Abstract
Activation of the basal forebrain (BF) has been associated with increased attention, arousal, and a heightened cortical representation of the external world. In addition, BF has been implicated in the regulation of the default mode network (DMN) and associated behaviors. Here, we provide causal evidence for a role of BF in DMN regulation, highlighting a prominent role of parvalbumin (PV) GABAergic neurons. The optogenetic activation of BF PV neurons reliably drives animals toward DMN-like behaviors, with no effect on memory encoding. In contrast, BF electrical stimulation enhances memory performance and increases DMN-like behaviors. BF stimulation has a correlated impact on peptide regulation in the BF and ACC, enhancing peptides linked to grooming behavior and memory functions, supporting a crucial role of the BF in DMN regulation. We suggest that in addition to enhancing attentional functions, the BF harbors a network encompassing PV GABAergic neurons that promotes self-directed behaviors associated with the DMN.
Highlights
We studied the expression of two different Cre-dependent viral constructs, adenoassociated virus type 5 (AAV5)-ChR2-mCherry and AAV8-Chronos-GFP, both of which resulted in highly specific opsin expression in PV neurons (Figures 1A–1C)
We anticipated that among basal forebrain (BF) nuclei, the magnocellular preoptic nucleus (MCPO) would show a high density of PV neurons (McKenna et al, 2013), and this was the case
We found that in the visual cortex (VC), the regulation of 11 peptides were affected by BF Deep Brain Stimulation (DBS), a number of which were modulated in BF
Summary
The basal forebrain (BF) has long been known to contribute to attention—that is; the allocation of brain resources to the encoding of incoming sensory stimuli (Baxter and Chiba, 1999; Dotigny et al, 2008; Harris and Thiele, 2011; Herrero et al, 2008; Kang and Vaucher, 2009; Quinn et al, 2010; Xu et al, 2015; Zaborszky and Duque, 2003; Zaborszky et al, 1999; Zinke et al, 2006). Neurons in primary visual cortex (VC; V1) become more responsive to visual stimuli following BF activation (Alitto and Usrey, 2003; Bhattacharyya et al, 2012, 2013; Soma et al, 2011), demonstrating an upregulation of the cortical stimulus representation Along related lines, both single-unit and local field potential responses in V1 exhibit increased trial-to-trial reliability (De Luna et al, 2017; Goard and Dan, 2009; Pinto et al, 2013), facilitating decision making on the basis of sensory evidence. Available evidence suggests that the activation of BF cholinergic projections triggers a cortical state of elevated vigilance and attention to sensory stimuli, consistent with favoring subcortical over cortico-cortical inputs (Hsieh et al, 2000)
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