Neural correlates of cognitive dissonance and choice-induced preference change

According to many modern economic theories, actions simply reflect an individual's preferences, whereas a psychological phenomenon called “cognitive dissonance” claims that actions can also create preference. Cognitive dissonance theory states that after making a difficult choice between two equally preferred items, the act of rejecting a favorite item induces an uncomfortable feeling (cognitive dissonance), which in turn motivates individuals to change their preferences to match their prior decision (i.e., reducing preference for rejected items). Recently, however, Chen and Risen [Chen K, Risen J (2010) J Pers Soc Psychol 99:573–594] pointed out a serious methodological problem, which casts a doubt on the very existence of this choice-induced preference change as studied over the past 50 y. Here, using a proper control condition and two measures of preferences (self-report and brain activity), we found that the mere act of making a choice can change self-report preference as well as its neural representation (i.e., striatum activity), thus providing strong evidence for choice-induced preference change. Furthermore, our data indicate that the anterior cingulate cortex and dorsolateral prefrontal cortex tracked the degree of cognitive dissonance on a trial-by-trial basis. Our findings provide important insights into the neural basis of how actions can alter an individual's preferences

Economic choices can be made using only stimulus values

Decision-making often involves choices between different stimuli, each of which is associated with a different physical action. A growing consensus suggests that the brain makes such decisions by assigning a value to each available option and then comparing them to make a choice. An open question in decision neuroscience is whether the brain computes these choices by comparing the values of stimuli directly in goods space or instead by first assigning values to the associated actions and then making a choice over actions. We used a functional MRI paradigm in which human subjects made choices between different stimuli with and without knowledge of the actions required to obtain the different stimuli. We found neural correlates of the value of the chosen stimulus (a postdecision signal) in ventromedial prefrontal cortex before the actual stimulus–action pairing was revealed. These findings provide support for the hypothesis that the brain is capable of making choices in the space of goods without first transferring values into action space

Hyperarousal symptoms after traumatic and nontraumatic births

Background: Measurement is critical in postnatal posttraumatic stress disorder (PTSD) because symptoms may be influenced by normal postnatal phenomena such as physiological changes and fatigue. Objective: This study examined: (1) whether hyperarousal symptoms differ between women who have traumatic or nontraumatic births; (2) whether the construct of hyperarousal is coherent in postnatal women; and (3) whether hyperarousal symptoms are useful for identifying women who have traumatic births or PTSD. Methods: A survey of PTSD symptoms in 1,078 women recruited via the community or Internet who completed an online or paper questionnaire measuring childbirth-related PTSD symptoms between 1 and 36 months after birth. Women who had a traumatic birth as defined by DSM-IV criterion A (n = 458) were compared with women who did not have a traumatic birth (n = 591). Results: A one-factor dimension of hyperarousal was identified that included all five hyperarousal items. Diagnostic criteria of two or more hyperarousal symptoms in the previous week were reported by 75.3% of women with traumatic birth and 50.5% of women with nontraumatic births. The difference in mean hyperarousal symptoms between groups was substantial at 0.76 of a standard deviation (Hedge’s g, CI = 0.64, 0.89). A larger difference was observed between women with and without diagnostic PTSD (g = 1.64, CI 1.46, 1.81). However, receiver operating characteristic analyses showed hyperarousal symptoms have poor specificity and alternative ways of calculating symptoms did not improve this. Comparison with other PTSD symptoms found re-experiencing symptoms were most accurate at identifying women with traumatic births. Conclusions: Results suggest hyperarousal symptoms are associated with traumatic birth and are a coherent construct in postnatal women. However, they have poor specificity and should only be used as part of diagnostic criteria, not as a sole indicator

Tree diversity, forest structure and species composition in a logged-over mixed dipterocarp forest, Bintulu, Sarawak, Malaysia

