Striatal dopamine and learning strategy-an (123)I-FP-CIT SPECT study

Patients with Parkinson's disease (PD) have difficulty in processing learning tasks that lack external guidelines and, consequently, necessitate the subjects to generate their own problem-solving strategy. While the contribution of striatal dopaminergic deficiency to PD-specific motor symptoms is well established, its role in the PD-characteristic deviant learning style remains unclear. The aim of this study was to assess the relation between striatal dopamine activity as revealed by single photon emission computed tomography (SPECT) with (123)I-FP-CIT, a ligand for the dopamine transporter (DaT), and type of learning strategy, as identified by the California Verbal Learning Task (CVLT) in 19 patients with probable PD. The results showed a robust inverse correlation between striatal dopamine DaT binding and the externally guided, serial learning strategy: the lower the DaT in caudate nucleus as well as in putamen, the more the patient group appeared to rely on externally structured learning. Additionally, a significant positive correlation was found between caudatal DaT activity and the internally generated, semantic learning strategy. Unlike these strategic learning characteristics, IQ equivalent and recall total score appeared to vary independently from striatal DaT availability.

CONCLUSION

our findings provide direct evidence that striatal dopaminergic activity is specifically involved in the regulation of strategic learning processes.

Brain lateralization of motor imagery: motor planning asymmetry as a cause of movement lateralization

Movement asymmetry in humans and animals is often considered as being induced by the brain lateralization of the motor system. In the present work, the hemispheric asymmetry for motor planning as a cause of behavioral lateralization was examined. This study was carried out on normal volunteers and patients suffering unilateral brain damage caused by a stroke. Motor planning was evaluated by using the motor imagery of hand movement, a mental representation of a motor pattern that includes its internal simulation but not its real execution. The present study shows marked similarities between virtual movement executed during motor imagery and real movements. Thus, performance time showed a high correlation between real and virtual movements in the following conditions: (1) during dominant and non-dominant hand movements; (2) in simple and complex motor tasks; (3) in young control subjects; (4) in stroke patients; and (5) control subjects aged-matched to stroke patients. Brain strokes increased the performance time in both real and virtual movements. Left-brain strokes decreased the velocity of the real movements in both hands, whereas right-brain strokes mainly disturbed movements in the left hand. A similar effect was observed for virtual movements, suggesting a left-brain dominance for motor planning in humans. However, two-handed movement tasks suggest a complex interaction during motor planning, an interaction that facilitates motor performance during mirror movements and delays motor execution during non-mirror movements.

BIS-BAS sensitivity and cardiac autonomic stress profiles

This study examined the relationship of sensitivities of Gray's behavioral inhibition system (BIS) and behavioral approach system (BAS) to cardiac autonomic stress responses during laboratory tasks among 65 healthy men (n=34) and women (n=31) aged 22-37 years. Carver and White's BIS-BAS scales were used to measure BIS and BAS sensitivities. We measured heart rate (HR), respiratory sinus arrhythmia, and preejection period during mental arithmetic, a reaction time task, and a speech task. Results revealed that BAS sensitivity was related to HR reactivity and parasympathetic withdrawal during the tasks, but was unrelated to baseline levels. BIS sensitivity was unrelated to both reactivity and baseline levels of all measures. Overall, our results suggest that the relationship of the BAS with cardiac reactivity seems to be mediated by the parasympathetic nervous system.

Serial position effects in HIV-infected injecting drug users

This study examined memory and serial position effects in HIV-positive injecting drug users (IDUs), HIV-negative IDUs, and nondrug using control participants. Exploratory analyses investigating a possible mediating role of executive functions with HIV infection, drug use, and memory were also performed. Control participants showed stronger primacy effects than did both HIV-positive and HIV-negative IDUs and also outperformed the drug using groups on all memory measures. Interestingly, analysis of the role of executive functions with HIV infection, drug use, and memory suggested that executive functioning may mediate the verbal memory deficits associated with HIV infection, but not those associated with IDU.

Self-representation: searching for a neural signature of self-consciousness

Human self-consciousness operates at different levels of complexity and at least comprises five different levels of representational processes. These five levels are nonconceptual representation, conceptual representation, sentential representation, meta-representation, and iterative meta-representation. These different levels of representation can be operationalized by taking a first-person-perspective that is involved in representational processes on different levels of complexity. We refer to experiments that operationalize a first-person-perspective on the level of conceptual and meta-representational self-consciousness. Interestingly, these experiments show converging evidence for a recruitment of medial cortical and parietal regions during taking a first-person-perspective, even when operating on different degrees of complexity. These data lend support for the speculative hypothesis, that there exist a neural signature for human self-consciousness that is recruited independent from the degree of representational complexity to be performed.

