Showing papers by "Keele University published in 1975"

Cochlear Nerve and Cochlear Nucleus

Abstract: The first recordings of single neurone activity in the auditory system were made from the cochlear nucleus of the cat, by Galambos and Davis (1943). In these experiments the authors were attempting to record from fibres in the cochlear nerve; subsequently, however, they concluded that the recordings had been from aberrant cells of the cochlear nucleus lying central to the glial margin of the VIII nerve (Galambos and Davis, 1948). The first successful recordings from fibres of the cochlear nerve were made by Tasaki (1954) in the guinea pig. These classical but necessarily limited results were greatly extended by Rose, Galambos, and Hughes (1959) in the cat cochlear nucleus and by Katsuki and co-workers (Katsuki et al., 1958, 1961, 1962) in the cat and monkey cochlear nerve. Perhaps the most significant developments have been the introduction of techniques for precise control of the acoustic stimulus and the quantitative analysis of neuronal response patterns, notably by the laboratories of Kiang (e.g. Gerstein and Kiang, 1960; Kiang et al., 1962b, 1965a, 1967) and Rose (e.g. Rose et al., 1967; Hind et al., 1967). These developments have made possible a large number of quantitative investigations of the behaviour of representative numbers of neurons at these levels of the peripheral auditory system under a wide variety of stimulus conditions.

The sharpening of cochlear frequency selectivity in the normal and abnormal cochlea.

Abstract: In the normal (anaesthetized) animal cochlea, the frequency threshold curves for single primary fibres are up to an order of magnitude sharper than the analogous functions derived from various reported measurements of the basilar membrane amplitude of vibration. This enhanced neural frequency selectivity is found in the same species and under conditions similar to those in which the mechanical measurements are taken. The sharpening process (at least near threshold) appears to be linear and is not dependent upon lateral inhibitory mechanisms. The variability of the neural frequency selectivity and its vulnerability to metabolic, chemical and pathological influences suggests the hypothesis that the sharpening is due to some form of ‘second filter’ subsequent to the relatively broadly tuned basilar membrane.All fibres recorded from in the cochlear nerve in the normal cochlea show this enhanced frequency selectivity; in contrast, in pathological cochleas, all fibres, or a substantial proportion, have high-thr...

The Structure of the Crust and Upper Mantle in the Region of Barbados and the Lesser Antilles

Abstract: Summary The results of marine geophysical surveys across the Lesser Antilles in 1971 and 1972 by Durham University and the Royal Navy as part of the CICAR Project have revealed that the arc front sediment complex is nearly 20 km thick beneath the Barbados Ridge, where the igneous crust of the Atlantic is subducted beneath the Caribbean Plate. It appears that the sediment complex has grown away from the island arc, engulfing any bathymetric trench that was originally present. The Barbados Ridge is underlain by metamorphosed sediments and has been uplifted 4 or 5 km since the Pliocene. The crust beneath the Lesser Antilles island arc is about 35 km thick, and the crustal segments either side of the arc differ from each other in their crustal structure. The whole arc complex shows a change in character along the arc at Lat. 14deg;N. A positive gravity anomaly of 40 mgal computed to be the theoretical anomaly caused by the subducted lithosphere beneath the Lesser Antilles, is compatible with the interpretation of the crustal structure. The Lesser Antilles are an example of a maturely developed island arc complex.

Differential responses of cat visual cortical cells to textured stimuli

Abstract: The responsiveness of primary visual cortical units to luminance edges or bars (Hubel and Wiesel, 1962) has encouraged the belief that they may serve as the elementary edgeor bar-'detectors' in a hierarchic pattern-recognition process. One possible objection to this view is that patterns can readily be reeognised when presented against a background of the same average luminance but different texture. Even an area of static visual 'noise' identieM in texture to its background, which is completely camouflaged when at rest, has its contours instantly recognizable if moved relative to the background. I t might be felt that this objection would be answered if the same units proved sensitive to such 'kinetic contours' as well as to contours of luminance.

Recent advances in electrical recording from the human brain

Abstract: New techniques for recording evoked potentials to sensory stimulation have led to applications with both theoretical and practical implications. Evoked potentials can be used as a diagnostic tool in some pathological conditions, as well as shedding light on the mechanisms by which sensory information is processed in the brain.

Cochlear Tuning Properties: Concurrent Basilar Membrane and Single Nerve Fiber Measurements

Abstract: Removal of perilymph from the cochlea has been reported to destroy the sharp tuning of cochlear neurons. That these changes are mechanical in origin is refuted by the concurrent recording of sharp neural tuning with broad basilar membrane responses from the same region of the partially drained cat cochlea. A second cochlear filter is therefore necessary.

