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The aim of this study was to describe the spectral features of pre-stimulus event-related potential (ERP) components elicited in visual tasks such as the Bereitschaftspotential (BP), prefrontal negativity (pN) and visual negativity (vN). ERPs are considered time-locked and phase-locked (evoked) activity, but we have also analyzed the non-phase but time-locked (induced) activity in the same interval by applying the temporal spectral evolution (TSE) method. Participants (N = 26) were tested in a passive task, a simple response task (SRT) and a discriminative response task (DRT), where EEG activity was recorded with 64 scalp electrodes. We analyzed the time-frequency modulations (phase and non-phase) prior to the onset of the stimuli in the sub-delta, delta, theta, alpha, beta, and gamma frequency bands. The results showed that all the pre-stimulus ERP components were mainly regulated by evoked activity in the sub-delta band. On the other hand, induced activity seems to be linked to evoked responses but with a different psychophysiological role. We concluded that other preparatory cognitive mechanisms associated with ERPs can also be detected by the TSE method. This finding may suggest underlying mechanisms in non-phase activity and requires the addition of non-phase activity analysis to the traditional analysis (phase and evoked activity).

The giant mottled eel Anguilla marmorata Quoy & Gaimard is an important aquaculture candidate in eel farming industry. The high economic value of the species leads to intensive cultivation affecting its welfare under farm condition. Since colour environment affects the welfare of confined fishes, basic information on colour vision is necessary. By means of a behavioural experiment of A. marmorata elvers in the laboratory, we determined colour vision under natural daylight. The elvers were subjected to classical conditioning to associate a reward feed with a blue or a green stimulus placed amid seven shades of grey. The elvers learned this visual task after 30 or 36 trials and thus the ability of colour discrimination was confirmed. Since the elvers have the retinal tapetum, it may be suggested that colour vision in dim light enables crepuscular feeding by the A. marmorata elvers, clearly an advantage in aquaculture.

The purpose of this study was to investigate the effects of sport participation, concussion history, and age of first exposure to football on preseason cerebrovascular function in adolescent athletes. Athletes (n = 53, age = 15.8 ± 1.2 years) were examined based on three exposure groupings: (1) sport participation (football vs. non-collision), (2) concussion history (none vs. ≥ 1), and (3) age of first exposure (football participants only). Transcranial Doppler assessed cerebrovascular reactivity (CVR) and neurovascular coupling (NVC), and separate independent samples t-tests evaluated group differences in CVR and NVC outcomes. Separate univariate linear regressions determined how age of first exposure related to CVR and NVC outcomes. Linear mixed effects models assessed group differences in CVR and NVC relative response curves. Differential response to NVC visual task response was significantly greater in non-collision sport athletes (F1,2946 = 38.69, p < 0.0001) and athletes without a concussion history (F1,2946 = 25.23, p < 0.0001). Older age of first exposure significantly predicted reduced breath-holding CVR response (F1,1560 = 2.92, p = 0.03). Healthy adolescent athletes have similar pre-season cerebrovascular function despite different sport participation and concussion history. However, age of first exposure may predict CVR in adolescent football athletes. Developmental literature identifies cerebrovascular function as dynamically changing throughout adolescence. Our study provides fundamental data informing the clinical meaningfulness of short- and long-term physiological function changes.

The anatomy of the mammalian visual system, from the retina to the neocortex, is organized hierarchically1. However, direct observation of cellular-level functional interactions across this hierarchy is lacking due to the challenge of simultaneously recording activity across numerous regions. Here we describe a large, open dataset-part of the Allen Brain Observatory2-that surveys spiking from tens of thousands of units in six cortical and two thalamic regions in the brains of mice responding to a battery of visual stimuli. Using cross-correlation analysis, we reveal that the organization of inter-area functional connectivity during visual stimulation mirrors the anatomical hierarchy from the Allen Mouse Brain Connectivity Atlas3. We find that four classical hierarchical measures-response latency, receptive-field size, phase-locking to drifting gratings and response decay timescale-are all correlated with the hierarchy. Moreover, recordings obtained during a visual task reveal that the correlation between neural activity and behavioural choice also increases along the hierarchy. Our study provides a foundation for understanding coding and signal propagation across hierarchically organized cortical and thalamic visual areas.

Sleep is beneficial for learning. However, it remains unclear whether learning is facilitated by non-rapid eye movement (NREM) sleep or by REM sleep, whether it results from plasticity increases or stabilization, and whether facilitation results from learning-specific processing. Here, we trained volunteers on a visual task and measured the excitatory and inhibitory (E/I) balance in early visual areas during subsequent sleep as an index of plasticity. The E/I balance increased during NREM sleep irrespective of whether pre-sleep learning occurred, but it was associated with post-sleep performance gains relative to pre-sleep performance. In contrast, the E/I balance decreased during REM sleep but only after pre-sleep training, and the decrease was associated with stabilization of pre-sleep learning. These findings indicate that NREM sleep promotes plasticity, leading to performance gains independent of learning, while REM sleep decreases plasticity to stabilize learning in a learning-specific manner.

