Hippocampal and cortico-striatal contributions to spatial learning: early versus late Morris water maze learning

Normal 0 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}The ability to learn new skills or habitsas a result of practice is one of the most distinguished features of biologicalsystems. Neuroplastic processes and changes in synaptic connections arephenomena at the systems and molecular neuroscience level enabling differentforms of learning and memory. In this dissertation we aimed to elucidate someof these neuroplastic mechanisms associated with early and late complex watermaze learning. The main goal was to visualize possible network activity betweendifferent brain regions for which independent involvement in water mazelearning was already established a priori.The major part of this study comprisedthe quantitative analysis of immediate early gene expression levels in thehippocampus (CA1 and CA3), striatum (DMS, sDMS and DLS) and prefrontal cortex(aCC, PL and IL) by means of in situhybridization experiments for the molecular activity marker zif268 and the molecular plasticitymarkers Homer1a and arc. Through these analyses we soughtto identify learning phase-related differences in the contributions of thesedistinct subregions of the brain. Furthermore, this IEG imaging approach alsoallowed us to characterize the nature of interactions between subregions in theintact mouse brain. With respect to the hippocampus, surface biotinylationassays in acute brain slices (ASBA) combined with Western analysis enabled usto measure modifications in the membrane expression of specific cell surfaceproteins.In the corticostriatal system, we have found synergisticactivity dynamics (zif268 expression)over the course of learning in the (superior) dorsomedial striatum, theprelimbic and the anterior cingulate cortex, with these regions being mostactive during goal-directed early learning. Also, parallel dynamics in activitywere found in the dorsolateral striatum and infralimbic cortex, with bothregions mediating habitual water maze performance. During early taskacquisition, these two corticostriatal circuits were shown to develop simultaneously.However, arc expression levelssuggested that the goal-directed corticostriatal loop controlled behavioraloutput during early spatial learning. Upon overtraining, we demonstrated ashift in behavioral control to the habitual corticostriatal circuit. Withrespect to the hippocampal system, we demonstrated a continuous activation (zif268 expression) during water mazeperformance in CA1, not CA3. However, task-specific engagement in CA1 was only foundduring the goal-directed early learning phase. Since ASBA analysis onlydetected modifications of the NMDAR subunit composition during early learning,we suggest that the hippocampus indeed mediates goal-directed early learning incorrespondence with the corticostriatal circuit comprising the (superior)dorsomedial striatum, the prelimbic and the anterior cingulate cortex.Table of Contents i List of Abbreviations 1 Aim of the study 6 Chapter 1: Learning and memory 10 1. Different learning and memory systems dependent on the type of processed information 10 2. Learning and memory at cellular level 12 2.1. Activity-dependent synaptic plasticity 12 2.2. The molecular and cellular mechanisms substantiating synaptic plasticity and memory consolidation 13 2.2.1. NMDAR-dependent LTP 14 2.2.2. NMDAR-dependent LTD 19 3. Learning-related brain structures/systems involved in the Morris water maze task 21 3.1. The hippocampal system 23 3.1.1 Anatomical structure of the hippocampal system 23 3.1.2 Information transduction pathways of the hippocampal system 23 3.1.3 Memory processing functions of the hippocampal system 25 3.2. The cortico-striatal system 32 3.2.1 Anatomical structure of the basal ganglia 32 3.2.2 Information transduction pathways of the basal ganglia 33 3.2.3 Memory processing functions of the cortico-striatal system 35 Chapter 2: Materials and methods 41 1. Animals 41 2. Behavioral training procedures 41 2.1. Morris water maze training 41 2.2. Experimental conditions 42 2.3. Statistics 44 3. Semi-quantitative in situ hybridization (ISH) to determine zif268, arc, H1a and Pcp4 expression levels 45 3.1. Subjects 45 3.2. Tissue preparation 45 3.3. In situ hybridization 45 3.4. Regions of interest (ROIs) 46 3.4.1. The hippocampus (Learning-related changes in the hippocampus are discussed in chapter 3 and 4) 46 3.4.2. The striatum and the anterior cingulate cortex (aCC) (Learning-related changes in the striatum and the aCC are discussed in chapter 4) 48 3.4.3. The medial prefrontal cortex (Learning-related changes in the medial prefrontal cortex are discussed in chapter 4) 49 3.5. Quantitative analysis 49 3.6. Statistics 50 3.7. Corticosterone levels 51 4. Acute slice biotinylation assay (ASBA) to determine the optical density of glutamate receptor subunits in the hippocampal plasma membrane 52 4.1. Subjects 52 4.2. Tissue preparation 52 4.3. Acute slice biotinylation assay 53 4.4. Isolation of membrane proteins 53 4.5. Western Blotting 54 4.6. Quantitative analysis 55 4.7. Statistics 55 Chapter 