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In foraging tasks, multiple targets must be found within a single display. The targets can be of one or more types, typically surrounded by numerous distractors. Visual attention has traditionally been studied with single target search tasks, but adding more targets to the search display results in several additional measures of interest, such as how attention is oriented to different features and locations over time. We measured foraging among five age groups: Children in Grades 1, 4, 7, and 10, as well as adults, using both simple feature foraging tasks and more challenging conjunction foraging tasks, with two target types per task. We assessed participants’ foraging organization, or systematicity when selecting all the targets within the foraging display, on four measures: Intertarget distance, number of intersections, best-r, and the percentage above optimal path length (PAO). We found that foraging organization increases with age, in both simple feature-based foraging and more complex foraging for targets defined by feature conjunctions, and that feature foraging was more organized than conjunction foraging. Separate analyses for different target types indicated that children’s, and to some extent adults’, conjunction foraging consisted of two relatively organized foraging paths through the display where one target type is exhaustively selected before the other target type is selected. Lastly, we found that the development of foraging organization is closely related to the development of other foraging measures. Our results suggest that measuring foraging organization is a promising avenue for further research into the development of visual orienting.

The non-invasive neuromodulation technique tDCS offers the promise of a low-cost tool for both research and clinical applications in psychology, psychiatry, and neuroscience. However, findings regarding its efficacy are often equivocal. A key issue is that the clinical and cognitive applications studied are often complex and thus effects of tDCS are difficult to predict given its known effects on the basic underlying neurophysiology, namely alterations in cortical inhibition-excitation balance. As such, it may be beneficial to assess the effects of tDCS in tasks whose performance has a clear link to cortical inhibition-excitation balance such as the visual orientation discrimination task (ODT). In prior studies in our laboratory, no practice effects were found during 2 consecutive runs of the ODT, thus in the current investigation, to examine the effects of tDCS, subjects received 10 min of 2 mA occipital tDCS (sham, anode, cathode) between a first and second run of ODT. Surprisingly, subjects’ performance significantly improved in the second run of ODT compared to the first one regardless of the tDCS stimulation type they received (anodal, cathodal, or sham-tDCS). Possible causes for such an improvement could have been due to either a generic “placebo” effect of tDCS (as all subjects received some form of tDCS) or an increased delay period between the two runs of ODT of the current study compared to our previous work (10-min duration required to administer tDCS as opposed to ~ 2 min in previous studies as a “break”). As such, we tested these two possibilities with a subsequent experiment in which subjects received 2-min or 10-min delay between the 2 runs (with no tDCS) or 10 min of sham-tDCS. Only sham-tDCS resulted in improved performance thus these data add to a growing literature suggesting that tDCS has powerful placebo effect that may occur even in the absence of active cortical modulation.

Precise temporal coding is necessary for proper acoustic analysis. However, at cortical level, forward suppression appears to limit the ability of neurons to extract temporal information from natural sound sequences. Here we studied how temporal processing can be maintained in the bats’ cortex in the presence of suppression evoked by natural echolocation streams that are relevant to the bats’ behavior. We show that cortical neurons tuned to target-distance actually profit from forward suppression induced by natural echolocation sequences. These neurons can more precisely extract target distance information when they are stimulated with natural echolocation sequences than during stimulation with isolated call-echo pairs. We conclude that forward suppression does for time domain tuning what lateral inhibition does for selectivity forms such as auditory frequency tuning and visual orientation tuning. When talking about cortical processing, suppression should be seen as a mechanistic tool rather than a limiting element.

In order to understand the visual orientation mechanisms of the male black chafer Holotrichia loochooana loochooana to females, we examined male behavioral response to colored objects (lures) when female sex pheromone was present. In the field, males landed more frequently on darker lures than on lighter ones of the same color. Among lures of different colors but with the same brightness, males preferred landing on black, blue, or red ones to green or grey ones. The reflectance intensities of preferred lures were weaker than those of green and grey in the range of 540–580 nm. This range is considered to affect choice by males. When females perch on the leaf edges of the food plant to adopt a calling posture, the dominant background color is that of the leaves (i.e., green). This means that the landing target forms a silhouette (dark spot) which is prominent against a background of green leaves, providing maximum visual acuity for mating.

The aim of the present study was to investigate the distance at which vertical black and white stripes (contrast boundaries) elicit object-related behavioral responses in 6th instar and adults of the praying mantis Mantis religiosa. The mantids reacted when the contrast boundaries were not further away than 60 cm. However, with increasing distance (>20 cm), the contrast boundaries became progressively less significant for the mantids. Jumps/preparation of jumps could be observed between 10 and 30 cm. The results are supportive for distance measurement of up to 20–30 cm, which corresponds to distance accessible for the insect. It seems that image motion cues induced by peering movements play an important role.

