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At least 487 records · Page 27Linked to original sources
PubMed1999

Respective roles of scatter, attenuation, depth-dependent collimator response and finite spatial resolution in cardiac single-photon emission tomography quantitation: a Monte Carlo study.

The purpose of this study was to investigate the relative influence of scatter, attenuation, depth-dependent collimator response and finite spatial resolution upon the image characteristics in cardiac single-photon emission tomography (SPET). An acquisition of an anthropomorphic cardiac phantom was performed together with corresponding SPET Monte Carlo simulations. The cardiac phantom and the Monte Carlo simulations were designed so that the effect of scatter, attenuation, depth-dependent collimator response and finite spatial resolution could be studied individually and in combination. The impact of each physical effect and of combinations of effects was studied in terms of absolute and relative quantitative accuracy, spatial resolution and signal-to-noise ratio (SNR) in the resulting images. No corrections for these effects were assessed. Results obtained from Monte Carlo simulations and real acquisitions were in excellent agreement. Attenuation introduced about 90% activity underestimation in a 10-mm-thick left ventricle wall while finite spatial resolution alone introduced about 30% activity underestimation. Scatter had a negligible impact on quantitative accuracy in the recontructed slices when attenuation was present. Neither bull's eye map homogeneity nor contrast between a hot and a cold region were affected by depth-dependent collimator response or finite spatial resolution. Bull's eye map homogeneity was severely affected by attenuation but not by scatter. Attenuation and scatter reduced contrast by about 20% each. Both attenuation and scatter increased the full-width at half-maximum (FWHM) characterizing the spatial resolution of the imaging system by approximately 1 mm each but the main effect responsible for the observed 11-mm FWHM spatial resolution was the depth-dependent collimator response. SNR was reduced by a factor of approximately 2.5 because of attenuation, while scattered counts increased SNR by approximately 10%. In conclusion, the quantification of the relative influence of the different physical effects showed that attenuation is definitely the major phenomenon affecting cardiac SPET imaging accuracy, but that finite spatial resolution, scatter and depth-dependent collimator response also contribute significantly to the errors in absolute and relative quantitation and to the poor spatial resolution.

Computer Simulation↗
PubMed2005

Scaling up from local competition to regional coexistence across two scales of spatial heterogeneity: insect larvae in the fruits of Apeiba membranacea.

Species that live in patchy and ephemeral habitats can compete strongly for resources within patches at a small scale. The ramifications of these interactions for population dynamics and coexistence at regional scales will depend on the intraspecific and interspecific distributions of individuals among patches. Spatial heterogeneity due to independent aggregation of competitors among patchy habitats is an important mechanism maintaining species diversity. I describe regional patterns of aggregation for four species of insect larvae in the fruits of Apeiba membranacea, a Neotropical rainforest tree. This aggregation results from variation in densities at a small scale (among the fruits under a single tree), compounded by significant variation among trees in both mean densities and degrees of aggregation. Both the degrees of aggregation and mean densities are statistically independent within and across species at both spatial scales. I evaluate the regional consequences of these spatial patterns by using maximum likelihood methods to parameterize a model that includes both explicit measures of the strength of competition and spatial variation at both within- and among-tree spatial scales. Despite strong competitive interactions among these species, during 2 years the observed spatial variation at both scales combined was sufficient to explain the coexistence of these species, although other coexistence mechanisms may also operate simultaneously. The observed spatial variation at small spatial scales may not be sufficient for coexistence, indicating the importance of considering multiple sources of spatial heterogeneity when scaling up from experiments that investigate local interactions to regional patterns of coexistence.

Animals↗
PubMed2006

Bumblebees experience landscapes at different spatial scales: possible implications for coexistence.

