Deficiency of Thyroid Hormone Reduces Voltage-Gated Na Currents as Well as Expression of Na/K-ATPase in the Mouse Hippocampus.

Mice lacking functional thyroid follicular cells, mice, die early postnatally, making them suitable models for extreme hypothyroidism. We have previously obtained evidence in postnatal rat neurons, that a down-regulation of Na-current density could explain the reduced excitability of the nervous system in hypothyroidism. If such a mechanism underlies the development of coma and death in severe hypothyroidism, mice should show deficits in the expression of Na currents and potentially also in the expression of Na/K-ATPases, which are necessary to maintain low intracellular Na levels.

Mechanistic flexibility of the retrosplenial cortex enables its contribution to spatial cognition.

The retrosplenial cortex (RC) is a brain structure crucial for spatial navigation and memory. It contains neurons such as head direction cells, border cells, as well as other cells supporting spatial and contextual encoding. How such complex and diverse neuronal properties are generated by RC microcircuitry and how they jointly orchestrate subsequent behavior remains enigmatic.

Orchestration of Hippocampal Information Encoding by the Piriform Cortex.

The hippocampus utilizes olfactospatial information to encode sensory experience by means of synaptic plasticity. Odor exposure is also a potent impetus for hippocampus-dependent memory retrieval. Here, we explored to what extent the piriform cortex directly impacts upon hippocampal information processing and storage.

Differential expression patterns of sodium potassium ATPase alpha and beta subunit isoforms in mouse brain during postnatal development.

The sodium potassium ATPase (Na/K ATPase) is essential for the maintenance of a low intracellular Na and a high intracellular K concentration. Loss of function of the Na/K ATPase due to mutations in Na/K ATPase genes, anoxic conditions, depletion of ATP or inhibition of the Na/K ATPase function using cardiac glycosides such as digitalis, causes a depolarization of the resting membrane potential. While in non-excitable cells, the uptake of glucose and amino acids is decreased if the function of the Na/K ATPase is compromised, in excitable cells the symptoms range from local hyper-excitability to inactivating depolarization.

In the Piriform Cortex, the Primary Impetus for Information Encoding through Synaptic Plasticity Is Provided by Descending Rather than Ascending Olfactory Inputs.

Information encoding by means of persistent changes in synaptic strength supports long-term information storage and memory in structures such as the hippocampus. In the piriform cortex (PC), that engages in the processing of associative memory, only short-term synaptic plasticity has been described to date, both in vitro and in anesthetized rodents in vivo. Whether the PC maintains changes in synaptic strength for longer periods of time is unknown: Such a property would indicate that it can serve as a repository for long-term memories.

Involvement of Dopamine D1/D5 and D2 Receptors in Context-Dependent Extinction Learning and Memory Reinstatement.

Dopamine contributes to the regulation of higher order information processing and executive control. It is important for memory consolidation processes, and for the adaptation of learned responses based on experience. In line with this, under aversive learning conditions, application of dopamine receptor antagonists prior to extinction result in enhanced memory reinstatement.

Beta-adrenergic receptors support attention to extinction learning that occurs in the absence, but not the presence, of a context change.

The noradrenergic (NA)-system is an important regulator of cognitive function. It contributes to extinction learning (EL), and in disorders where EL is impaired NA-dysfunction has been postulated. We explored whether NA acting on beta-adrenergic-receptors (β-AR), regulates EL that depends on context, but is not fear-associated.

Regulation of neuronal excitability by release of proteins from glial cells.

Effects of glial cells on electrical isolation and shaping of synaptic transmission between neurons have been extensively studied. Here we present evidence that the release of proteins from astrocytes as well as microglia may regulate voltage-activated Na(+) currents in neurons, thereby increasing excitability and speed of transmission in neurons kept at distance from each other by specialized glial cells. As a first example, we show that basic fibroblast growth factor and neurotrophin-3, which are released from astrocytes by exposure to thyroid hormone, influence each other to enhance Na(+) current density in cultured hippocampal neurons.

Synaptic strength at the temporoammonic input to the hippocampal CA1 region in vivo is regulated by NMDA receptors, metabotropic glutamate receptors and voltage-gated calcium channels.

