After staring at a pattern of tilted lines, subsequent lines appear to be tilted in the opposite direction (direct tilt aftereffect, TAE). In a previous fMRI study we have demonstrated a direct TAE solely induced by the mental imagination accompanied by adaptation of orientation-selective neurons located in the extrastriate cortex, supporting the assumption of a perception-like coding of mental images. In this study we enlarge and specify the evidence for a perception-like coding of orientation-imagination. First, we replicated the previously detected direct TAE induced by line imagination with altered design-variations to control possible perceptual task confounds. Second, we tried to induce two other orientation-specific aftereffects: indirect TAE and contrast-threshold elevation aftereffect by mental imagery. The results replicate a robust direct TAE by mental imagery and by visual stimulation, with no influence of attentional resource allocation or perceptual task confounds. We could not induce an indirect TAE, but observed a perception bias in the opposite direction of the indirect TAE. The mental imagery of lines induced no orientation-selective contrast-threshold elevation aftereffect. In general, mental imagery seems to influence visual perception, indicating that perceptual resources are used by mental imagery. However, the utilisation of visual resources seems to be somewhat different from utilisation by perception.

Reward processing is a central component of learning and decision making. Functional magnetic resonance imaging (fMRI) has contributed essentially to our understanding of reward processing in humans. The strength of reward-related brain responses might prove as a valuable marker for, or correlate of, individual preferences or personality traits. An essential prerequisite for this is a sufficient reliability of individual measures of reward-related brain signals. We therefore determined test-retest reliabilities of BOLD responses to reward prediction, reward receipt and reward prediction errors in the ventral striatum and the orbitofrontal cortex in 25 subjects undergoing three different simple reward paradigms (retest interval 7-13 days). Although on a group level the paradigms consistently led to significant activations of the relevant brain areas in two sessions, across-subject retest reliabilities were only poor to fair (with intraclass correlation coefficients (ICCs) of -0.15 to 0.44). ICCs for motor activations were considerably higher (ICCs 0.32 to 0.73). Our results reveal the methodological difficulties behind across-subject correlations in fMRI research on reward processing. These results demonstrate the need for studies that address methods to optimize the retest reliability of fMRI.

Everyday we choose between a variety of different food items trying to reach a decision that fits best our needs. These decisions are highly dependent on the context in which the alternatives are presented (e.g. labeling). We investigate the influence of cognition on food evaluation, using an fMRI experiment in which subjects saw and bid on different foods labeled with (or without) a widely known German emblem for organically produced food. Increased activity in the ventral striatum was found for foods labeled “organic” in comparison to conventionally labeled food. Between-subject differences in activity were related to actual everyday consumption behavior of organic food.

Previous studies have shown that prolonged inspection of a tilted visual pattern leads to changes in perception (“tilt after-effect”, TAE), as well as to a reduction of the neural activation evoked by this pattern (“neural adaptation”). In this fMRI study, we investigated whether such perceptual and neural adaptation can be induced solely by mental imagination. The subjects were asked to mentally generate tilted lines, after which they were presented test lines oriented in the same or the direction orthogonal to the mentally tilted lines. Subjects showed a TAE even after mental imagery (“mental TAE”). Furthermore, a significant orientation-specific adaptation occurred in extrastriate visual areas (V3–V4), showing a decreasing gradient of adaptation from areas V4 to V1. Both this neural adaptation and the individual size of the mental TAE correlated with performance in a behavioural task probing mental imagery. Thus, orientation-selective neurons in visual areas seem to be recruited by mental imagery, and the amount of recruitment correlates with the degree of success of mental imagery operations. The influence of mental imagery on perception and on the neural activity in extrastriate visual areas provides evidence for analogue coding of mental images.