Biomedical subjects

M A Persinger

Publications and source records attributed to M A Persinger.

At least 91 records · Page 5Linked to original sources

PubMed2001

Mast cell numbers in the young rat thalamus: a search for control factors.

Numbers of mast cells within brain space can be influenced by exposures to weak, complex magnetic fields. The present studies were designed to help isolate the factors that control numbers of mast cell within the thalamus (n=96) of 15 and 20 day old rat pups. In Experiment I, rat pups were injected daily with either 1 microliter/g or 10 microliter/g of either distilled water, isotonic saline or 0.5 M saline; another group served as controls. The numbers of thalamic mast cells did not differ significantly between the four groups. In Experiment II, that employed a cross-fostering, split litter design, the rats whose mothers had consumed 0.9% taurine during pregnancy contained about twice as many mast cells within the thalamus compared to controls. Fifteen day old pups that had been reared by other mothers showed more mast cells than those reared by their own mothers. There were negative correlations (-.60) between the numbers of mast cells within the leptomeninges of the pups and the mothers' ovarian weights but no significant associations between the numbers of mast cells within the brains of the pups and the mothers.

Animals↗

PubMed2001

Suppression of analgesia in rats induced by morphine or L-NAME but not both drugs by microTesla, frequency-modulated magnetic fields.

In Experiment I, the nociceptive threshold for a criterion response to thermal stimuli (hot plate) for rats was obtained following injections with one of various dosages of either morphine or the nitric oxide synthase inhibitor, L-NAME. On the bases of these results, rats in Experiment II were injected with either morphine (4 mg/kg), L-NAME (50 mg/kg), both morphine and L-NAME, or saline after baseline measurements for nociception and then exposed to either a 1 microTesla magnetic field or to a sham field for 30 min. The magnetic field, presented once every 4 sec, was a frequency-modulated pattern whose pixel durations, for each of the 837 successive values, were 1 msec. Nociceptive thresholds were measured immediately after the exposure and 30 min later. The results indicated that exposure to this magnetic field abolished the analgesic effects of morphine or L-NAME when injected separately but not when injected together relative to rats that had received these drugs and had been exposed to the sham field.

Analgesia↗

PubMed2001

Decreased density of neurons in the medial preoptic nucleus and increased testicular weights for rats exposed perinatally to an 0.5 Hz Rotating Magnetic Field.

Pregnant Wistar rats were exposed to either 0.5 Hz Rotating Magnetic Fields (50 microT to 300 microT or 1.5 mT to 3.0 mT) or to sham field or control environments for 3 days before to 3 days after the day of birth. The adult male offspring that had been exposed perinatally to the RMF displayed significantly heavier testicle weights but fewer neurons within the medial preoptic nucleus (MPO) and caudal ventromedial hypothalamus relative to sham field controls (effect size about 30%). There was no statistically significant difference between the two ranges of RMF intensities for these measures. RMF-exposed rats relative to sham-field exposed rats did not differ with respect to spleen weights, body weights, or mounting (reproductive) activity. The heavier testicle weights replicated previous studies and suggest that permanent, selective alterations in neuronal density can also occur subsequent to perinatal exposure to relatively weak, extremely low frequency magnetic fields.

Animals↗

PubMed2001

Synchronized feeding as a "conditioned stimulus" for overt seizures in chronically (limbic) epileptic rats: a model for "psychogenic seizures" with complex partial epilepsy.

Chronic limbic epilepsy was induced in male albino rats by a single systemic injection of lithium (3 mEq/kg) and pilocarpine (30 mg/kg). During the subsequent months the numbers of spontaneous, paroxysmal stereotyped episodes (analogous to Racine stages 4 and 5) were monitored. The numbers of these "overt seizures" increased within 10 min of the daily presentation of a food stimulus even though food was available ad libitum. The majority of the paroxysmal, stereotyped behaviours occurred within 1 min of the stimulus presentation; they were attenuated by oral prednisolone. Three rats displayed evidence of "conditioned seizures" to specific stimuli. The results suggest that the display of these behaviours can be synchronized and learned in contexts that are associated with the release of CRF (corticotrophin releasing factor) and may involve the disinhibited activity within the central amygdaloid nucleus of these rats. Implications for the occurrence of psychogenic seizures in patients with complex partial (limbic) epilepsy are discussed.

Animals↗

PubMed2001

Experimental production of illusory (false) memories in reconstructions of narratives: effect size and potential mediation by right hemispheric stimulation from complex, weak magnetic fields.

