Functional Differences Between Members of the P300 Complex: P3e and P3b

The main findings of this study bear upon differences in the functional roles of P3b and a shorter latency, more centrally distributed endogenous positive component denoted as P3e. At the present writing, we have observed P3e only in conjunction with P3b. As in the case of P3b, P3e is fully endogenous in that it can be- elicited by omission of a stimulus if stimulus omission conveys relevant information to the subject. It was found that P3e and P3b relate differently to information delivery. Information delivery was manipulated by varying event probabilities and the discriminability of the events. The well known properties of P3b, namely that its amplitude is large when elicited by low probability (high information content) events and is reduced by perceptual difficulty (information loss-equivocation), were replicated in the current study. In contrast to P3b, variation of event probability had no effect upon P3e amplitude, but increased perceptual difficulty markedly reduced P3e amplitude. In addition, two CNV-type negativities were observed in the epochs prior to presentation of the informative signal event: 1) A negativity that was maximal over central scalp related to the subject's prediction that a rare or frequent event would be presented; 2) A negativity that was maximal over occipital scalp related to a stimulus that informed the subject whether the subsequent discrimination of the signal would be easy or difficult. Finally, there was a serendipitous Hading of an apparently new short duration component, tentatively labeled Px, which is elicited by presentation of the signal that informs the subject whether the subsequent discrimination will be easy or difficult.     

Contingent Negative Variation Audiometry in Children

The aim of the present work was to establish whether contingent negative variation audiometry (CNV-A) is applicable to children. In a group of 23 children aged 5-7 years, only 10 generated clearly recognizable CNV when tested with the method successfully used in adults. When the procedure was modified by prolonging the S₁-S₂ interval and by introducing attractive slides to serve as the S₂ stimulus and by adopting a slower repetition rate, 9 children randomly selected from the former group generated high-amplitude CNV (10.1 ± 4 μV). The CNV-A measurements involving a longer auditory stimulus (S₁), lasting nearly to the beginning of S₂, and an even slower repetition rate were equally successful in 18 children aged 3-5 years, who generated CNV with an average amplitude of about 9 μV (range 5-15 μV). We believe that the basic problem of successful CNV recording in children is to attract their attention to the signals of the CNV paradigm. The child's attentiveness decreases rapidly. The mean difference and the absolute mean difference between the subjective hearing threshold for white noise and the perception threshold for white noise as determined by CNV-A were as follows: 8.8 ± 8 dB (both values) for the older group, and 3 ± 10.4 and 8.6 ± 6.5 dB, respectively, for the younger group. These differences are quite comparable to those obtained in adults. We therefore believe that CNV-A, used in combination with the behavioral method, provides a most reliable estimate of the child's hearing threshold in dubious situations.

Le but de ce travail était l'étude de l'audiométrie à variation contingente négative (A-VCN) chez l'enfant. Avec la méthode A-VCN habituellement utilisée chez l'adulte, nous n'avons obtenu de réponse nette que chez 10 enfants sur 23 aˇgés de 5 à 7 ans. En modifiant la méthode (en prolongeant l'intervalle S₁-S₂, en introduisant des diapositives intéressantes en tant que S₂ et en ralentissant le rythme de répétition), chez 9 enfants sélectionnés au hasard, tous ont présenté des réponses VCN de grande amplitude (10,1 ±4 μV). Dans un groupe de 18 enfants plus jeunes (entre 3 et 5 ans), la méthode utilisant des stimulations auditives (S₁) prolongées presque jusqu'au début de S₂ à un rythme de répétition plus lent a également fourni des réponses VCN d'amplitude moyenne d'environ 9 μV (5-15 μV). Nous croyons que la question essentielle pour obtenir des réponses VCN nettes est celle du paradigme de stimulation. La réponse décroiˇt d'habitude rapidement; ainsi ne peut-on moyenner qu'une douzaine de réponses entre 5 et 7 ans, seulement environ 9 entre 3 et 5 ans. La différence moyenne et la différence moyenne absolue entre le seuil subjectif d'audition du bruit blanc et le seuil de perception du bruit blanc déterminé par l'A-VCN ont été les suivantes: 8,8 ± 8 dB (pour les deux) dans le groupe plus aˇgé et 3 ± 10,4 dB et 8,6 ± 6,5 dB, respectivement, dans le groupe le plus jeune. Ces différences sont comparables à celles relevées chez les adultes. En conséquence, nous pensons que l'A-VCN, utilisée en combinaison avec les méthodes comportementales, fournit l'estimation la plus fiable des seuils auditifs des enfants dans les cas douteux.     

Slow cortical potentials in migraine families

Amplitude and habituation of event-related potentials are abnormal in migraine. We investigated 43 migraine and 41 healthy families to evaluate the influences of age, sex and familial contribution on the variance of amplitude and habituation of the contingent negative variation (CNV). Analysis of individual differences in relation to the CNV habituation was performed. The study demonstrated that habituation of the early CNV component characterizes migraine considerably better than the CNV amplitudes. Habituation, however, is strongly influenced by age. Migraine adults and children generally showed reduced habituation. Surprisingly, more than 30% of the healthy adults demonstrated a marked loss of habituation. The reduced CNV habituation represented a high sensitivity but low specificity to migraine, especially in children. CNV amplitude and habituation parameters revealed a considerable familial contribution associated with migraine. No familial influence on either morphology or habituation of the CNV in healthy families or between healthy members of migraine families was observed. The low specificity and familial transmission of CNV parameters in members of migraine families suggest that increased amplitudes and reduced habituation of CNV do not constitute a primary risk factor for migraine, but rather represent a predisposition. Genetic components probably affect variation of the CNV amplitude and habituation.     