Very preterm (VPT

When two overlapping tasks are processed, they hit a bottleneck at a central processing stage that prevents simultaneous processing of the two tasks. Thus far, however, the factors determining the processing order of the tasks at the bottleneck are unknown. The present study was designed to (re)investigate whether the arrival times of the two tasks at the central bottleneck are a key determinant of the processing order (cf. Sigman & Dehaene, 2006). To this end, we implemented a visual-auditory dual task with a random stimulus order, in which we manipulated arrival time by prolonging the initial, perceptual processing stage (stimulus analysis) of the visual task and compared the effects of this manipulation with those of one impacting the central bottleneck stage of the visual task. Additionally, we implemented two instruction conditions: Participants were told to respond either in the order of stimulus presentation or in the order they preferred. The manipulation of the visual perception stage led to an increase in task response reversals (i.e., the response order was different from the order of stimulus presentation), whereas there was no such increase when the bottleneck stage was manipulated. This pattern provides conclusive evidence that the processing order at the bottleneck is (at least in part) determined by the arrival times of the tasks at that point. Reaction time differences between the two instruction conditions indicated that additional control processes are engaged in determining task processing order when the participants are expressly told to respond in the order of stimulus presentation.

A hierarchical and modular organization is a central hypothesis in the current primate model of auditory cortex (AC) but lacks validation in humans. Here we investigated whether fMRI connectivity at rest and during active tasks is informative of the functional organization of human AC. Identical pitch-varying sounds were presented during a visual discrimination (i.e. no directed auditory attention), pitch discrimination, and two versions of pitch n-back memory tasks. Analysis based on fMRI connectivity at rest revealed a network structure consisting of six modules in supratemporal plane (STP), temporal lobe, and inferior parietal lobule (IPL) in both hemispheres. In line with the primate model, in which higher-order regions have more longer-range connections than primary regions, areas encircling the STP module showed the highest inter-modular connectivity. Multivariate pattern analysis indicated significant connectivity differences between the visual task and rest (driven by the presentation of sounds during the visual task), between auditory and visual tasks, and between pitch discrimination and pitch n-back tasks. Further analyses showed that these differences were particularly due to connectivity modulations between the STP and IPL modules. While the results are generally in line with the primate model, they highlight the important role of human IPL during the processing of both task-irrelevant and task-relevant auditory information. Importantly, the present study shows that fMRI connectivity at rest, during presentation of sounds, and during active listening provides novel information about the functional organization of human AC.

Physical exercise and the training effects of repeated practice of skills over an extended period of time may have additive effects on brain networks and functions. Various motor skills and attentional styles can be developed by athletes engaged in different sports. In this study, the effects of fast ball sports and dance training on attention were investigated by event related potentials (ERP). ERP were recorded in auditory and visual tasks in professional dancer, professional fast ball sports athlete (FBSA) and healthy control volunteer groups consisting of twelve subjects each. In the auditory task both dancer and FBSA groups have faster N200 (N2) and P300 (P3) latencies than the controls. In the visual task FBSA have faster latencies of P3 than the dancers and controls. They also have higher P100 (P1) amplitudes to non-target stimuli than the dancers and controls. On the other hand, dancers have faster latencies of P1 and higher N100 (N1) amplitude to non-target stimuli and they also have higher P3 amplitudes than the FBSA and controls. Overall exercise has positive effects on cognitive processing speed as reflected on the faster auditory N2 and P3 latencies. However, FBSA and dancers differed on attentional styles in the visual task. Dancers displayed predominantly endogenous/top down features reflected by increased N1 and P3 amplitudes, decreased P1 amplitude and shorter P1 latency. On the other hand, FBSA showed predominantly exogenous/bottom up processes revealed by increased P1 amplitude. The controls were in between the two groups. WOS:000427611200005 29564028 Q2

Many demersal fish species undergo vertical shifts in habitats during ontogeny especially after larval metamorphosis. The visual spectral sensitivity shifts with the habitat, indicating a change in colour vision. Colour vision depends on sufficient ambient light and becomes ineffective at a particular low light intensity. It is not known how fishes see colour in dim light. By means of a behavioural experiment on larval African catfish Clarias gariepinus in the laboratory, we determined colour vision and colour discrimination in dim light. Light-adapted larvae were subjected to classical conditioning to associate a reward feed with a green or a red stimulus placed among 7 shades of grey. The larvae learned this visual task after 70 and 90 trials. A different batch of larvae were trained to discriminate between green and red and then tested for the ability to discriminate between these colours, as the light intensity was reduced. The larvae learned this visual task after 110 trials in bright light and were able to discriminate colours, as light was dimmed until 0.01 lx, the minimal illuminance measurable in this study, and similar to starlight. The retinae of the larvae were found to be light adapted at 0.01 lx; thus indicating cone-based colour vision at this illuminance. For comparison, three human subjects were tested under similar conditions and showed a colour vision threshold at between 1.5 and 0.1 lx. For the larvae of C. gariepinus, the ability of colour discrimination in dim light is probably due to its retinal tapetum, which could increase the sensitivity of cones.

