Virtual reality, disability and rehabilitation

Virtual reality, or virtual environment computer technology, generates simulated objects and events with which people can interact. Existing and potential applications for this technology in the field of disability and rehabilitation are discussed. The main benefits identified for disabled people are that they can engage in a range of activities in a simulator relatively free from the limitations imposed by their disability, and they can do so in safety. Evidence that the knowledge and skills acquired by disabled individuals in simulated environments can transfer to the real world is presented. In particular, spatial information and life skills learned in a virtual environment have been shown to transfer to the real world. Applications for visually impaired people are discussed, and the potential for medical interventions and the assessment and treatment of neurological damage are considered. Finally some current limitations of the technology, and ethical concerns in relation to disability, are discussed.

Visual search, perception, and visual-motor skill in "healthy" children born at 27-32 weeks' gestation

Visual-perceptual, attentional, and visual-motor skills were examined in a group of 16 school-age children, born at 27-32 gestational weeks, who had performed normally on pediatric screening tests. Compared with 16 matched full-term controls, the preterms performed poorly on only two measures: they took longer to point to the missing arc of an annulus displayed on a computer screen and failed to find targets more often in a complex visual search task. They showed no deficits on tests of visual form extraction and closure. These data suggest that in the absence of any disability that is clinically detectable, prematurity results in a cluster of small but significant visual-motor impairments that persist into middle childhood. These relate to the maintenance of attention and visual-motor coordination, though visual form perception is not measurably affected. The results are discussed in the context of current neurobiological models of visual system organization.

Transfer of spatial information from a virtual to a real environment in physically disabled children

A group 10 severely physically disabled children explored a to-scale computer simulation of a real multi-storey building. Following exploration, their knowledge of the spatial properties of the real environment was assessed by asking them to point to fire apparatus that was not visible from the test site. Subjects in a control group were asked to complete the same assessment tasks, but without the opportunity to explore either the real building or the computer simulation. The estimates of the disabled children were superior to the control group indicating good transfer of spatial knowledge. Route finding and recognition reports provided support for the pointing data in indicating good transfer of spatial information.

Effects of parietal cortex lesions on spatial problem solving in the rat

The Maier 3-table task was used to examine spatial representations in rats with lesions of the parietal cortex. Some animals had anteriorly placed lesions, some posteriorly placed in cortical areas, sometimes regarded as 'parietal' in earlier studies. After 5 days of familiarization, animals were given 18 days of testing on the standard Maier task. Both parietal groups were initially impaired, but reached the same level of performance as controls by the end of the test period. Learning occurred both within and between sessions for the anterior group, but only between sessions for the posterior group. There was no major functional differentiation apparent on this task between the two 'parietal' areas. Rate of exploration increased in both parietal groups across test sessions as task performance improved. It is argued that the change in exploratory activity across sessions in parietal groups may reflect the adoption of a compensatory strategy which improved performance, but that improvement could also have been due to neural changes, as structures, such as the frontal cortex or hippocampus, assume some functions normally mediated by the parietal area.

Distractibility and locomotor activity in rat following intra-collicular injection of a serotonin 1B-1D agonist

The superior colliculus (SC) is thought to be the decision center for reactions to novel and/or moving stimuli in the peripheral visual field. Serotonin 1B (5-HT1B) receptors were previously demonstrated to be located on collicular axon terminals of retinal ganglion cells and their activation might depress afferent inputs from the retina. The effects of intra-collicular injections of 5-HT1 drugs on distractibility were studied in hooded rats trained to run toward illuminated targets for a food reward in a 2-choice runway. 8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT), a 5-HT1A receptor agonist, RU 24969, a mixed 5-HT1A and 5-HT1B agonist, serotonin-O-carboxymethylglycyltyrosinamide (S-CM-GTNH2), a mixed 5-HT1B and 5-HT1D receptor agonist and saline (control) were alternately injected. Following the S-CM-GTNH2 treatment alone, animals exhibited an erratic running style, involving side-to-side movements of the head, without change in the overall accuracy of their locomotor trajectories, but with substantial decrease in their running speed. When distracting peripheral lights were introduced at the mid-points of the animals' run, in the weaker distracting condition (unilateral distractor) only, distraction indexes were found lower following the S-CM-GTNH2 treatment than following the other drug or saline treatments. It is concluded that serotonin, via 5-HT1B-1D receptors, may induce an elevation of the visual distractibility threshold by modulating directly the transmission of the primary visual signal.

