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Biomedical subjects

J R Valdizán

Publications and source records attributed to J R Valdizán.

At least 19 recordsLinked to original sources
PubMed2005

[Cognitive evoked potentials in face recognition in autism].

INTRODUCTION AND DEVELOPMENT: Face recognition requires a special type of processing that is different to that used to recognise objects. The right medial region of the fusiform gyrus displays a higher degree of activation when dealing with faces, which is why it is known as the fusiform face area, although the integrity of the right occipital face area may be needed to perform this task. Neuroimaging studies point not only to the existence of normal activation of the fusiform face area in response to faces but also of the occipital area. One modulation that supports the existence of a specific pathway is the face inversion effect, which is defined as the process in which greater disability is displayed in the recognition of inverted faces than for other mono-oriented objects. The P1 potential is the initial endogenic component of visual processing, acting as an index of the processing of features that show lower latency and greater amplitude when dealing with a face stimulus than when stimulated by objects. A later response, the negative component N170, also has lower latency in the case of faces than in inversion and objects. Its amplitude increases when the faces are inverted due to the generation of a greater activation in the region where it originates. A later negative potential can be associated to semantic identification in face recognition. The N170 waves in autistic individuals display greater latency with faces that is similar to the response to objects and, in turn, show no differences in the latencies with inverted faces. It remains to be shown whether they have an N400 response to faces. CONCLUSIONS: Cognitive evoked potentials allow us to evaluate face recognition both in normal and autistic individuals by presenting responses to specific stimuli. Further studies will enable us to determine whether an N400 response exists in individuals with autism.

Autistic Disorder↗
PubMed2000

[Why evidence-based medicine? 20 years of meta-analysis].

BACKGROUND: Meta-analysis, described within evidence-based medicine, has become a frequent issue in recent medical literature. An exhaustive search of reported meta-analysis from any medical specialty is described. MATERIAL AND METHODS: Search of papers included in Medline or Embase between 1973-1998. A study of intra and inter-reviewers liability about selection and classification have been performed. A descriptive analysis of the reported papers (frequency tables and graphics) is described, including differences of mean of reported meta-analysis papers by medical specialty and year. RESULTS: 1,518 papers were selected and classified. Most frequently found (45.91%) were: methodology (15.7%), psychiatry (11.79%), cardiology (10.01%) and oncology (8.36%). Inter personal agreement was 0.93 in selecting papers and 0.72 in classifying them. Between 1977-1987 overall mean of reported studies of meta-analysis (1.67 + 4.10) was significatively inferior to the 1988-1998 (49.54 + 56.55) (p < 0.001). Global number of meta-analysis was positively correlated (p < 0.05) with the number of studies about fundamentals and methodology during the study period. CONCLUSIONS: The method used to identify meta-analysis reports can be considered to be adequate; however, the agreement in classifying them in medical specialties was inferior. A progressive increase in the number of reported meta-analysis since 1977 can be demonstrated. Specialties with a greater number of meta-analysis published in the literature were: psychiatry, oncology and cardiology. Diffusion of knowledge about fundamentals and methodology of meta-analysis seems to have drawn and increase in performing and reporting this kind of analysis.

Evidence-Based Medicine↗
PubMed1998

Auditory event-related potentials to semantic priming during sleep.

The present study uses the N400 component of event-related potentials (ERPs) as a processing marker of single spoken words presented during sleep. Thirteen healthy volunteers participated in the study. The auditory ERPs were registered in response to a semantic priming paradigm made up of pairs of words (50% related, 50% unrelated) presented in the waking state and during sleep stages II, III-IV and REM. The amplitude, latency and scalp distribution parameters of the negativity observed during stage II and the REM stage were contrasted with the results obtained in the waking state. The 'N400-like' effect elicited in these stages of sleep showed a mean amplitude for pairs of unrelated words significantly greater than for related pairs and an increment of latency. These results suggest that during these sleep stages a semantic priming effect is maintained actively although the lexical processing time increases.

Adult↗
PubMed1998

[Topographic distribution of visual evoked potentials in optic neuropathy].

INTRODUCTION: Digital treatment of electrical signals coming from the central nervous system on stimulation of the optic nerve path offers an objective method for evaluation of visual evoked potentials (VEP) shown graphically on a cerebral map. OBJECTIVE: To evaluate the topographical distribution of VEP in cases of optic neuropathy adding this parameter to the usual parameters of latency and amplitude. MATERIAL AND METHODS: We studied 35 patients with suspected optic neuropathy and normal findings on basic ophthalmological examination, in whom VEP and VEP mapping (VEPM) was done. RESULTS: In 26% of the cases there was no response for evaluation with the usual VEP recording techniques, whilst in those with VEPM this percentage was reduced to 11.5%. In the other cases there was a potential with characteristic distribution in the occipital areas and a maximally positive dipole posteriorly. CONCLUSION: VEPM is an objective method for evaluation of the visual pathway offering better discrimination than the usual VEP in more severe cases of neuropathy.

Adolescent↗
PubMed1997

[Cortical variations of the dimension of correlation in children with attention deficit hyperactivity syndrome].

