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Biomedical subjects

M S Myslobodsky

Publications and source records attributed to M S Myslobodsky.

At least 19 recordsLinked to original sources
PubMed2005

Laparophobia: a cognitive perspective on appetite control in anorexia nervosa.

Decades of research have demonstrated that anorexia nervosa (AN) may be associated with aberrant cognition, yet, its role in maintaining stringent dieting has received relatively little attention from mainstream researchers of eating disorders. The purpose of the present article is to highlight cognitive ('top-down') factors that are considered responsible for anticipatory anxiety of stoutness and frank fat-phobia (laparophobia). A cognitive model proposed departs from the formulation suggesting that phobia of over-eating is superimposed on avoidant tendencies ('environmental autonomy syndrome'), whereas excessive exercising becomes a natural coping strategy with laparophobia, an instrument of reward. AN ideation involves complex neuronal circuitries and multiple neurochemical components that may conceivably represent a mirror image of those underlying obesity. The emphasis on phobia and aberrant membrane excitability akin to channelopathies behoves the clinicians to be aware of potential uses of drugs acting at the gamma-aminobutyric acid and the N-methyl-D-aspartate/AMPA [2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl) propionic acid] receptors sites as the adjuncts to conventional agents in managing AN.

Anorexia Nervosa↗
PubMed1999

Effects of prenatal exposure to gamma rays on circling and activity behavior in prepubertal and postpubertal rats.

The study departs from the finding that postural asymmetries in low-weight female neonates are greatly increased following prenatal lesions inflicted by gamma irradiation at day 15. Given that amphetamine-induced rotation in adult rats could be predicted by their infantile axial asymmetry we expected a greater tendency for circling in rats exposed at day 15. To examine this prediction, Sprague-Dawley rats were exposed to a single dose of gamma radiation at 1.5 Gy with a dose-rate of 0.15 Gy/min. The dose was delivered on one of the embryonic days (E15, 17 or 19) throughout the whole body of pregnant dams. Sham prenatal exposure of controls consisted of placing pregnant rats in the same environment for 10 min. All rats were tested during the active part of the circadian cycle. At postnatal day 27 (P27) exposed pups did not differ in rates of either spontaneous or d-amphetamine-induced circling from the shams. At P57, in keeping with our prediction, E15 rats manifested enhanced rotation and higher net asymmetry. However, E17 also showed higher gyration tendency compared to their shams while exposed E19 rats did not differ from their shams. The role of intrinsic DAergic imbalance presumably sharpened by irradiation at E15 and of neocortical deficit inflicted at E15 and E17 are discussed.

Animals↗
PubMed1998

Dissociation between startle and prepulse inhibition in rats exposed to gamma radiation at day 15 of embryogeny.

The role of prenatal trauma in disordered sensory gating was explored in albino rats of the Sprague-Dawley strain. Pregnant rats were exposed to 1.5 Gy (0.15 Gy/min) of the whole-body gamma radiation on days 15, 17, or 19 of gestation. Controls were sham-exposed during 10 min in the same conditions. Exposed and control offsprings were evaluated for the auditory startle response (ASR) and its gating by either the habituation process or by the preceding weak sensory stimulus in the prepulse inhibition of startle (PPI) procedure. The tests were conducted when the animals reached 27 and 57 days of age. A noticeable hyperresponding and delayed habituation of startle were found in rats exposed at E15, with meager effects in rats exposed at E17 and E19. Maximal deficit was obtained on tests conducted on P57 but not on P27. However, in rats pretreated with amphetamine, dysfunctional startle was unmasked already on the P27 test. By contrast, PPI was insensitive to the damaging effect of prenatal irradiation at either period. This dissociation is reminiscent of one observed in patients with posttraumatic stress disorder (PTSD).

Acoustic Stimulation↗
PubMed1997

Auditory inattention in right-hemisphere-damaged patients with and without visual neglect.

Fifteen right-hemisphere-damaged patients, eight with- and seven without visual neglect (N+ and N-, respectively), were assessed for the presence of auditory neglect using free-field bilateral simultaneous stimulation (BSS) and pseudorandom unilateral stimulation. Eight healthy subjects served as controls. Both N+ and N- groups extinguished left-sided sound stimuli in the BSS condition. N+ (but not N-) patients showed a right-side advantage in sound localization and were inferior, compared to normal individuals, in their ability to localize unilaterally administered sounds on the left side. Blindfolding significantly improved the localization performance. In a task demanding stimulus identification, both N+ and N- groups performed abnormally when auditory stimuli came from the left. Free-field stimulation is thus an adequate technique for the detection of auditory neglect. The results are consistent with the notion that left-sided neglect reflects a pathologically exaggerated attentional bias towards the right in normal individuals.

Adult↗
PubMed1996

Increased prevalence of septal cavitation in a nonschizophrenic sample: an MRI study of HIV-infected individuals.