In apes, four criteria are set to explore referen- tial and intentional communication: (1) successive visual orienting between a partner and distant targets, (2) the pres- ence of apparent attention-getting behaviours, (3) the requirement of an audience to exhibit the behaviours, and (4) the inXuence of the direction of attention of an observer on the behaviours. The present study aimed at identifying these criteria in behaviours used by dogs in communicative episodes with their owner when their toy is out of reach, i.e. gaze at a hidden target or at the owner, gaze alternation between a hidden target and the owner, vocalisations and contacts. In this study, an additional variable was analysed: the position of the dog in relation to the location of the tar- get. Dogs witnessed the hiding of a favourite toy, in a place where they could not get access to. We analysed how dogs engaged in communicative deictic behaviours in the pres- ence of their owner; four heights of the target were tested. To control for the motivational eVects of the toy on the dogs' behaviour and for the referential nature of the behav- iours, observations were staged where only the toy or only the owner was present, for one of the four heights. The results show that gazing at the container and gaze alterna- tion were used as functionally referential and intentional communicative behaviours. Behavioural patterns of dog position, the new variable, fulWlled the operational criteria for functionally referential behaviour and a subset of opera- tional criteria for intentional communication: the dogs used their own position as a local enhancement signal. Finally, our results suggest that the dogs gazed at their owner at optimal locations in the experimental area, with respect to the target height and their owner's (or their own) line of gaze.

An involvement of pituitary adenylate cyclase activating polypeptide-specific receptor type 1 (PAC1-R) in behavioral performance of retrieval of memory upon the stimulation of perception of sensory modality was investigated in mice. Eighteen heterozygous (-/+) transgenic mutant PAC1-R-deficient mice ((-/+) mice) and 18 wild-type (+/+) mice of littermates ((+/+) mice) as a control were used. No homozygous (-/-) transgenic mutant PAC1-R-deficit mouse was bred in our colony. It was observed that; (1) changing a single alley in the multiple mazes interfered with retrieval of memory in both (-/+) mice and (+/+) mice, and they made considerable errors; (2) a rotation of the multiple mazes for 180 degrees in relation to the geomagnetic field made also considerable errors, but in only (+/+) mice and not in (-/+) mice; and (3) an exposure for perception of fear signals made also considerable errors, but in only (+/+) mice and not in (-/+) mice. It is inferred that PAC1-R may play a gating role in passage permitting through perception of geomagnetic orientation and fear signals, but not perception of visual orientation, and it regulates behavioral performance in retrieval of memory in mice.

Means are presented for improving efficiency as a result of piscicultural measures in multipurpose water bodies.

We report a dramatic change in the arrival time of little penguins Eudyptula minor at their breeding colony when a heavy low-level fog was present on the southern beaches of Phillip Island, Australia. On the evening of 21 December 2002, only 5% of penguins arrived at the expected time, and the peak time at arrival that night was 2 h behind the peak arrival times of previous and subsequent days. It appears that little penguins were unable or unwilling to return to the colony under the low visibility caused by the fog. Only half (52%) of the average number of penguins returned to the colony on the evening of the fog. We propose two explanations for our observation. First, penguins could have been close to the colony but did not come ashore in conditions of poor visibility to avoid predation. Secondly, the extensive fog may have affected the orientation of the penguins and they were unable to find their way back home. Our results could serve as indirect evidence for both hypotheses.

Two experiments are presented which examine the effect of onset and offset cues on early occurring attentional cueing effects and later occurring inhibition of return (IOR). The first experiment compared the effects of single onset cues, single offset cues, and simultaneous onset and offset cues (at opposite locations) at a 100-ms stimulus-onset-asynchrony (SOA) and IOR at a 900-ms SOA. Whereas the first experiment examined these conditions with choice localization keypress responses, the second experiment used simple detection keypress responses. Both experiments found that onset and offset cues presented in isolation produce early facilitation and late IOR. When onset and offset cues were simultaneously presented, facilitation but not IOR was found with localization responses, while neither facilitation or IOR was found with detection responses. Overall, these findings suggest that offset cues can be treated in the same manner as onset cues by the attentional system, although the onset cues may have priority in orienting attention when targets must be localized in space.

