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Relation of intensity and duration of brief retinal stimulation by light to the electrical response of the optic cortex of the rabbit
... The exigency for an exhaustive assessment of the effectiveness of alpha wave entrainment in pediatric dental contexts is further accentuated by the preliminary findings of Joyce et al., who reported positive implications of such interventions on pediatric patients' cooperative behavior during dental treatments [5,6]. These observations lay a foundational premise for the present study, which endeavors to methodically evaluate the influence of alpha wave entrainment on both male and female pediatric dental patients subjected to interventions. ...
... The examination of diastolic blood pressure (DBP) metrics within the intervention group unveiled a subtle, though not statistically significant, downward trend across genders, contrasting with the outcomes observed in the control group, aligning with the research by Barlow (1960) and Bartley (1934) [5][6]. This modest reduction in DBP (p>0.05) ...
... The examination of diastolic blood pressure (DBP) metrics within the intervention group unveiled a subtle, though not statistically significant, downward trend across genders, contrasting with the outcomes observed in the control group, aligning with the research by Barlow (1960) and Bartley (1934) [5][6]. This modest reduction in DBP (p>0.05) ...
Background
Pediatric dental anxiety is a significant barrier to effective dental care, necessitating non-pharmacological interventions. Alpha wave entrainment has shown promise in adult studies for reducing procedural anxiety and pain perception, but its effectiveness in pediatric dental settings remains underexplored.
Objective
This study aims to evaluate the effectiveness of preoperative alpha wave entrainment in alleviating anxiety in gender-specific participants to the interventions.
Methods
We conducted a randomized controlled trial involving 252 pediatric patients (aged 7-12) with cooperative dispositions. Participants were randomly assigned to either an experimental group receiving alpha wave entrainment or a control group receiving conventional behavior management techniques. The experimental intervention involved 10-minute sessions of binaural beats with visual stimulation designed to induce alpha-wave synchronization. Anxiety levels were assessed using physiological measures (heart rate and blood pressure), both pre- and post-interventions.
Results
The intervention group demonstrated a significant reduction in heart rate and systolic blood pressure post-intervention compared to the control group. These changes indicate a decrease in anxiety levels, with no significant gender differences in the response to the intervention.
Conclusion
Alpha wave entrainment effectively reduces dental anxiety in pediatric patients, with similar efficacy observed across genders. This study supports the incorporation of alpha wave entrainment into pediatric dental practices as a viable alternative to traditional anxiety management techniques.
... As an approximation, the average figure of 30 msec difference will be used for further evaluation of the present data. This figure was used by Davis (I957) and is consistent with electrophysiological measurements at primary cortical areas (Bartley, 1934;Kemp, Coppee, & Robinson, 1937) and motor cortex (Buser & Imbert, 1961). Using the 30 msec estimate, the effective interstimulus intervals as approximated by physiological time are quite different from clock time. ...
Facilitation of reaction time by a second stimulus in another sense modality than the initial signal for response extended over a longer range of interstimulus intervals when the presented sequence was visual-auditory as compared with auditory-visual. The expected difference between visual and auditory reaction times was diminished or eliminated with paired bi-modal stimuli.
... At this point several stimulation methods start operating to externally influence the EEG-patterns. The general effect of persistent audio-visual stimuli on the EEG is well known since the early days of EEG, when the alpha-band could be influenced via well targeted visual stimuli [25,26] . In principal the procedure is to expose the patient with a series of light and/or acoustical impulses and to observe the subjective-physiological or EEG-pattern changes. ...
An EEG-Based audiovisual stimulation system was tested on a group of 32 ADHD patients. The efficacy was compared in a pre- and post analysis over a treatment period of 3 month with a control group and a group of patients with an EEG-based neurofeedback therapy. The number of impulsivity errors in a stop-signal paradigm at several distinct times during and after the therapy was used as a quality marker. The main feature of this method uses real-time-EEG data derived pa-rameters for a controlled manipulation of EEG patterns with persistently strong audio-visual stimuli. It is based upon a direct feedback of changes in short-term coherences in the context of central nervous stimulus processing to control the stimulating frequency. The real-time EEG processing is done on the basis of time-dependent coherence analysis of the theta and beta band.
