And colleagues describe rats as being “very fearful of the CS.” Adding to the ambiguity is the fact that in a given paper the word fear would sometimes be in quotes and sometimes not, implying that two kinds of fear were being discussed, but without explaining the different uses (37). To try to gain some clarity on the nature of what fear really meant in this literature, I contacted several of the behavioral researchers who played an active role in this work and asked whether they were thinking of fear as a conscious feeling, along the lines of Mowrer, or as an intervening variable that did not imply subjective states. Robert Rescorla, Bruce Overmier, Donald Levis, and Michael Fanselow responded, each noting that they did not view fear as conscious feeling but instead as an empirically defined term based on observable events. (These comments were obtained through e-mail correspondence. Respondents agreed to be quoted.) For example, Rescorla noted: “I do not think that reference to subjective experiences (by which I mean private experiences not subject to independent inter-observer verification) is especially useful.” Fanselow said: “I feel that part of our job is to redefine the concept of motivation in a scientific manner and that those new definitions should replace the layman’s informal view. I don’t see how subjective experience helps us do that.” With the constraints of (��)-Zanubrutinib chemical information behaviorism loosened, animal consciousness is no longer a taboo topic (61?6). Lacking the conceptual and historical foundations needed to navigate the ambiguous use of fear and the subtle issues that were being grappled with by those who treated fear as a nonsubjective intervening variable, readers today (including scientists, journalists, and lay people) are easily drawn toward the conventional meaning of fear as a conscious feeling and to the everyday belief that fearful feelings cause us to respond in a certain way to threats. Let us look at contemporary brain research to see why this view is neither necessary nor desirable.LeDouxConditioned Fear as a Circuit Function In the 1950s, avoidance conditioning became the main task used to explore brain mechanisms of fear and aversive learning (67?2). However, this work led to inconclusive results (4, 68, 69, 73). By the 1980s, researchers interested in learning in mammals and other vertebrates turned to Pavlovian conditioning (74, 75), inspired in part by the successful use of simple conditioning approaches in studies of invertebrates (14, 16, 76, 77). This strategy worked remarkably well, and Pavlovian fear conditioning became the “go-to” method in mammals for studying aversive learning (4, 54, 78), as well as for studies of the relation between emotion and memory (4, 79). The neural circuits and cellular, synaptic, and molecular mechanisms underlying the acquisition and expression of conditioned fear responses have been characterized in detail (4, 5, 53, 80?2). (For a different perspective on the Tulathromycin A manufacturer circuitry, see refs. 49 and 83.) The lateral nucleus of the amygdala (LA) receives sensory inputs about the CS and US. Before training, the CS only weakly activates LA neurons. After the CS is paired with the US, the ability of the CS to activate the LA increases. When the CS later occurs alone, CS activation of the LA leads to neural activity that propagates through amygdala circuits to the central nucleus (CeA). Output connections of CeA then result in the expression of defensive behavior and physiological responses, as we.And colleagues describe rats as being “very fearful of the CS.” Adding to the ambiguity is the fact that in a given paper the word fear would sometimes be in quotes and sometimes not, implying that two kinds of fear were being discussed, but without explaining the different uses (37). To try to gain some clarity on the nature of what fear really meant in this literature, I contacted several of the behavioral researchers who played an active role in this work and asked whether they were thinking of fear as a conscious feeling, along the lines of Mowrer, or as an intervening variable that did not imply subjective states. Robert Rescorla, Bruce Overmier, Donald Levis, and Michael Fanselow responded, each noting that they did not view fear as conscious feeling but instead as an empirically defined term based on observable events. (These comments were obtained through e-mail correspondence. Respondents agreed to be quoted.) For example, Rescorla noted: “I do not think that reference to subjective experiences (by which I mean private experiences not subject to independent inter-observer verification) is especially useful.” Fanselow said: “I feel that part of our job is to redefine the concept of motivation in a scientific manner and that those new definitions should replace the layman’s informal view. I don’t see how subjective experience helps us do that.” With the constraints of behaviorism loosened, animal consciousness is no longer a taboo topic (61?6). Lacking the conceptual and historical foundations needed to navigate the ambiguous use of fear and the subtle issues that were being grappled with by those who treated fear as a nonsubjective intervening variable, readers today (including scientists, journalists, and lay people) are easily drawn toward the conventional meaning of fear as a conscious feeling and to the everyday belief that fearful feelings cause us to respond in a certain way to threats. Let us look at contemporary brain research to see why this view is neither necessary nor desirable.LeDouxConditioned Fear as a Circuit Function In the 1950s, avoidance conditioning became the main task used to explore brain mechanisms of fear and aversive learning (67?2). However, this work led to inconclusive results (4, 68, 69, 73). By the 1980s, researchers interested in learning in mammals and other vertebrates turned to Pavlovian conditioning (74, 75), inspired in part by the successful use of simple conditioning approaches in studies of invertebrates (14, 16, 76, 77). This strategy worked remarkably well, and Pavlovian fear conditioning became the “go-to” method in mammals for studying aversive learning (4, 54, 78), as well as for studies of the relation between emotion and memory (4, 79). The neural circuits and cellular, synaptic, and molecular mechanisms underlying the acquisition and expression of conditioned fear responses have been characterized in detail (4, 5, 53, 80?2). (For a different perspective on the circuitry, see refs. 49 and 83.) The lateral nucleus of the amygdala (LA) receives sensory inputs about the CS and US. Before training, the CS only weakly activates LA neurons. After the CS is paired with the US, the ability of the CS to activate the LA increases. When the CS later occurs alone, CS activation of the LA leads to neural activity that propagates through amygdala circuits to the central nucleus (CeA). Output connections of CeA then result in the expression of defensive behavior and physiological responses, as we.
