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At least 289 records · Page 16Linked to original sources
PubMed2006

Treatment with MDMA from P11-20 disrupts spatial learning and path integration learning in adolescent rats but only spatial learning in older rats.

RATIONALE: Previous studies in rats showed that postnatal day (P)11-20 exposure to +/-3,4-methylenedioxymethamphetamine (MDMA, ecstasy) causes learning and memory deficits in adulthood. The emergence and permanence of these learning deficits are currently unknown. OBJECTIVE: This study was designed to investigate learning and memory deficits in adolescent (P30 or P40) and older (P180 or P360) rats exposed to MDMA from P11-20. MATERIALS AND METHODS: Within each litter half the animals were exposed to MDMA (20 mg/kg) and half to saline (SAL) twice a day (8 h apart) from P11-20. In experiment (exp) 1, behavioral testing began on either P30 or P40, whereas in exp 2, testing began on either P180 or P360. Offspring were tested in the Cincinnati water maze (CWM), a test of path integration learning (2 trials/day for 5 days), and the Morris water maze (MWM) (three phases, with 5 days of 4 trials/day and a probe trial on the sixth day per phase). RESULTS: MDMA-treated rats took longer to find the platform and traveled a greater distance to find the platform at all ages tested in all phases of the MWM. MDMA-treated animals also spent less time in the target quadrant during probe trials. In the CWM, P30 and P40 animals took longer to find the goal and committed more errors in locating the goal, while P180 and P360 MDMA-treated animals performed similarly to SAL-treated animals. CONCLUSION: The data suggest that the spatial learning and memory deficits induced by MDMA are long lasting, while the path integration deficits recover over time.

Age Factors↗
PubMed1985

Spatial perspective taking: coordination of left-right and near-far spatial dimensions.

Second- and fourth-grade children viewed a cylindrical object in nine positions on a square display board marked with a 3 X 3 grid. As the object was placed in each position children identified the view from 90, 180, or 270 degrees positions around the display from a set of photographs. Perspectives in which the object differed from the child's view in both left-right and near-far dimensions were more difficult than perspectives that only transformed one dimension. Error rates decreased with age. There were no main effects of left-right vs near-far or of observer position. Rates of egocentric responding were high at both ages. We note that the complementary spatial dimension to left-right is near-far not front-back. Moreover, the relative ease of front-back transformations in previous research resulted from distinctive front-back cues on the display objects which enabled subjects to use nonspatial strategies to identify observer perspectives.

Child↗
PubMed2006

The effects of forced exercise on hippocampal plasticity in the rat: A comparison of LTP, spatial- and non-spatial learning.

Physical activity may have the potential to improve cognitive function. Here we show that forced treadmill-running results in selective improvements in hippocampal plasticity. Rats that underwent exercise training demonstrated enhanced expression of long-term potentiation in dentate gyrus and enhanced object recognition learning. Spatial learning in the Morris watermaze was unaffected by exercise. These changes were associated with an increase in expression of brain-derived neurotrophic factor in the dentate gyrus.

Analysis of Variance↗
PubMed1997

Spatial-Semantic Display Processing: The Role of Spatial Structure on Recall

The purpose of the present study was to test a model of spatial-semantic display processing by comparing the aided and unaided recall of information presented in a node-link format (knowledge map) to the aided and unaided recall of information presented in a text format. Structural icons of the knowledge map and text with the verbiage removed were used to aid retrieval in some conditions. Participants were randomly assigned to one of eight groups formed by the complete crossing of three factors: knowledge map versus text, structural icon at recall versus no structural icon at recall, and immediate versus delayed recall. Knowledge map groups outperformed text groups on essay tests and they more accurately remembered where information was located within the materials. Both knowledge map and text icon-aided recall groups had significantly better performance than the no icon, unaided recall groups (particularly on main ideas).

Journal Article↗
PubMed1982

Spatial properties of the visual detectability of moving spatial white noise.

