Search

We experience the visual world as being three-dimensional. A major source of depth information derives from the slightly different views of each eye, leading to small variations in the retinal images ('disparities'). Neurons sensitive to visual disparities are thought to form the neural basis of stereo vision. Barn owls as well as several mammalian species have neurons that are sensitive to visual disparities. But how visual disparities are represented in the brain has been a matter of discussion ever since the first disparity-sensitive neurons were found some 25 years ago. Here we adopt a new approach to this problem and study the neural computation of visual disparities with a paradigm borrowed from auditory research. The measurement of interaural time difference (ITD) has many similarities with the measurement of visual disparity on the formal, algorithmic level. We speculate that the similarities might extend to the level of neural computation. The neural representation of ITD is well understood, and we have studied the representation of disparities with visual stimuli analogous to those successfully used in acoustic experiments. For example, ITD is converted in the brain to a pathlength on an axon that, owing to the finite conduction velocity in neurons, exactly matches the external ITD. This pathlength is called 'characteristic delay'. Our results suggest that there is an analogue of the characteristic delay in stereo vision which we propose to call 'characteristic disparity'.

The role of central and peripheral vision in the production of linear vection was assessed by using displays in which flow structure and sources of internal and external depth information were manipulated. Radial optical flow was more effective for inducing self-motion in both central and peripheral visual fields than was lamellar flow in displays of the same size. The presence of external occlusion information was necessary to induce linear vection when small displays were composed of lamellar flow, whereas the effectiveness of small radial displays did not depend on the availability of occlusion edges.

A Cognitive Shift neurocognitive training module was developed in the attempt to ameliorate cognitive flexibility deficits in chronic schizophrenic patients. A procedural training approach hypothesized the exercise of specific neural network processes, identified from theories of frontal and prefrontal lobe functioning. Three male patients who underwent the intensive program demonstrated significant gains in Wisconsin Card Sorting Test performance, gains that were maintained at a six month reassessment. Expanded Brief Psychiatric Rating Scale (a measure of symptomatology) and Life Skills Profile (a measure of daily functioning) measures showed smaller improvements. The ability to improve cognitive flexibility could have important implications for the treatment of schizophrenia.

The responses of single cells to luminance, color and computer-generated spots, bars, kinematograms, and motion-in-depth stimuli were studied in the nucleus rotundus of pigeons. Systematic electrode penetrations revealed that there are several functionally distinct subdivisions within rotundus where six classes of visual-selective cells cluster. Cells in the dorsal-posterior zone of the nucleus respond selectively to motion in depth (i.e. an expanding or contracting figure in the visual field). Most cells recorded from the dorsal-anterior region responded selectively to the color of the stimulus. The firing rate of the cells in the anterior-central zone, however, is dramatically modulated by changing the level of illumination over the whole visual field. Cells in the ventral subdivision strongly respond to moving occlusion edges and very small moving objects, with either excitatory or inhibitory responses. These results indicate that visual information processing of color, ambient illumination, and motion in depth are segregated into different subdivisions at the level of nucleus rotundus in the avian brain.

Throughout the animal kingdom, the sight of a rapidly approaching object usually signals danger and elicits an escape response. Gibson suggested that the symmetrical expansion of an object's image (looming) is the critical variable determining that the object is on a collision course with the observer. Similarly, large expanding flow-fields like those produced by locomotion may precipitate manoeuvres such as turning or landing. From such observations it has been shown that the optic flow parameter, tau, which specifies time to contact with the approaching object best fits the behavioural data. We describe a subpopulation of neurons in the nucleus rotundus of the pigeon brain that respond selectively to objects moving on a collision course towards the bird.

Illusory self-motion (vection) is thought to be determined by motion in the peripheral visual field, whereas stimulation of more central retinal areas results in object-motion perception. Recent data suggest that vection can be produced by stimulation of the central visual field provided it is configured as a more distant surface. In this study vection strength (tracking speed, onset latency, and the percentage of trials where vection was experienced) and the direction of self-motion produced by displays moving in the central visual field were investigated. Apparent depth, introduced by using kinetic occlusion information, influenced vection strength. Central displays perceived to be in the background elicited stronger vection than identical displays appearing in the foreground. Further, increasing the eccentricity of these displays from the central retina diminished vection strength. If the central and peripheral displays were moved in opposite directions, vection strength was unaffected, and the direction of vection was determined by motion of the central display on almost half of the trials when the centre was far. Near centres produced fewer centre-consistent responses. A complete understanding of linear vection requires that factors such as display size, retinal locus, and apparent depth plane are considered.

