Biomedical subjects

P Vendrell

Publications and source records attributed to P Vendrell.

At least 19 recordsLinked to original sources

PubMed2006

Abnormal orbitofrontal development due to prematurity.

OBJECTIVE: To investigate the effects of prematurity on sulcal formation. METHODS: We evaluated the depth and volume of the primary olfactory sulcus (developed at 16 weeks' gestation) and the secondary orbital sulci (which start to develop at 28 weeks' gestation) in a sample of 22 adolescents with history of very-preterm birth (VPTB). We compared this preterm sample with a sample of subjects born at term and matched by age, gender, and sociocultural status. The Anatomist/BrainVISA 3.0.1 package was used to identify and quantify the sulci. In addition, voxel-based morphometry (VBM) was used to analyze possible reductions of gray and white matter in the orbitofrontal area. RESULTS: Compared with controls, we found a significant reduction in the secondary sulci depth but not in the primary sulcus in the VPTB. VBM analysis showed reduced gray-matter volume in VPTB in the orbital region. CONCLUSIONS: Premature birth affects cerebral gyrification, and this impairment is not reversible during childhood. Identification of the specific factors involved in abnormal brain maturation may lead to effective interventions.

Adolescent↗

PubMed2001

Effects of bilateral subthalamic stimulation on cognitive function in Parkinson disease.

BACKGROUND: Chronic bilateral subthalamic deep brain stimulation (STN-DBS) is known to improve motor function in patients with Parkinson disease (PD). However, the possible effects of STN-DBS on neuropsychological functions have been studied less. OBJECTIVE: To investigate the effects of STN-DBS on neuropsychological functions in PD. DESIGN: Before-after trial. PATIENTS AND METHODS: Fifteen consecutive patients were assessed before and 3 months after implantation of stimulators for STN-DBS (postsurgical assessment with the stimulators switched on). Both assessments were performed with patients in a drug-free condition. The neuropsychological battery consisted of tests measuring memory and visuospatial and frontal functions. RESULTS: The comparison between presurgical and postsurgical performance showed a moderate deterioration in verbal memory and prefrontal and visuospatial functions, and a moderate improvement in a prefrontal task and obsessive-compulsive traits. The motor state improved in all patients. CONCLUSION: Therapy with STN-DBS improves motor symptoms in PD without any clinically relevant neuropsychological deterioration.

Aged↗

PubMed2001

The effect of medial frontal and posterior parietal demyelinating lesions on stroop interference.

Functional imaging has consistently shown that attention-related areas of medial frontal and posterior parietal cortices are active during the attentional conflict induced by color naming in the presence of distracting words (Stroop task). Such studies, however, have provided few details of the correlational nature between observed regional brain activations and reaction time delay occurring in this situation. We analyzed the effect of medial frontal and posterior parietal lesions on the Stroop response in a group of patients with multiple sclerosis, a neurological disorder in which Stroop response speed is affected to varying degrees. Forty-five patients were assessed using a computer-presented verbal version of the Stroop task and specific MRI protocol. Demyelination areas were measured on five anatomical divisions of the medial frontal white matter and on white matter of the posterior parietal lobe. We found that a combination of frontal and parietal lesion measurements accounted for 45% of the Stroop interference time variance. Patients with more right frontal than left parietal demyelination showed slowed Stroop responses, whereas the predominance of lesions in the left posterior parietal region was associated with a reduced Stroop interference. These results may contribute to defining the specific participation of these attention-related brain areas in the conflict of attention represented by the Stroop paradigm. They also help to explain the variability of the Stroop effect in multiple sclerosis patients and suggest that the Stroop test does not assess just a single cognitive operation, but rather the combined effect of anatomically segregated neural processes.

Adult↗

PubMed2001

Obsessive-compulsive symptoms in Parkinson's disease.

To systematically investigate obsessive-compulsive traits in Parkinson's disease, patients were administered the Maudsley obsessional-compulsive inventory (MOCI) and a modification of the Leyton obsessional inventory (LOI) to a sample of non-demented and non-depressed patients with Parkinson's disease. Patients with severe Parkinson's disease showed more obsessive traits than normal controls in MOCI and LOI total scores, and in the "checking", "doubting", and "cleaning" subscales of the MOCI. By contrast, patients with mild disease did not differ from controls. A significant correlation was found between severity and duration of illness and MOCI total score. These results support the involvement of basal ganglia in obsessive-compulsive symptomatology. As patients with mild Parkinson's disease did not differ from controls, obsessive-compulsive disorder does not seem to be directly related to the initial nigrostriatal dopaminergic deficiency which causes clinical Parkinson's disease symptomatology. The appearance of obsessive symptoms could be related to the subset of neurochemical changes taking place at the level of the basal ganglia circuitry as disease progresses.