This experiment was designed to discern the proportion of false, inferential and verbatim memories that would be included in the reconstruction, one week later, of a 5 min narrative containing ambiguous but emotional content about a little boy. After 48 subjects were administered Spiegel's Hypnosis Induction Profile, they listened to the narrative, were exposed to one of four applications of transcerebral weak, complex magnetic fields for 30 min and then given either an accurate or inaccurate short summary of the story. One week later the group who received the erroneous summary reported more false memories about the original story than did the reference group; this treatment accommodated about 40% of the variance in numbers of false memories. Only an indicator of electrical lability within the temporal lobes (but not hypnotizability) was strongly associated with the numbers of inferential memories but not the numbers of false memories. The group that received transcerebral stimulation over the right hemisphere by a complex magnetic field and the erroneous summary reported three times the numbers of false memories compared to the other groups. Whereas verbatim memories showed a strong primacy effect inferential memories exhibited a strong recency effect (eta(2) =.66).

Adult↗

PubMed2001

Normal spatial memory following postseizure treatment with ketamine: selective damage attenuates memory deficits in brain-damaged rodents.

Within 30 min after the initiation of status epilepticus (SE) by lithium and pilocarpine, rats were injected with either acepromazine or ketamine. Compared to the rats that had received the acepromazine, the group that had received the ketamine displayed more accurate spatial memory. Their scores did not differ significantly from normal (non-seized) controls. Although the ketamine treatment did not significantly change the amount of neuronal loss within about 100 Paxinos and Watson structures, it was neuroprotective for several structures within the thalamus and portions of the temporal and parietal cortices. Ketamine-treated rats, however, displayed markedly more damage within the entorhinal cortices and amygdalohippocampal area.

Acepromazine↗

PubMed2000

Differential effects of low frequency, low intensity (<6 mG) nocturnal magnetic fields upon infiltration of mononuclear cells and numbers of mast cells in Lewis rat brains.

Immediately after inoculation to induce experimental allergic encephalomyelitis, 64 female Lewis rats were exposed to either a reference condition (<10 nT) or to one of two frequencies (7 Hz, 40 Hz) of magnetic fields whose two intensities (either 50 nT or 500 nT) were amplitude-modulated for 6 min once per hour between midnight and 8 h for 15 nights. Rats that had been exposed to the 7 Hz, low intensity fields displayed fewer numbers of foci of infiltrations of mononuclear cells compared to all other groups that did not differ significantly from each other. Rats exposed to the 5 mG (500 nT), 40 Hz magnetic fields displayed more foci in the right thalamus while those exposed to the 5 mG, 7 Hz fields displayed more foci in the left thalamus. Numbers of mast cells within the thalamus were also affected by the treatments. These results suggest that weak magnetic fields can affect the infiltration of immunologically responsive cells and the presence of mast cells in brain parenchyma. Implications for the potential etiology of 'electromagnetic sensitivity' symptoms are discussed.

Animals↗

PubMed2000

Temporal changes in neuronal dropout following inductions of lithium/pilocarpine seizures in the rat.

Estimates of neuronal dropout for approximately 100 structures as defined by Paxinos-Watson were completed for brains of male Wistar albino rats between 1 and 50 days after status epilepticus was evoked by a single systemic injection of lithium and pilocarpine. Sample estimates of neuronal loss were strongly correlated with direct measures of cell density. The most extensive immediate damage occurred within the substantia nigra reticulata, CA1 field of the hippocampus, the piriform cortex and the reuniens and paratenial nuclei of the thalamus. Neuronal dropout continued in many other structures over a 50-day period. Structures that showed the greatest 2-deoxyglucose (2-DG) uptake during discrete seizures and waxing and waning seizures within the early stages of status epilepticus but the least 2-DG uptake at the time of late continuous spiking and fast spiking with pauses [Neuroscience 64 (1995) 1057, 1075] exhibited the most neuronal dropout. Relationships between the delay of injection of acepromazine (which facilitated survival) and the amount of damage suggested that the source of the process that results in permanent brain damage may originate within the region of the piriform cortices and its subcortices.

Animals↗

PubMed2000

Suppression of experimental allergic encephalomyelitis is specific to the frequency and intensity of nocturnally applied, intermittent magnetic fields in rats.

