An electrophysiological analysis of the reflex regulation of reticulo-ruminal movements

The reflex regulation of reticulo-ruminal movements was analysed in the present experiments using an electrophysiological 'single fibre* recording technique. The afferent input to and the efferent output from the 'gastric (retioulo-ruminal) centres' was repeatedly sampled by recording from single gastric units dissected from the cervical region of the left vagus in 8 sheep anaesthetized with chloralose and 70 with halothane. Primary cycle movements of the reticulo-rumen were usually evoked by distending a reticular balloon with 400-600 ml air.By recording from afferent gastric units, it was found that the majority of gastric mechanoreceptors are slowly-adapting 'in series' tension receptors situated in the muscle layers of, principally, the reticulum, the reticuloruminal fold and the cranial sac (dorsal rumen). The afferent discharge from these receptors increases during passive distension and during isometricallyrecorded contractions. Receptors in the lips and the floor of the reticular groove and oma sal canal respond both during a contraction and, particularly, to pressure. The 'resting discharge' generated by tension receptors is largely determined by the intrinsic motility of smooth muscle cells. The mean conduction velocity in afferent gastric fibres is 12.4 m/sec.By recording from efferent gastric units, at least 7 distinctive types were discernible and, by relating their discharges temporally to movements of the reticulum and of the rumen, it wa3 concluded that Types I, II and III occur in fibres innervating the reticulum or associated structures, Type IV the rumen and Types V, VI and VII other gastric structures not yet identified. In only Type VII units is there a 'resting discharge' during the quiescent part of the gastric cycle. By cold blocking vagal nerves, it was demonstrated that separate efferent fibres innervate the reticulum and the rumen and, that the dorsal vagal trunk carries predominantly excitatory afferent fibres to the gastric centres whereas the ventral vagal trunk carries predominantly either excitatory or inhibitory fibres depending on the experimental conditions.By recording from afferent and from efferent gastric units at the same time as altering conditions in the reticulum either physically or with certain drugs, the changes in the afferent input to and the efferent output from the gastric centres evoked by these manoeuvres were recorded and estimates of the total and the central reflex time for gastric reflexes were made.It is concluded from the present investigation that:(a) the co-ordination of the complex sequence of primary cycle movements is a function of the 'gastric centres', through their ability to determine the parameters and temporal interrelationships of efferent nervous discharges in the various types of gastric units innervating different regions of the forestomach.(b) the tonic afferent input from 'in series' reticular tension receptors during the quiescent period of the primary cycle provides a reflex •drive* to the gastric centres and largely determines the rate, the duration and the amplitude of reticular and ruminal contractions.(c) the enhanced afferent input to the 'gastric centres', occurring during a reticular contraction recorded under isometric conditions, modifies the form, the amplitude, the duration and the delay in onset of the later parts of the contraction sequence of the reticulum and the rumen

Shape information mediating basic- and subordinate-level object recognition revealed by analyses of eye movements.

This study examines the kinds of shape features that mediate basic- and subordinate-level object recognition. Observers were trained to categorize sets of novel objects at either a basic (between-families) or subordinate (within-family) level of classification. We analyzed the spatial distributions of fixations and compared them to model distributions of different curvature polarity (regions of convex or concave bounding contour), as well as internal part boundaries. The results showed a robust preference for fixation at part boundaries and for concave over convex regions of bounding contour, during both basic- and subordinate-level classification. In contrast, mean saccade amplitudes were shorter during basic- than subordinate-level classification. These findings challenge models of recognition that do not posit any special functional status to part boundaries or curvature polarity. We argue that both basic- and subordinate-level classification are mediated by object representations. These representations make explicit internal part boundaries, and distinguish concave and convex regions of bounding contour. The classification task constrains how shape information in these representations is used, consistent with the hypothesis that both parts-based, and image-based, operations support object recognition in human vision

Eye movement patterns during the recognition of three-dimensional objects: Preferential fixation of concave surface curvature minima

This study used eye movement patterns to examine how high-level shape information is used during 3D object recognition. Eye movements were recorded while observers either actively memorized or passively viewed sets of novel objects, and then during a subsequent recognition memory task. Fixation data were contrasted against different algorithmically generated models of shape analysis based on: (1) regions of internal concave or (2) convex surface curvature discontinuity or (3) external bounding contour. The results showed a preference for fixation at regions of internal local features during both active memorization and passive viewing but also for regions of concave surface curvature during the recognition task. These findings provide new evidence supporting the special functional status of local concave discontinuities in recognition and show how studies of eye movement patterns can elucidate shape information processing in human vision

Circuit quantum acoustodynamics with surface acoustic waves

The experimental investigation of quantum devices incorporating mechanical resonators has opened up new frontiers in the study of quantum mechanics at a macroscopic level$^{1,2}$. Superconducting microwave circuits have proven to be a powerful platform for the realisation of such quantum devices, both in cavity optomechanics$^{3,4}$, and circuit quantum electro-dynamics (QED)$^{5,6}$. While most experiments to date have involved localised nanomechanical resonators, it has recently been shown that propagating surface acoustic waves (SAWs) can be piezoelectrically coupled to superconducting qubits$^{7,8}$, and confined in high-quality Fabry-Perot cavities up to microwave frequencies in the quantum regime$^{9}$, indicating the possibility of realising coherent exchange of quantum information between the two systems. Here we present measurements of a device in which a superconducting qubit is embedded in, and interacts with, the acoustic field of a Fabry-Perot SAW cavity on quartz, realising a surface acoustic version of cavity quantum electrodynamics. This quantum acoustodynamics (QAD) architecture may be used to develop new quantum acoustic devices in which quantum information is stored in trapped on-chip surface acoustic wavepackets, and manipulated in ways that are impossible with purely electromagnetic signals, due to the $10^{5}$ times slower speed of travel of the mechanical waves.Comment: 12 pages, 9 figures, 1 tabl

Stereo viewing modulates three-dimensional shape processing during object recognition: a high-density ERP study

The role of stereo disparity in the recognition of 3-dimensional (3D) object shape remains an unresolved issue for theoretical models of the human visual system. We examined this issue using high-density (128 channel) recordings of event-related potentials (ERPs). A recognition memory task was used in which observers were trained to recognize a subset of complex, multipart, 3D novel objects under conditions of either (bi-) monocular or stereo viewing. In a subsequent test phase they discriminated previously trained targets from untrained distractor objects that shared either local parts, 3D spatial configuration, or neither dimension, across both previously seen and novel viewpoints. The behavioral data showed a stereo advantage for target recognition at untrained viewpoints. ERPs showed early differential amplitude modulations to shape similarity defined by local part structure and global 3D spatial configuration. This occurred initially during an N1 component around 145–190 ms poststimulus onset, and then subsequently during an N2/P3 component around 260–385 ms poststimulus onset. For mono viewing, amplitude modulation during the N1 was greatest between targets and distracters with different local parts for trained views only. For stereo viewing, amplitude modulation during the N2/P3 was greatest between targets and distracters with different global 3D spatial configurations and generalized across trained and untrained views. The results show that image classification is modulated by stereo information about the local part, and global 3D spatial configuration of object shape. The findings challenge current theoretical models that do not attribute functional significance to stereo input during the computation of 3D object shape