The current study examines the EEG coherence of young, old, and old declined adults performing a visual paired-associates task. In order to examine the effects of encoding context and stimulus repetition, target pairs were presented on either detailed or white backgrounds and were repeatedly presented during both early and late phases of encoding. Younger adults were found to have lower levels of frontal-temporal and temporal-parietal coherence, but higher levels of frontal-parietal coherence, particularly for the gamma frequency band. A number of differential coherence responses to background context and early- versus late-encoding phases were also observed across the groups, particularly for lower alpha and upper alpha frequencies. Coherence-performance maps were generated to further explore topographical differences in the relationship between coherence and performance across groups. Results revealed a more diffuse pattern of negative coherence-performance relations in older declined adults. Results are discussed in light of the literature on age-related cognitive decline.

Visual processing of basic perceptual attributes depends on attention. This has been well documented since the surprising initial report on attentional modulation of the visual motion aftereffect (Chaudhuri 1990). Here, we investigate proprioception and show for the first time that attention modulates adaptation to perceived limb movement. We used biceps vibration to induce illusory forearm extension in 10 participants and measured the aftereffect-perceived movement in the opposite direction. The aftereffect was largest when participants focused on the illusory extension during the adaptation period. To divert attention away from the illusory extension, a rapid serial visual presentation task was performed during the adaptation. The aftereffect was much smaller in this condition, indicating interference between the visual task and proprioceptive adaptation. In tests of an analogous interaction between audition and vision, earlier research found no effect. We suggest that conscious proprioception requires more attention than conscious processing of visual or auditory input.

Motor adaptation is impaired by the performance of a secondary task which divides cognitive resources. Additionally, we previously reported slowed adaptation when participants were required to switch from one visual displacement adaptation task to another. Here, we examined whether a dividing secondary task had a similar effect on adaptation as switching between opposing visual displacements. The resource-dividing task involved simultaneously adapting to a step-visual displacement whilst vocally shadowing an auditory stimulus. The switching task required participants to adapt to opposing visual displacements in an alternating manner with the left and right hands. We found that both manipulations had a detrimental effect on adaptation rate. We then integrated these tasks and found the combination caused a greater decrease in adaptation rate than either manipulation in isolation. A second set of experiments showed that adaptation to a gradually imposed visual displacement was influenced in a similar manner to step adaptation. In summary, step adaptation slows the learning rate of gradual adaptation to a large degree, whereas gradual adaptation only slightly slows the learning rate of step adaptation. Therefore, although gradual adaptation involves minimal awareness it can still be disrupted with a cognitively demanding secondary task. We propose that awareness and cognitive resource can be regarded as qualitatively different, but that awareness may be a marker of the amount of resource required. For example, large errors are both noticed and require substantial cognitive resource. However, a lack of awareness does not mean an adaptation task will be resistant to interference from a resource-consuming secondary task.

The influence of a secondary task on speeded responses, and its effect on the outcome of more complex tasks has been studied in detail. However, the consequence of task interference on specific movement parameters other than speed and accuracy has been largely ignored. The current study examines how performing a secondary task impacts the drawing of an unseen shape. Without vision of the hand, 15 subjects traced a shape on a graphics tablet. The shape and cursor were projected onto a screen. The shape disappeared and the subject attempted to draw three consecutive identical shapes. In the visual single-task condition, hand positions were represented by a cursor, but the resultant drawings could not be seen; in another, there was no visual feedback. In four remaining conditions, the 15 subjects drew the previously seen shapes without visual feedback while performing a secondary task of reporting the orientation of an arrow which appeared on the screen either in random or periodic timing. Subjects indicated the direction of the arrow either verbally or manually. Shapes were analyzed for scale, error of the corner angles as compared with 90 degrees, and drift, compared to the reference shape and across conditions. In dual-task conditions, performance of the primary, shape-drawing task deteriorated with respect to location and orientation, but not with respect to the pattern and proportion aspects of the shape. Vision was important for controlling position of the drawing, and also for controlling the shape and proportion of the drawing suggesting separate mechanisms for the location of a drawing and its shape and proportion. Furthermore, we propose that internal representations are more important than proprioception in the shape aspect of drawing well-known figures.

Previous work from our laboratory indicates that interhemispheric interaction (IHI) functionally increases the attentional capacity available to support performance on visual tasks (Banich in The asymmetrical brain, pp 261-302, 2003). Because manipulations of both computational complexity and selection demand alter the benefits of IHI to task performance, we argue that IHI may be a general strategy for meeting increases in attentional demand. Other researchers, however, have suggested that the apparent benefits of IHI to attentional capacity are an epiphenomenon of the organization of the visual system (Fecteau and Enns in Neuropsychologia 43:1412-1428, 2005; Marsolek et al. in Neuropsychologia 40:1983-1999, 2002). In the current experiment, we investigate whether IHI increases attentional capacity outside the visual system by manipulating the selection demands of an auditory temporal pattern-matching task. We find that IHI expands attentional capacity in the auditory system. This suggests that the benefits of requiring IHI derive from a functional increase in attentional capacity rather than the organization of a specific sensory modality.