Advances in understanding the neural control of saccades (visual orienting movements made when the head is prevented from moving) stem largely from early modeling efforts which provided a framework for developing and testing hypotheses about the relationships between neural activity and observed behaviors. When the head is free to move, visual orienting is often accomplished with coordinated movements of the eyes and head. A recent description of the temporal progression (i.e., kinematics) of these movements led to the hypothesis that eye and head control signals interact. This hypothesis is now formalized as a control systems model which accounts for existing data and makes explicit predictions about the neural control of orienting gaze shifts.

Modules of neurons sharing a common property are a basic organizational feature of mammalian sensory cortex. Primary visual cortex (V1) is characterized by orientation modules--groups of cells that share a preferred stimulus orientation--which are organized into a highly ordered orientation map. Here we show that in ferrets in which retinal projections are routed into the auditory pathway, visually responsive neurons in 'rewired' primary auditory cortex are also organized into orientation modules. The orientation tuning of neurons within these modules is comparable to the tuning of cells in V1 but the orientation map is less orderly. Horizontal connections in rewired cortex are more patchy and periodic than connections in normal auditory cortex, but less so than connections in V1. These data show that afferent activity has a profound influence on diverse components of cortical circuitry, including thalamocortical and local intracortical connections, which are involved in the generation of orientation tuning, and long-range horizontal connections, which are important in creating an orientation map.

Posner and Cohen (1984) and Maylor (1985) initially observed that a luminance change produces both facilitatory and inhibitory effects on subsequent detection. While Posner and Cohen claimed that the facilitatory effect was mapped in retinotopic coordinates, they showed that inhibition of return (IOR) was mapped in “environmental coordinates.” Tipper and colleagues (Tipper, Driver, & Weaver, 1991; Tipper et al., 1997; Tipper, Weaver, Jerreat, & Burak, 1994) and Abrams and Dobkin (1994b) have recently reported that IOR can be object based, but contradictory results have also been reported (Muller & von Muhlenen, 1996). Here we report six experiments showing that an uninformative peripheral cue can generate either facilitatory or inhibitory object-based effects that can tag moving objects and that can persist for several hundred milliseconds. Although the boundary conditions determining which effect will be manifest remain to be defined, the present results suggest that facilitation and inhibition are generated independently, rather than being components of the same biphasic process.

Normal subjects were presented with a simple line drawing of a face looking left, right, or straight ahead. A target letter F or T then appeared to the left or the right of the face. All subjects participated in target detection, localization, and identification response conditions. Although subjects were told that the line drawing’s gaze direction (the cue) did not predict where the target would occur, response time in all three conditions was reliably faster when gaze was toward versus away from the target. This study provides evidence for covert, reflexive orienting to peripheral locations in response to uninformative gaze shifts presented at fixation. The implications for theories of social attention and visual orienting are discussed, and the brain mechanisms that may underlie this phenomenon are considered.

Visual orientation greatly relies on the evaluation of the motion patterns received by the eyes when the animal moves around. In a combination of both behavioral and neurophysiological analysis and modeling, the mechanisms are established by which the visual system of the fly extracts three types of basic retinal motion patterns: Coherent retinal large-field motion as is induced during deviations of the animal from its course, image expansion occurring when the animal approaches an obstacle, and relative motion which is induced when a nearby object is passed in front of its background. Separate neuronal networks are specifically tuned to each of these motion patterns and make use of them in three different orientation tasks: in compensatory course stabilization, the control of landing behavior, and the fixation of objects.

Background. Several studies using spatial cueing paradigms have demonstrated that seeing gaze direction may trigger a reflexive visual orienting in the gazed-at direction. Recently, it has been reported that facial expression may enhance the reflexive orienting of attention to gaze stimuli. However, some researchers have also suggested that, rather than facilitating attentional orienting away from the face, emotional expressions may, in fact, delay or prevent orienting. In the present study we investigated the effects of facial expression and gaze direction on a visual orienting oculomotor task to test whether an angry face may or may not interfere with visual orienting. Method. Participants performed an oculomotor task in which they had to make a saccade towards one of two lateral targets, depending upon the colour of the fixation dot which appeared at the centre of the computer screen. The instruction dot remained visible for 50ms and then disappeared. At different time intervals (stimulus onset asynchronies, SOAs: 50, 100, 150 ms) following the onset of the instruction cue, a real face (gazing either to the right or to the left) was presented at the centre of the monitor. Gaze direction could be congruent or incongruent with respect to the instruction and target location. Facial expression was also manipulated. In half of the trials the diverted gaze (i.e., congruent or incongruent) appeared with an angry expression, whereas in the other half the face had a neutral expression. Participants were instructed to saccade either to the target on the left or to the target on the right (the targets were visible throughout the trial), as indicated by the instruction dot, while completely disregarding the face because it was irrelevant for the task. Results. Eye movement recordings on correct trials showed that saccades congruent with the direction of the distracting gaze had shorter latencies than incongruent ones. However, the time-course of this effect varied depending on facial expression. With a neutral expression, the congruency effect was found only at the shortest SOA (50 ms). On the contrary, for angry face the congruency effect occurred at the longer SOAs. These findings suggest that gaze direction (even when task-irrelevant) is capable of interfering with over orienting of visual attention, and that faces with an angry expression may hold attention and affect its orienting longer than a neutral expression.