Relationship of affect recognition with psychopathology and cognitive performance in schizophrenia

The purpose of the present study was to explore the relationship between emotion perception and both psychopathology and cognitive functioning in a group of Greek patients with schizophrenia. Thirty-five patients with schizophrenia were assessed with computerized tests of emotion perception, using visual faces (Kinney's Affect Matching Test, KAMT), prosody (Affective Prosody Test, APT), and visual everyday scenarios (Fantie's Cartoon Test, FCT), as well as a facial recognition test (Kinney's Identity Matching Test, KIMT). The patients were also evaluated with the symptoms dimensions derived from the PANSS (positive, negative, cognitive, depression, and excitement) and a battery of neuropsychological tests measuring executive functions, attention, working memory, verbal and visual memory, visuospatial ability, and visual scanning/psychomotor speed. The three emotion perception and face recognition tests correlated significantly with each other. The KAMT was significantly related to the cognitive symptoms dimension of the PANSS and executive functions. The FCT was significantly related to level of education and attention. Finally, the APT was significantly related to the cognitive symptoms dimension, executive functions, and attention. Our findings regarding the significant relationships of affect perception, both facial and vocal, as well as in everyday scenarios, with several cognitive abilities support the notion that deficits in decoding affective information in schizophrenia could be attributed to impairment in more basic neurocognitive domains.

Evidence that methylphenidate enhances the saliency of a mathematical task by increasing dopamine in the human brain

OBJECTIVE

Methylphenidate is the most commonly prescribed drug for attention deficit hyperactivity disorder (ADHD), yet its therapeutic mechanisms are poorly understood. The objective of this study was to assess if methylphenidate, by increasing dopamine (neurotransmitter involved in motivation) in brain, would enhance the saliency of an academic task, making it more interesting.

METHOD

Healthy subjects (N=16) underwent positron emission tomography with [(11)C]raclopride (dopamine D(2) receptor radioligand that competes with endogenous dopamine for binding) to assess the effects of oral methylphenidate (20 mg) on extracellular dopamine in the striatum. The authors compared the effects of methylphenidate during an academic task (solving mathematical problems with monetary reinforcement) and a neutral task (passively viewing cards with no remuneration). In parallel, the effects of methylphenidate on the interest that the academic task elicited were also evaluated.

RESULTS

Methylphenidate, when coupled with the mathematical task, significantly increased extracellular dopamine, but this did not occur when coupled with the neutral task. The mathematical task did not increase dopamine when coupled with placebo. Subjective reports about interest and motivation in the mathematical task were greater with methylphenidate than with placebo and were associated with dopamine increases.

CONCLUSIONS

The significant association between methylphenidate-induced dopamine increases and the interest and motivation for the task confirms the prediction that methylphenidate enhances the saliency of an event by increasing dopamine. The enhanced interest for the task could increase attention and improve performance and could be one of the mechanisms underlying methylphenidate's therapeutic effects. These findings support educational strategies that make schoolwork more interesting as nonpharmacological interventions to treat ADHD.

Increase in reaction time for solving problems during learning-set formation

Six rhesus monkeys were tested for a change in reaction time for problem-solving during a learning-set task, in which they showed progressive improvement in the rate of learning successive problems of visual discrimination. To evaluate the processing time for cognitive processes in problem-solving, the differences in release latency and movement time between the visual discrimination task and the visuomotor control task were defined. In their first experience, the monkeys required several hundreds of trials for solving the problem, and the Deltarelease latency was constant throughout the learning. With increasing experience, they solved problems within fewer trials than with the first problem. At this stage, the Deltarelease latency was high at the beginning and then decreased. The rise in the Deltarelease latency within the learning acquisition period increased depending on the amount of experience with problems they had solved, whereas the Deltamovement time within that period was not significantly affected by the experience with problems. The present findings suggest that the number of problem-solving experiences could promote profound cognitive processing, which may be related to a conceptual representation that actualizes the flexibility of learning, namely, the learning set.

