Biomedical subjects

K Rubia

Publications and source records attributed to K Rubia.

7 recordsLinked to original sources

PubMed2000

Functional frontalisation with age: mapping neurodevelopmental trajectories with fMRI.

The aim of this study was to investigate whether previously observed hypofrontality in adolescents with attention deficit-hyperactivity disorder (ADHD) during executive functioning [Rubia K, Overmeyer S, Taylor E, Brammer M, Williams S, Simmons A, Andrew C, Bullmore ET. Hypofrontality in attention deficit hyperactivity disorder during higher order motor control: a study using fMRI. Am J Psychiatry 1999;156(6):891-896] could be attributed to delayed maturation of frontal cortex. Brain activation of 17 healthy subjects, 9 adolescents and 8 young adults, during performance of a motor response inhibition task and a motor timing task was measured using functional magnetic resonance imaging (fMRI). The effect of age on brain activation was estimated, using the analysis of variance and regression, at both voxel and regional levels. In the delay task, superior performance in adults was paralleled by a significantly increased power of response in a network comprising prefrontal and parietal cortical regions and putamen. In the stop task, alternative neuronal routes--left hemispheric prefrontal regions in adults and right hemispheric opercular frontal cortex and caudate in adolescents--seem to have been recruited by the two groups for achieving comparable performances. A significant age effect was found for the prefrontal activation in both task, confirming the hypothesis of a dysmaturational pathogenesis for the hypofrontality in ADHD.

Adolescent↗

PubMed1999

Hypofrontality in attention deficit hyperactivity disorder during higher-order motor control: a study with functional MRI.

OBJECTIVE: Functional magnetic resonance imaging (MRI) was used to investigate the hypothesis that attention deficit hyperactivity disorder (ADHD) is associated with a dysfunction of prefrontal brain regions during motor response inhibition and motor timing. METHOD: Generic brain activation of seven adolescent boys with ADHD was compared to that of nine comparison subjects equivalent in sex, age, and IQ while they were performing a stop task, requiring inhibition of a planned motor response, and a motor timing task, requiring timing of a motor response to a sensory cue. RESULTS: The hyperactive adolescents showed lower power of response in the right mesial prefrontal cortex during both tasks and in the right inferior prefrontal cortex and left caudate during the stop task. CONCLUSIONS: ADHD is associated with subnormal activation of the prefrontal systems responsible for higher-order motor control. Functional MRI is a feasible technique for investigation of neural correlates of ADHD.

Adolescent↗

PubMed1999

Synchronization, anticipation, and consistency in motor timing of children with dimensionally defined attention deficit hyperactivity behaviour.

We tested the hypothesis that children with hyperactive behaviour are impaired in the temporal organization of their motor output. The performance of 11 boys, scoring above a cut-off on standard scales of overactivity and inattention, was compared to that of controls in progressively more complex Motor-timing tasks. The tasks administered required self-paced and externally paced Sensorimotor Synchronization and Sensorimotor Anticipation. Deficits at a perceptual level were investigated with a Time-discrimination task. As hypothesized, we found that hyperactive children had no deficits in their perception of time but were impaired in timing their motor output. Hyperactive children were more inconsistent than controls in maintaining a freely chosen tapping rhythm, in synchronizing and in anticipating their motor response to external visual stimulation.

Attention Deficit Disorder with Hyperactivity↗

PubMed1998

Prefrontal involvement in "temporal bridging" and timing movement.

Brain activity exclusively related to a temporal delay has rarely been investigated using modern brain imaging. In this study we exploited the temporal resolution of functional magnetic resonance imaging (fMRI) to characterise, by sinusoidal regression analysis, differential neuroactivation patterns induced in healthy subjects by two sensorimotor synchronization tasks different in their premovement delay of either 0.6 s or 5 s. The short event rate condition required rhythmic tapping, while the long event rate condition required timing of intermittent movements. Left rostral prefrontal cortex, medial frontal cortex, SMA and supramarginal gyrus demonstrated increased MR signal intensity during low frequency synchronization, suggesting that these brain regions form a distributed neural network for cognitive time management processes, such as time estimation and motor output timing. Medial frontal cortex showed a biphasic pattern of response during both synchronization conditions, presumably reflecting frequency-independent motor output related attention. As predicted, sensorimotor and visual association areas demonstrated increased MR signal intensity during high frequency synchronization.

