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B J Frost

Publications and source records attributed to B J Frost.

At least 55 records · Page 3Linked to original sources
PubMed1985

Acquisition of a 250-word vocabulary through a tactile vocoder.

In a previous experiment [P. L. Scilley, "Evaluation of a vibrotactile auditory prosthetic device for the profoundly deaf," unpublished Masters thesis, Queen's University, Kingston, Canada (1980)] two normal subjects learned to identify 70 and 150 words, respectively, using the Queen's Tactile Vocoder. In the present experiment, the most advanced subject continued word learning until a tactile vocabulary of 250 words was acquired. At this point randomized tests were given to obtain an indication of final performance level. From these data conditional probabilities of correct response for each stimulus word and significant confusions were obtained, which provides insight into the advantages and present limitations of the tactile vocoder.

Communication Devices for People with Disabilities↗
PubMed1985

A tactile fovea in the Scolopacidae?

In the Scolopacidae, which includes the sandpipers and snipe, there is a significant enlargement of the neural apparatus subserving the behaviour of probing which is the preferred feeding strategy of this family of birds. Along with a sophisticated motor arrangement which allows fine manipulation by the tip of the bill without abduction of the mandibles, there is an obvious expansion of the forebrain area devoted to the trigeminal innervation of receptor-rich bill tip. This 'trigeminal expansion' forms a visible bulge on the surface of the brains of the Scolopacidae but not on the brains of related shorebirds in the Charadriidae; this difference would be evident in fossil endocast material and could provide new information on the evolution of the avian brain.

Animals↗
PubMed1984

Video and scanning microdensitometer-based imaging systems in autoradiographic densitometry.

The characteristics of computer-assisted imaging devices (CIDs) incorporating charge-coupled device cameras, vidicon cameras and scanning microdensitometers (SMDs) are compared. Advantages of vidicons include their low cost, the option of real-time imaging, continuously variable optical magnification and the wide choice of available vidicon elements. Disadvantages include densitometric non-linearities and, with some vidicons, lack of dynamic range. A CID comprising a laboratory minicomputer, image processing device, vidicon and SMD scanners and our 'PANDA' image analysis routines is described. Software corrections for vidicon errors are evaluated by comparing the densitometric accuracy of the CID receiving input from the vidicon camera and from the SMD. The scanners exhibit similar densitometric accuracy and linearity, and acceptable between-session repeatability. It is concluded that densitometric precision of a corrected vidicon scanner is not the limiting factor for quantitative autoradiographic densitometry.

Animals↗
PubMed1984

Functional activity in the lateral habenular and dorsal raphe nuclei following administration of several dopamine receptor antagonists.

2-[14C]deoxyglucose autoradiography was used to show regional functional activity in the rat brain following administration of the dopamine antagonists, cis-flupenthixol, metoclopramide, and pimozide. Elevation of functional activity was observed in the lateral habenula (LHb) following administration of all antagonists. The dorsal raphe nucleus (DR) exhibited decreased functional activity following cis-flupenthixol, which exerts effects at both the D1 and D2 receptors, but not following pimozide or metoclopramide, which primarily act at the D2 receptor. These results converge with previous reports suggesting that the functional status of the LHb is regulated by dopaminergic systems, and that LHb efferents may exert a major influence upon DR neurons. These data further suggest that an influence of the LHb upon DR neurons may be affected via the D1 receptor.

Animals↗
PubMed1983

Single visual neurons code opposing motion independent of direction.

Cells in intermediate and deeper layers of the pigeon optic tectum respond best when a textured background pattern is moved in the opposite direction to a moving test spot. Complete inhibition occurs when the background moves in the same direction as the test stimulus. Most noteworthy is the invariance of this relationship over a wide range of test spot directions. These cells represent a higher level of abstraction in a motion-detecting system and may play a role in figure-ground segregation or the discrimination of the motion of an object from self-induced optical motion.