Coexistence in bumblebee communities has largely been investigated at local spatial scales. However, local resource partitioning does not fully explain the species diversity of bumblebee communities. Theoretical studies provide new evidence that partitioning of space can promote species coexistence, when species interact with their environment at different spatial scales. If bumblebee species possess specific foraging ranges, different spatial resource utilisation patterns might operate as an additional mechanism of coexistence in bumblebee communities. We investigated the effects of the landscape-wide availability of different resources (mass flowering crops and semi-natural habitats) on the local densities of four bumblebee species at 12 spatial scales (landscape sectors with 250-3,000 m radius) to indirectly identify the spatial scales at which the bumblebees perceive their environment. The densities of all bumblebee species were enhanced in landscapes with high proportions of mass flowering crops (mainly oilseed rape). We found the strongest effects for Bombus terrestris agg. and Bombus lapidarius at large spatial scales, implying foraging distances of 3,000 and 2,750 m, respectively. The densities of Bombus pascuorum were most strongly influenced at a medium spatial scale (1,000 m), and of Bombus pratorum (with marginal significance) at a small spatial scale (250 m). The estimated foraging ranges tended to be related to body and colony sizes, indicating that larger species travel over larger distances than smaller species, presumably enabling them to build up larger colonies through a better exploitation of food resources. We conclude that coexistence in bumblebee communities could potentially be mediated by species-specific differences in the spatial resource utilisation patterns, which should be considered in conservation schemes.

Animals↗
PubMed1996

Spatial learning alters hippocampal calcium/calmodulin-dependent protein kinase II activity in rats.

This study investigated the role of hippocampal CaM-kinase II (calcium/calmodulin-dependent protein kinase II) in spatial learning. In Experiment I, three groups of rats received 1, 2 or 5 days of training on a spatial task in the Morris water maze with a hidden platform, while a control group was trained on a nonspatial task with a visible platform. The acquisition rate in the spatial task was slower than that in the nonspatial task. However, rats receiving 5 days of spatial training had the highest Ca(2+)-independent activity of CaM-kinase II compared with the controls receiving nonspatial training and rats having 1 or 2 days of spatial training. Furthermore, the level of hippocampal Ca2+-independent CaM-kinase II activity was correlated with the final performance on the spatial task. In Experiment II, rats received intra-hippocampal injections of a specific CaM-kinase II inhibitor-KN-62-before each training session. In comparison with the vehicle-injected controls, pretraining injection of KN-62 retarded acquisition in the spatial task but had no effect on the nonspatial task. These results, taken together, indicated that the activation of CaM-kinase II in the hippocampus is not only correlated to the degree of spatial training on the Morris water maze, but may also underlie the neural mechanism subserving spatial memory.

Animals↗
PubMed1984

The contrast dependence of spatial frequency channel interactions.

Interactions between spatial frequency channels were tested in two ways: we measured the discriminability by the visual system between two compound spatial-frequency gratings, of components with spatial frequencies in the ratio 1:3, when the difference between the two gratings was an increase (or decrease) in contrast of both components of the compound grating (contrast discrimination), or when the difference between the two gratings was an increase in contrast of one component and a decrease in contrast of the other component (pattern discrimination). We found that the contrast: pattern discriminability ratio differs significantly from unity in most conditions. Furthermore, this ratio is generally greater when the components of the grating are in peaks-add relative phase than when in peaks-subtract phase. On the other hand, the ratio was close to unity for grating components of spatial frequencies 1 and 9 cycles/deg. These results suggest that the human visual system contains spatial frequency channels with bandwidths of between 1.6 and 3.2 octaves and that these relatively broad channels have peaks-add spatial profiles. The channels appear linear at intermediate contrasts and spatial frequencies, but super-linear at high spatial frequencies and contrasts. Contrast and spatial frequency may be interchangeable for the determination of the linearity of the visual system.

Discrimination, Psychological↗
PubMed1985

Spatial frequency sweep VEP: visual acuity during the first year of life.

