Power spectral analysis of the EEG following protein malnutrition

Boron deprivation alters rat behaviour and brain mineral composition differently when fish oil instead of safflower oil is the diet fat source*

PRIMARY OBJECTIVE

To determine whether boron deprivation affects rat behaviour and whether behavioural responses to boron deprivation are modified by differing amounts of dietary long-chain omega-3 fatty acids.

RESEARCH DESIGN

Female rats were fed diets containing 0.1 mg (9 micromol)/kg boron in a factorial arrangement with dietary variables of supplemental boron at 0 and 3mg (278 micromol)/kg and fat sources of 75 g/kg safflower oil or 65 g/kg fish (menhaden) oil plus 10 g/kg linoleic acid. After 6 weeks, six females per treatment were bred. Dams and pups continued on their respective diets through gestation, lactation and after weaning. Between ages 6 and 20 weeks, behavioural tests were performed on 13-15 male offspring from three dams in each dietary treatment. The rats were euthanized at age 21 weeks for the collection of tissues and blood.

METHODS AND PROCEDURES

At ages 6 and 19 weeks, auditory startle was evaluated with an acoustic startle system and avoidance behaviour was evaluated by using an elevated plus maze. At ages 7 and 20 weeks, spontaneous behaviour activity was evaluated with a photobeam activity system. A brightness discrimination test was performed on the rats between age 15 and 16 weeks. Brain mineral composition was determined by coupled argon plasma atomic emission spectroscopy. Plasma total glutathione was determined by HPLC and total cholesterol and 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha) were determined by using commercially available kits.

MAIN OUTCOMES AND RESULTS

Boron-deficient rats were less active than boron-adequate rats when fed safflower oil based on reduced number, distance and time of horizontal movements, front entries, margin distance and vertical breaks and jumps in the spontaneous activity evaluation. Feeding fish oil instead of safflower oil attenuated the activity response to boron deprivation. In the plus maze evaluation, the behavioural reactivity of the boron-deficient rats fed fish oil was noticeably different than the other three treatments. They made more entries into both open and closed arms and the center area and thus visited more locations. The boron-deficient rats fed fish oil also exhibited the lowest copper and zinc and highest boron concentrations in brain and the highest plasma glutathione concentration. Both boron deprivation and safflower oil increased plasma 8-iso-PGF2alpha.

CONCLUSIONS

Both dietary boron and long-chain omega-3 fatty acids influence rat behaviour and brain composition and the influence of one these bioactive substances can be altered by changing the intake of the other. Brain mineral and plasma cholesterol, glutathione and 8-iso-PGF2alpha findings suggest that rat behaviour is affected by an interaction between boron and fish oil because both affect oxidative metabolism and act the cellular membrane level.

León Cintra's contribution to the field of protein malnutrition effects on sleep and the brain

On June 19 2009, everyone who knew Leon Cintra was shocked by the terrible news of the automobile accident that took his life. The feeling within the scientific community was that his passing was not only a great loss for Mexican science but also the loss of a beloved friend. He will be missed and forever remembered for his brilliant mind and noble heart. His scientific career was focused, since the beginning, on the study of protein malnutrition effects on brain morphometry, somato-sensory transmission, sleep, circadian rhythms and behavior. His findings showed that malnutrition has long lasting adverse effects on morphometry of systems involved in sleep regulation such as locus coeruleus, nucleus raphe dorsalis and susprachiasmatic nucleus, and on hippocampal circuit implicated in theta activity generation. His results on spectral analysis of electrical field potential at every 4 sec from 24-h baseline recording and 72-h of recovery sleep after total sleep deprivation or selective REM sleep deprivation demonstrated that protein malnutrition induced alterations on homeostatic as well as on circadian sleep regulation; brain oscillations and theta coherent activity between left and right hemisphere and between hippocampus and cerebral cortex are also affected by malnutrition.