Female Lewis rats (n=72) were inoculated with an emulsion of spinal cord and complete Freund's adjuvant. They were then exposed for approximately 6 min every hour between midnight and 08:00 h for 2 weeks to either 7 or 40 Hz amplitude-modulated magnetic fields whose temporal pattern was designed to simulate a (geomagnetic) storm sudden commencement. The peak strengths of the fields averaged between either 30-50 nT (low intensity) or 500 nT (high intensity). Rats exposed to the 7 Hz, low intensity magnetic fields displayed significantly less severe overt signs of experimental allergic encephalomyelitis than rats exposed to either of the two intensities of the 40 Hz fields, the high intensity 7 Hz field, or the reference (<10 nT) condition. The latter groups did not differ significantly from each other. Predicted severity based upon the numbers of foci of infiltrations of lymphocytes within the brains of the rats also demonstrated the ameliorating effects of the low intensity, 7 Hz exposures. These results suggest very specific characteristics of complex, weak magnetic fields within the sleeping environment could affect the symptoms of autoimmunity.

Animals↗

PubMed2000

Exposure to a theta-burst patterned magnetic field impairs memory acquisition and consolidation for contextual but not discrete conditioned fear in rats.

Preceding or immediately following fear-conditioning rats were exposed for 30 min to either a sham field, one of two symmetrical (sine-wave 7, 20 Hz) magnetic fields or to one of two complex magnetic fields whose waveforms were modeled after salient electrophysiological patterns within either the hippocampal formation (theta-burst) or the amygdaloid complex (burst-firing). The magnetic fields were presented in successive 2s intervals through each of the three spatial planes and then simultaneously within all three planes. Field strengths ranged between 0.5 and 1 microTesla. Only the group exposed after the conditioning to the theta-burst (hippocampal) magnetic fields displayed evidence of forgetting, as inferred by their marked attenuation of freezing behavior, during contextual extinction 24h later. This powerful treatment explained 75% of the variance in the extinction scores. Behavioral responses to the discrete conditioned stimulus were not affected. These findings are consistent with the involvement of the hippocampus in learned fear to contextual stimuli but not to discrete auditory stimuli and suggest that physiologically relevant stimuli may be delivered to the brain by weak, complex magnetic fields whose intensities are ubiquitous within modern environments.

Acoustic Stimulation↗

PubMed2000

Cattell 16 personality profiles of patients following closed-head injuries.

The personality scores from Cattell's 16 PF for 188 patients who had been referred for neuropsychological assessment following motor vehicle incidents were analyzed as a function of the severity of neuropsychological impairment (Halstead-Reitan Index) and time since the injury. Patients who were impaired (Index > 0.4) exhibited lower scores on Factor B (moe concrete thinking), Factor E (more submissive), and Factor F (more cautious) than patients who were not impaired. The presence of impairment accommodated only 10% of the variance in Factor E scores, associated with the largest group difference. There were no significant differences between scores on any of the personality factors, verbal intelligence, or standardized reading ability as a function of time since the injury.

Accidents, Traffic↗

PubMed2000

Subjective improvement following treatment with carbamazepine (Tegretol) for a subpopulation of patients with traumatic brain injuries.

Over a 3-yr period, 19 patients who had sustained brain traumas during motor vehicle incidents and who exhibited abnormal scores for a dichotic word-listening task and Roberts' Epileptic Spectrum Disorder Inventory more than one year after the injury were recommended for treatment with carbamazepine (Tegretol). The psychiatric profile of these patients, as defined by the Minnesota Multiphasic Personality Inventory, was similar to the profile of patients from other studies who had displayed more objective improvement following this treatment. Of the 14 patients 12 who followed the recommendation retrospectively reported that within a few weeks after treatment they experienced marked reductions in the incidence of sudden confusion and depression, increased attention and focus, and either elimination or attenuation of an aversive sensed presence. Such results suggest that many of the debilitating symptoms that persist for months to years after a traumatic brain injury may be electrical in nature rather than due to "psychological responses" and might be treatable by appropriate dosages of carbamazepine or other, e.g., Gabapentin (Neurontin) antiepileptic compounds.

Accidents, Traffic↗

PubMed2000

Experimental simulation of a haunt experience and elicitation of paroxysmal electroencephalographic activity by transcerebral complex magnetic fields: induction of a synthetic "ghost"?

To test the hypothesis that experiences of apparitional phenomena with accompanying fear can be simulated within the laboratory, a 45-yr.-old journalist and professional musician who had experienced a classic haunt four years previously was exposed to 1 microTesla, complex, transcerebral magnetic fields. Within 10 min. after exposure to a frequency-modulated pattern applied over the right hemisphere, the man reported "rushes of fear" that culminated in the experience of an apparition. Concurrent electroencephalographic measurements showed conspicuous 1-sec.-to-2-sec. paroxysmal complex spikes (15 Hz) that accompanied the reports of fear. A second magnetic field pattern, applied bilaterally through the brain, was associated with pleasant experiences. The subject concluded that the synthetic experience of the apparition was very similar to the one experienced in the natural setting. The results of this experiment suggest that controlled simulation of these pervasive phenomena within the laboratory is possible and that this experimental protocol may help discern the physical stimuli that evoke their occurrence in nature.