INTRODUCTION AND OBJECTIVE: The syndrome of deficient attention and hyperactivity affects approximately 5% of children of school age. Clinically it is characterized by deficient attention, impulsiveness and excessive motor activity. Developments in nonlinear dynamic theory have made it possible to think of modelling cerebral activity as a dynamic system of chaotic type. One the most widely standardized measurements is the dimension of correlation (D2). In this paper we study the electroencephalographic traces of a control group of 9 healthy children and another group of 19 children with the syndrome of deficient attention, at rest and whilst carrying out a visuomotor task (Test of perception of differences). MATERIAL AND METHODS: The dimension of correlation was estimated for both groups. Statistical comparison was made between the cortical distributions of the D2 between both types of recordings and between both groups. RESULTS: The children with lack of attention showed a larger number of activated cortical areas than those of the control group when carrying out the same task. However, during the resting state there were no differences in the D2 between the control children and the children with deficient attention. The indicates that both groups have the same basal level of activation. CONCLUSION: The dimension of correlation is a method which permits the demonstration of an increase in neuronal activity in the stimulated areas, in this case in the occipital region.

Adolescent↗
PubMed1994

Quantitative EEG in children with headache.

The object of this work is to determine if Brain Mapping can reveal significant differences between a normal control group and a group whose members suffer from one of three types of headache: tension-type, migraine with aura and migraine without aura. Both groups were formed by children aged between 6 and 14; the latter were undergoing no treatment and were in a headache-free phase. Results demonstrate that there are no significant differences between the control group and the tension-type headache group. Neither were differences found in migraine without aura group but in migraine with aura there was an increase of the theta/alpha ratio in the temporal posterior and occipital zones. This ratio could be used as a neurophysiological indicator in the evolution of the migraine with aura pathology.

Adolescent↗
PubMed1993

Test of repeated operations and logistic regression as to the efficacy of brain mapping.

The object of this paper is to apply two new methods, those of repeated observations and logistic regression in order to verify the validity of qEEG. These methods are applied using children with hyperactivity and attentional disorders, according to DSM III-R. The results of sensitivity and specificity were similar.

Attention Deficit Disorder with Hyperactivity↗
PubMed1992

Nocturnal prolactin and growth hormone levels in children with complex partial and generalized tonic-clonic seizures.

This study measures whether there is a rise in the secretion of nocturnal prolactin and growth hormone (GH), during the delta phase of the first sleep cycle in children who are suffering from either complex partial or generalized tonic-clonic seizures. The findings are compared with those obtained in the control group of patients which is made up who suffer from pseudoseizures. There is a moderate but significant rise in the nocturnal prolactin plasma level in both types of infantile seizures. No significant difference was found in the GH.

Child↗
PubMedDate not supplied

[P300 and auditory information processing during natural sleep].

INTRODUCTION: The P300 is elicited, in the waking state and during an 'attention condition', in response to deviant stimuli of an oddball paradigm. This component of event related potentials (ERP) may be a useful research tool in the assessing of cortical sensory processing during normal sleep since a subject does not need to be awake or totally conscious in order to generate a measurable response. OBJECTIVE: This study used an classical oddball paradigm as a means to assess the auditory information processing during sleep. PATIENTS AND METHODS: The auditory ERP were registered in twelve healthy volunteers during the waking state and sleep stages II, III-IV and REM. The amplitude, latency and scalp distribution parameters of the positivity observed were contrasted with the results obtained in the waking state. RESULTS: A 'P300-like' with a significantly smaller peak amplitude and an increment of latency was elicited during stage II and the REM stage of sleep. As in the waking state, the positivity during this sleep stages was maximal at central-parietal regions. CONCLUSIONS: The response obtained seems to correspond both for the morphology of the potential as for the centro-parietal predominance with a waking P3b component. These results suggest that certain processes of attention and memory-related operations involved in the auditory processing of simple signals remain operative during these sleep stages.

Adult↗
PubMedDate not supplied

[Cortical spectral distribution of infantile electroencephalography in attention disorders].

INTRODUCTION: Sensory and attention disorders cause selective effects on the topographical distribution of electroencephalograph frequencies. OBJECTIVES: In this paper we show changes in spectral topography produced by visual attention tests in a group of healthy children, thus demonstrating the cerebral areas involved in this mental process and the anatomical and bioelectrical organization of the subsystems involved. METHOD: To distinguish the effect due to cognoscitive activity from what is merely a visual sensorial process, firstly we compared resting quantified electroencephalograms with the eyes shut, with those done with the eyes open. Immediately afterwards we evaluated the spectral transformation caused by the test to find the contribution made to the electroencephalogram pattern by intellectual activity, using spectral amplitude analysis as an objective method for the measurement of recordings in a group of 10 children with an average age of 8.85 years. RESULTS AND CONCLUSIONS: The contribution of the cognitive test is seen in an increased beta frequency in the temporal and occipital cortical areas, whilst the maps of cortical distribution show the cerebral areas activated.

Attention↗
PubMedDate not supplied

[Neurological sciences based on evidence].