1 -Foragers of the harvester antPheidole militicida travel along well defined trunk trails to their foraging grounds. These trails can be subdivided into three major sections: trunk, branches and twigs (fig. 2). 2 -Trunk and branches can last several days or even weeks, whereas the design of the outermost twig section changes daily. 3 -The persistence of a trunk route depends on the amount of seeds available in the foraging area to which it leads. When an area has been greatly depleted of its suitable seed supplies, the trunk route is abandoned and a new one, leading to a different area, is established. 4 -Trail pheromones, originating from the poison gland of workers, play a major role in regulating the activity along the foraging routes. They contain not only a recruitment signal but also an orientation cue, which is responsible at least in part for the remarkable precision of orientation by workers during their foraging excursions. 5 -The trail pheromones are highly species-specific in those sympatricPheidole species that employ a trunk trail foraging system (P. militicida, P. tucsonica, P. rugulosa). 6 -Although the so-called soldier caste ofP. militicida follows natural as well as artificial trails drawn with worker poison gland secretions, their own poison gland substance does not contain a trail pheromone. 7 -It was demonstrated that the foraging pathways ofP. militicida are marked by very enduring chemical cues, which might be distinct from the poison gland trail pheromone. 8 -Not only chemical cues but also visual guidelines seem to play a role in the directional maintenance of the trunk route. The remarkable route fidelity of foragers ofP. militicida seems to depend in part on specific landmarks. 9 -The well defined, chemically marked trunk trails enableP. militicida to conduct extensive foraging excursions during the night, when almost no visual orientation seems possible. 10 -The trunk route foraging system ofP. militicida is compared with that ofPogonomyrmex rugosus andP. barbatus and with the column foraging ofveromessor.

Heart rate and electrodermal responding were recorded while 48 subjects viewed eight discrete presentations of a visual orienting stimulus. Subjects were split into Internals and Externals according to scores on the Locus of Control scale (Rotter, 1966). A beat-by-beat analysis of the heart-rate data collapsed over all eight stimulus trials indicated that Externals exhibited a significant decrease in heart rate in response to the stimulus, whereas Internals exhibited no significant change in heart rate. A further analysis of the heart-rate results during the first stimulus trial indicated that Internals displayed a heart-rate response consisting of an initial increase in heart rate followed by a significant decrease in heart rate 4 heart beats after the initiation of the stimulus. In contrast, Externals displayed a large and significant decrease in heart rate during the 1st heart beat after the initiation of the first stimulus. The electrodermal data indicated that Externals were more likely to exhibit electrodermal activity and Internals were less likely to display electrodermal activity during the first stimulus trial. It is suggested that the differential autonomic responsivity noted for Internals and Externals during the task may indicate that Externals attend more to environmental stimuli than Internals.

The visual orientation towards single black stripes and more complex patterns, comprising smooth gradients of brightness was studied in walking gypsy moths. Depending on the width of a black stripe, up to three walking directions are preferred within one stimulus situation: towards the centre of the stripe and towards a region within the stripe closer to each edge. The observed responses are explained by a compromise between edge-fixation and negative phototaxis. This hypothesis turned out to be also applicable to more complex patterns.

Leptothorax unifasciatus workers use both chemical and visual cues when foraging. A visual orientation based on menotactical cues (60 watt light-bulb) and environmental cues (laboratory surroundings) dominate over a chemical orientation. The learning response to a 60 watt light-bulb cue occurs after a single trip to the food source. Workers lay down a trail when foraging which helps them to orient themselves but does not recruit other nestmates. Such trails are distinguished and preferred even when superposed by several other nestmates' trails. Nevertheless, the foragers are able to follow their nestmates' trails if their own is somehow missing. Newly recruited ants are unable to orient along chemical trails.

