Role In Spatial Processing Research Articles

Comparison of head direction cell firing characteristics across thalamo-parahippocampal circuitry.

Head direction (HD) cells, which fire persistently when an animal's head is pointed in a particular direction, are widely thought to underlie an animal's sense of spatial orientation and have been identified in several limbic brain regions. Robust HD cell firing is observed throughout the thalamo-parahippocampal system, although recent studies report that parahippocampal HD cells exhibit distinct firing properties, including conjunctive aspects with other spatial parameters, which suggest they play a specialized role in spatial processing. Few studies, however, have quantified these apparent differences. Here, we performed a comparative assessment of HD cell firing characteristics across the anterior dorsal thalamus (ADN), postsubiculum (PoS), parasubiculum (PaS), medial entorhinal (MEC), and postrhinal (POR) cortices. We report that HD cells with a high degree of directional specificity were observed in all five brain regions, but ADN HD cells display greater sharpness and stability in their preferred directions, and greater anticipation of future headings compared to parahippocampal regions. Additional analysis indicated that POR HD cells were more coarsely modulated by other spatial parameters compared to PoS, PaS, and MEC. Finally, our analyses indicated that the sharpness of HD tuning decreased as a function of laminar position and conjunctive coding within the PoS, PaS, and MEC, with cells in the superficial layers along with conjunctive firing properties showing less robust directional tuning. The results are discussed in relation to theories of functional organization of HD cell tuning in thalamo-parahippocampal circuitry.

Cortical volume alteration in the superior parietal region mediates the relationship between childhood abuse and PTSD avoidance symptoms: A complementary multimodal neuroimaging study

BackgroundAdverse childhood experiences (ACE), which can be separated into abuse and neglect, contribute to the development of post-traumatic stress symptoms (PTSS). However, which brain structures are mainly affected by ACE as well as the mediating role these brain structures play in ACE and PTSS relationship are still being investigated. The current study tested the effect of ACE on brain structure and investigated the latter's mediating role in ACE-PTSS relationship. MethodsA total of 78 adults with self-reported ACE were included in this study. Participants completed the childhood trauma questionnaire (CTQ) and a Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5) to ascertain ACE history and PTSS, respectively. T1w images and diffusion MRI scans were then acquired to assess cortical morphometry and white matter (WM) integrity in fibre tracts connecting key areas where ACE-related cortical volume alterations were observed. ResultsThe combined effect of ACE was negatively associated with total grey matter volume and local cortical area in the right superior parietal region (rSP). Childhood abuse was negatively related to right superior parietal volume after controlling for neglect and overall psychological burden. The right superior parietal volume significantly mediated the relationship between childhood abuse and avoidance-related PTSS. Post-hoc analyses showed that the indirect relation was subsequently moderated by dissociative symptoms. Lastly, a complementary examination of the WM tracts connected to abuse-associated cortical GM regions shows that abuse was negatively related to the normalised fibre density of WM tracts connected to the right superior parietal region. ConclusionWe provide multimodal structural evidence that ACE in the first years of life is related to alterations in the right superior brain region, which plays a crucial role in spatial processing and attentional functioning. Additionally, we highlight that the cortical volume alteration in this region may play a role in explaining the relationship between childhood abuse and avoidance symptoms.

Retrosplenial and subicular inputs converge on superficially projecting layer V neurons of medial entorhinal cortex

The medial entorhinal cortex (MEC) plays a pivotal role in spatial processing together with hippocampal formation. The retrosplenial cortex (RSC) is also implicated in this process, and it is thus relevant to understand how these structures interact. This requires precise knowledge of their connectivity. Projections from neurons in RSC synapse onto principal neurons in layer V of MEC and some of these neurons send axons into superficial layers of MEC. Layer V of MEC is also the main target for hippocampal efferents from the subiculum and CA1 field. The aim of this study was to assess whether the population of cells targeted by RSC projections also receives input from the hippocampal formation and to compare the distribution of synaptic contacts on target dendrites. We labeled the cells in layer V of MEC by injecting a retrograde tracer into superficial layers. At the same time, we labeled RSC and subicular projections with different anterograde tracers. 3D-reconstruction of the labeled cells and axons revealed likely synaptic contacts between presynaptic boutons of both origins and postsynaptic MEC layer V basal dendrites. Moreover, these contacts overlapped on the same dendritic segments without targeting specific domains. Our results support the notion that MEC layer V neurons that project to the superficial layers receive convergent input from both RSC and subiculum. These data thus suggest that convergent subicular and RSC information contributes to the signal that neurons in superficial layers of EC send to the hippocampal formation.

