Acute sleep deprivation reduces amygdala-kindled seizure thresholds in cats

It is well known that sleep loss activates human and experimental epilepsy. Because sleep deficits are also common among epileptics, it is possible that sleep loss enhances seizures by worsening these spontaneous sleep abnormalities. We examined this hypothesis by documenting the effects of acute (72 h) sleep deprivation on seizures in fully kindled cats. We have reported elsewhere sustained decrements in both slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep with the development of amygdala kindling in this species. In the present experiment, eight cats underwent an A₁ B₁ A₂ paradigm in which sleep state physiology (12-h polygraphic recordings) and seizure thresholds were examined in both an experimental (sleep deprivation) and control (nonsleep deprived) sequence of conditions, with order of presentation counterbalanced. Sleep deprivation was produced by a modification of the “flower pot” procedure and involved placing the cat on a small platform over water so as to prevent REM sleep. In the control sequence, cats underwent the same procedure except the platform was large enough to allow normal SWS and REM sleep. A significant reduction in both REM and SWS sleep occurred exclusively during the experimental B₁ condition and was accompanied by a significant reduction in seizure threshold for partial or generalized tonic-clonic convulsions. These findings indicated that this procedure, thought to influence only REM sleep, also disrupts SWS; further, this generalized disruption of sleep reduced kindled seizure thresholds, perhaps by compounding existing sleep deficits. Collectively, these observations again suggest that the integrity of both SWS and REM sleep may be an important consideration in the etiology of amygdala-kindled seizures.     

Respiratory-related heart rate variation during sleep and waking states in cats

Respiratory-related heart rate variation was examined during sleep and waking in cats with time series analysis techniques. Extent (magnitude) and coherence (degree of correlation between heart rate variation and respiratory activity) were calculated from cardiac and respiratory activity spectra. State-related differences in extent and coherence were found. Coherence appeared to be the most appropriate indicator of respiratory arrythmia differences between sleep and waking states. Overall coherence was greatest during quiet sleep, least during quiet wakefulness, and intermediate during rapid eye-movement sleep. Overall extent was also greatest during quiet sleep and least during rapid eye-movement sleep and quiet wakefulness.     

Electrofunctional features of the tilted disc syndrome

The ERG, EOG and VEPs of 15 patients with tilted disc syndrome were studied. The ERG showed abnormal amplitudes in about 1/4 of the eyes and the EOG values were pathological in 3 patients. It is probable that the abnormality of the inferiornasal portion of the retina and retinal pigment epithelium seen in the tilted disc syndrome causes the changes in the ERG and EOG. Pattern VEPs latency was delayed in most patients. This finding is probably due to the poor focusing of the light in the retina.     

Different cortical potentials preceding self-paced and visually initiated hand movements and their reciprocal transition in the same monkey

With chronically implanted electrodes on the surface and in the depth of the cortex, field potentials preceding hand movements initiated at self-pace and by visual stimulus were recorded from the premotor cortex and the forelimb areas of motor and somatosensory cortices of the same monkey. A monkey trained with either self-paced or visually initiated movement of a common motor performance revealed the premovement cortical potentials characteristic of the movement, which were markedly distinguishable between the differently initiated movements. When a monkey well-trained with one of the two movements was subsequently trained with the other, it still showed the premovement cortical potentials characteristic of the previous movement at an early stage of training and then later came gradually to reveal the premovement potentials characterized with the latter movement. After sufficient sequential training with each type of movement, the monkey was able to elicit the two kinds of premovement cortical potentials respectively on self-paced and visually initiated movements in successive sessions of the same day. We suggest that the central nervous mechanisms (programs) of preparing self-paced (“voluntary”) and visually initiated (reaction) movements with a common motor performance are very different in the same monkey, and that they can be switched from one to the other after the mechanisms have been reliably established by sufficient training with the two types of movements.     

Eye blinking and rapid eye movement: Pulsed photic stimulation of the brain

Abnormalities of blinking observed in patients with parkinsonism and schizophrenia led to this examination of spontaneous blinking in a number of mammalian species. Spontaneous blink rate, like the duration of rapid eye movement (REM) sleep, is relatively constant for each individual and species. Significantly higher blink rates were found in diurnally active animals than in nocturnal species. In contrast, REM durations are significantly longer in nocturnally active mammals. This observation led to the hypothesis that blinking during waking and REM during sleep may both serve to periodically excite the visual pathway. This hypothesis was tested by recording multipleunit activity and evoked potentials elicited by blinking and REMs in day-light and darkness from cats bearing chronically implanted electrodes in visual cortex and subcortical nuclei of the visual pathway. Both blinking and REMs evoked light-modulated potentials in the primary visual pathway and in the suprachiasmatic nucleus and medial terminal nucleus of the accessory optic tract, regions which have been implicated in photic regulation of biological rhythms.     