Increasing the reliability of ipsative interpretations in neuropsychology: a comparison of reliable components analysis and other factor analytic methods

Ipsative approaches to neuropsychological assessment typically involve interpreting difference scores between individual test scores. The utility of these methods is limited by the reliability of neuropsychological difference scores and the number of comparisons between scores. The present study evaluated the utility of difference scores using factor analytic methods, including reliable components analysis (RCA), equally weighted composites and individual neuropsychological measures. Data from 1,364 individuals referred for neuropsychological assessment were factor analyzed and the resulting solutions were used to compute composite scores. Reliabilities and confidence intervals were derived for each method. Results indicated that RCA outperformed other factor analytic methods, but produced a slightly different factor structure. Difference scores derived using orthogonal solutions were slightly more reliable than oblique methods, and both were more reliable than those from equally weighted composites and individual measures. Confidence intervals for difference scores were considerably smaller for factor methods relative to those for individual test comparisons, due to the greater reliability of factor based difference scores and the smaller number of comparisons required. These findings suggest that difference scores derived from orthogonal factor solutions, particularly RCA solutions, may improve reliability for clinical assessment purposes.

How positive affect modulates cognitive control: reduced perseveration at the cost of increased distractibility

A fundamental problem that organisms face in a changing environment is how to regulate dynamically the balance between stable maintenance and flexible switching of goals and cognitive sets. The authors show that positive affect plays an important role in the regulation of this stability-flexibility balance. In a cognitive set-switching paradigm, the induction of mild increases in positive affect, as compared with neutral or negative affect, promoted cognitive flexibility and reduced perseveration, but also incurred a cost in terms of increased distractibility. Rather than influencing set switching in an unspecific way, positive affect thus exerted opposite effects on perseveration and distractibility. Results are consistent with neuropsychological models according to which effects of positive affect on cognitive control are mediated by increased dopamine levels in frontal brain areas.

Integration of spatial maps in pigeons

The integration of spatial maps in pigeons was investigated using a spatial analog to sensory preconditioning. The pigeons were tested in an open-field arena in which they had to locate hidden food among a 4x4 grid of gravel-filled cups. In phase 1, the pigeons were exposed to a consistent spatial relationship (vector) between landmark L (a red L-shaped block of wood), landmark T (a blue T-shaped block of wood) and the hidden food goal. In phase 2, the pigeons were then exposed to landmark T with a different spatial vector to the hidden food goal. Following phase 2, pigeons were tested with trials on which they were presented with only landmark L to examine the potential integration of the phase 1 and 2 vectors via their shared common elements. When these test trials were preceded by phase 1 and phase 2 reminder trials, pigeons searched for the goal most often at a location consistent with their integration of the L-->T phase 1 and T-->phase 2 goal vectors. This result indicates that integration of spatial vectors acquired during phases 1 and 2 allowed the pigeons to compute a novel L-->goal vector. This suggests that spatial maps may be enlarged by successively integrating additional spatial information through the linkage of common elements.

Developmental aspects of timing behavior in children

This research examined the association of age, sex, and intelligence on the performance of a time production (temporal response differentiation, TRD) task. Variations of this task have been used extensively with both animals and humans to study factors that affect aspects of timing ability. The participants in this study (720 children, ages 5 to 13 years) were required to hold down a response lever for at least 10 s, but no more than 14 s, to receive a nickel. Older children made more correct lever holds and exhibited less variability in the duration of their lever holds than did the younger children. Boys and girls performed similarly on this task, whereas children with higher IQs made more correct lever holds. Young children with below average IQs exhibited increased variability in lever hold duration compared with young children with average and above average IQs. The results of this study illustrate that both age and intelligence influence timing ability. The use of this timing task in children, which also has been widely used in animal models, provides unique opportunities for interspecies comparisons.

Age-related differences in arithmetic problem-verification strategies

To test age-related differences in split and problem-difficulty effects, adults between the ages of 20 and 80 years (N = 138) performed a simple and a complex inequality verification task (e.g., 6 + 3 < 11, 271 + 182 < 458; true or false?). Split effects in verification tasks (i.e., better performance for large-split than for small-split problems) reflect strategy selection between nonexhaustive verification (e.g., evaluation of plausibility; estimation) and exhaustive verification (e.g., retrieval; calculation). Problem-difficulty effects (i.e., better performance for easy than hard problems) reflect calculation processing. Results showed decreased split effects across age groups, particularly in the complex task. Moreover, problem-difficulty effects did not vary across age groups. Age-related changes were mostly mediated by age-related declines in processing speed.