Optogenetic control of receptors reveals distinct roles for actin- and Cdc42-dependent negative signals in chemotactic signal processing

During chemotaxis, neutrophils use cell surface G Protein Coupled Receptors to detect chemoattractant gradients. The downstream signaling system is wired with multiple feedback loops that amplify weak inputs and promote spatial separation of cell front and rear activities. Positive feedback could promote rapid signal spreading, yet information from the receptors is transmitted with high spatial fidelity, enabling detection of small differences in chemoattractant concentration across the cell. How the signal transduction network achieves signal amplification while preserving spatial information remains unclear. The GTPase Cdc42 is a cell-front polarity coordinator that is predictive of cell turning, suggesting an important role in spatial processing. Here we directly measure information flow from receptors to Cdc42 by pairing zebrafish parapinopsina, an optogenetic G Protein Coupled Receptor with reversible ON/OFF control, with a spectrally compatible red/far red Cdc42 Fluorescence Resonance Energy Transfer biosensor. Using this toolkit, we show that positive and negative signals downstream of G proteins shape a rapid, dose-dependent Cdc42 response. Furthermore, F-actin and Cdc42 itself provide two distinct negative signals that limit the duration and spatial spread of Cdc42 activation, maintaining output signals local to the originating receptors.

Vascular cognitive impairment due to dilated perivascular spaces in putamen: Connections with the ventrolateral prefrontal cortex and neurological deficits

AbstractBackgroundAnatomical studies in animals have described multiple striatal circuits and suggested that sub‐components of the striatum project to distinct cortical areas. Researchers that reconstructed tracts of the left and right putamen have shown ipsilateral projections to the primary motor area, primary somatosensory area, supplementary motor area, premotor area, cerebellum, thalamus and prefrontal cortex (specifically to the ventrolateral prefrontal cortex). The ventrolateral prefrontal cortex appears to have a specific role in spatial processing and memory retrieval.MethodCase report and analyses of MR Images (T1, T2 and Flair) of a patient presenting with vascular cognitive impairment due to dilated perivascular spaces in putamen bilaterally.ResultMale patient, 81 years‐old, right‐handed, with four years of formal education and high cerebrovascular risk. His cognitive complaints began twelve years ago, and worsened in the last two years (losing personal belongings inside his own house, sometimes forgetting names of well‐known persons, with word finding difficulties). He denied impairment in activities of daily living, was able to organize his home budget, take his medications and go to the market alone. Now, he is physically and intellectually active (walking, reading newspapers, and talking about Philosophy), and still drives cars. His CDR score is 0.5, and his MMSE score is 29 (with 3 points in evoked memory). Word List Memory Task (Immediate Recall):4/5/8 (intrusion of "vessel" in the first two lists); Evocation:6 (intrusion of "vessel"); Recognition:10; Verbal Fluency (Animals):20; Verbal Fluency (Fruits):9. MR (10/15/2018): mild supratentorial microangiopathy; encephalomalacia/gliosis in the vermis and the left cerebellar hemisphere; Fasekas = 1 / Scheltens = 1 (bilaterally); bilateral supratentorial dilated perivascular spaces, particularly in the putamen.ConclusionOur patient does not have dementia, regardless of more than ten years of cognitive impairment. Bilateral dilated perivascular spaces in the putamen may cause deficits in memory retrieval and spatial processing. Neuropsychological evaluations must consider specific areas of brain injury. Our patient has impaired memory retrieval (with false memories verified by constant intrusions in the Word List Memory Task), and the high occurrence of losing personal belongings inside his house can be due to difficulties in spatial processing (mental map of positions of items in space).

