Showing papers by "Keele University published in 1973"
TL;DR: The dorsal nucleus is a more complex and more highly differentiated division of the cochlear nucleus than the ventral, both functionally and anatomically.
Abstract: 1
The response of single neurones in the cat cochlear nucleus to single tones have been studied as a function of their location in the dorsal, anteroventral and posteroventral divisions, with and without a variety of anaesthetics, and with particular attention to systematic analysis of the effective frequency bands and the time-course of responses
2
The neurons were classified into five Response Types; (1) excitatory only; (2) excitatory, with inhibition at the termination of effective tones; (3) excitatory, with inhibition to one or more adjacent frequency “side-bands”; (4) mainly inhibitory over a wide band of frequencies with one or more, usually adjacent, excitatory frequency bands; (5) inhibitory only at threshold, with or without “off-excitation”, or high threshold excitatory “side-bands”
3
Substantial differences in the distribution of Response Types, and in particular of inhibitory phenomena, were found between dorsal and ventral divisions, and in the dorsal division between anaesthetized and unanaesthetized conditions No significant differences were found between anteroventral and posteroventral divisions, with or without anaesthesia Response Type 1 neurones were almost entirely restricted to the ventral divisions, where Type 2 was the commonest 92% of the dorsal division neurones in the unanaesthetized or chloralose anaesthetized preparations, and 50% in the barbiturate and halothane preparations could be inhibited by single tones, ie were of Types 3, 4 or 5 In the ventral divisions the corresponding proportions were approximately 10% under both conditions of anaesthesia
4
Pentobarbitone and halothane anaesthesia reduce the inhibition on neurones of the dorsal division
5
It is concluded that the dorsal nucleus is a more complex and more highly differentiated division of the cochlear nucleus than the ventral, both functionally and anatomically
308 citations
01 Jan 1973
138 citations
TL;DR: The results indicate that the shape of borders is coded at the same level as the coding of orientation in line figures of various sizes, indicating that a single coding mechanism can serve both functions, but those used to signify shape reach a greater size.
129 citations
Journal Article•
TL;DR: F Fourier-analyzed EP's provide the clinician with an immediate indication of the result of altering refractive correction, so that this EP procedure is analogous to conventional subjective refraction.
Abstract: With no prior information of either spherical or cylindrical components, objective (evoked potential) refraction can be performed up to 100 times faster than by comparable averaging procedures. The new procedure is to directly obtain the required graph of evoked potential (EP) amplitude vs. some stimulus parameter rather than to make separate measurements of each point on the graph. Fourier-analyzed EP's provide the clinician with an immediate indication of the result of altering refractive correction, so that this EP procedure is analogous to conventional subjective refraction. While the subject views the pattern through a rotating stenopeic slit, a 10-second plot of EP amplitude vs. slit angle can indicate the axes of astigmatism to within 10°. The slit is then set parallel first to one axis of astigmatism and is then turned through 90° while the subject views the pattern through a lens whose power is continuously oscillated. Each of these two graphs of EP amplitude vs. lens power can be obtained in 10 to 20 seconds; these data give a complete description of the required refractive correction to within 0.5 D. The use of checks rather than stripes gives a faster procedure.
123 citations
TL;DR: Psychophysical findings which bear on the question whether the dynamic characteristics of binocular depth perception differ for stimuli located in front of, behind and near the plane of fixation are reported.
115 citations
TL;DR: It is concluded that the dorsal nucleus receives its major sensory (inhibitory) input by way of an intranuclear pathway originating in the anteroventral nucleus.
Abstract: The hypothesis is tested that the dorsal division of the cochlear nucleus might not be a second order nucleus but might derive its major sensory (inhibitory) input via an intranuclear pathway from the ventral division.
1.
The mean latency of excitation of neurones in the dorsal division under pentobarbitone was significantly longer than in the antero- and postero-ventral divisions.
2.
Participation of the centrifugal (“efferent”) nervous system in the inhibitory responses of the dorsal cochlear nucleus could be excluded. Firstly, the latency of inhibition evoked by tones in the dorsal nucleus under chloralose anaesthesia and in unanaesthetized preparations was found to be as short as 4–6 msec. Secondly, the inhibitory responses of neurones to tonal stimuli could be recorded in spite of acute section of the two centrifugal fibre inputs to the dorsal nucleus.