Immunomodulatory effects of human neuroblastoma cells transduced with a retroviral vector encoding interleukin-2

We have investigated whether retroviral mediated transfer of the IL-2 gene renders human neuroblastoma cells immunogenic, justifying their use in a clinical tumor immunization study. Fourteen neuroblastoma cell lines were established from patients with disseminated neuroblastoma and transduced with the vector G1Ncvl2, which contains the neomycin phosphotransferase gene and the cDNA of the human interleukin-2 gene. Clones secreting > 150 pg/10(6) cells/24 h of IL-2 were selected for further study. Secretion of IL-2 was maintained for at least 3 weeks in nonselective media, implying that production of the cytokine would continue under in vivo conditions. Co-culture of IL-2 transduced cell lines with patient lymphocytes induced potent cytotoxic activity against both transduced and parental neuroblastoma cell lines. This activity was HLA unrestricted, and predominantly mediated by CD16+ or CD56+ and CD8- lymphocytes. These data form the preclinical justification for our current immunization protocol for patients with relapsed or resistant neuroblastoma.

Choice autonomy and memory for spatial locations in six-year-old children

Six-year-old children were presented with 12 identically labelled locations in a room and required to search non-redundantly for the six that contained rewards. On each day they could commit Across-Trial Memory (ATM) errors by visiting non-rewarded locations, or Within-Trial Memory (WTM) errors by revisiting locations previously visited that day. Groups were trained for nine days, either walking or pushed in a wheelchair, and with or without freedom of choice. They were then tested, walking with freedom of choice. Performance of the task improved significantly across training days in groups allowed free choice, whether walking or transported, and was superior at test to that of non-choosing groups. Throughout training and testing, the ATM component of performance was superior in groups allowed free choice. WTM was more accurate than would be expected by chance in all subjects at all stages of the experiment, but did not differ between groups. The problem of comparing WTM scores in groups differing in ATM accuracy was discussed. It was concluded that the primary benefit of free choice in spatial memory tasks is that it promotes accurate environmental segmentation, and that WTM is little affected by training or environmental familiarity.

A rapid test of rodents' vision using a modified open field apparatus

Rats' responses to visual change in the environment were recorded in open field arenas in which a part or all of the visual environment could be altered without changing nonvisual features. Rats responded to a change in the appearance of one quadrant of a field by selectively reexploring the changed quadrant, and to a change in the whole environment by generally increasing their locomotor activity. The latter effect was equally large whether the change was from a patterned to a blank environment, or vice-versa. The present paradigms provide a rapid means of testing animals' vision.

The impact of burn injury: a preliminary investigation

Thirty-eight individuals who had been previously hospitalized for burn injuries were interviewed about the problems that they had experienced as a result of their injuries, their rehabilitation goals, and factors that they believed had influenced either the rate or extent of their recovery. The problems that were most frequently mentioned by participants were compared with problem areas that are covered by the Burn-Specific Health scale, which is a standardized measure designed to assess the impact of burn injury. Our findings suggest that although many problem areas are well covered by the Burn-Specific Health scale, other areas are covered less well. Thus more work is needed to refine the scale to capture more fully the wide variety of problems that are experienced by survivors of burn injuries. In general, patients' rehabilitation goals reflected the types of problems they experienced. Support from health care providers was the most frequently mentioned facilitator to recovery, which emphasizes the importance of the patient-provider relationship.

Object exploration and reactions to spatial and nonspatial changes in hooded rats following damage to parietal cortex or hippocampal formation

Hooded rats with bilateral lesions of the anterior part of the hippocampal formation (HIP), anterior region of the posterior parietal cortex (APC), or posterior region of the posterior parietal cortex (PPC) were compared with controls for their exploration of 5 objects in an open field, habituation of locomotion and object investigation, and response to spatial and nonspatial change. First, all groups displayed habituation of both locomotor and exploratory activity. Second, controls selectively reexplored displaced objects, and APC-lesioned rats reexplored all objects, whereas PPC- and HIP-lesioned rats failed to react to the spatial change. Third, a novel object induced reexploration in all groups. The results are consistent with the roles of the HIP and PPC in spatial information processing. Moreover, the APC and PPC are involved in attentional effortful processing and visuospatial information processing necessary for spatial representation, respectively.