Arctic chironomids of the northwest North Atlantic reflect environmental and biogeographic gradients

AbstractAimWhile we understand broad climate drivers of insect distributions throughout the Arctic, less is known about the role of spatial processes in determining these relationships. As such, there is a need to understand how spatial controls may influence our interpretations of chironomid environment relationships. Here, we evaluated whether the distribution of chironomids followed spatial gradients, or were primarily controlled by environmental factors.LocationEastern Canadian Arctic, Greenland, Iceland.TaxonNon‐biting midges (Chironomidae).MethodsWe examined chironomid assemblages from 239 lakes in the western North Atlantic Arctic region (specifically from the Arctic Archipelago of Canada, two parts of west Greenland (the southwest and central west) and northwest Iceland). We used a combination of unconstrained ordination (Self Organizing Maps); a simple method with only one data matrix (community data), and constrained ordination (Redundancy Analysis); a canonical ordination with two datasets where we extracted structure of community related to environmental data. These methods allowed us to model chironomid assemblages across a large bioregional dimension and identify specific differences between regions that were defined by common taxa represented across all regions in high frequencies, as well as rare taxa distinctive to each region found in low frequencies. We then evaluated the relative importance of spatial processes versus local environmental factors.ResultsWe find that environmental controls explained the largest amount of variation in chironomid assemblages within each region, and that spatial controls are only significant when crossing between regions. Broad‐scale biogeographic effects on chironomid distributions are reflected by the distinct differences among chironomid assemblages of Iceland, central‐west Greenland, and eastern Canada, defined by the presence of certain common and low‐frequency, rare taxa for each region. Environmental gradients, especially temperature, defined species distributions within each region, whereas spatial processes combine with environmental gradients in determining what mix of species characterizes each broad and geographically distinct island region in our study.Main conclusionsWhile biogeographic context is important for defining interpretations of environmental controls on species distributions, the primary control on distributions within regions is environmental. These influences are fundamentally important for reconstructing past environmental change and better understanding historical distributions of these insect indicators.

Distinct Transcriptomic Cell Types and Neural Circuits of the Subiculum and Prosubiculum along the Dorsal-Ventral Axis

Subicular regions play important roles in spatial processing and many cognitive functions, and these are mainly attributed to the subiculum (Sub) rather than the prosubiculum (PS). Using single-cell RNA sequencing, we identify 27 transcriptomic cell types residing in sub-domains of the Sub and PS. Based on in situ expression of reliable transcriptomic markers, the precise boundaries of the Sub and PS are consistently defined along the dorsoventral axis. Using these borders to evaluate Cre-line specificity and tracer injections, we find bona fide Sub projections topographically to structures important for spatial processing and navigation. In contrast, the PS sends its outputs to widespread brain regions crucial for motivation, emotion, reward, stress, anxiety, and fear. The Sub and PS, respectively, dominate dorsal and ventral subicular regions and receive different afferents. These results reveal two molecularly and anatomically distinct circuits centered in the Sub and PS, respectively, providing a consistent explanation for historical data and a clearer foundation for future studies.

Discriminating the effects of local stressors from climatic factors and dispersal processes on multiple biodiversity dimensions of macroinvertebrate communities across subtropical drainage basins

Metacommunity ecology emphasizes that community structure and diversity are not only determined by local environmental conditions through environmental filtering, but also by dispersal-related processes, such as mass effects, dispersal limitation and patch dynamics. However, the roles of dispersal processes are typically ignored in bioassessment approaches. Here, we simultaneously explored the potential influences of four groups of factors: local stressors, climatic factors, within-basin spatial factors and basin identity in explaining variation in diversity indices of macroinvertebrate assemblages from seven subtropical tributary rivers. A total of 12 biodiversity indices based on species identities, functional traits and taxonomic relatedness were calculated and used in the subsequent statistical analysis. Our results showed that, although differing in their relative importance, the four explanatory factor groups all played important roles in explaining variation in biodiversity indices. Of the pure fractions, index variation was best explained by local environmental stressors, whereas the other three explanatory factor groups appeared less influential. Furthermore, diversity indices from species, functional and taxonomic dimensions responded distinctly to the focal ecological factors, and differed in their abilities to portray the effects of human disturbances on macroinvertebrate communities. Taxonomic distinctness indices performed best, with the highest amount of variation associated to local stressors and hardly any variation explained by other factors, implying that these indices are robust in portraying human disturbances in streams. However, species diversity and functional diversity indices were also affected by spatial processes and climatic factors, suggesting that these indices should be used with caution in bioassessment. We hence conclude that environmental assessment of riverine ecosystems should not rely entirely on the perspective of species sorting. In contrast, both roles of spatial processes and environmental variables related to human disturbances and climatic variation should be incorporated in management and conservation of riverine ecosystems.

