Location-specific Manner Research Articles

Hippocampal place cell responses to distal and proximal cue manipulations in dopamine D2 receptor-knockout mice

The human hippocampus is critical for learning and memory. In rodents, hippocampal pyramidal neurons fire in a location-specific manner and form relational representations of environmental cues. The important roles of dopaminergic D1 receptors in learning and in hippocampal neural synaptic plasticity in novel environments have been previously shown. However, the roles of D2 receptors in hippocampal neural plasticity in response to novel and familiar spatial stimuli remain unclear. In order to clarify this issue, we recorded from hippocampal neurons in dopamine D2 receptor-knockout (D2R-KO) mice and their wild-type (WT) littermates during manipulations of distinct spatial cues in familiar and novel environments. Here, we report that D2R-KO mice showed substantial deficits in place-cell properties (number of place cells, intra-field firing rates, spatial tuning, and spatial coherence). Furthermore, although place cells in D2R-KO mice responded to manipulations of distal and proximal cues in both familiar and novel environments in a manner that was similar to place cells in WT mice, place fields were less stable in the D . The axes represent the differences between the peak and the valley of each waveform of EL2 and EL3.2R-KO mice in the familiar environment, but not in the novel environment. The present results suggested that D2 receptors in the hippocampus are important for place response stability. The place-cell properties of D2R-KO mice were similar to aged animals, suggesting that the alterations of place-cell properties in aged animals might be ascribed partly to alterations in the D2R in the HF of aged animals.

Morphological parameters associated with ruptured posterior communicating aneurysms.

The rupture risk of unruptured intracranial aneurysms is known to be dependent on the size of the aneurysm. However, the association of morphological characteristics with ruptured aneurysms has not been established in a systematic and location specific manner for the most common aneurysm locations. We evaluated posterior communicating artery (PCoA) aneurysms for morphological parameters associated with aneurysm rupture in that location. CT angiograms were evaluated to generate 3-D models of the aneurysms and surrounding vasculature. Univariate and multivariate analyses were performed to evaluate morphological parameters including aneurysm volume, aspect ratio, size ratio, distance to ICA bifurcation, aneurysm angle, vessel angles, flow angles, and vessel-to-vessel angles. From 2005–2012, 148 PCoA aneurysms were treated in a single institution. Preoperative CTAs from 63 patients (40 ruptured, 23 unruptured) were available and analyzed. Multivariate logistic regression revealed that smaller volume (p = 0.011), larger aneurysm neck diameter (0.048), and shorter ICA bifurcation to aneurysm distance (p = 0.005) were the most strongly associated with aneurysm rupture after adjusting for all other clinical and morphological variables. Multivariate subgroup analysis for patients with visualized PCoA demonstrated that larger neck diameter (p = 0.018) and shorter ICA bifurcation to aneurysm distance (p = 0.011) were significantly associated with rupture. Intracerebral hemorrhage was associated with smaller volume, larger maximum height, and smaller aneurysm angle, in addition to lateral projection, male sex, and lack of hypertension. We found that shorter ICA bifurcation to aneurysm distance is significantly associated with PCoA aneurysm rupture. This is a new physically intuitive parameter that can be measured easily and therefore be readily applied in clinical practice to aid in the evaluation of patients with PCoA aneurysms.

A Novel Approach for Security Testing of Client Server Based Applications using Misuse Deployment Diagrams, Misuse Cases and Threat Trees

Security testing is one of the most important security practices today. To secure an application it's important to go for a security testing phase during the development life cycle. Many useful enhancements are done using UML diagrams to model security like Misuse cases, Mis-sequence diagrams and Misuse deployment diagrams etc. Misuse deployment diagrams can be used to model a client server environment with security aspects. Since in client server environment it is important to know where to apply your security, it's better to use Misuse Deployment diagrams which can give an overall view of the system in a single model. Based on this fact, an approach is proposed in this paper by combining Misuse deployment diagrams and Misuse Case diagrams with threat trees to generate security test cases. The approach is demonstrated with a case study where Misuse deployment diagrams, Misuse Cases are used to show that possible security defects can be identified using these diagrams and combined those with threat trees. Finally the threat trees are traversed to generate test sequences. This approach is suitable for detecting threats that need to be tested in location specific manner in client-server applications.