We determined the spatial parameters that described the visual detection of spatio-temporal correlation in moving two-dimensional noise patterns. The target field (5.21 x 5.31 deg of visual angle) was divided into horizontal stripes of equal width D. Adjacent bars alternately contained noise patterns moving with velocity leads to V1 and leads to V2. We varied D, leads to V1 and leads to V2. Roughly three different percepts occurred. If the stripes were very broad the different movements in alternate stripes were perceived together with the division of the field into stripes. If the stripes were very narrow the division into stripes was not seen, but the moving noise patterns with velocities leads to V1 and leads to V2 were perceived as transparent sheets moving through each other. For intermediate stripe widths the target field looked incoherent and the subject was not clear about the percept. In this region the subject found it difficult and sometimes impossible to discriminate these patterns from a completely uncorrelated spatio-temporal white noise pattern (snow). To quantify the detectability, the patterns were masked with snow (spatio-temporal white noise). The r.m.s. contrast of the total stimulus was kept at a constant value, whereas the subject set the signal-to-noise ratio (SNR) to a threshold value. At certain bar width the thresholds reached a maximum value. Thse critical bar widths depended on the velocities leads to V1 and leads to V2. These critical bar widths were interpreted in terms of a simple general model for the detection of spatio-temporal correlation. In these terms the span of the elementary correlators rose monotonically with the velocity to which the correlator is most sensitive.

Acoustic Stimulation↗
PubMed1989

Selective spatial attention and length representation in normal subjects and in patients with unilateral spatial neglect.

The aim of this study was to assess whether perceptual representation along the horizontal axis is affected by hemispace position of the stimulus or by orienting attention to one side. Ten control subjects and 10 right brain damaged patients with left unilateral spatial neglect (USN) were asked to bisect lines of five lengths in three space positions (left, center, right) and under three cueing conditions (no cue, left cue, right cue). Normal controls showed significant displacement of bisection opposite to the side of hemispace presentation and toward the side of cueing. USN patients showed a bisection error toward the right end which increased with lines placed in the left hemispace and decreased with lines placed in the right hemispace and when attention was oriented toward the left side. We conclude that (1) In absence of cues normal subjects tend to overestimate the portions of space closer to their body midline; (2) both normal and USN patients tend to overestimate portions of space that they direct their attention to; (3) USN patients' performance without cueing is consistent with an attentional shift toward the right hemispace implying a gradient of overestimation of the right-most portions of space. A common neural substratum for directing attention and space representation can explain these findings.

Aged↗
PubMed1993

Monkey hippocampal neuron responses related to spatial and non-spatial influence.

Activity in the monkey hippocampal formation (HF) was analyzed during movement guided by auditory and visual cues. The monkey could control a motorized cab by pressing the proper 1 of 4 available levers within a 2.5 x 2.5 m field. Of 238 HF neurons analyzed, responses of 79 were place related and responses of 110 were task related. Of the task-related neurons, 33 were also place related, and responded to task cues only where place-related responses occurred. The results suggest HF gating of incoming non-spatial information, depending on information about location.

Acoustic Stimulation↗
PubMed2006

Selective attention to spatial and non-spatial visual stimuli is affected differentially by age: effects on event-related brain potentials and performance data.

To assess selective attention processes in young and old adults, behavioral and event-related potential (ERP) measures were recorded. Streams of visual stimuli were presented from left or right locations (Experiment 1) or from a central location and comprising two different spatial frequencies (Experiment 2). In both experiments, results were compared in visual-only and visual+auditory stimulus context conditions. Participants were forced to respond fast in both experiments, while maintaining high accuracy. In Experiment 1, no behavioral effects of aging were found; however, an enlargement of the N1 component in the older age group suggested that older adults initial selection process was larger than that of young adults. A late frontal effect following the P300 elicited by attended non-targets was larger in the visual+auditory condition than in the visual-only condition in the old age group. This effect was interpreted as reflecting a memory update of the relevant target location. In Experiment 2, older adults made relatively more errors in the visual+auditory condition than in visual-only condition, more so than the young adults. Older adults' ERP data were also characterized by an enlargement of the occipital selection negativity, compared to the young age group. In contrast to experiment 1, no late frontal post-P3 effect could be found, suggesting that the memory trace of the relevant stimulus feature was updated less frequently, explaining the reduction in response accuracy in the visual+auditory stimulus context conditions.

