D UCS converges on the amygdala, allowing associative connections to form in BX795 side effects amygdala synapses, and subsequent reexposure to the CS activates output cells within the central nucleus (Ledoux, 2000; Kim and Jung, 2006). Although fear learning appears to be one of the primary functions of the amygdala, there is also ample evidence to suggest the amygdala is engaged in other types of psychological phenomena.Received: 1 December 2014; Revised: 27 March 2015. Accepted: 7 MayC V The Author (2015). Published by Oxford University Press. For Permissions, please email: [email protected]|Social Cognitive and Affective Neuroscience, 2015, Vol. 10, No.In several recent articles, our lab and others have found that the amygdala responds to simple stimulus novelty (Wright et al., 2003; Blackford et al., 2010; Weierich et al., 2010; Balderston et al., 2011). For example, we compared novel and repeated images of faces and scenes. We found that novel faces, but not scenes, evoked larger responses than repeated stimuli of the same type. In addition, we found that this novelty effect was due to a response evoked by the initial presentation of a unique face; this response was not evoked on subsequent presentations (Balderston et al., 2011). This was clearly the case even for emotionally neutral faces, which is notable given the large literature suggesting that angry and fearful faces preferentially activate the amygdala (Gamer and Buchel, 2009; Whalen et al., 1998, 2001, 2004). ?One possible explanation for this novelty effect evoked by neutral faces is that the amygdala’s response to novelty represents the processing necessary to initially identify threats in the environment, while fear responses represent the actual response to an identified threat. According to this hypothesis, novelty and fear may engage distinct, separable processes in the amygdala, which has been suggested by others (Weierich et al., 2010). Alternatively, it could be that novel stimuli are more salient than repeated stimuli, and the amygdala is simply tracking this difference in salience (Sander et al., 2003). According to this idea, novelty and fear are examples of a single superordinate principle, and thus engage the same process in the amygdala. The purpose of this experiment was to test these hypotheses by examining the effects of both novelty and fear on neural activity within individual subregions of the amygdala. If these psychological properties are representations of different processes occurring in the amygdala, it is possible that they activate distinct subregions of the amygdala. If they are representations of a superordinate process occurring in the amygdala, they should activate similar subregions of the amygdala.(Contact Precision Instruments, Model SHK1, Boston, MA) through two surface cup electrodes (silver/silver chloride, 8 mm diameter, Baicalein 6-methyl ether site Biopac model EL258-RT, Goleta, CA) filled with electrolyte gel (Signa Gel, Parker laboratories Fairfield, NJ). Stimulation electrodes were placed on the skin over the subject’s right tibial nerve over the right medial malleolus. The shock was presented for 500 ms, at a level that the subject rated as painful but tolerable.UCS expectancyParticipants continuously rated their expectancy of receiving the electrical stimulation. They controlled a cursor placed on a visual analog scale anchored with 0 and 100. They were instructed to place the cursor near 0 if they were sure they would not receive an electrical stimulation, near 1.D UCS converges on the amygdala, allowing associative connections to form in amygdala synapses, and subsequent reexposure to the CS activates output cells within the central nucleus (Ledoux, 2000; Kim and Jung, 2006). Although fear learning appears to be one of the primary functions of the amygdala, there is also ample evidence to suggest the amygdala is engaged in other types of psychological phenomena.Received: 1 December 2014; Revised: 27 March 2015. Accepted: 7 MayC V The Author (2015). Published by Oxford University Press. For Permissions, please email: [email protected]|Social Cognitive and Affective Neuroscience, 2015, Vol. 10, No.In several recent articles, our lab and others have found that the amygdala responds to simple stimulus novelty (Wright et al., 2003; Blackford et al., 2010; Weierich et al., 2010; Balderston et al., 2011). For example, we compared novel and repeated images of faces and scenes. We found that novel faces, but not scenes, evoked larger responses than repeated stimuli of the same type. In addition, we found that this novelty effect was due to a response evoked by the initial presentation of a unique face; this response was not evoked on subsequent presentations (Balderston et al., 2011). This was clearly the case even for emotionally neutral faces, which is notable given the large literature suggesting that angry and fearful faces preferentially activate the amygdala (Gamer and Buchel, 2009; Whalen et al., 1998, 2001, 2004). ?One possible explanation for this novelty effect evoked by neutral faces is that the amygdala’s response to novelty represents the processing necessary to initially identify threats in the environment, while fear responses represent the actual response to an identified threat. According to this hypothesis, novelty and fear may engage distinct, separable processes in the amygdala, which has been suggested by others (Weierich et al., 2010). Alternatively, it could be that novel stimuli are more salient than repeated stimuli, and the amygdala is simply tracking this difference in salience (Sander et al., 2003). According to this idea, novelty and fear are examples of a single superordinate principle, and thus engage the same process in the amygdala. The purpose of this experiment was to test these hypotheses by examining the effects of both novelty and fear on neural activity within individual subregions of the amygdala. If these psychological properties are representations of different processes occurring in the amygdala, it is possible that they activate distinct subregions of the amygdala. If they are representations of a superordinate process occurring in the amygdala, they should activate similar subregions of the amygdala.(Contact Precision Instruments, Model SHK1, Boston, MA) through two surface cup electrodes (silver/silver chloride, 8 mm diameter, Biopac model EL258-RT, Goleta, CA) filled with electrolyte gel (Signa Gel, Parker laboratories Fairfield, NJ). Stimulation electrodes were placed on the skin over the subject’s right tibial nerve over the right medial malleolus. The shock was presented for 500 ms, at a level that the subject rated as painful but tolerable.UCS expectancyParticipants continuously rated their expectancy of receiving the electrical stimulation. They controlled a cursor placed on a visual analog scale anchored with 0 and 100. They were instructed to place the cursor near 0 if they were sure they would not receive an electrical stimulation, near 1.
