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The aim of the investigations was to explore the nature and the severity of cognitive deficits in narcolepsy patients. In two studies, narcolepsy patients were compared with matched control subjects on a range of attention, memory and executive control tasks. Impairments were only observed on attention and executive function tasks which involved higher demands on inhibition or task management abilities whereas relatively routine memory and attention tasks yielded intact performance in narcolepsy patients. The overall pattern of results indicates an executive control deficit in narcolepsy which might be related to a reduction of available cognitive processing resources because of the need for continuous allocation of resources to monitoring and maintenance of vigilance. [ABSTRACT FROM AUTHOR]

Background: Excessive alcohol consumption has been linked to structural and functional brain changes associated with cognitive, emotional, and behavioral impairments. It has been suggested that neural processing in the reward system is also affected by alcoholism. The present study aimed at further investigating reward-based associative learning and reversal learning in detoxified alcohol-dependent patients., Methods: Twenty-one detoxified alcohol-dependent patients and 26 healthy control subjects participated in a probabilistic learning task using monetary and alcohol-associated rewards as feedback stimuli indicating correct responses. Performance during acquisition and reversal learning in the different feedback conditions was analyzed., Results: Alcohol-dependent patients and healthy control subjects showed an increase in learning performance over learning blocks during acquisition, with learning performance being significantly lower in alcohol-dependent patients. After changing the contingencies, alcohol-dependent patients exhibited impaired reversal learning and showed, in contrast to healthy controls, different learning curves for different types of rewards with no increase in performance for high monetary and alcohol-associated feedback., Conclusions: The present findings provide evidence that dysfunctional processing in the reward system in alcohol-dependent patients leads to alterations in reward-based learning resulting in a generally reduced performance. In addition, the results suggest that alcohol-dependent patients are, in particular, more impaired in changing an established behavior originally reinforced by high rewards., (Copyright © 2014 by the Research Society on Alcoholism.)

Both execution and observation of erroneous actions have been shown to increase the activity of the anterior cingulate cortex (ACC) as reflected in characteristic event-related potential (ERP) components labelled error-related negativity (ERN) and observer error-related negativity (oERN), respectively. Whereas these labels implicate a modulation of both components by response accuracy, recent findings suggest a more general involvement of the ACC in the detection of unexpected events. In previous studies, a lower frequency of erroneous as compared with correct observed actions resulted in lower expectation of erroneous actions. The present study investigates whether ERPs following observed actions are modulated by response accuracy or violation of expectation. Sixteen human subjects observed a virtual person whose actions in a game were expected or unexpected. Action expectation was independent of accuracy. In both conditions, subjects observed correct and incorrect actions equally often. Whereas ERPs were not modulated by accuracy, we found an enhanced amplitude of a negative frontocentral ERP component in the time window of the oERN for unexpected as compared with expected observed actions, which we suggest reflects an action prediction error. These results propose that the function of the ACC in performance monitoring depends less on accuracy of actions but rather on predictions and their violations. Future research will have to clarify whether the present ERP modulations revealed a feature of the oERN or whether they represent a distinct component., (© 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)

The updating of visual space across saccades is thought to rely on efference copies of motor commands. In humans, thalamic lesions impair performance on a saccadic double-step task, which requires the use of efference copy information, and the altering of saccade-related efference copy processing. This deficit is attributed to disruption of a pathway from the superior colliculus to the frontal eye field. However, the cerebellum is probably also involved in efference copy processing, due to its pivotal role for predictive motor control. The present study investigated the processing of efference copy information in eight patients with focal cerebellar lesions and 22 healthy controls by means of a saccadic double-step task with simultaneous event-related potential recording. Despite intact behavioural performance, a positive event-related potential component between 150 and 450 ms after first saccade onset in the updating condition, which has been interpreted in terms of the integration of efference copy signals with motor intentions for a subsequent saccade, was markedly reduced in the patients. These findings suggest that the cerebellum contributes to on-line saccade monitoring, and that cerebellar lesions alter saccade-related efference copy processing. However, given the intact behavioural performance, the reduced positivity in the patients may indicate that cerebellar damage is accounted for by either exploiting reduced saccade-related information, or making use of compensatory strategies to circumvent a deficit in using efference copy information procured by the cerebellum. The present study extends previous findings on the neural underpinnings of saccadic updating and further elucidates the mechanisms underlying cerebellar predictive motor control., (© 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.)

