Electrical activity of sensory pathways in female and male geriatric Rhesus monkeys (Macaca mulatta), and its relation to oxidative stress.

Synapses loss during aging has been related to decreased neuronal excitability and reduced electrophysiological activity in the nervous system, as well as to increased brain damage. Those physiological and biochemical alterations have been related to the oxidative stress increase associated with old age. The main substrate of lipid peroxidation (LPX) in the central and peripheral nervous systems are the myelin sheaths, and their damage generates a delayed nerve conduction velocity. However, studies in which the neural conduction velocity is related to changes in the redox state are still lacking. Therefore, our aim was to correlate the sensory neural pathways delay in healthy geriatric Rhesus monkeys (Macaca mulatta) with the oxidative stress associated with physiological aging. Twenty-four monkeys were divided into four groups according to age and gender. Auditory, visual, and somatosensory evoked potentials were obtained. Superoxide dismutase, catalase, and glutathione peroxidase enzymatic activity, as well as LPX, were determined from blood samples. Our results showed significant differences between the older and younger age groups in all neural generators of the different sensory pathways evaluated, along with an increase in LPX and the antioxidant enzymatic activities. It suggests that, even though the enzymatic activity was found to be higher in older monkeys, probably as a compensatory effect, it was not enough to avoid LPX damage and the declined electric activity associated with age.

Visual, auditive and somatosensory pathways alterations in geriatric rhesus monkeys (Macaca mulatta).

BACKGROUND: Synapses loss during aging is associated to neurophysiologic alterations that impair organism's health span, thus making the study and prevention of sensory decline relevant for healthy aging and welfare. Therefore the aim of this study was to obtain normative data related to the electrophysiological responses of the different neurosensory components in the visual, auditory and somatosensory pathways in healthy geriatric rhesus monkeys in captivity. METHODS: Twenty-four rhesus monkeys were divided in two groups: (i) Geriatric monkeys, 20-30 years of age, and (ii) Young monkeys, 7 years of age. Evoked potentials were obtained from the visual, auditory and somatosensory pathways. RESULTS: Regardless the sensory pathways evaluated, a significant delay in nerve conduction was observed in the geriatric group in comparison to the young group. CONCLUSIONS: Evoked potentials allowed identifying changes generated during aging in rhesus monkeys and normative data for this species were obtained.

Cefalea y epilepsia como secuelas de un traumatismo craneoencefálico por proyectil de arma de fuego / No disponible

No disponible

Spatial distribution of EEG theta activity as a function of lifetime lead exposure in 9-year-old children.

The relationship between low-level childhood lead exposure and developmental retardation has been proposed but the existing evidence is weak. We examined the EEG of 42 children participating in the Mexico City Prospective Lead Study to determine if relative theta power and distribution across the scalp was related to history of lifetime lead exposure as measured by sequential blood lead concentration of the mother during pregnancy and the child after delivery. EEG was recorded from scalp electrodes placed according to the 10-20 system during eyes-closed. Theta activity (4-7 Hz) was filtered with a fast Fourier transform (FFT) and relative power calculated. The expected distribution of theta was found, with the greatest relative power centrally located and lesser amounts at frontal, occipital, and lateral derivations. Multiple regression models of theta at each electrode showed that increasing postnatal blood lead from 6 to 96 months was related to increasing relative theta power adjusted for age, sex and fetal suffering at delivery, in occipital derivations. The most significant increases in theta power were associated with blood lead levels (geometric mean = 10.3 microg/dl) measured between 54 and 72 months. Spatially weighted regression demonstrated that there was a significant antero-posterior gradient in lead-induced increase in relative theta power associated with postnatal blood lead levels at 54-72 months and 78-96 months. The greatest lead effect on both occipital relative theta power and the antero-posterior gradient of theta power was found with lead at an age during which relative theta power reaches its developmental maximum and starts to decrease. Results suggest that 54-72 months represent a critical period during which lead can exert lasting effects on the developmental pattern of theta activity. Occipital derivation of the largest effects of lead on theta activity may also be related to other lead-related developmental deficits.

Absence seizures effects on reading revealed by video-electroencephalography.

OBJECTIVE: The effects of absence seizures on reading have not been studied. The purpose of this paper is to show some alterations in reading during absence seizures in patients with video-electroencephalographic recordings. METHODS: Patients were selected if absences seizures were the only type of seizures. They were studied at rest with eyes closed and while reading aloud a text by simultaneous bipolar electroencephalographic and video recordings. RESULTS: Eight patients were studied with 34 events. Absences ranged from 1-12 events in twenty-five minutes recording, seizures duration ranged from 1.5-16 seconds. Brief seizures results on non-stop reading, but reading arrest with latency of 1-3 seconds after seizure onset were present in the longer events. Post-absence amnesia ranged from 1-4.5 seconds. Re-start reading occurs mainly in other reading place in the text, but two patients in one event re-started reading in the right place. Classic symptoms during absence were present and reading alterations found were: reading arrest, lost of reading point, bradylexia, dysprosodic reading, grapheme substitution, reading loudness reduction, repeating of phrases. Events occurred without patient seizure awareness, except in one patient by means of the time lost between onset to the end of the event. CONCLUSIONS: This study showed that acute reading alterations during absence seizures are frequent in longer seizures, producing many neuropsychological symptoms that alter reading without seizure awareness.