The grating acuity of 197 infants from 1 week to 53 weeks of age was measured using the visual evoked potential (VEP) in response to counterphase grating stimulation. The gratings were presented as a 10 sec spatial frequency sweep which spanned the acuity limit. The amplitude and phase of the second harmonic response were extracted by discrete Fourier analysis. The VEP amplitude versus spatial frequency function showed narrow spatial frequency tuning with amplitude peaks at one or more spatial frequencies. The phase of the response at medium to high spatial frequencies was generally constant at a spatial frequency peak, followed by a progressive phase lag with increasing spatial frequency. Grating acuity was estimated by linear extrapolation to zero microvolts of the highest spatial frequency peak in the VEP amplitude versus spatial frequency function. This visual acuity estimate increased from a mean of 4.5 c/deg during the first month to about 20 c/deg at 8-13 months of age. The VEP acuities at 1 month are a factor of three to five higher than previously reported for pattern reversal or pattern appearance stimuli. By 8 months VEP grating resolution was not reliably different from adult levels in the same apparatus.

Adult↗
PubMed1993

Neural recruitment explains "Weber's law" of spatial position.

We ask whether the well known Weber's law between spatial localization and element separation for high contrast, spectrally broad-band stimuli is a consequence of the organization of the early visual filters, or a fundamental constraint on the computation of spatial position by more central mechanisms. We address this question by identifying the individual contributions of mechanisms tuned to different ranges of spatial frequencies and contrast. We measure spatial-alignment and bisection error as a function of element separation at each of a number of spatial scales, using spectrally narrow-band stimuli of fixed supra-threshold contrast. We show that stimuli which minimize the extent of neural recruitment across different spatial channels before the site of extraction of the local contrast energy (and to a lesser extent across different contrast channels) do not exhibit Weber's law for either alignment or bisection. We present evidence that Weber's law for localization with increasing separation, found for stimuli of high contrast and broad-band spatial frequency content, is a consequence of the successive disengagement of unitary neural mechanisms, each of which has different spatial and contrast properties, and none of which individually exhibits Weber's law for spatial position.

Contrast Sensitivity↗
PubMed1994

Spatial scale shifts in amblyopia.

We used a masking paradigm to uncover the properties of the mechanisms engaged by the amblyopic visual system for vernier acuity and line detection. Line vernier and line detection thresholds were measured in the presence of one-dimensional noise masks varying in orientation, spatial frequency content or contrast. Our results reveal that in both normal and amblyopic eyes, there is a bimodal orientation tuning function for vernier acuity, i.e. vernier acuity is most strongly masked by mask orientations approx. +/- 10 deg on either side of the target lines. In contrast, in both normal and amblyopic eyes, line detection is most strongly masked when the mask and line target have the same orientation. In the normal fovea, the spatial frequency tuning is bandpass, with a peak spatial frequency of about 10 c/deg. In the amblyopic eyes, the spatial tuning is similar in specificity; however the peak is shifted to lower spatial frequencies, suggesting a shift in the scale of spatial processing of line stimuli. For all of the amblyopic eyes, the increased line detection thresholds are approximately proportional to the shift in spatial scale. In anisometropic amblyopes, the (unmasked) vernier threshold is elevated in proportion to the shift in spatial scale; however in some amblyopes with constant strabismus the shift in spatial scale is not sufficient to account for the degraded vernier acuity. The "extra" increase in vernier thresholds associated with strabismus may be a consequence of a high degree of positional uncertainty which adds noise at a stage following the combination of filter responses.

Adult↗
PubMed1993

Effects of intracranial infusions of chlordiazepoxide on spatial learning in the Morris water maze. II. Neuropharmacological specificity.

