Dopaminergic medication alters auditory distractor processing in Parkinson's disease

Parkinson's disease (PD) patients show signs of cognitive impairment, such as executive dysfunction, working memory problems and attentional disturbances, even in the early stages of the disease. Though motor symptoms of the disease are often successfully addressed by dopaminergic medication, it still remains unclear, how dopaminergic therapy affects cognitive function. The main objective of this study was to assess the effect of dopaminergic medication on visual and auditory attentional processing. 14 PD patients and 13 matched healthy controls performed a three-stimulus auditory and visual oddball task while their EEG was recorded. The patients performed the task twice, once on- and once off-medication. While the results showed no significant differences between PD patients and controls, they did reveal a significant increase in P3 amplitude on- vs. off-medication specific to processing of auditory distractors and no other stimuli. These results indicate significant effect of dopaminergic therapy on processing of distracting auditory stimuli. With a lack of between group differences the effect could reflect either 1) improved recruitment of attentional resources to auditory distractors; 2) reduced ability for cognitive inhibition of auditory distractors; 3) increased response to distractor stimuli resulting in impaired cognitive performance; or 4) hindered ability to discriminate between auditory distractors and targets. Further studies are needed to differentiate between these possibilities.     

The effect of alcohol administration on human timing: a comparison of prospective timing, retrospective timing and passage of time judgements

Previous research suggests that human timing may be affected by alcohol administration. The current study aimed to expand on previous research by examining the effect of alcohol on prospective timing, retrospective timing and passage of time judgements. A blind between-subjects design was employed in which participants were either administered 0 g of alcohol per kilogramme of body weight (placebo), 0.4 g/kg (low dose) or 0.6 g/kg (high dose). Participants completed four types of temporal task; verbal estimation and temporal generalisation, a retrospective timing task and a passage of time judgement task. A high dose of alcohol resulted in overestimations of duration relative to the low dose and placebo group in the verbal estimation task. A high dose of alcohol was also associated with time passing more quickly than normal. Alcohol had no effect on retrospective judgements. The results suggest that a high dose of alcohol increases internal clock speed leading to over-estimations of duration on prospective timing tasks, and the sensation of time passing more quickly than normal. The absence of an effect of alcohol on retrospective timing supports the suggestion that retrospective judgements are not based on the output of an internal clock.     

The role of the noradrenergic system in emotional memory

This contribution is an overview on the role of noradrenaline as neurotransmitter and stress hormone in emotional memory processing. The role of stress hormones in memory formation of healthy subjects can bear significance for the derailment of memory processes, for example, in post traumatic stress disorder (PTSD). Increased noradrenaline levels lead to better memory performance, whereas blocking the noradrenergic receptors with a betablocker attenuates this enhanced memory for emotional information. Noradrenaline appears to interact with cortisol in emotional memory processes, varying from encoding to consolidation and retrieval. Imaging studies show that confronting human subjects with emotional stimuli results in increased amygdala activation and that this activation is noradrenergic dependent. The role of noradrenaline in other brain areas, such as hippocampus and prefrontal cortex, is shortly summarized. Finally, the pros and cons of a therapeutic application of betablockers in the (secondary) prevention of PTSD will be discussed.