Cerebrovascular reactivity among native-raised high altitude residents: an fMRI study

Background: The impact of long term residence on high altitude (HA) on human brain has raised concern among researchers in recent years. This study investigated the cerebrovascular reactivity among native-born high altitude (HA) residents as compared to native sea level (SL) residents. The two groups were matched on the ancestral line, ages, gender ratios, and education levels. A visual cue guided maximum inspiration task with brief breath holding was performed by all the subjects while Blood-Oxygenation-Level-Dependent (BOLD) functional Magnetic Resonance Imaging (fMRI) data were acquired from them

Functional MRI and sensory perception of food

Nowadays, human brain activity in response to complex paradigms can be extensively mapped. Though introduced relatively recently, functional magnetic resonance imaging (fMRI) based on blood-oxygen-level-dependent contrast has developed dramatically. It is a noninvasive and exploratory approach which provides in a relatively direct way a differentiated measure of each processing step within the brain, the complete network giving access to cognitive mechanisms. Compared with the other functional imaging methods, fMRI offers high spatial and temporal resolution, and so can detail cognitive tasks both in space and in time by following the time course of the operations. This review deals with how this detailed breakdown is achieved. A further aim is to show how and why fMRI can be used to study sensory perceptions that might, at first sight, seem hard to address by this method, namely perceptions during eating. The processing of stimuli from food by the brain is one determinant of food representation, but also of food liking and wanting, which in turn control appetite, and ultimately food intake. Food consumption also activates the reward system, which thus helps to control food intake. fMRI experiments conducted with human subjects have largely helped to gain a fuller understanding of these intricate brain processes. Among the sensations triggered by food, visual, olfactory, gustatory, and somatosensory cues are the most salient. Accordingly, we focus here on these sensory systems and on the integration of the two senses necessary to produce flavor perception: namely olfaction and gustation