Eliciting contextual temporal calibration: The effect of bottom-up and top-down information in reproduction tasks.

Bayesian integration assumes that a current observation is integrated with previous observations. An example in the temporal domain is the central tendency effect: when a range of durations is presented, a regression towards the mean is observed. Furthermore, a context effect emerges if a partially overlapping lower and a higher range of durations is presented in a blocked design, with the overlapping durations pulled towards the mean duration of the block. We determine under which conditions this context effect is observed, and whether explicit cues strengthen the effect. Each block contained either two or three durations, with one duration present in both blocks. We provided either no information at the start of each block about the nature of that block, provided written ("short" / "long" or "A" / "B") categorizations, or operationalized pitch (low vs high) to reflect the temporal context. We demonstrate that (1) the context effect emerges as long as sufficiently distinct durations are presented; (2) the effect is not modulated by explicit instructions or other cues; (3) just a single additional duration is sufficient to produce a context effect. Taken together, these results provide information on the most efficient operationalization to evoke the context effect, allowing for highly economical experimental designs, and highlights the automaticity by which priors are constructed.

Dynamic range adaptation to spectral stimulus statistics in human auditory cortex.

Classically, neural adaptation refers to a reduction in response magnitude by sustained stimulation. In human electroencephalography (EEG), neural adaptation has been measured, for example, as frequency-specific response decrease by previous stimulation. Only recently and mainly based on animal studies, it has been suggested that statistical properties in the stimulation lead to adjustments of neural sensitivity and affect neural response adaptation. However, it is thus far unresolved which statistical parameters in the acoustic stimulation spectrum affect frequency-specific neural adaptation, and on which time scales the effects take place. The present human EEG study investigated the potential influence of the overall spectral range as well as the spectral spacing of the acoustic stimulation spectrum on frequency-specific neural adaptation. Tones randomly varying in frequency were presented passively and computational modeling of frequency-specific neural adaptation was used. Frequency-specific adaptation was observed for all presentation conditions. Critically, however, the spread of adaptation (i.e., degree of coadaptation) in tonotopically organized regions of auditory cortex changed with the spectral range of the acoustic stimulation. In contrast, spectral spacing did not affect the spread of frequency-specific adaptation. Therefore, changes in neural sensitivity in auditory cortex are directly coupled to the overall spectral range of the acoustic stimulation, which suggests that neural adjustments to spectral stimulus statistics occur over a time scale of multiple seconds.

Serum vaspin concentrations are decreased after exercise-induced oxidative stress.

Elevated visceral adipose tissue-derived serpin (vaspin) serum concentrations are associated with impaired insulin sensitivity, but increase unexpectedly after long-term physical training. We therefore investigated the effect of an acute exercise bout and the effects of vitamin supplementation on chronic exercise effect and on serum vaspin concentrations. We measured serum vaspin and thiobarbituric acid-reactive substances (TBARS) concentrations in 80 individuals before and after a 1-hour acute exercise bout and independently in 40 healthy young men who were randomly assigned to either antioxidant (vitamin C (1,000 mg/day) and vitamin E (400 IU/day)) or to no supplementation after a standardized 4-week physical training program as a post hoc analysis. Serum vaspin concentrations significantly decreased after acute physical exercise as well as after 4 weeks of training in individuals without antioxidants. Changes in vaspin serum concentration correlate with increased TBARS serum concentrations both in response to a 1-hour exercise bout (r = -0.42, p < 0.01) and to the 4-week training (r = -0.31, p < 0.05). Interestingly, supplementation with antioxidants rather increased circulating vaspin levels in response to 4 weeks of exercise. In conclusion, vaspin serum concentrations are decreased by exercise-induced oxidative stress, but not by exercise-associated improvement in insulin sensitivity.