Spatial Localization Task Research Articles

An electrophysiological dissociation of retrieval mode and retrieval orientation

The relationship between two classes of retrieval process—retrieval orientation and retrieval mode—was investigated by recording event-related potentials (ERPs) during the period in which participants were preparing to retrieve information from memory. Participants were cued on a trial-by-trial basis to complete either a semantic retrieval task or one of two episodic retrieval tasks (remember spatial location or remember encoding task). ERPs were recorded time-locked to the cues indicating which task to complete. There were commonalities between the ways in which ERPs evoked by the two episodic retrieval cues diverged from those evoked by the semantic cue. These shared differences are a likely correlate of processes related to retrieval mode. Critically, there were also reliable differences between the ERPs evoked by the two episodic cues. This novel finding is consistent with the view that participants adopted task-specific retrieval sets—retrieval orientations—which varied according to the kinds of episodic information that were to be retrieved.

Memória visuo-espacial a curto prazo: os efeitos da supressão articulatória e de uma tarefa aritmética

We investigated the nature of the information stored in visuo-spatial short-term memory in two experiments. In the first experiment, a spatial localization task was performed simultaneously with articulatory suppression and arithmetical subtraction tasks. The articulatory suppression has a negative effect on the performance with letters, but not with visual patterns. Despite that, the recall of the letters is better than the recall of the visual patterns. This result suggests that the storage of the visual patterns does not use the phonological loop, and that the articulatory suppression, even if it inhibits the use of the phonological loop, cannot inhibit the access to the semantic information. In the second experiment we established the effect of the visual similarity on the capacity of memory for the spatial position. The results confirm the use of visual codes and suggest that the storage capacity of the visual stimuli is limited, but not restricted to the recency items.

Spatial Learning and Shelter Selection by Juvenile Spotted Pythons, Anteresia maculosus

-Spatial abilities are important in mediating natural behaviors in snakes, such as localization of refuges. Twelve spotted pythons (Anteresia maculosus) were trained to find the location of an escape hole in a circular arena, given a choice of eight holes. A snake was deemed to have learned the task if it found the goal on eight out of the last ten acquisition trials. Only half of the animals learned the task after 32 training sessions. Manipulation of sensory cues after training suggests that subjects differed in their responses to manipulations in the environment, suggesting the use of different cues to find the goal. Ten of 12 animals were also tested for shelter preferences. Snakes were given a choice of three different shelter sites (submerged, on the surface, or elevated) to determine the relevance of the arena escape task. Most snakes preferred elevated shelters and showed fidelity to shelters chosen on the first day. These results suggest that juvenile spotted pythons may be more motivated to seek elevated, instead of submerged, refuges, and this may account for the failure of half of the snakes to learn the spatial location task. rnal of Herpetology, Vol. 34, No. 4, pp. 5 5-587, 2000 right 2000 Society for the Study of Amphibians and Reptiles atial Learning and Sh lter Selection by Juvenile Spot ed Pythons, Like most animals, snakes must rely on spatial abilities to find food sources and shelter effectively in their habitats. Most studies on spatial learning and memory have focused on rodents and birds (Bingman, 1990, 1992; Clayton and Krebs, 1992; Sherry et al., 1992). Studies on learning in reptiles have been conducted on turtles, tortoises, and lizards (reviewed in Burghardt, 1977; Brattstrom, 1978; Day et al., 1999), while snakes remain relatively unstudied. In the wild, snakes need to solve spatial tasks in order to find mates, foraging areas, ost animals, snakes must rely on spa4 Corresponding Author. and shelter. Field studies indicate that snakes are able to use celestial cues for orientation (Landreth, 1973; Newcomer et al., 1974; Lawson, 1989, 1994; Lawson and Secoy, 1991). In addition, displacement studies show that snakes actively select specific areas for shelter and can home to a hibernaculum or feeding s te (Noble and Clausen, 1936; Seibert and Hagen, 1947; Stickel and Cope, 1947; Hirth, 1966; Weatherhead and Robertson, 1990; Holtzman, 1998), suggesting that snakes must be able to orient themselves in their environment. Recent laboratory studies have also demonstrated that young corn snakes, Elaphe g. guttata, are able to learn to use and remember orientation cures to 575 This content downloaded from 157.55.39.147 on Sun, 07 Aug 2016 06:44:52 UTC All use subject to http://about.jstor.org/terms

The use of cognitive context in schizophrenia: an investigation.

