Mid latency and slow vertex responses during pregnancy

Central auditory pathways picked up electro-physiologically as mid latency responses (MLRs) and slow vertex responses (SVRs) have been studied least in women during their critical periods of life although auditory brainstem responses (ABRs) have been studied by many researchers. In the present study MLRs and SVRs were recorded in 20 pregnant women of age group 18-28 years. Their period of gestation ranged between 26-40 weeks and pregnancy had been uneventful and normal. MLRs and SVRs were recorded from Cz-A1 and Cz-A2 positions with alternating 90 dB sound pressure click stimuli delivered at 5 Hz and 0.5 Hz respectively. 256 stimuli for mid-latency and 64 stimuli for slow vertex responses were averaged and analyzed. Different waves of these auditory evoked responses were compared with 20 age matched non-pregnant females. The data obtained was analyzed for each variable by using unpaired student's T test. Present study did not reveal any difference in MLR waves during pregnancy when compared with the non-pregnant females whereas all the SVR waves were found to be significantly delayed in pregnant females. As SVR generators are found in different cortical areas, it can be said that auditory information processing at the higher centers is slow during pregnancy which in turn could be due to elevated levels of sex hormones specially estrogen and progesterone during pregnancy.     

Sensory, cognitive and motor assessment of children with poor academic performance: an auditory evoked potential study

The present study aims to evaluate the auditory sensory process in the brainstem, thalamocortical and cortical areas by using auditory evoked potentials [auditory brainstem response (ABR), mid latency response (MLR) and slow vertex response (SVR)], cognitive functions by P300 and motor response by reaction time in children with poor academic performance. Thirty children between 6-12 years of age were selected as subjects on the basis of poor academic school records. While thirty children with good academic performance served as controls. The recordings were done using a computerized evoked potential recorder by 10-20 electrode placement system. There was no difference in the anthropometric parameters and IQ of the two groups. There was a significant increase in latency of waves II, III, IV and V, and Inter-peak latency I-V of ABR in poor performer females. All the component waves of MLR and SVR showed increased latency in the subjects but could not reach the level of significance. There was a significant increase in latencies of P300 at Cz and Pz electrode positions with no change in amplitude in poor performer females. The reaction time was also increased in the poor performer females as compared to the controls. The latencies of all the waves of ABR, P300 and reaction time are also increased in male poor performers as compared to male controls but could not reach the level of significance. The conduction of impulses is slower in pontine and midbrain auditory pathway along with inefficient cortical processing of task relevant stimuli and motor response in female children having poor academic performance.     

Auditory evoked responses during different phases of menstrual cycle

The electrophysiological correlates of changes in sensory function during menstrual cycle has already been studied and attributed to the hormonal influence. Effects of estrogen and progesterone on waves of auditory brainstem responses (ABR) have been reported and a hypothesis has been proposed that sex steroids have more influence on central auditory pathways. As mid-latency responses (MLRs) and slow vertex responses (SVRs) are better indicators of central auditory pathways, so MLRs and SVRs were also recorded besides ABRs in the present study. Waves of ABRs, MLRs & SVRs were recorded in 20 normal cycling females in 4 different phases of menstrual cycles from Cz-A1 and Cz-A2 position with alternating 90dB sound pressure click stimuli. Contralateral ear was masked with a white noise of -40 dBHL. With the same setting by changing the number of click stimuli, intervals of stimuli and filter bandpass the above 3 recordings were taken. The evoked responses in females having ovulatory cycles were compared within the four phases using ANOVA test. There is a trend of increase in peak latencies of ABR waves III and V and IPL I-V in estrogen-peak midcycle while decrease in latencies in progesterone-peak (interpeak latency) midluteal phase. Peak latencies of MLR waves No, Po, Na, Pa and Pb also show a same trend. SVR waves P2 and N2 are significantly delayed in mid-cycle (178.80 +/- 20.49, 276.65 +/- 18.32) while conduction is faster in midluteal phase (166.45 +/- 17.41, 261.95 +/- 21.07). Smallest latencies of all the waves are occurring during menstruation. These findings are suggesting that normal cyclical variations in the levels of estrogen and progesterone during menstrual cycle do affect the auditory pathways and effects are better seen on the central component.     