Analyses of MRI scans of 26 asymptomatic HIV-infected individuals (HIV+) and 10 HIV-seronegative psychiatric control subjects (HIV-) revealed an incidental finding: 50% of the HIV+ subjects had discernible cleft in the septum pellucidum (cavum septi pellucidi; CSP), compared to only 20% of the HIV- control subjects. HIV+ subjects with CSP were more likely to complain of sensory changes and performed more poorly on specific neuropsychological tests when compared with HIV+ subjects without CSP. These findings suggest that elevated rates of CSP are not limited to the schizophrenic population. CSP may be a marker of premorbid events that increase the vulnerability to cognitive and perhaps behavioral sequelae of neurologic disease or injury.

Adult↗
PubMed1995

Changes of brain anatomy in patients with posttraumatic stress disorder: a pilot magnetic resonance imaging study.

No abnormalities in magnetic resonance images were recorded in patients with posttraumatic stress disorder other than an increased incidence (50%) of a small cleft in the callosal-septal interface, a cavum of the septum pellucidum. A similar grade of cavum was obtained in 14% of normal volunteers matched for age, socioeconomic background, and military experience. The cavum is believed to have antedated the disorder and is conceived to be a neurodevelopmental aberration. The possibility that the cavum is a marker of vulnerability to stress in psychopathology is discussed.

Adult↗
PubMed1995

Effects of hemi-thalamic damage on K-complexes evoked by monaural stimuli during midafternoon sleep.

Polygraphic recording of midafternoon sleep were made in two patients with unilateral hemorrhagic infarction in the thalamus. One patient had massive signs of reduced attention in the contralesional space following right lateral thalamic lesion. The other patient had infarction centered in the left posterior ventrolateral thalamus with no signs of hemineglect. In both cases, waking and sleep records showed symmetric background EEG at C3 and C4. In contrast, monaural sounds (clicks) elicited bilaterally symmetrical K-complexes only in the second patient. In the other patient with right thalamic lesion, both left- and right-ear clicks failed to elicit K-complexes in the right cerebral hemisphere, whereas normal K-complexes continued to appear at C3 as well as at Fz. In neither patient did the frequency of evoked K-complexes depend on the side of the stimulated ear. Unlike K-complexes, sleep spindles were bilaterally absent in patient 1. The right hemisphere does not seem to have a special role in control of circuits generating K-complexes.

Acoustic Stimulation↗
PubMed1995

Ventriloquist effect reinstates responsiveness to auditory stimuli in the 'ignored' space in patients with hemispatial neglect.

We examined 6 patients with robust visual neglect following right hemisphere damage. All of them had signs of auditory neglect as documented by the inferior identification of syllables delivered through a loudspeaker on the left side. When the same stimuli on the left were administered in the presence of a fictitious source of sound (a dummy loudspeaker) visible in the homolesional space, a significant increase in the identification score of sounds was obtained (the "ventriloquist" effect). The result is in keeping with a notion of a strong coupling between auditory and visual systems. The effect is attributed to the activation by the fictitious source of sound of the audio-visual map in the left hemisphere. We draw attention to the possibility that loss of awareness of auditory input may arise due to the disconnection of the visual input from the audio-visual template.

Adult↗
PubMed1994

Rotational swimming tendencies in the dolphin (Tursiops truncatus).

Anecdotal evidence suggests that dolphins placed in a pool exhibit stereotypic swimming in circles. The present study confirmed these observations in a sample of thirteen dolphins. The majority of dolphins (84.6%) showed highly consistent directional swimming in counterclockwise circles. The latter directionality held throughout the circadian cycle and resisted environmental manipulations. Only social interaction was capable of altering the directionality of circumnavigation. The consistency of unidirectional swimming is considered paradoxical in view of the existing evidence regarding the alternating of hemispheric activity in sleeping dolphins.

Animals↗
PubMed1993

Central determinants of attention and mood disorder in tardive dyskinesia ("tardive dysmentia").

The typical apathetic state of tardive dyskinesia patients may be punctuated by periods of hyperactivity, vigilance, and tension. Patients may exhibit unusual readiness for contact, even though they remain edgy, loud and loquacious, euphoric, jolly, intrusive, and invasive of the privacy of others. These features designated as "tardive dysmentia" are examined, so as to draw attention to the possibility that the syndrome of dysmentia is comprised of occasional excessive emotional reactivity, enhanced responsiveness to environmental stimuli, and indifference to or reduced awareness of the patient's abnormal involuntary movements. The pathophysiology of tardive dysmentia remains uncertain. It is proposed that behavioral changes in patients with dysmentia may be conceived in terms of a more outward direction of attentional processing. Such an immense change in psychopathology under antipsychotic drugs, from withdrawal to the emotional externalization of behavior, is conceived as reflecting a shift in the approach-avoidance behavior due to alterations in the parieto-frontal balance.

Cognition Disorders↗
PubMed1993

The representation of patterns of structural brain asymmetry in normal individuals.