3.
Inhibition of neurones in the dorsal nucleus was evoked by direct electrical stimulation of the anteroventral nucleus or the association fibres linking the anteroventral to the dorsal nucleus. These results were also obtained after degeneration of the sensory input to the cochlear nuclei by prior section of the cochlear nerve.
4.
It is concluded that the dorsal nucleus receives its major sensory (inhibitory) input by way of an intranuclear pathway originating in the anteroventral nucleus. The importance of the division of the auditory pathway into dorsal and ventral paths is discussed.
95 citations
Journal Article•
TL;DR: The mechanisms for stereopsis are shown to consist of at least two components in the same individual, based upon a new kind of perimetry whereby field maps for stereoopsis are plotted for both convergent and divergent disparities.
Abstract: The neural basis for stereopsis may be divided into at least two components: one mechanism that processes divergent disparities and a second mechanism that processes convergent disparities. The most clearcut evidence for the presence of these two components is the finding that some individuals lack either one or the other. However, when the ability to process both convergent and divergent disparities is present in the same individual it is more difficult to demonstrate the presence of two separate mechanisms. In this paper, the mechanisms for stereopsis are shown to consist of at least two components in the same individual. This demonstration is based upon a new kind of perimetry whereby field maps for stereopsis are plotted for both convergent and divergent disparities. Extensive measurements on one observer show that the zone of the visual field over which convergent disparities are processed may differ quite distinctively from the zone of the visual field over which divergent disparities are processed.
95 citations
TL;DR: The human brain generated electrical responses to changes in the chromatic contrast of an equiluminant spatially-patterned stimulus even when the eye's longitudinal and transverse chromatic aberrations were simultaneously cancelled, suggesting that the human visual system handles colour information differently when colour is linked with spatial form than when color is not linked with form.
91 citations
TL;DR: The feasibility of converting English text into speech using an inexpensive computer and a small amount of stored data has been investigated and the intelligibility of the resulting synthetic speech is assessed by listening tests.
Abstract: The feasibility of converting English text into speech using an inexpensive computer and a small amount of stored data has been investigated. The text is segmented into breath groups, the orthography is converted into a phonemic representation, lexical stress is assigned to appropriate syllables, then the resulting string of symbols is converted by synthesis-by-rule into the parameter values for controlling an analogue speech synthesizer. The algorithms for performing these conversions are described in detail and evaluated independently, and the intelligibility of the resulting synthetic speech is assessed by listening tests.
71 citations
TL;DR: It is shown that steady-state EP amplitude may be a very poor measure of brightness contrast, at least when the sensations are considerably above threshold, and interactions between blurring and pattern size could lead to large systematic errors in EP refraction procedures.
Abstract: The amplitude of the evoked potential (EP) generated by an oscillating checkerboard pattern remains constant, even though the brightness contrast of the checks may be significantly altered by changing fixation distance without altering retinal subtense. On the other hand, when the pattern is slightly blurred, the brightness contrast of small checks is changed only slightly, whereas the EP undergoes marked attenuation. Such a double dissociation between brightness effects and the EP shows that steady-state EP amplitude may be a very poor measure of brightness contrast, at least when the sensations are considerably above threshold. For suprathreshold stimuli, check size may also affect brightness contrast and the steady-state EP amplitude in different ways. Moderate blurring may increase the amplitudes of large-check EP’s, while attenuating small-check EP’s. Interactions between blurring and pattern size could thus lead to large systematic errors in EP refraction procedures.
61 citations
TL;DR: The limited retinal range of the interactive process responsible for Mach Bands and the related illusion2 are shown by the gradual disappearance of the illusion as the viewing distance is increased, which can be taken to explain why the middle panel in Fig. 1 is seen as brighter overall than its neighbours.