Unit activity related to head and eye movements in central thalamus of cats

Single-unit activity was recorded with stereotaxically guided microelectrodes in the central thalamus of five alert cats. The animals were studied with the head either fixed or free to move in a horizontal plane. They were trained to make eye and/or head movements toward discrete visual targets presented on a screen. Unit activity was analyzed in relation to triggered and spontaneous gaze displacements with head fixed and free successively. Four groups of cells were found, all within the thalamic internal medullary lamina: 20 cells were active with eye but not head movements, 49 with head but not eye movements, 36 with head or eye movements, and 17 responding to visual stimuli in the absence of movement. The patterns of firing during gaze shifts are described. It is hypothesized that eye- or head-related units carry a signal representing gaze driving.     

Firing rates and patterns of output and nonoutput cells in cortical areas 5 and 7 of cat during the sleep-waking cycle

The rate and patterns of spontaneous discharge in output cells and putative interneurons of cortical areas 5 and 7 were analyzed in the behaving cat during wakefulness (W), synchronized (S) sleep, and desynchronized (D) sleep, with (D+) and without (D−) rapid eye movements (REMs). Output cells were antidromically identified following stimulation of the thalamic and pontine nuclei. Interneurons were inferred from their thalamically elicited synaptic responses consisting of high-frequency spike barrages. Non-parametric (rank) statistics were used for tests of significance. A method derived from the Wilcoxon rank tests was developed to permit some statistical testing between interspike interval histogram patterns. Rate analysis showed that output cells discharge in all states of the sleep-waking cycle at significantly higher rates than interneurons. Corticothalamic and corticopontine cells decreased firing rates from W to S sleep and reached maximal rates in both (D+ and D−) substates of D sleep. In contrast, interneurons increased firing rates from W to S sleep and had their highest rates in D sleep, selectively occurring during REM epochs. In output cells, pattern differences between states consisted essentially of: (a) more short and long interspike intervals in S sleep compared to W, which indicates an increase in the burst-silence pattern in S sleep; (b) more short, but less long, intervals in D sleep, compared to both W and S sleep, which results from tonic excitation during D sleep and indicates that the firing pattern in D sleep is not an extreme type of S sleep. Compared to output cells, interneurons in all states had more short and long intervals and a significantly higher probability of spike bursts. The REM-related firing of interneurons may be related to recent investigations suggesting the consolidation of memory traces during D sleep.     

正常人眼电图的特征

目的:探讨正常人眼电图(electrooculogram,EOG)的特征,以获得正常参考值.方法:应用法国Metrovision公司生产的Vision Monitor视觉诱发系统对正常成人60例(73眼)在自然瞳孔下进行EOG检查.结果:正常成人EOG的暗谷电位为(701.8±265.1)μV,光峰电位为(1255.0±447.7)μV,Arden比(光峰电位/暗谷电位)为180%±21%.结论:我们的研究基本上准确、客观的反映了正常人EOG的特征,为临床研究提供了较可靠的正常值.     

Clinical and visual electrophysiological characteristics of vitelliform macular dystrophies in the first decade of life

Purpose:To evaluate patterns of pediatric vitelliform macular dystrophy (PVMD).Methods: This is a retrospective analysis of Indian children with vitelliform macular dystrophy (VMD) presenting within the first decade of life. Records were evaluated for clinical findings, family screening, and investigative findings including optical coherence tomography (OCT), fundus autofluorescence (FAF), full-field electroretinogram (ERG) and electrooculogram (EOG). Electrophysiology was scrutinized and audited for acquisition and interpretation errors. Findings on follow-up were also recorded.Results: 46 eyes of 24 patients were included. Mean age at presentation was 7.17 ± 2.17 years. Mean follow-up duration was 1.55 ± 1.69 years. Best disease was the commonest type of VMD detected (21 patients), while autosomal recessive bestrophinopathy was seen in three cases. Mean logMAR BCVA was 0.364 which decreased to 0.402 on follow-up. Hyperopia was noted in 29 out of 46 eyes (mean being +3.87 D, range ebing +0.75 to +8.75 D). Four eyes of four children had choroidal neovascular membrane at presentation, while another child developed while in follow-up. Solid type subretinal deposit was the commonest OCT finding (n = 29/38) and central hyper FAF was the commonest pattern (n = 18/32). EOG was available for review in 32 eyes, but was unreliable in 11 eyes. Seven eyes demonstrated complete absence of light rise on EOG.Conclusion: PVMD can present in advanced forms. Progression to complications with loss of visual acuity can happen within the first decade of life. EOG shows grossly suppressed waveforms in the light phase in a large number of such children.