The remote distractor effect is a robust finding whereby a saccade to a lateralised visual target is delayed by the simultaneous, or near simultaneous, onset of a distractor in the opposite hemifield. Saccadic inhibition is a more recently discovered phenomenon whereby a transient change to the scene during a visual task induces a depression in saccadic frequency beginning within 70 ms, and maximal around 90-100 ms. We assessed whether saccadic inhibition is responsible for the increase in saccadic latency induced by remote distractors. Participants performed a simple saccadic task in which the delay between target and distractor was varied between 0, 25, 50, 100 and 150 ms. Examination of the distributions of saccadic latencies showed that each distractor produced a discrete dip in saccadic frequency, time-locked to distractor onset, conforming closely to the character of saccadic inhibition. We conclude that saccadic inhibition underlies the remote distractor effect.

To successfully lift an object, a person's fingers must be moved to locations where forces can be applied that are sufficient for maintaining contact and that allow for easy object manipulation. Obtaining such finger positions becomes more difficult when there is perceptual uncer- tainty about the location of the hand and object. However, knowledge about the amount of uncertainty could be incorporated into grasp plans to mitigate its effect. For example, during peripheral viewing the fingers could open wider to avoid colliding with or missing the object. The goal of this study is to determine the degree to which people incorporate their understanding of visual uncer- tainty when making a precision grasp. To investigate, subjects reached to a spatially fixed object whose retinal location was varied by fixating points 0-80� to the left of the object. This manipulation controlled the visual uncer- tainty of the hand and target without affecting the kine- matic demands of the task. We found that people systematically changed their grasping behavior as a func- tion of the amount of visual uncertainty in the task. Spe- cifically, subjects' maximum grip aperture increased linearly with target eccentricity. Moreover, the effect of visual uncertainty on finger trajectories could be captured by a single dimension of change along an axis. Together, these findings suggest that the sensorimotor system esti- mates visual uncertainty and behaviorally adjusts for it during grasping movements.

Rapid reaching movements of human and non-human primates are often characterized by irregular multi-peaked velocity profiles. How to interpret these irregularities is still under debate. While some reports assert that these irregularities are the result of a continuous controller interacting with the environment, we and others hold that the velocity irregularities are evidence for a controller that produces discrete movement corrections. Here we analyze rapid pronation/supination wrist movements in monkey during a 1D step-tracking task, where visual perturbations of the target were randomly introduced at movement onset. We use our recently introduced algorithm (Fishbach et al. in Exp Brain Res 164:442-457, 2005) to decompose an irregular movement into a primary movement and one or more discrete, corrective submovements. We first show that the visual perturbation has almost no effect on primary movements. In contrast, this perturbation influences the type and the extent of the corrective submovements that often follow primary movements. Secondly, we show that the highly variable timing of overlapping submovements does not depend directly on the visual perturbation but rather on an estimate of the movement error and on the movement's extent-to-go at the time of correction initiation. These results are consistent with a forward-model based intermittent controller with a non-linearity that depends both on a prediction of the magnitude and direction of the movement's error and on its variance. Corrections are initiated only when the predicted error is statistically significant. A simple abstract model that implements these principles accounts for the type and timing of the corrections observed in our data.

Tipper (1985; Q J Exp Psychol A 37:571-590) has suggested that competing responses programmed to distracting stimuli are inhibited based on their relationship to the action being performed. The present paper reports two experiments designed to examine the influence of the terminal action of a task on the allocation of visual attention. Taken together the results suggest that when engaging targets in an environment, which includes distracting stimuli, competing responses are likely to be programmed in parallel and that the relationship between competing responses can include both spatial position and action characteristics.

The human visual system analyzes shapes and objects in a series of stages in which stimulus features of increasing complexity are extracted and analyzed. The first stages use simple local features, and the image is subsequently represented in terms of larger and more complex features. These include features of intermediate complexity and partial object views. The nature and use of these higher-order representations remains an open question in the study of visual processing by the primate cortex. Here we show that intermediate complexity (IC) features are optimal for the basic visual task of classification. Moderately complex features are more informative for classification than very simple or very complex ones, and so they emerge naturally by the simple coding principle of information maximization with respect to a class of images. Our findings suggest a specific role for IC features in visual processing and a principle for their extraction.

We investigated how sensorimotor adaptation acquired during one experimental session influenced the adaptation in a subsequent session. The subjects' task was to track a visual target using a joystick-controlled cursor, while the relationship between joystick and cursor position was manipulated to introduce a sensorimotor discordance. Each subject participated in two sessions, separated by a pause of 2 min to 1 month duration. We found that adaptation was achieved within minutes, and persisted in the memory for at least a month, with only a small decay (experiment A). When the discordances administered in the two sessions were in mutual conflict, we found evidence for task interference (experiment B). However, when the discordances were independent, we found facilitation rather than interference (experiment C); the latter finding could not be explained by the use of an "easier" discordance in the second session (experiment D). We conclude that interference is due to an incompatibility between task requirements, and not to a competition of tasks for short-term memory. We further conclude that the ability to adapt to a sensorimotor discordance can be improved by practicing with an unrelated discordance.