The Anap Muput Forest Management Unit (AMFMU) located in Bintulu, Sarawak, Malaysia is a production forest. It have undergone at least one or two cycle of selective logging where valuable timber species are depleting. Therefore the structure, composition and productivity of the re growth forests are quite different from the virgin stands. Measuring the diversity is one of the ways to access the soundness of ecological information on tree diversity, forest structure and species composition. A total of 61 circular plots of 25-m radius were established covering a total area of 7.67 hectares. Trees with diameter at breast height (DBH) of 10 cm and above were recorded. Species composition, diversity, relative density (RD), relative basal area (RBA) and relative frequency (RF) and important value index (IVI) were calculated. A total of 5,871 trees comprised of 66 families, 208 genera and 827 species were recorded. Dipterocarpaceae was the most dominant family with 31.8% of trees. Shorea was the dominant genus, while Macaranga hosei of Euphorbiaceae with 193 trees is the most dominant species here. Shorea collaris was the highest record for Dipterocarpaceae with 176 stands. The highest IVI of trees in lowland dipterocarp forest was Shorea macroptera ssp. baillonii with the value of 84.73 though it only represented 1.8% of the total IVI of the area. At ShannonWeiner diversity index (H’) of 3.44, the diversity of logged-over lowland dipterocarp forest in the study area is considered highly diverse. The results of this study strengthen the importance to manage the forest sustainably as timber industry is important for the state’s economy

Neural computations underlying action-based decision making in the human brain

Action-based decision making involves choices between different physical actions to obtain rewards. To make such decisions the brain needs to assign a value to each action and then compare them to make a choice. Using fMRI in human subjects, we found evidence for action-value signals in supplementary motor cortex. Separate brain regions, most prominently ventromedial prefrontal cortex, were involved in encoding the expected value of the action that was ultimately taken. These findings differentiate two main forms of value signals in the human brain: those relating to the value of each available action, likely reflecting signals that are a precursor of choice, and those corresponding to the expected value of the action that is subsequently chosen, and therefore reflecting the consequence of the decision process. Furthermore, we also found signals in the dorsomedial frontal cortex that resemble the output of a decision comparator, which implicates this region in the computation of the decision itself

Breakdown of supersaturation barrier links protein folding to amyloid formation

The thermodynamic hypothesis of protein folding, known as the “Anfinsen’s dogma” states that the native structure of a protein represents a free energy minimum determined by the amino acid sequence. However, inconsistent with the Anfinsen’s dogma, globular proteins can misfold to form amyloid fibrils, which are ordered aggregates associated with diseases such as Alzheimer’s and Parkinson’s diseases. Here, we present a general concept for the link between folding and misfolding. We tested the accessibility of the amyloid state for various proteins upon heating and agitation. Many of them showed Anfinsen-like reversible unfolding upon heating, but formed amyloid fibrils upon agitation at high temperatures. We show that folding and amyloid formation are separated by the supersaturation barrier of a protein. Its breakdown is required to shift the protein to the amyloid pathway. Thus, the breakdown of supersaturation links the Anfinsen’s intramolecular folding universe and the intermolecular misfolding universe

Fission yeast 26S proteasome mutants are multi-drug resistant due to stabilization of the pap1 transcription factor

Here we report the result of a genetic screen for mutants resistant to the microtubule poison methyl benzimidazol-2-yl carbamate (MBC) that were also temperature sensitive for growth. In total the isolated mutants were distributed in ten complementation groups. Cloning experiments revealed that most of the mutants were in essential genes encoding various 26S proteasome subunits. We found that the proteasome mutants are multi-drug resistant due to stabilization of the stress-activated transcription factor Pap1. We show that the ubiquitylation and ultimately the degradation of Pap1 depend on the Rhp6/Ubc2 E2 ubiquitin conjugating enzyme and the Ubr1 E3 ubiquitin-protein ligase. Accordingly, mutants lacking Rhp6 or Ubr1 display drug-resistant phenotypes