Acoustic Stimulation↗
PubMed2003

Effects of same- and different-modality cues in a Posner task: extinction-type, spatial, and non-spatial deficits after right-hemispheric stroke.

The response delay to left target stimuli preceded by right-side cues, first described by Posner et al. [J. Neurosci. 4 (1984) 1863-1874] appears to be a stable marker of right-parietal injury. However, only few studies compared patients' performance to age-matched controls. Furthermore, only few studies compared visual and auditory stimuli in this task. Therefore, two groups of right-hemisphere stroke patients, with and without left visual hemineglect, and a healthy control group were studied in three versions of Posner's paradigm. Visual or auditory target stimuli were presented to the subject's left or right, following a visual or auditory cue by 150 ms. The classical 'extinction-type' effect, an increase in missing responses for right visual cue/left visual target, was specifically observed in neglect patients. In the same condition, an 'extinction-type' response delay was present in patients with neglect and in those without neglect. No such delay occurred in any group when cues were auditory. Specifically in neglect patients, response times were generally longer for left than for right visual targets, regardless of cue side and of cue modality. Response times were generally prolonged in neglect patients regardless of target modality. This suggests that three components impair neglect patients' performance in this paradigm: a non-spatial, supramodal deficit, a global, neglect-type deficit of the contralesional hemi-field, and the extinction-type impairment. The latter two deficits appear to be most marked within the visual domain.

Acoustic Stimulation↗
PubMed2003

Multimodal spatial representations engaged in human parietal cortex during both saccadic and manual spatial orienting.

BACKGROUND: Recent neuroimaging studies have found that several areas of the human brain, including parietal regions, can respond multimodally. But given single-cell evidence that responses in primate parietal cortex can be motor-related, some of the human multimodal activations might reflect convergent activation of potentially motor-related areas, rather than multimodal representations of space independent of motor factors. Here we crossed sensory stimulation of different modalities (vision or touch, in left or right hemifield) with spatially directed responses to such stimulation by different effector-systems (saccadic or manual). RESULTS: The fMRI results revealed representations of contralateral space in both the posterior part of the superior parietal gyrus and the anterior intraparietal sulcus that activated independently of both sensory modality and motor response. Multimodal saccade-related or manual-related activations were found, by contrast, in different regions of parietal cortex. CONCLUSIONS: Whereas some parietal regions have specific motor functions, others are engaged during the execution of movements to the contralateral hemifield irrespective of both input modality and the type of motor effector.

Adult↗
PubMed2005

Information processing flow and neural activations in the dorsolateral prefrontal cortex in the Stroop task in schizophrenic patients. A spatially filtered MEG analysis with high temporal and spatial resolution.

Using a spatially filtered magnetoencephalography analysis (synthetic aperture magnetometry), we estimated neural activations in the Stroop task in nearly real time for schizophrenic patients with/without auditory hallucinations and for normal control subjects. In addition, auditory hallucinations were examined through the information processing flow of the brain neural network, including the frontal regions. One hundred unaveraged magnetoencephalography signals during the incongruent stimulus responses were analyzed with a time window of 200 ms in steps of 50 ms. In the 25-60-Hz band, cortical regions that showed significant current source density changes were examined for each time window. The three groups showed significantly decreased current source density, corresponding to neural activation, with temporal overlap along the fundamental cognitive information processing flow: sensory input system, executive control system, motor output system. Transient neural activations in the dorsolateral prefrontal cortex were bilateral with left-side dominancy for normal controls, left-lateralized for nonhallucinators and right-lateralized for hallucinators. Our results suggest that the dysfunction in the left dorsolateral prefrontal cortex was related to auditory hallucinations, while the information processing flow was unaffected in the schizophrenic subjects in the Stroop task.

