Anticipatory scrs are generated in the time window

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selection of cards from the bad decks versus the good decks. Anticipatory SCRs are generated in the time window before turning a card from any given deck, that is, during the time the subject ponders from which deck to choose ( 2 ). SCRs in association with the good and bad decks from normal controls or patients were not significantly different during the pre-punishment (baseline) period. However, there was a significant increase in the magnitude of these SCRs during the pre-hunchperiod, but only for normal controls. During the next two periods, SCR activity in normal subjects was sustained in the case of the bad decks, but it began to subside in the case of the good decks ( 8 ). (Bottom panels) Bars in the “Behavioral responses” plots represent means ( 6 SEM) of the mean number of cards selected from the bad decks versus those selected from the good decks. Normal controls selected more cards from the good decks during the pre-hunch, hunch, and conceptual periods. In contrast, prefrontal patients selected more cards from the bad decks during these periods ( 9 ). Fig. 2. Diagram of the proposed steps involved in decision-making. SCIENCE z VOL. 275 z 28 FEBRUARY 1997 z 1294 on May 27, 2018 Downloaded from
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Frontal Lobe Function and Dysfunction , H. S. Levin, H. M. Eisenberg, A. L. Benton, Eds. (Oxford Univ. Press, New York, 1991), pp. 217]. See also P. R. Montague, P. Dayan, C. Person, T. J. Sejnowski, Nature 377 , 725 (1995). This action might occur both at the cortical level and in subcortical structures such as basal ganglia. 7. On the basis of a series of related studies [A. Bechara, D. Tranel, H. Damasio, S. W. Anderson, A. R. Damasio, Soc. Neurosci. Abstr. 21 , 1210 (1995); D. Tranel, A. Bechara, H. Damasio, A. R. Damasio, ibid. 22 , 1108 (1996)], we believe that the bias mechanism identified here is distinct from other neural mechanisms whose integrity is crucial for decision- making. Such mecha- nisms include response inhibition [J. M. Fuster, The Pre- frontal Cortex: Anatomy, Physiology, and Neuropsy- chology of the Frontal Lobe (Raven, New York, ed. 3, 1996); R. Dias, T. W. Robbins, A. C. Roberts, Nature 380 , 69 (1996); A. Diamond, in The Development and Neural Bases of Higher Cognitive Functions , A. Dia- mond, Ed. (New York Academy of Sciences, New York, 1990), vol. 608, pp. 637–669], working memory [P. S. Goldman-Rakic, in Handbook of Physiology; The Ner- vous System , F. Plum, Ed. (American Physiological So- ciety, Bethesda, MD, 1987), vol. 5, pp. 373–401], and selective attention [M. I. Posner and S. Dehaene, Trends Neurosci. 17 , 75 (1994)]. In other words, we propose an addition to mechanisms already recognized as neces- sary for proper reasoning rather than an alternative to those mechanisms. 8. A three-way analysis of variance (ANOVA) on the antic- ipatory SCRs generated by normal participants and pa- tients (between group), during the pre-punishment and pre-hunch periods (within group), and in association with the bad and good decks (within group) revealed, most importantly, a significant two-way interaction of group with period [ F (1,14) 5 16.24, P , 0.001]. Subse- quent Newman-Keuls tests on these SCRs revealed that, during the pre-punishment (baseline) period, the SCRs associated with the good or bad decks of nor- mals or patients were not significantly different. Howev-
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