Matching clinical and biological specificity: implications for biological psychiatry.
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Cloning, Molecular↗
Biomedical subjects
R T Pivik
Publications and source records attributed to R T Pivik.
Smooth pursuit eye tracking dysfunction in schizophrenia: subcortical implications.
The study of smooth pursuit eye tracking behavior in schizophrenics has occupied a prominent position in the search for biological correlates of this mental illness for nearly 20 years. During this time, impairments in this behavior have been shown to be a most robust finding in these patients. Attempts to further characterize the basis for this dysfunction have emphasized the role of cortical--particularly frontal--processes in both the symptomatology of schizophrenia and the eye tracking disturbance. In the present paper, arguments are made in support of a subcortical contribution to smooth pursuit eye tracking dysfunction in schizophrenia. Supporting data include new observations of cortical EEG variations in association with pursuit tracking disruptions, and a review of recent data indicating visual-vestibular and cerebellar-vestibular influences on the tracking disturbances in these patients. On the basis of such data, it is concluded that it is highly unlikely that a single mechanism or process is exclusively responsible for impaired pursuit tracking in schizophrenics, and that there are data to support both cortical and subcortical contributions to this dysfunction.
Adult↗
Abnormal visual-vestibular interaction and smooth pursuit tracking in psychosis: implications for cerebellar involvement.
The vestibulo-ocular response to caloric irrigation and the effect of vestibular activation on eye movements were examined during light and dark testing conditions--the latter to assess these measures under conditions attenuating possible cerebellar-vestibular interaction present in the light-adapting condition. Subjects were psychiatric patients (23 actively-ill psychotic patients and 23 remitted psychotic patients) and normal controls (23 with no history of psychiatric illness). Standardized clinical electronystagmographic procedures were used, together with electrographic measures to assess visual fixation and level of arousal. During the light condition previous findings of impaired smooth pursuit tracking and reduced fixation suppression in actively psychotic patients were replicated. These patients also exhibited hyperresponsive vestibulo-ocular responses. Remitted patients' performance levels on test measures fell between those of controls and actively-ill patients on the majority of response measures. However, remitted patients were found to have impaired smooth pursuit tracking and failure of fixation suppression relative to controls. The dark testing condition effected a normalization of several patient-control differences, including smooth pursuit tracking and the elimination of vestibular hyperresponsiveness. In many respects the present results parallel findings of eye movement aberrations in cerebellar patients. These similarities include evidence of an intact but hyperresponsive vestibular system, the normalization of previously disordered pursuit tracking during dark-testing, the failure of fixation suppression, and the decrease in this measure during dark conditions. These findings suggest that cerebellar dysfunction may contribute to irregularities in smooth pursuit tracking and fixation suppression found in psychotic patients.
Adult↗
Spinal motoneuronal excitability in hyperkinesis: effects of the Jendrassik manoeuvre.
H-reflex recovery functions and homosynaptic depression curves were studied in unmedicated hyperkinetic and control children in the presence and absence of the Jendrassik manoeuvre. The Jendrassik manoeuvre failed to affect recovery function reflex amplitude across or within groups, but reflex amplitude was augmented in the homosynaptic depression procedure for hyperkinetic children who failed to show recovery function facilitation. The absence of Jendrassik-associated reflex facilitation in children during the recovery function and during selective homosynaptic depression rates may reflect developmental influences on processes underlying this phenomenon. However, reflex augmentation in non-facilitating hyperkinetic subjects suggests that these processes are present in children and can be revealed under conditions of decreased motoneuronal excitability. These findings suggest that reduced gamma-efferent drive may contribute to decreased motoneuronal excitability observed in hyperkinetic children, but the possible role of other Jendrassik-activated influences, such as coactivation of alpha and gamma motoneurons or selective activation of alpha motoneurons by processes independent of increased gamma-efferent drive, cannot be excluded.
Animals↗
The effects of background illumination and stimulant medication on smooth pursuit eye movements of hyperactive children.