... At this point several stimulation methods start operating to externally influence the EEG-patterns. The general effect of persistent audio-visual stimuli on the EEG is well known since the early days of EEG, when the alpha-band could be influenced via well targeted visual stimuli [25,26] . In principal the procedure is to expose the patient with a series of light and/or acoustical impulses and to observe the subjective-physiological or EEG-pattern changes. ...
An EEG-Based audiovisual stimulation system was tested on a group of 32 ADHD patients. The efficacy was compared
in a pre- and post analysis over a treatment period of 3 month with a control group and a group of patients with an EEGbased
neurofeedback therapy. The number of impulsivity errors in a stop-signal paradigm at several distinct times during
and after the therapy was used as a quality marker. The main feature of this method uses real-time-EEG data derived parameters
for a controlled manipulation of EEG patterns with persistently strong audio-visual stimuli. It is based upon a
direct feedback of changes in short-term coherences in the context of central nervous stimulus processing to control the
stimulating frequency. The real-time EEG processing is done on the basis of time-dependent coherence analysis of the
theta and beta band.
This paper aims to explore the psychological and demographic profiles of living kidney donors in Iraq. And to analysed thier motivations, relation to the recipients, and to detect commercial transplant
Since the discovery of photic driving by Adrian and Matthews in 1934, much has been discovered about the benefits of brainwave entrainment (BWE) or audiovisual entrainment (AVE) as it is commonly known today. Studies are now available on the effectiveness of AVE in promoting relaxation, hypnotic induction and restoring somatic homeostasis, plus improving cognition, and for treating ADD, PMS, SAD, migraine headache, chronic pain, anxiety, depression and hypertension.
The study aims to evaluate the effectiveness of brainwave entrainment on pre-operative fear and anxiety in pediatric dental patients.
The study protocol received approval from the Institutional Ethical Committee under reference number 3010/IEC/2021. Pediatric patients (252) aged from 7 to 12 years, who reported to the dental department were randomized pre-operatively and presented either with brainwave entrainment (experimental), delivered using a “David delight plus device” or a standard behavior management protocol (control). Baseline and post-assessment of anxiety and fear levels were done using the Visual Facial Anxiety Scale and Frankl’s behavior rating scale with Wright’s modification. Vitals such as blood pressure and pulse rate were also measured.
The study sample (n = 252) comprised 118 females and 134 males. The non-significant differences for values of (VFAS1, FRS1, HR1, and BP1) indicated similar baseline characteristics. In the brainwave entrainment group, the p values of the Mann–Whitney U test and Wilcoxon Signed Ranks test (p < 0.01) between the two-timepoints indicated a statistical difference for the values of (VFAS1, FBRS1, HR1, BP1) and (VFAS2, FBRS2, HR2, BP2).
Brainwave entrainment effectively reduces pre-operative fear and anxiety in pediatric dental patients. Therefore, they can be a non-pharmacological and non-invasive behavior management aid.
Clinical Trial Registry of India database CTRI/2023/03/051066.
Visual evoked responses (VER) were recorded from the thalamus and the scalp during stereotaxic thalamotomy in our service. The study involved fourteen patients with various involuntary movement disorders and intractable pain. Routine monopolar EEGs were recorded, from the ventrolateral nuclens and the centremedian of the thalamus, with multipolar electrodes and from the vertex and the occipital region with needle electrodes simultaneously. VERs have been analysed by means of averaging techniques as well as spectral analysis of the EEGs.
Experimental studies were also performed with chronically implanted electrodes in the ventrolateral nucleus, the lateral geniculate body, the visual cortex and the anterior sigmoid gyrus of the cats. The results were as follows:
1) Visual evoked responses (VERs) from the occipital regions were well demonstrated in seven out of fourteen cases. The responses had typical seven components (I-VII) with rhythmic after-discharge, documented by Cigánek's report.
2) The evoked responses from the vertex showed practically no early components. Therefore, four components of the response, namely P1, N1, P2 and N2, were started with P1 of the peak latency of 105.2msec. This response was corresponded to so-called vertex potential, of which pattern had no similarity to the VER from the occipital region.
