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T Harmony

Publications and source records attributed to T Harmony.

11 recordsLinked to original sources
PubMed1992

Maturation of the coherence of EEG activity in normal and learning-disabled children.

The age effect on coherence has been studied in control (98) and learning-disabled (LD, 54) school-aged children (from 6.0 to 16.8 years old). The EEG recordings were made at rest in 15 leads, and 105 pairwise combinations for coherence were calculated (each lead was compared with all the rest) for delta, theta, alpha, beta and total frequency bands. A significant increase of coherence with age was found in both groups, with a different pattern of maturation. In the control group, a significant increase with age was found in the coherences between posterior regions and vertex (Cz). A significant decrease with age in the coherence between frontal areas was observed, especially in the theta band. The LD group showed a different pattern: no significant relation with age was found in the coherence between any lead and vertex. A high effect of age on coherence between temporal regions was observed with a predominance of the left side in comparison with the contralateral and the ipsilateral. No decrease in frontal coherence was found: in the same region where the control group showed negative values with age, the LD groups had no age effect. The results obtained are discussed as differences in brain organization, in myelogenesis and synaptogenesis and an explanation of the etiology of LD is proposed.

Adolescent↗
PubMed1992

Visual evoked potentials, attention and mnemonic abilities in children.

We analyzed the correlation between attention and mnemonic processes and different visual evoked potential (VEP) parameters. A group of 34 children between 9 and 13 years old was studied. VEPs were recorded in C3, C4, P3, P4, O1, O2, T5 and T6 with linked ear lobes as reference. Two different types of stimuli were used: flash and checkerboard pattern. The power of VEPs was calculated as the sum of the square amplitude values for different time epochs. Correlation coefficients between left and right homologous VEPs were also computed. A visual selective attention task divided into 5 items of increasing difficulty and the Sternberg paradigm were applied. The performance was automatically evaluated by the computer, giving the number of correct responses (NCR) and other measures of performance. Correlation coefficients between VEP parameters and the scores obtained in the performance of tasks were calculated. It was observed that power in P3, P4, T5, and T6 and the correlation coefficients between central, parietal and temporal VEPs were positively correlated with NCR of both tasks. However, power in O1 and O2 was negatively correlated with NCR.

Adolescent↗
PubMed1990

Effect of sex, psychosocial disadvantages and biological risk factors on EEG maturation.

Broad-band frequency analysis was performed on the EEGs of school-age children in order to study the effects of sex, socioeconomic status (SES) and biological risk factors on EEG maturation. Absolute power and relative power in delta, theta, alpha and beta frequency bands were computed in monopolar recordings from F3, F4, C3, C4, P3, P4, O1, O2, F7, F8, T3, T4, T5 and T6. Total absolute power and power in the delta and theta bands decreased with age, following a quadratic polynomial expression. Relative power followed a linear regression with age. Delta and theta decreased while alpha and beta increased. Sex differences in relative power were observed, possibly related to a pubertal spurt: slopes of regression equations were steeper in girls than in boys. Children from low SES (very low income and/or illiterate mother) had higher values of absolute power and a higher percentage of delta and lower of alpha than children with good SES, suggesting a maturational lag. A group of children with personal antecedents of risk factors associated with brain damage were compared with children without antecedents. The former group had higher values of absolute power. Depending on the severity of the risk, children with more severe antecedents had greater differences from children with no antecedents than children in whom antecedents were considered as slight. Risk antecedents had no effect on relative power.

Age Factors↗
PubMed1978

Visual, auditory and somatosensory evoked responses in patients with cerebrovascular disorders.