Abstract: A NUMBER of well-known visual phenomena, including Mach Bands1 and the related illusion2 shown in Fig. 1 are inter-pretable as evidence of lateral interaction between adjacent neural channels sensitive to retinal luminance. Inhibitory interaction would lead to disproportionate weight being given to sharp discontinuities in luminance. This can be taken to explain why the middle panel in Fig. 1 (when viewed from the right distance) is seen as brighter overall than its neighbours, though objectively all three have the same luminance at their centres. The limited retinal range of the interactive process responsible is shown by the gradual disappearance of the illusion as the viewing distance is increased.
TL;DR: In this article, the main Auger peaks in the low energy Auger spectra of clean Mg and Fe surfaces were identified as due to L 2,3 VV and M 2, 3 VV transitions for Mg, and the changes in the spectra are believed to be due to the energy shifts of inner energy levels and valence bands involved in the Auger transitions as an oxide is formed.
TL;DR: The unexpectedly large effect of ΔF upon depth sensitivity suggests that there is more than one class of disparity detector such that a given monocular input to a given disparity detector is elicited by only one direction of retinal image movement.
TL;DR: It is concluded that the motion-offset and -onset VEPs likewise may be largely the product of motion-sensitive mechanisms when the stimulus velocity is less than about 10dg/sec.
Abstract: Human averaged visual evoked potentials (VEPs) have been recorded to the onset, reversal and offset of motion of a visual noise pattern as in the previous paper; and to the appearance and disappearance of stationary and of moving noise patterns These VEPs have been compared
TL;DR: Azadirachtin, a triterpenoid of Azadirachta indica with feeding and growth disruptive effects on certain insects, has been found in Melia azedarach.
TL;DR: The Duolbasgaissa Formation, Lower Cambrian, of northern Norway consists of 550 m of mineralogically and texturally mature sandstones with subordinate siltstones, mudstones and conglomerates as mentioned in this paper.
Abstract: The Duolbasgaissa Formation, Lower Cambrian, of northern Norway consists of 550 m of mineralogically and texturally mature sandstones with subordinate siltstones, mudstones and conglomerates. Four facies are defined on the basis of grain size, bed thickness and sedimentary structures. Facies 1–3 consist of a variety of erosively-based, cross-stratified and parallel-stratified sandstones interbedded with siltstone and mudstone. Many of these sandstones show evidence of deposition from waning currents. Facies 4 consists of trough cross-bedded sandstones with sets up to 4 m thick. Symmetrical ripples and bioturbation are ubiquitous. Bipolar palaeocurrent distributions are common to all facies and one mode is usually strongly dominant.
Lateral facies variations and sedimentary structures suggest that deposition took place in a tide-dominated, offshore, shallow marine environment in which maximum sediment transport probably occurred when storm generated waves enhanced tidal currents.
The four facies are thought to represent the deposits of various parts of tidal sediment transport paths such as exist in modern seas around Great Britain. Small scale coarsening upward sequences may represent the superposition of facies independently of changing water depth. Lack of information prevents a detailed palaeogeographic reconstruction. It is suggested that sand body shape is not accurately predictable.
TL;DR: Viewing a target moving in depth depresses visual sensitivity to depth when test and adapting stimuli simulate motion along closed paths with the same directions of rotation, but for opposite directions ofrotation, sensitivity is either unaffected or increased.
Abstract: Viewing a target moving in depth depresses visual sensitivity to depth when test and adapting stimuli simulate motion along closed paths with the same directions of rotation. However, for opposite directions of rotation, sensitivity is either unaffected or increased. This points to two classes of disparity detectors. Either eye's input to a single class of disparity detector consists of the physiological responses to a single direction of horizontal movement.
TL;DR: McCollough observed that if only one eye was exposed to the original sequence of stimuli, no after-effect was seen when the other eye was used to view the test grating, and suggested as a possible explanation that orientation-sensitive channels in the uniocular nervous system may be colour-coded, so that strong adaptation with bars of red light in one orientation leads to a “minus-red” after-response from the adapted channels to similarly oriented colourless bars.