Problems with visual information processing have been reported in children with the diagnosis of attention deficit disorder with hyperactivity (ADD H), and deficits in oculomotor control have been posited as an important factor in this phenomenon. To assess aspects of oculomotor performance, smooth pursuit eye movements (PEMs) were recorded electrooculographically in 20 ADD H and 20 age-matched control children and computer-analyzed for discrete (velocity arrests) and global (root mean square error) disruptions. The effects of stimulant medication (methylphenidate), together with manipulations designed to influence behavioral (attention) and physiological (cerebellar) processes involved in PEM performance, were examined. The tracking patterns of nonmedicated ADD H children contained significantly more discrete aberrations on baseline conditions. Although no single experimental manipulation significantly improved tracking performance in ADD H children, combining all experimental conditions did normalize PEMs in these subjects. Slight improvements in PEM performance in association with medication correlated positively with dose of medication and with medication-related improvements in behavior. In light of these data, arguments are presented in support of (a) hypoarousal as a contributing factor underlying oculomotor difficulties in ADD H children, and (b) subcortical involvement in PEM dysfunction.
Attention↗
Dark condition normalization of smooth pursuit tracking: evidence of cerebellar dysfunction in psychosis.
Smooth pursuit tracking performance was evaluated in psychotic (n = 20) and normal control subjects (n = 20) during light and dark testing conditions using computer-based analyses of electrographically recorded tracking patterns. Previously reported impaired tracking in psychotics tested under light conditions was reaffirmed. However, the tracking patterns of patients during the dark condition not only resembled those of controls under similar conditions, but were no longer significantly different from controls' light condition performance. Among several possible bases for these results which are considered, the involvement of cerebellar dysfunction in these patients is emphasized.
Adult↗
Personality and individual differences in spinal motoneuronal excitability.
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Adolescent↗
Variations in nuchal muscle tonus following paradoxical sleep deprivation in the rabbit.
Although tonic inhibition of nuchal or facial musculature is considered an intrinsic component of paradoxical sleep (PS) in mammals, this inhibition is either absent or greatly attenuated in the rabbit. To further explore the characteristics of this phenomenon in this species, variations in quantified nuchal muscle activity were examined before, during and following 24 h of PS deprivation. It was postulated that if the substrate for PS-associated tonic electromyogram (EMG) inhibition is present, this procedure--which is known to affect both tonic and phasic components of PS--might enhance such inhibition. For these investigations chronically implanted rabbits (electroencephalographic, eye movement and nuchal muscle placements) were recorded continuously for 5 consecutive days (two day baseline, one day deprivation, two day recovery). Muscle activity was quantified by resetting integration techniques and comparisons made of activity levels before, during and after PS episodes across conditions. The deprivation procedure significantly reduced the amount of PS relative to baseline values, and a significant PS increase (rebound) occurred during postdeprivation recordings. Across-condition EMG-related effects included the corroboration of previous reports of an absence of nuchal atonia during PS, a significant diurnal variation in EMG activity--with greater activity occurring during the dark portion of the light-dark cycle, and enhanced activity immediately following PS episodes relative to either pre-PS or PS levels. Deprivation-related changes in quantified EMG activity included a pre-PS decrease during both the last 12 h of deprivation and the initial 12 h of recovery sleep, and an enhancement of EMG activity during PS.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The effects of dark adaptation on pursuit tracking dysfunction in psychotics with impaired vestibular suppression.
Smooth pursuit eye tracking performance, evaluated by electronic processing and subjective ratings, was assessed in actively psychotic psychiatric patients and normal controls under conditions of light and dark adaptation and was related to subjects' ability to suppress vestibular nystagmus induced by caloric irrigation. Patients' tracking performance was significantly inferior during the light-adapted condition on all tracking measures. Dark-adaptation eliminated group differences based on electronic analyses, but subjective ratings--which showed a variable relationship to the other tracking measures--did not reflect this improvement. Vestibular nystagmus suppression was significantly impaired in patients relative to controls and this impairment, coupled with smooth pursuit dysfunction and marked improvement in tracking performance during dark-adaptation, suggests that cerebellar dysfunction contributes significantly to tracking dysfunction in psychotic patients.