Functional differences in spatial processing along an anterior-posterior axis: are there implications for the retrosplenial cortex?

The retrosplenial cortex has recently received attention from the neuroscience community for its role in spatial processing and involvement in diseases such as Alzheimer's. Here, we discuss a recent study by Silson et al. (Silson EH, Gilmore AW, Kalinowski SE, Steel A, Kidder A, Martin A, Baker CI. J Neurosci 39: 705-717, 2019.) that reported functionally specific activation within this region during scene perception and (mnemonic) construction. We then propose considerations for future experiments such as adopting standardized methodology and terminology that may improve the interpretation of retrosplenial cortex function within the broader literature.

Metacommunity ecology meets bioassessment: Assessing spatio-temporal variation in multiple facets of macroinvertebrate diversity in human-influenced large lakes

Metacommunity theory emphasizes that local communities are jointly affected by environmental filtering and spatial processes. However, the roles of spatial processes are often given insufficient attention in bioassessment practices, which may bias the assessments of ecological status based on biotic metrics. Here, we quantified the relative importance and the seasonal stability of spatial processes, natural conditions and human-induced factors in structuring variation in different bioassessment metrics based on macroinvertebrate communities. Our study systems were two extensively sampled large and shallow lakes with strong nutrient gradients related to human disturbance. The roles of different drivers were examined for three kinds of indicators: general diversity, trait-based and taxonomic distinctness metrics, and their performance in characterizing human disturbance was evaluated. Overall, human-induced and spatial factors were all important in explaining variation in the three types of bioassessment metrics. Contrary to our expectations, however, we found that the importance of spatial processes on bioassessment metrics can be comparable to the effects of local environmental conditions at the within-lake scale. Furthermore, the results showed substantial seasonal variability in the relative roles of different drivers, which might be linked to life-cycle seasonality of macroinvertebrates. As expected, trait-based metrics generally were best associated with human-induced variables in both lakes, whereas general diversity and taxonomic distinctness metrics performed poorly. The low effectiveness of taxonomic distinctness metrics might due to low species richness associated with high nutrient levels. To conclude, our results suggest that bioassessment cannot exclusively rely on the idea of environmental filtering even if we focus on fine spatial scales. We hence strongly urge that spatial processes, natural drivers and temporal variability should be better considered in combination in the development and application of bioassessment approaches. In addition, taxonomic distinctness measures should be used with caution, especially for the ecosystems and organism groups typically characterized by low species richness.

Development and topographical organization of projections from the hippocampus and parahippocampus to the retrosplenial cortex.

The rat hippocampal formation (HF), parahippocampal region (PHR), and retrosplenial cortex (RSC) play critical roles in spatial processing. These regions are interconnected, and functionally dependent. The neuronal networks mediating this reciprocal dependency are largely unknown. Establishing the developmental timing of network formation will help to understand the emergence of this dependency. We questioned whether the long‐range outputs from HF‐PHR to RSC in Long Evans rats develop during the same time periods as previously reported for the intrinsic HF‐PHR connectivity and the projections from RSC to HF‐PHR. The results of a series of retrograde and anterograde tracing experiments in rats of different postnatal ages show that the postnatal projections from HF‐PHR to RSC display low densities around birth, but develop during the first postnatal week, reaching adult‐like densities around the time of eye‐opening. Developing projections display a topographical organization similar to adult projections. We conclude that the long‐range projections from HF‐PHR to RSC develop in parallel with the intrinsic circuitry of HF‐PHR and the projections of RSC to HF‐PHR.