3: Hippocampal contributions to spatial learning: early versus late Morris water maze learning 56 1. Introduction 56 2. Materials and methods 58 3. Results 59 3.1. Behavioral learning profile 59 3.2. Initial acquisition but not consolidation of spatial memory is reflected in changed hippocampal IEG expression patterns 60 3.2.1 Zif268 expression 60 3.2.2 Homer1a (H1a) expression 61 3.3. Correlation between IEG expression and performance 62 3.4. Glutamate receptor subunit expression on the plasma membrane of hippocampal cells 63 4. Discussion 66 4.1. Differential zif268 and H1a expression patterns in CA1 and CA3 over the course of MWM training 66 4.2. No changes in the total number of AMPARs inserted into the plasma membrane of hippocampal cells upon MWM training 69 4.3. A constant number of NMDARs but an altered NMDAR subunit composition accompanies early spatial learning in the MWM 69 Chapter 4: Cortico-striatal contributions to spatial learning: early versus late Morris water maze learning 72 1. Introduction 72 2. Materials and methods 75 3. Results 76 3.1. Behavioral learning profile 76 3.2. Concomitant learning phase-specific changes of IEG expression in distinct cortico-striatal circuits enable mastering of MWM performance 77 3.2.1 The (superior) dorsomedial and dorsolateral striatum: goal-directed versus habitual learning 78 3.2.2 Interaction between the anterior cingulate and prelimbic prefrontal cortices and the (superior) dorsomedial striatum: goal-directed learning 84 3.2.3 Interaction between the infralimbic prefrontal cortex and the dorsolateral striatum: habitual learning 91 4. Discussion 93 4.1. The hippocampus and (superior) dorsomedial striatum versus the dorsolateral striatum: goal-directed versus habitual learning 93 4.1.1. The (superior) dorsomedial striatum versus the dorsolateral striatum: goal-directed versus habitual learning 93 So what about the dorsomedial striatum? 95 This observation raised the question whether the dorsomedial and dorsolateral striatal subdivisions both contributed to the early learning phase and what the functional specificity was of each subregion? 97 If both systems develop in parallel during early learning, how are they interacting to control behavior? 99 If the less energy consuming response strategy is already operational during early learning, why is it not controlling behavior? 100 4.1.2. The hippocampus and (superior) dorsomedial striatum: goal-directed learning 101 If both the hippocampus and the dorsomedial striatum are part of the same goal-directed circuit, what are their respective functions in relation to spatial learning and how do they interact? 101 If not the acquisition of spatial information, then what is the function of the dorsomedial striatum in spatial learning? 102 4.2. Interaction between the anterior cingulate and prelimbic prefrontal cortices and the (superior) dorsomedial striatum: goal-directed learning 103 In relation to the dorsomedial striatum and hippocampus (§ 4.1.2.), what is the specific function of the prelimbic and anterior cingulate prefrontal cortical areas during goal-directed early spatial learning? What is their contribution to action-outcome contingency learning, the dominant type of information processing governed by the associative corticostriatal circuit during the early stage of task acquisition? And, what is the functional implication of the distinct hippocampal innervation? 105 If the PL is not the locus of action-outcome encoding, then what is its function in goal-directed learning? 105 How does the prelimbic cortex contribute to path planning? 107 How does this theory fit into the context of our experimental water maze setup? 108 If both strategies continuously exist in parallel, why is the anterior cingulate cortex not active anymore during late learning to guide effort-based decision making and establish a bias towards response learning? Thus, why is activation of the anterior cingulate cortex no longer required after extensive training? 109 4.3. Interaction between the infralimbic prefrontal cortex and the dorsolateral striatum: habitual learning 110 4.4. Interaction between the prelimbic and infralimbic cortex: goal-directed versus habitual learning 112 How is the infralimbic cortex enabling the habitual system to override the goal-directed system? 112 Chapter 5: General discussion and future perspectives 114 1. Concluding remarks about the differential contribution of distinct cortical and subcortical regions to Morris water maze learning: from goal-directed to habitual control 114 2. Parallel findings from within the KU Leuven consortium 117 3. What type of navigation strategy actually reflects goal-directed and habitual performance? 118 4. Are free-swimming controls a suitable control condition? Are their alternatives? 120 5. Future perspectives 121 5.1. Medial prefrontal cortex: prelimbic and infralimbic cortex 121 5.2. ASBA AMPA1 122 Summary 124 Samenvatting 126 Appendix 1 128 List of References 131 List of Publications 160nrpages: 164status: publishe

Comparison of the spatial-cognitive functions of dorsomedial striatum and anterior cingulate cortex in mice.