Adult↗

PubMed1998

Inhibitory dysfunction in hyperactive boys.

Recent evidence suggests that the main deficit in childhood hyperactivity is in frontal lobe-mediated self-regulative functions such as inhibitory control. Hyperactives have consistently been shown to perform poorly on the stop task, which is a laboratory measurement of inhibitory control. This study was aimed at extending knowledge about inhibitory processes involved in the hyperactive's performance on this task. For this purpose, the performance of 11 pervasive hyperactives was compared to the performance of normal children on two stop tasks which differed from each other in the contingency of timing of the stop signal. In Stop1 stop signals were internally related, i.e. presented at time intervals after onset of the response stimulus, whereas in Stop2 stop signals were externally related, i.e. presented at time intervals related to the subject's own go-process. Both tasks were modifications of the classical stop task in modality of the stop signal visual instead of auditory and in event rate, which was half-shortened. The aim of this study was: (a) to replicate the findings of deficient inhibitory functions in hyperactive children in the stop task in spite of modifications in modality and event rate; and (b) to elucidate (dis)similarities of stopping processes or of group differences in these stopping processes triggered by stop delays related either to external or to internal processes. Hyperactive children were less efficient than controls in inhibiting their motor response in both versions of the stop task. independent of whether the stop signals were externally or internally related. Furthermore, the go-process of the hyperactives was more variable and erratic in both tasks. Thus, the results strengthen the effectiveness of stop tasks in distinguishing hyperactive from normal children.

Attention↗

PubMed1998

Neuroelectric mapping reveals precursor of stop failures in children with attention deficits.

Children with attention deficit disorders (ADD) may have specific problems with response inhibition in the STOP task. This task requires that subjects stop responses to a primary task if a second signal follows. However, it is unclear whether these problems reflect an impairment of the stopping process per se, whether they are related to reduced frontal lobe activation and whether they are confined to severe and pervasive forms of ADD. In 11 ADD and nine control children, 32 channel event-related EEG potentials (ERPs) were recorded in a STOP and a delayed GO task. Mapping revealed that both tasks evoked a similar sequence of neuroelectric microstates, i.e. of time segments with stable map topography. Adaptive segmentation identified the transition between these microstates. Reliable group differences were found in several microstates and in both tasks despite matched performance. In the GO task, ADD children had topographically altered P2/N2 microstates and attenuated P300-type microstates. In the STOP task, a topographically altered N1 microstate which coincided with the onset of the stop signal preceded the stop failures of ADD children. The timing of this microstate is too early to reflect deficits in actual stop signal processing and instead suggests altered initial orienting of attention to the primary signal in ADD children. Imaging with low resolution tomography (LORETA) during this microstate to stop failures indicated mainly posterior activation for both groups and increased rather than reduced frontal activation in ADD children. For a later microstate (P550), LORETA indicated strong frontal activation after successful stopping, but no group differences. The results suggest that information processing of ADD children deviates during activation of posterior mechanisms which may be related to the orienting of attention and which precedes and partly determines inhibitory control problems in ADD.

Arousal↗

PubMed1997

Time estimation as a neuronal network property: a lesion study.

The neural substrate of estimating short temporal intervals is still unknown. We investigated the ability of patients with infarctions of the middle cerebral artery of either the left or the right hemisphere to estimate verbally and produce time intervals of seconds by counting. Patients showed long-lasting and stable deficits in time estimation in both methods, with either extreme acceleration or deceleration in apparent time compared with healthy controls. A lesion of the posterior part of the supralenticular white matter proved to be responsible for these deficits. Disruption of interneuronal communication therefore leads to a lasting alteration of a learned time-pacing synchronized to conventional time units.

Adult↗