Research on emotion showed an increase, with age, in prevalence of positive information relative to negative ones. This effect is called positivity effect. From the cerebral analysis of the Late Positive Potential (LPP), sensitive to attention, our study investigated to which extent the arousal level of negative scenes is differently processed between young and older adults and, to which extent the arousal level of negative scenes, depending on its value, may contextually modulate the cerebral processing of positive (and neutral) scenes and favor the observation of a positivity effect with age. With this aim, two negative scene groups characterized by two distinct arousal levels (high and low) were displayed into two separate experimental blocks in which were included positive and neutral pictures. The two blocks only differed by their negative pictures across participants, as to create two negative global contexts for the processing of the positive and neutral pictures. The results show that the relative processing of different arousal levels of negative stimuli, reflected by LPP, appears similar between the two age groups. However, a lower activity for negative stimuli is observed with the older group for both tested arousal levels. The processing of positive information seems to be preserved with age and is also not contextually impacted by negative stimuli in both younger and older adults. For neutral stimuli, a significantly reduced activity is observed for older adults in the contextual block of low-arousal negative stimuli. Globally, our study reveals that the positivity effect is mainly due to a modulation, with age, in processing of negative stimuli, regardless of their arousal level. It also suggests that processing of neutral stimuli may be modulated with age, depending on negative context in which they are presented to. These age-related effects could contribute to justify the differences in emotional preference with age.

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The electrical characteristics and the low frequency noise of TiN x Schottky contacts on n-type Si(100) have been systematically measured. The TiN x thin films were deposited by reactive magnetron sputtering at room temperature. Based on a model of a parallel combination of an ideal diode of current I 1 and a generation-recombination diode of current I 2 , we have extracted the contribution of both diodes to the measured total current I . Treating the two components I 1 and I 2 as different noise generators, we have analysed the observed white noise at high frequencies and the 1/f excess current noise at lower frequencies. The white noise is explained by using a pure shot noise for the component I 1 , by applying Gupta's general theorem on noise in non-linear driven devices for the component I 2 and by considering an additional noise generator with a Nyquist-type intensity. The 1/f excess current noise S I is explained by a model based on fluctuations of the generation-recombination current I 2 only. Analysis of the S I versus I data allowed us to determine the interface state density.