Auditory evoked potential responses in menopausal women: a normative study

Three types of auditory evoked potential responses i.e. auditory brainstem response (ABR), middle latency response (MLR) and slow vertex response (SVR) were studied in 22 post-menopausal Indian women to have a normative value for each response. Recordings were done on computerised evoked potential recorder using 10/20 system of electrode placement and standard click stimuli. The results were comparable with similar studies done in the western world indicating that there is no ethnic variation in evoked potential responses. The latencies of ABR waves showed an increase in menopausal females when compared with young adults indicating a delay in neural transmission which might be due to changed hormonal milieu of sex hormones after menopause. The normative values of MLR and SVR which represent the thalamo-cortical and cortical auditory projections are being reported in Indian menopausal women for the first time.     

Auditory evoked responses in postmenopausal women on hormone replacement therapy

The effect of hormone replacement therapy (HRT) was studied in 32 postmenopausal women on their auditory Evoked Potentials i.e. auditory brainstem response (ABR), Middle latency response (MLR) & slow vertex response (SVR). Recordings were done on computerized evoked potential recorder using 10/20 system of electrode placement and standard click stimuli. A significant improvement in neural transmission was observed as was evidenced by decrease in the ABR wave latencies I, III, IV & V and interpeak latency III-V and I-V after 6 months of HRT. A similar significant decrease was observed in MLR wave latencies of Po, Na & Pa. The SVR wave latencies although found to be decreased after HRT, could not reach the level of statistical significance. There was a significant inverse correlation obtained between latencies of wave I in ABR, Po in MLR and serum estradiol. The results indicate the effect of sex hormone in improving transmission in auditory pathway from periphery through brainstem, thalamus upto cortex. However slow vertex responses indicate that auditory association areas are not much affected. This might have bearing on improvement of neuropsychological functions in postmenopausal women on HRT.     

Differential effects of exogenous estrogen versus a estrogen-progesterone combination on auditory evoked potentials in menopausal women

The study was undertaken to determine the differential effects of estrogen and progestin on auditory evoked responses in postmenopausal women receiving hormone replacement therapy (HRT). Forty-seven women between 45 and 70 years of age attending menopause and HRT clinic were divided into two groups. Group I included 32 women who attained natural menopause and receiving combined estrogen progestin therapy. While group II included 15 surgically menopausal women receiving only estrogen. Evoked potentials were recorded in form of auditory brainstem response (ABR), middle latency response (MLR) & slow vertex response (SVR). There was improvement of conduction in auditory pathways at the level of brainstem and thalamocortical projections as indicated by the decrease in latencies of most of the waves of ABR and/MLR after 6 months of HRT in both the groups. The conduction in association areas, as indicated by SVR, did not show a significant change. The intergroup comparison after therapy revealed a decrease in latency of wave V and I-V interpeak latency in group II indicating that only estrogen users are benefited more. Thus HRT facilitates the process of sensory conduction, which may form one of the mechanisms of improved neuropsychological functions in menopausal women on HRT. The addition of progestin to estrogen does not have a negative or potentiating effect on it.     

12- and 24-month neurobehavioural follow-up of children prenatally exposed to marihuana, cigarettes and alcohol

The motor, mental, and language development plus the home environment was examined in 217 twelve-month and 153 twenty-four-month-old children for whom prenatal exposure to marijuana, alcohol and cigarettes was previously ascertained. With this low-risk sample multiple regression analysis was used to assess the association between outcome measures and prenatal drug exposure while adjusting for potential confounding factors. Prenatal exposure to marijuana was uniquely positively associated with a series of items evaluating the child's attitudes and interests that reflect a cognitive factor. Moderate levels of alcohol were significantly associated with lower mental scores at 24 months of age. Prenatal maternal cigarette smoking was significantly associated with lower mental scores at 12 months of age and altered responses on auditory items at 12 and 24 months. However, at 24 months, the strong relationship of postnatal environmental factors with cognitive outcomes and with prenatal maternal smoking resulted in loss of significant, unique predictive power for maternal smoking. Based on the present work and supplemented by previously reported data pertaining to maternal attitudes during pregnancy and neonatal behaviour, a transactional interpretation is presented.     

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.     