What explains sex differences in math anxiety? A closer look at the role of spatial processing

A large body of research has documented that females experience more math anxiety than males. Researchers have identified many factors that might explain the relation between sex and math anxiety. In the current study, we present a novel theoretical framework that highlights the importance of examining multiple aspects of processing across different cognitive domains. We use this framework to address the question of what best explains sex differences in math anxiety. One hundred and seventy-five undergraduate students completed a battery of cognitive tasks and affect questionnaires intended to measure actual math ability, perceived math ability, math anxiety, actual spatial ability, perceived spatial ability, and anxiety about situations requiring spatial mental manipulation (spatial anxiety). Results revealed that processes within the spatial domain but not in the mathematical domain mediated the relation between sex and math anxiety, controlling for general anxiety and cognitive ability. Moreover, within the spatial domain, spatial anxiety was the strongest mediator between sex and math anxiety, over actual and perceived spatial ability. Our findings point to spatial anxiety as a key contributor to the commonly reported sex differences in math anxiety. We conclude by raising the possibility that sex differences in math anxiety, may be rooted in sex-related differences in anxiety about or avoidance of spatial strategies in solving mathematical tasks.

Collateral Projections Innervate the Mammillary Bodies and Retrosplenial Cortex: A New Category of Hippocampal Cells.

To understand the hippocampus, it is necessary to understand the subiculum. Unlike other hippocampal subfields, the subiculum projects to almost all distal hippocampal targets, highlighting its critical importance for external networks. The present studies, in male rats and mice, reveal a new category of dorsal subiculum neurons that innervate both the mammillary bodies (MBs) and the retrosplenial cortex (RSP). These bifurcating neurons comprise almost half of the hippocampal cells that project to RSP. The termination of these numerous collateral projections was visualized within the medial mammillary nucleus and the granular RSP (area 29). These collateral projections included subiculum efferents that cross to the contralateral MBs. Within the granular RSP, the collateral projections form a particularly dense plexus in deep Layer II and Layer III. This retrosplenial termination site colocalized with markers for VGluT2 and neurotensin. While efferents from the hippocampal CA fields standardly collateralize, subiculum projections often have only one target site. Consequently, the many collateral projections involving the RSP and the MBs present a relatively unusual pattern for the subiculum, which presumably relates to how both targets have complementary roles in spatial processing. Furthermore, along with the anterior thalamic nuclei, the MBs and RSP are key members of a memory circuit, which is usually described as both starting and finishing in the hippocampus. The present findings reveal how the hippocampus simultaneously engages different parts of this circuit, so forcing an important revision of this network.

Energetic constraints to food chain length in a metacommunity framework

As metabolism increases with body size, populations of large-sized species can become constrained to relatively low trophic positions within a local community due to their high energetic demands combined with the limited efficiency with which energy is transferred up the food chain from primary producers. In a metacommunity context, dispersal can become a major driver of population dynamics and persistence, having also the potential to ameliorate the aforementioned energetic constraints due to its effect on colonization and energy subsidies from connected patches. Here, we derive a size-dependent model for food chain length in communities subjected to migration and show that populations with higher influx of migrants are able to persist at higher trophic positions. Simulations of random, dendritic, and real aquatic metacommunities corroborate this result and further indicate that community location in the landscape (relative centrality or isolation) may determine local food web structure. More central patches contained larger populations and were less constrained in trophic position. This effect was particularly strong in dendritic metacommunities, which are representative of freshwater watersheds in general. Furthermore, the role of spatial processes is nonlinearly intensified with increases in body size, indicating that larger organisms have a much stronger dependence on landscape attributes.

The Right Supramarginal Gyrus Is Important for Proprioception in Healthy and Stroke-Affected Participants: A Functional MRI Study.

Human proprioception is essential for motor control, yet its central processing is still debated. Previous studies of passive movements and illusory vibration have reported inconsistent activation patterns related to proprioception, particularly in high-order sensorimotor cortices. We investigated brain activation specific to proprioception, its laterality, and changes following stroke. Twelve healthy and three stroke-affected individuals with proprioceptive deficits participated. Proprioception was assessed clinically with the Wrist Position Sense Test, and participants underwent functional magnetic resonance imaging scanning. An event-related study design was used, where each proprioceptive stimulus of passive wrist movement was followed by a motor response of mirror ­copying with the other wrist. Left (LWP) and right (RWP) wrist proprioception were tested separately. Laterality indices (LIs) were calculated for the main cortical regions activated during proprioception. We found proprioception-related brain activation in high-order sensorimotor cortices in healthy participants especially in the supramarginal gyrus (SMG LWP z = 4.51, RWP z = 4.24) and the dorsal premotor cortex (PMd LWP z = 4.10, RWP z = 3.93). Right hemispheric dominance was observed in the SMG (LI LWP mean 0.41, SD 0.22; RWP 0.29, SD 0.20), and to a lesser degree in the PMd (LI LWP 0.34, SD 0.17; RWP 0.13, SD 0.25). In stroke-affected participants, the main difference in proprioception-related brain activation was reduced laterality in the right SMG. Our findings indicate that the SMG and PMd play a key role in proprioception probably due to their role in spatial processing and motor control, respectively. The findings from stroke-­affected individuals suggest that decreased right SMG function may be associated with decreased proprioception. We recommend that clinicians pay particular attention to the assessment and rehabilitation of proprioception following right hemispheric lesions.

