Age trajectories of functional activation under conditions of low and high processing demands: an adult lifespan fMRI study of the aging brain.

We examined functional activation across the adult lifespan in 316 healthy adults aged 20-89years on a judgment task that, across conditions, drew upon both semantic knowledge and ability to modulate neural function in response to cognitive challenge. Activation in core regions of the canonical semantic network (e.g.

Age-related differences in memory-encoding fMRI responses after accounting for decline in vascular reactivity.

BOLD fMRI has provided a wealth of information about the aging brain. A common finding is that posterior regions of the brain manifest an age-related decrease in activation while the anterior regions show an age-related increase. Several neurocognitive models have been proposed to interpret these findings.

Effects of beta-amyloid accumulation on neural function during encoding across the adult lifespan.

Limited functional imaging evidence suggests that increased beta-amyloid deposition is associated with alterations in brain function, even in healthy older adults. However, the majority of these findings report on resting-state activity or functional connectivity in adults over age 60. Much less is known about the impact of beta-amyloid on neural activations during cognitive task performance, or the impact of amyloid in young and middle-aged adults.

A comparison of physiologic modulators of fMRI signals.

One of the main obstacles in quantitative interpretation of functional magnetic resonance imaging (fMRI) signal is that this signal is influenced by non-neural factors such as vascular properties of the brain, which effectively increases signal variability. One approach to account for non-neural components is to identify and measure these confounding factors and to include them as covariates in data analysis or interpretation. Previously, several research groups have independently identified four potential physiologic modulators of fMRI signals, including baseline venous oxygenation (Yv ), cerebrovascular reactivity (CVR), resting state BOLD fluctuation amplitude (RSFA), and baseline cerebral blood flow (CBF).

Culture-related differences in default network activity during visuo-spatial judgments.

Studies on culture-related differences in cognition have shown that Westerners attend more to object-related information, whereas East Asians attend more to contextual information. Neural correlates of these different culture-related visual processing styles have been reported in the ventral-visual and fronto-parietal regions. We conducted an fMRI study of East Asians and Westerners on a visuospatial judgment task that involved relative, contextual judgments, which are typically more challenging for Westerners.

Alterations in cerebral metabolic rate and blood supply across the adult lifespan.

With age, the brain undergoes comprehensive changes in its function and physiology. Cerebral metabolism and blood supply are among the key physiologic processes supporting the daily function of the brain and may play an important role in age-related cognitive decline. Using MRI, it is now possible to make quantitative assessment of these parameters in a noninvasive manner.

Culture differences in neural processing of faces and houses in the ventral visual cortex.

Behavioral and eye-tracking studies on cultural differences have found that while Westerners have a bias for analytic processing and attend more to face features, East Asians are more holistic and attend more to contextual scenes. In this neuroimaging study, we hypothesized that these culturally different visual processing styles would be associated with cultural differences in the selective activity of the fusiform regions for faces, and the parahippocampal and lingual regions for contextual stimuli. East Asians and Westerners passively viewed face and house stimuli during an functional magnetic resonance imaging experiment.

Age differences in default mode activity on easy and difficult spatial judgment tasks.

The default network is a system of brain areas that are engaged when the mind is not involved in goal-directed activity. Most previous studies of age-related changes in default mode processing have used verbal tasks. We studied non-verbal spatial tasks that vary in difficulty.

The impact of increased relational encoding demands on frontal and hippocampal function in older adults.

In the present study, we manipulated the cognitive effort in an associative encoding task using functional magnetic resonance imaging (fMRI). Older and younger adults were presented with two objects that were either semantically related or unrelated, and were required to form a relationship between the items. Both groups self-reported greater difficulty in completing the unrelated associative encoding task providing independent evidence of the associative difficulty manipulation.