The Intronic Long Noncoding RNA ANRASSF1 Recruits PRC2 to the RASSF1A Promoter, Reducing the Expression of RASSF1A and Increasing Cell Proliferation

The down-regulation of the tumor-suppressor gene RASSF1A has been shown to increase cell proliferation in several tumors. RASSF1A expression is regulated through epigenetic events involving the polycomb repressive complex 2 (PRC2); however, the molecular mechanisms modulating the recruitment of this epigenetic modifier to the RASSF1 locus remain largely unknown. Here, we identify and characterize ANRASSF1, an endogenous unspliced long noncoding RNA (lncRNA) that is transcribed from the opposite strand on the RASSF1 gene locus in several cell lines and tissues and binds PRC2. ANRASSF1 is transcribed through RNA polymerase II and is 5′-capped and polyadenylated; it exhibits nuclear localization and has a shorter half-life compared with other lncRNAs that bind PRC2. ANRASSF1 endogenous expression is higher in breast and prostate tumor cell lines compared with non-tumor, and an opposite pattern is observed for RASSF1A. ANRASSF1 ectopic overexpression reduces RASSF1A abundance and increases the proliferation of HeLa cells, whereas ANRASSF1 silencing causes the opposite effects. These changes in ANRASSF1 levels do not affect the RASSF1C isoform abundance. ANRASSF1 overexpression causes a marked increase in both PRC2 occupancy and histone H3K27me3 repressive marks, specifically at the RASSF1A promoter region. No effect of ANRASSF1 overexpression was detected on PRC2 occupancy and histone H3K27me3 at the promoter regions of RASSF1C and the four other neighboring genes, including two well-characterized tumor suppressor genes. Additionally, we demonstrated that ANRASSF1 forms an RNA/DNA hybrid and recruits PRC2 to the RASSF1A promoter. Together, these results demonstrate a novel mechanism of epigenetic repression of the RASSF1A tumor suppressor gene involving antisense unspliced lncRNA, in which ANRASSF1 selectively represses the expression of the RASSF1 isoform overlapping the antisense transcript in a location-specific manner. In a broader perspective, our findings suggest that other non-characterized unspliced intronic lncRNAs transcribed in the human genome might contribute to a location-specific epigenetic modulation of genes.

Abstract TP77: Simple Morphological Parameters Associated With The Rupture Risk Of Posterior Communicating Artery Aneurysms.

Introduction: The contribution of morphological characteristics to the treatment decision of unruptured aneurysms has not been established in a systematic and location specific manner. We present a large sample of posterior communicating (PComm) aneurysms that were assessed using a diverse array of morphological variables to determine the parameters associated with aneurysm rupture. Methods: Demographic and clinical risk factors of aneurysm rupture were obtained viachart review. Pre-operative CT angiograms (CTA) were evaluated with 3D Slicer© to generate 3-D models of the aneurysms and surrounding vascular architecture. Morphological parameters examined in each model included aneurysm volume, aspect ratio, size ratio, distance to bifurcation and origin points, aneurysm angle, vessel angles, flow angles, and parent-daughter angles. Univariate and multivariate analyses were performed to determine statistical significance. Results: From 2005-2011, 141 PComm aneurysms were treated in a single institution, and preoperative CTAs from 48 patients (32 ruptured, 16 unruptured) were analyzed. Those that underwent reoperation, were associated with arteriovenous malformations, or lacked a preoperative CTA were excluded. Ruptured aneurysms were associated with smaller volume, greater aspect ratio, greater size ratio, smaller internal carotid artery (ICA) to aneurysm neck angle, larger PComm flow angle, larger ICA to PComm angle, and smaller PComm to daughter vessel angle. Multivariate logistic regression revealed that a larger neck diameter, greater aspect ratio, greater size ratio, and shorter ICA bifurcation to aneurysm distance were the most strongly associated with rupture after adjusting for all other variables. Interestingly, volume of the aneurysm had a smaller effect size than most other variables and rupture risk was associated with smaller volumes. Conclusion: We found that larger neck diameter, greater aspect ratio, greater size ratio, and smaller ICA bifurcation to aneurysm distance to be highly associated with PComm aneurysm rupture. These are easily measured and physically intuitive parameters. They are more strongly associated with PComm aneurysm rupture than size alone and can be readily applied in clinical practice.