We present a statistical analysis of a previously published (Yen, 1983) but heretofore unanalyzed data set on the vertical distributions and diel vertical migration (DVM) of adult females of the marine planktonic copepod Euchaeta elongata in Dabob Bay, Washington, USA. Non-ovigerous females were strongly migratory on all four dates sampled, residing between 75-175 m during the day and at shallower depths during the night, commonly entering the upper 50 m of the water column. In contrast, ovigerous females were non-migratory or weakly migratory, largely remaining between 100-175 m both day and night, and entering the upper 50 m of the water column only rarely. Thus non-ovigerous females always migrated much more strongly, as measured by both amplitude of migration and the proportion of animals migrating, than did ovigerous females. These results led us to hypothesize that differential susceptibility to visually orienting predators was the cause of these differences in DVM behavior in female E. elongata, and we subsequently undertook an experimental study of the feeding selectivity of the copepod's natural predator, Pacific herring (Clupea harengus pallasi). Pacific herring exhibited a highly significant preference for ovigerous over nonovigerous adult female E. elongata. The demographic consequences of variable DVM in adult female E. elongata were investigated by way of life table analyses. Results indicated that under conditions of thermal stratification of the water column there is a distinct demographic disadvantage (reduced rate of realized population growth) incurred by non-migratory or weakly migratory ovigerous females due to delayed egg development at cooler subsurface temperatures. We conclude that ovigerous female E. elongata remain at depth both day and night to avoid visually orienting predators, and that such behavior must afford the copepod a demographic advantage of no less than a 26% reduction in adult mortality to offset the demographic cost of delayed egg development.

The visual response characteristics of single cells in the nucleus isthmi (NI) of pigeons were investigated using standard extracellular recording techniques. The results show that both major components of NI, the parvocellular NI (Ipc) and the magnocellular NI (Imc), have a tight retinotopic organization where nasal regions of the visual field are mapped onto the rostral poles of Ipc and Imc, and temporal regions of the visual field are mapped onto the caudal poles. The more ventral regions of these nuclei receive input from more inferior regions of visual space. The receptive fields (RFs) of both Ipc and Imc are large and oval-shaped, and their long axis is oriented vertically in the visual field. Most RFs are distributed on the contralateral visual horizon, and no binocular responses were found in either Ipc or Imc. All of the excitatory RFs of NI cells were surrounded by large inhibitory regions which participated in the dramatic modulation of the driven visual response when a large background pattern was moved across this zone. Although both Ipc and Imc neurons are driven best by small dark spots, some of them also show orientation selectivity to bars which may result from their oval-shaped RF (74% of Imc cells, 20/38, were orientation selective as compared to 10% of the Ipc cells, 3/30). It is suggested that some tectal cells with small RFs, and which originate from a vertically oriented zone may converge onto a single NI neuron to produce the elliptical shaped receptive fields.

Using standard extracellular techniques, the response properties of neurons in the vestibulocerebellum of the pigeon to movement of a wholefield visual stimulus were determined. Complex spike activity of Purkinje cells was modulated in a direction-selective manner by the stimulus and 94% of cells were binocularly driven. Some neurons preferred the same direction of wholefield motion in both eyes, simulating optic flow which results from self-translation, while others preferred the opposite direction in each eye, simulating optic flow resulting from rotation. Four functional classes of neurons were found: (1) Descent cells preferred upward motion in both eyes; (2) Ascent neurons preferred downward motion in both eyes; (3) Roll cells preferred upward and downward motion in the ipsilateral and contralateral eyes respectively; and (4) Yaw cells preferred forward (temporal to nasal) and backward motion in the ipsilateral and contralateral eyes respectively. The observation that these neurons clearly distinguish rotational and translational optic flow patterns suggest they may play an important role in controlling locomotor activities of the pigeon.