In the preceding paper it was found that infusions of chlordiazepoxide (CDP) into the medial septal region, but not several other regions possessing a high density of benzodiazepine receptors, impaired spatial learning, but not cue learning or swim speed, in the Morris water maze. The present investigation sought to further characterize the neuropharmacological profile of this effect. Initially, it was reconfirmed that systemically administered CDP impaired spatial learning, but not cue learning or swim speed, in the water maze. Additionally, it was found that systemically administered scopolamine, a muscarinic antagonist, impaired both spatial and cue learning, but not swim speed, confirming the detrimental effects of cholinergic hypofunction on maze learning. In new rats, a dose-response assessment revealed that 60 and 30 nmol, but not 10 nmol, CDP infused into the medial septum impaired spatial learning, but not cue learning or swim speed. On the following day, rats from each dose group, now undrugged, acquired a reversed platform location at control levels, suggesting that the previously observed impairment was not due to a neurotoxic effect. Additionally, it was found that systemically administered flumazenil (10 mg/kg) blocked the spatial learning deficit produced by the 60 nmol dose of CDP infused into the medial septum. However, intraseptal infusions of flumazenil (10, 20, or 30 nmol) failed to attenuate the spatial learning deficit produced by systemically administered CDP. Finally, systemically administered tetrahydroaminoacridine (1 or 3 mg/kg), an acetylcholinesterase inhibitor, failed to attenuate the spatial learning deficit produced by intraseptal CDP (60 nmol). Together these results implicate benzodiazepine receptors in the medial septum in the amnesic actions of CDP but suggest that additional sites also mediate this action. The present results fail to support the idea that the spatial learning deficit produced by intraseptal infusions of CDP is due to a suppression of septo-hippocampal cholinergic activity and it is proposed that CDP impairs spatial learning by exacerbating hippocampal inhibition by inhibiting septo-hippocampal GABAergic projection neurons.

Animals↗
PubMed1991

Spatial grouping activity in young children with congenital right or left hemisphere brain injury.

Spatial grouping abilities were examined in 20 preschool-aged children with right or left hemisphere congenital focal brain injury, and a group of age-matched normal control children. Children were presented with a series of spontaneous grouping tasks in which they were given small sets of blocks and asked to play with them. Although the children with focal brain injury played as actively with the blocks as normal children, the constructions they produced differed systematically. Across eight measures of spatial grouping both children with right and left hemisphere injury were delayed compared to normal children. In addition, the behavioral profiles for the two groups of children with focal brain injury were qualitatively different. Data for the children with RH injury suggested difficulty organizing objects into coherent spatial groupings, while data from the children with LH injury suggested difficulty with local relations within the spatial arrays. These findings are consistent with data reported for adults on spatial construction tasks. Developmental trajectories in the 3- to 4-year age period suggest, further, that the spatial integrative deficits observed in the children with RH injury are persistent. When the children began to produce spatial constructions using complex grouping procedures, those constructions were heaps or disordered clusters. In contrast, when children with LH injury began to use complex procedures, they generated the types of constructions usually associated with those procedures in normal children, e.g., arches, enclosures, and symmetries. These data were found within a cross-sectional study of 20 children and confirmed in a series of six longitudinal case study reports of three children with RH and three with LH injury. The data confirm our previous reports of spatial integrative deficit associated with early RH injury and present the first indication of spatial encoding deficits in children with LH injury.

Age Factors↗
PubMed1995

Glucocorticoids, hippocampal corticosteroid receptor gene expression and antidepressant treatment: relationship with spatial learning in young and aged rats.

The emergence of cognitive deficits in a subgroup of aged rats is associated with increased hypothalamic-pituitary-adrenal axis activity, decreased hippocampal mineralocorticoid and/or glucocorticoid receptor gene expression and neuronal loss. Short-term treatment with antidepressant drugs in young rats increases hippocampal corticosteroid receptor gene expression. In this study, the effects of chronic antidepressant administration on hippocampal mineralocorticoid and glucocorticoid receptor gene expression and spatial memory in young and aged rats were investigated. Young (eight months) and old (22 +/- 1 months) Lister-hooded rats were ranked according to watermaze performance. Matched pairs of rats were treated with amitriptyline (10 mg/kg) or saline daily for nine weeks, then reassessed in the watermaze. Amitriptyline significantly improved spatial memory in the young rats (33% increase in transfer test time) and increased hippocampal mineralocorticoid, but not glucocorticoid receptor messenger RNA expression. By contrast, in aged rats, amitriptyline had no effect on spatial memory or hippocampal corticosteroid receptor gene expression, either in cognitively unimpaired or cognitively-impaired animals. In aged rats, basal plasma corticosterone levels, which were significantly higher than in young animals, correlated negatively with spatial memory, while hippocampal glucocorticoid receptor mRNA expression correlated negatively with plasma corticosterone levels and positively with spatial memory. Amitriptyline had no significant effect on basal morning plasma corticosterone levels in either young or aged rats, but significantly decreased evening corticosterone levels in aged rats. Our data support the notion that corticosterone exerts a concentration-dependent biphasic influence, via selective activation of hippocampal mineralocorticoid and glucocorticoid receptor, on spatial memory. Amitriptyline improves spatial memory in young rats and increases hippocampal mineralocorticoid receptor gene expression. The lack of amitriptyline effect on spatial memory in aged rats may reflect decreased plasticity of both the synaptic processes underlying spatial memory and the regulation of hippocampal mineralocorticoid/glucocorticoid receptor expression, with mineralocorticoid receptors fully occupied due to elevated basal plasma corticosterone levels (in part a consequence of inadequate glucocorticoid receptor function).

