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The lateralized readiness potential (LRP) is considered to reflect motor activation and has been used extensively as a tool in elucidating cognitive processes. In the present study, we attempted to more precisely determine the origins of the LRP within the cognitive system. The response selection and motor programming stages were selectively manipulated by varying symbolic stimulus response compatibility and the time to peak force of an isometric finger extension response. Stimulus response compatibility and time to peak force affected response latency, as measured in the electromyogram, in a strictly additive fashion. The effects of the experimental manipulations on stimulus- and response-synchronized LRPs indicate that the LRP starts after the completion of response-hand selection and at the beginning of motor programming. These results allow a more rigorous interpretation of LRP findings in basic and applied research.

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This study used event-related potentials (ERPs) and flanker-task performance to compare executive functions in adolescents with ADHD, their siblings and independent healthy controls. The aim was to investigate the processing of distracting stimuli, control over inappropriate responses, and the detection of errors in the presence of incompatible and No-go stimuli (arrow-heads and a circle, respectively). Performance showed no major differences between the groups, although No-go errors were numerically increased for the patients. Adolescents with ADHD were not characterised by the absence of post-error response slowing. The ADHD group showed a generally smaller N2 and a missing amplification of the frontal P3 (P3a) in No-go vs. incompatible trials most likely reflecting impaired inhibitory processing. In response-locked potentials error-related negativity (Ne) and positivity (Pe) did not clearly differentiate between the groups. This study shows that ADHD children are more impaired in controlled than automatic response processing and inhibition. This was particularly evident in reduced frontal activity in general and especially after No-go stimuli. Deficient error processing may, however, not be a cardinal feature of adolescents with ADHD. Future work must orient towards determining if there is a subgroup for whom the inhibitory impairment is characteristic.

Background: The event-related brain response mismatch negativity (MMN) registers changes in auditory stimulation with temporal lobe sources reflecting short-term echoic memory and frontal sources a deviance-induced switch in processing. Impairment, controversially present at the onset of schizophrenia, develops rapidly and can remain independent of clinical improvement. We examined the characteristics of the scalp-recorded MMN and related these to tests of short-term memory and set-shifting. We assessed whether the equivalent dipole sources are affected already at illness-onset in adolescence and how these features differ after a 14-year course following an adolescent onset. The strength, latency, orientation and location of frontal and temporal lobe sources of MMN activity early and late in the course of adolescent-onset schizophrenia are analysed and illustrated.

Mismatch negativity (MMN) is an event-related potential measure of auditory change detection. It is widely reported to be smaller in patients with schizophrenia and may not improve along with otherwise successful clinical treatment. The main aim of this report is to explore ways of measuring and presenting four features of frequency-deviant MMN dipole sources (dipole moment, peak latency, brain location and orientation) and to relate these to the processes of psychopathology and illness progression. Data from early onset patients (EOS) at the start of the illness in adolescence, and others who had their first break in adolescence 15 years ago (S-15Y) were compared with two groups of age-matched healthy controls (C-EOS, C-15Y). A four-source model fitted the MMN waveform recorded from all four groups, whether MMN amplitude was more (EOS) or less (S-15Y) reduced. The locations were in the left superior temporal and anterior cingulate gyri, right superior temporal and inferior/mid frontal cortices. Dipole latencies confirmed a bottom-up sequence of processing and dipole moments were larger in the temporal lobes and on the left. Patients showed small dipole location changes that were more marked in the S-15Y than the EOS group (more rostral for the left anterior cingulate, more caudal for the right mid-frontal dipole) consistent with illness progression. The modelling of MMN dipole sources on brain atlas and anatomical images suggests that there is a degree of dissociation during illness between small progressive anatomical changes and some functional recovery indexed by scalp recordings from patients with an onset in adolescence 15 years before compared to adolescents in their first episode.

Ulrich, suggested that movement preparation at the level of the motor cortex, as indexed by the lateralized readiness potential (LRP), proceeds in a strongly hierarchical fashion, where parameters other than response hand are prepared only if all the movement parameters are known. These conclusions were based on an experiment where a precue provided information about response hand, direction of finger movement, and movement force. To assess the generality of these findings, we replaced the force parameter with response finger. LRP indicated that preparation of the required finger is possible even when preliminary information is incomplete. Therefore, movement preparation appears to follow different rules when anatomical relationships (hand and finger) are concerned as compared to functional parameters like movement direction. On the other hand, at a limb-unspecific level, as indicated by the contingent negative variation, we confirmed evidence for parallel programming of all movement parameters.Descriptors: Lateralized readiness potential, Contingent negative variation, Movement preparation, Precuing Even very simple movements involve different dimensions and, therefore, require the specification of values along these dimensions. For example, flexing a finger requires the specification of the finger, the movement direction, its force, and velocity. According to the theory of generalized motor programs (Schmidt, 1975), values on movement dimensions are conceived as parameters of abstract motor programs. The assembly of concrete motor commands requires the selection of the motor program as well as the specification of all its parameters. A crucial question for theories about movement preparation is the organization of parameter specification. In principle, all necessary parameters might be specified independently and in parallel. Alternatively, specification of the various movement parameters might proceed in a predetermined, strictly hierarchical order (cf. Rosenbaum, 1980). In the present experiments, the structure of parameter specification is analyzed by means of recording event-related brain potentials (ERPs). Important headway in investigating the organization of movement preparation has been made by using the precuing technique developed by Rosenbaum (1980Rosenbaum ( , 1983. Here, a number of possible responses differ with respect to parameter values, for example, an upward or downward movement with the right or left index finger. A precue prior to the response signal may provide none, some, or all of the defining parameters of the response, allowing for different degrees of advance movement preparation. Finally, a response signal is presented that specifies the required response. In many experiments, it has been shown that reaction time (RT) to the response signal decreases with the number of parameters provided by the precue. This so-called precuing effect is considered to be informative about questions like the order of movement parameter selection, whether the selection of response parameters occurs ser...

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