Microenvironmental regulation of inducible nitric oxide synthase expression and nitric oxide production in mouse bone marrow-derived mast cells

In addition to its well-known role in relaxation of vascular smooth muscle, NO modulates immune responses in a concentration- and location-specific manner. For MC, it is well accepted that exogenous NO regulates their function. However, there are inconsistencies in the literature of whether MC express NOS and make NO. MC progenitors mature in peripheral tissues, but the factors that influence MC maturation and their specific phenotype, such as whether they express NOS, are not well understood. To study microenvironmental conditions that could be "permissive" for NOS expression, we cultured BMMC in various conditions--BMMC(IL-3), BMMC(SCF/IL-3), or BMMC(SCF/IL-4)-for >3 weeks and examined NOS expression. We detected Nos2 mRNA in BMMC(SCF/IL-4) but not BMMC(IL-3) or BMMC(SCF/IL-3). After stimulation with IFN-γ and/or LPS, NOS2 expression and NO production were detected in BMMC(SCF/IL-4) but rarely detected in BMMC cultured with other conditions. Confocal microscopic analysis showed that NOS2 expression induced by IFN-γ colocalized in CD117(+) BMMC. NO production, after activation with IFN-γ and LPS in BMMC(SCF/IL-4), was abrogated by pretreatment with the NOS2-specific inhibitor. In addition to NOS2 expression, BMMC(SCF/IL-4) were distinguished from BMMC(IL-3) in heparin and MMCP expression. Thus, MC progenitors that develop in SCF + IL-4 can be induced to express NOS2 after receiving appropriate signals, such as IFN-γ, and subsequently produce NO. Microenvironmental conditions during their development can influence whether MC are capable of NOS expression and of NO production.

Opposite effects of fear conditioning and extinction on dendritic spine remodelling

It is generally believed that fear extinction is a form of new learning that inhibits rather than erases previously acquired fear memories. Although this view has gained much support from behavioural and electrophysiological studies, the hypothesis that extinction causes the partial erasure of fear memories remains viable. Using transcranial two-photon microscopy, we investigated how neural circuits are modified by fear learning and extinction by examining the formation and elimination of postsynaptic dendritic spines of layer-V pyramidal neurons in the mouse frontal association cortex. Here we show that fear conditioning by pairing an auditory cue with a footshock increases the rate of spine elimination. By contrast, fear extinction by repeated presentation of the same auditory cue without a footshock increases the rate of spine formation. The degrees of spine remodelling induced by fear conditioning and extinction strongly correlate with the expression and extinction of conditioned fear responses, respectively. Notably, spine elimination and formation induced by fear conditioning and extinction occur on the same dendritic branches in a cue- and location-specific manner: cue-specific extinction causes formation of dendritic spines within a distance of two micrometres from spines that were eliminated after fear conditioning. Furthermore, reconditioning preferentially induces elimination of dendritic spines that were formed after extinction. Thus, within vastly complex neuronal networks, fear conditioning, extinction and reconditioning lead to opposing changes at the level of individual synapses. These findings also suggest that fear memory traces are partially erased after extinction.

Pangolin expression influences the development of a morphological novelty: Beetle horns

Morphological diversity arises during development through the actions and interactions of diverse developmental pathways. Among those, the Wnt pathway is known to contribute to diverse developmental processes such as segmentation and the morphogenesis of appendages. Here, we characterize a transcription factor in the Wnt pathway, pangolin (pan), to investigate the role of Wnt signaling in the development of evolutionarily novel body structures: the horns of beetles. Beetle horns are highly diverse in size, shape, and number and develop principally from two major body regions: the head and prothorax. We investigate horns in two species of the genus Onthophagus using comparative in situ hybridization, larval RNA interference, and allometric measurements to analyze whether horn formation is regulated by pan and by extension the Wnt pathway. Our results illustrate that pan expression affects beetle horn growth in a species-, sex-, and location-specific manner in two morphologically distinct, yet closely-related, Onthophagus species.

S.07.05 Deep brain stimulation of the ventral striatum affects consummatory and motivated behaviour in a location-specific manner

S.07.05 Deep brain stimulation of the ventral striatum affects consummatory and motivated behaviour in a location-specific manner

Glutamate induces de novo growth of functional spines in developing cortex

Mature cortical pyramidal neurons receive excitatory inputs onto small protrusions emanating from their dendrites called spines. Spines undergo activity-dependent remodeling, stabilization, and pruning during development and similar structural changes can be triggered by learning and changes in sensory experiences1–4. However, the biochemical triggers and mechanisms of de novo spine formation in the developing brain and the functional significance of new spines to neuronal connectivity are largely unknown. We developed an approach to induce and monitor de novo spine formation in real-time using combined two-photon laser-scanning microscopy and two-photon laser uncaging of glutamate. Our data demonstrate that, in mouse cortical layer 2/3 pyramidal neurons, glutamate is sufficient to trigger de novo spine growth from the dendrite shaft in a location-specific manner. We find that glutamate-induced spinogenesis requires opening of NMDA-type glutamate receptors and activation of PKA but is independent of CaMKII and TrkB receptors. Furthermore, newly formed spines express glutamate receptors and are rapidly functional such that they transduce presynaptic activity into postsynaptic signals. Together, our data demonstrate that early neural connectivity is shaped by activity in a spatially precise manner and that nascent dendrite spines are rapidly functionally incorporated into cortical circuits.