Previous electrophysiological studies have shown that neurons in the nucleus of the basal optic root (nBOR) of the pigeon respond best to wholefield stimuli moving slowly in a particular direction in the contralateral visual field. In this study, we have found that some nBOR neurons respond to wholefield stimulation of both eyes. These binocular neurons have spatially separate receptive fields in both visual fields. Some binocular neurons prefer the same direction of wholefield motion in both eyes, and thus respond best to wholefield visual motion which would result from translation movements of the bird, either ascent, descent, or forward and backward motion. Other neurons prefer opposite directions of wholefield motion in each eye and therefore respond optimally to wholefield visual motion simulating rotational movements of the bird, either roll or yaw. These binocular neurons may play a crucial part in the locomotor behavior of the pigeon by providing visual information distinguishing translational and rotational movements.

Like many diurnal raptors, the American kestrel or sparrow hawk, Falco sparverius, possesses two foveae in each eye. In this study, we used fundus photography and reversed ophthalmoscopy to plot the projection of these foveae onto the visual field, together with other retinal landmarks such as the pecten and ora terminali. From such data, it was determined that the central monocular fovea (CMF) and temporal binocular fovea (TBF) were separated by 36 deg and that the kestrel has 58 deg of binocular overlap when the eyes are appropriately converged. Single-cell and multi-unit recordings were used to systematically explore the tectal surface and map receptive fields (RF) onto a hemispheric screen. A retinotopic map of the tectal surface was produced from such data and revealed an expanded representation for each fovea on the tectum and a systematic increase in RF size from fovea to periphery. The functional significance of this organization is discussed.

The effect of stimulus orientation of letters presented either visually or vibrotactually was examined to obtain basic information on sensory substitution using the tactile sense. The reaction time (RT) to identify the letters F and R presented in normal or mirror-image form at four orientations each was measured. In addition, conditions of 0 degree and 270 degrees of head rotation from vertical and arm rotation from the midline axis were employed. Data from 5 trained subjects showed that vibrotactile RTs were always longer than visual RTs. Stimulus rotation away from normal orientation increased visual RTs significantly but not vibrotactile RTs. Visual orientation effect then seemed to be determined by the body-coordinate system but not the vibrotactile orientation. Although further studies are warranted, from the results of this experiment, any convenient and constant stimulus orientation could be used with a wearable vibrotactile display system to exploit passive touch.

This paper reviews electrophysiological studies of motion processing in the tectofugal and accessory optic systems (AOS), and suggests these are specialized respectively for the analysis of object motion and self motion. Evidence is presented which shows that directionally specific neurons in the tectofugal system process local motion and are inhibited by wholefield motion. These cells respond to kinematograms and moving occlusion edges and may therefore also be involved in figure-ground segregation and depth perception. In contrast, cells in the nucleus of the basal optic root (nBOR), a component of the AOS, respond best to large slowly moving patterns. These cells are directionally selective preferring either upward, downward or backward directions. In the posterior region of the nBOR some cells have been found which are binocular and prefer either the same or opposite directions of motion in the two eyes. Thus, these cells are tuned to respond optimally to either translational or rotational components of wholefield motion and it is suggested these may be involved in the control of posture and locomotion.

The response characteristics of single-units in the nucleus of the basal optic root (nBOR) of the pigeon accessory optic system (AOS) were investigated using standard extracellular techniques. The receptive fields (RFs) were large (20-115 degrees long) and elliptical and were found throughout the contralateral visual field with the exception of the red field. The RFs did not have inhibitory surrounds and there was no evidence of retinotopic organization. Most neurons responded to small moving spots although the optimal stimulus was wholefield motion of a particular direction. Analysis of 166 single-units showed that neurons preferring upward, downward and backward (nasal to temporal) motion were equally abundant (32.5, 32.5 and 31% respectively), while less than 5% preferred forward (temporal to nasal) motion. Mapping studies demonstrated that UP units were located in the dorsal portion of the nucleus; DOWN units were found ventral to UP units; BACK units were found along the ventral surface of the nucleus; and FORWARD units were found in the posterior-dorsolateral margin of the nucleus. Most cells were excited by wholefield motion in the preferred direction and inhibited by motion approximately 180 degrees in the opposite direction, however, some cells lacked the excitatory component while other lacked the inhibitory component. Neurons were grouped into six categories based on the relative contributions of excitation and inhibition. These results are compared with investigations of the AOS of other vertebrates.

