اثر متفاوت غیر فعال شدن کورتکس اربیتوفرونتال بر استراتژی تغییر و آموزش معکوس

Different subregions of the rodent prefrontal cortex (PFC) mediate dissociable types of behavioral flexibility. For example, lesions of the medial or orbitofrontal (OFC) regions of the PFC impair extradimensional shifts and reversal learning, respectively, when novel stimuli are used during different phases of the task. In the present study, we assessed the effects of inactivation of the OFC on strategy set-shifting and reversal learning, using a maze based set-shifting task mediated by the medial PFC. Long–Evans rats were trained initially on a visual-cue discrimination to obtain food. On the subsequent day, rats had to shift to using a response strategy (e.g., always turn left). On Day 3 (reversal), rats were required to reverse the direction of their turn (e.g., always turn right). Infusions of the local anesthetic bupivacaine into the OFC did not impair initial visual discrimination learning, nor did it impair performance on the set-shift. In contrast, inactivation of the OFC did impair reversal learning; yet, these rats ceased using the previously acquired response rule as readily as controls. Instead, rats receiving OFC inactivations made a disproportionate number of erroneous arm entries towards the visual-cue, suggested that these animals reverted back to using the original visual-cue based strategy. These findings, in addition to previous data, further support the notion that the OFC and medial PFC play dissociable roles in reversal learning and set-shifting. Furthermore, the lack of effect of OFC inactivations on the set-shift indicates that this type of behavioral flexibility does not require cognitive operations related to reversal learning.

The ability to alter behavioral strategies and adapt to changes in one’s environment is mediated by interactions between different cortical and subcortical brain regions. Studies across mammalian species have strongly implicated different subregions of the prefrontal cortex (PFC) in mediating distinct forms of behavioral flexibility. For instance, inactivations or lesions of the medial PFC in rodents disrupt the acquisition of novel strategies, rules or attentional sets, impairing the inhibition of a previously relevant strategy (Birrell and Brown, 2000, Floresco et al., 2006a and Ragozzino et al., 1999). In contrast, reversal learning, a simpler form of behavioral flexibility that entails shifting between different stimulus-reward associations, is impaired by lesions of the orbitofrontal region of the PFC (OFC), while set-shifting remains unaffected with similar lesions (Birrell and Brown, 2000, Chudasasma et al., 2001 and McAlonan and Brown, 2003).