Fairness and discrimination: English versus Welsh

Abstract: It has previously been suggested that there is a generic norm of conflict between groups so that when a differentiation is perceived between one group and another there is a predisposition to discriminate against the outgroup. The present study investigates whether this norm of conflict operates in social situations involving differentiation over real issues, or to what extent behavior is modified by norms of fairness. The research examined English and Welsh groups and found that when there was an opportunity of giving equal rewards to both parties about one-third of subjects acted in this fair way. Never as many as one-third of subjects acted in the most discriminatory way possible, and the remainder modified or tempered their discrimination. Behavior in this situation was felt to be the result of opposing internal norms for fairness and discrimination. Differences were found between the English and Welsh subjects. The Welsh showed more discrimination against the outgroup, while discrimination in favor of the outgroup was more common among the English. It is hypothesized that that effect may be characteristic of the behavior of ‘top-dogs’ and ‘underdogs’.

Intrinsic and Extrinsic Factors in Vowel Judgements

Abstract: Listeners have little difficulty in recognizing vowels produced by different talkers even though the formant frequencies of some of their vowels differ greatly. This implies that some kind of perceptual normalisation takes place. In the experiments described the effects of an intrinsic normalising factor, fundamental frequency, and an extrinsic factor, formant frequencies of vowels /u, i, a/ in an introductory sequence are compared. The results suggest that the extrinsic factor has a greater effect than the intrinsic factor. Fundamental frequency affects the perceived value of first formant frequency more than that of the second formant frequency. The introductory sequence, on the other hand, affects both formants to a greater extent, with perhaps a slightly larger effect on perceived second formant frequency.

Receptive field mechanisms of sustained and transient retinal ganglion cells in the cat.

Abstract: Receptive field organization of 135 sustained and 45 transient retinal ganglion cells was investigated in lightly pentobarbitone-anaesthetised cats. Stimuli were concentric annuli presented alone or simultaneously with a small spot centred on the receptive field, against photopic, mesopic or scotopic backgrounds. The addition of the test spot led to reduction in diameter of the centre-surround boundary of receptive fields of sustained retinal ganglion cells (assessed with annuli), and a decrease in diameter of the annulus which was most effective on the surround. In transient cells there was only marginal reduction in diameter of the centre-surround boundary, measured with annuli, and little or no decrease in diameter of the most effective annulus. Reducing background intensity from photopic to scotopic induced changes in response patterns and receptive field organization of sustained and transient retinal ganglion cells which were independent of stimulus intensity. Against photopic backgrounds, large annuli evoked surround-type responses from the majority of transient ganglion cells and from all sustained cells. In the scotopic range, surround-type responses could still be evoked from sustained cells, whereas predominantly centre-type responses were obtained throughout the receptive fields of transient cells. With transition from cone to rod vision, receptive field surrounds of sustained and transient cells became progressively less responsive than centres; in consequence the diameter of the centre-surround boundary increased. The initial, high frequency burst of impulses in discharges at annulus onset or offset became less evident and response latency increased substantially. The results are consistent with a model in which the centre and surround receptive field mechanisms are spatially co-extensive in transient retinal ganglion cells, albeit of different shape, but only partially overlapping in sustained retinal ganglion cells. It is suggested that the surround mechanism in sustained cells is spatially more extensive than the centre mechanism but does not extend entirely through the centre of the field.

Repair of UV-induced DNA damage and survival in yeast. I. Dimer excision.

Abstract: Summary The amount of pyrimidine dimer UV photoproduct lost from the DNA of irradiated yeast cells during dark incubation has been measured in various conditions. It was found that no dimers were lost when cells were incubated in saline. When the cells were incubated, with aeration, in a full growth medium, dimers were lost, most excision being complete within 4 h. Not all dimers were lost and the number lost was a function of UV dose. Maximum loss, amounting to 50 000 dimers per genome was observed after 4000 or 6000 erg/mm2 of UV. At higher doses, the number excised declined. Making the assumptions that dimers are the principal lethal product of UV, that a single dimer remaining in its genome is enough to prevent a cell from multiplying and that excision is the principal dark-repair process in yeast, these data were incorporated into the repair term of an expression relating survival to repair8 and it was found that the survival of yeast at doses up to 2000 erg /mm2 of UV could be quite accurately predicted. This is the first time it has been possible to account for survival in terms of measured repair. It is suggested that the divergence of the predicted and observed curves at higher doses is due to other repair processes known to exist in yeast.