P.3.011 Deep brain stimulation of the nucleus accumbens affects operant responding and consummatory behaviour in a location-specific manner

P.3.011 Deep brain stimulation of the nucleus accumbens affects operant responding and consummatory behaviour in a location-specific manner

Geometric and functional architecture of visceral sensory microcircuitry

Is microcircuit wiring designed deterministically or probabilistically? Does geometric architecture predict functional dynamics of a given neuronal microcircuit? These questions were addressed in the visceral sensory microcircuit of the caudal nucleus of the tractus solitarius (NTS), which is generally thought to be homogeneous rather than laminar in cytoarchitecture. Using in situ hybridization histochemistry and whole-cell patch clamp recordings followed by neuronal reconstruction with biocytin filling, anatomical and functional organization of NTS microcircuitry was quantified to determine associative relationships. Morphologic and chemical features of NTS neurons displayed different patterns of process arborization and sub-nuclear localization according to neuronal types: smaller cells featured presynaptic local axons and GABAergic cells were aggregated specifically within the ventral NTS. The results suggested both a laminar organization and a spatial heterogeneity of NTS microcircuit connectivity. Geometric analysis of pre- and postsynaptic axodendritic arbor overlap of reconstructed neurons (according to parent somal distance) confirmed a heterogeneity of microcircuit connectivity that could underlie differential functional dynamics along the dorsoventral axis. Functional dynamics in terms of spontaneous and evoked postsynaptic current patterns behaved in a strongly location-specific manner according to the geometric dimension, suggesting a spatial laminar segregation of neuronal populations: a dorsal group of high excitation and a ventral group of balanced excitation and inhibition. Recurrent polysynaptic activity was also noted in a subpopulation of the ventral group. Such geometric and functional laminar organization seems to provide the NTS microcircuit with both reverberation capability and a differentiated projection system for appropriate computation of visceral sensory information.Electronic supplementary materialThe online version of this article (doi:10.1007/s00429-010-0294-5) contains supplementary material, which is available to authorized users.

Location-specific activation of the paraventricular nucleus of the hypothalamus by localized inflammation

The existence of an immunological homunculus has been proposed, but evidence for location-specific response of the central nervous system to immunological stimulation is lacking. In this study, we show that inflammation induced by injection of casein into one of the causes c-fos expression in the paraventricular nucleus of the hypothalamus (PVN) in an asymmetrical manner: much stronger activation is always induced in the contralateral PVN. Unilateral sciatic nerve transection abolished the casein-induced PVN activation if casein was injected into the hindlimb with the nerve transection, but had no effect if casein was injected into the hindlimb with intact nerve innervation. Injection of casein into one the forelimbs also caused contralateral PNV activation. Further, stronger PVN activation was found in the anterior PVN after the forelimb injection, but in the posterior PVN after the hindlimb injection. Casein-induced PVN activation is absent in IL-1R1 KO, IL-6 KO, TNFα KO, and in C3H/HeJ (TLR4 mutant) animals. In comparison, injection of LPS, a systemic inflammagen, into one hindlimb induced bilateral PVN activation but injection of live Escherichia coli into one hindlimb induced contralateral PVN activation. These results support the notion that local inflammation may activate the PVN by neural routes in a location-specific manner.