This experiment examined the whole-partial effect of overtraining in concurrent discriminations using two different sensory modality tasks (tactual and visual task) and assessed the effect against single discrimination training in rats. Overtraining facilitated reversals in both Group W, in which rats were given concurrent training on two tasks in the original learning before both tasks were reversed, and Group S, in which rats were trained only on the tactual task before it was reversed. Overtraining retarded reversal in Group P, in which rats were given the same training as in Group W in original learning, but only the tactual task was reversed. After overtraining, Groups Wand S reversed more rapidly than Group P. After criterion training, Group P reversed more rapidly than Group W, which reversed more rapidly than Group S. These findings indicate that rats form stimulus classes (i.e., cross-modal stimulus classes) between the discriminative stimuli of two different sensory modalities with the same response assignment during overtraining in two concurrent discriminations as well as between the discriminative stimuli of the same sensory modality.

An ability of primates to compare and identify planar images and three-dimensional objects has been studied at solving tasks of the “choice on model” type. The study is carried out on three species of monkeys of different levels of phylogenetic development: macaques rhesuses Macaca mulata, brown capuchins Cebus apella, and chimpanzee Pan troglodytes. Plaster casts of fruits, household objects, and toys–animals were used for the identification. It is revealed that representatives of the studied monkey species are able to compare and identify three-dimensional objects and their two-dimensional images and to extract identical attributes during solution of visual tasks of different degrees of complexity in variants of the methodical approach “choice on model.” Under conditions of our experiments, the capuchins, macaques, and chimpanzee performed a direct transfer of the elaborated principle of the solution. There have also been established peculiarities of behavior of different species of the lower and higher monkeys. Macaques rhesuses had difficulties when solving complex combinatory tasks. Capuchins displayed pronounced negative emotions and characteristic patterns of defensive behavior at demonstration and during identification of two- and three-dimensional objects of the toys–animals type. Unlike the lower monkeys, the chimpanzee, when presented with toys–animals, did not change the level of their correct answers and demonstrated pronounced play reactions.

The visual evoked potentials (EPs) in response to lateralized and central visual symbols under the conditions of involuntary (passive viewing) and selective attention (when one of the symbols was a target and required a rapid and precise motor reaction) are considered. The evoked potentials in the occipital, parietal, and frontal derivations were recorded in 20 healthy subjects. It was shown that the EP during selective attention are most pronounced and more alike in the parietal derivations. A strong positive correlation was revealed between the EP amplitude ([N1–P3] component) and the EP stability (correlation between the repeated EP). The involuntary and voluntary forms of attention supplement each other: the more expressed the involuntary attention (assessed by the [N1–P3] component) the higher the EP to target stimuli during voluntary attention and the shorter the reaction time. It is suggested that the role of visual attention consists in the increase and stabilization of cortical activity (primarily, the parietal regions) engaged in solving a visual task.

We have studied the effect of rest breaks on sensorimotor adaptation to rotated visual feedback in a pointing task. Adaptive improvement was significantly poorer after 1-s breaks than after 5–40-s breaks, with no significant difference among the latter break durations. The benefit of >1-s breaks emerged soon after the onset of adaptation, and then remained steady throughout the adaptation, retention (next day), and persistence (no feedback) phases. This pattern of findings indicates that break-induced facilitation is not a result of strategic adjustments, motivation, or recovery from fatigue, but rather to consolidation of previously acquired sensorimotor recalibration rules.

In two separate experiments, P300 was recorded from overnight-abstaining smokers before and after smoking. In the first experiment, 32 subjects counted forward by ones and counted backwards by threes upon presentation of a rare tone burst (20%) in a stream of standard tones. There were no changes in P300 amplitude or latency pre- to post-smoking (1.1-mg FTC nicotine-yield cigarette). In the second experiment, 29 subjects completed auditory and visual oddball tasks before smoking, after smoking a low nicotine-yield cigarette (0.05 mg), after smoking a higher nicotine-yield cigarette (1.1-mg), and after smoking a second 1.1-mg cigarette. In the visual oddball task, P300 latency decreased after smoking the first higher-yield cigarette relative to both pre-smoking and post smoking the lower-yield cigarette. This effect was maintained after smoking the second higher-yield cigarette. In the visual task, P300 amplitude increased after smoking the first higher-yield cigarette (from a lower baseline level) in a group of subjects with larger changes in tidal-breath CO but not in a group with smaller changes in CO. There were no effects of smoking on P300 amplitude or latency in the auditory tasks of either the first or second experiment.

Past research and theory presents an inconsistent picture concerning the relative value of verbal versus visual instructional programs for individuals with mental retardation. From an empirical perspective, there is evidence that this inconsistency may be due to the differences in the type of tasks and the specific abilities of the subjects employed across studies. In this research, the effects of three instructional procedures (verbal, visual, and verbal plus visual) were evaluated with mentally retarded persons who varied in verbal and visual ability. Performance was examined on a visual task which incorporated stimuli of varying degrees of familiarity to the subjects. The results indicated that the use of the combined verbal-visual instruction procedure was more effective than the other two training programs when task stimuli were familiar to the subjects. When task stimuli were unfamiliar, instructional procedures which had a visual component were found to be superior to a procedure which employed only the use of verbal component. The subjects' visual ability was most strongly associated with performance outcome when visual instruction was employed and unfamiliar task stimuli were sorted. In contrast, subjects' verbal ability appeared to be equally important across instructional and task conditions. The implications of the results for the design of instructional programs and for future research are discussed.