The haslingden flags (namurian g1) of south-east lancashire: bar finger sands in the pennine basin

Abstract: Summary The sedimentary sequence between the Gastrioceras cancellatum Marine Band and the Rough Rock in south-east Lancashire comprises a wide range of lithologies ranging from mudstone through siltstone to ripple cross-laminated and cross-bedded medium-grained sandstones. The sequence consists broadly of two coarsening upwards sequences, each dominantly of mudstone and siltstone in its lower part and each capped by a sandstone member, the Lower and Upper Haslingden Flags respectively. Isopachytes on these sandstones show them to form elongate lobes thinning eastwards from a maximum exposed development around Blackburn. Palaeocurrent directions are dominantly towards the east. Both sandstones are cross-bedded in their central upstream regions and, in the Upper Haslingden Flags, a complex internal geometry involves large scale, low-angle cross-bedding up to 27 metres thick. The overall geometry and lithofacies assemblage is compared with that of a modern bar-finger sand and, in the Upper Haslingden Flags, the internal structure of the actual distributary mouth bar is shown. These deltas differ in type from the usual Millstone Grit delta in their finer grain size, their body geometry and in their palaeocurrent pattern. These points of difference raise the possibility of a western source area for at least some of the Millstone Grit and also imply that a different hydrological regime may have operated there.

Extraversion and variety-seeking in a monotonous task.

Abstract: It is hypothesized on the basis of Eysenck's theory of extraversion that extraverts should build more variety into their performance at a monotonous task than introverts. The performance of a group of extravets (n = 16) and a group of introverts (n = 16) on a simple repetitive task was compared. Comparisons were made on two measures of response variety: firstly, a simple measure of number of alternations among possible responses and, secondly, a measure of variety taken from information theory-the average entropy of the set of responses made. The hypothesis was confirmed on both measures. The results are interpreted as adding further support to Eysenck's work linking differences in extraversion to differences in arousal. Language: en

Dichoptic induction of McCollough-type effects.

Abstract: If left-oblique and right-oblique black/white gratings are presented alternately to one eye, and unpatterned red and green fields are presented alternately to the other, orientation-sensitive chromatic after-effects are induced. With the colour-stimulated eye the hue usually seen on a test grating is complementary to that originally paired with its orientation, with the pattern-stimulated eye the hue is the same as that originally paired. The experiments reported here show that: (a) the time course of decay of these chromatic after-effects (for each eye) fits approximately the same power law as that found for the normal McCollough effect; (b) analogous chromatic after-effects, opposite in the two eyes, can be dichoptically induced using pairs of stimuli other than gratings, such as dot patterns differing in magnification. These results suggest that strongly coloured light in one eye can induce a weakly complementary bias in the colour-signalling system of the other eye, at a level peripheral to the site o...

The size and shape of small‐scale current ripples: an experimental study using medium sand

Abstract: Flume experiments with medium sand confirm the increasing complexity in the shape of small-scale current ripples with increasing flow velocity for constant depth. Experiments suggest that a measure of ripple shape (the ratio of wavelengths of transverse to streamwise features, λ-x/λ-z) has a more complex relationship with the flow property (Fr, H/d) (where Fr is Froude Number of the flow and H/d is relative roughness), than was previously realized. It is suggested that hydraulic properties of the flow at the sediment water interface have a more general relationship with ripple form than do properties of the whole flow such as Froude and Reynolds Numbers. Properties of the whole flow tend to separate data into depthrelated curves at shallow flows where the free water surface influences the structure of the turbulence.

Electron‐impact fragmentation of penta‐fluorophenyldimethylsilyl ethers of some sterols of biological importance

Abstract: The mass spectral properties under medium and high resolution of a new protecting group for sterols is described and its ability to direct fragmentation is compared with established derivatives. The mass spectra obtained are characterised by strong molecular ions which fragment to produce a more even ion distribution than the familiar TMS ethers. This results in enhanced abundance of hydrocarbon fragments, with molecular structural details given greater prominence than is found with other derivatives.

Degrees of novelty and their effects on children's attention and preference

Abstract: Two experiments investigated the question of whether those attributes of stimuli effective in eliciting attention are also effective in motivating choice. In the first experiment children of 4 and 6 years were given the opportunity to view pictures varying in novelty. They could choose the type of picture they wished to view and view as long as they wished. They also stated their preference. Novelty influenced attention and expressed preference but not choice. In the second experiment fewer stimuli were used in the familiarization phase, thereby increasing tedium, whereupon choice was also found to be influenced. The results are considered in the context of other studies which have related exposure to attention and preference.