Animals↗
PubMed1983

Double-opponent-process mechanism underlying RF-structure of directionally specific cells of cat lateral suprasylvian visual area.

For the experiments reported in this study, recordings were obtained from 246 single units in the middle lateral suprasylvian visual area (LS) of 13 cats. 49 of these cells were subjected to detailed quantitative analysis. The receptive field (RF) organization was examined for directionally specific cells by presenting moving single spots on large moving random dot backgrounds. A cell's response to an optimal spot (in terms of size, direction, velocity) moving on a stationary background inside the excitatory RF (ERF) was compared to in-phase (same direction, same velocity) and anti-phase (opposite direction, same velocity) movement of spot and background. In-phase movement resulted in inhibition of the cell's response (3-100%) in 94% of the cells, while anti-phase movement led to reduced inhibition in 52% of the cells or to facilitation (0.5-327%) in 39% of the cells. By changing the direction of background motion with respect to that of the spot, the directional tuning of the in-phase inhibition and anti-phase facilitation effects was determined. We were able to manipulate the size of the background effects by masking out the background for various proportions of the ERF, and maximizing them by restricting background stimulation to the large inhibitory RF (IRF) surrounding the ERF. These results could be best accounted for by a double-opponent-process mechanism with both RF center and RF surround being directionally selective, but with opposite polarity. It is suggested that this type of mechanism could be involved in the processing of object motion.

Animals↗
PubMed1983

Regional metabolic activity in the rat brain during sleep-wake activity.

[14C]2-Deoxyglucose autoradiography was used to demonstrate regional metabolic activity in the rat brain during wake, slow-wave sleep (SWS), and REM sleep. Data are expressed as values of relative metabolic activity (RMA, regional optic density/mean brain optic density), which show the level of metabolic activity in a region, relative to the mean level of the brain. Regions exhibiting obviously decreased RMA during SWS include the cerebellum, cortical layer IV, and most of the thalamus, including the massa intermedia and lateral geniculate nuclei. Low levels of RMA in sensory relay regions during SWS reflect functional deafference of the brain. In contrast, some limbic regions, including the hypothalamic core and hippocampal dentate fascia, exhibit increased RMA during SWS. Regions exhibiting increased RMA may have functions which are carried on at high levels during sleep. The metabolic appearance of the brain in REM is very different from that in SWS. The reticular core, substantia nigra, hippocampal dentate fascia, and stratum moleculare, and many regions associated with the extrapyramidal motor system, exhibit increased RMA. The cerebellum and ventral thalamic nucleus show decreased RMA, while the lateral thalamic nuclei and cortical layer IV show no metabolic state dependency. In sum, SWS is associated with a general decrease in RMA of sensory and motor areas, and with increased RMA in some limbic regions. RMA is similar in cerebellar and hippocampal regions during REM and SWS. In contrast, RMA in many sensory relay regions does not decrease during REM, and there is REM-specific increase of RMA in some pontomesencephalic regions associated with motor function.

Animals↗
PubMed1983

Evaluation of a tactile vocoder for work recognition.

Normal subjects learned to identify words through a tactile vocoder. The vocoder employed 16 filter channels, each with a bandwidth of 1/3 octave, with center frequencies ranging from 200-8000 Hz. The output of each filter was detected and after logarithmic amplification the resulting outputs were transmitted to a 16-channel solenoid array placed on the subject's ventromedial forearm. Words, spoken "live voice," were used as stimuli; the subject was able to feel both the vocalization of the reader and herself and, most importantly, extensive training was provided. In 40.5 h one subject learned 70 words and a second subject reached criterion on 150 words in the comparatively short time of 55 h. Words that were poorly identified initially were identified more readily with increased experience. Phonetic identification tests showed that the features of voicing, nasality, and frication were reliably recognized, indicating the tactile vocoder will be useful in providing information to complement lipreading. Finally, subjects learned rapidly to generalize word-learning to unfamiliar readers.

Communication Devices for People with Disabilities↗
PubMed1981

Visual response characteristics of neurons in nucleus of basal optic root of pigeons.