Abstract: MCCOLLOUGH1 discovered that if a grating pattern of (say) red vertical stripes is viewed alternately with one of green horizontal stripes for some minutes, an orientation-specific colour after-effect is observed when viewing a black-and-white test grating. White stripes in a given orientation appear tinted with the hue complementary to the hue presented at that orientation in the original stimulus. McCollough observed that if only one eye was exposed to the original sequence of stimuli, no after-effect was seen when the other eye was used to view the test grating. From this she concluded that the adaptation responsible for the after-effect must occur somewhere in the uniocular pathway before signals from left and right eyes are combined. She suggested as a possible explanation that orientation-sensitive channels in the uniocular nervous system (“edge-detectors”) may be colour-coded, so that strong adaptation with bars of red light in one orientation leads to a “minus-red” after-response from the adapted channels to similarly oriented colourless bars. Harris and Gibson2 have confirmed that the effect persists in conditions ruling out ordinary negative afterimages, which Murch and Hirsch3 have shown sufficient to induce it. Held and Shattuck4 have demonstrated a corresponding after-effect of colour upon the perceived orientation of test bars.
TL;DR: This work has shown that in animals (such as the cat), single nerve cells with properties which suggest that they signal when an object is moving in depth away from the plane of binocular fixation are also found in humans.
Abstract: RECENT psychophysical evidence suggests that there are movement detectors in the human visual pathway selectively sensitive to different directions of motion in three-dimensional space1–5. In animals (such as the cat) there are single nerve cells with properties which suggest that they signal when an object is moving in depth away from the plane of binocular fixation6.
01 Jan 1973
TL;DR: With the help of more powerful statistical techniques it becomes possible to ask increasingly sophisticated questions about the form of these potentials and their relation both to the parameters of stimulation and to the processes of perception.
Abstract: When a bright light is flashed into the eyes of a subject whose electroencephalogram (EEG) is being recorded, it is often possible to see, riding the normal EEG record after each flash, a transient polyphasic potential change of several microvolts in amplitude. Until the advent of electronic computing aids it was difficult to separate such “Visual Evoked Potentials” (VEP’s) from the ongoing EEG activity, and they remained little more than a curiosity. The past decade, however, has seen a proliferation of relatively inexpensive electronic devices for the extraction and purification of repetitive signals corrupted by an uncorrelated background. In their simplest forms such devices rely on the averaging of successive samples, in this case of the EEG, for a limited period after each presentation of the stimulus (Goldstein, 1960); but with the help of more powerful statistical techniques it becomes possible to ask increasingly sophisticated questions about the form of these potentials and their relation both to the parameters of stimulation and to the processes of perception.
01 Jan 1973
TL;DR: The E 1a -E 2a (inclusive) succession of the North Staffordshire Basin exhibits a crudely rhythmic sequence with units of calcareous siltstone lithofacies, units of siderite-bearing protoquartzitic sandstone and typical marine bands of thicker-shelled goniatite faunal phase.
Abstract: Summary The E 1a –E 2a (inclusive) succession of the North Staffordshire Basin exhibits a crudely rhythmic sequence with units of calcareous siltstone lithofacies, units of siderite-bearing protoquartzitic sandstone lithofacies and typical marine bands of thicker-shelled goniatite faunal phase. The eastern and western margins of the basin are marked by total or partial disappearance of the silt-stone and protoquartzite lithofacies; the southern margin is unpreserved. The protoquartzite lithofacies exhibits sandstone-rich and sandstone-poor sub-types, interpreted as proximal and distal turbidites respectively. The flows originated to the south of the basin, probably on the fronts of periodically advancing deltas. The calcareous siltstones were deposited in a more fully marine environment by intermittent waning currents, similar in some, but not all, respects to turbidity currents. Supply was probably from the west and north-west. The rhythmic sequence is explained as a response to sea-level oscillation during a period of unusually strong differential movement between the North Staffordshire Basin and its margins.
TL;DR: In this article, qualitative experiments are described which suggest that crazing can occur in some fully cured epoxy resin systems, which may indicate that the epoxy resins are not fully cured.
Abstract: Some qualitative experiments are described which suggest that crazing can occur in some fully-cured epoxy resin systems.
TL;DR: The human averaged visual evoked potentials recorded to the onset, reversal and offset of the motion of a visual noise pattern were almost invariant with respect to changes in the brightness, the direction of motion, and the sharpness of the boundary of the visual field.
