The ability to link variables is critical to many high-order cognitive functions, including reasoning. It has been proposed that limits in relating variables depend critically on relational complexity, defined formally as the number of variables to be related in solving a problem. In humans, the prefrontal cortex is known to be important for reasoning, but recent studies have suggested that such processes are likely to involve widespread functional brain networks. To test this hypothesis, we used functional magnetic resonance imaging and a classic measure of deductive reasoning to examine changes in brain networks as a function of relational complexity. As expected, behavioral performance declined as the number of variables to be related increased. Likewise, increments in relational complexity were associated with proportional enhancements in brain activity and task-based connectivity within and between 2 cognitive control networks: A cingulo-opercular network for maintaining task set, and a fronto-parietal network for implementing trial-by-trial control. Changes in effective connectivity as a function of increased relational complexity suggested a key role for the left dorsolateral prefrontal cortex in integrating and implementing task set in a trial-by-trial manner. Our findings show that limits in relational processing are manifested in the brain as complexity-dependent modulations of large-scale networks.

Many clinical strategies use patients' imagery to explore and treat phobic and posttrauma reactions, however little attention has been paid to the underlying assumption that imagery of relevant stimuli may help maintain conditioned behavior. In this article, the authors examine the premise that mental images can potentiate and substitute for physical stimuli in human classical conditioning. The authors review empirical evidence to detail the role of images of conditioned stimuli (CS) and unconditioned stimuli (US) during pre-exposure to stimuli, the actual pairing of the CS and US, and extinction when the CS is presented alone. The evidence suggests that mental imagery can facilitate or diminish the outcome of classical conditioning in humans and, more tentatively, that mental images can substitute for actual US and CS in autonomic conditioning. They argue that researchers should explore the role of mental imagery in conditioning through the use of advances in the measurement of imagery. Finally, they analyze anxiety and trauma reactions as examples of how applied areas can be used to explore and benefit from developments in this area.

This study investigated the effect of traumatic brain injury (TBI) on time-, event-, and activity-based prospective memory using a laboratory paradigm developed in the literature on ageing (Einstein, McDaniel, Richardson, Guynn, & Cunfer, 1995). The participants were 12 individuals with severe long-term TBI and 12 community controls. Participants were asked to answer general-knowledge questions on a computer for two sessions. The time- and event-based tasks were embedded in this filler activity. Participants were also required to carry out activity-based actions at the end of the two sessions. Participants with TBI performed significantly worse than did controls on all three prospective-memory tasks, indicating that TBI affects not only retrospective but also prospective memory. Implications of these results for the assessment and rehabilitation of memory problems in individuals with TBI are discussed.

Despite the likely importance of Pavlovian conditioning in sexual behavior, previous evidence of reliable or sizeable effects is very sparse. This report includes four experiments in the conditioning of sexual arousal in the males of a mammalian species, namely, the rat. In each case the unconditioned response (UR) was unconsummated arousal after exposure to a female. There was evidence of a substantial conditioned effect, as shown by decreases in the time to complete copulation during postconditioning conditioned stimulus (CS) tests. It is also possible to establish a second-order conditioned response (CR), which retains its strength even after extinction of the first-order response. These results confirm the power of Pavlovian contingencies in sexual responding and provide implications for conditioning theory and applied work.

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