Biomedical subjects

Pablo Campo

Publications and source records attributed to Pablo Campo.

15 recordsLinked to original sources

PubMed2006

Magnetoencephalographic parietal delta dipole density in mild cognitive impairment: preliminary results of a method to estimate the risk of developing Alzheimer disease.

BACKGROUND: Subjects with mild cognitive impairment (MCI) are at a higher risk of experiencing Alzheimer disease (AD). Magnetoencephalographic temporoparietal dipole densities of low-frequency activity are good predictors of individuals' cognitive status, and might be a useful tool to investigate the conversion from MCI to AD. OBJECTIVE: To investigate the role of low-frequency dipole densities as predictors of the risk of developing AD. DESIGN: Whole-head magnetoencephalographic recordings were obtained from 19 probable AD patients, 17 MCI patients, and 17 healthy control subjects. The generators of focal magnetic slow waves were located using a single moving dipole model. RESULTS: Left parietal delta dipole density permitted a reliable classification of AD and MCI patients. The MCI patients were divided into 2 groups based on the median left parietal delta dipole density, and were followed up for 2 years. The estimated relative risk of conversion to AD was increased by 350% in those MCI patients with high left parietal delta dipole density scores. CONCLUSIONS: Results confirmed the important role of parietal delta dipole density in the evaluation of AD and MCI. A magnetoencephalographic-based assessment of AD and MCI patients might be considered a useful clinical test in the near future.

Aged↗

PubMed2005

Brain dynamics of Arabic reading: a magnetoencephalographic study.

Arabic writing differs greatly from western scripts. To evaluate the influence of written Arabic on the pattern of language-related brain activation, a group of native Arab speakers and a control group of native Spanish speakers were scanned with magnetoencephalography during a reading task. In both groups, brain activity was strongly left lateralized during the time window between 200 and 500 ms after stimulus onset. During late latencies (beyond 500 ms), however, the right and the left hemispheres reached a similar activation level in the Arabic but not in the Spanish group. This suggests a time-dependent role of both hemispheres during Arabic language reading.

Adult↗

PubMed2005

Shifting-related brain magnetic activity in attention-deficit/hyperactivity disorder.

BACKGROUND: Current theories suggest a role for frontal-striatal circuits in the pathogenesis of attention-deficit/hyperactivity disorder (ADHD). METHODS: We used magnetoencephalography (MEG) to measure event-related brain activity during a simplified version of the Wisconsin Card Sorting Test in children with DSM-IV combined type ADHD (ADHD-C) or predominantly inattentive type ADHD (ADHD-PI) and in age- and intelligence-matched control children. RESULTS: In control children, set-shifting cues evoked a higher degree of activation in the medial temporal lobe (MTL) between 200 and 300 msec than non-shifting cues, with MTL activation predicting later activity in left anterior cingulate cortex (ACC) (at 400-500 msec). This MTL-ACC response pattern was diminished in children with ADHD. By contrast, children with ADHD showed early activity in regions barely activated in control children, such as left inferior parietal lobe and posterior superior temporal gyrus. CONCLUSIONS: These preliminary data support theories of frontal dysfunction in ADHD but also suggest that deficits in higher-level functions might be secondary to disruptions in earlier limbic processes.

Adolescent↗

PubMed2005

Proton magnetic resonance spectroscopy and magnetoencephalographic estimation of delta dipole density: a combination of techniques that may contribute to the diagnosis of Alzheimer's disease.

Whole-head magnetoencephalographic recordings were obtained from 10 patients with Alzheimer's disease (AD) and 10 healthy controls in a resting position. Spectroscopic examinations were performed by means of a 1.5-tesla whole-body scanner in the temporoparietal regions of both hemispheres. The relationship between (1)H-MRS-based and magnetoencephalography (MEG)-based measures and their conjoined capability to improve the diagnosis of AD were investigated in this study. Logistic regression analyses were performed. Three separated logistic models were calculated for (1)H-MRS-based metabolites, low-frequency magnetic activity, and the combination of both measures. A combined myoinositol/N-acetyl aspartate (mI/NAA)-delta dipole density (DD) model predicted the diagnosis with 90% sensitivity and 100% specificity. Additionally, the combination of temporoparietal mI/NAA and delta DD values explained the variability of individuals' cognitive status. The results support the notion that a multidisciplinary approach may improve the understanding and diagnosis of AD.

Acetylglucosamine↗

PubMed2005

Could activity in anterior frontal regions predict performance on declarative memory tests?