The hippocampal CA1 region receives cortical information via two main inputs: directly via the perforant (temporoammonic) path (pp-CA1 synapse) and indirectly via the tri-synaptic pathway. Although synaptic plasticity has been reported at the pp-CA1 synapse of freely behaving animals, the mechanisms underlying this phenomenon have not been investigated. Here, we explored whether long-term potentiation (LTP) at the pp-CA1 synapse in freely behaving rats requires activation of N-methyl-d-aspartate receptors (NMDAR) and L-type voltage-gated calcium channels (VGCCs).

The metabotropic glutamate receptor, mGlu5, is required for extinction learning that occurs in the absence of a context change.

The metabotropic glutamate (mGlu) receptors and, in particular, mGlu5 are crucially involved in multiple forms of synaptic plasticity that are believed to underlie explicit memory. MGlu5 is also required for information transfer through neuronal oscillations and for spatial memory. Furthermore, mGlu5 is involved in extinction of implicit forms of learning.

Spatial representations of place cells in darkness are supported by path integration and border information.

Effective spatial navigation is enabled by reliable reference cues that derive from sensory information from the external environment, as well as from internal sources such as the vestibular system. The integration of information from these sources enables dead reckoning in the form of path integration. Navigation in the dark is associated with the accumulation of errors in terms of perception of allocentric position and this may relate to error accumulation in path integration.

Place field stability requires the metabotropic glutamate receptor, mGlu5.

The metabotropic glutamate (mGlu) receptors are critically involved in enabling the persistency of forms of synaptic plasticity that are believed to underlie hippocampus-dependent memory. These receptors and in particular, mGlu5, are also required for hippocampus-dependent learning and memory. In the hippocampus, synaptic plasticity is one of the mechanisms by which spatial information may be represented.

Spatial olfactory learning contributes to place field formation in the hippocampus.

Spatial encoding in the hippocampus is multifactorial, and it is well established that metric information about space is conferred by place cells that fire when an animal finds itself in a specific environmental location. Visuospatial contexts comprise a key element in the formation of place fields. Nevertheless, hippocampus does not only use visual cues to generate spatial representations.

The temporoammonic input to the hippocampal CA1 region displays distinctly different synaptic plasticity compared to the Schaffer collateral input in vivo: significance for synaptic information processing.

In terms of its sub-regional differentiation, the hippocampal CA1 region receives cortical information directly via the perforant (temporoammonic) path (pp-CA1 synapse) and indirectly via the tri-synaptic pathway where the last relay station is the Schaffer collateral-CA1 synapse (Sc-CA1 synapse). Research to date on pp-CA1 synapses has been conducted predominantly in vitro and never in awake animals, but these studies hint that information processing at this synapse might be distinct to processing at the Sc-CA1 synapse. Here, we characterized synaptic properties and synaptic plasticity at the pp-CA1 synapse of freely behaving adult rats.

Spatial olfactory learning facilitates long-term depression in the hippocampus.

Recently, it has emerged that visual spatial exploration facilitates synaptic plasticity at different synapses within the trisynaptic network. Particularly striking is the finding that visuospatial contexts facilitate hippocampal long-term depression (LTD), raising the possibility that this form of plasticity may be important for memory formation. It is not known whether other sensory modalities elicit similar permissive effects on LTD.

Differentiation in the protein synthesis-dependency of persistent synaptic plasticity in mossy fiber and associational/commissural CA3 synapses in vivo.

Long-term potentiation (LTP) and long-term depression (LTD) are two mechanisms involved in the long-term storage of information in hippocampal synapses. In the hippocampal CA1 region, the late phases of LTP and LTD are protein-synthesis dependent. In the dentate gyrus, late-LTP but not LTD requires protein synthesis.

Brief environmental enrichment elicits metaplasticity of hippocampal synaptic potentiation in vivo.

Long-term environmental enrichment (EE) elicits enduring effects on the adult brain, including altered synaptic plasticity. Synaptic plasticity may underlie memory formation and includes robust (>24 h) and weak (<2 h) forms of long-term potentiation (LTP) and long-term depression (LTD). Most studies of the effect of EE on synaptic efficacy have examined the consequences of very prolonged EE-exposure.