Visually guided locomotion, distractibility, and the missing-stimulus effect in hooded rats with unilateral or bilateral lesions of parietal cortex

When hooded rats with bilateral lesions of Krieg's area 7 (parietal cortex) were trained to locomote toward visual targets in a runway, they ran less accurately than did controls, although unilaterals ran accurately. When flashing lights were presented unexpectedly during their run, bilateral parietals were less disrupted than were controls, but they failed to show total neglect. Unilateral paritals turned toward distracters on either side but turned preferentially toward distracters contralateral to the intact hemisphere, particularly when distracters occurred bilaterally and simultaneously. Effects due to the omission of expected distracters were similar in parietals and controls. Rat parietal cortex is not essential for the redirection of attention to stimuli notable for their unexpected presence or absence, but parietal cortex may resolve interhemispheric competition. The results suggest a homology between parietal cortex in rat and primate.

Exploratory activity and response to a spatial change in rats with hippocampal or posterior parietal cortical lesions

Rats with bilateral lesions of posterior parietal cortex (PPC: Krieg's Area 7) or dorsal hippocampus (HIP) were compared with controls for their response to environmental change. In the first experiment, following subjects' exploration of a relatively homogeneous open-field environment, a stimulus-rat was introduced at a particular location beneath the glass floor. All groups selectively explored the location of the stimulus-rat, but only the control and PPC groups displayed habituation. On removal of the stimulus-rat, only the control group selectively re-explored the place where the stimulus-rat had been. A second experiment, similar to the first, used additional prominent visual cues beneath the floor. When the cues were spatially separate from the location of the stimulus-rat (Dissociated object condition), the same results were obtained as in the first experiment. When the additional cues were positioned close to the stimulus-rat location (Associated object condition), habituation occurred in all groups including the hippocampal group, and again the removal of the stimulus-rat resulted in a selective re-exploration of its former location in the control group only. However, a selective preference for staying at the stimulus-rat's previous location was found in PPC animals as in controls. Hippocampal rats failed to investigate the location of the missing stimulus in all conditions. The results confirm the role played by the hippocampus in spatial memory and suggest that the posterior parietal cortex is involved in the cognitive-demanding aspects of spatial encoding, particularly in environments that are poorly visually differentiated.

Visually guided locomotion, distractibility, and the missing-stimulus effect in hooded rats with unilateral or bilateral lesions of parietal cortex

When hooded rats with bilateral lesions of Krieg's area 7 (parietal cortex) were trained to locomote toward visual targets in a runway, they ran less accurately than did controls, although unilaterals ran accurately. When flashing lights were presented unexpectedly during their run, bilateral parietals were less disrupted than were controls, but they failed to show total neglect. Unilateral paritals turned toward distracters on either side but turned preferentially toward distracters contralateral to the intact hemisphere, particularly when distracters occurred bilaterally and simultaneously. Effects due to the omission of expected distracters were similar in parietals and controls. Rat parietal cortex is not essential for the redirection of attention to stimuli notable for their unexpected presence or absence, but parietal cortex may resolve interhemispheric competition. The results suggest a homology between parietal cortex in rat and primate.

The development of exploration and spontaneous alternation in hooded rat pups: effects of unusually early eyelid opening

Changes in exploratory activity and spontaneous alternation were examined across postnatal Days 8-31 in Lister hooded rat pups whose eyelids were surgically opened at 6-8 postnatal days. Compared with controls, whose eyes open naturally at 14-16 days, the treated animals showed accelerated behavioral development. Open-field activity increased more rapidly in the week following surgery, but only when all pups in the litter had their eyelids opened, and not when only half of the litter was treated. Rearing on the hind paws emerged earlier in treated animals, but grooming was unaffected. Pups having unilateral early eyelid opening made pivotal circling movements contraversive to the opened eye in an open-field arena in the early neonatal period. When tested in a T-maze, treated pups showed earlier spontaneous alternation than controls. Possible physiological systems underlying such changes are discussed. Our results show that unusually early visual stimulation has behavioral consequences, producing a brief speeding of some attentional and investigatory behaviors, though such changes may also depend upon environmental factors.

