แต่ละของการเปลี่ยนแปลงในเครื่องหมายของตะกร้า PV Each of the alterations in markers of PV basket and chandelier
และโคมระย้าเชื่อมต่อเซลล์ประสาทเด่นชัดมากที่สุดในชั้น3, ชั้นเดียวกันสถานที่ที่ผิดปกติทางสัณฐานวิทยาในเซลล์เสี้ยมมีความโดดเด่นที่สุด neuron connectivity is most pronounced in layer 3, the same laminar
location where the morphological abnormalities in pyramidal cells are
most striking. Interestingly, studies in non-human primates have
shown that neural activity in the DLFPC is particularly pronounced in
layer 3 during working memory tasks, and that the pattern of neural
connections in this layer is well suited to support the sustained firing
of DLPFC neurons observed during the delay period of working
memory tasks (Goldman-Rakic, 1995). Thus, the alterations in
pyramidal neuron–PV neuron connectivity are likely to contribute to
the working memory impairments in schizophrenia.
Consistent with this interpretation, the working memory impairments
in schizophrenia are associated with lower power of frontal lobe
gamma oscillations (Cho et al., 2006; Minzenberg et al., 2010), which
in at least other association regions of the primate neocortex are most
prominent in layer 3 (Buffalo et al., 2011). Furthermore, both
computational models (Gonzalez-Burgos & Lewis, 2008) and experimental
data in rodents (Cardin et al., 2009; Sohal et al., 2009)
indicate that pyramidal neuron–PV neuron connectivity is essential for
the generation of gamma oscillations, supporting the interpretation that
alterations in this local circuitry contribute to the neural substrate for
working memory impairments in the illness. However, these findings
leave open the question of whether the alterations in pyramidal
neurons or PV neurons are the proximal cause of the disturbance in
neural network activity. Recent data in humans, reviewed in detail
elsewhere (Lewis et al., 2012), converge on the hypothesis that an
intrinsic deficit in pyramidal neuron dendritic spines, the associated loss of excitatory synapses and the resulting reduction in cortical
network activity leads to a homeostatic reduction in inhibition from
PV basket neurons in order to restore excitatory–inhibitory balance.
While a direct examination of this hypothesis in individuals with
schizophrenia faces the usual constraints associated with experimental
studies in humans, studies in model animal systems can be used to
provide proof-of-concept tests of the cause and effect relationships
between observations made in post mortem human studies. For
example, genetic manipulations in mice that selectively reduce
dendritic spines in pyramidal neurons would be predicted to recapitulate
the pattern of other circuitry alterations seen in schizophrenia,
whereas the selective reduction of GAD67 expression in PV basket
would not.
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