Brainstem auditory evoked potentials (BAEPs) in pregnant women

The electrophysiological correlate of change in sensory function during pregnancy has not been reported. The brain stem auditory evoked potentials were recorded in eight pregnant women during third trimester from CZ-A1 and CZ-A2 position, with alternating 90 dB sound pressure click stimuli delivered at 10/sec and -40 dB (white noise) masking of contralateral ear. Two thousand and forty eight responses were analysed and replicated. The noise and other artefacts were rejected with filter bandpass setting 150 to 3000 Hz. The evoked responses in pregnant women were compared with ten age matched normal subjects using Student's 't' test. The threshold for eliciting wave V of the brainstem auditory response was higher in pregnant women (28.1 +/- 2.1 dB). The absolute peak latencies of waves I to V were similar in both groups. However, Inter peak latencies (IPLs) I-III, III-V were on higher side in the pregnant women, and I-V, in particular (3.9 +/- 0.14) was significantly higher when compared with controls (3.73 +/- 0.16). These findings suggest that besides an increase in evoking wave V threshold, neural conduction process in brainstem auditory pathways during pregnancy is also delayed within + 2SD of the mean central conduction time in nonpregnant state.     

Maternal smoking during pregnancy affects children's vigilance performance

Aspects of attentional behaviour in 4--7-year-olds, as assessed by auditory and visual vigilance tasks, were related to prenatal exposure to cigarettes. Data on 76--79 children born to healthy, white, predominantly middle-class women were analyzed using multiple regression techniques controlling for potentially confounding variables including postnatal second hand smoke exposure. Cigarette smoking during pregnancy was related to an increased activity level of the children during the tasks and increased errors of commission in the auditory task and, to a lesser degree, in the visual task. After controlling for confounding factors, the relationship between prenatal smoking and errors of omission did not retain significance. The combination of results suggest that the deficits in attention may reflect impulsive responding and increased overall activity.     

Reduced auditory acuity in rat pups from excess and deficient omega-3 fatty acid consumption by the mother

Consumption of the nutrients omega-3 fatty acids (omega-3 FA) during pregnancy and lactation is considered beneficial to fetal and infant development. It may also reduce the incidence and severity of preterm births by prolonging gestational length. However several recent human and animal studies have reported that over-supplementation with omega-3 FA, especially in the form of fish oil, can have adverse effects on fetal and infant development and the auditory brainstem response (ABR). Our goal was to assess further the effects of omega-3 FA excess and deficiency during pregnancy and lactation on the offspring's auditory acuity as evidenced by their ABR thresholds. Female Wistar rats were given diets that were either deficient, adequate (control) or excess in omega-3 FA from day 1 of pregnancy through lactation. The offspring were ABR-tested at the postnatal age of 24 days. The rat pups in the Excess treatment condition had significantly elevated (worse) ABR thresholds, postnatal growth restriction, and a trend for increased postnatal mortality in comparison to the Control group. The Deficient group was intermediate. In conclusion, excess or deficient amounts of omega-3 FA during pregnancy and lactation in the laboratory rat adversely affected the offspring's auditory acuity. Postnatal thriving was also adversely affected. Consuming or administering large or inadequate amounts of omega-3 FA during pregnancy and lactation seems inadvisable because of the potential for adverse effects on infant development.     

High dosage sildenafil induces hearing impairment in mice

Sildenafil is widely administered for the treatment of erectile dysfunction. Recently, sensorineural hearing loss following the ingestion of sildenafil was reported in one male patient. We examined hearing in mice that were administered high doses of sildenafil for up to 105 d. To assess hearing impairment, we evaluated auditory brainstem responses, auditory middle latency responses, and otoacoustic emissions. At high doses, sildenafil increased the hearing threshold shift of auditory brainstem responses. High-dose sildenafil treatment also resulted in delayed latency of both auditory brainstem responses and auditory middle responses. Otoacoustic emissions differed between control and high-dose sildenafil groups with long-term treatment. Collectively, these data demonstrate that high-dose and long-term sildenafil administration can induce hearing impairment in mice.     

Effects of calcitonin on human auditory and visual evoked brain potentials

Besides its Ca⁺⁺-regulative effects, calcitonin is known to diminish sensitivity to painful stimuli. The present study aimed to clarify whether calcitonin has similar effects on stimulus processing in other modalities. Effects of calcitonin were assessed on brain potentials recorded from the human scalp which were evoked either by auditory clicks or visual checkerboard pattern-reversals. Twelve healthy men were tested in a double-blind intra-subject design receiving either 0.1 IU/kg salmon calcitonin (sCT) or 1.0 IU/kg sCT or saline solution during a 20 min IV infusion. sCT significantly increased latency of wave V of the brainstem auditory evoked potential (BAEP). Effects on BAEP wave V increased in magnitude with increasing dose of sCT and with decreasing intensity of the click stimulus. There was also a slight increase in latency of the N80 of the pattern-reversal visual evoked potential (PR-VEP). Additionally, subjects rated themselves as less activated following the high dose of sCT compared to placebo. The pattern of results is in accord with a slowing or inhibitory influence of calcitonin on auditory and visual sensory processing, thus paralleling findings concerning calcitonin effects on the perception of painful somatosensory stimuli.     

