FIGURE 4.

PNN intensity during wakefulness vs. sleep. PNNs display increased intensity during wakefulness (Harkness et al., 2020; Pantazopoulos et al., 2020a), coinciding with increased glutamatergic receptor activity (Harkness et al., 2020) and OTX2 expression (Harkness et al., 2020). This condition promotes LTP as new synapses are formed when interacting with the environment in active states, reflected by increased LTP (Chaudhury et al., 2005) and dendritic spine numbers on pyramidal neurons (Spano et al., 2019; Gisabella et al., 2020). In contrast, PNN intensity decreases during sleep, coinciding with several factors involved in synaptic regulation, including increased expression of proteases in part by microglia (Taishi et al., 2001; Pantazopoulos et al., 2020a), decreased OTX2 protein and glutamatergic receptor activity (Harkness et al., 2020), increased PVB neuron firing (Niethard et al., 2016), decreased LTP (Chaudhury et al., 2005) and decreased dendritic spines on pyramidal neurons, as memories are consolidated during synaptic downscaling (Spano et al., 2019; Gisabella et al., 2020).