Brain potentials index executive functions during random number generation

The generation of random sequences is considered to tax different executive functions. To explore the involvement of these functions further, brain potentials were recorded in 16 healthy young adults while either engaging in random number generation (RNG) by pressing the number keys on a computer keyboard in a random sequence or in ordered number generation (ONG) necessitating key presses in the canonical order. Key presses were paced by an external auditory stimulus to yield either fast (1 press/800 ms) or slow (1 press/1300 ms) sequences in separate runs. Attentional demands of random and ordered tasks were assessed by the introduction of a secondary task (key-press to a target tone). The P3 amplitude to the target tone of this secondary task was reduced during RNG, reflecting the greater consumption of attentional resources during RNG. Moreover, RNG led to a left frontal negativity peaking 140 ms after the onset of the pacing stimulus, whenever the subjects produced a true random response. This negativity could be attributed to the left dorsolateral prefrontal cortex and was absent when numbers were repeated. This negativity was interpreted as an index for the inhibition of habitual responses. Finally, in response locked ERPs a negative component was apparent peaking about 50 ms after the key-press that was more prominent during RNG. Source localization suggested a medial frontal source. This effect was tentatively interpreted as a reflection of the greater monitoring demands during random sequence generation.

Effects of amisulpride, risperidone and chlorpromazine on auditory and visual latent inhibition, prepulse inhibition, executive function and eye movements in healthy volunteers

In view of the evidence that cognitive deficits in schizophrenia are critically important for long-term outcome, it is essential to establish the effects that the various antipsychotic compounds have on cognition, particularly second-generation drugs. This parallel group, placebo-controlled study aimed to compare the effects in healthy volunteers (n = 128) of acute doses of the atypical antipsychotics amisulpride (300 mg) and risperidone (3 mg) to those of chlorpromazine (100 mg) on tests thought relevant to the schizophrenic process: auditory and visual latent inhibition, prepulse inhibition of the acoustic startle response, executive function and eye movements. The drugs tested were not found to affect auditory latent inhibition, prepulse inhibition or executive functioning as measured by the Cambridge Neuropsychological Test Battery and the FAS test of verbal fluency. However, risperidone disrupted and amisulpride showed a trend to disrupt visual latent inhibition. Although amisulpride did not affect eye movements, both risperidone and chlorpromazine decreased peak saccadic velocity and increased antisaccade error rates, which, in the risperidone group, correlated with drug-induced akathisia. It was concluded that single doses of these drugs appear to have little effect on cognition, but may affect eye movement parameters in accordance with the amount of sedation and akathisia they produce. The effect risperidone had on latent inhibition is likely to relate to its serotonergic properties. Furthermore, as the trend for disrupted visual latent inhibition following amisulpride was similar in nature to that which would be expected with amphetamine, it was concluded that its behaviour in this model is consistent with its preferential presynaptic dopamine antagonistic activity in low dose and its efficacy in the negative symptoms of schizophrenia.

A prospective study of the association among impaired executive functioning, childhood attentional problems, and the development of bipolar disorder

Studies of adults who have been diagnosed with, and treated for, bipolar disorder have shown that these patients exhibit impairment on measures of executive functioning. However, it is unclear whether executive dysfunction precedes the diagnosis of bipolar illness, or develops subsequent to its onset. Moreover, investigators have failed to control for the effects of premorbid attentional problems on cognitive performance in these patients. The present authors explored these questions using data from a longitudinal prospective study of individuals at risk for major mood disorder. Results revealed that 67% of participants who met criteria for bipolar disorder in young adulthood showed impairment on the Wisconsin Card Sorting Test (WCST) when they were assessed during adolescence, as compared with 17% of individuals with no major mood diagnosis, and 19% with unipolar depression. This association between performance on the WCST and bipolar illness was not accounted for by high rates of premorbid attentional disturbance. In fact, among participants with early attentional problems, only those who ultimately developed bipolar disorder exhibited impairment on the WCST. Early attentional problems that preceded unipolar depression or no mood disorder were not associated with executive dysfunction.

The executive clock drawing task (CLOX) is a poor screening test for executive dysfunction in Chinese elderly patients with subcortical ischemic vascular disease

Executive dysfunction (ED) is a prominent feature of subcortical ischemic vascular disease. A screening test for ED is lacking among Chinese. The objective of the study is to investigate the validity and reliability of a Chinese version of the Executive clock drawing task (CLOX) in screening ED among Chinese elderly patients with small subcortical infarct (SSI). The Chinese version of CLOX correlated with MMSE, CDRS I/P, and WCST perseverative errors. However, multivariate regression analysis showed that only education (R(2) change=0.22, p < 0.001 ) and MMSE (R(2) change=0.35, p < 0.001), but none of the standard executive function tests, significantly accounted for the variance in the CLOX. Test-retest (r=0.84) and inter-rater reliability (r=0.84) were high for the CLOX. Conclusions. Although the CLOX is reliable, it is not valid in detecting ED in Chinese elderly patients with SSI.