Brainstem auditory evoked response at five years and prenatal and postnatal blood lead.

Previous work from this laboratory demonstrated an association between higher maternal blood lead level at 20 weeks of pregnancy and increased I-V and III-V interpeak intervals in the brainstem auditory evoked response (BAER) recorded in 1-month-old infants. We repeated the BAER measurements with a larger group of children (n = 100-113) from the same study at 5-7 years. Maternal blood lead level at 20 weeks of pregnancy (geometric mean = 7.7 microg/dl; range 1-30. 5 microg/dl) was the only prenatal blood lead level significantly associated with I-V and III-V interpeak interval in a multiple regression model controlling for head circumference and age at time of testing and sex. In contrast to the findings at 1 month of age, interpeak intervals decreased as a linear function of increasing 20-week maternal blood lead. A nonlinear, orthogonal, second-order polynomial model was a significantly better fit to the data than the linear model. The nonlinear model showed I-V and III-V interpeak intervals decreased as blood lead rose from 1 to 8 microg/dl, and then increased as blood lead rose from 8 to 30.5 microg/dl. We hypothesized that the negative linear term was related to lead effect on brainstem auditory pathway length, and that the positive quadratic term was related to neurotoxic lead effect on synaptic transmission or conduction velocity. We found support for the brainstem length interpretation in the data, showing that 6-year-old head circumference in these children significantly decreased with increased maternal 20-week blood lead level. Increasing postnatal blood lead at 12 and 48 months was related only to decreased BAER conduction intervals across the entire blood lead range, suggesting only pathway length effects. Alterations in BAER at this age may indicate that the effect of prenatal lead exposure on the auditory brainstem is permanent, as response latencies reach essentially adult values by 4 years of age.

Thinner abuse alters optokinetic nystagmus parameters.

BACKGROUND: Deliberate self-inhalation of solvents such as thinner is a recognized problem in underdeveloped countries, with chronic abuse resulting in neurological impairment. In this article, we use electronystagmography (ENG) to study optokinetic nystagmus abnormalities (OKN) that may be induced by thinner consumption. METHODS: Twenty-five patients exposed to thinner for 5-20 years, in an irregular fashion of consumption, were recruited from a toxicologic center. Twenty-five control subjects were invited to participate as volunteers matched by age (+/-2 years) and gender. At the time of evaluation, all had abstained from intoxicants for at least 4 weeks. ENG recordings were performed by clinicians masked to the patient's group. Clockwise and counterclockwise stimulation were performed at 20 and 40 degrees /sec. RESULTS: None of the patients showed spontaneous nystagmus during the test period. Differences between thinner abusers and controls on clockwise and counterclockwise OKN on number of beats of nystagmus elicited on the 40 degrees /sec velocity were identified. The thinner abusers group showed a lesser number of nystagmus (p level was 0.02 and 0.005, respectively). CONCLUSIONS: The present results confirm the sensibility of OKN as an early marker of solvent abuse. These results were obtained in middle-term chronic exposure to solvent mixtures and are in favor of both cortical and brainstem dysfunction.

Electrophysiological and behavioral methods in early detection of hearing impairment.

BACKGROUND: Recent advances in neonatal life-support systems have contributed to the survival of high-risk newborns. However, protection of the auditory system and the prevention of sequelae is still paramount in neonatal neurology. The aim of this study was to compare auditory-evoked responses with a toy test and acoustic reflex in the early detection of hearing loss in infants. METHODS: Three groups were studied. The first was composed of infants showing less than a 30 dB biaural threshold in the neurophysiological test. The second group was made up of infants showing peripheral alterations on one side or both ears. The third group was comprised of infants who showed no responses at 95 dB HL in both ears after neurophysiological testing. The neurophysiological test, toy test, and acoustic reflex were performed on the same day, with masked results given to each investigator. Sensitivity and specificity for each toy test and acoustic reflex were calculated afterward. RESULTS: Forty-five controls, 44 peripheral alterations, and 8 non-response infants were studied. Most patients studied were born prior to the 37(th) week of gestation with a birthweight of less than 2,250 g, received required administration of potential ototoxic drugs and mechanical ventilation, and showed hyperbilirubinemia and hypoxia. Sensitivity for each toy was as follows: drum 0.54; wooden rattle 1.0, and metallic ratle 0.88. Specificity was 0.95, 1.0, and 1.0, respectively. Acoustic reflex sensitivity was 0.38 and specificity was 0.97. CONCLUSIONS: Results suggest that the wooden and the metallic rattles of the toy test can be useful tools in the study of hearing in the high-risk infant and deserve more attention in future studies.