3) The evoked responses from the human thalamic VL and CM nuclei showed very similar patterns to the vertex potentials with four components. Peak latencies of them were noted P1 with 96.4±12.8msec, N1 with 134.6±19.4msec, P2 with 196.0±25.5msec and N2 with 260.9±29.3msec. The thalamic responses always tended to lead off the vertical one about 8.8 to 18.3msec in all cases.
4) In the animal (cat) experiments, VER from visual cortex showed similar pattern to the one from the lateral geniculate body, and VER from the thalamic VL nucleus resembled to the one from the anterior sigmoid gyrus.
5) Rhythmic after-discharges were noted in the thalamus as well as the vertex after their wave components. The after-discharges of the vertex were not disappeared after VL thalamotomy, while spontaneous spindle discharges were disappeared after the thalamotomy. Therefore, rhythmic after-discharges were thought to be involved some other physiological mechanisms to that of spantaneous spindle activity.
6) Spectral analysis of EEGs showed high value of coherence between the thalamic and thevertical EEGs before and during photic stimulation. On the other hand, low coherence were obtained between the vertical and the occipital EEGs in all cases.
7) Photic stimulation provoked VERs in the occipital cortex as well as the vertex potentials through the VL or CM nucleus of the thalamus. It is most interesting that, while the VL nucleus is known as one of specific thalamic nuclei physiologically, the nucleus is also concerned with one of non-specific response such as vertex potentials.
Die retino-corticale Zeit zwischen dem Beginn der b-Welle des Elektroretinogramms (ERG) und dem Beginn des b-Potentials der corticalen Antwort auf einen Lichtreiz wurde beim Tier und beim Menschen durch gleichzeitige Elektroretinographie und Elektroencephalographie gemessen.
Beim Kaninchen fand sich im Mittel eine corticale Zeit von 28 msec bei Ableitung von der Dura in der Nähe des occipitalen Sehzentrums und eine retinale Zeit von 21 msec, so daß die retino-corticale Zeit etwa 7 msec betrug. Qualitativ ähnliche Antworten auf denselben Lichtblitz trafen im Corpus geniculatum laterale etwa 1 msec früher als im occipitalen Cortex ein.
Beim Menschen fand sich im Mittel mit einer bipolaren Ableitung oberhalb des Inions eine retino-corticale Zeit von 10 msec bei einer corticalen Zeit von 40 msec und einer retinalen Zeit von 30 msec. Auf die erste corticale Antwort (b-Potential) folgten die c-, d- und e-Potentiale, die schon den Charakter des wiedereinsetzenden Grundrhythmus zeigen. Diese Befunde bestätigen die früheren Beobachtungen von Monnier (1949/1952).
Mittels des Elektro-oculogramms (EOG) erwies sich, daß die Blinzelreaktion mit ihren Bulbusbewegungen nach oben erst nach 100 msec einsetzt, also erst nach dem Auftreten der corticalen Antwort.
Die Messung der retino-corticalen Zeit ist ein brauchbares Kriterium für die Beurteilung der Leistungsfähigkeit der zentralen Sehbahn.
Various studies on ADHD patients come to the conclusion that in the spontaneous EEG the low frequency theta-band (4-7Hz) is increased, whereas the beta-(14-18 Hz), alpha-band and the sensorimotor rhythm (SMR) is decreased compared to healthy volunteers. [1;2;3]. Therefore the theta/beta-ratio is considered to be a good indicator for the diagnosis of ADHD also shown in standardized behavioral studies. [4].
It was therefore not too far fetched to utilize neurofeedback - training for ADHD treatments using the theta/beta-band ratio as a parameter at first.
But the application of neurofeedback methods for the ADHD therapy showed ambivalent results: whereas some studies concluded the evidence for the effectiveness of the method for children not responding to medical therapy, [5; 6; 7], other studies state no improvements of hardware – in – the – loop – technique compared to pharmaceutical treatment [8; 9]
Of a more serious concern regarding the neurofeedback method could possibly be that the method requires a degree of concentration and learning ability, which is actually lacking in this group.
