Biomedical subjects

D Zarabozo

Publications and source records attributed to D Zarabozo.

7 recordsLinked to original sources

PubMed2003

POTENCOR: a program to calculate power and correlation spectra of EEG signals.

This work describes a computer program (POTENCOR) that applying the Fast Fourier Transform and Pearson product-moment correlation, can calculate easily, fast and accurately the absolute and relative power as well as the inter- and intrahemispheric correlation between every pair of EEG signals for narrow bands and for broad bands. POTENCOR has three main advantages: (1) it allows calculation of inter- and intrahemispheric correlation spectra, for which to our knowledge, there is no commercial program available; (2) the absolute and relative power values are not affected by the number of points that constitutes the signal segment; and (3) in case of making the analysis by each segment the temporal evolution for each EEG parameter can be graphically represented. The utility and flexibility of this program has been confirmed in many clinical and experimental researches.

Computers↗

PubMed2001

Event-related brain potentials in normal children during detection of inverse serial digits.

Three inverse serial digit detection tasks were evaluated with event-related brain potentials (ERPs) in 15 11-year-old children to determine how the increase of perceptual or memory demands could modify detection processing. Reaction times were significantly longer for the task that used visual blurring, compared to that with a greater memory demand. Difference-ERPs (target minus non-target conditions) showed three significant parietal components; one earlier positive peak at 162 ms interpreted as an index of working memory load; a same polarity 295 ms peak which probably represents a P3 analogous and a subsequent negative polarity component (520 ms) possibly involved with motor preparation. A fourth difference-component was a frontal positive peak at 680 ms, interpreted as related to task difficulty.

Cerebral Cortex↗

PubMed2000

Does literacy have an effect on stick construction tasks?

Since constructional apraxia is often concomitant with brain lesions, the study of constructional tasks in the non-brain-damaged population might be useful in helping to disentangle other causal factors. This paper explores the performance of illiterate individuals (N = 29) as compared to that of semiliterates (N = 21) and literates (N = 23) in order to see the effect of reading and writing abilities on constructional tasks. Each participant was asked to construct 4 figures based upon models having varying degrees of complexity. A global criterion of lack of fidelity and several analytic criteria (related to distortion, rotation, and disarticulation errors) were used to evaluate performance. Although illiterates generally made more errors than semiliterates and semiliterates more than literates, only some of these differences were statistically significant. Significant differences were found for lack of global fidelity and disarticulation errors when all 4 figures were considered together. Subtler data emerged with respect to single figures.

Adolescent↗

PubMed2000

Coherence in short narratives written by Spanish-speaking children with reading disabilities.

A novel analysis of coherence using a combination of three criteria (syntactic connexity, pragmatic complexity, and rhetorical well-roundedness) was applied to short narratives produced by a group of 60 Spanish-speaking children of different ages and grades with reading disabilities and compared to those produced by normal children. We posit a scale of 6 degrees of increasing coherence. This feature of children's writing, together with 2 others (viz. number of propositions, or "story points," recovered and number of words employed), was compared to features of children's reading by means of discriminant analysis in relation to age. We show that the combination of age, words read per minute, and degree of coherence achieved an optimal discrimination of the 2 groups.

Adolescent↗

PubMed1987

Neuroelectric correlates of a neuropsychological model of word decoding and semantic processing in normal children.

The use of event-related potentials (ERPS) as a technique in the study of word decoding and semantic processing in the cerebral cortex was investigated. Ten right-handed boys, aged between nine and eleven, with adequate school performance were studied. Visual ERPS were obtained using four derivations: occipital (O1-O2) and parietal (P3-P4). Four stimuli were presented: a frequently used noun written in capitals; the same noun in handwriting; the pictorial representation of this noun (drawing); and a pattern consisting of a checkerboard (25 squares). The data were analyzed using multivariate procedures. A Principal Component Analysis with varimax rotation of the solution was applied. Concepts about reading contributed by cognitive psychology, neuropsychology and neurophysiological research are reviewed, and a hypothetical model of the neuronal bases underlying the act of reading is presented. This model emphasizes the complex, dynamic interplay of the neural structures involved and points to the differences which probably exist between beginning and fluent readers. The results are discussed in accordance with the proposed model.

Brain↗

PubMed1987

Neuroelectric correlates of a neuropsychological model of word decoding and semantic processing in reading disabled children.

The purpose of this study was to distinguish the characteristics and components of event related potentials (ERPs) correlated with word decoding and semantic processing in a subgroup of children with specific reading disabilities related to visual processing deficiencies. The results were compared with those obtained from a group of normal readers previously studied (Ostrosky et al. in press). Visual ERPs were recorded to four stimuli: three physically different but with the same semantic content: a frequently used noun written in capitals (COCHE), the same noun in handwriting, the pictorial representation of the noun (drawing), and a neutral stimulus consisting of a checkerboard. Four derivations were used: occipital (O1-O2) and parietal (P3-P4) with reference to linked mastoids. Data were analyzed using multivariate procedures. A Principal Component Analysis with Varimax rotation of the solution was applied. In the normal readers, we found some components in the occipital derivations which identified the words presented in different styles of handwriting and others which seemed to identify these words with the pictorial representation (and not with the neutral stimuli). The first "verbal" components were situated around the 156-256 ms latency range and the second "semantic" components were observed at over 380 ms. In the disabled readers, there was no "verbal" or "semantic" recognition grouping of these physically different stimuli. As opposed to the normal readers, interhemispheric responses were symmetrical. At the left parietal leads in the normal readers, the morphology of the verbal stimuli (capitals and handwriting) were very similar throughout the sweep and both were very different from the nonverbal stimuli. At 376 ms the four stimuli elicited a prominent negative peak in which the verbal stimuli elicited significantly higher amplitude than the nonverbal stimuli. In the disabled group, the morphologies of the four stimuli were very similar and no significant differences were observed. The results are discussed in accordance with a hypothetical model of the neural bases underlying reading. The model takes into account the complexity of the reading process and the various cognitive skills required for its adequate performance, and emphasizes a complex, dynamic interplay between occipital, parietal and temporal areas.

Cerebral Cortex↗

PubMed1979

Petit mal and grand mal seizures produced by toluene or benzene intoxication in the cat.

Motor incoordination, euphoria and hallucinations are symptoms reported for humans voluntarily intoxicated by industrial solvents. An epileptic-like consciousness impairment has also been noted. The present paper describes a technique used for the experimental study of solvent intoxication in which toluene and benzene can be applied directly into the trachea of freely moving cats with chronically implanted electrodes. This technique permits the control of solvent dose and time of exposure. Results showed a 3 Hz spike-wave activity in the gyrus cinguli recording with both toluene or benzene intoxication. Furthermore, benzene inhalation produced generalized tonic-clonic seizures. These effects were dose-related. However, a sensitization period was essential for the development of such alterations, and effects showed a tendency to shortening through chronic exposures. These alterations were correlated with behavioral disturbances such as nodding, twitching and apparent hallucinations. Results are discussed regarding the sensitization period, the optimal peak of effects, and the period of tolerance development relevant to an earlier found amygdalar activation that could be correlated with other methods inducing experimental seizures, such as repetitive stimulation of the brain (kindling).

Amygdala↗