Cognitive deficits in schizophrenia have recently been ascribed to impaired representation and use of cognitive context. Context is defined as relevant information held temporarily in mind to mediate appropriate but often non-habitual responses. Parallel studies in a variety of cognitive domains were designed in order to explore the generality of any schizophrenic deficit in context use. In all of the tasks (a Stroop task, a Continuous Performance Task and a cued spatial location task), we examined how performance was affected by the time for which contextual information must be held in mind, and by whether context or task demands were consistent or varying between trials. It was predicted that manipulation of these variables would produce tests especially sensitive to schizophrenic attentional problems. Predictions were partially confirmed. Although increasing contextual demands failed in most cases to produce disproportionate slowing of performance in patients, error data were largely in line with predictions. At the same time, the data did not suggest a simple unitary context deficit. Instead, different aspects of context--the time over which contextual information must be held in mind and the consistency of context--were differentially important in different tasks. The cognitive impairments of schizophrenic patients cannot be simply characterized as a generalized context deficit. A more differentiated, if not task specific, picture of schizophrenic deficits is suggested.

Auditory Inspection Time and Intelligence: A New Spatial Localization Task

Sixty-seven university undergraduates were tested on a new auditory inspection time (AIT) task based on the ability of human subjects to locate the left or right position of a stereophonic source and on a modified version of the Raven's Progressive Matrices (MRPM). The AIT task required subjects to locate the spatial position of a dichotic phantom lateralized by a phase difference to their left or right side that was backward masked by a high intensity source located in the midline of the head. Unlike previously described AIT tasks all subjects were able to perform the task. The log of AIT threshold was significantly correlated with the MRPM ( r=−0.37). In a further sample ( n=41) an r of −0.61 was observed; this latter sample was retested, with a delay of between 3 and 10 days and an r of −0.57 was obtained on this second occasion. In comparison, the correlation between visual inspection time (VIT) and MRPM in this sample was −0.41 and −0.21 on retest. Test–retest reliability for AIT was high (0.82) and comparable to that obtained in the same sample for VIT (0.76). It is concluded that this new AIT task appears to be accessible to a wider range of subjects than the successive frequency discrimination tasks employed by others.

Optimal spatial localization is limited by contrast sensitivity

Bisection is one of several spatial localization tasks that achieve hyperacuity performance levels. We find that optimal bisection thresholds, and hyperacuity tasks in general, are no better than might be expected from simple contrast detection and discrimination performance. The three-line bisection task can be described in terms of the test-pedestal paradigm where the test pattern is a horizontal dipole and the pedestal is a horizontal three-line pattern with equal spacing between the lines. When the dipole test is added to the center line, the line shifts up or down, depending on the test polarity. For low contrast pedestal lines at the optimal separation, the bisection threshold falls between the observer’s own dipole contrast detection threshold and the bottom of the dipole contrast discrimination dipper function. At higher pedestal strengths performance degrades with a slope of about 0.5–0.7, similar to that found in contrast discrimination tasks. Therefore, bisection performance is compatible with expectations based on contrast discrimination data. At large pedestal line separations (>10 min) bisection thresholds in min are about 1/60 the separation and relatively independent of pedestal strength. These findings are consistent with the idea that two processes are involved in limiting bisection performance; the first limit is based on contrast sensitivity of the system and the second limit to performance is based on a local sign or position tag processing. Finally, when bisection is compared with Vernier acuity and blur resolution tasks, where the test is also a dipole, bisection performance falls roughly midway, better than Vernier acuity but worse than blur resolution.