1. The histone H1 fractions from rat spleen and liver were used as substrates for two H1-specific protein-lysine N-methyltransferases, V-A and V-B (protein methylase III) from Euglena gracilis. 2. When the enzymatically [methyl-3H]labeled H1 fractions were resolved by two-dimensional gel electrophoresis, four subtypes were found to be methylated (H1b, H1c, H1d and H1e). Both enzymes methylated H1c and H1b to approximately the same extent; H1d and H1e were methylated preferentially by enzyme V-B and V-A, respectively. 3. Histone H1c, [methyl-3H]labeled by the methyltransferase V-A, which had been digested by arginine-specific protease (Arg C protease), showed a single radioactive peptide on HPLC, indicating methylation site specificity of the enzyme. 4. Arg C protease-digestion of [methyl-3H]labeled H1c labeled by methyltransferase V-B indicated that this enzyme methylated two sites on the histone molecule. 5. The histone H1c methylation sites of these two enzymes did not overlap, indicating the two enzymes have different site specificity. 6. In combination with the other results, this suggests that the two enzymes serve discrete purposes, possibly involving the presumed different actions of histone H1 subtypes.

Furazolidone was more active than 3-(1-methyl)-5-nitro-2-imidazolyl-methylideneamino)-2-oxazolidinone (MABN) against a series of 34 isolates of Pasteurella and 11 of Yersinia (formerly designated Pasteurella). However, the nitroimidazole was superior to furazolidone by both subcutaneous and oral routes against a series of mouse infections incited by strains of Pasteurella. It also was superior to furazolidone and sulfaquinoxaline when administered in the diet against two Pasteurella strains in a fowl cholera model infection in chickens. The good in vitro activity of MABN plus its low toxicity suggest its further study as an agent for fowl cholera and the shipping fever complex of cattle.

1. The various types of eye movement exhibited by the cyclopean eye of Daphnia pulex were studied using high speed motion photography. 2. This rudimentary eye, which consists of only 22 ommatidia, can move through approximately 150 degrees in the sagittal plane and 60 degrees in the horizontal plane. 3. Four classes of eye movement were found: (1) a high speed tremor at 16 Hz with an amplitude of 3-4 degrees, which resembles physiological nystagmus, (2) a slow rhythmic scanning movement at 4 Hz, and 5-6 degrees amplitude, (3) large fast eye movements similar to saccadic eye movements and (4) optokinetic nystagmus produced by moving striped patterns. 4. Where the fast tremor occurred concurrently with the slow rhythmic scan, a Fourier analysis revealed that the former was the fourth harmonic of the latter.

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.

A previously developed theory for the transmission of radiation in over moded hollow circular waveguides is extended to cover walls of arbitrary material. The extension relies on approximations to the Fresnel reflection coefficients near grazing angles of incidence for a material characterized by its complex refractive index.

The vascular response to intraluminally and extraluminally administered catecholamines mixed in combination with local anaesthetics has been studied using the isolated perfused rabbit ear artery as the model system. Potentiation of the vascular response to extraluminal adrenaline was observed when prilocaine, lignocaine or cocaine were combined in low concentrations with the vasoconstrictor. No potentiation of the vascular response to extraluminally administered noradrenaline could be demonstrated in the presence of prilocaine or lignocaine. Further, no potentiation to either catecholamine was found if the artery had been denervated or the drugs were applied intraluminally. Possible mechanisms for the potentiation of extraluminally applied adrenaline are discussed.

A geometrical optics theory is presented for the transmission of radiation in hollow overmoded rectangular lightguides with arbitrary wall materials, when the incident beam is injected into the waveguide by focusing to a waist in the guide entrance. Expressions are given for transmission coefficients, both of the total radiation and of that component of the surviving radiation which is plane polarized in a chosen direction.

(14C) 2-deoxyglucose (2-DG) autoradiography was used to examine functional activity in the pigeon accessory optic system (AOS) during visual, vestibular and combined visual-vestibular stimulation. Monocular horizontal whole-field visual stimulation resulted in preferential labelling of the contralateral nucleus of the basal optic root (nBOR), in medial and lateral, but not dorsal regions, as well as the contralateral nucleus lentiformis mesencephali pars magnocellularis (LMmc). Increased activation was also observed bilaterally in LMmc after vestibular stimulation alone. 2-DG accumulation was maximal during combined visual-vestibular stimulation in both nBOR and LMmc.