Latent inhibition effects reflected in event-related brain potentials in healthy controls and schizophrenics

The present study examined the effects of pre-exposure of an irrelevant stimulus on reaction time and the contingent negative variation (CNV) in healthy controls and schizophrenic patients. In Phase I, subjects were either pre-exposed (PE) or not pre-exposed (NPE) to repeated presentations of an auditory probe stimulus (white noise), while engaged in counting auditory nonsense syllables. In Phase II, all subjects were required to produce a rapid motor response to a visual imperative stimulus that was preceded by the previously irrelevant auditory stimulus. During Phase II in controls, for PE as compared to NPE subjects, the build-up of CNV across trials was delayed. In schizophrenics, for both PE and NPE subjects, there was no pre-exposure effect on the CNV component. These findings indicate that ERPs may be useful in explicating the normal latent inhibition effect (poor associative learning to a stimulus after it has been passively pre-exposed) and its disruption in schizophrenia.     

姜黄素抑制视网膜新生血管的实验研究

目的:观察姜黄素对视网膜新生血管的抑制作用.方法:高氧诱导幼鼠建立视网膜新生血管模型.治疗组玻璃体腔注射姜黄素;对照组注射等量生理盐水.组织切片计数突破视网膜内界膜血管内皮细胞核;免疫组化检测视网膜VEGF的表达.结果:治疗组视网膜新生血管数减少,视网膜VEGF表达较对照组明显减少,两者差异显著.结论:姜黄素可以有效抑制视网膜新生血管(CNV)形成.     

Further Conclusions Regarding The Influence Of Ward Meaning On The Cortical Averaged Evoked Response In Audiology

The influence of meaning of words and meassages was studied in relation to the auditory evoked response produced by computer-averaged EEG studies.

The basic method used was the comparison of latency and amplitude of evoked response to 64-word messages played forwards to the subject, and then with each word reversed.

Several series of variations on this method were used, e.g. with alternation of ‘words forward’ and ‘words reversed', then random groups of forward and reversed words. Spoken number series were used, and varied with ‘reversed word’ patterns in a similar way.

Several methods of synchronisation of word tapes with initiation of computer-averaging were used and compared, e.g. with a short tone, and a longer tone, on the other track of a two-track tape recorder. Also a synthetic message composed of words shown on the spectrograph to have symmetrical rise and fall times was recorded and relayed to subjects in forward and reversed form.

The effect of reversal on the word message was always the same, i.e. a reduction of amplitude of evoked response, defined as the difference in microvolts between the potentials of the N₁ and P₂ waves. Latency was not affected in this way, though there was considerable inter-subject variation.     

Ketorolac inhibits choroidal neovascularization by suppression of retinal VEGF

We assessed the effect of topical ketorolac on laser-induced choroidal neovascularization (CNV), measured retinal PGE₂ and VEGF levels after laser treatment, and determined the effect of ketorolac on PGE₂ and VEGF production. Six laser burns were placed in eyes of rats which then received topical ketorolac 0.4% or artificial tears four times daily until sacrifice. Fluorescein angiography (FA) was performed at 2 and 3 weeks and retinal pigment epithelium-choroid-sclera flat mounts were prepared. The retina and vitreous were isolated at 1, 3, 5, 7, and 14 days after laser treatment and tested for VEGF and PGE₂. Additional animals were lasered and treated with topical ketorolac or artificial tears and tested at 3 and 7 days for retinal and vitreous VEGF and PGE_2. Ketorolac reduced CNV on FA by 27% at 2 weeks (P < 0.001) and 25% at 3 weeks (P < 0.001). Baseline retina and vitreous PGE₂ levels were 29.4 μg/g and 16.5 μg/g respectively, and reached 51.2 μg/g and 26.9 μg/g respectively, 24 h after laser treatment (P < 0.05). Retinal VEGF level was 781 pg/g 24 h after laser treatment and reached 931 pg/g by 7 days (P < 0.01). Ketorolac reduced retinal PGE₂ by 35% at 3 days (P < 0.05) and 29% at 7 days (P < 0.001) and retinal VEGF by 31% at 3 days (P = 0.10) and 19% at 7 days (P < 0.001). Topical ketorolac inhibited CNV and suppressed retinal PGE₂ and VEGF production.     

Regenerative Nanomedicine for Vision Restoration

Herein, we discuss recent applications of nanotechnology to ophthalmology, including nanoparticles for drug, gene, and trophic factor delivery; regenerative medicine (in the areas of optogenetics and optic nerve regeneration); and diagnostics (eg, minimally invasive biometric monitoring). Specific applications for the management of choroidal neovascularization, retinal neovascularization, oxidative damage, optic nerve damage, and retinal degenerative disease are considered. Nanotechnology will play an important role in early- and late-stage interventions in the management of blinding diseases.