Fort Worth, TX 76129, United States. Tel. : +1 817 257 6084. E-mail address: m.papini@tcu.edu (M.R. Papini). 166-4328/$ – see front matter © 2013 Elsevier B.V. All rights reserved. ttp://dx.doi. org/10.1016/j.bbr. 2013.01. 029 © 2013 Elsevier B.V. All rights reserved. stimulus paired with food (unconditioned stimulus), when the food was later devaluated by pairing it with lithium chloride [3]. In addition, lesions of the orbitofrontal cortex impaired autoshaping acquisition [4]. The PFC is connected, among others, with thalamic nuclei, basal ganglia, and sensory and motor cortices [1]. Miller and Cohen suggested that networks associated with the PFC are in an exceptional location to coordinate a wide array of neural processes and control various types of behaviors [5]. Furthermore, the PFC may be especially relevant for the control of behavior in a top-down manner, as in situations requiring dynamic responses that in turn may involve the organization of sensory/internal inputs, cognitive information, and motivated responses. Thus, the PFC may underlie the coordination of some of the behavioral and motivational adjustments that occur in situations involving incentive downshifts, such as those studied in the present experiment.