No abstract

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.

Cognitive impairment was studied in distinct types of spinocerebellar ataxia (SCA): eleven SCA1, 14 SCA2, and 11 SCA3 individuals and 8 age- and IQ- matched controls. All were submitted to a neuropsychological test battery that comprised tests for IQ, attention, executive function, verbal and visuospatial memory. Executive dysfunction was prominent in SCA1 as compared with controls and all other SCA types. Mild deficits of verbal memory were present in SCA1, SCA2 and SCA3. The neuropathological pattern in different SCA types suggests that these cognitive deficits are not likely to be contingent upon cerebellar degeneration but to result from disruption of a cerebrocerebellar circuitry presumably at the pontine level.

We explored classical conditioning in human subjects who had lesions in their cerebellar circuitry. Seven patients with damage to cerebellar structures and matched control subjects underwent simple delay tone-airpuff conditioning. Eyelid conditioned response (CR) acquisition was severely disrupted in the patient group, whereas autonomic CRs and slow cortical potentials developing between conditioned stimulus (CS) and the unconditioned stimulus (UCS) were unaffected. Results are consistent with animal studies and earlier case reports indicating that intact cerebellar structures are necessary for the acquisition of classically conditioned motor responses.

The cerebellum has long been considered to be mainly involved in motor function. In the last 20 years, evidence from neuroimaging studies and from investigations of patients with cerebellar lesions has shown that the cerebellum plays a role in a range of cognitive functions. While cerebellar contributions have been shown for learning and memory, the cerebellum has also been linked to higher order cognitive control processes frequently referred to as executive functions. Although it is widely accepted that the cerebellum contributes to cognitive processing, the nature of cerebellar involvement is not well understood. The present paper focuses on the role of the cerebellum in executive processing, reviewing findings derived from neuroimaging studies or from studies investigating deficits related to cerebellar dysfunction. As executive functions cannot be considered as a unitary concept, special emphasis is put on cerebellar contributions to different aspects of executive control such as working memory, multitasking or inhibition. Referring to models derived from motor control, possible mechanisms of cerebellar involvement in executive processing are discussed. Finally, methodological problems in assessing executive deficits in general and in assessing the cerebellar contribution to executive processing in particular are addressed.

No abstract

Accumulating evidence from both human lesion and functional neuroimaging studies appears to support the hypothesis that the cerebellum contributes to non-motor functions. Along similar lines, cognitive, affective and behavioural changes in psychiatric disorders, such as autism, schizophrenia and dyslexia, have been linked to structural cerebellar abnormalities. The aim of this special issue was to evaluate the current knowledge base after more than 20 years of controversial discussion. The contributions of the special issue cover the most important cognitive domains, i.e., attention, memory and learning, executive control, language and visuospatial function. The available empirical evidence suggests that cognitive changes in patients with cerebellar dysfunction are mild and clearly less severe than the impairments observed after lesions to neocortical areas to which the cerebellum is closely connected via different cerebro-cerebellar loops. Frequently cited early findings, e.g., with respect to a specific cerebellar involvement in attention, have not been replicated or might be confounded by motor or working memory demands of the respective attention task. On the other hand, there is now convincing evidence for a cerebellar involvement in the mediation of a range of cognitive domains, most notably verbal working memory. Verbal working memory problems may partly underlie the compromised performance of cerebellar lesion patients on at least some complex cognitive tasks. Although investigations have moved from anecdotical case reports to hypothesis-driven controlled clinical group studies based on sound methods which are complemented by state-of-the-art functional neuroimaging studies, the empirical evidence available so far does not yet allow a convincing theory of the mechanisms of a cerebellar involvement in cognitive function. Future studies are clearly needed to further elucidate the nature of the processes linked to cerebellar mediation of cognitive processes and their possible link to motor theories of cerebellar function, e.g., its role in prediction and/or timing.

The present study aimed to further explore the mechanisms underlying the perception of human body shapes. Behavioral and electrophysiological inversion effects were studied for human bodies with and without heads and for animal bodies (cats, dogs, and birds). Recognition of human bodies (with heads) was adversely affected by stimulus inversion, and the N170 had longer latencies and higher amplitudes for inverted compared to upright human bodies. Human body shapes presented without heads yielded the opposite result pattern. The data for animal bodies did not yield consistent effects. Taken together, the present findings suggest that human bodies might be processed by specialized cortical mechanisms which are at least partly dissociable from mechanisms involved in object or face processing.