Phonological and visuo-spatial working memory alterations in dyslexic children.

BACKGROUND: Working memory allows the retention of a limited amount of information for a brief period of time and the manipulation of that information. This study was undertaken to compare possible differences in working memory between dyslexic and control children. METHODS: To test the executive central process that controls attention, subjects were requested to assemble a 100-piece puzzle. To test the phonological loop, subjects were requested to repeat orally a 10-item list with the following characteristics: digits spanning two numbers; phonologically similar words, and unfamiliar pseudowords. The visuo-spatial sketchpad was tested by means of assembling a 25-piece puzzle. RESULTS: Forty dyslexic and and forty control children were studied. Dyslexic children recall a lesser number of similar words in the phonological loop and spend a longer time in puzzle assembly in the visuo-spatial sketchpad. No statistical difference in the central executive process was found. CONCLUSIONS: Present results suggest the importance of visuo-spatial and phonological loop alterations in dyslexic children that may result in difficulties with similar words and spatial information.

[Auditory provoked potentials in children with neonatal risk for hypoacusia]. / Potenciales provocados auditivos en niños con riesgo neonatal de hipoacusia.

Auditory evoked potentials of the brain stem (AEPBS) provide a simple noninvasive method of evaluating hearing function and have been widely used for early detection of hypoacusis in children. Between April 1992 and May 1994, a study was done of 400 Mexican children who presented at least one neonatal risk factor for hearing impairment. The average age of the children studied was 6.6 months and their average gestational age at birth was 35.1 weeks. Just over half of them (51%) had been treated with amikacin. The study found 1427 risk factors (3.5 per child), the most common ones being exposure to ototoxic substances, hyperbilirubinemia, and birthweight of less that 1500 g. In 27% of the children, peripheral auditory changes were found, and 13% did not respond to auditory stimuli. Low birthweight and young gestational age at birth, high serum concentration of bilirubin, sepsis, subependymal or intraventricular hemorrhage, mechanical ventilation, and exposure to ototoxic substances were significantly associated with the presence of severe or profound hypoacusis.

[Auditory evoked potentials in addicts to organic solvent inhalation]. / Potenciales provocados auditivos en adictos a la inhalación de solventes orgánicos.

Organic solvents affect the membrane lipids of neurons and glial cell. This led us to search for auditory damage, by means of brainstem auditory evoked responses, in subjects with chronic inhalation of thinner. Waves III and V showed delayed latency at an intensity of 90 dB, and wave V was delayed at 70 and 30 dB; the interwave intervals I-III and I-V at 90 dB and the interpeak I-V at 70 dB were also retarded. Three subjects did not show a response to stimulation at 30 dB: pure tone audiometry showed biaural mild hypoacusia in them. These results show that chronic inhalation of thinner may alter the auditory pathway of addicts.

[Brain stem auditory evoked responses in rats. Effects of the development, stimulation rate and electrode placement]. / Potenciales evocados auditivos del tronco cerebral en ratas. Efectos del desarrollo, frecuencia del estímulo y colocación de los electrodos.

Brainstem auditory evoked responses (BAER) were studied in Long-Evans rats in relation to development, stimulation frequency and electrode placement. Recordings made on day 11 of life showed no BAER. From day 14 on, four BAER waves were observed and centripetal maturational changes in wave latency were evident. Wave I attained adult latency values at day 20-22, wave II at day 24-25, wave II at day 24-25, and wave IV at day 39 of life. BAER latencies elicited by 8,000-Hertz tone-pips were shorter than those obtained with clicks and 4,000 Hz. Only wave II latency measures were affected significantly by electrode location.

Electro-oculographic recordings reveal reading deficiencies in learning disabled children.

This study was undertaken in order to learn the functional differences in reading tasks between two groups of children: those identified as learning disabled and a group of control children. During the earliest stages of learning to read, children adopt a logographic strategy, in which letter order is ignored and phonologic factors are secondary. The children later move into an alphabetic and then to an orthographic reading stage. Reading strategies can be studied by electro-oculographic (EOG) recordings during text reading. This investigation uses EOG to study text reading time, and number of saccadic and regressive movements, to test if learning disabled children show altered strategies on text reading. Nineteen learning disabled and thirteen control subjects were included in the study. Learning disabled children showed longer text reading time, and greater number of saccadic and regressive eye movements. Electro-oculographic recording is not a test customarily performed on learning disabled children. However, our results concerning the dynamic discriminative reading have shown that it can be a useful tool for the examination of learning disabled children.