Nutrition and neurodevelopment: mechanisms of developmental dysfunction and disease in later life

Nutrition plays a central role in linking the fields of developmental neurobiology and cognitive neuroscience. It has a profound impact on the development of brain structure and function and malnutrition can result in developmental dysfunction and disease in later life. A number of diseases, including schizophrenia, may be related to neurodevelopmental insults such as malnutrition, hypoxia, viruses or in utero drug exposure. Some of the most significant findings on nutrition and neurodevelopment during the last three decades, and especially during the last few years, are discussed in this review. Attention is focused on the underlying cellular and molecular mechanisms by which diet exerts its effects. Randomized intervention studies have revealed important effects of early nutrition on later cognitive development, and recent epidemiological findings show that both genetics and environment are risk factors for schizophrenia. Particularly important is the effect of early nutrition on development of the hippocampus, a brain structure important in establishing learning and memory, and hence for cognitive performance. A major aim of future research should be to elucidate the molecular mechanisms underlying nutritionally-induced impairment of neurodevelopment and specifically to determine the mechanisms by which early nutritional experience affects later cognitive performance. Key research objectives should include: (1) increased understanding of mechanisms underlying the normal processes of ageing and neurodegenerative disorders; (2) assessment of the role of susceptibility genes in modulating the effects of early nutrition on neurodevelopment; and (3) development of nutritional and pharmaceutical strategies for preventing and/or ameliorating the adverse effects of early malnutrition on long-term programming.

Cortical sources of awake scalp EEG in eating disorders

OBJECTIVE

To investigate quantitative EEG (qEEG) in anorexia nervosa (AN) and bulimia nervosa (BN) in comparison with healthy controls.

METHODS

Resting EEG was recorded in 30 healthy females (age: 27.1+/-5.5), 16-AN females (age: 26.4+/-9.5) and 12-BN females (age: 27.0+/-6.3). Cortical EEG sources (delta, theta, alpha 1, alpha 2, beta 1, beta 2) were modeled by LORETA solutions. The statistical analysis was performed considering the factors Group, power Band, and region of interest (central, frontal, parietal, occipital, temporal, limbic).

RESULTS

Alpha 1 sources in central, parietal, occipital and limbic areas showed a greater amplitude in Controls versus AN and BN groups. Alpha 2 sources in parietal, occipital and limbic areas showed a greater amplitude in Controls than in both AN and BN groups. Alpha 1 sources in temporal area showed a greater amplitude in Controls compared to both the BN and AN groups as well as in the BN group compared to AN group. Central alpha 1 source correlated significantly with BMI in patients.

CONCLUSIONS

These results support the hypothesis that eating disorders are related to altered mechanisms of cortical neural synchronization, especially in rolandic alpha rhythms.

SIGNIFICANCE

To our knowledge this is the first study by LORETA able to detect modifications of cortical EEG activity in eating disorders.

Effects of prenatal protein malnutrition on perforant path kindling in the rat

Rats born to dams fed either a 6% (malnourished) or 25% (control) casein diet during gestation were all fostered to lactating dams on the 25% casein diet 24 h after birth and were maintained on this diet throughout life following weaning. At 90-120 days of age electrographic and behavioral responses to electrical kindling of the medial perforant pathway were investigated in animals from both the straight 25% diet (designated 25%/25% for the pre- and postnatal periods) and the dietary rehabilitated (designated 6%/25% casein diet for the pre- and postnatal periods) groups. Animals of the dietary rehabilitated group (6%/25%) were found to: (1) require a significantly lower stimulus intensity to evoke afterdischarge activity in the ipsilateral dentate gyrus; (2) progress through the various behavioral stages of kindling in a markedly different manner from the 25%/25% group, and; (3) require significantly more daily kindling stimulations to attain the full motor convulsive stage indicative of the kindled state. These results indicate that dietary protein rehabilitation at birth is incapable of reversing or significantly ameliorating the effects of gestational protein deficiency on susceptibility to seizure activity and acquisition of the kindled state. These findings indicate that gestational protein deficiency results in long-lasting, if not permanent, changes in neuronal systems in the hippocampal formation which are involved in both the electrographic and behavioral correlates of the kindling process.

Age-related change in the multiple unit activity of the rat brain parietal cortex and the effect of centrophenoxine

In this study, spontaneous multiple unit activity (MUA, action potentials derived simultaneously from a number of neurons in a given brain region) was recorded through electrodes chronically implanted in the parietal cerebral cortex of the rats of 1, 3, 6, 9, 12, and 26 months of age (cross-sectional study). Electrophysiological recordings were obtained from unrestrained conscious rats using standard techniques. The results indicated that multiple unit activity was decreased with aging (senescence). Maximum firing rate (MUA counts) was found at the age of 3 months. At 6 months of age, the MUA was decreased by about 30%, while during 6 to 12 months of age the activity seemed to remain unchanged. At 26 months of age the firing rate was, however, further decreased (about 40%). Centrophenoxine administration led to an increase in MUA in the rats of 12 and 26 months of age. The results, thus, further showed that centrophenoxine, a nootropic drug known for its antiaging effects in experimental animals as well as in humans, also manifested beneficial effects electrophysiologically. The data presented in this work are new and significant, since although age effects on gross electrophysiological signals (EEG, evoked potentials, etc.) are known, the aging changes in cellular level electrophysiological signals (action potentials) have not been generally studied particularly in conscious animals.