Cover crop effect on corn growth and yield as influenced by topography

The use of cover crops is reported to enhance ecosystem services, however their adoption by farmers has remained limited. A challenge to farmer uptake is high spatial and temporal variability in cover crop growth and performance. Since topography plays an important role in spatial processes that ultimately affect plant performance, it could be used to quantify cover crop spatial variability and cover crop contribution to a subsequent cash crop. We assessed the effects of topography and cover crop (red clover) biomass on corn yields. Hierarchical path analysis was used to identify direct and indirect relationships among topography, red clover biomass, and corn yield, while taking into account the effects of agricultural management practices, multiple years, and multiple experimental fields. We observed that topography contribute significantly to explaining the variability in both red clover biomass and corn yields. Higher red clover biomass was produced in flat areas, whereas higher corn yield was produced in areas with high curvature. Red clover biomass positively influenced corn yield, however, the magnitude of that effect varied both temporally and spatially. The effect of red clover on corn yields was significant only in the years with lowest precipitation; and its magnitude was more pronounced at summit and slope topographical positions. Therefore, a good cover crop stand will be most beneficial to subsequent corn crop at summit and slope positions. Accounting for variability in fields and years using a hierarchical model significantly improved analysis of the interactive relationships between topography, red clover, and corn; therefore we encouraged its use in agroecological research.

The role of spatial processes and environmental determinants in microgeographic shell variation of the freshwater snail Chilina dombeyana (Bruguière, 1789)

Wildlife data often show spatial organization, demonstrating positive correlations either as a result of processes occurring over the landscape or due to the influence of spatially structured environmental variables. It is, thus, essential to consider non-random spatial structure when evaluating the underlying causes of biological variation. In this study, we analyzed the population structure of Chilina dombeyana shell morphology of 14 populations that are close geographically and belong to the same hydrographic basin. We utilized a variation partitioning approach to evaluate the importance of spatial processes, such as migration, acting over the landscape, and environmental characteristics, including habitat and hydrologic characteristics, and the occurrence of aquatic predators in promoting between population variation. Our results demonstrate spatially structured variation in C. dombeyana shell morphology, with populations living near each other having more similar shell sizes than populations living farther apart. The shell size variation partition indicated that both spatially structured environmental factors and genetic relationships resulting from migration or shared common ancestry may explain this pattern. Shell shape variation, in contrast, was found to be essentially under the influence of non-spatially structured environmental factors, with habitat and water characteristics accounting for about half of the total variation among populations. The large proportion of the variation in shell size that is spatially structured demonstrates that spatial structure on morphological traits might be strong and highlights the need to consider such phenomenon in intraspecific studies of phenotypic evolution.

Habitat isolation shapes the recovery of aquatic insect communities from a pesticide pulse

Summary1. The role of spatial processes in ecotoxicology is largely ignored. Yet, together with species‐specific sensitivities to the pollutant, spatial processes may determine community recovery and the resulting community composition after a pollution event.2. We investigated the isolation‐specific potential for internal recovery by reproduction and external recovery by dispersal after a pesticide pulse in experimental aquatic insect communities along an isolation gradient.3. External recovery was important in the univoltine species and in a multivoltine species that went locally extinct but only when a source population was nearby. Internal recovery occurred in all multivoltine species and was unexpectedly stronger in more isolated communities, probably because of release from a dispersal‐limited key predator.4. As a result, community recovery and resulting changes in composition strongly depended on isolation and species differences in the potential for external recovery through dispersal and internal recovery through reproduction.5. Synthesis and applications. Our results indicate that while the immediate impact of a toxicant on natural communities is shaped by species sensitivities, their recovery is primarily dependent on the degree of isolation. Risk assessment and the protection of communities under toxicant threat may improve greatly from considering the spatial context: isolated communities and communities with poor dispersers should receive extra protection to safeguard their member species. Ideally, land use planning should strive to remediate isolation of natural communities under threat in agricultural landscapes. Where this is not possible, spatial regulation of pesticide application may considerably improve protection of extant diversity.