Female↗

PubMed2001

MRI atrophy parameters related to cognitive and motor impairment in Parkinson's disease.

BACKGROUND: Patients with Parkinson's disease (PD) show specific neuropsychological deficits in attention, memory, visuospatial or frontal lobe functions, which can arise from degeneration of different cerebral structures. OBJECTIVE: The aim of the present study was to analyze the role of focal degeneration (basal ganglia and substantia nigra) and diffuse cerebral atrophy (ventricular enlargement) in motor/cognitive impairment in PD. PATIENTS AND METHODS: We administered to 14 patients with advanced PD the following tests: Purdue Pegboard, Rey's Auditory-Verbal Learning test (RAVLT), Benton's Line Orientation, Trail Making, phonemic verbal fluency and Stroop test. Ventricular system, caudate and putamen nuclei and pars compacta of the substantia nigra were quantitatively measured by magnetic resonance imaging. Correlation analyses were carried out. RESULTS: The results showed that ventricular enlargement is negatively correlated with the performance on RAVLT and Stroop test. No relationship was found between caudate atrophy and cognitive deficits. Degeneration of putamen nucleus was found to be associated with motor deficits. CONCLUSION: Memory and frontal impairment are related to diffuse cerebral degeneration and the motor deficit is related to degeneration of the putamen nucleus.

Aged↗

PubMed2000

Effects of unilateral posteroventral pallidotomy on 'on-off' cognitive fluctuations in Parkinson's disease.

In Parkinson's disease, cognitive performance can vary according to levodopa levels (on-off states). Both positive and negative effects of dopaminergic stimulation have been reported. Pallidotomy is also able to change cognitive performance, in addition to levodopa pharmacokinetics. The aim of this investigation was to study the effects of pallidotomy on cognitive on-off fluctuations in Parkinson's disease. A brief neuropsychological battery was administered to 15 PD patients during on and off states before and after surgery. Before pallidotomy, patients performed better in the on condition on Trail Making test B; after pallidotomy levodopa no longer improved performance, and the interaction between surgery and state was significant. In relation to the difference between preoperative and postoperative performance in Trail Making B test, there was a significant postsurgical improvement only in off state. Verbal fluency decreased after pallidotomy in both on and off conditions. Our results suggest that pallidotomy can change the effects of levodopa on neuropsychological functions.

Aged↗

PubMed1999

Cognitive and behavioral changes after unilateral posteroventral pallidotomy: relationship with lesional data from MRI.

We investigated cognitive and behavioral changes after unilateral posteroventral pallidotomy, and their relationship with lesion size and location as identified in magnetic resonance image quantitative analysis. Fifteen consecutive patients with Parkinson's disease were assessed neuropsychologically before and after unilateral posteroventral pallidotomy (five right and 10 left). Immediate postsurgery evaluation (1 week) demonstrated significant worsening of memory, motor learning, motor speed, and verbal fluency. In the 3-month follow up, learning, memory, and speed returned to the presurgical level, but verbal fluency remained below the baseline. Significant improvements were observed in visuospatial functions and obsessive-compulsive behavior. Lesional volume did not correlate with neuropsychologic changes. Left lesions produced more impairment in verbal fluency than right-sided lesions. Regression analysis identified two lesional areas in the pallidum mediale internum. These regions accounted for 68% of the variance in the visuospatial changes.

Aged↗

PubMed1998

Overestimation and unreliability in "feeling-of-doing" judgements about temporal ordering performance: impaired self-awareness following frontal lobe damage.

"Feeling-of-doing" accuracy in a temporal ordering task in 33 patients with frontal lobe lesions and a matched control group was investigated. The temporal ordering task used word lists that had high, medium, or no semantic interrelatedness. Patients with frontal lobe lesions showed an impairment in temporal ordering across all three word lists. Both groups performed better on the lists with higher semantic interrelatedness. Patients with frontal lobe lesions overestimated their ability to order words accurately. On the less semantically interrelated lists, metamemory judgment in patients with frontal lesions did not correlate with their performance. These results indicate that both temporal order judgment and metacognitive decisions about temporal order judgment are subserved by the prefrontal cortex and further clarifies the role of the frontal lobes in behavioral monitoring.