This study investigated the response characteristics of single cells in the nucleus of the basal optic root (nBOR) of the accessory optic system of pigeons. One hundred and twenty-one nBOR cells were studied and quantitative data from 87 units indicated that they preferred very large random patterned stimuli, and did not respond to stimuli less than 30 degrees in diameter. In many cases the receptive field encompassed the entire monocular visual field. nBOR cells were directionally sensitive with approximately 70% preferring motion with an upward vector. They responded to very slow velocities in the range of 0.5 degrees to 5.0 degrees s-1, and did not adapt to continuous stimulation. Maximal responses occurred to very large randomly patterned stimuli moving slowly in an upward direction. These response characteristics together with the anatomical connections of the nBOR suggest that this nucleus may be involved in processing self-induced visual motion information required for vertical optokinetic stabilization.

Animals↗
PubMed1981

Moving background patterns reveal double-opponency of directionally specific pigeon tectal neurons.

The experiments reported in this paper were carried out to determine the effect moving background patterns have on the response characteristics of directionally specific neurons in the pigeon optic tectum. First, care was taken to select the optimal single stimulus for each cell, then large textured patterns were added to the test stimulus and moved either "in-phase" or "anti-phase". Altogether 214 cells were studied in 77 white Carneaux pigeons and it was found that all cells below a depth of 400 microns were inhibited by backgrounds moved "in-phase" with the optimal test stimulus, while few cells above this level were affected in any way by backgrounds. All directions of background motion containing an "in-phase" vector resulted in rather profound inhibition of the directional response while directions with an "anti-phase" vector produced less inhibition and sometimes were even facilitated by direct "anti-phase". The velocity tuning curves obtained with an optimal single test stimulus and by "anti-phase" movement of backgrounds were essentially similar. "In-phase" inhibition can also be produced by a second spot stimulus located some distance from the test stimulus. This latter effect was used to map the outer margins of the inhibitory receptive fields of deep tectal neurons displaying these effects and it was found they were extremely large, often in excess of 100 degrees in diameter. When masks were used to prevent the moving background from stimulating the excitatory receptive field "anti-phase" movement always produced facilitation. This suggests a double opponent-process directionally specific receptive field organization. These neurons seem well suited to respond to local (object) motion and to ignore translation of the visual image arising from body, head and eye movements.

Animals↗
PubMed1977

Adaptation and habituation characteristics of tectal neurons in the pigeon.

The adaptation and habituation characteristics produced by the repeated presentation of a moving visual stimulus were studied in single cells in the pigeon's optic tectum. Units located near the surface in the stratum opticum showed little adaptation. However, cells located in deeper layers exhibited varying rates and degrees of adaptation and recovery. Approximately two thirds of the units that adapted, individually showed different rates of adaptation to different directions of movement, thus revealing different receptive field profiles in their adapted and recovered states. Some units were described as habituating since a change in the path of the stimulus through the receptive field or a change in the type of stimulus, resulted in the reinstatement of the initial level of responsiveness.

Adaptation, Physiological↗
PubMed1977

Sensory substitution and the design of an artificial ear.

This paper is concerned with attempts at sensory substitution and in particular with devices that have been designed to substitute for hearing by using the skin as an alternative channel of communication. A review of the literature suggests that the failure or limitations of tactile substitution systems are due, not to the inadequacy of the skin's perceptual processing capacity, but to inappropriate displays, ineffective training methods, or insensitive testing techniques. Specifically, displays have been artificial in that they have typically failed to preserve the information relevant to the modality for which they are supposed to substitute. Furthermore, certain false assumptions and misconceptions have been manifest in testing techniques which have not taken into account the way in which perceptual processes normally develop and operate. The result has been that some important evidence has been ignored or has gone unnoticed and that some promising devices have been prematurely abandoned. In the final section of the review, some suggestions are made concerning the design, application, and evaluation of an artificial ear.

Deafness↗