Real-World Scene Representations in High-Level Visual Cortex: It's the Spaces More Than the Places

Real-world scenes are incredibly complex and heterogeneous, yet we are able to identify and categorize them effortlessly. In humans, the ventral temporal parahippocampal place area (PPA) has been implicated in scene processing, but scene information is contained in many visual areas, leaving their specific contributions unclear. Although early theories of PPA emphasized its role in spatial processing, more recent reports of its function have emphasized semantic or contextual processing. Here, using functional imaging, we reconstructed the organization of scene representations across human ventral visual cortex by analyzing the distributed response to 96 diverse real-world scenes. We found that, although individual scenes could be decoded in both PPA and early visual cortex (EVC), the structure of representations in these regions was vastly different. In both regions, spatial rather than semantic factors defined the structure of representations. However, in PPA, representations were defined primarily by the spatial factor of expanse (open, closed) and in EVC primarily by distance (near, far). Furthermore, independent behavioral ratings of expanse and distance correlated strongly with representations in PPA and peripheral EVC, respectively. In neither region was content (manmade, natural) a major contributor to the overall organization. Furthermore, the response of PPA could not be used to decode the high-level semantic category of scenes even when spatial factors were held constant, nor could category be decoded across different distances. These findings demonstrate, contrary to recent reports, that the response PPA primarily reflects spatial, not categorical or contextual, aspects of real-world scenes.

Spatial filter by spike timing dependent plasticity

Spike timing dependent plasticity (STDP) is found in various areas of the brain, visual cortex, hippocampus and hindbrain of electric fish, etc. The synaptic modification by STDP depends on time difference between presynaptic spike arrival and postsynaptic firing. If presynaptic neuron fires earlier than postsynaptic neuron dose, synaptic weight is strengthened. If postsynaptic neuron fires earlier than presynaptic neuron dose, synaptic weight is weakened. This learning rule is one example of various rules (hippocampal type). The learning rule of electric fish type is reversed. Changes of synaptic efficiency precisely depend on timing of pre- and postsynaptic spikes under STDP. Because of this precise dependence, STDP is thought to play the important role in temporal processing of stimuli. Temporal processing by STDP is well known. However, the role of STDP in spatial processing is not enough understood. To investigate spatial processing by STDP, We studied the role in spatial processing on interconnected network with STDP, using computer simulation. In this study, we found two type spatial filter by STDP on interconnected network. One is low pass filter using the learning rule of electric fish type. Another is edge-enhancing filter using the learning rule of hippocampus type. In this study, we calculated the response of interconnected neural network with STDP learning. The structure of the network is one-dimensional array. The neuron of the network has connection to neighbour neurons. In the case of learning rule of electric fish type, the network provided the function of low pass filter. The network was stimulated by direct current rectangularly distributed with noise. We examined two cases. In one case, synaptic modification did not occur (Fig ​(Fig1a).1a). In another case, synaptic modification occurred (Fig ​(Fig1b).1b). In the first case, Noise presented in response of the network and covered the rectangular form of stimulus. In the second case, noise was eliminated and the rectangular form of stimulus was represented. In the case of learning rule of hippocampal type, the network provided the function of edge-enhancing filter. The network was stimulated by direct current rectangularly distributed. The firing rate of the neuron that represents the edge of stimulus was larger than one of the others. This result shows that the network with hipocampal type STDP plays the role of edge-enhancing filter. These results show that interconnected network with STDP provides the function of spatial filter, and suggest that STDP would plays the important role in spatial processing. Figure 1 Response of network. Vertical and horizontal line indicates response of the network and neuronal number, respectively. (a) and (b) show the response of the network without and with STDP learning, respectively.