Visually guided locomotion toward goal doors designated by various cues was assessed in normal hamsters, hamsters with undercuts of the superior colliculus, and hamsters with neonatal lesions of the superior colliculus. Scanning of visual arrays, orientation to novel stimuli, and orientation to sunflower seeds were assessed in the same animals. Collicular lesions produced no deficit in accuracy of choice of goal door, type of route taken, or speed of locomotion. By contrast, the same hamsters showed major deficits in spontaneous scanning and orientation to stimuli in the visual periphery. Hamsters with neonatal and adult collicular lesions performed identically on every task except orientation to sunflower seeds presented at various locations in the visual field; adult operates were somewhat more variable in their performance. The implications of these results for the concept of encephalization of function and the phylogeny of the optic tectum are discussed.

A radioimmunoassay (RIA) was developed for the quantification of caffeine in saliva. The mean salivary caffeine level for this sample of 40 full-term, AGA, healthy 1-2 day old human neonates was consistent with levels reported in previous studies. Salivary caffeine was significantly correlated with the number of state changes and startles observed during administration of the Brazelton Neonatal Behavior Assessment Scale. There was also a nonsignificant trend correlating salivary caffeine with visual orienting and consolability.

A neural model is constructed based on the structure of a visual orientation hypercolumn in mammalian striate cortex. It is then assumed that the perceived orientation of visual contours is determined by the pattern of neuronal activity across orientation columns. Using statistical estimation theory, limits on the precision of orientation estimation and discrimination are calculated. These limits are functions of single unit response properties such as orientation tuning width, response amplitude and response variability, as well as the degree of organization in the neural network. It is shown that a network of modest size, consisting of broadly orientation selective units, can reliably discriminate orientation with a precision equivalent to human performance. Of the various network parameters, the discrimination threshold depends most critically on the number of cells in the hypercolumn. The form of the dependence on cell number correctly predicts the results of psychophysical studies of orientation discrimination. The model system's performance is also consistent with psychophysical data in two situations in which human performance is not optimal. First, interference with orientation discrimination occurs when multiple stimuli activate cells in the same hypercolumn. Second, systematic errors in the estimation of orientation can occur when a stimulus is composed of intersecting lines. The results demonstrate that it is possible to relate neural activity to visual performance by an examination of the pattern of activity across orientation columns. This provides support for the hypothesis that perceived orientation is determined by the distributed pattern of neural activity. The results also encourage the view that limits on visual discrimination are determined by the responses of many neurons rather than the sensitivity of individual cells.

This study concerned the processing of the outputs of visual orientation-sensitive mechanisms by higher order mechanisms. Ss performed a simultaneous detection-recognition task. Variation in the number of possible orientations of a single straight line produced only slight, if any, changes in detection or recognition performance as compared with findings from similar auditory frequency experiments. It was concluded that the outputs of all orientation-sensitive mechanisms are examined by higher order mechanisms. As the angular separation of two possible orientations increased, the data showed that recognition improved in keeping with other reported findings. Comparison of detection with recognition indicated that the latter, under certain conditions, was superior to the former.

The rod-and-frame effect (RFE) was investigated with the use of a frame that oscillated about an axis at its center at five different frequencies, ranging from .013 to .213 Hz. The resultant RFE shifted continuously with the roll motion of the frame, and it was significantly larger at the lowest frequency (.013 Hz) than under comparable static conditions. The dynamic RFE was lowest at the higher oscillation frequencies. Oscillatory roll vection--apparent self-motion--was reported by 3 of the 9 subjects when the frame was oscillating at its highest frequency (.213 Hz). The subjects yielded large increases in the RFE during the sessions with reports of vection. Surrounding the kinetic frame with a circular contour eliminated all reports of vection and significantly interacted with frequency to reduce the RFE--but only at low frequencies. The reduction amounted to 21.2% averaged over all 9 subjects at the three lowest frequencies. A surrounding contour, therefore, suppressed low-frequency kinetic visual orientation information that might otherwise have produced larger changes in apparent self-orientation and perceived vertical. Vection-sensitive subjects differed from nonvection subjects by exhibiting (1) a high-frequency fall-off in real-motion gain, (2) a high-frequency enhancement in illusory-motion gain, and (3) only a small and nonsignificant increase in illusory-movement phase lag with increases in frequency.