Adult↗
Effects of paradoxical sleep deprivation in the rabbit.
The effects of nonpharmacologically-induced deprivation of paradoxical sleep for a 24 hour period were studied in rabbits. Response characteristics commonly associated with the deprivation procedure in other species were observed, as well as features apparently peculiar to the rabbit. Like other mammals, rabbits: (1) show increased attempts to experience PS during the deprivation procedure relative to the baseline occurrence of PS; (2) become increasingly difficult to arouse from PS as the deprivation period progresses; (3) show increased amounts of PS (rebound) in post-deprivation recordings relative to baseline; and (4) compensate for only one-third of the PS deficit incurred during deprivation. Rabbits' response to PS deprivation differs from other mammals in the following ways: (1) the deprivation procedure is truly selective, significantly affecting only amounts of PS and not total sleep time or other sleep stages; (2) the rebound response is restricted to the light phase of the light-dark cycle on the first recovery day; and (3) as indexed by eye movement density, phasic activity during PS is not enhanced during the recovery period. Given that the crucial factor in the PS deprivation-compensation phenomenon is thought to be the deprivation and subsequent enhanced occurrence of phasic events, and considering that events within the oculomotor system have been emphasized in this regard, the results of this investigation suggest the existence of species differences regarding the nature and form of the compensatory response to PS deprivation.
Animals↗
Sleep-wakefulness rhythms in the rabbit.
The characteristics and stability of sleep-wakefulness patterns across consecutive 24-h periods were examined in adult male rabbits implanted for chronic recording of electroencephalographic, eye movement, and nuchal muscle activities. Criteria for stage scoring along with associated scoring reliability are presented. Rabbits slept an average of 11.4 h per day, 25.9% of which was drowsy, 64.5% slow wave sleep, and 9.6% paradoxical sleep. Diurnal differences in amount and type of sleep, consisting of increased wakefulness and decreased paradoxical sleep during the dark phase of the light-dark cycle, were observed. The results are integrated with those of previous sleep studies in this species and phylogenetic implications of variations in the distribution and characteristics of sleep in the rabbit are discussed.
Animals↗
Abnormal motoneuronal excitability in hyperkinetic children.
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Action Potentials↗
Vestibular activation, smooth pursuit tracking, and psychosis.
Pursuit tracking and vestibular activation procedures were combined in an investigation to determine if smooth pursuit tracking deficits could be related to abnormalities of visual-vestibular interaction in psychiatric patients. In actively psychotic patients, but not in comparison groups of schizophrenic outpatients with remitted symptomatology or normal controls, a significant failure of visual fixation to suppress caloric nystagmus was related to a higher incidence of disordered tracking during both baseline and postirrigation conditions. Other vestibular irregularities including dysrhythmia and reduced fast phase velocity were observed in these same patients. The results are supportive of a central deficit in visual-vestibular interaction that may contribute to pursuit tracking deficits in psychosis.
Adult↗
Auditory arousal thresholds during sleep in hyperkinetic children.
Auditory arousal thresholds were determined throughout sleep (4-night protocol) in prepubertal nonmedicated and medicated hyperkinetic and normal control male children. The most striking result was the general inability to arouse children of all groups to behavioral response even at intensities up to 123 dB sound pressure level. Of total awakening attempts, 52.5% resulted in non-arousal, 13% resulted in partial, nonsustained physiological arousal responses, and 34.3% were associated with complete awakenings. A significant increase in proportion of awakenings and decrease in the frequency of nonarousals occurred across the night. The groups did not differ with respect to the number of arousal responses. Although nonmedicated hyperkinetic children tended to have lower arousal thresholds relative to children in both comparison groups, the only significant group difference was a lower threshold response in nonmedicated, relative to medicated, hyperkinetic subjects during stage 2 sleep. Arousal thresholds in hyperkinetic children receiving stimulant medication approximated those of normal control children. The enhanced sensitivity of nonmedicated hyperkinetic subjects to auditory stimuli during sleep is interpreted as indicating that processes responsible for elevating arousal threshold at this time are less effective in these children.
