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Learning cortical topography from spatiotemporal stimuli

BIOLOGICAL CYBERNETICS 2000年第2期82卷 173-187页

作者： Wiemer, J Spengler, F Joublin, F Stagge, P Wacquant, S Ruhr Univ Bochum Inst Neuroinformat D-44780 Bochum Germany

Stimulus representation is a functional interpretation of early sensory cortices. Early sensory cortices are subject to stimulus-induced modifications. Common models for stimulus-induced learning within topographic representations are based on the stimuli's spatial structure and probability distribution. Furthermore, we argue that average temporal stimulus distances reflect the stimuli's relatedness. As topographic representations reflect the stimuli's relatedness, the temporal structure of incoming stimuli is important for the learning in cortical maps. Motivated by recent neurobiological findings, we present an approach of cortical self-organization that additionally takes temporal stimulus aspects into account. The proposed model transforms average interstimulus intervals into representational distances. Thereby, neural topography is related to stimulus dynamics. This offers a new time-based interpretation of cortical maps. Our approach is based on a wave-like spread of cortical activity. Interactions between dynamics and feedforward activations lead to shifts of neural activity. The psychophysical saltation phenomenon map represent an analogue to the shifts proposed here. With regard to cortical plasticity, we offer an explanation for neurobiological findings that other models cannot explain. Moreover? we predict cortical reorganizations under new experimental, spatiotemporal conditions. With regard to psychophysics, we relate the saltation phenomenon to dynamics and interaction in early sensory cortices and predict further effects in the perception of spatiotemporal stimuli.

关键词：脑图计算机模拟类人猿亚目动力学学习/生理学模型神经学神经网/生理学神经元可塑性/生理学神经元/生理学物理刺激心理物理学躯体感觉皮质/细胞学躯体感觉皮质/生长和发育躯体感觉皮质/生理学空间知觉/生理学突触/生理学时间因素触觉/生理学动物

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An excitatory GABAergic plexus in developing neocortical layer 1

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JOURNAL OF NEUROPHYSIOLOGY 2000年第1期84卷 428-434页

作者： Dammerman, RS Flint, AC Noctor, S Kriegstein, AR Columbia Univ Coll Phys & Surg Dept Neurol New York NY 10032 USA Columbia Univ Coll Phys & Surg Ctr Neurobiol & Behav New York NY 10032 USA

Layer 1 of the developing rodent somatosensory cortex contains a dense, transient GABAergic fiber plexus. Axons arising from the zona incerta (ZI) of the ventral thalamus contribute to this plexus, as do axons of intrinsic GABAergic cells of layer 1. The function of this early-appearing fiber plexus is not known, but these fibers are positioned to contact the apical dendrites of most postmigratory neurons. Here we show that electrical stimulation of layer 1 results in a GABA(A)-mediated postsynaptic current (PSC) in pyramidal neurons. Gramicidin perforated patch recording demonstrates that the GABAergic layer 1 synapse is excitatory and can trigger action potentials in cortical neurons. In contrast to electrical stimulation, activation of intrinsic layer 1 neurons with a glutamate agonist fails to produce PSCs in pyramidal cells. In addition, responses can be evoked by stimulation of layer 1 at relatively large distances from the recording site. These findings are consistent with a contribution of the widely projecting incertocortical pathway, the only described GABAergic projection to neonatal cortex. Recording of identified neonatal incertocortical neurons reveals a population of active cells that exhibit high frequencies of spontaneous action potentials and are capable of robustly activating neonatal cortical neurons. Because the fiber plexus is confined to layer 1, this pathway provides a spatially restricted excitatory GABAergic innervation of the distal apical dendrites of pyramidal neurons during the peak period of cortical synaptogenesis.

关键词： 2-氨基-5-膦酰基戊酸盐/药理学动作电位/药物作用动作电位/生理学钙/代谢兴奋性氨基酸拮抗剂/药理学兴奋性突触后电位/药物作用兴奋性突触后电位/生理学荧光染料新皮质/化学新皮质/细胞学新皮质/生长和发育膜片钳术锥体细胞/化学锥体细胞/生理学喹恶啉类/药理学大鼠 Sprague-Dawley 若丹明类躯体感觉皮质/化学躯体感觉皮质/细胞学躯体感觉皮质/生长和发育突触/生理学 γ氨基丁酸/生理学动物大鼠

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Impairments in prehension produced by early postnatal sensory motor cortex activity blockade

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JOURNAL OF NEUROPHYSIOLOGY 2000年第2期83卷 895-906页