Technical Foundations of Neurofeedback provides, for the first time, an authoritative and complete account of the scientific and technical basis of EEG biofeedback. Beginning with the physiological origins of EEG rhythms, Collura describes the basis of measuring brain activity from the scalp and how brain rhythms reflect key brain regulatory processes. He then develops the theory as well as the practice of measuring, processing, and feeding back brain activity information for biofeedback training. Combining both a “top down” and a “bottom up” approach, Collura describes the core scientific principles, as well as current clinical experience and practical aspects of neurofeedback assessment and treatment therapy. Whether the reader has a technical need to understand neurofeedback, is a current or future neurofeedback practitioner, or only wants to understand the scientific basis of this important new field, this concise and authoritative book will be a key source of information.
Evoked potentials are the bioelectric responses of nervous tissue (field potentials) following electrical or adequate stimulation of sensory organs, afferent nerves or other cerebral structures neuronally connected with the recorded area. Evoked potentials can only be recorded if sufficient nervous tissue is excited simultaneously. Therefore, the stimuli are either electrical stimuli of a large number of elements or adequate stimuli (light, sound, pressure etc.) with a sharp gradient and of short duration. For visual evoked potentials a short flash (about 1–10 μ sec) of intense light is used, such as that produced by a stroboscope, or flashes of longer duration but with a short rise time. Sinusoidal stimuli have the disadvantage of variable rise times proportional to the stimulus frequency. The evoked potentials produced by light as well as by electrical stimuli in any part of the visual system have only a restricted value for analysis of the finer functional organization of the visual system if it is not correlated with results of single neuronal and behavioral analysis. But the evoked potential analysis has two advantages: 1) As an electrophysiological tool for determining anatomical connections in the brain and 2) as a method for monitoring cerebral responses in behavioral, physiological or pathophysiological situations, if more refined recording methods are not applicable. The informative value of an evoked potential will increase when more is known about the excitatory and inhibitory responses of the single neurons which contribute to it.
This chapter traces the origins of our current ideas about visual cortex. We begin, in Section 2, long before the beginning of science, in the 30th century BCE, with the earliest description of the cerebral cortex. In Section 3 we consider the views of Greek philosopher-scientists on the functions of the brain. Section 4 concerns the long period in which there were virtually no advances in Europe in understanding the brain. In Section 5 we describe how even after Western brain research was well underway again, the cerebral cortex tended to be ignored. Section 6 considers the beginning of the modern study of the cerebral cortex and the localization therein of psychological functions. Our focus narrows in Section 7 and we consider how a specifically visual area of the cortex was delineated. The final section brings us to the theme of the entire volume, the extrastriate visual cortices. This review ends in the early 1980s about the time of the award of the Nobel Prize to Hubel and Wiesel for their discoveries on the visual cortex.
If the language of the brain lies in its neuronal coding, then the expression of the brain lies in its rhythmicity and timing. The rhythmicity is due to the selective synchronization and desynchronization of the encoding within billions of pools of neurons which provide the sensory activity of everything that is sensed, thought, or done. Berger (1929) observed all four main rhythms-the alpha, beta, theta, and delta-in his very first EEG recording. It should come as no surprise, therefore, that since the earliest EEG studies, interest has turned toward rhythmic sensory stimulation, and its possible effects on brain function. A large and growing body of research and clinical experience demonstrates that audio-visual entrainment (AVE) quickly and effectively modifies conditions of high autonomic (sympathetic and parasympathetic) activation and over- and under-aroused states of mind, bringing about a return to homeostasis. AVE exerts a powerful influence on brain/mind stabilization and normalization by means of increased cerebral flow, increased levels of certain neurotransmitters, and by normalizing EEG activity. AVE is proving to be a safe and cost-effective treatment, especially for the large numbers of disorders associated with dysfunctions of the central and autonomic nervous system.
Die retino-corticale Zeit zwischen dem Beginn der b-Welle des Elektroretinogramms (ERG) und dem Beginn des b-Potentials der corticalen Antwort auf einen Lichtreiz wurde beim Tier und beim Menschen durch gleichzeitige Elektroretinographie und Elektroencephalographie gemessen.