Background: Chronic and excessive consumption of alcohol is associated with structural, physiological, and functional changes in multiple regions of the human brain including the prefrontal cortex, the medial temporal lobe, and the structures of the reward system. The present study aimed to assess the ability of alcohol-dependent patients (ADP) to learn probabilistic stimulus-reward contingencies and to transfer the acquired knowledge to new contexts. During transfer, the relative preference to learn from positive or negative feedback was also assessed., Methods: Twenty-four recently detoxified ADP and 20 healthy controls engaged in a feedback learning task with monetary rewards. The learning performance per se and transfer performance including positive versus negative learning were examined, as well as the relationship between different learning variables and variables comprising alcohol and nicotine consumption patterns, depression, and personality traits (harm avoidance and impulsivity)., Results: Patients did not show a significant general learning deficit in the acquisition of stimulus-response-outcome associations. Fifteen healthy subjects and 13 patients reached the transfer phase, in which ADP showed generally lower performance than healthy controls. There was no specific deficit with regard to learning from positive or negative feedback. The only near-significant (negative) correlation between learning variables and drug consumption patterns, depression, and personality traits emerged for harm avoidance and positive learning in controls., Conclusions: Impaired transfer performance suggests that ADP had problems applying their acquired knowledge in a new context. Potential relations to dysfunctions of specific brain structures and implications of the finding for therapy are discussed., (Copyright © 2012 by the Research Society on Alcoholism.)

The dissociability of novelty detection in relational (RM) and non-relational memory (NRM) is currently under debate. To further address the time courses and underlying brain correlates of novelty detection, event-related potentials (ERPs) were analysed for encoding and retrieval on three memory tasks in healthy subjects. Spatial and non-spatial RM as well as NRM were assessed separately. The ERPs related to RM and NRM were dissociable for hits and correct rejections in an early and late time window. An early old/new effect was observed for NRM. A late old/new effect replicated the frequently reported recollection-associated old/new effect in terms of direction and amplitudes. Four different novelty types (spatial relational, non-spatial relational, horizontal non-relational and inverted non-relational) were examined. The P3a related to novelty detection differed in horizontal vs. inverted distractors in NRM, but not in spatial vs. non-spatial RM. ERPs for repetition detection (hits during retrieval) and also for subsequent hits (encoding phase) differed between RM and NRM. These findings are discussed in relation to potential brain correlates in RM and NRM during encoding and retrieval.

The feedback-related negativity (FRN) has been hypothesized to be linked to reward-based learning. While many studies have shown that the FRN only occurs in response to unexpected negative outcomes, the relationship between the magnitude of negative prediction errors and FRN amplitude remains a matter of debate. The present study aimed to elucidate this relationship with a new behavioural procedure that allowed subjects to predict precise reward probabilities by learning an explicit rule. Insight into the rule did not only influence subjects' choice behaviour, but also outcome-related event-related potentials. After subjects had learned the rule, the FRN amplitude difference between non-reward and reward mirrored the magnitude of the negative prediction error, i.e. it was larger for less likely negative outcomes. Source analysis linked this effect to the anterior cingulate cortex. P300 amplitude was also modulated by outcome valence and expectancy. It was larger for positive and unexpected outcomes. It remains to be clarified, however, whether the P300 reflects a positive prediction error.

Accumulating evidence suggests that thalamic nuclei relay corollary discharge information of saccadic eye movements, enabling the visual system to update the representation of visual space. The present study aimed to explore the effect of thalamic lesions in humans on updating-related cortical processing. Event-related potentials were recorded while four patients with impairments in using corollary discharge information and 12 healthy control subjects performed a saccadic double-step task. In the experimental condition, which required the use of corollary discharge information, control subjects showed a pronounced positivity over the parietal cortex starting about 150 ms after first saccade onset, reflecting the updating process. In the patients, parietal processing related to updating was altered. Three patients showed evidence of reduced updating event-related potential effects, consistent with a unilateral deficit in using corollary discharge information. In two patients, the event-related potential topography differed significantly from the topography pattern observed in controls. Thalamic damage affects updating-related processing, presumably due to insufficient transfer of saccade-related information to parietal areas. This study thus provides further evidence for thalamic involvement in relaying corollary discharge information related to saccadic eye movements. Our data suggest that integration of corollary discharge and motor information occurs directly before the second saccade in a double-step task.