作者： Martin, JH Donarummo, L Hacking, A Columbia Univ Ctr Neurobiol & Behav New York NY 10032 USA New York State Psychiat Inst & Hosp New York NY 10032 USA

Impairments in prehension produced by early postnatal sensory motor cortex activity blockade. J. Neurophysiol. 83: 895-906, 2000. This study examined the effects of blocking neural activity in sensory motor cortex during early postnatal development on prehension. We infused muscimol, either unilaterally or bilaterally, into the sensory motor cortex of cats to block activity continuously between postnatal weeks 3-7. After stopping infusion, we trained animals to reach and grasp a cube of meat and tested behavior thereafter. Animals that had not received muscimol infusion (unilateral saline infusion;age-matched) reached for the meat accurately with small end-point errors. They grasped the meat using coordinated digit flexion followed by forearm supination on 82.7% of trials. Performance using either limb did not differ significantly. In animals receiving unilateral muscimol infusion, reaching and grasping using the limb ipsilateral to the infusion were similar to controls. The limb contralateral to infusion showed significant increases in systematic and variable reaching end-point errors, often requiring subsequent corrective movements to contact the meat. Grasping occurred on only 14.8% of trials, replaced on most trials by raking without distal movements. Compensatory adjustments in reach length and angle, to maintain end-point accuracy as movements were started from a more lateral position, were less effective using the contralateral limb than ipsilateral limb. With bilateral inactivations, the form of reaching acid grasping impairments was identical to that produced by unilateral inactivation, but the magnitude of the reaching impairments was less. We discuss these results in terms of the differential effects of unilateral and bilateral inactivation on corticospinal tract development. We also investigated the degree to which these prehension impairments after unilateral blockade reflect control by each hemisphere. In animals that had received unilateral blockade b

关键词：年龄因素条件反射(心理学)/生理学关键期(心理学) 摄食行为/生理学前肢/生理学功能偏侧化/生理学 GABA激动剂/药理学运动皮质/药物作用运动皮质/生长和发育运动皮质/生理学运动技能/药物作用运动技能/生理学蝇蕈醇/药理学精神运动性行为/生理学躯体感觉皮质/药物作用躯体感觉皮质/生长和发育躯体感觉皮质/生理学空间知觉/生理学动物猫

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Neonatal lead exposure impairs development of rodent barrel field cortex

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2000年第10期97卷 5540-5545页

作者： Wilson, MA Johnston, MV Goldstein, GW Blue, ME Johns Hopkins Univ Kennedy Krieger Inst Baltimore MD 21205 USA Johns Hopkins Univ Dept Neurol Baltimore MD 21205 USA Johns Hopkins Univ Dept Pediat Baltimore MD 21205 USA Johns Hopkins Univ Dept Environm Hlth Sci Baltimore MD 21205 USA

Childhood exposure to low-level lead can permanently reduce intelligence, but the neurobiologic mechanism for this effect is unknown. We examined the impact of lead exposure on the development of cortical columns, using the rodent barrel field as a model. In all areas of mammalian neocortex, cortical columns constitute a fundamental structural unit subserving information processing. Barrel field cortex contains columnar processing units with distinct clusters of layer IV neurons that receive sensory input from individual whiskers. In this study, rat pups were exposed to 0, 0.2, 1, 1.5, or 2 g/liter lead acetate in their dam's drinking water from birth through postnatal day 10. This treatment, which coincides with the development of segregated columns in the barrel field, produced blood lead concentrations from 1 to 31 mu g/dl. On postnatal day 10, the area of the barrel field and of individual barrels was measured. A dose-related reduction in barrel field area was observed (Pearson correlation = -0.740;P < 0.001);mean barrel field area in the highest exposure group was decreased 12% Versus controls. individual barrels in the physiologically more active caudoventral group were affected preferentially Total cortical area measured in the same sections was not altered significantly by lead exposure. These data support the hypothesis that lead exposure may impair the development of columnar processing units in immature neocortex. We demonstrate that low levers of blood lead, in the range seen in many impoverished inner-city children, cause structural alterations in a neocortical somatosensory map.