A precolumn phenylisothiocyanate derivatization method is described for the determination of amino acids in protein hydrolysates from a wide variety of complex food matrixes, with and without performic acid oxidation pretreatment. Analysis of samples that were not pretreated with performic acid was necessary since this pretreatment destroyed an average of 25% of the histidine and 87% of the tyrosine present in the food samples. This method is rapid and reproducible; coefficients of variation between duplicate analyses of the same food item were less than 5% for a majority of the amino acids. Occasionally, variation between duplicate analyses for histidine and tyrosine was greater than 10%. Recoveries of amino acids added to samples were in the 100% range.

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.

1. Methylation of the lysine at residue 72 of yeast apocytochrome c increases its import into mitochondria. 2. Using methylated and unmethylated apocytochrome c as substrate and intact yeast mitochondria and a solubilized mitochondrial fraction as a source of cytochrome c heme lyase, the results show that the methylation state of the apoprotein has no significant effect on its conversion to holoprotein. 3. The above result suggests that the import mechanism is separate from the heme-attaching activity. 4. Unmethylated apocytochrome c was less resistant to a yeast homogenate fraction that methylated apocytochrome c, suggesting that methylation of apocytochrome c alters the conformation of the whole protein.

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.

The effect of several sympathomimetic agents on the efflux of noradrenaline and its metabolites has been evaluated using the ventral artery of the rat tail as the experimental model. This vessel is richly endowed with sympathetic nerves and is therefore well suited to examine the efflux patterns of that transmitter. Etilefrine, tyramine, ephedrine and REN-293 were all found to increase the efflux of 3H-noradrenaline and/or 3H-DOPEG to different degrees from the artery. Possible reasons for this variation in metabolite efflux are discussed.

The haematological indices of Peninsular Arabs (United Arab Emirate Nationals, Yemeni and Omani) have been examined. The most outstanding feature, seen in 40-50% of all subjects, was one of hypochromia, microcytosis associated with erythrocytosis. In approximately 5% the hypochromia was severe (MCH 19-22 pg) and 20% of these were found to have beta thalassaemia trait. In 10% of subjects the hypochromia was moderate (MCH 23-24 pg) and beta thalassaemia was confirmed in only 10%. The remaining 25% had a mild hypochromia (MCH 25-27 pg) and no beta thalassaemia was detected. The cause of the hypochromia in subjects with a normal Hb A2 (30% of the total population) is probably alpha thalassaemia, firstly because in those patients with an MCH of 19-24 pg the other haematological parameters are statistically the same as those with proven beta thalassaemia and, secondly, in those with an MCH of 25-27 pg iron deficiency is not common (6% of the population). The degree and pattern of the distribution of hypochromia of the three major ethnic groups of the Peninsular Arabs could be explained either by different alpha and beta thalassaemia genes being operative or by different degrees of inbreeding of the same genes.

A systematic study was made of visual evoked responses to dynamic random dot stimuli containing controllable, monocularly visible contrast cues. Ratios of dot densities for the centrally presented, disparate figure and the background were varied in steps of 1/8 maximum density between 0/8 and 8/8. The figure was either a square or an equivalent area of nebulous shape. A 30-arc min disparity was compared with binocular nondisparate and monocular conditions. Evoked responses (scalp sites 02, 01, T6, T5) were averaged for each of 24 disparity-contrast-shape conditions. At all contrast levels, response amplitudes and latency over the left hemisphere was significantly greater than over the right hemisphere. For 30 arc min disparity, amplitudes in the 8/8 condition were significantly smaller than in conditions where stimulus/background contrast could afford monocular depth cues. Hemisphere amplitude differences diminished as contrast decreased. Factor analyses isolated two overlapping components in the response to disparate stimuli. The earlier, at 236 ms latency, may index the stereoscopic stimulus features. The later, at 295 ms, peaking at maximum contrast and present in all suprathreshold nondisparity conditions, may index contrast features of the stimulus. The results indicate the importance of controlling dot density ratios in electrophysiological studies of the stereoscopic response to random dot stimuli.