Abstract: Human averaged visual evoked potentials (VEPs) have been recorded to the onset, reversal and offset of the motion of a visual noise pattern. The VEPs have been analysed into components, distinguishable by their different scalp distributions, and by their distinct dependences on the retinal area stimulated and the pattern velocity. The effects of varying the form and the scale of the pattern have been investigated. The VEPs were almost invariant with respect to changes in the brightness, the direction of motion, and the sharpness of the boundary of the visual field. Under some circumstances the motion-reversal VEP was very similar to the sum of the motion-onset and the motion-offset VEPs.
TL;DR: In this article, the authors discuss the effects of pre-tests on subsequent learning and further tests (of varying degrees of similarity and difference) given after instructional sessions, and discuss the issues involved in a series of experiments conducted by the author.
Abstract: At the present time, sharp differences of opinion exist concerning the possible and probable consequences of giving studients a test before the commencement of instruction. Researchers are unclear about the effects of such “pre-tests” on subsequent learning (if any), and they are also unclear about the effects of such tests on further tests (of varying degrees of similarity and difference) given after instructional sessions. There is evidence that pre-tests can have orienting and motivational and (hence) teaching functions — in addition to the sought-for testing function. There is also evidence that these additional functions can be either general or specific. The present paper contributes to the ongoing debate by discussing the issues involved in the context of a series of experiments conducted by the author.
TL;DR: GOLDSTEIN1 has shown that when two tones of frequency f1 and f2 (f2>f1) are heard simultaneously, the most prominent distortion product is the combination tone of frequency 2f1−f2, which seems to rule out Helmholtz's2 explanation based on simple limiting distortion in the middle ear.
Abstract: GOLDSTEIN1 has shown that when two tones of frequency f1 and f2 (f2>f1) are heard simultaneously, the most prominent distortion product is the combination tone of frequency 2f1−f2. It is observed most strongly when the ratiof2/f1=1.1, when it is typically only 15 dB below the level of the primary tones. The relative amplitude can be measured by cancellation and is substantially independent of input level, that is, it can be considered as an essential non-linearity, but it decreases rapidly as the ratio f2/f1 is increased. These features seem to rule out Helmholtz's2 explanation based on simple limiting distortion in the middle ear.
TL;DR: The Dinantian succession near Eyam, Derbyshire as discussed by the authors contrasts sharply with that proved in the Woo Dale borehole about 11 km west-south-west of Eyam.
Abstract: THE unexpectedly thick development of the Dinantian succession near Eyam, Derbyshire1 contrasts sharply with that proved in the Woo Dale borehole about 11 km west-south-west of Eyam2.
TL;DR: In this paper, the results of ESR studies of single crystals of the type M3Cr2Cl9 are reported for M=Cs and tetraethylammonium (Et4N).
Abstract: The results of ESR studies of single crystals of the type M3Cr2Cl9 are reported for M=Cs and tetraethylammonium (Et4N). In both materials the anions (Cr2Cl9)3- exist as discrete units within the crystal structure. In the caesium compound the Cr3+ pairs are found to be coupled by an antiferromagnetic interaction which can be described by the isotropic form Delta S1S2, with Delta /k=17+or-1K. The corresponding value for the Et4N material is 20+or-2K. The caesium compound shows a spectral averaging effect at high temperatures. This is interpreted in some detail in terms of relatively weak exchange coupling between pairs. The Et4N compound is sufficiently magnetically dilute to show a resolved spectrum at all temperatures. This spectrum is however attributed entirely to the total spin J=2 manifold; no spectrum was detected from the J=1 or 3 manifolds of the pairs.
TL;DR: The electric field arising from K+ or Na+ in the “A” sites of synthetic hydroxyamphiboles of the richterite-tremolite series raises the stretching frequency of adjacent OH groups by about 60 cm−1 as mentioned in this paper.
Abstract: The electric field arising from K+ or Na+ in the “A” sites of synthetic hydroxyamphiboles of the richterite-tremolite series raises the stretching frequency of adjacent OH groups by about 60 cm−1. In natural amphiboles, however, the increase in frequency is generally only 20–40 cm−1, due, probably, to the effects of such substitutions as F for OH and Al for Si.