Memory for Spatial Location: Role of the Hippocampus in Mediating Spatial Pattern Separation

A paradigm based on measuring short-term memory for spatial location information as a function of spatial similarity between distal cues was developed to examine the role of pattern separation in the modulation of short-term memory for spatial information. A delayed-match-to-sample for spatial location task using a dryland version of the Morris water maze was used to assess spatial pattern separation in male Long-Evans rats. In the sample phase, animals were trained to displace an object that covered a baited food well in one of 15 spatial locations along a row of food wells perpendicular to a start box. In the ensuing choice phase, the animal was allowed to choose between two objects identical to the sample phase object. One covered the same baited food well as did the object in the study phase (correct choice), and another foil object (incorrect choice) covered a different unbaited food well along the row of wells. Five spatial separations were randomly used to separate the correct object from the foil object. After reaching a criterion before the operation, animals were given either hippocampal or cortical control lesions. In trials after the operation, control animals matched their performance before the operation across all spatial separations. In contrast, hippocampal-lesioned animals displayed impairments across all spatial separations with the exception of the longest (105 cm) spatial separation. The results suggest that the hippocampus may serve to separate incoming spatial information by temporarily storing one place separate from another. It is proposed that hippocampal lesions decrease efficiency in pattern separation, resulting in impairments in trials with increased spatial similarity among working-memory representations.

"Effect of defining features on inhibition in a spatial localization task": Correction to Simone et al (1998).

"Effect of defining features on inhibition in a spatial localization task": Correction to Simone et al (1998).

Lateral difference in the reproduction of arm positioning movement: an examination of the hypothesis on the levels of psychological processes.

The purpose of this study was to determine whether the hypothesis on the levels of psychological processes (Hatta, 1977, 1978) accounts for lateral differences in arm positioning movement (a spatial localization task). Fifteen right-handed male subjects were asked to perform a constrained criterion movement, 12 cm in length, with the left or right arm. Then, after a 10-sec retention interval, they were asked to perform the movement with the same arm, estimating lengths of 6, 12 or 24 cm. Different levels of psychological processes were assumed to be involved in estimating these various movement lengths--half, the same, or double that of the original. All possible combinations of the arm (left/right) and three movement length were tested. The CE scores were lower (more accurate) for the left arm (half; 1.5 +/- 8.1 mm, same; 4.3 +/- 6.2mm, double; 5.9 +/- 20.3 mm) than those for the right arm (half; 5.9 +/- 7.6 mm, same; 10.6 +/- 10.6 mm, double; 11.8 +/- 23.6 mm) in all conditions, indicating a lateral difference (the right hemisphere dominance) in arm positioning tasks. This typical lateral difference, which displayed no significant difference among conditions, is supposed to be mediated by complex or high-level psychological processes. These psychological processes are required by the subjects in the estimation of the various movement lengths. This study suggests that the level of psychological processes is a crucial factor in the manifestation of lateral differences in the performance of arm positioning movements.

Effect of defining features on inhibition in a spatial localization task.

Effect of defining features on inhibition in a spatial localization task.

Effect of defining features on inhibition in a spatial localization task.

Effect of defining features on inhibition in a spatial localization task.

Visuospatial Ability of Parkinsonians and Elderly Adults in Location Memory Tasks

Two experiments addressed the question of the spatial deficits of Parkinson disease (PD) patients, using a spatial location task which varied the characteristics of the task along an effortful continuum. In the more effortful task, 11 PD patients, 10 elderly control subjects, and 13 young control subjects were given 3 min to learn the layout of 12 places labeled on a map and then reproduce it. In the less effortful task, 9 new PD patients, 9 new elderly control subjects, and 10 new young control subjects were given 3 min to learn the layout of 12 black dots and then asked to reproduce it. In both cases the task was repeated twice. The results showed that PD patients were less accurate than young and elderly control subjects in the less effortful task. In contrast, the performances of PD patients and elderly control subjects were equivalent in the more effortful task. These results support the idea of a specific visuospatial deficit in Parkinson's disease. Moreover, the deficit in effortful tasks seems to be due to normal aging.