成人正常听性脑干反应结果分析

目的观察正常成人听性脑干反应(auditory brainstem response,ABR)正常值范围及阈值,为早期干预治疗提供依据。方法对50名(100耳)男女各半的听力正常成人进行ABR检测,建立ABR正常值范围,讨论性别、耳别对测试结果的影响及阈值测定的临床应用。结果成人正常ABR波Ⅰ、Ⅲ、Ⅴ潜伏期的正常值范围分别是:(1.29±0.17)ms(、3.46±0.22)ms(、5.41±0.17)ms;女性潜伏期(PL)和波间期(IPL)短于男性组,差异具有统计学意义(P<0.05);无左右耳差异(P>0.05);正常成人ABR阈值(100耳)比主观纯音听阈高(15.1±0.9)dBnHL。结论建立成人正常ABR潜伏期及阈值正常值标准,为听损伤的早期诊断和随访监测提供可靠依据。     

The clinical free radical scavenger, edaravone, protects cochlear hair cells from acoustic trauma

It is known that reactive oxygen species have toxicity to the cochlea. We investigated the effect of edaravone, a free radical scavenger for clinical use, on the cochleae of guinea pigs subjected to acoustic trauma. We assessed auditory brainstem response (ABR) thresholds to evaluate cochlear function and observed the sensory epithelium. After noise exposure (130 dB SPL, 3 h), we observed that the auditory brainstem response threshold shift in edaravone-treated ears was significantly less than that in untreated ears. This result suggests that edaravone protected the cochleae from acoustic trauma.     

Neonatal behavioural correlates of prenatal exposure to marihuana, cigarettes and alcohol in a low risk population

Infant neonatal behaviour is significantly and differentially related to maternal marihuana, cigarette and alcohol use during pregnancy. Data on 250 babies born to healthy, predominantly middle-class women were analyzed using canonical analysis and multiple regression adjusting for potentially confounding variables. Prenatal marihuana exposure was associated with increased tremors and startles and poorer habituation to visual stimuli, prenatal cigarette exposure with increased tremors and poorer auditory habituation, whereas a relatively low level of alcohol consumption was marginally related to increased neonatal irritability.     

The Impact of Smoking and Other Substance Use by Urban Women on the Birthweight of Their Infants

The impact of maternal smoking and other substance use during pregnancy on infant birthweight is demonstrated in a sample of 766 urban women, using data collected in the Washington, D.C. Metropolitan Area Drug Study (DC*MADS). Women residing and giving birth in the District of Columbia were interviewed in 1992. A multivariable linear regression model was used to quantify the association between birthweight and the mother's use of cigarettes, alcohol, or illicit drugs during pregnancy, while controlling for possible confounding variables. The analysis focused on factors, including prenatal care and substance use during pregnancy that may contribute to low birthweight infants born to this sample of urban, predominantly black women. A woman's use of cigarettes, marijuana, and heroin during pregnancy was related to infant birthweight, but her use of alcohol and cocaine during pregnancy was not significantly related. Smoking during pregnancy was a strong predictor for low birthweight, suggesting that targeting more smoking cessation programs for pregnant women, particularly those who may also be illicit drug users, could help reduce adverse health consequences for low birthweight infants.     