Tonic and phasic orientation in full-term and preterm infants

Thirty-three full-term infants and thirty-eight preterm infants (on average born at 30 weeks gestation) were tested for their latency to turn toward checkered stimulus patterns (phasic orienting or "attention-getting") and for the duration of their initial fixation (tonic orienting or "attention-holding"). Plotted against the logarithm of the subjects' postconceptional age, turning latency fell linearly between 36 and 120 weeks, while fixation time fell abruptly at 53 weeks. Preterm and full-term infants showed the same developmental trends, implying that both of these attentional behaviors are biologically timetabled and that neither is greatly affected by premature extrauterine experience. Unexpectedly, phasic orientation in the first 30 postnatal days was significantly faster in preterm than in full-term infants, and fixation times failed to differ. Despite the necessary functional integration of phasic and tonic orienting in mature visual scanning and attention, the present results suggest an independence in their early postnatal development and that neither is mature at birth.

Correlates of performance on the Gollin and Mooney tests of visual closure

One hundred and twenty-seven undergraduate students variously performed a computerized version of the Gollin (1960) Incomplete Figures Test, the Mooney (1957) Test of Incomplete Face Perception, the Poppelreuter (1917) Overlapping Figures Test, and a visual search task. Performance of male subjects was superior to that of female subjects on the Mooney test but inferior on the visual search task. Correlation and regression analyses showed that the only significant predictor of Gollin test scores was latency to identify all items in the Overlapping Figures Test. There was no relationship between performances on the Gollin and Mooney tests or between Gollin or Mooney test performance and visual search latency. The Gollin and Mooney tests appear to access different perceptual processes, none of which is dependent on the efficiency of visual search.

Development of reference and working spatial memory in preschool children

Three groups of preschool children (aged 18 to 28, 33 to 42, and 47 to 58 months) were given a radial search test similar to the radial arm maze used with nonhuman subjects. The children searched for chocolate sweets among 10 labeled locations in a room, 5 of which were baited with a sweet. Older children outperformed the intermediate group, who in turn outperformed the youngest group in requiring fewer choices to retrieve all of the sweets. Working memory and reference memory aspects of performance were then separated: Reference memory (restriction of choices to the baited subset) in older children was superior to that in the youngest group but not to that in the intermediate group. In terms of working memory (avoidance of repeat responses to already visited locations), the older group made fewer errors than the intermediate group, who, in turn, made fewer errors than the youngest group. We concluded that working and reference components of spatial memory in children may share common elements, perhaps the ability to recognize places as familiar, although reference memory may develop earlier than working memory.

Spontaneous and learned turning behaviour in food- or water-restricted hooded rats

Some laboratory studies have suggested that whereas food restriction in animals leads to response alternation (behavioural flexibility), water restriction induces perseverative, stereotyped responding. Hooded rats, restricted to 1 hour per day access to either food or water, were tested on a radial-arm maze (using a procedure that eliminates algorithmic response strategies), for alternation in a 3-arm maze (both when the maze was familiar and unfamiliar, and with or without differential reward) and a 2-choice maze in which some animals were taught to alternate direction of turn, and others to perseverate. Both groups performed the radial-arm maze task competently and spontaneously alternated at a high rate. In the learned task, food-restricted rats were slower than water-restricted to reverse a consistent direction of turn; in the alternation condition, water-restricted rats developed a temporary, but strong, directional bias when making their first choice each day. Water-restricted subjects took water more readily than food-restricted took food when initially introduced to the apparatuses, but there was no consistent difference in motivation in the two conditions. The results provide little support for the notion that distinct cognitive-motivational states or behavioural strategies are induced by food- and water-restriction.

Locomotion, active choice, and spatial memory in children

In two studies, children between 4 and 6 years old were tested on a radial search task requiring nonredundant sampling of eight identically labeled positions in a room. In the training phase (5 days), children made free choices by walking between positions, were passively transported in a pushchair, actively directed their own route from a pushchair, or were led on foot to positions selected by the experimenter. When tested (whether walking or directing while seated in a pushchair), children who had either walked independently or directed the experimenter while being pushed performed competently; those led on foot without spatial choice performed almost as well. Only the children who had neither independent locomotor experience nor autonomous choice performed very poorly. The results are related to neurobiological models of spatial cognition and may have implications for the transportation of children with mobility problems.