A diagnostic evoked response battery, consisting of visual evoked responses to flashes and to a checkerboard pattern, auditory evoked responses to three different tones and somatosensory evoked responses to left, right and bilateral median nerve stimulation, was administered to 20 patients with strokes, and compared with 20 normal control subjects. Recordings were obtained at C3, C4, O1, O2, T3 and T4. Evoked responses were found to be of lower amplitudes and lower amplitudes and lower waveform symmetry (expressed by low correlation coefficients between left and right homologous areas) in the patients than in normal subjects. A discriminant equation with 17 variates was computed to separate the two groups. One patient (5%) and 2 (10%) normal subjects were misclassified. Comparison between patients with left or right lesions showed that somatosensory and auditory evoked responses were very useful for identification of the affected side. Quantitative study of evoked responses to different types of stimuli and sensory modalities provides a sensitive method for the evaluation of brain function in such patients. This technique gives higher accuracy than the routine EEG examination in terms of both the percentage of dectection and the accuracy of localization of the affected side.

Acoustic Stimulation↗
PubMed1977

Neurometrics.

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Aged↗
PubMed1975

Driving activity. A quantitative study.

A comparative study of driving activity between normal subjects and neurological patients was performed. Driving activity was considered as the energy of the visual evoked potentials filtered at the same frequency of stimulation (1, 2, 4, 7, 10, 12 and 15 cps) using a CAT 400 C computer as a digital filter. The hemispheric symmetry of the responses was measured by the Pearson product moment correlation coefficient and the signal energy ratio. Each symmetry measure for every patient was compared with the normal values and considered abnormal when differences were greater than 3 SD from the normal mean. Of 25 patients 14 of them with a normal EEG, 23 presented severe alterations in the symmetry of the filtered visual evoked responses. Each patient showed a peculiar pattern of abnormality. It is concluded that the procedure described is a very powerful method in the discrimination of brain lesions.

Adolescent↗
PubMed1975

Polarity coincidence correlation coefficient and signal energy ratio of the ongoing EEG activity. II. Brain tumors.

The asymmetry of the EEG in 35 patients with brain tumor was analyzed using a special purpose computer which provided two measures: Polarity Coincidence Correlation Coefficient (PCC) and Signal Energy Ration (SER). Significant differences were found between this group and a control group of normal subjects. A discriminant function was calculated using both measures and gave an overall separation accuracy of 87% in the sample studied. It was concluded that the method described offers great utility in routine screening and diagnosis of brain tumors.

Adolescent↗
PubMed1975

Polarity coincidence correlation coefficient and signal energy ratio of the ongoing EEG activity. III. Cerebral vascular lesions.

The EEG symmetry of 65 patients with different kinds of cerebrovascular disorders was analyzed using the Polarity Coincidence Correlation Coefficient (PCC) and the Signal Energy Ratio (SER) measurements. Significant differences were found between the pathology group and a control group of normal subjects for both measures. A discriminant function was applied for both values with an overall accuracy of 80%. It is concluded that since the method does not require an experienced electroencephalographer it may be useful for the diagnosis of cerebrovascular pathology and for screening purposes.

Adolescent↗
PubMedDate not supplied

[Visual somatosensory and auditory evoked potentials in multiple sclerosis].

In a group of 15 patients with multiple sclerosis and in a control group of 20 healthy subjects visual evoked potentials produced with flashes or checkerboard pattern, auditory evoked potentials after stimulation with three different tones, and somatosensory evoked potentials after stimulation of the left, right or both median nerves, and reactions to stroboscopic stimulation at seven different frequencies were investigated. Recording was done with unipolar leads from frontal, central, occipital and temporal regions on the left and right side. In patients with multiple sclerosis the cortical responses to all these stimuli had lower amplitude than in healthy subjects, and the reponses to stroboscopic stimulation were also abnormal in the group of patients. Different clinical signs related to various defects of sensory functions showed a high correlation with electrophysiological anomalies. Non-linear discrimination analysis was carried out using 13 variants (the amplitudes were calculated from peak to peak and correlation coefficients were calculated between identical regions on the left and right side) comparing the group of patients with the control group. Using this method it was possible to establish the correct diagnosis in all cases of multiple sclerosis and 85% of healthy subjects could have been included into the asymptomatic group. Since the methods used in these investigations are easy and can be easily automated the authors think that they could be very useful in the clinical diagnosis of multiple sclerosis.

Acoustic Stimulation↗