Deviations in brain development due to caloric undernutrition and scope of their prevention by rehabilitation: alterations in the power spectra of the EEG of areas of the neocortex and limbic system

Wistar rats underwent caloric undernutrition so as to produce undernourished pups (F1, both male and female), which were put on a reduced diet throughout life, causing deficits in body weight of 40-70%, and in brain weight of 14-20% by adulthood. These chronic undernourished rats were mated and their progeny (F2), which had suffered gestational and postnatal undernutrition, were undernourished, like their parents, throughout life until the moment of use in this study. At this degree of chronic undernutrition, rats do not appear to be sick or morbid, but only small-for-age, they are active and can reproduce. The computer-generated power spectra of the EEG of two neocortical areas (visual and motor) and of 3 regions of the limbic system (cingulate, hippocampus and olfactory bulb) of the chronically undernourished pups were obtained at different ages from birth to adulthood, and compared with the normal ontogenetic patterns of corresponding areas obtained from age-matched controls. In another group of rats, the undernutrition was imposed on normal pups from the day of weaning (21st day), i.e., after the major part of the brain growth spurt is over. Finally, the effect of restituting normal rehabilitatory nutrition from the day of weaning on the chronic group was also studied. The results show that all brain regions studied were affected by the chronic caloric undernutrition. The deviations from the normal consist of: (1) an initial lag or delay in the development of the EEG amplitude and activity by several days, (2) a later development of an abnormally high amplitude or power in the EEG power spectra by about the weaning age, and (3) an imbalance in the occurrence of the characteristics of the EEG of the respective areas of the brain (the low and high frequency spindles of slow sleep, the slow and fast theta activities of paradoxical sleep of the hippocampus, the delta rhythm, etc.). While the chronic undernutrition was continuing there was also a certain degree of spontaneous reduction in the magnitude of abnormality after about 80 days of age, instead of worsening with age, perhaps due to an intrinsic adaptational readjustment to the stress of the nutritional deprivation. The results reveal a variation in the susceptibility of development to these abnormalities. Typical examples of the range of variation of the effects are presented in the results showing that there can be nearly normal EEG patterns in some undernourished subjects (about 14-22%), and also that there can be abnormal EEG power spectra in a proportion of normals (up to about 20%).(ABSTRACT TRUNCATED AT 400 WORDS)

Spectral analysis of the electroencephalogram in the developing rat

Power spectral measures of the EEG obtained from the frontal cortex and hippocampal formation during different vigilance states in the developing rat have been computed and compared. The most significant ontogenetic changes were observed in the hippocampal power spectra obtained during the vigilance state of REM sleep. These spectral analyses have revealed in the hippocampus: (1) a significant increase in the frequency at which the peak power occurs in the theta-frequency (4-11 Hz) band from 14 to 45 days of age; (2) a decrease in the quality factor of the peak from 14 to 45 days of age; (3) a decrease in the relative power co-ordinate for the center of spectral mass associated with the 0-4-Hz frequency band coupled with an increase in the frequency coordinate of the 4-11-Hz frequency band from 14 to 45 days of age, and; (4) a significant decrease in the average percent relative power associated with the 0-4-Hz frequency band from 14 to 22 days of age. For the EEG obtained from the frontal cortex, the major findings of note were: (1) a dominant contribution of relative power in the 0-4-Hz frequency band which was observed at every age and during every vigilance state tested, and; (2) a significant increase in the average percent relative power associated with this band at 18, 22, and 45 days of age. The results of this study provide a quantitative description of the electroencephalographic (EEG) ontogeny of the hippocampal formation and the frontal cortex in the rat. These ontogenetic changes in EEG activity relate closely to development of the internal circuitry and synaptic maturation in the hippocampal formation and frontal cortex.