Few studies have tested the correlation between traditional declarative memory scores and functional brain imaging measures of memory. We examined the predictable capabilities of magnetoencephalography-derived measures, scanned during a high-load encoding-memory task, in the immediate (LM-1) and delayed (LM-2) recall from the Wechsler memory scale. The number of activity sources on the left frontal pole (between 300 and 600 ms) predicted scores in LM-1 and LM-2. Collapsing the activity in the left frontal pole and the orbitofrontal cortex increased the goodness of the solution for the LM-2 scores. The fact that rostral-frontal measures achieved significant values highlights the importance of executive processes, such as the implementation of memory strategies and top-down control mechanisms, in the performance of high-load memory tasks.

Adult↗

PubMed2005

Is medial temporal lobe activation specific for encoding long-term memories?

Several neuroimaging studies have consistently demonstrated the critical involvement of prefrontal cortices and medial temporal lobes during long-term encoding. While the contribution of prefrontal lobes to working memory is well established, the role of the MTL structures remains controversial. To address this issue, we registered the neuromagnetic brain patterns of eight adult volunteers while they performed two working memory tasks (verbal and spatial) using magnetoencephalography (MEG). MEG recordings can provide real-time measures of brain activity, thus allowing detailed tracking of the time-course of brain activation during the encoding phase. We detected sustained and material-specific activity on the MTLs during the encoding phase of a working memory task, based on verbal and spatial information. Two peaks of activation were noted in the left MTL during word encoding in two non-consecutive time periods (500-600 ms and 700-800 ms after stimulus onset). Right MTL laterality was found for encoding locations when we collapsed activity sources in a wider time period (400-800 ms). In addition, we provided the spatiotemporal profiles of what seems to be two different brain circuits specific for each type of material. Finally, following an emerging conceptualization of working memory, we hypothesized that encoding processes mediated by the MTL to long-term memory would also apply to working memory.

Adult↗

PubMed2005

Prefrontal brain magnetic activity: effects of memory task demands.

Changes in spatiotemporal profiles of brain magnetic activity were investigated in healthy volunteers as a function of varying demands for phonological storage of spoken pseudowords. Greater activity for the phonological memory task was restricted to the dorsolateral prefrontal cortex (DLPFC) in the left hemisphere. During performance of the memory task, activity was initially found in the left superior temporal gyrus (between 100 and 200 ms), followed by activity in the ventrolateral prefrontal, motor, and premotor cortices (between 200 and 300 ms). Activity in DLPFCs was first observed consistently across participants later, between 300 and 400 ms. The data are consistent with the purported role of posterior temporal cortices in phonological analysis and in the online storage of phonological information, the contribution of ventrolateral and motor processing areas in establishment and short-term maintenance of articulatory representations through rehearsal, and the role of DLPFCs in the executive control of the maintenance operation.

Acoustic Stimulation↗

PubMed2005

Activity in human medial temporal lobe associated with encoding process in spatial working memory revealed by magnetoencephalography.

Animal studies have suggested that working memory may be affected after lesions in the medial temporal lobe, although this assumption has not been corroborated by neuropsychological studies in humans. However, very recently, several functional neuroimaging studies in humans have successfully observed activation of the medial temporal lobe during working memory tasks. The main aim of this study was to investigate the contribution of the medial temporal lobe to the encoding process in spatial working memory. To address this issue we registered the neuromagnetic brain patterns of eight adult volunteers while they performed a spatial working memory task and more perceptual task using identical stimuli. After a initial phase (between 200 and 400 ms) without differences in activation, the medial temporal lobe showed a sustained activity, more evident in the right hemisphere, lasting up to 800 ms during the encoding stage of the spatial working memory task, while the activation in the perceptual task terminated earlier (approximately 400 ms after stimulus onset). The finding of a continued activation of the medial temporal lobe strongly suggests the contribution of this brain region to encoding operations in working memory.

Adult↗

PubMed2004

Time modulated prefrontal and parietal activity during the maintenance of integrated information as revealed by magnetoencephalography.

Using magnetoencephalography, we investigated the spatiotemporal patterns of brain magnetic activity responsible for maintaining verbal and spatial information in either an integrated or an unintegrated fashion. Considering time dimension, we noted a greater activation of a fronto-parietal network in early latencies during the maintenance of integrated information, and a different pattern during the maintenance of unintegrated material, showing a greater activation in a fronto-posterior network in late latencies. The greater activation found in certain areas which are traditionally reported as being engaged in spatial working memory (i.e. superior frontal gyri, dorsolateral prefrontal cortex, superior and inferior parietal lobes) when subjects maintained integrated information could be explained by a greater weight of the spatial dimension. It is as if words somehow acquired a spatial attribute, thus exerting a greater load in a neural network specialized in spatial working memory. Alternatively, and not mutually exclusive, we also propose that during the maintenance of integrated information the allocation of cognitive resources is less interfering than during the maintenance of unintegrated information, making it easier.

Adult↗

PubMed2004

Time-modulated enhancing of the fronto-parietal circuits in the very-old elders.