BeimKaninchen fand sich im Mittel eine corticale Zeit von 28 msec bei Ableitung von der Dura in der Nähe des occipitalen Sehzentrums und eine retinale Zeit von 21 msec, so daß die retino-corticale Zeit etwa 7 msec betrug. Qualitativ ähnliche Antworten auf denselben Lichtblitz trafen im Corpus geniculatum laterale etwa 1 msec früher als im occipitalen Cortex ein.
BeimMenschen fand sich im Mittel mit einer bipolaren Ableitung oberhalb des Inions eine retino-corticale Zeit von 10 msec bei einer corticalen Zeit von 40 msec und einer retinalen Zeit von 30 msec. Auf die erste corticale Antwort (b-Potential) folgten die c-, d- und e-Potentiale, die schon den Charakter des wiedereinsetzenden Grundrhythmus zeigen. Diese Befunde bestätigen die früheren Beobachtungen vonMonnier (1949/1952).
Mittels des Elektro-oculogramms (EOG) erwies sich, daß die Blinzelreaktion mit ihren Bulbusbewegungen nach oben erst nach 100 msec einsetzt, also erst nach dem Auftreten der corticalen Antwort.
Die Messung der retino-corticalen Zeit ist ein brauchbares Kriterium für die Beurteilung der Leistungsfähigkeit der zentralen Sehbahn.
Diese Arbeit gliedert sich in zwei Teile.
1.
Die Messung der Corticalzeit an Gesunden. Folgende Zeiten wurden fiir die einzelnen Wellen ermittelt:
a-
Anfang 33 ms
b-
Culmination 67 ms
c-
Culmination 100–133 ms
d-
Culmination 150–200 ms
Gemessen wurde jeweils vom Beginn des Lichtreizes.
2.
Die Messung der Corticalzeit am Patienten mit Stauungspapillen. Von 16 Patienten wiesen neun eine Verl\:angerung der Corticalzeit auf.
Es erfolgte eine kurze Besprechung der Krankengeschichten und Besprechung der Ergebnisse.
Es wird festgestellt, daβ die verlängerte Corticalzeit bei Stauungspapillen ein zusatzliches, wertvolles objektiv zu erhebendes Zeichen ist.
The author describes a procedure by which he explores the electrical activity of the optic pathways of man at three different levels: the cornea (electroretinogram), the optic radiations or their vicinity (electrosubcorticogram), and the scalp (electroencephalogram).The results obtained are described for spontaneous activity and that evoked by isolated and repetitive photic stimulation (flicker). Certain new facts are brought to light in these experiments on the visual system in man with regard to the form of the electrical response to a single flash of light as recorded from cortex and subcortex, the form of the subcortical flicker response and its variation, and precise measurement of the latent times of these various phenomena and the central, retinocortical conduction time in man, hitherto measured only in animals.Certain of the results are interpreted as in support of the following conclusions: (1) the electrical activity recorded developes principally in a system of closed cortico-thalamic circuits, oriented radially in the occipital lobe. (2) The electrical activity may be different from moment to moment from different points in the subcortical regions and that the transcranial EEG provides a veritable instrumental synthesis of the “ensemble”.
Mit Makroelektroden lieen sich bisher nach Lichtreizung nur Wellenformen im elektrischen Projektionsfeld der Sehrinde beobachten, ohne da man sich ihr gehuftes Vorkommen im einzelnen erklren konnte. Mit Mikroelektroden wurde beobachtet, da ein Einzelneuron bei Aufnahme des Reizlichtimpulses negativ gerichtete Spitzen entldt. Durch Anwendung einer groen Lichtmenge fand sich jetzt, da sich die eigentliche Antwort der Sehrindenprojektion an die Hirnoberflche auf den etwa 40 msec whrenden Initialkomplex einer positiven und negativen Auslenkung zu beschrnken scheint. Dabei werden innerhalb letzterer wohl Neuronengruppen zur Entladung gebracht, was sich in Spitzen darstellt. Diese Darstellung konnte erzielt werden unter Ausschlu der Mglichkeit von Verletzungsentladungen durch eingefhrte Elektroden. Die Spitzen-Entladungen auf den Lichtreiz hin vermehren sich nach wiederholter Reizung auf Grund der dann mglicherweise einsetzenden Reizbahnung. Anschlieend kommt es anscheinend zu Regulationsvorgngen in Form der nachfolgenden Wellen abnehmender Frequenz. Nach etwa 500 msec findet sich wieder das normale Erregungsniveau des Grundrhythmus. Verschiedene bisherige Untersuchungsergebnisse der optischen Hirnrinde haben damit eine verbindende Klrung erfahren.
