What Has Intrinsic Signal Optical Imaging Taught Us About NGF-Induced Rapid Plasticity in Adult Cortex and Its Relationship to the Cholinergic System?

Abstract

Intrinsic signal optical imaging (ISI) is a high-resolution functional brain mapping technique that is being used to further our understanding of the neocortex and its interaction with drugs. Recent studies using combination ISI and in vivo pharmacology have advanced our insight into the actions of both acetylcholine and neurotrophins on inducing rapid and large-scale cortical plasticity. In particular, it appears that acetylcholine (ACh), nicotinic ACh receptors, nerve growth factor (NGF), and NGF receptors (TrkA and p75) are involved in an important feedback loop between the basal forebrain cholinergic system (BFCS) and the neocortex. Specifically, recent data suggest that NGF expressed in the cortex may act on multiple time scales on the BFCS: acutely to increase BFCS release of acetylcholine, intermediately to induce sprouting of BFCS axons, and long-term to change gene expression of BFCS neurons. In this article, advances in understanding the links in vivo between the BFCS, neocortex, nicotinic ACh receptors, and NGF are reviewed.

Current trends in intraoperative optical imaging for functional brain mapping and delineation of lesions of language cortex

“…The activation leads to even more metabolic byproducts some of which are directly vasoactive, such as NO and potassium (Girouard and Iadecola, 2006). Additionally, a behaviorally relevant stimulus can lead to release of vasoactive neurotransmitters, such as acetylcholine or norepinephrine (Prakash and Frostig, 2005; Sandor, 1999). All these factors alter nearby endothelial cells, pericytes, and smooth muscle cells (Allt and Lawrenson, 2001), leading to localized increased HbT via increased CBF and CBV (functional hyperemia).…”

Neuroimaging - Clinical Applications

“…Accordingly, neuronal and non-neuronal expression of α7 nAChR has also been found in peripheral organs (Albuquerque et al, 2009;Sharma & Vijayaraghavan, 2002). Molecular imaging in vivo as considered in this review relates exclusively to the use of radiolabelled receptor ligands, although occasionally optical imaging has been used to investigate the cholinergic system (Prakash & Frostig, 2005). Molecular imaging of α4β2 nAChR in vivo has recently been reviewed (Horti et al, 2010;Sabri et al, 2008).…”

In situ measurements of brain tissue hemoglobin saturation and blood volume by reflectance spectrophotometry in the visible spectrum

“…New instrumentation and computer analysis have made it possible for more detailed and quantitative development of techniques and concepts related to intrinsic optical properties of intact brains. [47][48][49][50][51] It is likely that some of the future advances made in these areas will be based on or strongly influenced by the approaches pioneered by Frans Jöbsis using visible wavelength reflectance spectrophotometry.…”