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This chapter focuses on aspects of structural and functional neuroanatomy relevant to Behavioral Neurology & Neuropsychiatry (BN&NP). It considers the general structure of the brain from the brainstem through the cerebral cortex, including a review of white matter anatomy, the cerebral vasculature, and the ventricular system. The brainstem comprises the medulla oblongata, pons and cerebellum, and midbrain. Each of these areas and the neurobehaviorally salient structures they contain are reviewed briefly in the chapter. The reticular formation (which is contributed to by several brainstem substructures) and the cranial nerves (some, but not all, of which are located within the brainstem) also are discussed in the chapter. The diencephalon includes the thalamus, metathalamus (medial and lateral geniculate nuclei), epithalamus (habenula, stria medullaris, and pineal body), and subthalamus. The chapter considers briefly the thalamus, hypothalamus (and pituitary), and the epithalamus.
Background: There is ongoing debate about whether a decline in body mass represents a true risk factor for dementia, whether it is a phenotypic marker of incipient dementia, or perhaps a marker of another process that increases dementia risk. This study was designed to determine if changes in body mass index (BMI) in later life are associated with hazard of incident dementia over a follow-up period of up to eight years.
Methods: Method followed was a prospective cohort study of 4,181 men aged 65–84 years, resident in Perth, Australia. The exposure of interest was change in BMI measured between 1996–1998 and 2001–2004. The outcome was incident dementia, established using the Western Australia Data Linkage System until 2009. We used Cox regression models to establish crude and adjusted hazard of dementia for change in BMI.
Results: Compared with men with a stable BMI, those with a decrease in BMI >1 kg/m2 had a higher adjusted hazard of dementia (hazard ratio (HR) = 1.89, 95% CI = 1.32–2.70). The cumulative hazard of dementia over follow-up for changes in BMI was greatest for men with a decrease in BMI >1 kg/m2; this trend was apparent for men in all BMI categories (underweight, normal, overweight, obese). A reverse “J-shaped” association between BMI change and incident dementia was observed, with the lowest dementia rate being for men whose BMI remained stable.
Conclusions: Men who maintained a stable body mass had the lowest incidence of dementia. Further studies are needed to clarify causality and assess feasibility of interventional studies to preserve body mass in aging men.
Here we examine the patterns of connections between the
zona incerta (ZI) of the thalamus and the major visual
centers of the rat brain, namely the retina, dorsal lateral
geniculate nucleus (LGd), superficial layers of the superior
colliculus (SCs), and occipital cortex (Oc1). Injections
of the tracers biotinylated dextran or cholera toxin subunit
b were made into each of these centers, as well
as ZI itself, by using stereotaxic coordinates. Rat brains
were then aldehyde-fixed and processed using standard methods.
We show that the retina, LGd, SCs, and Oc1 all have connections
with ZI; moreover, that each of these connections make
a very distinct territory or subsector within the most
lateral ZI regions. This subsector of connectivity with
the visual centers does not respect the well-defined cytoarchitectonic
sectors of ZI, being made up of small zones in the dorsal,
ventral, and caudal sectors. Often, a distinctive “horse-shoe”
pattern is evident, particularly after retinal and Oc1
injections. Tracer injections into topographically distinct
regions of the LGd, SCs, or Oc1 results in no shift in
the spatial location of labelling within ZI; after each
injection, labelling is always seen within the lateral
edge of the nucleus. Labelled terminals and cells are seen
after LGd and SCs injections, while only labelled terminals
are seen after retinal and Oc1 injections. Although the
precise function of this novel visual subsector is not
known, these early findings suggest that ZI may be in a
position to integrate visual information together with
the other somatosensory, motor, and visceral information
that it receives.
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