The diagonal band of Broca in health and disease

Cholinergic Basal Forebrain Integrity and Cognition in Parkinson's Disease: A Reappraisal of Magnetic Resonance Imaging Evidence

Cognitive impairment is a well-recognized and debilitating symptom of Parkinson's disease (PD). Degradation in the cortical cholinergic system is thought to be a key contributor. Both postmortem and in vivo cholinergic positron emission tomography (PET) studies have provided valuable evidence of cholinergic system changes in PD, which are pronounced in PD dementia (PDD). A growing body of literature has employed magnetic resonance imaging (MRI), a noninvasive, more cost-effective alternative to PET, to examine cholinergic system structural changes in PD. This review provides a comprehensive discussion of the methodologies and findings of studies that have focused on the relationship between cholinergic basal forebrain (cBF) integrity, based on T1- and diffusion-weighted MRI, and cognitive function in PD. Nucleus basalis of Meynert (Ch4) volume has been consistently reduced in cognitively impaired PD samples and has shown potential utility as a prognostic indicator for future cognitive decline. However, the extent of structural changes in Ch4, especially in early stages of cognitive decline in PD, remains unclear. In addition, evidence for structural change in anterior cBF regions in PD has not been well established. This review underscores the importance of continued cross-sectional and longitudinal research to elucidate the role of cholinergic dysfunction in the cognitive manifestations of PD. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Response of nitrergic system in the brain of rat conditioned to intracranial self-stimulation

The role of nitrergic system in modulating the action of psychostimulants on reward processing is well established. However, the relevant anatomical underpinnings and scope of the involved interactions with mesolimbic dopaminergic system have not been clarified. Using immunohistochemistry, we track the changes in neuronal nitric oxide synthase (nNOS) containing cell groups in the animals conditioned to intracranial self-stimulation (ICSS) via an electrode implanted in the lateral hypothalamus-medial forebrain bundle (LH-MFB) area. An increase in the nNOS immunoreactivity was noticed in the cells and fibers in the ventral tegmental area (VTA) and nucleus accumbens shell (AcbSh), the primary loci of the reward system. In addition, nNOS was up-regulated in the nucleus accumbens core (AcbC), vertical limb of diagonal band (VDB), locus coeruleus (LC), lateral hypothalamus (LH), superficial gray layer (SuG) of the superior colliculus, and periaqueductal gray (PAG). The brain tissue fragments drawn from these areas showed a change in nNOS mRNA expression, but in opposite direction. Intracerebroventricular (icv) administration of nNOS inhibitor, 7-nitroindazole (7-NI) showed decreased lever press activity in a dose-dependent manner in ICSS task. While an increase in the dopamine (DA) and 3, 4-dihydroxyphenylacetic acid (DOPAC) efflux was noted in the microdialysates collected from the AcbSh of ICSS rats, pre-administration of 7-NI (icv route) attenuated the response. The study identifies nitrergic centers that probably mediate sensory, cognitive, and motor components of the goal-directed behavior.

Dexmedetomidine modulates neuronal activity of horizontal limbs of diagonal band via α2 adrenergic receptor in mice

BACKGROUND AND OBJECTIVES

Dexmedetomidine (DEX) is widely used in clinical sedation which has little effect on cardiopulmonary inhibition, however the mechanism remains to be elucidated. The basal forebrain (BF) is a key nucleus that controls sleep-wake cycle. The horizontal limbs of diagonal bundle (HDB) is one subregions of the BF. The purpose of this study was to examine whether the possible mechanism of DEX is through the α2 adrenergic receptor of BF (HDB).

METHODS

In this study, we investigated the effects of DEX on the BF (HDB) by using whole cell patch clamp recordings. The threshold stimulus intensity, the inter-spike-intervals (ISIs) and the frequency of action potential firing in the BF (HDB) neurons were recorded by application of DEX (2 µM) and co-application of a α2 adrenergic receptor antagonist phentolamine (PHEN) (10 µM).

RESULTS

DEX (2 µM) increased the threshold stimulus intensity, inhibited the frequency of action potential firing and enlarged the inter-spike-interval (ISI) in the BF (HDB) neurons. These effects were reversed by co-application of PHEN (10 µM).

CONCLUSION

Taken together, our findings revealed DEX decreased the discharge activity of BF (HDB) neuron via α2 adrenergic receptors.

The Neuromodulatory Role of the Noradrenergic and Cholinergic Systems and Their Interplay in Cognitive Functions: A Focused Review

The noradrenergic and cholinergic modulation of functionally distinct regions of the brain has become one of the primary organizational principles behind understanding the contribution of each system to the diversity of neural computation in the central nervous system. Decades of work has shown that a diverse family of receptors, stratified across different brain regions, and circuit-specific afferent and efferent projections play a critical role in helping such widespread neuromodulatory systems obtain substantial heterogeneity in neural information processing. This review briefly discusses the anatomical layout of both the noradrenergic and cholinergic systems, as well as the types and distributions of relevant receptors for each system. Previous work characterizing the direct and indirect interaction between these two systems is discussed, especially in the context of higher order cognitive functions such as attention, learning, and the decision-making process. Though a substantial amount of work has been done to characterize the role of each neuromodulator, a cohesive understanding of the region-specific cooperation of these two systems is not yet fully realized. For the field to progress, new experiments will need to be conducted that capitalize on the modular subdivisions of the brain and systematically explore the role of norepinephrine and acetylcholine in each of these subunits and across the full range of receptors expressed in different cell types in these regions.

The brain of the tree pangolin (Manis tricuspis). VIII. The subpallial telencephalon

The current study provides a detailed architectural analysis of the subpallial telencephalon of the tree pangolin. In the tree pangolin, the subpallial telencephalon was divided into septal and striatopallidal regions. The septal region contained the septal nuclear complex, diagonal band of Broca, and the bed nuclei of the stria terminalis. The striatopallidal region comprised of the dorsal (caudate, putamen, internal and external globus pallidus) and ventral (nucleus accumbens, olfactory tubercle, ventral pallidum, nucleus basalis, basal part of the substantia innominata, lateral stripe of the striatum, navicular nucleus, and the major island of Calleja) striatopallidal complexes. In the tree pangolin, the organization and numbers of nuclei forming these regions and complexes, their topographical relationships to each other, and the cyto‐, myelo‐, and chemoarchitecture, were found to be very similar to that observed in commonly studied mammals. Minor variations, such as less nuclear parcellation in the bed nuclei of the stria terminalis, may represent species‐specific variations, or may be the result of the limited range of stains used. Given the overall similarity across mammalian species, it appears that the subpallial telencephalon of the mammalian brain is highly conserved in terms of evolutionary changes detectable with the methods used. It is also likely that the functions associated with these nuclei in other mammals can be translated directly to the tree pangolin, albeit with the understanding that the stimuli that produce activity within these regions may be specific to the life history requirements of the tree pangolin.