[Evoked potentials in a population of children below 1,500 grams at birth: a description and probabilities]. / Potenciales evocados en una población de niños menores de 1.500 gramos: descripción y probabilidades.

INTRODUCTION: Bioelectrical behaviour was studied in a group of low birth weight children. AIM: To evaluate whether the characteristics of the waves of the brain potentials in these children, who weighed less than 1500 g at birth and experienced anomalous circumstances and events during their perinatal period, would help reach an early diagnosis of the possible developmental disorders they might suffer later on in life. SUBJECTS AND METHODS: Both visual and auditory cerebral evoked potentials were recorded in a group of children born underweight and the results were compared with the findings from another group of healthy children who were born in normal physiological conditions and were apparently free of any kind of pathology. RESULTS: In the waves and locations that were examined, the problem group displayed latencies that were longer than those of the control group; in contrast, no statistically significant differences were found in the amplitude, regardless of the location. Low gestational age and lower weight made latencies longer, but no relationship was found between latencies and the other perinatal features that were studied. CONCLUSIONS: Children with low weight at birth have slower wave latencies than normal children. This slowing, which is inversely proportional to the weight and weeks of gestation, is considered to be an anomalous sign that could be related to brain immaturity, delayed development or to disorders affecting myelination. Moreover, the amplitude, which has received far less attention from researchers, is usually shorter in these processes, although in our study we found no differences with the group of healthy children--only very slightly in the P300, in the weeks and the weight, and the N100 only in one location with respect to weight. Since these children usually have developmental disorders, the use of evoked potentials could be a very useful tool in their detection and ensuing therapy.

[A study of evoked potentials in the brains of very low birth weight infants]. / Estudio de potenciales evocados cerebrales en niños de muy bajo peso al nacimiento.

INTRODUCTION: This work studies the behaviour of the N200 and P300 waves of the brain evoked potentials (BEP) in a group of very low birth weight infants and results are compared with a second group of children whose weight was normal at birth. AIMS: The objective of this study was to determine whether the N200 and, more especially, the P300 waves in children under the age of 3 could be used to assess the development and prognosis of their disorders. PATIENTS AND METHODS: BEP were performed in very low birth weight infants (taken as the test group) and in others whose weight at birth was normal (control group); the difference in ages when the potentials were recorded was not statistically significant. RESULTS: The EEG index was evaluated for both the test and the control group, and a difference was found with a significance of p < 0.001. Latency, in milliseconds, of the N200 wave and the P300 wave was recorded at the same sites for the test and control groups and showed differences with a significance of p < 0.001. CONCLUSIONS: The findings from the EEG and the latencies of the N200 and P300 waves in the BEP of very low birth weight infants are pathological and are linked to immaturity of the brain, which is characteristic of this population. This tool could help to detect developmental disorders and to facilitate a better approach to attending these children.

[Deficit of cognitive event-related potentials during a working task in patients with major depression]. / Déficit de los potenciales evocados cognitivos durante una tarea de memoria en pacientes con depresión mayor.

INTRODUCTION: To study working memory function in major depression using identification and memory tests with event-related potentials (ERP). METHODS: We compared behavioral performance and event-related potentials during the processing of the Sternberg working memory task in 26 patients with major depression and 64 healthy matched control subjects. RESULTS: Depressed patients had more errors and had an increase in reaction time that was superior to the control subjects during the memory test of 5 letters presented. The depressive patients showed increased event-related potentials (P300 and N400) between 300-700 milliseconds registered in Pz. The prolonged positive activity in the patients ERPs suggests specific deficit in cortical activity and the large prolonged negativity activity in the patients' ERPs suggests abnormal activation of additional neuronal assemblies than those normally participating in the memory task. These data could reflect either compensatory mechanisms of dysfunction of inhibitory systems. CONCLUSIONS: This study provides objective evidence that major depression significantly affects working memory. The ERP changes in depression could be accounted for by cortical activity dysfunction of the central executive control of working memory.

[P300 clinical utility in major depression]. / Utilidad clínica de la P300 en pacientes con depresión mayor.

INTRODUCTION: Event related potentials are an objective parameter reflecting cognitive functions. Among the event related potentials, the P300 component is viewed as a measure of stimulus evaluation time and it can provide a rough estimate of the time required for perceptual processing. Impairment in cognitive processing, psychomotor retardation and abnormally amplitude and longer P300 latency have been found in depressive patients. METHODS: To evaluate the influence of visual and auditory stimuli on the P300 latency we studied 595 patients with major depression. The experimental tasks applied were, first, a series of 300 auditory stimuli: 85% were tones of 1,000 Hz, and 15% were tones of 2,000 Hz, and second, a series of 300 visual stimuli; 85% were black circles on a white background and 15% were black squares on a white background. RESULTS: The results shown an increase of P300 latency in depressive patients during auditory and visual tasks. DISCUSSION: These results are consistent with an impairment in brain function with cortical hypo activity in depressive patients that is associated with cognitive deficit processing. These results determine the clinical utility of P300 in patients with major depression.

[Cortical processing of visual and auditory stimuli in depressive patients: a study with event related potentials]. / Procesamiento cortical e estímulos visuales y auditivos en pacientes depresivos: estudio mediante potenciales evocados.

Event related Potentials, which seem to be an objective parameter reflecting cognitive functions, have been examined in depression. To evaluate the influence of visual and auditory stimuli on the P300 latency we studied 42 patients with major depression and 21 normal subjects. The experimental tasks applied were first a series of 300 auditory stimuli [255 (85%) were tones of 1000 Hz, and considered the frequent stimulus, whereas 45 (15%) were tones of 2000 Hz and referred to as the rare stimulus and second a series of 300 visual stimuli 255 (85%) were black circles on a white background, and considered the frequent stimulus, 9 cm diameter, 200 ms duration whereas 45 (15%) were back squares on a white background and referred to as the rare stimulus, 9 cm diameter, 200 ms duration] in the center of a computer screen. The results shown an increase of P300 latency in depressive patients during auditory and visual tasks. Non differences were found in reaction time to visual or auditory stimuli. These results are consistent with an impairment in brain function in depressive patients that is associated with cortical hypoactivity and deficits in perceptive, auditory or visual, functions.

Associated EMG responses to voluntary hand movement in probable Alzheimer's disease.

The goal of this work is to dilucidate the mechanism that yields the associated EMG responses in patients with probable Alzheimer's disease. Seventeen subjects fulfilling this criteria and ten normal subjects as a control group were selected. They were asked to perform an oddball task in which they had to discriminate between two kinds of stimuli and produce a response to one of them. Results show that reaction times in controls and in patients when there is no associated EMG are equal in latency. When the associated EMG response occurs in the pathological group reaction time is significantly increased. Furthermore, the associated EMG response is delayed in 55 milliseconds when compared to the voluntary movement. Although these results may reflect some controversy, we interpret this finding as a contralateral inhibitory deficit associated to the corpus callosum abnormalities that occur in the evolving course of Alzheimer's disease.