Role of the Basal Forebrain
Neurons in Cortical Activation and Behavioural State Regulation
Re^3: Attention vs. "Arousal" or Cortical Activation
Using relatively large tracer injections into the thalamus and basal forebrain, Losier and Semba (Brain Res., 604:41-52, 1993) have shown that 8% of single mesopontine tegmental cholinergic neurons, 5% of serotonergic raphe neurons, 2% of noradrenergic locus coeruleus neurons, and 2% of histaminergic tuberomammillary neurons project to both the thalamus and the basal forebrain through axonal collateralization. These percentages are likely to be underestimated due to limited penetration of antibodies. As mentioned in my previous message to Dr. Barbara Jones, there is no anatomical evidence for direct projections from the basal forebrain to LGN. However, please also check my reply to Dr. Marian Lewandowski for other possible pathways from the LGN to the basal forebrain, and there might be more.
Wed Dec 16