OBJECTIVE: An exhaustive search of reported metanalysis from any medical speciality is described. MATERIAL AND METHODS: Search of papers included in MEDLINE or EMBASE between 1973-1998. A descriptive analysis of the reported papers (frequency tables and graphics) is described, including differences of mean of reported metanalysis papers by medical speciality and year. RESULTS: 1,514 papers were selected and classified. Between 1977-1987 overall mean of reported studies of neurologic metanalysis (1.20 +/- 1.10) was significatively inferior to the 1988-1998 (11.20 +/- 7.85) (p < 0.001). Global number of neurologic metanalysis was positively correlated (p < 0.05) with the number of studies about fundamentals and methodology during the study period. CONCLUSIONS: A progressive increase in the number of reported neurologic metanalysis since 1977 can be demonstrated. Diffusion of knowledge about fundamentals and methodology of metanalysis seems to have drawn and increase in performing and reporting this kind of analysis.

Evidence-Based Medicine↗
PubMedDate not supplied

[Multiband spectral analysis and standardized markers of the slope of pediatric electroencephalograms].

INTRODUCTION: The infantile electroencephalogram has been studied in connection with many cognitive disabilities. Although normal resting infantile bioelectric recordings are known, the cortical distribution of electroencephalographic frequencies during other sensory and/or cognitive mental processes is less well known. OBJECTIVE: Our interest is based on the description of EEGs of a homogeneous sample of healthy children and their relation to intellectual activities. MATERIAL AND METHODS: The sample studied was made up of 13 healthy children with an average age of 9.3 +/- 1.3 years, on whom two types of tests of attention were done. One of the tasks was a simple auditory memory test and consisted of the spoken repetition of a series of numbers previously heard, which was of variable length. The second test consisted of the identification and crossing out of one face of a series of three faces, which included one which was different from the others. The methodology chosen was electroencephalographic measurement in the frequency and temporal domains. RESULTS AND CONCLUSIONS: There was a relative increase in beta frequencies in all cortical sites which was significant in T3 and T4 with the auditory test and in all electrodes with the visual test. During auditory testing reduction in the alpha frequency was observed in frontotemporal regions. The greatest cortical variations of beta frequency occurred, in the facial test, in the electrodes O2, T6, O1, T5 and T3. The values of Hjorth complexity obtained varied within the interval 1 to 3, which was a considerably lower interval than that found in adult populations.

Attention↗
PubMedDate not supplied

[Pattern electroretinogram in anterior ischemic optic neuropathy].

INTRODUCTION: Anterior ischemia optic neuropathy is defined as ischemia of the disc optic papilla nerve. The aetiology is multifactorial and causes ischemia of the optic disc and apoptosis of the nerve cells of the retina. OBJECTIVE: To study the retina of patients with anterior ischemia optic neuropathy by means of the electroretinogram pattern (PERG) to assess the function of ganglion cells of the inner layers of the retina. PATIENTS AND METHODS: We studied 12 patients referred from the Ophthalmology Department with the diagnosis of anterior ischemia optic neuropathy. The electrophysiological study consisted of PERG and PEV within 20 days of the episode. The latencies and amplitudes of the different components of the responses and the ratios of the PERG amplitudes were determined. RESULTS: No significant differences were seen in the P50 component of the PERG or the latency of the N95 component. However, statistically significant values were obtained for the amplitude N95. These differences were greater when measured from a nonlinear baseline. CONCLUSIONS: The PERG is useful for early diagnosis of patients with anterior ischaemia optic neuropathy. Measurement of the N95 is more useful when a nonlinear baseline is used. This shows dysfunction of the ganglion cells of the inner retina caused by ischaemia and retrograde degeneration of axons and cell bodies of the optic nerve.

Aged↗
PubMedDate not supplied

[Sleep in infantile autism].

INTRODUCTION: Analysis of nocturnal sleep in infantile autism has been presented in various studies. However, there has been no systematization including the different structural and paroxystic alterations at the same time as permitting the development of a general theory of the effect of sleep on prognosis and treatment, particularly in a spectrum in which there is currently no definite solution. DEVELOPMENT: A systematic review was made of the literature obtained from publications included in MEDLINE and web pages of the last 25 years using the key words: autism, Asperger's disorder, sleep, childhood and Rett's syndrome. Altogether 21 papers fulfllled criteria for inclusion. Disorders of sleep in infantile autism were classified into three types: immaturity of sleep, showing a destructured polysomnographic recording and negative correlation with the level of development; functional alterations of sleep with early waking and difficulty in going to sleep being the disorders most frequently seen; and paroxystic alterations with epileptiform discharges being the commonest, without necessarily occurring together with seizures. The opinions stated on questionnaires and the data observed on the polysomnography were not in agreement. CONCLUSIONS: Analysis of the literature has permitted us to make an initial classification of sleep disorders in autistic children, and has shown a marked presence of these disorders in the evolution of autistic children. It is necessary that further studies being done, polysomnographic rather than by means of questionnaires, for two reasons: clinical and in order to obtain more precise classification.

Autistic Disorder↗