Aging↗
PubMed1996

A curvilinear relationship between testosterone and spatial cognition in humans: possible influence of hand preference.

The nature of the relationship, if any, between performance on visuo-spatial tests in humans and circulating testosterone (T) concentrations remains controversial. We investigated possible relationships between salivary T and cortisol (C) concentrations and performance on visuo-spatial and verbal cognitive tests in a sample of healthy young adults. Among right-handers, salivary T was found to be negatively correlated with spatial performance in males, but was positively correlated with a measure of spatial visualization in females. This pattern was not evident in left-handers. Across the entire observed range of T, the relationship between spatial cognition and T was best described by an inverted quadratic function in right-handers, but not in left-handers. A significant difference in spatial accuracy was seen among right-handers tested in early vs. late morning testing sessions, in accordance with the expected diurnal change in circulating T. No significant relationships between salivary C and visuo-spatial performance were found. These results are consistent with prior literature suggesting a curvilinear relationship between spatial performance and circulating T concentrations, with intermediate levels of T being associated with better spatial functioning, but raise the possibility that hand preference may be one factor that moderates the observed relationship.

Adult↗
PubMed2006

Spatial and temporal resolution effects on dynamic contrast-enhanced magnetic resonance mammography.

We tested the hypothesis that partial volume effects due to poor in-plane resolution and/or low temporal resolution used in clinical dynamic contrast-enhanced magnetic resonance imaging results in erroneous diagnostic information based on inaccurate estimates of tumor contrast agent extravasation and tested whether reduced encoding techniques can correct for dynamic data volume averaging. Image spatial resolution was reduced from 469 x 469 microm2 to those reported below by selecting a subset of k-space data. We then compared the top five K(trans)/V(T) "hot spots" obtained from the original data set, 469 x 469-microm in-plane spatial resolution and an 18-s temporal resolution processed by fast Fourier transform (FFT), with values obtained from data sets having in-plane spatial resolutions of 938 x 938, 1875 x 1875 and 2500 x 2500 microm2 and a temporal resolution of 18 s, or data sets with temporal resolutions of 36, 54 and 72 and a spatial resolution of 469 x 469 microm2, and found them to statistically differ from the parent data sets. We then tested four different post processing methods for improving the spatial resolution without sacrificing temporal resolution: zero-filled FFT, keyhole, reduced-encoding imaging by generalized-series reconstruction (RIGR) and two-reference RIGR (TRIGR). The top five values of K(trans)/V(T) obtained from data sets, the in-plane spatial resolutions of which were improved to 469 x 469 microm2 by zero-filling FFT, Keyhole and RIGR, statistically differed from those obtained from the original 469 x 469 microm2 FFT parent image data set. Only the 938 x 938 and 1875 x 1875 microm2 data sets reconstructed to 469 x 469 microm2 with TRIGR reconstruction method yielded values of the top five K(trans)/V(T) hot spots statistically the same as the original parent data set, 469 x 469 microm2 in-plane spatial and 18-s temporal-resolution FFT. That is, partial volume effects from data sets of different in-plane spatial resolution resulted in statistically different values of the top five K(trans)/V(T) hot spots relative to a high spatial and temporal resolution data set, and TRIGR reconstruction of these low resolution data sets to high resolution images provided statistically similar values with a savings in temporal resolution of 2 to 4 times.