Adult↗

PubMed1997

Impaired estimation of word occurrence frequency in frontal lobe patients.

Neuroanatomical correlates of the estimation of occurrence frequency have received little attention. This study investigates the possible role of the frontal lobe in estimating word occurrence frequency. A sample of 27 patients with frontal lesions were matched with normal controls by sex, age and years of education. Significant differences between patients and controls were found for frequency estimation, but not for item recognition. Studying accuracy of estimation as a function of actual frequency, the frontal group performed worse, especially at high frequencies of occurrence. As far as lesion lateralization is concerned, the right frontal subgroup performed worse than the control group in the estimation of frequency. Our results suggest that the prefrontal cortex plays a role in estimating word occurrence and that there is a dissociation between frequency memory and recognition memory, pointing to the involvement of two different cerebral systems.

Adult↗

PubMed1996

Frontal lobe activation during word generation studied by functional MRI.

AIMS: To further delimit the specific verbal operations occurring in the dorsolateral frontal cortex during the generation of words. METHODS: Different verbal fluency tasks guided by distinct specifications (phonological, semantic, or automatic production of words) were used in a functional magnetic resonance study. The study group comprised 10 right-handed normal subjects ranging in age from 23 to 27 years. Functional magnetic resonance images were obtained in a 1.5-Tesla magnet using a spoiled GRASS sequence. RESULTS: Noticeable activation was found during the word generation tasks in the dorsolateral frontal cortex. The region showing the most prominent activation was the posterior part of the left middle frontal gyrus. Nevertheless, the different tasks each had a different activation effect. The phonologically guided generation of words produced the most consistent activation of the middle frontal gyrus, which mainly involved the premotor cortex. CONCLUSION: The results suggest that operations concerned with the generation of sound sequences, rather than the amount of produced words or their semantics, are responsible for sustained focal activity observed in the frontal lobes during verbal fluency tasks.

Adult↗

PubMed1996

Presurgical identification of the primary sensorimotor cortex by functional magnetic resonance imaging.

The ability of functional magnetic resonance (MR) imaging to detect a selective sensorimotor cortex activation in healthy subjects and the feasibility of motor activation in patients with lesions around the central sulcus were investigated. Twenty-five healthy volunteers performed 100 motor activation trials, using a variety of motor tasks, which were monitored by several image analysis methods. The functional images were obtained using a 1.5-tesla standard MR imaging system magnet with blood oxygenation level-dependent contrast. Four patients were assessed using functional MR imaging and invasive cortical mapping. Rolandic cortex activation was observed in 98% of the trials performed on healthy subjects in which no head motion occurred. Nevertheless, the cortical response was not selective in a task-rest analysis due to concurrent activation of neighboring regions. Across-task comparison analyses were useful in cancelling nonrelevant activity in most cases (86%). In the patient group, the region identified as the sensorimotor cortex by invasive means corresponded accurately to the area that was activated in functional MR imaging. Present data support the feasibility of detecting selective activation of the rolandic cortex, even in the clinical setting, leading the authors to suggest the usefulness of this widely available technique in surgical planning.

Adult↗

PubMed1995

[Study of cerebral activity with functional magnetic resonance].

BACKGROUND: Functional magnetic resonance is a new imaging method which allows the incruent observation of human cerebral activity. The authors describe their method of functional magnetic resonance and the results of cerebral activation. METHODS: A total of 364 functional sequences were performed in 52 volunteers with a magnetic resonance system of 1.5 Tesla. A gradient echo sequence with a long echo time sensitive to the changes in oxygenation of venous blood was used. Different cortical areas were stimulated by visual, motor and language maneuvers and by complex mental operations. RESULTS: Different cerebral areas representative of different levels of cerebral functional complexity were consistently activated and reproduced. Experiments of activation of primary cerebral cortex (visual and motor), premotor regions, specific area of language and areas of cortical association for cognitive operations are described. CONCLUSIONS: Functional magnetic resonance imaging is a sensitive method for the observation of cerebral activity and provides functional images with great spatial and temporal resolution. This may be useful in both clinical and basic investigation.

Adult↗

PubMed1995

The role of prefrontal regions in the Stroop task.

