Abstract
The medial prefrontal cortex (mPFC) exerts top-down control of primary visual cortex (V1) activity. As there is no direct neuronal projection from mPFC to V1, this functional connection may use an indirect route, i.e., via basalo-cortical cholinergic projections. The cholinergic projections to V1 originate from neurons in the horizontal limb of the diagonal band of Broca (HDB), which receive neuronal projections from the ventral part of the mPFC, composed of prelimbic (PrL) and infralimbic cortices (IL). Therefore, the objective of this study was to determine whether electrical stimulation of mice mPFC subregions activate (1) V1 neurons; and (2) HDB cholinergic neurons, suggesting that the HDB serves as a relay point in the mPFC-V1 interaction. Neuronal activation was quantified using c-Fos immunocytochemistry or thallium autometallography for each V1 layer using automated particle analysis tools and optical density measurement. Stimulation of IL and PrL induced significantly higher c-Fos expression or thallium labeling in layers II/III and V of V1 in the stimulated hemisphere only. A HDB cholinergic neuron-specific lesion by saporin administration reduced IL-induced c-Fos expression in layers II/III of V1 but not in layer V. However, there was no c-Fos expression or thallium labeling in the HDB neurons, suggesting that this area was not activated by IL stimulation. Stimulation of another mPFC subarea, the anterior cingulate cortex (AC), which is involved in attention and receives input from V1, activated neither V1 nor HDB. The present results indicate that IL and PrL, but not AC, stimulation activates V1 with the minor involvement of the HDB cholinergic projections. These results suggest a functional link between the ventral mPFC and V1, but this function is only marginally supported by HDB cholinergic neurons and may involve other brain regions.
Highlights
The medial prefrontal cortex plays a ubiquitous role in decision making, attention and other cognitive processes in humans, primates and rodents
EFFECT OF CHOLINERGIC FIBER LESIONS ON medial prefrontal cortex (mPFC) STIMULATION-INDUCED NEURONAL ACTIVITY To further evaluate the role of HDB cholinergic neurons in the infralimbic cortices (IL)-evoked increase of V1 neuronal activity, a specific lesion of the cholinergic neurons was performed with p75saporin intraventricular injection
The present study demonstrates that activation of the IL and PrL mPFC subregions, but not the anterior cingulate (AC), induced neuronal activation in layers II/III and V of V1
Summary
The medial prefrontal cortex (mPFC) plays a ubiquitous role in decision making, attention and other cognitive processes in humans, primates and rodents. The rat mPFC, as the homologs area in primates, the dorsolateral PFC, is involved in visual attention (Muir et al, 1996; Granon et al, 1998; Delatour and Gisquet-Verrier, 2000; Heidbreder and Groenewegen, 2003; Maddux and Holland, 2011) and cue guided behavior (Passetti et al, 2002; Kozak et al, 2006; Parikh et al, 2007) Both mechanisms may involve topdown control of the primary sensory areas, by modulating local responsiveness to afferent sensory stimuli. The vmPFC is the major output region of the mPFC and shares anatomical connections with many parts of the brain, including the ventral tegmental area, the amygdala, several regions of the temporal lobe, the olfactory system, the hypothalamus, the hippocampal formation and the basal forebrain (BF), i.e., the diagonal band of Broca, substantia innominata and nucleus basalis magnocellularis (Vertes, 2004; Gabbott et al, 2005)
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