Bei Reizung des Kaninchenauges mit energiegleichen Lichtern verschiedener Spektralbereiche zeigte sich, daß nur mit Rotlicht λmax 641 mμ kein Elektroretinogramm und keine spezifischen Aktionspotentiale des Corpus geniculatum laterale und der Sehrinde abzuleiten sind.
Gleiche Latenzzeiten der Augen- und Gehirnaktionspotentiale ergeben sich bei Anwendung von Lichtreizen gleicher Energie, 1,7·10−2 W, im kurzwelligeren Spektralbereich (λmax 479 mμ blau, 538 mμ grün, 585 mμ gelb).
Die Feststellung, daß kurze Einzellichtreize eines Spektralbereiches über 600 mμ gleicher Energie am Auge und Gehirn keine Aktionspotentiale erstehen lassen, legt nahe, daß Rotlicht beim Kaninchen keinen Seheindruck hinterläßt.
1.1. Records obtained during photic stimulation may be described in terms of the following components, any or all of which may be present at any one time, or from time to time. 1.1.A. A series of dicrete elementary evoked responses, e.g. figures 1B and 8.1.2.B. Fusion of evoked responses giving an accidental appearance of rhythimicity (first part of figure 5).1.3.C. Instrumental summation of evoked response and spontaneous rhythms (Fig. 1A).1.4.D. True augmentation of “driving” of local rhythms at the frequency of the stimulus.1.5.E. Augmentation of harmonically related rhythms in other areas.2.2. Differences between individuals are attributable in some cases to anatomical variations and correlate also to some extent with the character of their spontaneous activity, with age and with differences in personality.3.3. Alterations in the response in given individuals are produced by somatic, mental and emotional changes whether spontaneous, voluntary or induced.4.4. Somatic, mental and emotional changes can be induced in the subject by stimulation at appropriate frequencies.5.5. The above effects can interact with one another in both regenerative and degenerative fashion.6.6. Subjective visual effects are attributed to interference between rhythmic evoked responses, and spontaneous rhythms at cortical and possibly thalamic levels.7.7. Anomalous (non-visual) effects in normal and abnormal between rhythmic evoked responses to interaction between the evoked activity and harmonically related spontaneous rhythms in other circuits at a thalamic level.8.8. Evocation of activity in non-visual circuits can be used to study their physiology and as an to diagnosis of some pathological conditions.9.9. Some theoritical implications of these findings are speculatively discussed.
A visual signal with two equiprobable alternative values, calling for a manual choice response, was presented to the subject after a fairly long (5 sec) waiting period from the ‘start’ signal.The effect of introducing a warning signal at a fixed interval between 0 and 500 msec prior to the visual signal to respond was examined. When the warning signal was presented in the auditory modality, it was found that simultaneous presentation of the auditory signal improved reaction times to the visual signal and that a further improvement developed as the interval was increased to 200 msec.When the warning signal was presented visually no improvement in reaction times to the visual signal to respond was found until the interval reached 150 msec.The results from the auditory warning condition may be accounted for by the difference in conduction latencies of simultaneously presented auditory and visual signals.The results from the visual warning condition suggest that no use can be made of a warning signal entering by the same modality as the signal to respond until an interval of 100–150 msec has elapsed.
1. Frequency-specific outputs from the visual cortex and lateral geniculate of unanesthetized rats were recorded and measured by means of matched narrow bandpass filters under conditions of no stimulation and bandpass-tuned flicker stimulation at the contralateral and ipsilateral eye.
2. In the visual cortex, output was significantly higher under stimulation than during the resting condition, and output under contralateral stimulation was significantly higher than under ipsilateral stimulation.