Two-dimensional normally distributed random dot patterns were used in two experiments on visual orientation estimation. In the first experiment the patterns differed in their sample correlation and in dot number. In the second one the number of dots was maintained constant but the patterns were generated as a superposition of two normally distributed orthogonal sets composed of different number of dots. In both experiments the estimated orientation depended on stimuli correlation - with increasing correlation the estimated orientation gets closer to the orientation of the least square distance axis of the pattern. Even at very low unsignificant correlations there still remained a hint about stimulus orientation which was not estimated at random. Equalizing consecutively the number of dots in the two orthogonal dot patterns during the second experiment did not result in chance performance either. The bimodal angular distributions of the obtained responses permitted to approach the problem of orientation ambiguity. The results are discussed in terms of optimization processes taking place in the visual system.

Previous research indicates that a tilted visual display is capable of inducing eye torsion and an illusion of self-tilt in objectively upright observers. These effects may contribute to performance errors on the rod-and-frame test by rotating the perceived axes of visual space toward the tilted frame. The kinesthetic-matching method was used in the present study to see whether an effect of the visual orientation contrast between red and frame sides might also contribute to rod-and-frame test performance. Observers aligned invisible hand-held rods with the visual rod at various tilts under a control condition when the frame was absent, and under experimental conditions with the frame upright or set at 45°. The frame induced matching errors in the direction away from the frame sides which were most nearly parallel to the rod. Since no rotation of apparent visual axes should occur under these conditions, the data suggest that an orientation contrast effect is involved in the rod-and-frame test.

Visual judgments of orientation were investigated during (effect) and after (aftereffect) different body postures. In Experiment 1 four trained Ss made apparent verticality (AV) judgments before and after 2 min in each of seven orientations: head tilt left and right, body tilt left and right, trunk tilt left and right and a control condition with head ’and body upright. The aftereffect was significant for all postures excepting trunk tilt left and the control. The aftereffect from head tilt was greater than that from the same degree of body tilt, and that in the trunk tilt condition was in the same direction as’ predicted from neck stimulation. In Experiment 2, 30 Ss made AV judgments during tilt in the same seven postures. The E-phenomenon resulted from both head and body tilts, and an effect was found for trunk tilt in the direction predicted from neck stimulation. The results are discussed in terms of the otolith, neck, and trunk receptor systems.

The eye tracks of 29 children (aged 2-7 years) were recorded by a reflection eye camera while they were looking ata4by 4 matrix of 16 white geometric shapes. When a circle suddenly changed to red, the children immediately looked at it for two-thirds of the presentation time, a reading which was 16 times the initial level before this novel color was introduced. With repeated presentations of the novel red circle display, progressively fewer fixations fell on the red circle. After 20 trials, this habituation was incomplete, and the red circle was still drawing six times the initial amount of looking found on the original white circle. Ss were apparently relatively slow to form a neural representation of the visual environment due to the wide range of choices in the original display. The age of the children had no monotonic effect on the high, and virtually equal, initial visual concentration, nor on the rate at which habituation occurred. An interesting contrast, therefore, appeared between these data and the marked age effects noted by others in the recognition of letter-like shapes. Unlike recognition tasks, orienting and habituation need a minimum of stimulus interpretation. Children, even as young as 2 years, have demonstrated a remarkable efficiency in these processes of orienting and habituation to novelty.

1. Hypotheses concerning the neural mechanisms by which the back swimmerNotonecta undulata locates prey have been examined using behavioral tests. 2. The results are consistent with the following hypotheses: A. The receptor nearest the target controls the direction of the turn which is elicited by a stimulus (Figs. 2 and 3). B. Sensory input via a given receptor is capable of eliciting a very limited range of motor responses (Fig. 3). C. There are inhibitory interactions between receptors at some level of the central nervous system (Figs. 6 and 7C). 3. A neuronal network analogous to a lateral inhibitory network is proposed to be the neural basis for the orientation (Fig. 5).

The aftereffects of viewing diagonal lines for 50, 500, and 1,000 msec were measured by the speed and accuracy of identification of a variably tilted test grating. Significant RT and tilt aftereffects were found as functions of the duration of orientation-specific adaptation and the angle of separation between inspection and test lines. The results throw light on anchoring effects of the main visual coordinates and support a structural interpretation of orientational selectivity in human vision.

Insect visual orientation is mostly considered as a stimulus-response phenomenon1,2. This view may be challenged in Drosophila melanogaster by genetic dissection, as we show here. When suspended in a fixed position in a flight simulator3, which transforms torque into angular velocity of the panorama, Drosophila establishes a state of zero net rotation of the panorama (optomotor balance4). The genetic variant rol sol, with greatly reduced optic lobes, is entirely motion-blind but can respond with turning manoeuvres to the position of landmarks. Mutant flies maintain optomotor balance but do so irrespective of the sign of the visual feedback in the simulator, that is, whether angular velocity is inversely or directly proportional to torque. Using the amount, but not the direction, of pattern motion the flies stabilize the panorama by trying out which value of torque has the desired effect. We conclude that operant behaviour is a basic constituent of visual orientation in flies.