Maternal malnutrition in the rat: effects on food intake and body weight

The effects of dietary protein level on food intake and body weight were examined in adult female rats during a 35-day pre-mating period and during gestation and lactation. During the pre-mating period, no differences in daily food intake were observed among rats fed a 6% casein, 8% casein or 25% casein diet. However, during this period, rats fed the 6% casein diet gained significantly less weight than those with ad lib access to the 8% or 25% casein diets or than rats pair-fed the 25% casein diet in amounts equivalent to that consumed by rats in the 6% or 8% casein groups. Additionally, rats fed the 6% casein diet displayed decreased efficiency of energy utilization, calculated as weight gain per 100 kilocalories consumed, relative to rats fed the 8% or 25% casein diets. No differences in food intake were observed among the groups during gestation. However, rats fed the 6% casein diet gained less weight than rats fed the 8% or 25% casein diets. During lactation rats fed either the 6% or 8% casein diet consumed significantly less food than animals given the 25% casein diet ad lib. During the second week of lactation, rats receiving ad lib access to the 25% casein diet gained weight while those receiving the 6% or 8% casein diets continued to lose weight. At parturition, body weights of pups did not differ as a function of dietary condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Power spectral analysis of hippocampal and cortical EEG activity following severe prenatal protein malnutrition in the rat

We have studied the effects of prenatal protein malnutrition on development of the hippocampal and frontal cortical electroencephalographic (EEG) activity. Using power spectral analyses in rats of several age groups we found that protein malnutrition, instituted prenatally and continued postnatally, produces marked alterations in power spectral measures, i.e., alterations in peak theta frequency in the hippocampus during rapid eye movement (REM) sleep. Peak theta frequency was found to be significantly retarded in malnourished animals, especially during the preweaning period of development. Protein malnutrition, therefore, appears to affect mechanisms responsible for generating the tonic component of theta activity.

Ontogeny of electrical activity of main olfactory bulb in freely-moving normal and malnourished rats

Electroencephalographic activity (EEG) was recorded from the main olfactory bulb (MOB) in freely-moving, normally-nourished, (NP, normal-protein diet) and malnourished (LP, low-protein diet) rats from 4 days of age through adulthood. MOB EEG was analyzed for dominant frequency components using power spectral techniques. For NP rats, a single dominant frequency component (induced wave) was present in the MOB EEG at 4-6 days of age. From 10 days of age through adulthood, the MOB EEG contained two dominant frequency components (induced and intrinsic waves). Both the induced wave and intrinsic waves increased in center-frequency to reach maturity at approximately 30 days of age. Rats reared on low-protein diets (8% casein, prenatal and postnatal) displayed relatively permanent retardation in the development of induced wave center-frequencies and a delay in the development of the intrinsic wave center-frequencies. These results closely parallel the morphological development of the MOB in normally-nourished and malnourished rats.

Spectral analysis of neocortical and hippocampal EEG in the protein malnourished rat

In these studies, power spectral analysis techniques were utilized to quantify changes in the cortical and hippocampal EEG obtained from rats reared on either an 8% or 25% casein diet as they mature from 14 to 22 days of age. Analyses of the power spectral data obtained from the frontal cortex of rats reared on the 25% casein diet during this preweaning period (14-22 days) indicated increases in the power in the 0.5-3.5 c/sec frequency band primarily during slow-wave sleep. Prenatal protein malnutrition (8% casein diet) significantly reduced the low frequency power content in the cortical EEG obtained during slow-wave sleep at 18 and 22 days of age. Analyses of power spectral data obtained from the hippocampal EEG during REM sleep also revealed developmental and diet-related differences. The frequency at which the peak power occurs in the theta band (4-11 c/sec) was found to increase normally in a linear fashion from 14 to 22 days of age (from 4.4 to 5.5 c/sec) in rats reared on the 25% casein diet. In addition, power in the 4-7 c/sec band significantly increased during this preweaning period. Prenatal protein malnutrition significantly slowed the development of theta frequency and produced higher values of power in the component of theta rhythm. Finally, vigilance profiles showed that rats normally progress from 14 days of age when REM sleep dominates their vigilance profile, to 22 days of age when they spend significantly more time in slow-wave sleep. Prenatal protein malnutrition retards this normal developmental sequence by significantly reducing the REM sleep time at 14 and 18 days of age and increasing the time spend in aroused waking at both these ages. However, at the time of weaning, i.e., at 22 days of age, these differences in sleep-waking behavior were no longer observed to be significant.