Intrinsic, light-independent and visual activity-dependent mechanisms cooperate in the shaping of the field response in rat visual cortex.

Do light intensity and behavioral state regulate synaptic plasticity in the visual cortex? We have shown previously that synaptic transmission in the visual cortex oscillates between elevated and depressed levels in accordance with the diurnal light-dark cycle. In this study, we examined the role of intrinsic, light-independent, and visual activity-driven sensory information on the field response during diurnal fluctuations, and examined the plasticity properties of the visual cortex under both conditions. Recordings were obtained from layer 2/3 of the primary visual cortex, of adult freely moving Long Evans rats, after stimulation of the dorsal lateral geniculate nucleus.

The adult visual cortex expresses dynamic synaptic plasticity that is driven by the light/dark cycle.

Experimental evidence derived from in vitro studies suggests that synaptic plasticity may be involved in information processing in the adult sensory cortex. Here, we demonstrate, for the first time, that synaptic plasticity that endures for >24 h can be elicited in the visual cortex of freely moving adult rats. Both long-term potentiation (LTP) and long-term depression (LTD) were evoked in layer 2/3 of the primary visual cortex after stimulation of the dorsal lateral geniculate nucleus.

Creative thinking in schizophrenia: the role of executive dysfunction and symptom severity.

Introduction: This study examines the notion of enhanced creative thinking in schizophrenia and determines the mediating role of executive dysfunction and symptom severity in this relationship.

Method: Patients with chronic schizophrenia (n=28) were assessed on varied facets of creative cognition and standard tests of executive control relative to matched healthy control participants (n=18).

Results: Multivariate analyses revealed poorer performance by the patient group across almost all creative and executive function measures, except in the ability to be unconstrained by the influence of restrictive examples.

Dopamine D1/D5 receptors gate the acquisition of novel information through hippocampal long-term potentiation and long-term depression.

Hebbian learning models require that neurons are able to both strengthen and weaken their synaptic connections. Hippocampal synaptic plasticity, in the form of long-term potentiation (LTP) and long-term depression (LTD), has been implicated in both spatial memory formation as well as novelty acquisition. In addition, the ventral tegmental area-hippocampal loop has been proposed to control the entry of information into long-term memory, whereas the dopaminergic system is believed to play an important role in information acquisition and synaptic plasticity.

Creative thinking in adolescents with attention deficit hyperactivity disorder (ADHD).

A widened attentional focus, that is typically associated with ADHD, has been postulated to be accompanied by enhanced creative ability. However, creativity has been only limitedly examined in ADHD. Performance across several creativity measures were investigated in three groups: adolescents with ADHD, those with conduct disorder, and a healthy control sample.

Conceptual expansion and creative imagery as a function of psychoticism.

The ability to be creative is often considered a unique characteristic of conscious beings and many efforts have been directed at demonstrating a relationship between creativity and the personality construct of psychoticism. The present study sought to investigate this link explicitly by focusing on discrete facets of creative cognition, namely the originality/novelty dimension and the practicality/usefulness dimension. Based on Eysenck's conceptualisation of psychoticism as being characterised by an overinclusive cognitive style, it was expected that higher levels of psychoticism would accompany a greater degree of conceptual expansion and elevated levels of originality in creative imagery, but would be unrelated to the practicality/usefulness of an idea.

The metabotropic glutamate receptor, mGluR5, is a key determinant of good and bad spatial learning performance and hippocampal synaptic plasticity.

Hippocampal synaptic plasticity is expressed to very different extents in distinct rat strains in vivo. This may correlate with differences in learning ability. We investigated whether the metabotropic glutamate receptor mGluR5 contributes to differences in long-term potentiation (LTP) and learning in freely moving hooded Lister (HL) and Wistar rats.

The 5-hydroxytryptamine4 receptor exhibits frequency-dependent properties in synaptic plasticity and behavioural metaplasticity in the hippocampal CA1 region in vivo.

Long-term plasticity, in the forms of long-term depression (LTD) and long-term potentiation (LTP), of synaptic transmission are thought to underlie memory. Biogenic amino acids modulate the expression of LTD and LTP. The serotonergic 5-hydroxytryptamine4 (5-HT4) receptor has been shown to influence learning and memory.