Animals↗
PubMed2007

Space, time and learning in the hippocampus: how fine spatial and temporal scales are expanded into population codes for behavioral control.

The hippocampus participates in multiple functions, including spatial navigation, adaptive timing and declarative (notably, episodic) memory. How does it carry out these particular functions? The present article proposes that hippocampal spatial and temporal processing are carried out by parallel circuits within entorhinal cortex, dentate gyrus and CA3 that are variations of the same circuit design. In particular, interactions between these brain regions transform fine spatial and temporal scales into population codes that are capable of representing the much larger spatial and temporal scales that are needed to control adaptive behaviors. Previous models of adaptively timed learning propose how a spectrum of cells tuned to brief but different delays are combined and modulated by learning to create a population code for controlling goal-oriented behaviors that span hundreds of milliseconds or even seconds. Here it is proposed how projections from entorhinal grid cells can undergo a similar learning process to create hippocampal place cells that can cover a space of many meters that are needed to control navigational behaviors. The suggested homology between spatial and temporal processing may clarify how spatial and temporal information may be integrated into an episodic memory. The model proposes how a path integration process activates a spatial map of grid cells. Path integration has a limited spatial capacity, and must be reset periodically, leading to the observed grid cell periodicity. Integration-to-map transformations have been proposed to exist in other brain systems. These include cortical mechanisms for numerical representation in the parietal cortex. As in the grid-to-place cell spatial expansion, the analog representation of number is extended by additional mechanisms to represent much larger numbers. The model also suggests how visual landmarks may influence grid cell activities via feedback projections from hippocampal place cells to the entorhinal cortex.

Animals↗
PubMed2004

The neural correlates of spatial language in English and American Sign Language: a PET study with hearing bilinguals.

Rather than specifying spatial relations with a closed-class set of prepositions, American Sign Language (ASL) encodes spatial relations using space itself via classifier constructions. In these constructions, handshape morphemes specify object type, and the position of the hands in signing space schematically represents the spatial relation between objects. A [15O]water PET study was conducted to investigate the neural regions engaged during the production of English prepositions and ASL locative classifier constructions in hearing subjects with deaf parents (ASL-English bilinguals). Ten subjects viewed line drawings depicting a spatial relation between two objects and were asked to produce either an ASL locative classifier construction or an English preposition that described the spatial relation. The comparison task was to name the figure object (colored red) in either ASL or in English. Describing spatial relations in either ASL or English engaged parietal cortex bilaterally. However, an interaction analysis revealed that right superior parietal cortex was engaged to a greater extent for ASL than for English. We propose that right parietal cortex is involved in the visual-motoric transformation required for ASL. The production of both English prepositions and ASL nouns engaged Broca's area to a greater extent than ASL classifier constructions. We suggest that Broca's area is not engaged because these constructions do not involve retrieval of the name of an object or the name of a spatial relation. Finally, under the same task conditions, only left parietal activation was observed for monolingual English speakers producing spatial prepositions (H. Damasio et al., 2001, NeuroImage, 13). We conclude that the right hemisphere activation observed for ASL-English bilinguals was due to their life-long experience with spatial language in ASL.

Adult↗
PubMed2006

An electrophysiological study on the interaction between emotional content and spatial frequency of visual stimuli.

