Abstract
Previous research indicated that monkeys with neonatal perirhinal lesions (Neo-PRh) were impaired on working memory (WM) tasks that generated proactive interference, but performed normally on WM tasks devoid of interference (Weiss et al., 2016). This finding suggested that the early lesions disrupted cognitive processes important for resolving proactive interference, such as behavioral inhibition and cognitive flexibility. To distinguish between these possibilities, the same Neo-PRh monkeys and their controls were tested using the Intradimensional/Extradimensional attentional set-shifting task (Roberts et al., 1988; Dias et al., 1997). Neo-PRh monkeys completed the Simple and Compound Discrimination stages, the Intradimensional Shift stage, and all Reversal stages comparably to controls, but made significantly more errors on the Extradimensional Shift stage of the task. These data indicate that impaired cognitive flexibility was the likely source of increased perseverative errors made by Neo-PRh monkeys when performing WM tasks, rather than impaired behavioral inhibition, and imply that the perirhinal cortex and its interactions with the PFC may play a unique and critical role in the development of attentional set shifting abilities.
Highlights
A recent study reported that adult monkeys with neonatal lesions of the perirhinal cortex (NeoPRh) had working memory (WM) impairments that were characterized by a tendency to make perseverative errors on tasks that generated proactive interference (Weiss et al, 2016)
Lesion studies in monkeys have already demonstrated a double-dissociation between behavioral inhibition supported by the orbitofrontal cortex (OFC), and cognitive flexibility supported by the Impaired Cognitive Flexibility and Perirhinal Lesions ventrolateral prefrontal cortex (Dias et al, 1997; Rogers et al, 2000; Monchi et al, 2001; Burnham et al, 2010; Bissonette et al, 2013)
These results revealed that mechanisms important for visual discrimination learning and behavioral inhibition functioned in the normal range following the early lesions, whereas mechanisms mediating cognitive flexibility were significantly impaired
Summary
A recent study reported that adult monkeys with neonatal lesions of the perirhinal cortex (NeoPRh) had working memory (WM) impairments that were characterized by a tendency to make perseverative errors on tasks that generated proactive interference (Weiss et al, 2016). The same Neo-PRh animals were unimpaired when tested with a WM task that was devoid of interference (Weiss et al, 2016) Taken together, these data suggested that the Neo-PRh lesions may have resulted in difficulty resolving proactive interference, rather than a deficit in WM per se. The increased perseverative errors made by the Neo-PRh monkeys could be due to either a failure to suppress the influence of previously acquired stimulusreward associations (i.e., behavioral inhibition), resulting in repetitive tendencies, or to difficulty shifting attention toward new stimulus-reward associations (i.e., cognitive flexibility), resulting in a tendency to choose the previously rewarded stimulus. The goal of this study was to distinguish between these possible alternatives by characterizing the ability of the same Neo-PRh monkeys to perform a task that taps both capacities, i.e., the Intradimensional-Extradimensional setshifting paradigm (ID-ED) (Roberts et al, 1988)
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