Schoenbaum Geoffrey, Saddoris Michael P, Stalnaker Thomas A
Department of AAnatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Ann N Y Acad Sci. 2007 Dec;1121:320-35. doi: 10.1196/annals.1401.001. Epub 2007 Aug 14.
Damage to orbitofrontal cortex (OFC) has long been associated with decision-making deficits. Such deficits are epitomized by impairments in reversal learning. Historically, reversal learning deficits have been linked to a response inhibition function or to the rapid reversal of associative encoding in OFC neurons. However here we will suggest that OFC supports reversal learning not because its encoding is particularly flexible-indeed it actually is not-but rather because output from OFC is critical for flexible associative encoding downstream in basolateral amygdala (ABL). Consistent with this argument, we will show that reversal performance is actually inversely related to the flexibility of associative encoding in OFC (i.e., the better the reversal performance, the less flexible the encoding). Further, we will demonstrate that associative correlates in ABL are more flexible during reversal learning than in OFC, become less flexible after damage to OFC, and are required for the expression of the reversal deficit caused by OFC lesions. We will propose that OFC facilitates associative flexibility in downstream regions, such as ABL, for the same reason that it is critical for outcome-guided behavior in a variety of setting-namely that processing in OFC signals the value of expected outcomes. In addition to their role in guiding behavior, these outcome expectancies permit the rapid recognition of unexpected outcomes, thereby driving new learning.
眶额皮质(OFC)受损长期以来一直与决策缺陷相关。这种缺陷在反转学习障碍中表现得最为典型。从历史上看,反转学习缺陷与反应抑制功能或OFC神经元中联想编码的快速反转有关。然而,在这里我们将提出,OFC支持反转学习,并非因为其编码特别灵活——实际上它并非如此——而是因为OFC的输出对于基底外侧杏仁核(ABL)下游的灵活联想编码至关重要。与这一观点一致,我们将表明反转表现实际上与OFC中联想编码的灵活性呈负相关(即反转表现越好,编码的灵活性越低)。此外,我们将证明,ABL中的联想相关性在反转学习过程中比在OFC中更灵活,在OFC受损后变得不那么灵活,并且是OFC损伤导致的反转缺陷表达所必需的。我们将提出,OFC促进下游区域(如ABL)的联想灵活性,原因与它在各种情况下对结果导向行为至关重要相同,即OFC中的处理表明预期结果的价值。除了在指导行为中的作用外,这些结果预期还允许快速识别意外结果,从而推动新的学习。
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