Pattern-visual evoked potentials in thinner abusers.

Organic solvents cause injury to lipids of neuronal and glial membranes. A well known characteristic of workers exposed to thinner is optic neuropathy. We decided to look for neurophysiologic signs of visual damage in patients identified as thinner abusers. Pattern reversal visual evoked potentials was performed on 34 thinner abuser patients and 30 controls. P-100 wave latency was found to be longer on abuser than control subjects. Results show the possibility of central alterations on thinner abusers despite absence of clinical symptoms.

[Risk factors for hypoacusis and audiometric findings in preschool children who had been admitted to neonatal intensive care units]. / Factores de riesgo para hipoacusia y hallazgos audiométricos en una población preescolar egresada de cuidados intensivos neonatales.

Thirty preschool children who survived from a neonatal intensive care unit were studied with pure tone audiometry between 125 to 8000 Hertz. Examinations were performed in a cross-sectional study at 36 to 72 postnatal months of age. Hypoacusis was found in three patients. Risk factors most frequently found in hypoacusic children were hyperbilirubinemia, hypoxia neonatorum and ototoxic exposure. All hypoacusic children had a history of preterm birth, one suffered hypoxia neonatorum, and two hyperbilirubinemia. The patients' group had an average of 2.26 risk factors. These data suggest that perinatal auditory damage occurs in the presence of additional hearing damage risk factors leading to hypoacusis.

Prenatal and perinatal lead exposures alter acoustic cry parameters of neonate.

We performed acoustic analyses on cries elicited from a subset of healthy babies born to the Mexico City Prospective Lead Study at 2 days (n = 75), 15 days (n = 176), and 30 days (n = 166). Lead was measured in maternal blood every 8 weeks during pregnancy from week 12 to delivery and in umbilical cord (1-38 micrograms/dL, 0.05-1.84 mumol/L). Percent nasalization and number of cries decreased in babies born to mothers with higher lead levels in the last two trimesters while median fundamental frequency increased in babies born to mothers with higher lead at 12 weeks of pregnancy, and with higher cord lead in multiple regression analysis. Decreased percent nasalization was related to increased brainstem auditory evoked response latencies and interpeak intervals in a subset of the sample. The results suggest an effect of gestational exposure to lead on apparatus innervated by cranial nerves and/or lead effect on cry mediated by lead-altered auditory function. Altered baby cry and auditory function associated with lead might contribute to developmental delays by affecting early communication between caretaker and baby.

Potenciales evocados auditivos de tallo cerebral en rana catesbeiana / Brainstem auditory evoked responses on rana catesbeiana

Se estudió la sensibilidad de la vía auditiva a través del registro de los potenciales auditivos de tallo cerebral en 10 anfibios sanos de la especie Rana catesbiana. Las respuestas auditivas se efectuaron a 70, 50, 40 y 30 dB NA, en dos grupos de diferente peso. El primero de 17 a 27 gr y el otro grupo de 36 a 86.5 gr, los electrodos fueron insertados subcutáneamente y la estimulación fue por clicks en campo libre dentro de una cámara sonoamortiguada. A 70 dB las respuestas fueron de dos ondas en los primeros milisegundos, a 50 dB la onda II se separó en dos subcomponentes (IIa y IIb). El umbral electrofisiológico se estableció en 40 dB

Prenatal and perinatal low level lead exposure alters brainstem auditory evoked responses in infants.

Wave III latency and the III-V interpeak interval of brainstem auditory evoked responses in infants in the first weeks of life decreased and increased, respectively, in association with mid-pregnancy maternal blood lead levels (2.5-35 micrograms/dl) in a group of 30 prospectively followed healthy pregnancies and deliveries. The rapid myelination of brainstem auditory pathways occurring around mid-pregnancy and the lengthening of the III-V interpeak interval with increased mid-pregnancy maternal lead suggest that brain structures involved in spatial localization of sound may be compromised by prenatal lead exposure. The data also indicate that maternal blood lead measurements during pregnancy provide an adequate surrogate index of fetal exposure.

[Brainstem auditory evoked potentials in low and high risk newborns]. / Potenciales provocados auditivos del tallo cerebral en recién nacidos de bajo y alto riesgo.

Brainstem auditory evoked potentials (BAEP) were performed in a population of preterm infants of 32-34, 35-37 and 38-41 weeks of gestational age (GE) high risk newborns, and in 38-41 weeks GE low risk newborns. Statistical differences were found between both 38-41 weeks GE groups. High risk newborns showed longer latencies of waves III and V (P < 0.001), and I-III and I-V interwave intervals (P < 0.01). Our data show that auditory brainstem system suffer in high risk newborns. Results is discussed in relationship with other brainstem auditory evoked potentials studies in high risk newborns due it's clinical implications of present data.