In four experiments, we tested whether perceptual identification is impeded by temporal overlap with another task. The results demonstrate that temporal overlap with an auditory task consistently impaired the identification of the highest digit in a briefly presented and masked array of digits. The impairment was especially pronounced when we emphasized speed on the auditory task, thus counteracting the normal tendency to focus advance preparation on the more challenging visual task. The data also indicate that previous findings of minimal effects of temporal overlap may have been due to the use of a restricted range of stimulus onset asynchronies. The present results demonstrate the important role of preparatory strategies in overlapping-task performance, and show that perceptual identification is impeded by the overlapping performance of another task.

Background Children are able to inhibit a prepotent reaction to suddenly arising visual stimuli, although this skill is not yet as pronounced as it is in adulthood. However, up to now the inhibition mechanism to acoustic stimuli has been scarcely investigated Methods Reflexive (prosaccade) and inhibitory (antisaccade) responses to visual and acoustic targets were examined with an eye tracker system in 31 children between seven and twelve years of age using a gap-overlap task and two target eccentricities. Results Acoustically cued saccades had longer reaction times than visually cued saccades. A gap effect (i.e., shorter reaction time in the gap than the overlap condition) was only found for visually elicited saccades, whereas an eccentricity effect (i.e., faster saccades to more laterally presented targets - 12° vs. 6° or rather 90° vs. 45°) was only present in the acoustic condition. Longer reaction times of antisaccades compared to prosaccades were found only in the visual task. Across both tasks the typical pattern of elevated error rates in the antisaccade condition was found. Antisaccade errors declined with age, indicating an ongoing development of inhibitory functions. Conclusions The present results lay the ground for further studies of acoustically triggered saccades in typically as well as atypically developing children and it might thus be possible to upgrade physiological diagnostic tools.

Perceptual organization is thought to involve an analysis of both textural discontinuities and perceptual grouping. In earlier work, we found that textural discontinuities were detected nor­ mally even when visual attention was engaged elsewhere. Here we report how perceptual group­ ing is affected when visual attention is engaged by a concurrent visual task. To elicit perceptual grouping, we used the Gestalt demonstrations of grouping on the basis of proximity and of simi­ larity. Four tasks were investigated, some requiring the observer to discriminate between hori­ zontal and vertical grouping, and some requiring the observer to merely detect the presence or absence of grouping. Visual attention was engaged at the center of the display by a form identifi­ cation task. The detection of a textural discontinuity served as a control task. Concurrent form identification conflicted with all four grouping tasks, resulting in a significant reduction of group­ ing performance in each case. No performance reduction was observed when either form identifi­ cation or grouping discrimination was combined with the detection of a textural discontinuity. These results suggest that perceptual grouping and form identification compete for visual atten­ tion, whereas the detection of a textural discontinuity does not.

The perception of natural visual scenes that contain many objects poses computational problems that are absent when objects are perceived in isolation1. Vision researchers have captured this attribute of real-world perception in the laboratory by using visual search tasks, in which subjects search for a target object in arrays containing varying numbers of non-target distractor objects. Under many conditions, the amount of time required to detect a visual search target increases as the number of objects in the stimulus array increases, and some investigators have proposed that this reflects the serial application of attention to the individual objects in the array2,3. However, other investigators have argued that this pattern of results may instead be due to limitations in the processing capacity of a parallel processing system that identifies multiple objects concurrently4,5. Here we attempt to address this longstanding controversy by using an electrophysiological marker of the moment-by-moment direction of attention — the N2pc component of the event-related potential waveform — to show that attention shifts rapidly among objects during visual search.

The effects of alcohol and extended practice on divided attention were investigated using a visual tracking task and an auditory detection task. Subjects performed the tasks with and without alcohol, under single-task (S) and dual-task (D) conditions, both before and after they had received extended practice under single-task conditions without alcohol. Tracking accuracy improved with practice and was impaired under divided-attention conditions but was not affected by alcohol. Speed of detection was impaired by alcohol, improved by practice, and impaired by divided attention. Extended practice did not reduce the influence of alcohol. The effects of both alcohol and practice on speed of detection were significantly greater under dual-task conditions than under single-task conditions. Analysis of detection-task reaction times in terms of relative divided-attention costs, (D-S)/S, showed no effect of alcohol, but a highly significant reduction in costs with extended practice. It is concluded that (1) alcohol and practice can have quantitatively, but not qualitatively, similar effects on speeded performance, and (2) the effect of alcohol is not influenced by the attentional requirements of the task.

WE describe here a new view of primary visual cortex (VI) based on measurements of neural responses in V1 to patterns called ‘illusory contours’ (Fig. la, b). Detection of an object's boundary contours is a fundamental visual task. Boundary contours are defined by discontinuities not only in luminance and colour, but also in texture1–3, disparity4 and motion5–7. Two theoretical approaches can account for illusory contour perception. The cognitive approach emphasizes top-down processes8,9. An alternative emphasizes bottom-up processing. This latter view is supported by (1) stimulus constraints for illusory contour perception10–14 and (2) the discovery by von der Heydt and Peterhans15–17 of neurons in extrastriate visual area V2 (but not in V1) of macaque monkeys that respond to illusory contours. Using stimuli different from those used previously15,16, we found illusory contour responses in about half the neurons studied in V1 of macaque monkeys. Therefore, there are neurons as early as V1 with the computational power to detect illusory contours and to help distinguish figure from ground.