Hemispheric asymmetries were examined in 20 normal individuals who underwent MR scanning. The asymmetry indices were represented for a series of contiguous, consecutive coronal images through the occipital and frontal lobes, along the dorso-ventral [DV] axis. A monotonic decrease in size of the parieto-occipital hemispheric areal asymmetry was observed, from a marked left predominance to a greater degree of symmetry. When frontal and occipital lobe asymmetries were compared, the familiar frontal-right vs occipital-left counterclockwise torque was observed, but was found to be more prominent in the dorsal aspect of the frontal cuts and the ventral aspect of the occipital cuts. At the individual level, a within-subject linear model for predicting cerebral area as a function of cut, hemisphere and DV, revealed this marked DV effect. The use of the within-subject linear model further enabled the individual assessment of structural asymmetries, and provided criteria by which subjects could be grouped. We further show how a deviation of the occipital falx will engender different hemispheric asymmetries, depending on the orientation of the coronal imaging plane. Given the latter, we recommend planning the coronal cuts based on a low-ventricular transaxial scout, wherein the deviated falx, if present, can be taken into account.

Adolescent↗
PubMed1993

Effect of nootropic Solcoseryl on kainic acid-induced excitotoxic brain injury.

Solcoseryl (S) has been shown to provide significant cytoprotection in a variety of models of cerebral hypoxia. In the present study, we quantified the epileptiform effects caused by kainic acid administered into the pontine reticular formation of rats and their response to S pretreatment. Compared to saline, the agent appeared to significantly reduce the mortality of rats in the course of status epilepticus. However, S-pretreated rats manifested an increased incidence of behavioral seizures. This untoward effect is attributed to the fact that S improves the functional potential of injured tissue and retards the period of metabolic exhaustion at a time when neuronal activity should be minimized.

Actihaemyl↗
PubMed1993

Pro- and anticonvulsant effects of stress: the role of neuroactive steroids.

The present review deals with findings related to the contribution of pro- and anticonvulsant effects of "neuroactive" steroids and the role of the gamma-aminobutyric acid (GABA) receptor as a physiological target for naturally occurring steroids. Ways are discussed via which GABAergic neurotransmission can be enhanced or reduced following maneuvers that inflict stress. The duality of stress effects is emphasized in conjunction with different types of epileptogenesis (e.g., grand mal vs petit mal) that undergo dissimilar evolution. Among the issues covered are steroid-induced sedation and epileptogenicity, excitatory steroids, stress and epilepsy, GABA and respiratory functions, asymmetric brain injury, and psychopathology and stress.

Animals↗
PubMed1992

Lipreading in patients with schizophrenia.

This study was designed to explore whether schizophrenic patients who are able to maintain their gaze with adequate persistence could competently lip-read. Four lipreading tests, designed to assess recognition of syllables, words, and overlearned sentences, were administered to 15 schizophrenic and 15 normal subjects matched for age, sex, and educational level. The patients proved to be competent lip-readers susceptible to the blend illusion and were inferior only in lipreading of overlearned sentences. The latter difficulty may tentatively be attributed to the inadequacy of the patient's premorbid social network for establishing contextual cues that aid in the recognition of overlearned sentences.

Adult↗
PubMed1991

EEG laterality in the era of structural brain imaging.

Bilateral EEG recording is a common practice when brain laterality needs to be assessed in cognitive neurophysiology and psychiatry research. Its precision and validity remain uncertain. With structural brain imaging methods, it is possible to examine EEG electrode placements according to the 10-20 system and the validity of inferences made on derived data. Frequent sources of placement errors are examined along with important factors that contribute to EEG imbalance. Examples are mentioned where asymmetries of EEG/ERP caused by cranial and parenchymal brain asymmetries may be mistaken for cognition-related laterality changes. Because external skull landmarks are not reliable predictors of cranial and parenchymal brain asymmetries, laterality assessment cannot be guaranteed by the 10-20 system. Consequently, a return, on a case-to-case basis, to nonstandard montages, assisted by structural brain imaging is seen as an acceptable alternative.

Brain↗
PubMed1991

Occipital lobe morphology in normal individuals assessed by magnetic resonance imaging (MRI).

The topography of visual evoked potentials (VEP) is dependent on occipital lobe morphology. Using magnetic resonance imaging we examine the sulcal pattern (the calcarine and parieto-occipital sulci), and assess the size of the cuneus and the asymmetry of the occipital lobes, computed separately for its ventral and dorsal segments. No differences were found for either the cuneus or the sulci pattern. In contrast, hemispheric asymmetry values appeared to be substantial. The predominance of the left occipital area was seen distinctly in the ventro-caudal portion of the occipital lobe. It was frequently reversed in the dorsal aspect of the lobe, notably in more rostral cuts. Such complexities may lead to ambiguities in interpreting VEP asymmetries.

Adolescent↗