Brain↗

PubMed2000

Delayed left ear accuracy during childhood and early adolescence as indicated by Roberts' Dichotic Word Listening Test.

A total of 200 girls and boys between the ages of 6 years and 15 years were administered Roberts' Dichotic Word Listening Test. A statistically significant relatively abrupt and maintained increase in left ear accuracy was noted after 9 years of age (eta = .55). Except for a mild improvement after 6 to 7 years of age, comparable changes were not observed for the right ear. The magnitude of the effect was not significantly diminished even after covariance for verbal fluency and semantic categorization. These results are compatible with the observations that myelination of the cerebral commissures and electroencephalographic phase relations of the right hemisphere achieve near-adult characteristics after 9 years of age. Boys displayed less accuracy for dichotic word listening, particularly for the left ear, compared to the girls eta = .20).

Adolescent↗

PubMed2000

Right to left hemispheric shift in occipital electroencephalographic responses to repeated Kimura figures.

Gordon and Carmon (1976) reported that repeated presentations of an initially novel stimulus were associated with a transfer of cerebral dominance over time (trials) from the right to the left hemisphere. To test the generalizability of these results the proportions of alpha rhythms over the left and right occipital and parietal lobes were measured following the presentation of recurring and nonrecurring complex visual patterns (the Kimura Figures) to the upper or lower, left or right peripheral visual fields. Analysis showed increased electrical activation (as inferred by attenuated proportions of alpha rhythms) of the left occipital lobe but decreased activation of the right occipital lobe. This shift occurred during repeated presentations of the same stimuli but not during single presentations of different novel stimuli. There was no significant shift in this activity over the parietal lobes. These results are consistent with the reports of other researchers who have found a shift of dominant neuroelectrical activity from the right to the left hemisphere as the novelty of a visuospatial stimulus decreases.

Adult↗

PubMed2000

"Prefrontal deficits" discriminate young offenders from age-matched cohorts: juvenile delinquency as an expected feature of the normal distribution of prefrontal cerebral development.

A total of 36 male adolescent delinquents and 19 age-matched students from a male secondary school were administered several different performance-based tests. Although estimates of intelligence did not differ significantly between the groups, the incarcerated delinquents displayed more impulsivity, lower conceptual level, less conceptual flexibility, and poorer critical thinking than the reference group. The linear combination of only three variables, critical thinking, conceptual level, and numbers of errors during a conditioned spatial association task, correctly classified 89% of the 55 subjects. The results were considered consistent with the hypothesis that delayed or different development of complex functions associated with the left and (particularly) the right prefrontal cortices and their limbic inputs may be responsible for antisocial behavior. This variation will always be present due to the statistical variations in ontogeny and less than optimal parental structure within a consistent but small proportion of any generational cohort.

Adolescent↗

PubMed2000

Pretraining exposure to physiologically patterned electromagnetic stimulation attenuates fear-conditioned analgesia.

The effect of weak electromagnetic stimulation on the emergence of conditioned analgesia was examined in the adult rat. Subjects were conditioned to associate a continuous 20 kHz ultrasonic tone (CS) with 0.2 mA footshock (UCS-) over five successive days. For 30 min either before or after conditioning sessions, rats were exposed to sham or pulsed (primed burst potentiation) magnetic fields (500 nT). At the end of the conditioning phase, all animals were evaluated for anticipatory analgesia following CS presentation using a hotplate analgesiometer. Data analysis suggested a statistically significant attenuation of fear-conditioned analgesia in rats exposed to electromagnetic stimulation prior to conditioning, whereas post-conditioning exposure potentiated the reduction in pain sensitivity compared to baseline measures. The present results suggest that the emergence of fear-conditioned responses is sensitive to whole body exposure to a magnetic field pattern that has been shown to induce long-term potentiation in hippocampal slices.

Analgesia↗

PubMed2000

Suppression of experimental allergic encephalomyelitis in rats exposed nocturnally to magnetic fields.

After inoculation with spinal cord and complete Freund's adjuvant, female Lewis rats were exposed to weak, 7 Hz complex magnetic fields or to the control condition. The computer-generated magnetic field, whose amplitude varied from 15 nT to 60 nT every 6 to 12 sec, was presented for 6 min every hour between midnight and 0800 of the scotophase. In two replicates of the experiment, the rats exposed to the field displayed statistically significant suppression relative to sham-field controls (effect size = 55%) of the overt symptoms of experimental allergic encephalomyelitis which included hindleg paralyses.

Animals↗