Previous research (Flowers & Lohr, 1985) has not found evidence for the “popout” phenomenon (e.g., Treisman, 1988) with word and nonword letter strings. Flowers and Lohr utilized a visual search task that employed a circular arrangement of stimuli. This format does not optimize spatial contiguity, which has been shown to facilitate stimulus detection in certain contexts (Bryant & Soraci, 1992; Soraci, Carlin, Deckner, & Baumeister, 1990). The present study examined popout with words and nonwords in a same-different task, using a visual array format in which interstimulus contiguity increased with changes in set size. With these arrays, no popout effect was evidenced under conditions of high featural overlap between targets and distractors. However, under conditions of low featural overlap, a popout effect for both words and nonwords was found.

1. Poecilobothrns nobilitatus has a spectacular courtship in which the males perform a complex aerial display directed towards the females. This begins with short bouts of wing-waving, after which the male hovers in front of the female. This is followed by two types of display flight. In one the male circles in an arc around one side of the female, and in the second he flies over her, rotating through 180° in 40ms. The display flights are not modified once they have begun, and are thus pre-coordinated rather than feedback driven, as in tracking behaviour. 2. Courtship behaviour is confined to the males, and the extra tasks the male nervous system is required to perform are discussed in terms of the information needed for the execution of the behaviour.

A prominent part in the development of the theory of visuo-spatial working memory has been played by techniques such as the Corsi Blocks task. A study on a wide variety of WM tasks using a patient group, bipolar patients in the euthymic stage, indicates that the group is relatively disadvantaged on the Corsi Blocks task. However, patients are also disadvantaged on tasks involving executive processes while visual task processes are spared. A number of regression analyses clearly indicates that the Corsi task disadvantage can be explained by the executive deficit and suggest that tasks that purportedly index spatial processes may be better considered to be dependent on the executive processes. Implications for the development of visuo-spatial working memory theory are discussed.

An experiment concerning recognition memory for shapes investigated the consequences of manipulating the component operations of domain of processing, that is, encoding strategy, processing time, and stimulus compatibility. It is established that semantic encoding and long processing time facilitated recognition performance for low-, but not for high-, compatibility shapes. A visual task interfered with recognition memory for low-compatibility shapes. Several theoretical contributions to the domain-of-processing framework, which follow from the findings of this experiment, are presented and discussed.

Rats with lesions of the occipital pole or a more anterior extrastriate area were tested on either original learning of a successive brightness discrimination or retention of this task after acquisition as a normal. Equivalent original learning losses relative to normals were sustained from both lesions, but while extrastriates showed substantial savings in retention, rats with occipital pole damage required as many relearning trials as were necessary for original learning by brain-damaged groups. It was suggested that the effect of the anterior extrastriate lesion was to impair a spatial or positional component of discrimination performance, and that this component might differ from one related to visual task properties, especially in terms of recovery of function following brain damage.

Effects of target size, eccentricity and background luminance were determined for static and acuity profile perimetry in the central 30° radius of the visual field. Reductions in target size produced decreases in sensitivity for both functions, with acuity profiles (resolution sensitivity) being more affected than static profiles (detection sensitivity). At photopic background luminances, detection sensitivity was greatest at the fovea and progressively declined with increasing eccentricity; lower background luminances produced greater detection sensitivity for the near periphery than for the fovea. Resolution sensitivity for small targets (20/80 or less) exhibited a rapid decline with increasing eccentricity that was relatively independent of background luminance, whereas large targets (20/125 or greater) revealed findings similar to the detection sensitivity results. The relative contributions of rods and cones to threshold visual responses thus appear to depend on the type of visual task, target size, eccentricity, background luminance and thek interactions. These data provide a comparison basis for future evaluations of patients with photoreceptor dysfunction.

This report describes experimental measurements of threshold contrasts as a function of the angle to the visual axis (peripheral threshold contrasts). The visual tasks consist in detection (perception of presence) and discrimination (perception of a form feature) of simple visual signs during a fixation period realistic observing conditions being chosen. Proceeding from the experimental findings a model for forecasting off-axis threshold contrast functions on different visual conditions is developed based upon spatial frequency filters. Further with the aid of a known model visibility fields are calculated.

Effects of physical effort have been difficult to find in attention tasks for various reasons, such as the activating effect of the laboratory situation or the spare capacity in automated tasks. Instead, a double task, reflecting quantitatively the changes of information processing, is proposed. Thirty minutes after a paced circuit training, a visual-auditory task was presented for 40 min: tachistoscopically presented dot patterns together with high and low tones. This was done at an easy pace, leaving it up to the subject to decide what to reproduce, as in normal circumstances. No effect was found in the total correct scores or in the auditory task. Deterioration was found only in the more difficult part of the visual task. The results can be explained in terms of Kahneman’s variable-allocation capacity model. This method seems promising for separating effects on different stages of information processing.

