Grace AA. Gating of information flow within the limbic system and the pathophysiology of schizophrenia. Brain Res Brain Res Rev 31: 330-341

Department of Neuroscience, University of Pittsburgh, 458 Crawford Hall, Pittsburgh, PA, USA.
Brain Research Reviews (Impact Factor: 5.93). 04/2000; 31(2-3):330-41. DOI: 10.1016/S0165-0173(99)00049-1
Source: PubMed


Although first thought of as a dopaminergic disorder, there is little direct evidence to support a primary pathology in the dopamine system as the etiological factor in schizophrenia. In contrast, evidence is amassing in support of a cortical disturbance in this disorder; one consequence of which is a disruption in the cortical regulation of subcortical dopamine systems. Our studies show that the hippocampus plays a major role in this interaction, in that, along with the dopamine system, it provides a gating influence over information flow from the prefrontal cortex at the level of the nucleus accumbens. Moreover, chemically-induced disruption of the development of the hippocampus and entorhinal cortex were found to lead to pathophysiological changes in these interactions in the limbic system of adult rats. Therefore, schizophrenia is proposed to be a developmentally-related disorder, in which disruption of the hippocampal influence over the limbic system during ontogeny results in a pathological alteration of corticoaccumbens interactions in the adult organism.

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    • "What modulates the state of the NAcc neurons is an extra input from the hippocampus (HPC). That is, only the NAcc neurons that are stimulated by HPC neurons enter their depolarized state and subsequently , fire upon receiving input from the PFC (Grace, 2000). For this reason, these neurons are said to implement a type of AND gate, since they fire only if they receive input from both the PFC and the HPC (Gisiger and Boukadoum, 2011). "
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    ABSTRACT: A central question in artificial intelligence is how to design agents capable of switching between different behaviors in response to environmental changes. Taking inspiration from neuroscience, we address this problem by utilizing artificial neural networks (NNs) as agent controllers, and mechanisms such as neuromodulation and synaptic gating. The novel aspect of this work is the introduction of a type of artificial neuron we call “switch neuron”. A switch neuron regulates the flow of information in NNs by selectively gating all but one of its incoming synaptic connections, effectively allowing only one signal to propagate forward. The allowed connection is determined by the switch neuron’s level of modulatory activation which is affected by modulatory signals, such as signals that encode some information about the reward received by the agent. An important aspect of the switch neuron is that it can be used in appropriate “switch modules” in order to modulate other switch neurons. As we show, the introduction of the switch modules enables the creation of sequences of gating events. This is achieved through the design of a modulatory pathway capable of exploring in a principled manner all permutations of the connections arriving on the switch neurons. We test the model by presenting appropriate architectures in nonstationary binary association problems and T-maze tasks. The results show that for all tasks, the switch neuron architectures generate optimal adaptive behaviors, providing evidence that the switch neuron model could be a valuable tool in simulations where behavioral plasticity is required.
    Neural Networks 11/2015; DOI:10.1016/j.neunet.2015.11.001 · 2.71 Impact Factor
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    • "In the last few decades there has been a particular focus on the malfunctioning of the sensory–motor system gating mechanisms that rely on the prefrontal cortex of those patients. The gating of information flow within the limbic system and the pathophysiology of schizophrenia has been assumed (Grace, 2000) and social deficits of schizophrenia (emotional processing, social perception, emotion recognition, etc.) could be linked to it. Thus, higher stress levels could affect sensory input. "
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    ABSTRACT: It is known that patients with schizophrenia show a deficiency in the prepulse inhibition reflex (PPI). These patients display abnormalities in autonomic nervous system and hypothalamic-pituitary-adrenal function and may have an altered sensitivity to stress. To date, no studies have been carried out to determine the effect of acute stress on the PPI. We investigated whether there was a differential response in reactivity to acute stress caused by the socially evaluated cold-pressor test (SECPT) in a sample of 58 chronic male patients with schizophrenia and 28 healthy control subjects. PPI, salivary cortisol and heart rate (HR) were measured. The patients were evaluated in two sessions (with and without the SECPT) 72h apart and basal measurements were carried out and 30min post-startle probe. We found an increase in salivary cortisol levels and the HR with SECPT condition in both groups and a significantly lower PPI% in patients with schizophrenia. The most relevant findings of this study are that the impairment of the PPI is increased by stress. Stress-induced increase in cortisol in both groups, mainly in healthy control group which allows us to hypothesize that at least such deterioration may be due to the hypercortisolemia caused by the SECPT. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
    06/2015; 228(3). DOI:10.1016/j.psychres.2015.05.097
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    • "It has been reported that memories of fearful experiences can lead to pathogenic conditions such as anxiety and phobias (Orsini & Maren, 2012). According to previous researches, stimulation of the hippocampus with NMDA may disrupt particular hippocampal functions (Bast & Feldon, 2003; Berke & Eichenbaum, 2001), and impair processing of sensory stimuli, which is the core deficit in neuropsychiatric disorders such as schizophrenia and anxiety disorders (Bast & Feldon, 2003; Benes, 2000; Grace, 2000). Previous reports in animal models have also shown that intra-VH infusions of NMDA agonists increase locomotor activity (Bast, Zhang & Feldon, 2001; Swerdlow et al., 2001), and their antagonists decrease level of anxiety (Rezvanfard, Zarrindast & Bina, 2009). "
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    ABSTRACT: Introduction: In this study, we investigated the role of N-Methyl-D-Aspartate (NMDA) receptors in the ventral hippocampus (VH) and their possible interactions with GABA A system on anxiety-like behaviors. Methods: We used an elevated-plus maze test (EPM) to assess anxiety-like behaviors and locomotor activity in male Wistar rats. Results: The results showed that intra-VH infusions of different doses of NMDA (0.25 and 0.5 µg/rat) increased locomotor activity, and also induced anxiolytic-like behaviors, as revealed by a tendency to increase percentage of open arm time (%OAT), and a significant increase in percentage of open arm entries (%OAE). The results also showed that intra-VH infusions of muscimol (0.5 and 1 µg/rat) or bicuculline (0.5 and 1 µg/rat) did not significantly affect anxiety-like behaviors, but bicuculline at dose of 1 µg/rat increased locomotor activity. Intra-VH co-infusions of muscimol (0.5 µg/rat) along with low doses of NMDA (0.0625 and 0.125 µg/rat) showed a tendency to increase %OAT, %OAE and locomotor activity; however, no interaction was observed between the drugs. Interestingly, intra-VH co-infusions of bicuculline (0.5 µg/rat) along with effective doses of NMDA (0.25 and 0.5 µg/rat) decreased %OAT, %OAE and locomotor activity, and a significant interaction between two drugs was observed. Discussion: It can be concluded that GABAergic system may mediate the anxiolytic-like effects and increase in locomotor activity induced by NMDA in the VH.
    Autonomic neuroscience: basic & clinical 11/2014; 5(4). · 1.56 Impact Factor
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