196 research outputs found
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Differential brain activity during emotional versus nonemotional reversal learning
The ability to change an established stimulus–behavior association based on feedback is critical for adaptive social behaviors. This ability has been examined in reversal learning tasks, where participants first learn a stimulus–response association (e.g., select a particular object to get a reward) and then need to alter their response when reinforcement contingencies change. Although substantial evidence demonstrates that the OFC is a critical region for reversal learning, previous studies have not distinguished reversal learning for emotional associations from neutral associations. The current study examined whether OFC plays similar roles in emotional versus neutral reversal learning. The OFC showed greater activity during reversals of stimulus–outcome associations for negative outcomes than for neutral outcomes. Similar OFC activity was also observed during reversals involving positive outcomes. Furthermore, OFC activity is more inversely correlated with amygdala activity during negative reversals than during neutral reversals. Overall, our results indicate that the OFC is more activated by emotional than neutral reversal learning and that OFC's interactions with the amygdala are greater for negative than neutral reversal learning
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Age-related similarities and differences in brain activity underlying reversal learning
The ability to update associative memory is an important aspect of episodic memory and a critical skill for social adaptation. Previous research with younger adults suggests that emotional arousal alters brain mechanisms underlying memory updating; however, it is unclear whether this applies to older adults. Given that the ability to update associative information declines with age, it is important to understand how emotion modulates the brain processes underlying memory updating in older adults. The current study investigated this question using reversal learning tasks, where younger and older participants (age ranges 19-35 and 61-78 respectively) learn a stimulus–outcome association and then update their response when contingencies change. We found that younger and older adults showed similar patterns of activation in the frontopolar OFC and the amygdala during emotional reversal learning. In contrast, when reversal learning did not involve emotion, older adults showed greater parietal cortex activity than did younger adults. Thus, younger and older adults show more similarities in brain activity during memory updating involving emotional stimuli than during memory updating not involving emotional stimuli
The diverse magneto-optical selection rules in bilayer black phosphorus
The magneto-optical properties of bilayer phosphorene is investigated by the
generalized tight-binding model and the gradient approximation. The vertical
inter-Landau-level transitions, being sensitive to the polarization directions,
are mainly determined by the spatial symmetries of sub-envelope functions on
the distinct sublattices. The anisotropic excitations strongly depend on the
electric and magnetic fields. A perpendicular uniform electric field could
greatly diversify the selection rule, frequency, intensity, number and form of
symmetric absorption peaks. Specifically, the unusual magneto-optical
properties appear beyond the critical field as a result of two subgroups of
Landau levels with the main and side modes. The rich and unique
magneto-absorption spectra arise from the very close relations among the
geometric structures, multiple intralayer and interlayer hopping integrals, and
composite external fields
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