Effects of ibogaine on sensory-motor function, activity, and spatial learning in rats

Ibogaine, a naturally occurring alkaloid, has been show to reduce naloxone-precipitated withdrawal symptoms from morphine. Given the clinical possibilities, it is important to determine ibogaine's effects on sensory-motor function, activity, learning, and memory. Long-Evans rats injected with doses of 20–60 mg/kg of ibogaine displayed slower response times on sensory and sensory-motor tests and were impaired in performing specific motor reflexes at doses of 40–60 mg/kg. Furthermore, these rats showed a marked reduction in locomotor and nonlocomotor activity, as well as emotionality at doses ranging from 10–40 mg/kg. At the higher doses the rats appeared to be virtually inactive. There were also deficits in learning a spatial location task (a dry-land version of the Morris water-maze). The deficits, however, were probably due to a reduction in locomotor activity and reduction in detection of sensory information. In a final experiment, a single injection of 40 mg/kg of ibogaine had marked deleterious effects on the acquisition of the spatial location task 1 but not 7 days after the injection, even though in this case there were no effects on sensory motor function 1 or 7 days after the injection. Thus, there are severe sensory-motor activity and learning problems while the animal is under the influence of ibogaine (acute effect) as well as long-term consequences on learning without concomitant changes in sensory-motor function.

Localization of element clusters by the human visual system

A spatial localization task was used to determine the accuracy of localization of random element clusters about their centroid. The random element clusters were generated within a circular region and the observers' task was to decide whether the cluster lay to the right or left of a reference line, defined by two vertically separated reference elements. Both the reference elements and the cluster elements themselves were comprised of spatially narrowband stimuli (gabor patches), and were presented at a constant suprathreshold level. The thresholds for localization of the element cluster were measured with varying element number, and for a number of different sizes of circular region and element. The relationship between localization threshold and element number was not monotonie. Thresholds were found to rise with increasing element number up to about six elements within a region, and to then fall with further increase in element number. Asymptotic thresholds at high element number were indistinguishable from those obtained for filled circles of the same size. The results do not conform to any one of a number of models based on a centroid analysis alone. By manipulating the spatial and orientational properties of the elements comprising the cluster to be localized it was determined that the more central mechanism underlying localization receive input from different spatial and orientation filters.

Memory for spatial location: Functional dissociation of entorhinal cortex and hippocampus

To test whether there is a functional dissociation between the hippocampus and entorhinal cortex, rats were trained on a variable spatial-location matching-to-sample (working memory) task with various delays. After training, rats with entorhinal cortex, entorhinal-cortex-plus-hippocampus/subiculum, hippocampus, control, or cortical control lesions were tested for performance within the task. Results indicated that in the variable spatial-location condition relative to the control and cortical controls, all lesioned groups showed a profound impairment in performance of the task across all delays. They were subsequently tested for acquisition of a constant spatial location task. In the constant spatial-location condition, the entorhinal cortex and entorhinal-cortex-plus-hippocampus/subiculum lesioned groups did not learn the task, whereas the hippocampal lesioned group did. It is suggested that there is a functional dissociation between the hippocampus and the entorhinal cortex. It is proposed that the hippocampus encodes new spatial information within a working-memory system, whereas the entorhinal cortex represents spatial information within a reference-memory system as part of a spatial cognitive map.

Negative priming in a spatial localization task: Feature mismatching and distractor inhibition.

Negative priming has recently been demonstrated in tasks requiring spatial localization (S. P. Tipper, J. C. Brehaut, & J. Driver, 1990), supporting the notion that distractors are actively inhibited during selection. However, it has since been argued that this effect is caused by the appearance of mismatching identities at a single location (J. Park & N. Kanwisher, 1994). The present studies show that negative priming in a spatial localization task can occur when the ignored distractor and subsequent target are identical. However, feature mismatches can also lead to negative priming. The argument is made that distractor inhibition and implicit retrieval of previously presented items together provide a better account of efficient sequential selective behavior than does either process alone. Consider a bartender clearing glasses from a table. This apparently simple perceptual-motor interaction can be broken down into two complex stages of processing. The first stage encompasses the movement of the hand toward one glass among others in the same path of motion, and thus affords conflicting motor responses (see Tipper, Lortie, & Baylis, 1992). The second stage encompasses subsequent motor behavior after action toward the first glass has been completed. This second stage of processing is the focus of the present article. However, a complete understanding of how action is directed toward an object that was ignored in a recent perceptual-motor interaction begins with an understanding of the processing consequences of originally ignoring that object. Two mechanisms have been proposed to explain how action can be selectively directed toward one object when there are distracting objects in the scene. Most early models of selective attention proposed that internal representations of the attended object receive analysis beyond that of initial perceptual processing. This extra level of excitation was considered sufficient to separate the target from distractor (Broadbent, 1958, 1982; Van der Heijden, 1981). More recently, inhibitory mechanisms have been proposed to play a role complementary to that of excitation in separating

Negative priming in a spatial localization task: Feature mismatching and distractor inhibition.