The visual vertical with 30 deg right head tilt was determined by three psychophysical procedures: the methods of adjustment with and without bracketing and a modified up-and-down (staircase) method. The visual vertical was on the opposite side of the gravitational vertical to tilt (E-effect) under all conditions. However, the E-effect measured by the up-and-down method was significantly larger than the combined average of the two methods of adjustment. The methods of adjustment with and without bracketing yielded approximately the same means for the visual vertical when averaged over starting positions, but differed significantly in the linear trends taken over starting positions. A greater error of anticipation resulted when bracketing was not allowed.

Mongolian gerbils received either lesions of the superior colliculus, small lesions of the uncrossed efferents of the superior colliculus, knifecuts of the dorsal tegmental decussation, or sham operations. The animals were subsequently tested for avoidance of overhead visual threat, orientation and locomotion toward small targets, and negotiation of a large barrier in order to reach a small target. Animals with collicular lesions showed no responses to overhead threat and had severe deficits in orienting to small targets. Animals with lesions of the uncrossed tectal efferents showed diminished responses to overhead threat but had no deficits in orienting to targets. Animals with lesions of the dorsal tegmental decussation showed only slight reductions in responses to overhead threats but clear impairments in the orientation tasks. The impairments in orientation, however, were less severe than those seen in collicular animals. Animals in all groups were able to negotiate barriers efficiently. These results suggest that separate output pathways of the superior colliculus mediate different types of visuomotor behaviours. The results further suggest that visual orientation to small targets does not depend completely on output through the predorsal bundle, but must also involve other collicular outputs.

The compensatory optomotor turning reaction as well as the turning response towards objects play an important role in visual orientation. On the basis of behavioural experiments under precisely defined stimulus conditions it is concluded that in female house-flies these motion-dependent responses are mediated by two parallel control systems with different dynamic and spatial integration properties. One of them (lsquolarge-field systemrsquo) is most sensitive to the motion of large textured patterns and controls the yaw torque mainly at low oscillation frequencies (below 0.1 Hz) of the stimulus panorama. In contrast, the other control system (lsquosmall-field systemrsquo) is tuned to the detection of relatively small moving patterns and shows its strongest responses at high oscillation frequencies (between 1 and 4 Hz), i.e. in a frequency range where the large-field system contributes to the turning response with only a relatively small gain. In free flight, house-flies do not curve smoothly but in sequences of rapid turns which induce retinal large-field motion of continually changing sign (Wagner 1986b). The dynamic properties of the large-field system might thus be interpreted as a simple strategy to almost eliminate the unwanted optomotor yaw torque induced by active self-motion. In contrast, the small-field system might still be operational under these conditions.

The use of a laser microbeam has allowed us to ablate specific small groups of cells deep in the larval brain of the housefly Musca domestica, without damage to overlying tissues. The ablation results in various specific alterations in brain structure and behaviour of adult flies. In the experiments described here, a set of large horizontal and vertical neurones on one side of the adult optic lobes was ablated. These neurones are known to be directionally motion sensitive and are thought to play an essential part in visual orientation of the fly1–8. However, visually guided orientation behaviour towards single objects by flies lacking the large horizontal and vertical neurones on one side was not significantly different from the behaviour of normal flies, although the response to moving gratings was reduced on the ablated side. Therefore we suggest that other sets of nerve cells are involved in the information processing of single moving objects, whereas the horizontal and vertical cells seem to be implicated in ordinary optomotor flight stabilization.

Polarized UV light from a platform on the ground can attract backswimmers and elicit plunge reactions. Threshold intensity is independent of the overall UV-intensity in the surrounding space. Unpolarized UV light attracts the animals only when the intensity is higher than that of the surroundings. These results show that polarized UV light can be discriminated from unpolarized UV light independently of intensity.

Human Visual Orientation. By Ian P. Howard. Pp.697. ISBN 0-471-27946-3. (Wiley: 1982.) £25, $59.95.

Asch and Witkin showed that when an observer adjusted a bar on the far wall of a miniature room tilted at 22° laterally, the apparent vertical of the bar was displaced about 10°–14° in the direction of room tilt1. We report here an experiment which shows that earlier exposure to a similarly tilted room produces the same direction of change in apparent verticality when a luminous bar is adjusted in darkness. This experiment included appropriate controls for the occurrence of a spatial after-effect2,3, and so the data suggest that illusory effects persist after the conditions inducing them are removed.