The effects of ambiguous instructions and instructions to specifically ignore or attend to stimuli on electrodermal habituation were examined in 88 volunteers who were evenly divided among four groups. The subjects were exposed to 17 105-dB tones. Subjects in three of the groups watched a videotape of an old silent movie. Those in the “Ignore” group were exhorted to immerse themselves in the movie and ignore the tones. “Attend” subjects were told to count the tones and be certain that they all sounded the same. In the two neutral groups, only one of which saw the movie, subjects were told simply that they would hear some tones. “Ignore” subjects responded less often, habituated at a faster rate, and rated the tones as less loud than did subjects in the other groups. The results confirmed our previous findings that ignore instructions coupled with a distracting task reduce electrodermal reactivity to loud task-irrelevant stimuli.

Usarmymedical Research Laboratory, Fort Knox, Kentucky This investigation examined the performance of 36 Ss on three 90-min vigilance tasks. As time on task increased, there was a significant decrease in number of detections and false responses and a corresponding significant increase in response latency. The consistent rank order relationship between stimulus conditions suggests that there were uniform trends among these conventional response measures. There was a significant decline in sensitivity (d′) lor the closely coupled tasks, regardless of the sense mode involved. However, d′ remained fairly stable for the loosely coupled visual task. The significant increase in criterion values(β) suggest that Ss adopt a more conservative mode of responding with increasing time on task. Further, these data indicate that a lack of control of coupling effects, rather than sense mode specificity, may have confounded the interpretation of prior research on visualand auditory tasks.

Visual and auditory classification of equivalent class structured patterns were examined. Underlying patterns from two classes were translated into auditory tone sequences and visual polygons. All Ss classified 50 visual patterns and their direct auditory analogs. Visual classification accuracy exceeded auditory accuracy (p < .01); however, auditory accuracy improved when auditory classification was preceded by the visual task (p < .01). Based on group data, classification strategies appeared similar across modalities, with accuracy of classification of individual patterns predicted to the same degree by common measures of physical class structure across modalities. Ss’ drawings of the prototypes also suggested a common strategy across modalities. While group data suggest some consistency of classification strategy across modalities, individual Ss were not at all consistent in their visual and auditory classifications.

A lie scale was administered to college students. Three groups were formed according to the degree to which they responded truthfully to the statements. The subjects were then individually run in a visual perception task with dissyllables being presented for short time durations. Two response measures were taken: the latency of the first verbal response and the number of incorrect intrusions made during the experiment. The results showed that the liars responded with shorter latencies and made more intrusions than either of the other groups. There were no differences between the truthtellers and the medium group.

Using incompletely filled grids, Ss retained simultaneously both the position and identity of items for 10-sec periods which were filled with one of three different kinds of interpolated activity. Interpolated activity consisted of (1) no activity, (2) a verbal task involving addition of orally presented digits, or (3) a visual task involving discrimination between dot patterns. Percentage loss data demonstrated that the visual and verbal interpolated conditions were selective in affecting type of information loss, thus suggesting that position and identity information are stored, or at least lost, independently. The fact that the selective effect of information lost as a result of the visual and verbal interpolated task was much greater for position information than for identity information suggests a two-modality STM code. Presumably, position information is mediated by a structural or visual code and identity information is mediated by the same structural code as well as an acoustic code.

The refractive state of the eye can be accurately determined while performing a visual task by introducing the diverged beam of a laser, reflected from a moving drum, into the visual field. The direction of the apparent motion of the resultant interference pattern is a direct indicator of refractive state. By incorporation of the Badal principle into the optical system, a measurement can be completed within approximately 30 sec. The advantage of this method over other techniques is that it permits evaluation of refractive state but does not itself influehce the magnitude of accommodation. A number of applications of this principle are cited.

Experiments with feedback regulation of normal subjects' parietal-occipital alpha electroencephalographic asymmetry have shown that subjects learned to optimize the conditions under which symmetry and asymmetry occurred. Asymmetry was defined as the difference in the occurrence of the two hemispheres' alpha EEG activity. The results of this experiment can be interpreted to mean that the subjects did not learn alpha asymmetry per se, but instead learned to increase then percent time of alpha and increase the alternations between alpha and no alpha. This condition is optimized when the subject has his eyes closed and is not performing a visual search. On the other hand, symmetry is optimized when the subject performs a visual task. Methodological problems in feedback training are discussed.

A visual analogue of Savin’s (1967) auditory task was used to examine preferred order of recall and order of recall accuracy for two pairs of visually superimposed digits. Savin (1967) and Rollins, Everson, and Schurman (1972) found that Ss preferred to recall simultaneous auditory information in successive order, even though the information was presented over a single channel. In the present experiments, Ss were found to prefer strongly to recall visual information in simultaneous order. On the other hand, the results of Rollins et al (1972), that Ss are equally accurate when forced to recall simultaneous auditory information in either the preferred or nonpreferred mode, were replicated for this visual task. The results of these experiments, together with the experiment reported by Rollins et al (1972), indicate that verbal information is processed differently by these two sensory systems.

On each trial of a short-term memory task, Ss were required to give the correct response to a paired-associate stimulus and to estimate the number of trials intervening between study and test on that stimulus. On trials where an incorrect paired-associate response was made, judgment of the number of intervening items was relatively independent of the actual number of intervening items. On trials where a correct paired-associate response was made, judgment of the number of intervening items was accurate for recent items but incorrect for more distant items.