The Stroop is a classical paradigm that presumably involves the inhibition of automatic responses and is frequently used to assess the frontal lobe functions. We investigated the effect of discrete prefrontal lesions in a Stroop task. A sample of 32 patients with frontal lesions were matched with normal controls by sex, age and years of education. Significant differences between patients and controls were found for errors but not for reaction time. Regression analysis showed that the region most related to errors was the right prefrontal lateral cortex. Left lobectomies did not impair the Stroop performance. Our results favour the role of the right prefrontal cortex in sustained attention, and disagree with the conception of the left prefrontal cortex having a role in the inhibition of verbal automatic responses.

Adult↗

PubMed1993

When does human brain development end? Evidence of corpus callosum growth up to adulthood.

To locate structural changes in the brain accounting for the increasing effectiveness in cognition and skills that occurs at the final stage of behavioral development, we attempted to determine the age at which the corpus callosum completes its active growth period. We assessed the growth rate of the corpus callosum by measuring its area twice on midsagittal magnetic resonance imaging scans separated by a 2-year interval, in a series of 90 subjects with a wide range of ages. We observed an increase in the size of the corpus callosum as long as human mentation expands, up to the middle 20s. Clinical and experimental data about the corpus callosum, together with the present findings, suggest that the corpus callosum is part of the highest order-latest maturing neural network of the brain.

Adolescent↗

PubMed1993

Diurnal oscillations in hemispheric performance.

Folkard (1979, 1990) suggested that diurnal changes in performance may reflect a morning-evening decrease in the degree of left-hemisphere dominance. Forty-eight right-handed women performed verbal and spatial hemifield tachistoscopic tasks at four separate times of day. Supporting the above hypotheses, changes in accuracy over the day showed a left-hemisphere advantage at 12:00 and a right-hemisphere advantage at 19:45, whereas changes in speed were symmetrical both in verbal and spatial tasks. These changes occurred only when hemispheres received stimuli in the processing of which they were not specialized, that is, when verbal stimuli appeared at the left visual field and spatial stimuli at the right visual field. Evidence suggesting a separate oscillatory control of the circadian rhythms of left and right-hemisphere activity is discussed.

Adolescent↗

PubMed1992

Biological significance of iron-related magnetic resonance imaging changes in the brain.

Iron, an essential element for basic cellular metabolism, regularly accumulates in certain brain areas in normal subjects and in patients with certain diseases. Magnetic resonance imaging can depict iron deposition, offering a singular opportunity to correlate the regional iron content with the functional status of the human brain in vivo. We studied the relationship between age and the iron-related signal loss on T2-weighted images in basal ganglia, and observed a strongly significant signal decrease in the globus pallidus at the age of brain development (first two decades of life), but we found no such decrease in later years. Moreover, in healthy adults, subject-to-subject variability was relevant in changes due to iron deposition in magnetic resonance imaging. We found increased signal loss to be associated with poor performance on motor and specific cognitive tasks, suggesting that these image changes can provide functional information with respect to the brain in normal subjects.

Aged↗

PubMed1992

Reduction of the substantia nigra width and motor decline in aging and Parkinson's disease.

We studied the functional significance of the involutional and degenerative changes in the substantia nigra as seen on magnetic resonance imaging. The width of the pars compacta correlated with motor performance in both healthy elderly subjects and idiopathic Parkinson's disease groups. Patients exhibited significant reduction of the width of the pars compacta and the level of this reduction correlated strongly with the clinical status evaluated by the Unified Parkinson's Disease Rating Scale. These results suggest that pars compacta shrinkage may account for a substantial part of the structural substratum of motor decline in the elderly. Moreover, an analysis of the relationship of the midbrain damage with specific symptoms in Parkinson's disease could contribute to a better understanding of the pathogenesis of this degenerative process.

Aged↗

PubMed1992

[Memory changes in Parkinson's disease. Relation with clinical variables].

We studied verbal and visual short term memory, learning capabilities and long term retention in a sample of 96 patients with Parkinson's Disease (PD) and 42 controls matched by sex, age, years of education and verbal intelligence. We found significant differences between groups in visual short term memory and verbal learning, but not in verbal short term memory and long term retention. Performance in visual short term memory and learning correlated with the severity of disease and motor performance. Forty-one per cent of patients had impairment in visual short term memory, and this impairment is related with bradykinesia and correlated with age of onset. These results suggest that two forms of memory failure are closely related to motor symptoms and other clinical variables probably reflecting the same neuropathological substrate.

Aged↗