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Biomedical subjects

T Harmony

Publications and source records attributed to T Harmony.

At least 55 records · Page 3Linked to original sources
PubMed1990

Brainstem evoked potentials in learning disabled children.

Averaged brainstem auditory responses (BAER) were recorded using left and right ear stimulation with clicks of 90 dBs in two groups of primary school children (control and learning disabled). A linear multiple regression model was used in an attempt to demonstrate the effects of sex, high risk factors related to brain damage and learning disability on the evoked responses. Sex showed a strong influence in the latencies of the first five peaks, with girls having shorter latencies. Risk factors had an effect on the latency of peak V, the I-V interval and the V/I amplitude ration, but only when the left ear was stimulated. Learning disability had no significant influence according to this analysis. Multivariate test of complete homogeneity showed highly significant differences between LD and control boys when the left ear was stimulated and between control and LD girls when the right ear was stimulated. Principal component analyses revealed differences between the two groups: the BAER components of the control subjects showed a minor source of variance when the right ear was stimulated. A contrary effect was observed in LD children. Such differences might be related to ear preference and hemispheric dominance.

Acoustic Stimulation↗
PubMed1988

EEG maturation on children with different economic and psychosocial characteristics.

It has been shown that EEG maturation can be described in terms of regression equations on age of broad band EEG frequency parameters. In the present paper six groups of children with different economic and psychosocial characteristics of three countries were studied. Regression equations on age of the EEG relative power (expressed in percentages of the total EEG activity) in the delta, theta, alpha and beta bands in 8 bipolar derivations were computed in each group of children and the slopes compared with those previously published by John et al. (1980). Those children who grew up with adequate nutritional, sanitary and cultural environmental conditions showed the same slopes as U.S. and Swedish children selected with strict criteria of normality. Children nourished in poor socioeconomic and sanitary environments and who frequently had pathological personal antecedents with risk factors associated with brain damage showed either a slow maturation of the EEG characterized by smaller slopes of theta relative power or a great variance of EEG parameters and no relation of these parameters to age.

Child↗
PubMed1988

Effect of different factors on EEG spectral parameters.

We had previously observed that in groups of children with low socioeconomic and cultural level the EEG spectral parameters did not correlate with age due to the great variance in the distribution of such EEG parameters. In this paper we have made several statistical analyses in order to look for other factors that may explain the great variance observed. EEG during rest was recorded in 14 monopolar leads from 119 children. After FFT the following measures were calculated: absolute power, relative power, dominant frequency, coherence and left power/right power ratio for the delta, theta, alpha and beta bands in each derivation. For each measure, in each derivation, ANOVA analyses were performed taking age as covariable and sex, presence or absence of antecedents of risk factors and of learning disorders (LD) as independent variables. Age had its main effect on absolute power in the different bands and in the dominant frequency in the alpha band. Sex affected absolute and relative power in the alpha band. Risk factors per se had no effect. Presence of LD showed its main effect on absolute power. Many interactions between risk and LD and sex and LD were observed. Other analyses, such as MANCOVA, corroborated these results: significant differences between girls and boys, significant differences between children with and without LD and no differences between children with and without antecedents of risk factors.

Adolescent↗
PubMed1987

Electroencephalographic characteristics of children with learning disabilities.

Normal, borderline and abnormal EEG findings were investigated in 122 children with no evidence of active neurological or psychiatric disorder, or perceptual or behavioral alterations. All children had a normal IQ. Sixty-one children had a good academic achievement (Controls) and 61 were considered as learning disabled (LD). The great majority of the children had pathological antecedents considered as risk factors for brain damage. The main findings observed were: Abnormal signs were significantly more frequent in LD than in control children. Atypical high amplitude alpha, and abnormal focal paroxysmal and nonparoxysmal activities were found only in LD children with risk factors. No significant differences in the resting EEG were found between presence or absence of pathological antecedents, or between males and females, when the children were compared as a group against the 4 EEG categories. Paroxysmal reactivity to eye-closure was only observed in children with a pathological history. Excessive response to hyperventilation (Grades II and III) was found significantly more frequently in girls than in boys.

Brain Damage, Chronic↗
PubMed1981

Transcatheter embolization of brain arteriovenous malformations and meningiomas. Evoked responses correlations.

Transcatheter embolization of selective arteries of the carotid and vertebral systems were performed in several patients with brain arteriovenous malformations, angiomas and chemodectomas. All patients were submitted to angiography and electrophysiological examination consisting of a conventional EEG and of visual, auditory and somatosensory evoked responses before and after embolization. Patients with tumors showed a marked decrease of blood flow and tumoral necrosis after embolization, facilitating subsequent surgical procedures. Most patients showed an electrophysiological improvement after embolization, in those regions in which angiography revealed brain decompression resulting from the size reduction of the abnormal tissue. Transcatheter embolization can be very useful in the treatment of brain arteriovenous malformations and intracranial tumors, often facilitating surgical procedures.

Adult↗
PubMed1981

Evoked responses after head trauma.

A neurological examination, routine EEG and a battery of evoked responses (i. e. to a flash, to a checkerboard pattern, to three different tones and to the electrical stimulation of the median nerves) were performed in 14 patients within 24 hours, after one month, six months and a year after head trauma. The results have shown a significant correlation between the number of low R values in the first study and both severeness of the trauma and the clinical evolution a year later. ERs appeared to be - unlike the native EEG - a powerful measure for recommending prophylactic treatment in those traumas which are generally considered to produce slight brain damage, but may provoke a post-traumatic epilepsy and/or great memory deficits. This correlation also shows that bad prognosis may be anticipated in cases with widespread ERs' abnormalities.

Adolescent↗
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.

Explore the source record for details and available documents.

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↗