Negative priming in a spatial localization task: Feature mismatching and distractor inhibition.

Contrast sensitivity and vernier acuity in amblyopic monkeys

Human psychophysical studies suggest that strabismic and anisometropic amblyopes may have characteristically different patterns of visual loss. In particular, anisometropic amblyopes often show deficits on spatial localization tasks that scale with their spatial resolution losses, whereas strabismic amblyopes can show localization deficits that are large relative to their losses in spatial resolution. We have compared the performance of non-human primates with experimentally-induced anisometropic and strabismic amblyopia on contrast detection and vernier acuity tasks. The performance of both groups of animals was fundamentally similar: both strabismic and anisometropic monkeys showed deficits in spatial localization that were large relative to their resolution losses, although the animals with the most disproportionate losses were strabismic. We investigated the extent to which contrast sensitivity losses accounted for the vernier acuity deficits. The results showed that, in most cases of either strabismic or anisometropic amblyopia, when the vernier stimuli for each eye were equated in terms of effective contrast, the extent of the vernier acuity deficit was reduced to approximately the extent of the spatial resolution deficit. In two cases, both of strabismic amblyopia, we found that equating the stimuli in this way was not sufficient to make the deficits equal, a pattern that has been described for human strabismic amblyopes.

Color-Mediated Contrast Sensitivity in Disabled Readers

Specific deficits in the processing of transient visual stimuli have been identified in reading-disabled children. It has been suggested that suitably chosen colored filters can assist reading-disabled children but this is controversial. In order to assess how colored lenses might assist a reading-disabled child, we compared contrast sensitivity judgments of 20 disabled readers with those made by 20 good readers of the same age. Contrast sensitivity thresholds were measured over a spatial frequency range of 0.4 to 12.8 cpd. Contrast sensitivity functions were recorded for each child under four different conditions. For each condition the child wore a spectacle frame with a colored filter which had been selected on the basis of the child's best and worst performances on a spatial location task (BEST and WORST), a neutral density optical filter (GRAY), and an untinted filter (CLEAR). The results showed that the best colored filter selected for each of the disabled readers dramatically reduced sensitivity as the spatial frequency moved into the range of printed material (i.e., sensitivity declined sharply from 0.4 to 12.8 cpd). In contrast, there was very little change in sensitivity for the good readers using their best filters. These provocative findings suggest that colored optical filters might improve transient-on-sustained inhibition in disabled readers. It is possible that individually designed filters will provide a way of mitigating the effects of weak transient processing in reading-disabled children. However, our results should not be interpreted as supporting the efficacy of prescribed, colored optical filters as a remediation technique for reading disability.

Dissociation of object and spatial visual processing pathways in human extrastriate cortex.

The existence and neuroanatomical locations of separate extrastriate visual pathways for object recognition and spatial localization were investigated in healthy young men. Regional cerebral blood flow was measured by positron emission tomography and bolus injections of H2(15)O, while subjects performed face matching, dot-location matching, or sensorimotor control tasks. Both visual matching tasks activated lateral occipital cortex. Face discrimination alone activated a region of occipitotemporal cortex that was anterior and inferior to the occipital area activated by both tasks. The spatial location task alone activated a region of lateral superior parietal cortex. Perisylvian and anterior temporal cortices were not activated by either task. These results demonstrate the existence of three functionally dissociable regions of human visual extrastriate cortex. The ventral and dorsal locations of the regions specialized for object recognition and spatial localization, respectively, suggest some homology between human and nonhuman primate extrastriate cortex, with displacement in human brain, possibly related to the evolution of phylogenetically newer cortical areas.