Neurons in anterior cingulate cortex (aCC) project to dorsomedial striatum (DMS) as part of a corticostriatal circuit with putative roles in learning and other cognitive functions. In the present study, the spatial-cognitive importance of aCC and DMS was assessed in the hidden-platform version of the Morris water maze (MWM). Brain lesion experiments that focused on areas of connectivity between these regions indicated their involvement in spatial cognition. MWM learning curves were markedly delayed in DMS-lesioned mice in the absence of other major functional impairments, whereas there was a more subtle, but still significant influence of aCC lesions. Lesioned mice displayed impaired abilities to use spatial search strategies, increased thigmotaxic swimming, and decreased searching in the proximity of the escape platform. Additionally, aCC and DMS activity was compared in mice between the early acquisition phase (2 and 3 days of training) and the over-trained high-proficiency phase (after 30 days of training). Neuroplasticity-related expression of the immediate early gene Arc implicated both regions during the goal-directed, early phases of spatial learning. These results suggest the functional involvement of aCC and DMS in processes of spatial cognition that model associative cortex-dependent, human episodic memory abilities

AMIGO2 mRNA expression in hippocampal CA2 and CA3a

AMIGO2, or amphoterin-induced gene and ORF (open reading frame) 2, belongs to the leucine-rich repeats and immunoglobulin superfamilies. The protein is a downstream target of calcium-dependent survival signals and, therefore, promotes neuronal survival. Here, we describe the mRNA distribution pattern of AMIGO2 throughout the mouse brain with special emphasis on the hippocampus. In the Ammon's horn, a detailed comparison between the subregional mRNA expression patterns of AMIGO2 and Pcp4 (Purkinje cell protein 4)--a known molecular marker of hippocampal CA2 (Cornu Ammonis 2)--revealed a prominent AMIGO2 mRNA expression level in both the CA2 and the CA3a (Cornu Ammonis 3a) subregion of the dorsal and ventral hippocampus. Since this CA2/CA3a region is particularly resistant to neuronal injury and neurotoxicity [Stanfield and Cowan (Brain Res 309(2):299–307 1984); Sloviter (J Comp Neurol 280(2):183–196 1989); Leranth and Ribak (Exp Brain Res 85(1):129–136 1991); Young and Dragunow (Exp Neurol 133(2):125–137 1995); Ochiishi et al. (Neurosci 93(3):955–967 1999)], we suggest that the expression pattern of AMIGO2 indeed fits with its involvement in neuroprotection.status: publishe

The cross-modal aspect of mouse visual cortex plasticity induced by monocular enucleation is age dependent

Monocular enucleation (ME) drastically affects the contralateral visual cortex, where plasticity phenomena drive specific adaptations to compensate for the unilateral loss of vision. In adult mice, complete reactivation of deprived visual cortex involves an early visually driven recovery followed by multimodal plasticity 3 to 7 weeks post ME (Van Brussel et al. [2011] Cereb. Cortex 21:2133-2146). Here, we specifically investigated the age dependence of the onset and the exact timing of both ME-induced reactivation processes by comparing cortical activity patterns of mice enucleated at postnatal day (P) 45, 90, or 120. A swifter open-eye potentiated reactivation characterized the binocular visual cortex of P45 mice. Nevertheless, even after 7 weeks, the reactivation remained incomplete, especially in the monocular cortex medial to V1. In comparison with P45, emergent cross-modal participation was demonstrated in P90 animals, although robust reactivation similar to enucleated adults (P120) was not achieved yet. Concomitantly, at 7 weeks post ME, somatosensory and auditory cortex shifted from a hypoactive state in P45 to hyperactivity in P120. Thus, we provide evidence for a presensitive period in which gradual recruitment of cross-modal recovery upon long-term ME coincides with the transition from adolescence to adulthood in mice.status: publishe

Hippocampal involvement in the acquisition of relational associations, but not in the expression of a transitive inference task in mice

The hippocampus (HC) has been suggested to play a role in transitive inference (TI) on an ordered sequence of stimuli. However, it has remained unclear whether HC is involved in the expression of TI, or rather contributes to TI through its role in the acquisition of the sequence of elements (Frank, Rudy, & O'Reilly, 2003). Presently, the authors compared the effects of excitotoxic dorsal HC lesions in C57BL mice that received surgery before or after they were trained to discriminate between pairs of visual stimuli. Performance on a subsequent TI task was worse in mice with pretraining lesions than in those with posttraining lesions, which showed similar performance to shams without lesions. This indicates that HC is not involved in the expression of TI, but may merely help to acquire the underlying representations required for TI