When Planning Fails: Individual Differences and Error-related Brain Activity in Problem Solving

The neuronal processes underlying correct and erroneous problem solving were studied in strong and weak problem-solvers using functional magnetic resonance imaging (fMRI). During planning, the right dorsolateral prefrontal cortex was activated, and showed a linear relationship with the participants' performance level. A similar pattern emerged in right inferior parietal regions for all trials, and in anterior cingulate cortex for erroneously solved trials only. In the performance phase, when the pre-planned moves had to be executed by means of an fMRI-compatible computer mouse, the right dorsolateral prefrontal cortex was again activated jointly with right parahippocampal cortex, and displayed a similar positive relationship with the participants' performance level. Incorrectly solved problems elicited stronger bilateral prefrontal and left inferior parietal activations than correctly solved trials. For both individual ability and trial-specific performance, our results thus demonstrate the crucial involvement of right prefrontal cortex in efficient visuospatial planning.

Independent control of processing strategies for different locations in the visual field

We investigated how the selection of information-processing strategies is organized. We contrasted three alternative ways in which strategies may be controlled: a centralized mechanism, a hemisphere-specific mechanism or a local mechanism. We built on the previous observation that the size of the noise-compatibility effect (flanker effect) is influenced by observers' expectancies for compatible or incompatible arrays. In three experiments, we varied the probabilities of compatible or incompatible noise in different locations of the visual field. We found that observers can adapt their processing strategies, as indicated by changes in the size of the noise-compatibility effect, independently in the left and right hemifields. However, processing of midline stimuli is determined by the expectancies existing in the lateral locations. These data support the notion of a hemisphere- or location-specific selection of processing strategies and suggest that the strategy selection process is not unitary.

Aging and path integration skill: kinesthetic and vestibular contributions to wayfinding

In a triangle completion task designed to assess path integration skill, younger and older adults performed similarly after being led, while blindfolded, along the route segments on foot, which provided both kinesthetic and vestibular information about the outbound path. In contrast, older adults' performance was impaired, relative to that of younger adults, after they were conveyed, while blindfolded, along the route segments in a wheelchair, which limited them principally to vestibular information. Correlational evidence suggested that cognitive resources were significant factors in accounting for age-related decline in path integration performance.

Inductive reasoning and implicit memory: evidence from intact and impaired memory systems

In this study, we modified a classic problem solving task, number series completion, in order to explore the contribution of implicit memory to inductive reasoning. Participants were required to complete number series sharing the same underlying algorithm (e.g., +2), differing in both constituent elements (e.g., 2468 versus 57911) and correct answers (e.g., 10 versus 13). In Experiment 1, reliable priming effects emerged, whether primes and targets were separated by four or ten fillers. Experiment 2 provided direct evidence that the observed facilitation arises at central stages of problem solving, namely the identification of the algorithm and its subsequent extrapolation. The observation of analogous priming effects in a severely amnesic patient strongly supports the hypothesis that the facilitation in number series completion was largely determined by implicit memory processes. These findings demonstrate that the influence of implicit processes extends to higher level cognitive domain such as induction reasoning.

Trend detection via temporal difference model predicts inferior prefrontal cortex activation during acquisition of advantageous action selection

The process of accurately predicting which actions are associated with advantageous versus disadvantageous outcomes is an important function of daily life. An integral part of this process is being able to detect when the association between an action and an outcome changes. This investigation examined the hypothesis that the inferior prefrontal cortex is critical for the detection of trends and that a trend process derived from the temporal difference model accomplishes this detection. Nineteen normal right-handed volunteers completed 120 4-s trials of a Rock Paper Scissors (RPS) task during functional magnetic resonance imaging. Subjects acquired the selection of advantageous actions during the RPS task. Activations in the medial frontal gyrus (BA 10), left ventrolateral frontal gyrus (BA 11/47), and left pallidum were significantly higher during trials in which subjects acquired the advantageous action. The time course of individually derived trend detection functions was found to be time-locked to the hemodynamic changes in the inferior frontal gyrus. These findings are consistent with the hypothesis that the inferior prefrontal cortex computes a trend from previously experienced action-outcome sequences based on a value function derived from the temporal difference model.

