How feedback inhibition shapes spike-timing-dependent plasticity and its implications for recent Schizophrenia models

NMDA Receptor Model of Antipsychotic Drug-Induced Hypofrontality

Schizophrenia is a chronic mental disease, affecting around 1% of the general population. Schizophrenia is characterized by productive, negative, affective, and disorganization symptoms, and cognitive deficits. Cognitive deficits prevail in most of the schizophrenia patients and are one of the most disabling symptoms. They usually occur before the acute episode of the disease and tend to become chronic with no satisfactory treatment from antipsychotic drugs. Because of their early manifestation in patients’ lives, cognitive deficits are suggested to be the primary symptom of schizophrenia. The pathogenesis of cognitive deficits in schizophrenia is not fully understood. They are linked with hypofrontality, which is a decrease in blood flow and glucose metabolism in the prefrontal lobe of schizophrenia-suffering patients. Hypofrontality is linked with disturbances of the corticolimbothalamic circuit, important for cognition and memory in humans. The circuit consists of a group of neuroanatomic structures and hypothetically any disturbance in them may result in cognitive deficits. We present a translational preclinical model of understanding how antipsychotic medication may decrease the N-methyl-D-aspartic acid (NMDA) receptors’ activity and produce dysfunctions in the corticolimbothalamic circuit and hypofrontality. From several pharmacological experiments on rats, including mainly our own recent findings, we collected data that suggest that antipsychotic medication may maintain and escalate hypofrontality in schizophrenia, decreasing NMDA receptor activity in the corticolimbothalamic circuit in the human brain. We discuss our findings within the literature of the subject.

Inhibitory control of site-specific synaptic plasticity in a model CA1 pyramidal neuron

A computational model of a biochemical network underlying synaptic plasticity is combined with simulated on-going electrical activity in a model of a hippocampal pyramidal neuron to study the impact of synapse location and inhibition on synaptic plasticity. The simulated pyramidal neuron is activated by the realistic stimulation protocol of causal and anticausal spike pairings of presynaptic and postsynaptic action potentials in the presence and absence of spatially targeted inhibition provided by basket, bistratified and oriens-lacunosum moleculare (OLM) interneurons. The resulting Spike-timing-dependent plasticity (STDP) curves depend strongly on the number of pairing repetitions, the synapse location and the timing and strength of inhibition.