关键词：投药口服动物新生剂量效应关系药物电子传递复合物Ⅳ/分析泌乳铅/血液铅中毒/病理生理学有机金属化合物/投药和剂量有机金属化合物/毒性大鼠 Long-Evans 大鼠 Sprague-Dawley 受体 AMPA/分析受体谷氨酸/分析受体亲代谢性谷氨酸盐/分析躯体感觉皮质/药物作用躯体感觉皮质/生长和发育躯体感觉皮质/病理学触须/神经支配动物女(雌)性大鼠

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Experimental microgyri disrupt the barrel field pattern in rat somatosensory cortex

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CEREBRAL CORTEX 1999年第7期9卷 733-744页

作者： Jacobs, KM Mogensen, M Warren, E Prince, DA Stanford Univ Med Ctr Dept Neurol & Neurol Sci Stanford CA 94305 USA

Transcranial freeze lesions in neonatal rat pups produce microgyri and adjacent epileptogenic regions of neocortex that can be used to model human polymicrogyria. The hypothesis that the presence of microgyri is associated with abnormal cortical organization occurring within as well as adjacent to the microgyri was tested by creating microgyri within the face representation of somatosensory cortex. Microgyri were associated with a widespread disruption of the stereotypic whisker barrel field pattern delineated with cytochrome oxidase (CO) staining. CO-stained patches resembling barrel hollows were absent within the microgyrus, and were abnormally shaped and distributed outside of the microgyrus. Adjacent Nissl- or acetylcholinesterase-stained sections demonstrated that both cell clusters and thalamocortical afferents contributed to the abnormally organized paramicrogyral zone identified in GO-stained sections. Field potential recordings showed that this region of heavy CO staining corresponded to the epileptogenic zone adjacent to the microgyrus. Results support our hypothesis that the epileptogenic paramicrogyral zone develops an abnormal organization of cell clusters and thalamocortical projections that could contribute to epileptogenesis in the paramicrogyral zone.

关键词：年龄因素动物新生脑图去神经支配疾病模型动物电生理学癫痫/病理学癫痫/病理生理学冷冻大鼠 Sprague-Dawley 躯体感觉皮质/生长和发育躯体感觉皮质/病理学躯体感觉皮质/病理生理学触须/神经支配触须/生理学动物大鼠

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Serotonin depletion and barrel cortex development: Impact of growth impairment vs. serotonin effects on thalamocortical endings

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CEREBRAL CORTEX 2000年第2期10卷 181-191页

作者： Persico, AM Altamura, C Calia, E Puglisi-Allegra, S Ventura, R Lucchese, F Keller, F LUCBM Neurosci Lab Dept Physiol I-00155 Rome Italy LUCBM Serv Neurol I-00155 Rome Italy Univ Roma La Sapienza Dept Psychol Rome Italy

Converging evidence supports a role of serotonin (5-hydroxytryptamine;5-HT) in barrel cortex development. Systemic administration of 5-HT-depleting drugs reduces cross-sectional whisker barrel areas in the somatosensory cortex (SSC) of neonatal rats. Here we assess the relative impact on barrel pattern formation of (i) 5-HT depletion and (ii) decreased brain growth, which is often associated with pharmacological 5-HT depletion, by comparing the effects of 5-HT-depleting drugs with those of reduced protein intake. Left hemisphere 5-HT levels in the SSC and right hemisphere whisker barrel areas were assessed at postnatal day 6 (P6) in the same animal following injection of p-chloroamphetamine (PCA) or p-chlorophenylalanine (PCPA) at PO. Both drugs significantly reduced cortical 5-HT content and mean barrel areas at P6, but also body and brain growth. Differences in brain weight accounted for 84.4 % of the variance in barrel size, with negligible contributions by cortical 5-HT content. PCPA-treated animals sacrificed at P14 yielded similar trends, albeit less pronounced. Finally, reduced protein intake resulted in lower body weight and cortical 5-HT levels at P6, but yielded no change in brain weight or mean barrel area. Barrel formation therefore appears markedly less sensitive to 5-HT depletion per se than to drug-induced growth impairment.

关键词：衰老动物新生体重/药物作用脑/解剖学和组织学芬克洛宁/药理学羟基吲哚乙酸/代谢器官测量/药物作用大鼠近交Lew 血清素/代谢躯体感觉皮质/药物作用躯体感觉皮质/生长和发育躯体感觉皮质/生理学触须/神经支配 p-氯苯丙胺/药理学动物大鼠

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REHABILITATION FOLLOWING EARLY MALNUTRITION IN THE RAT - BODY-WEIGHT, BRAIN SIZE, AND CEREBRAL-CORTEX DEVELOPMENT

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BRAIN RESEARCH 1979年第1期169卷 121-138页

作者： ANGULOCOLMENARES, AG VAUGHAN, DW HINDS, JW UNIV CARABOBO NUCLEO ARAGUA FAC CIENCIAS SALUD MARACAY VENEZUELA BOSTON UNIV SCH MED DEPT ANAT BOSTON MA 02118 USA