Several studies have shown that memory circuits can be reorganised as a function of age. Brain magnetic activity evoked by a memory task was recorded in 19 healthy elderly subjects divided into two groups, a young-elder group (mean age of 62) and senior-elder group (mean age of 76). The young-elder group showed greater activity over the left medial temporal lobe in the late latency windows (between 400 and 800 ms) than the senior-elder group. The senior-elder group showed an initial increased activity (between 150 and 400 ms) over the complex of motor areas, followed by an increased activity in the left temporo-parietal cortex at the late latency window. These results revealed a reorganization of brain networks supporting memory in the eldest subjects. Furthermore, these circuits are reorganised in a time-dependent manner, meaning the rehearsal articulatory process active in the early time window followed by a phonological storage and recognition process in the late latency window.

Aged↗

PubMed2004

Normative data and reliability for a Spanish version of the verbal Selective Reminding Test.

The purpose of this paper was to extend the use of the verbal Selective Reminding Test to the Spanish-speaking population. Since valid and reliable tests, with appropriate norms are essential for an adequate assessment of cognitive functioning, in this study we provide normative data collected from 329 Spanish-speaking individuals for a Spanish version of the test. Age, gender and education effects were analyzed. In addition, the reliability of the test was also investigated. The adequacy of these norms to people from other Spanish-speaking countries is discussed. In addition to the measures typically reported, we have included three new indices.

Adolescent↗

PubMed2003

Modulation of brain magnetic activity by different verbal learning strategies.

In this study we examined spatiotemporal profiles of brain activity in the context of tasks designed to engage different verbal learning strategies (serial order, phonological, and semantic). The profile of activation associated with the serial-order strategy, which resulted in poor recall performance, featured early activation of the inferior frontal, sensorimotor, and insular region in the left hemisphere, between 200 and 400 ms after stimulus onset. Subsequently, activation was more prominent in dorsolateral prefrontal cortices bilaterally. In contrast, activation profiles associated with the phonological strategy featured predominantly activation of the superior temporal gyrus in the left hemisphere between 500 and 600 ms. Predominant activation of the left middle temporal gyrus, between 500 and 700 ms, was the key feature of the activation profile observed when the semantic elaboration strategy was utilized. These results suggest that different brain circuits are engaged to support learning of new verbal information as a function of the level and type of initial processing applied to the stimuli.

Adult↗

PubMed2003

Reliability and normative data for the Benton Visual Form Discrimination Test.

Visuoperceptual disorders are a common consequence of brain disease. The Visual Form Discrimination Test is a task designed to assess the ability to make fine visual discriminations. Although its validity to assess the visuoperceptual impairments in patients with different neurological conditions has been well established, the normative data base for the test has remained small. The clinical use of the test has been limited by the scanty normative data available. Thus, with the aim of assisting the clinicians in interpreting more accurately the performances of their patients we investigated the test-retest reliability of the Benton's VFDT and also provide normative data obtained on a sample of 397 healthy individuals.

Adolescent↗

PubMed2003

Discrimination of normal from demented elderly on a Spanish version of the verbal Selective Reminding Test.

The verbal Selective Reminding Test (vSRT) is a frequently used test for evaluating verbal learning and memory. In the present study we investigated the construct validity of a Spanish version of the vSRT by determining its ability to distinguish between a group of healthy elderly subjects and a group of patients with dementia of the Alzheimer type (DAT). Further validation of the test was assessed by comparing the pattern of memory deficits found in the group of patients with DAT with findings from previous neuropsychological research concerning with memory impairments in English-speaking patients with Alzheimer's disease. Analyses revealed that the test was able to differentiate normal individuals from patients with DAT. In addition the pattern of memory functioning found in the group of patients with DAT was consistent with findings of previous experimental and clinical reports. These results support the construct validity of the Spanish version of the vSRT.

Aged↗

PubMedDate not supplied

Dipole density of low-frequency and spike magnetic activity: a reliable procedure in presurgical evaluation of temporal lobe epilepsy.

Conventional visual analysis and dipole density analysis of magnetoencephalographic data for both spike and low-frequency magnetic activity were compared for presurgical evaluation in temporal lobe epilepsy (TLE) in a sample of 26 drug-resistant operated TLE patients. A series of logistic regression analyses were performed. Dipole density sensitivity was superior to visual localization analysis. Three separated logistic models were calculated for interictal spikes, low-frequency magnetic activity, and the combination of both measures. A combined interictal spike/low-frequency magnetic activity model predicted correctly the operated temporal lobe in all patients. Clear-cut criteria for the probability model are proposed that are valid for 92.3% of cases in the sample. The quantitative approach proposed by this study is an evidence-based model for presurgical evaluation of temporal lobe epilepsy, which improves previous magnetoencephalographic investigations and establishes working clinical criteria for patient evaluation in TLE.

Adolescent↗