![]() Collectively, these findings indicate reduced synaptic connections in the schizophrenia PFC. Studies have also identified reduced density of glutamate- or GABA-containing axon terminals, presumably corticocortical and intrinsic in origin. Decreased density of afferent axon terminals from the mediodorsal thalamus and terminals containing dopamine from the ventral tegmental area have also been described in the dorsolateral PFC in schizophrenia brains. Axon terminals in the PFC may come from collateral branches of pyramidal neuronal axons, GABA interneurons, and afferents from cortical and subcortical areas. ![]() In addition to abnormalities of postsynaptic elements, postmortem studies have identified a decreased density of synaptophysin-immunoreactive puncta representing presynaptic axon terminals in the PFC of schizophrenia patients. In a preclinical model, DISC1 mutant mice show small dendritic spines in pyramidal neurons of the PFC ( Lee et al., 2011). DISC1 has been identified as a candidate gene in schizophrenia. For example, the protein disrupted in schizophrenia 1 (DISC1) binds to postsynaptic density protein-95 and modulates its interaction with N-methyl- d-aspartate (NMDA) receptors, and hence it is integral to activity-dependent structural plasticity of dendritic spines (see Chapter 2). The loss of dendritic spines might be a primary pathological state in schizophrenia because a number of candidate genes of schizophrenia affect the development and function of dendritic spines. Consequently, the loss of dendritic spines results in decreased glutamatergic (excitatory) synapses onto layer-3 pyramidal neurons of the dorsolateral PFC in schizophrenia. Each dendritic spine of a pyramidal neuron typically forms synapses with at least one glutamatergic excitatory terminal. In addition to the loss of dendritic spines, dendrites of layer-3 pyramidal neurons are also shorter in length. Rajakumar, in The Cerebral Cortex in Neurodegenerative and Neuropsychiatric Disorders, 2017 Pyramidal Neuronal Abnormalities May Lower Their Excitabilityįewer numbers of dendritic spines, particularly on the basal dendrites of layer-3 pyramidal neurons, and a corresponding decrease in proteins specific to dendritic spines such as spinophilin are consistent findings in the dorsolateral PFC of schizophrenia brains. Thus, as is typical of most sensory systems, centrifugal and feedback circuits contribute to the flow of information through the olfactory bulb. While their specific functions and role in modulating information processing in the olfactory bulb are not entirely clear, it is evident that the synaptic actions of these circuits will activate the granule cells and, in turn, their dendrodendritic circuits within the EPL. T., 1991), and the raphe nucleus ( McLean, J. D., 1984), the locus coeruleus ( McLean, J. Axon collaterals from mitral and tufted cells form asymmetric synapses on granule cell basal dendrites as do axons from the anterior olfactory nucleus, anterior commissure, olfactory cortex, horizontal limb of the diagonal band ( Carson, K. The basal dendrites of the granule cells in the granule cell layer receive synaptic input from a variety of sources ( Price, J. Rodriguez Gil, in The Senses: A Comprehensive Reference, 2008 4.36.5.5 Granule Cell Layer Thus, as is typical of most sensory systems, centrifugal and feedback circuits contribute to the flow of information through the olfactory bulb.Ĭ.A. While their specific functions and role in modulating information processing in the olfactory bulb are not entirely clear, it is evident that the synaptic actions of these circuits will activate the granule cells and, in turn, their dendrodendritic circuits within the EPL ( Boyd et al., 2012 Nunez-Parra et al., 2013). Axon collaterals from mitral and tufted cells form asymmetric synapses on granule cell bodies and basal dendrites as do axons from the anterior olfactory nucleus, anterior commissure, olfactory cortex ( Padmanabhan et al., 2016), horizontal limb of the diagonal band ( Carson, 1984 Shipley and Adamek, 1984), the locus coeruleus ( McLean et al., 1989 McLean and Shipley, 1991) and the raphe nucleus ( McLean and Shipley, 1987). The basal dendrites of the granule cells in the granule cell layer receive synaptic input from a variety of sources ( Price and Powell, 1970b). Fumiaki Imamura, Diego J Rodriguez-Gil, in The Senses: A Comprehensive Reference (Second Edition), 2020 3.29.6.5 Granule Cell Layer
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