Identification of open set words, by an experienced normal hearing subject using the tactile vocoder developed at Queen's University, was examined. The tactile vocoder filters and processes the acoustic waveform into 16 filter channels, each of which controls a vibrator on the skin surface. After acquiring a 250-word vocabulary through the tactile vocoder, the subject was presented with three sets of 1000 different open set words in three reception conditions. The percentages of words correctly identified in the tactile vocoder (TV), lipreading (L), and lipreading plus tactile vocoder (L + TV) conditions were 8.8, 39.4, and 68.7 percent respectively. Phonemic analysis of stimulus/response pairs revealed that 36.7, 64.9 and 85.5 percent of the phonemes were correctly identified in TV, L, and L + TV conditions, respectively, indicating that incorrect-response words often contained many correct phonemes. Also, syllabic stress of stimulus and response words was identical 88 percent of the time in the TV condition. Important information about speech was transmitted through the tactile vocoder.

The effects of etilefrine on the ventral caudal artery of the rat have been examined in the presence of agents modifying sympathetic nerve function. Catecholamine levels were also measured in adjacent segments of artery to those studied pharmacologically and an attempt made to relate vascular response to etilefrine (and tyramine) with catecholamine content. Both guanethidine and reserpine produced significant attenuation of the vascular effects of etilefrine and tyramine. Pre-treatment with a monoamine oxidase inhibitor caused an increase in tissue catecholamine levels but, paradoxically, depressed the vascular response to etilefrine. The significance of some of the findings in terms of an indirect component to etilefrine's action are discussed.

Multiple ureteral diverticula are rare and not previously reported in Scandinavian literature. Various etiologic factors have been considered. In our opinion, it is a congenital abnormality, not in itself demanding specific therapy. Diverticulosis ureteris is not seen at ordinary excretory pyelography, and only occasionally at a high volume excretory pyelography with compression. They are best visualized by retrograde pyelography, and the incidence may, therefore, be higher than hitherto anticipated.

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.

The blood vessels in the rabbit ear have been used to investigate the effects of octapressin on vascular smooth muscle. Continuous administration of this drug resulted in tachphlatis. Cocaine enhanced the response of the ear to octapressin; however, this potentiation was not evident when phentolamine was concurrently added to the perfusate. Denervation and reserpinisation of the ear also eliminated the potentiation of octapressin's response by cocaine. The results suggest that there is a small, indirect sympathomimetic component involved in octapressin's action on the vasculature.

[14C]2-deoxyglucose autoradiography was used to show cerebral and regional cerebral metabolism during slow-wave sleep (SWS) and rapid-eye-movement sleep (REM) in the cat. Lower levels of mean cerebral metabolism, reflecting cerebral energy conservation, were associated with SWS. A clear link between REM and mean cerebral metabolism was not observed. At the regional level, SWS was associated with markedly low metabolism in thalamic sensory relays and in cortex. REM was associated with relatively low metabolism in the cerebellum, but with relatively high metabolism in the hippocampus, and in some 'motor' regions including the trigeminal and red nuclei. Thus, SWS was linked to cerebral energy conservation and to particularly low levels of functional activity in cortical and sub-cortical sensory regions. REM was unlike SWS in that: REM did not appear to be strongly linked to cerebral energy conservation; REM was linked to metabolism in fewer brain regions than was SWS; and most REM-linked regions exhibited relatively high levels of metabolism. In addition, while SWS was most clearly associated with functional activity in sensory regions, REM was linked to functional activity in a small number of limbic and motor regions. In sum, SWS and REM are associated with distinctive cerebral metabolic and functional states.

Most neurons in cat striate visual cortex show inhibitory effects when moving contours are presented beyond the limits of classic receptive field regions. Facilitatory effects are also present in about 40% of simple cells. Here, we report a highly specific form of this facilitation, mediated only by neurons possessing both an orientation tuning matched to the test unit, and a receptive field position aligned with its long axis. This finding illustrates one of the intracortical interconnection schemes hypothesized by Mitchison and Crick (1982). Periodic clustering in long, intrinsic axons may signify a neuron seeking specific functional interactions like these across columnar systems in both the spatial and orientation domains.