Hippocampal involvement in the acquisition of relational associations, but not in the expression of a transitive inference task in mice

The hippocampus (HC) has been suggested to play a role in transitive inference (TI) on an ordered sequence of stimuli. However, it has remained unclear whether HC is involved in the expression of TI, or rather contributes to TI through its role in the acquisition of the sequence of elements (Frank, Rudy, & O’Reilly, 2003). Presently, the authors compared the effects of excitotoxic dorsal HC lesions in C57BL mice that received surgery before or after they were trained to discriminate between pairs of visual stimuli. Performance on a subsequent TI task was worse in mice with pretraining lesions than in those with posttraining lesions, which showed similar performance to shams without lesions. This indicates that HC is not involved in the expression of TI, but may merely help to acquire the underlying representations required for TI.status: publishe

MS imaging to analyse the transition from the early goal-directed phase to the late habituation phase of spatial learning in mice

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Impaired appetitively as well as aversively motivated behaviors and learning in PDE10A-deficient mice suggest a role for striatal signaling in evaluative salience attribution

Phosphodiesterase 10A (PDE10A) hydrolyzes both cAMP and cGMP, and is a key element in the regulation of medium spiny neuron (MSN) activity in the striatum. In the present report, we investigated the effects of targeted disruption of PDE10A on spatial learning and memory as well as aversive and appetitive conditioning in C57BL/6J mice. Because of its putative role in motivational processes and reward learning, we also determined the expression of the immediate early gene zif268 in striatum and anterior cingulate cortex. Animals showed decreased response rates in scheduled appetitive operant conditioning, as well as impaired aversive conditioning in a passive avoidance task. Morris water maze performance revealed not-motor related spatial learning and memory deficits. Anxiety and social explorative behavior was not affected in PDE10A-deficient mice. Expression of zif268 was increased in striatum and anterior cingulate cortex, which suggests alterations in the neural connections between striatum and anterior cingulate cortex in PDE10A-deficient mice. The changes in behavior and plasticity in these PDE10A-deficient mice were in accordance with the proposed role of striatal MSNs and corticostriatal connections in evaluative salience attribution.status: publishe

MS imaging and mass spectrometric synaptosome profiling identify PEP-19/pcp4 as a synaptic molecule involved in spatial learning in mice

The Morris water maze (MWM) spatial learning task has been demonstrated to involve a cognitive switch of action control to serve the transition from an early towards a late learning phase. However, the molecular mechanisms governing this switch are largely unknown. We employed MALDI MS imaging (MSI) to screen for changes in expression of small proteins in brain structures implicated in the different learning phases. We compared mice trained for 3days and 30days in the MWM, reflecting an early and a late learning phase in relation to the acquisition of a spatial learning task. An ion with m/z of 6724, identified as PEP-19/pcp4 by top-down tandem MS, was detected at higher intensity in the dorsal striatum of the late learning phase group compared with the early learning phase group. In addition, mass spectrometric analysis of synaptosomes confirmed the presence of PEP-19/pcp4 at the synapse. PEP-19/pcp4 has previously been identified as a critical determinant of synaptic plasticity in locomotor learning. Our findings extend PEP-19/pcp4 function to spatial learning in the forebrain and put MSI forward as a valid and unbiased research strategy for the discovery and identification of the molecular machinery involved in learning, memory and synaptic plasticity.publisher: Elsevier articletitle: MS imaging and mass spectrometric synaptosome profiling identify PEP-19/pcp4 as a synaptic molecule involved in spatial learning in mice journaltitle: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics articlelink: http://dx.doi.org/10.1016/j.bbapap.2016.10.007 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved.status: publishe

Protein Expression Dynamics during Postnatal Mouse Brain Development

We explored differential protein expression profiles in the mouse forebrain at different stages of postnatal development, including 10-day (P10), 30-day (P30), and adult (Ad) mice, by large-scale screening of proteome maps using two-dimensional difference gel electrophoresis. Mass spectrometry analysis resulted in the identification of 251 differentially expressed proteins. Most molecular changes were observed between P10 compared to both P30 and Ad. Computational ingenuity pathway analysis (IPA) confirmed these proteins as crucial molecules in the biological function of nervous system development. Moreover, IPA revealed Semaphorin signaling in neurons and the protein ubiquitination pathway as essential canonical pathways in the mouse forebrain during postnatal development. For these main biological pathways, the transcriptional regulation of the age-dependent expression of selected proteins was validated by means of in situ hybridization. In conclusion, we suggest that proteolysis and neurite outgrowth guidance are key biological processes, particularly during early brain maturation