Sprague-Dawley rats were malnourished by giving their mothers an 8% casein diet starting at day 10 of gestation, while controls were fed a 24% casein diet. Starting at postnatal day 20 (P20), rehabilitation of the malnourished animals was attempted by: feeding both mother and young a 24% casein diet, leaving the pups with their mothers until they were 40 days old, and reducing the litter size from 8-4 pups. Observations were made on aldehyde-perfused tissue from animals 20, 40 and 70 days old. The somatosensory cortex from 1 hemisphere was embedded in Araldite, and that from the other side was processed for Golgi staining. At 20 days of age the body weight of the malnourished animals was 21% that of the controls, but at 70 days it was no longer different. The anterior-posterior length, the width, and the height of the cerebral hemispheres were also significantly reduced at P20, but the differences had disappeared by P70. The thickness of area 3 of the cerebral cortex was measured in 1 .mu.m sections. It was significantly reduced in the malnourished animals at P20, but at P40, following rehabilitation, the difference was no longer statistically significant. In tangential 1 .mu.m sections the fraction of the volume of tissue occupied by neuropil was measured in layers II through IV. At P20 it was significantly reduced only in the upper half of layers II/III of the malnourished animals;at P40 this difference was no longer present. The mean volume of upper layer II/III cell bodies was estimated to be significantly reduced in the experimental animals at P20 but not at P40. In the Golgi preparations, pyramidal cells in upper layer II/III were studied. Their estimated volume, and the thickness of their basal dendrites, was significantly reduced in the 20 day malnourished animals, but not in the rehabilitated animals. Animals severely malnourished until 20 days of age can reach normal body weight and attain cerebral hemispheres of normal size when proper nutrition is provid

关键词：动物新生体重细胞计数细胞分化大脑皮质/细胞学大脑皮质/生长和发育树突/超微结构食品剥夺神经元/细胞学器官测量蛋白质能量营养不良/康复躯体感觉皮质/生长和发育动物女(雌)性妊娠大鼠

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Partial forelimb deafferentation during early ontogenesis in rats increases somatosensory cortex neuron reactivity

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Neuroscience and Behavioral Physiology 1999年第2期29卷 181-183页

作者： Sitnikova, E.Yu. Institute of Higher Nervous Activity and Neurophysiology Russian Academy of Sciences Moscow Russian Federation

The aim of the present work was to establish whether limitation of sensory input during early ontogenesis can really actualize sensory functions. The effects of partial forelimb denervation on the formation of responses by neurons in the somatosensory zone of the cortex were studied in the areas representing the hindpaws, stimuli being applied to the contralateral sciatic nerve.

关键词：去神经支配诱发电位躯体感觉/生理学前肢/生理学神经元传入/生理学大鼠 Wistar 坐骨神经/生理学躯体感觉皮质/生长和发育躯体感觉皮质/生理学动物大鼠

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The role of α-CaMKII autophosphorylation in neocortical experience-dependent plasticity

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NATURE NEUROSCIENCE 2000年第9期3卷 911-918页

作者： Glazewski, S Giese, KP Silva, A Fox, K Cardiff Univ Cardiff Sch Biosci Cardiff CF10 3US S Glam Wales UCL Dept Anat & Dev Biol London WC1E 6BT England Univ Calif Los Angeles Dept Neurobiol Los Angeles CA 90095 USA Univ Calif Los Angeles Dept Psychiat & Psychol Los Angeles CA 90095 USA

Calcium/calmodulin kinase type II (CaMKII) is a major postsynaptic density protein. CaMKII is postulated to act as a 'molecular switch', which, when triggered by a transient rise in calcium influx, becomes active for prolonged periods because of its ability to autophosphorylate. We studied experience-dependent plasticity in the barrel cortex of mice carrying a point mutation of the alpha -CaMKII gene (T286A), which abolishes this enzyme's ability to autophosphorylate. Plasticity was prevented in adult and adolescent mice homozygous for the mutation, but was normal in heterozygotes and wild-type littermates. These results provide evidence that the molecular switch hypothesis is valid for neocortical experience-dependent plasticity.

关键词：年龄因素杂合子学习/生理学机械感受器/细胞学机械感受器/代谢小鼠基因敲除新皮质/细胞学新皮质/生长和发育新皮质/代谢神经元可塑性/生理学神经元/细胞学神经元/代谢磷酰化点突变/生理学躯体感觉皮质/细胞学躯体感觉皮质/生长和发育躯体感觉皮质/代谢突触/代谢突触/超微结构触须/神经支配触须/生理学动物小鼠

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