Executive dysfunction in Alzheimer disease

BACKGROUND

Executive dysfunction (EDF) is common in Alzheimer disease (AD); however, its relationship to other symptoms is difficult to assess in patients with AD.

OBJECTIVES

To determine the prevalence of EDF and study its relationship to cognitive, functional, and neuropsychiatric symptoms in patients with AD.

DESIGN, SETTING, AND PATIENTS

A retrospective analysis of data from participants in the English Instruments Protocol of the Alzheimer's Disease Cooperative Study. Subjects were drawn from a sample of patients evaluated at tertiary referral centers.

RESULTS

A total of 64% of AD patients were classified as having EDF. Patients with EDF performed worse on tests of cognition (P <.001), dementia severity (P <.001), and activities of daily living (P =.01) and had more frequent symptoms of psychosis (P =.03) with greater emergence during the 12-month interval (P =.03) compared with patients with normal executive function. Less than 30% of the variance in executive function performance was explained by cognitive measures.

CONCLUSION

These findings support the assessment of executive function in persons with AD and the importance of frontal lobe dysfunction in AD.

Spatiotemporal brain dynamics during preparatory set shifting: MEG evidence

Humans can flexibly alter a plan of action to adjust their behavior adaptively in changing environments. Functional neuroimaging has shown distinct patterns of activation across a frontoparietal network responsible for switching and updating such plans of action or 'task sets.' However, little is known about the temporal order of activations within prefrontal or across with posterior regions subserving set-shifting operations. Here, whole-head magnetoencephalography (MEG) was used to explore the spatiotemporal brain dynamics in a modified version of the Wisconsin card-sorting test (WCST). Our task was designed to examine preparation of set-shifting rather than set-acquisition operations time locked to context-informative cues. Three cortical regions showed a larger number of MEG activity sources in response to shift and relative to nonshift cues: (a) inferior frontal gyrus (IFG; BA 45, 47/12), (b) anterior cingulate cortex (ACC; BA 24, 32), and (c) supramarginal gyrus (SMG; BA 40). Importantly, the timing of MEG activation differed across these regions. The earliest shift-related MEG activations were detected at the IFG (100-300 ms postcue onset), followed by two further peaks at the ACC (200-300 and 400-500 ms) and the SMG (300-400 and 500-600 ms). Several other prefrontal and posterior cortical areas were similarly activated by both shift and nonshift preparatory cues. The resulting temporal pattern of interactions within prefrontal and across with posterior association cortices is coherent with current models of task switching and provides novel information about the temporal course of brain activations responsible for the executive control of attention.

Activations of "motor" and other non-language structures during sentence comprehension

In this paper we report the results of an experiment in which subjects read syntactically unambiguous and ambiguous sentences which were disambiguated after several words to the less likely possibility. Understanding such sentences involves building an initial structure, inhibiting the non-preferred structure, detecting that later input is incompatible with the initial structure, and reactivating the alternative structure. The ambiguous sentences activated four areas more than the unambiguous sentences. These areas are the left inferior frontal gyrus (IFG), the right basal ganglia (BG), the right posterior dorsal cerebellum (CB) and the left median superior frontal gyrus (SFG). The left IFG is normally activated when syntactic processing complexity is increased and probably supports that function in the current study as well. We discuss four hypotheses concerning how these areas may support comprehension of syntactically ambiguous sentences. (1) The left IFG, right CB and BG could support articulatory rehearsal used to support the processing of ambiguous sentences. This seems unlikely since the activation pattern associated with articulatory rehearsal in other studies is not similar to that seen here. (2) The CB acts as an error detector in motor processing. Error detection is important for recognizing that the wrong sentence structure has been chosen initially. (3) The BG acts to select and sequence movements in the motor domain and in cognitive domains may serve to inhibit competing and completed plans which is not unlike inhibiting the initially non-preferred structure or "unchoosing" the initial choice when incompatible syntactic input is received. (4) The left median SFG is relevant for the evaluation of plausibility. Evaluating the plausibility of the two possibilities provides an important basis for choosing between them. The notion of the use of domain general cognitive processes to support a linguistic process is in line with recent suggestions that the a given area may subserve a specific cognitive task because it carries out an appropriate sort of computation rather than because it supports a specific cognitive domain.