AGGREGATION in planktonic organisms is often observed, both in the sea and in fresh water, and several explanations have been put forward to account for it. Uneven light intensity can often lead to aggregation; but other reasons must be put forward to account for swarms under uniform illumination. Some authors consider the animal's own behaviour to be responsible for swarming; thus social behaviour has been invoked in Cladocera1, chemosensitivity in Hemimysis2 and visual orientation to explain Mysid shoaling3. Other authors regard physical processes as being largely or entirely responsible, such as wind-generated turbulence4, retention in convection cells5 or in a weak convergence, aided by photopositive swimming6.

AT least some, and perhaps most, pinnipeds of the families Phocidae and Otariidae are nocturnal feeders1. The eyes of these predators, being sensitive to very low light intensities2, are suited for use at night and in deep water. During the day the visual acuity of the California sea lion (Zalophus californianus) allows this animal to discriminate a size difference ratio as small as 1.06 : 1 (ref. 3). A great deal of vocalizing occurs among pinnipeds, both above and below the surface of the water1,4–6. This fact, along with experimental work such as that of Mohl with the harbour seal (Phoca vitulina)7, indicates that hearing is generally well developed. Poulter suggested that the California sea lion, and probably other species, is able to capture prey in darkness by utilizing an echo-ranging sense similar to that known to occur among cetaceans4. However, subsequent work5,6 has failed to support Poulter's theory. Nevertheless, as “individuals totally blind but in a good state of health have been reported”1, the possibility that such a sense may bo developed when needed should not be dismissed lightly.

Visual orientation judgments were made during right head tilt, left body tilt, and left trunk tilt, each of 30 deg. In these postures the otolith, neck, and trunk systems are stimulated in pairs. The hypothesis that the visual vertical during trunk tilt is equal to the algebraic sum ofthose in the same direction ofbody tilt and the opposite head tilt was tested and accepted. This result demonstrates the interaction of these postural systems in visual orientation, and complements the confirmation of the same hypothesis for the visual aftereffect following prolonged tilt.

Recent advances in neonatology have enabled an increasing number of small premature infants to survive. While research on the physiological aspects of prematurity has been abundant, little is known about the early developmental course of these infants. This study examines the development of visual orientation in premature infants and has important theoretical and clinical implications. All infants were assessed using visual items from the Brazelton Scale. In the first 3 groups were 36 AGA, premature infants, breathing room air by 32 weeks gestation. Group 1 was assessed at weekly intervals from 32 to 37 weeks and at 40 weeks. Groups 2 and 3 served as controls for repeated testing. In Group 4 were 12 full-term infants tested at 2 days. Visual orientation increased steadily from 32 to 40 weeks. At 40 weeks, Group 1 was no different in visual behavior from Group 4. However, infants tested less frequently (Groups 2 and 3) performed less well than Groups 1 or 4. Theoretically these results support that view that visual development is gradual but can be affected by experience. Clinically, intervention strategies to enhance visual orientation are recommended in light of previous studies demonstrating the effects of visual behavior on mother-infant interaction.

Data from the NINDS Collaborative Study and others suggests that infants of diabetic mothers do more poorly than matched controls in specific development tests at age 4 years. This study assesses the behavior of these newborns of diabetic mothers (NDM's) in order to understand the genesis of these later problems and to design appropriate interventions. Ten full-term NDM's delivered by elective Caesarian section were compared to ten healthy full-term newborns delivered by elective Caesarian section on the Brazelton Neonatal Behavioral Assessment scale administered on days 3 and 5. All NDM's were free of all anomalies, metabolic and respiratory problems and considered healthy by their pediatricians by day 3. Brazelton scale data were analyzed with an a priori established cluster and profile scheme. The NDM's did significantly more poorly than the control newborns in physiological responses to stress and on interactive processes (Repeated measures ANOVA, p≥0.05, p≥0.001). In particular, the NDM's were more tremulous, had more startles and showed more color changes with handling even though they were normoglycemic and normocalcemic. Furthermore, NDM's behaved differently than controls on those behaviors considered important elicitors of caregiving by parents: attractiveness, need for and use of stimulation, visual orientation, sustaining periods of alertness and molding to the examiner's body during cuddling. It is speculated that the behavioral difficulties demonstrated in these newborns may influence early interaction with caregivers, make bonding more difficult and set the stage for later problems.