Intermodal enhancement of stimulus localisation in infants born prematurely

The interaction of auditory and visual modalities in the enhancement of orientation was examined in premature and near-term infants by presenting them auditory or visual stimuli or auditory-visual stimulus combinations at various positions in sensory space. In 4.5--15-mo-olds, brisk orienting responses could be elicited to very peripheral stimulus positions but only when the stimulus consisted of a spatially coherent auditory-visual combination (i.e., where a sound and a light occurred at the same point in space). This occurred for all infants, irrespective of age or gestational age at birth. First, the result shows that infants can respond to visual stimuli at eccentric positions, beyond the supposed limits of their effective visual fields as measured by standard perimetry. Second, the result extends earlier studies showing that intersensory integration and stimulus localisation develop relatively normally in prematurely born infants. The auditory-visual enhancement test as used here may have a number of further uses and applications in the clinic and laboratory.

High doses of caffeine impair performance of a numerical version of the Stroop task in men

The effects of caffeine ingestion on mid-morning cognitive performance were investigated in thirty-two male subjects. These were given drinks containing either no caffeine, 125 mg caffeine (mean dose: 1.38 mg/kg), or 250 mg caffeine (mean dose: 3.45 mg/kg) and were tested on three tasks: 1) free recall of supraspan word lists, 2) a response time (pointing) task and 3) a numerical Stroop task. There were no significant group differences on the recall task or in response times, but subjects having the higher caffeine dose were seriously impaired on the Stroop test, making particularly slow responses. Caffeine may have a deleterious effect on the rapid processing of ambiguous or confusing stimuli, and this may account for its clear effect on the Stroop test than on other cognitive tests used hitherto.

The Gollin incomplete figures test: a flexible, computerised version

The Gollin incomplete figures test has been used as a measure of visual development, as a clinical test for parietal cortex dysfunction, and to examine long-term memory in amnesic patients. It has traditionally been administered by using a series of three or five stimulus cards, successive cards containing progressively more information. A study is reported in which digitised outline drawings of familiar objects were presented via a computer, the percentage of the figure on the screen slowly increasing from 0 to 100. The original findings of Gollin were successfully replicated; children's performance on the task improved markedly over the age range 2-5 years, and performance improved dramatically over three tests in all subjects. Computerisation of the Gollin task provides a precise and versatile alternative to the original card version.

Spatial memory in preschool infants

In order to test the spatial competence of preschool infants, two groups, aged 2 years and 4 years, were tested on a version of the "radial maze" task. They were required to obtain a chocolate sweet from each of eight identically labelled positions in an unfamiliar room. Four-year-olds accomplished this with considerable accuracy, rarely revisiting previously sampled positions. Two-year-olds performed marginally above chance. Variants of the task were employed, including rotation of the room configuration so that labelled positions were rendered ambiguous with respect to all other environmental stimuli. The latter caused a marked fall in performance in those infants that had been scoring above chance. By these criteria, infants clearly possess a form of intuitive "spatial memory" that is likely to mature during the second and third years. Parameters of performance were remarkably similar to those seen in comparable studies with nonhumans. It is likely that hippocampal development in early infancy underlies this evolving skill, assuming cross-species similarity in the organization of spatial behavior, and that locomotor competence is required for its development.

Distractibility following simultaneous bilateral lesions of the superior colliculus or medial frontal cortex in the rat

Hooded rats with bilateral lesions of the superior colliculus or medial frontal cortex were compared with controls for locomotor guidance in shuttling back and forth between goal-doors at two opposite ends of a large arena. Colliculectomized rats accomplished this with great accuracy. When flashing distractor lights were introduced midway down the runway, frontal corticals and controls were severely disrupted but colliculars continued to run normally. This result was obtained both when all training occurred postoperatively (Experiment 1) and when runway performance had been stabilized preoperatively (Experiment 2), thus after a long or short postoperative recovery interval. The results offer support for previous studies with rats which have demonstrated sensory 'neglect' but good locomotor guidance after collicular ablation. Frontal corticals differed from controls only in terms of their elevated rate of repeat door-pressing upon postoperative resumption of testing in Experiment 2. Despite the similarity between effects reported elsewhere of collicular and frontal lesions made unilaterally, bilateral deficits clearly demonstrable after collicular ablation were absent here after frontal lesions. The results imply that the functional responsibilities of superior colliculus and frontal cortex in the rat are separable; at least, they have different rates of functional recovery.