3. Signal-to-noise levels in the visual cortex were computed for both contralateral and ipsilateral stimulation. It was found that a S/N advantage of 4.38:1 favored contralateral stimulation over ipsilateral stimulation, whereas contralateral stimulation was approximately 13 times as effective as ipsilateralv with respect to the signal-to-noise power ratio.
4. Stimulation resulted in a significant increase in the duration of modulation periods at the visual cortex. The observed shift in modulation periods from rest to stimulation was significantly greater for contralateral stimulation compared to ipsilateral stimulation.
5. In the lateral geniculate, output was significantly higher under stimulation than during the resting condition, and as with the visual cortex, output under contralateral stimulation was significantly higher than under ipsilateral stimulation.
6. Signal-to-noise levels in the lateral geniculate showed as S/N advantage of 4.15:1 for contralateral over ipsilateral stimulation, whereas contralateral stimulation was approximately 10 times as effective as ipsilateral with respect to the signal-to-noise power ratio.
7. At the lateral genicualte, contralateral stimulation resulted in a significant increase in modulation period, whereas ipsilateral stimulation yielded practically no increase.
8. As the photo-evoked signal passed from lateral geniculate to visual cortex, S/N improved by a factor of approximately four, and the signal-to-noise power ratio by a factor of approximately ten.
9. The endogenous modulation period was significantly longer in the visual cortex than in the lateral geniculate. This was true under either contralateral or ipsilateral stimulation.
10. The known ratio of decussating optic nerve fibers in the rat was quantitatively reflected in corresponding relative signal-to-noise power ratios for contralateral and ipsilateral stimulation. This was true at both the occipital cortex and the lateral geniculate.
11. Modulation-period distributions in the visual cortex and lateral geniculate corresponded very well with theoretically predicted distributions derived from a proposed mathematical model.
The innate and state-of-the-art limitations on human operator manual control speed, frequency, and flexibility are reviewed and analyzed. Advanced manual control techniques for overcoming these limitations are suggested and research relating to these suggestions is reviewed. It is concluded that a considerable increase in human operator response speed, frequency, and flexibility could accrue from use of the suggested manual control techniques.
Saccadic eye movements, quick phases of nystagmus, and blinks induced prominent potential changes in the rostral calcarine cortex of the monkey. Slow eye movement did not induce these potential changes. Calcarine potential changes disappeared in darkness and could be induced by passive eye movement. The latency and amplitude of the calcarine responses was related to the amount of light energy which reached the retina. The amplitude was also dependent on the size of the rapid eye movements which induced the potential changes. Contrast in the external visual fields had no apparent effect on the amplitude of these potentials. This is different from lambda waves which disappear or are markedly attenuated when contrasts are removed from the external visual fields. Calcarine potential changes were present at levels of illumination which were in the scotopic range, and increased in size between 10 and 25 min after animals began to dark-adapt to low light levels. They were not affected by foveal destruction. It is likely that they arose largely as a result of activity in rods in the periphery of the retina.
An examination of potentials recorded from the hypothalamus of the chloralose-anesthetized cat following cutaneous or visual stimuli revealed the existence of complex interactions between evoked potentials and background electrical activity. These interactions led to alterations in the form of evoked potentials or to their nonappearance. The evoked potentials could be stabilized to a large extent by timing stimuli in relation to background activity so that stimuli were delivered in periods of little or no activity. Further, it was found that the effects of one evoked potential on subsequent evoked potentials lasted for periods of up to 6 sec. When averages of evoked potentials were computed it was found that the form of the average was markedly affected by background activity, which exaggerated stable wave-form components and distorted others. Averages computed from stimuli delivered in periods of little or no background activity showed clear differences from averages computed from stimuli delivered at the same time intervals, but without regard to background electrical activity.
A differential equation describing the electroencephalogram (EEG) is deduced based on the data on the structure of the brain cortex and the conceptions about a recurrent inhibition. This equation allows the study of a number of essential electrophysiological phenomena: the philogenetic differences in the frequency composition of the EEG, the shift of the EEG spectrum to higher frequencies upon excitation of the cortex, the lowering of the EEG rhythms and changes in cell reaction on deafferentation of the cortex, the identity in the spectra of a spontaneous EEG and evoked responses. A possible mechanism for the onset of epileptic activity is proposed.
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