Changes in auditory brainstem response in rats chronically exposed to carbon disulfide

The chronic effect of carbon disulfide (CS₂) on the central nervous system (CNS) was studied by examining auditory brainstem responses (ABRs) in female rats (Jcl Wistar) exposed to 200 ppm or 800 ppm CS₂ by inhalation, 6 h a day, 5 days a week, for 15 weeks. Two modes of ABRs evoked by clicks at 61 and 96 dB sound pressure levels (61 dB-ABR and 96 dB-ABR) were recorded during the exposure and for 6 weeks afterwards. Three main components (I, III and V) of ABRs were analyzed from the latencies and differences between latencies of them (interpeak latencies, IPL I–III, IPL III–V and IPL I–V). The latencies of the three components and IPLs of 96 dB-ABR in rats group exposed to 800 ppm of CS₂ were significantly delayed during the exposure period. The delay of latency of component V and IPL III–V and I–V tended to increase with exposure time. At 61 dB-ABR, the changes in the latency of component V, IPL III–V and I–V resembled those at 96 dB-ABR. For the rats group exposed to 200 ppm CS₂, the latency of component I, IPL III–V and I–V at 96 dB-ABR were delayed significantly but transiently during the exposure period. For both groups, recovery from the latencies of the three components and IPLs of ABR was observed by the end of the recovery period. The delayed latencies of ABR observed in rats exposed to 800 ppm CS₂ suggested a conduction dysfunction in the brainstem due to CS₂ exposure. The transient delay of the parameters in the rats group exposed to 200 ppm CS₂ was considered to represent a slight conduction dysfunction.     

The impact of smoking and other substance use by urban women on the birthweight of their infants

The impact of maternal smoking and other substance use during pregnancy on infant birthweight is demonstrated in a sample of 766 urban women, using data collected in the Washington, D.C. Metropolitan Area Drug Study (DC*MADS). Women residing and giving birth in the District of Columbia were interviewed in 1992. A multivariable linear regression model was used to quantify the association between birthweight and the mother's use of cigarettes, alcohol, or illicit drugs during pregnancy, while controlling for possible confounding variables. The analysis focused on factors, including prenatal care and substance use during pregnancy that may contribute to low birthweight infants born to this sample of urban, predominantly black women. A woman's use of cigarettes, marijuana, and heroin during pregnancy was related to infant birthweight, but her use of alcohol and cocaine during pregnancy was not significantly related. Smoking during pregnancy was a strong predictor for low birthweight, suggesting that targeting more smoking cessation programs for pregnant women, particularly those who may also be illicit drug users, could help reduce adverse health consequences for low birthweight infants.     

Abnormal neurological responses in young adult offspring caused by excess omega-3 fatty acid (fish oil) consumption by the mother during pregnancy and lactation

Consuming omega-3 fatty acids (omega-3 FA) during pregnancy and lactation benefits fetal and infant brain development and might reduce the severity of preterm births by prolonging pregnancy. However, diets that are relatively rich in omega-3 FA can adversely affect fetal and infant development and the auditory brainstem response (ABR), a measure of brain development and sensory function. We previously examined the offspring of female rats fed excessive, adequate or deficient amounts of omega-3 FA during pregnancy and lactation. The 24-day-old offspring in the Excess group, compared to the Control group, had postnatal growth retardation and poor hearing acuity and prolonged neural transmission times as evidenced by the ABR. The Deficient group was intermediate. The current study followed these offspring to see if these poor outcomes persisted into young adulthood. Based on prior findings, we hypothesized that the Excess and Deficient offspring would "catch-up" to the Control offspring by young adulthood. Female Wistar rats received one of the three diet conditions from day 1 of pregnancy through lactation. The three diets were the Control omega-3 FA condition (omega-3/omega-6 ratio approximately 0.14), the Excess omega-3 FA condition (omega-3/omega-6 ratio approximately 14.0) and Deficient omega-3 FA condition (omega-3/omega-6 ratio approximately 0% ratio). The Control diet contained 7% soybean oil; whereas the Deficient and Excess omega-3 FA diets contained 7% safflower oil and 7% fish oil, respectively. One male and female offspring per litter were ABR-tested as young adults using tone pip stimuli of 2, 4, 8 and 16 kHz. The postnatal growth retardation and prolonged neural transmission times in the Excess and Deficient pups had dissipated by young adulthood. In contrast, the Excess group had elevated ABR thresholds (hearing loss) at all tone pip frequencies in comparison to the Control and Deficient groups. The Deficient group had worse ABR thresholds than the Control group in response to the 8 kHz tone pips only. The Excess group also had ABR amplitude-intensity profiles suggestive of hyperacusis. These results are consistent with the Barker hypothesis concerning the fetal and neonatal origins of adult diseases. Thus, consuming diets that are excessively rich or deficient in omega-3 FA during pregnancy and lactation seems inadvisable because of risks for long-lasting adverse effects on brain development and sensory function.