Adolescent↗
PubMed2003

Spatial laser-wing suppression in saturated laser-induced fluorescence without spatial selection.

Spatial wings of laser beams are of great concern in saturated laser-induced fluorescence. Their contribution to fluorescence is customarily avoided by resolution of laser peaks in the interaction volume. An alternative and versatile approach is formulated, based on the derivative of fluorescence with respect to laser intensity. It turns out that wing-free data are possible, although they are obtained from wing-dependent fluorescence. The advantages of this approach are exact centerline detection and simplicity of the experimental setup and procedure.

Journal Article↗
PubMed2004

Spatial distribution patterns of malaria vectors and sample size determination in spatially heterogeneous environments: a case study in the west Kenyan highland.

The current study examined temporal and spatial distribution patterns of anopheline malaria vectors in a highland site and determined the number of houses to be sampled to achieve the targeted precision level. Adult mosquito sampling was conducted seasonally in May and August 2002 in a 3 by 3-km2 area, and in November 2002 and February 2003 in an expanded 4 by 4-km2 area in Kakamega District, western Kenya. Anopheles gambiae Giles was the predominant malaria vector species, constituting 84.6% of the specimens, whereas Anopheles funestus Giles constituted 15.4% of the vector populations. An. gambiae abundance increased by six- to eight-fold in the long rainy season over the dry seasons, but An. funestus abundance peaked 3 mo after the long rainy season. For both species, the coefficient of variation was larger than 1, suggesting that the distribution of mosquito adults was aggregated. Mosquito clustering occurred in houses <400 m from a valley bottom. The negative binomial distribution was accepted in one sample period (August 2002) for An. gambiae and in two sampling periods (May and August 2002) for An. funestus. Taylor's power law analyses indicated that An. gambiae distribution was more aggregated in the wet seasons than in the dry seasons, whereas the degree of aggregation of An. funestus was similar in all four seasons. The minimum number of houses required to estimate anopheline female abundance within the commonly acceptable precision level (0.2) should be 17 houses per km2 for An. gambiae and 42 houses per km2 for An. funestus. The potential factors causing aggregated anopheline mosquito distribution are discussed.

Animals↗
PubMed2002

Negative information: both presence and absence of spatial pattern elements guide rats' spatial choices.

Rats learn the spatial pattern in which hidden caches of food are located. Once the pattern is learned, finding one or more baited locations provides (positive) information about the remaining baited locations. In the present experiment, we examined whether negative information (the absence of food in a location) would also be used in locating the remaining baited locations. Rats were tested in an apparatus containing a matrix of vertical poles, on top of which food could be hidden. At the beginning of the trial, the location of the baited poles was unpredictable, but the poles were always arranged in a linear pattern. The rats learned the pattern and used both positive and negative information in locating baited poles.

Animals↗
PubMed1985

Spatial magnitude of the normal QRS-complex in the electrocardiogram of rabbits. Velocity and acceleration of the spatial magnitude.

The article describes the curves of the spatial magnitude (SM) of the normal QRS-complex in 52 rabbits, as well as of the velocity and acceleration of SM as a function of time. The X-, Y- and Z-recordings after McFee and Parungao are subjected to analogue-to-digital conversion and computer-calculation. The SM-curve consists of two and less frequently of three peaks, the third peak having the greatest amplitude and the first peak--the smallest. The three peaks are discovered at 16, 41 and 64 per cent, respectively, of the duration of the QRS-complex. The results are discussed in relation to data about other mammals and humans. The characteristic points in the curves of the recorded parameters are compared.

Animals↗