Geometric and functional architecture of visceral sensory microcircuitry

Is microcircuit wiring designed deterministically or probabilistically? Does geometric architecture predict functional dynamics of a given neuronal microcircuit? These questions were addressed in the visceral sensory microcircuit of the caudal nucleus of the tractus solitarius (NTS), which is generally thought to be homogeneous rather than laminar in cytoarchitecture. Using in situ hybridization histochemistry and whole-cell patch clamp recordings followed by neuronal reconstruction with biocytin filling, anatomical and functional organization of NTS microcircuitry was quantified to determine associative relationships. Morphologic and chemical features of NTS neurons displayed different patterns of process arborization and sub-nuclear localization according to neuronal types: smaller cells featured presynaptic local axons and GABAergic cells were aggregated specifically within the ventral NTS. The results suggested both a laminar organization and a spatial heterogeneity of NTS microcircuit connectivity. Geometric analysis of pre- and postsynaptic axodendritic arbor overlap of reconstructed neurons (according to parent somal distance) confirmed a heterogeneity of microcircuit connectivity that could underlie differential functional dynamics along the dorsoventral axis. Functional dynamics in terms of spontaneous and evoked postsynaptic current patterns behaved in a strongly location-specific manner according to the geometric dimension, suggesting a spatial laminar segregation of neuronal populations: a dorsal group of high excitation and a ventral group of balanced excitation and inhibition. Recurrent polysynaptic activity was also noted in a subpopulation of the ventral group. Such geometric and functional laminar organization seems to provide the NTS microcircuit with both reverberation capability and a differentiated projection system for appropriate computation of visceral sensory information.

Dopamine D1Receptor Modulates Hippocampal Representation Plasticity to Spatial Novelty

The human hippocampus is critical for learning and memory. In rodents, hippocampal pyramidal neurons fire in a location-specific manner, forming relational representations of environmental cues. The importance of glutamatergic systems in learning and in hippocampal neural synaptic plasticity has been shown. However, the role of dopaminergic systems in the response of hippocampal neural plasticity to novel and familiar spatial stimuli remains unclear. To clarify this important issue, we recorded hippocampal neurons from dopamine D(1) receptor knock-out (D1R-KO) mice and their wild-type (WT) littermates under the manipulation of distinct spatial cues in a familiar and a novel environment. Here we report that in WT mice, the majority of place cells quickly responded to the manipulations of distal and proximal cues in both familiar and novel environments. In contrast, the influence of distal cues on spatial firing in D1R-KO mice was abolished. In the D1R-KO mice, the influence of proximal cues was facilitated in a familiar environment, and in a novel environment most of the place cells were less likely to respond to changes of spatial cues. Our results demonstrate that hippocampal neurons in mice can rapidly and flexibly encode information about space from both distal and proximal cues to cipher a novel environment. This ability is necessary for many types of learning, and lacking D1R can radically alter this learning-related neural activity. We propose that D1R is crucially implicated in encoding spatial information in novel environments, and influences the plasticity of hippocampal representations, which is important in spatial learning and memory.

Spatial heterogeneity in sediment-associated bacterial and eukaryotic communities in a landfill leachate-contaminated aquifer

Heterogeneity in eukaryotic and bacteria community structure in surface and subsurface sediment samples downgradient of the Banisveld landfill (The Netherlands) was studied using a culturing-independent molecular approach. Along a transect covering the part of the aquifer most polluted by landfill leachate, sediment was sampled at 1-m depth intervals, until a depth of 5.5 m, at four distances from the landfill. Two drillings were placed in a nearby clean area as a reference. Denaturing gradient gel electrophoresis banding patterns revealed high bacterial and eukaryotic diversity and complex community structures. Bacteria and eukaryotic community profiles in polluted samples grouped different from those in clean samples. Bacteria community profiles in surface samples clustered together and separately from subsurface community profiles. Subsurface bacteria profiles clustered in a location-specific manner. Eukaryotic community structure did not significantly relate to distance from the landfill or depth. No significant spatial autocorrelation of bacteria or eukaryotic communities was observed over 1-m depth intervals per sampling location. Spatial heterogeneity in sediment-associated bacterial communities appears to be much larger than in groundwater. We discuss how on the one hand, spatial heterogeneity may complicate the assessment of microbial community structure and functioning, while on the other it may provide better opportunities for natural attenuation.

Estrogen modulates neuronal movements within the developing preoptic area–anterior hypothalamus

The preoptic area-anterior hypothalamus (POA-AH) is characterized by sexually dimorphic features in a number of vertebrates and is a key region of the forebrain for regulating physiological responses and sexual behaviours. Using live-cell fluorescence video microscopy with organotypic brain slices, the current study examined sex differences in the movement characteristics of neurons expressing yellow fluorescent protein (YFP) driven by the Thy-1 promoter. Cells in slices from embryonic day 14 (E14), but not E13, mice displayed significant sex differences in their basal neuronal movement characteristics. Exposure to 10 nm estradiol-17beta (E2), but not 100 nm dihydrotestosterone, significantly altered cell movement characteristics within minutes of exposure, in a location-specific manner. E2 treatment decreased the rate of motion of cells located in the dorsal POA-AH but increased the frequency of movement in cells located more ventrally. These effects were consistent across age and sex. To further determine whether early-developing sex differences in the POA-AH depend upon gonadal steroids, we examined cell positions in mice with a disruption of the steroidogenic factor-1 gene, in which gonads do not form. An early-born cohort of cells were labelled with the mitotic indicator bromodeoxyuridine (BrdU) on E11. More cells were found in the POA-AH of females than males on the day of birth (P0) regardless of gonadal status. These results support the hypothesis that estrogen partially contributes to brain sexual dimorphism through its influence on cell movements during development. Estrogen's influence may be superimposed upon a pre-existing genetic bias.