Arousal↗
Effects of brainstem lesions on tonic immobility in the rabbit (Oryctolagus cuniculus).
Lesions were placed in discrete brainstem areas implicated in the generation of both tonic immobility (T1) and paradoxical sleep (PS) to examine postulated state and event correspondences between these states in the rabbit. Lesions were concentrated in the region of the nucleus locus coeruleus (LC)-an area implicated in the mediation of muscular atonia during PS-but also included other reticular (pontine gigantocellular tegmental field: FTG), and nonreticular (vestibular, cerebellar, central grey, collicular) areas. Polygraphic recordings of EEG, EMG and EOG activities were taken during sleep-waking states and measures of the TI response were obtained before (1 day prior) and after (5 and 14 days) lesions were made. None of the lesions was followed by a sustained, significant variation in either frequency of induction or duration of TI. Following LC lesions, and to a lesser extent after FTG lesions, sleep patterns were fragmented, with a reduction or absence of PS and the occurrence of phasic motor activation at times when PS periods might be expected to occur. The absence of PS and persistence of TI following specific brainstem lesions indicate a fundamental difference in mechanisms underlying these states. It is suggested that a major determinant of these results is the activation of phasic activity during PS but not TI, and that the possibility remains that both states may share a common mechanism of tonic motor control.
Animals↗
Spinal motoneuronal excitability during wakefulness and non-REM sleep in hyperkinesis.
Variations in spinal motoneuronal excitability were assessed during wakefulness and non-REM sleep in hyperkinetic and normal children by determining the recovery cycle of the H-reflex following a conditioning stimulus. Reflex facilitation which generally occurs 100-300 msec after a conditioning stimulus was markedly reduced during sleep in both groups and during wakefulness as well in hyperkinetic subjects. Among possible mechanisms which might underlie the observed reductions in facilitation, emphasis is placed on decreased central excitability resulting from depressed fusimotor activity.
Attention Deficit Disorder with Hyperactivity↗
Sleep patterns in children of superior intelligence.
To examine the relationship between superior intellectual functioning and physiological patterns and events during sleep, male children (8-12 years old) of superior (mean IQ: 133.3) and average (means IQ: 111.0) intelligence were recorded for five consecutive nights using standard electrographic measures. Compared to normal controls, superior IQ subjects had greater amounts of TST, stage 2, stage 3, total NREM sleep, a longer average NREM cycle length and significantly less average REM density. In addition, significant negative relationships were obtained between full-scale IQ and REM density, and between verbal IQ and REM density. The results suggest that patterns and amounts of sleep stages in superior IQ children do not differ in any dramatic fashion from those of children with average IQ. However, the negative correlations between IQ measures and eye movement density during REM sleep are consonant with previous notions relating eye movement density to waking information processing strategies and suggest a carry-over of such strategies from wakefulness to sleep.
Child↗
Failure of high intensity auditory stimuli to affect behavioral arousal in children during the first sleep cycle.
Behavioral and physiologic indices of arousal to auditory stimuli were examined during the first cycle of sleep in 8-12-year-old hyperactive children and nonhyperactive controls. No behavioral responses or sustained awakenings were obtained for any child during the first cycle of sleep to stimuli at intensities up to 123 dB sound pressure level re 0.0002 dynes/cm2), i.e., at intensities more than 90 dB above waking threshold values. Half of the arousal attempts in stage 2 and a quarter of those in stage 4 elicited a partial or momentary physiologic arousal response (i.e., EEG desynchronization and/or change in skin potential response or respiratory activity rates). These arousals were shortlived, with the subjects returning to sleep even with continuing or increased stimulus intensity. Neither the incidence of partial arousals nor the associated threshold intensities differentiated subject groups. Although increased skin potential response activity and decreased respiratory rates were observed during sleep relative to wakefulness, and a predominance of skin potential response activity was noted in stage 4 sleep, no significant differences in frequency (rate/min) of autonomic response measures were obtained when rates before and during auditory stimulation were compared.
Acoustic Stimulation↗