Previous studies suggest that the magnocellular pathway, a visual processing system that rapidly provides low spatial frequency information to fast-responding structures such as the amygdala, is more involved in the processing of emotional facial expressions than the parvocellular pathway (which conveys all spatial frequencies). The present experiment explored the spatio-temporal characteristics of the spatial frequency modulation of affect-related neural processing, as well as its generalizability to non-facial stimuli. To that aim, the event-related potentials (ERPs) elicited by low-pass filtered (i.e., high spatial frequencies are eliminated) and intact non-facial emotional images were recorded from 31 participants using a 60-electrode array. The earliest significant effect of spatial frequency was observed at 135 ms from stimulus onset: N135 component of the ERPs. In line with previous studies, the origin of N135 was localized at secondary visual areas for low-pass filtered stimuli and at primary areas for intact stimuli. Importantly, this component showed an interaction between spatial frequency and emotional content: within low-pass filtered pictures, negative stimuli elicited the highest N135 amplitudes. By contrast, within intact stimuli, neutral pictures were those eliciting the highest amplitudes. These results suggest that high spatial frequencies are not essential for the initial affect-related processing of visual stimuli, which would mainly rely on low spatial frequency visual information. According to present data, high spatial frequencies would come into play later on.

Adult↗
PubMed2004

The influence of motion-defined form on the perception of spatially-defined form.

It is well established that the visual system is sensitive to the global structure--or "form"--of objects defined exclusively by spatial or motion cues, but it remains unclear how form perception combines spatial and motion cues if these are presented concurrently. In the present study, we introduce a novel class of stimuli where spatial-form and motion-form can be superimposed and manipulated independently. In both the spatial and motion domains, global structure consisted of radial-frequency (RF) contours defined by a virtual circle of Gabor elements whose positions and/or drift speeds were sinusoidally modulated at a specified frequency of polar angle. The first two experiments revealed that observers encode the global structure of spatial-RF and motion-RF contours presented in isolation. In a third experiment, observers detected a spatial-RF modulation superimposed on a motion-RF pedestal of identical radial frequency: results showed little facilitation at low pedestal amplitudes but significant masking at higher pedestal amplitudes, especially if the RF modulations of test and pedestal were in anti-phase. Additional experiments demonstrated that masking of the spatial-RF test is abolished if the global structure of the motion-RF pedestal is altered or destroyed while local motion cues are preserved. We argue these results cannot be explained by local neural interactions between spatial and motion cues and propose instead that data reflect higher-level interactions between separate visual pathways encoding spatial-form and motion-form.

Cues↗
PubMed2002

Turning the tables: language and spatial reasoning.

This paper investigates possible influences of the lexical resources of individual languages on the spatial organization and reasoning styles of their users. That there are such powerful and pervasive influences of language on thought is the thesis of the Whorf-Sapir linguistic relativity hypothesis which, after a lengthy period in intellectual limbo, has recently returned to prominence in the anthropological, linguistic, and psycholinguistic literatures. Our point of departure is an influential group of cross-linguistic studies that appear to show that spatial reasoning is strongly affected by the spatial lexicon in everyday use in a community (e.g. Brown, P., & Levinson, S. C. (1993). Linguistic and nonlinguistic coding of spatial arrays: explorations in Mayan cognition (Working Paper No. 24). Nijmegen: Cognitive Anthropology Research Group, Max Planck Institute for Psycholinguistics; Cognitive Linguistics 6 (1995) 33). Specifically, certain groups customarily use an externally referenced spatial-coordinate system to refer to nearby directions and positions ("to the north") whereas English speakers usually employ a viewer-perspective system ("to the left"). Prior findings and interpretations have been to the effect that users of these two types of spatial system solve rotation problems in different ways, reasoning strategies imposed by habitual use of the language-particular lexicons themselves. The present studies reproduce these different problem-solving strategies in speakers of a single language (English) by manipulating landmark cues, suggesting that language itself may not be the key causal factor in choice of spatial perspective. Prior evidence on rotation problem solution from infants (e.g. Acredolo, L.P. (1979). Laboratory versus home: the effect of environment on the 9-month-old infant's choice of spatial reference system. Developmental Psychology, 15 (6), 666-667) and from laboratory animals (e.g. Restle, F. (1975). Discrimination of cues in mazes: a resolution of the place-vs.-response question. Psychological Review, 64, 217-228) suggests a unified interpretation of the findings: creatures approach spatial problems differently depending on the availability and suitability of local landmark cues. The results are discussed in terms of the current debate on the relation of language to thought, with particular emphasis on the question of why different cultural communities favor different perspectives in talking about space.

Adult↗