Location specificity of plantar cutaneous reflexes involving lower limb muscles in humans

It is known that cutaneous reflexes in human hand muscles show strong location-specificity dependent on the digit stimulated. We hypothesized that in lower leg muscles the cutaneous reflex following tactile sensation of the plantar surface of the foot is also organized in a location-specific manner. The purpose of the present study was to test this hypothesis. Middle latency reflexes (approximately 70-110 ms, MLR) following non-noxious electrical stimulation to different locations on the plantar foot were recorded from 16 neurologically intact volunteers (15 males, 1 female). Electrical stimulation was given to the fore-medial (f-M), fore-lateral (f-L) and heel (HL) regions of the plantar surface of the right foot while the subjects performed isometric dorsiflexion (tibialis anterior, TA), plantarflexion (soleus, Sol and medial gastrocnemius, MG), eversion (peroneus longus, PL) and knee extension (vastus lateralis, VL) while sitting and standing. In the Sol and MG, an excitatory response was observed following HL stimulation, which was switched to an inhibitory response following f-M or f-L stimulation (P < 0.001). A reciprocal pattern in contrast to Sol was observed in the TA. In the PL, MLR exhibited significant excitation following both f-L and HL stimulation, which, however, was switched to an inhibitory response following f-M stimulation (P < 0.001). Moderate inhibition of the MLR was seen in the VL for all stimulated positions. Systematic stimulation along the lateral side of the plantar foot demonstrated that the reflex reversal occurred around the middle of the plantar foot in the Sol and TA. In all muscles tested, the slope of the regression line between the magnitude of the MLR and background electromyographic activity significantly decreased during standing compared with sitting except for the PL following f-L simulation. These results suggest that reflex effects from cutaneous nerves in the plantar foot onto the motoneurons innervating the lower leg muscles are organized in a highly topographic manner in humans. The organization of these reflexes may play an important role in the alteration of limb loading and/or ground contact in response to tactile sensation of the plantar foot while sitting and standing.

Increased Attention to Spatial Context Increases Both Place Field Stability and Spatial Memory

The hippocampal formation is critical for the acquisition and consolidation of memories. When recorded in freely moving animals, hippocampal pyramidal neurons fire in a location-specific manner: they are “place” cells, comprising a hippocampal representation of the animal's environment. To explore the relationship between place cells and spatial memory, we recorded from mice in several behavioral contexts. We found that long-term stability of place cell firing fields correlates with the degree of attentional demands and that successful spatial task performance was associated with stable place fields. Furthermore, conditions that maximize place field stability greatly increase orientation to novel cues. This suggests that storage and retrieval of place cells is modulated by a top-down cognitive process resembling attention and that place cells are neural correlates of spatial memory. We propose a model whereby attention provides the requisite neuromodulatation to switch short-term homosynaptic plasticity to long-term heterosynaptic plasticity, and we implicate dopamine in this process.

The optic tectum controls visually guided adaptive plasticity in the owl's auditory space map.

The midbrain contains an auditory map of space that is shaped by visual experience. When barn owls are raised wearing spectacles that horizontally displace the visual field, the auditory space map in the external nucleus of the inferior colliculus (ICX) shifts according to the optical displacement of the prisms. Topographic visual activity in the optic tectum could serve as the template that instructs the auditory space map. We studied the effects of a restricted, unilateral lesion in the portion of the optic tectum that represents frontal space. Here we show that such a lesion eliminates adaptive adjustments specifically in the portion of the auditory map that represents frontal space on the same side of the brain, while the rest of the map continues to adjust adaptively. Thus, activity in the tectum calibrates the auditory space map in a location-specific manner. Because the site of adaptive changes is the ICX, the results also indicate that the tectum provides a topographic instructive signal that controls adaptive auditory plasticity in the ICX.