Simultaneous EEG-fMRI reveals attention-dependent coupling of early face processing with a distributed cortical network.

The speed of visual processing is central to our understanding of face perception. Yet the extent to which early visual processing influences later processing in distributed face processing networks, and the top-down modulation of such bottom-up effects, remains unclear. We used simultaneous EEG-fMRI to investigate cortical activity that showed unique covariation with ERP components of face processing (C1, P1, N170, P3), while manipulating sustained attention and transient cognitive conflict employing an emotional face-word Stroop task.

Cholinergic enhancement of functional networks in older adults with mild cognitive impairment.

Objective: The importance of the cholinergic system for cognitive function has been well documented in animal and human studies. The objective of this study was to elucidate the cognitive and functional connectivity changes associated with enhanced acetylcholine levels. We hypothesized that older adults with mild memory deficits would show behavioral and functional network enhancements with an acetylcholinesterase inhibitor treatment (donepezil) when compared to a placebo control group.

Parameterization of transcranial magnetic stimulation.

A recent study (Di Lazzaro et al. J Neurophysiol 105: 2150-2156, 2011) describes the findings from a rigorous comparison on the effects of several popular variations of transcranial magnetic stimulation (TMS) protocols. The results demonstrate that excitatory and inhibitory neural networks may be independently modulated based on TMS protocol selection.

Deficit in switching between functional brain networks underlies the impact of multitasking on working memory in older adults.

Multitasking negatively influences the retention of information over brief periods of time. This impact of interference on working memory is exacerbated with normal aging. We used functional MRI to investigate the neural basis by which an interruption is more disruptive to working memory performance in older individuals.

Causal role of the prefrontal cortex in top-down modulation of visual processing and working memory.

Selective attention filters information to limit what is encoded and maintained in working memory. Although the prefrontal cortex (PFC) is central to both selective attention and working memory, the underlying neural processes that link these cognitive abilities remain elusive. Using functional magnetic resonance imaging to guide repetitive transcranial magnetic stimulation with electroencephalographic recordings in humans, we perturbed PFC function at the inferior frontal junction in participants before they performed a selective-attention, delayed-recognition task.

An expectation-based memory deficit in aging.

Memory performance can be enhanced by expectations regarding the appearance of ensuing stimuli. Here, we investigated the influence of stimulus-category expectation on memory performance in aging, and used fMRI to explore age-related alterations in associated neural mechanisms. Unlike younger adults, who demonstrated both working memory (WM) and long-term memory (LTM) performance benefits for face stimuli when this stimulus category was expected, older adults did not exhibit these memory benefits.

Expectation-driven changes in cortical functional connectivity influence working memory and long-term memory performance.

Expectations generated by predictive cues increase the efficiency of perceptual processing for complex stimuli (e.g., faces, scenes); however, the impact this has on working memory (WM) and long-term memory (LTM) has not yet been investigated.

Top-down modulation of visual feature processing: the role of the inferior frontal junction.

Distinct areas within the visual association cortex are specialized for representing specific stimulus features, such as V4 for color and V5/hMT+ for motion. Recent studies have demonstrated that areas associated with attended features exhibit enhanced cortical activity, whereas those associated with ignored features elicit reduced activity. However, the source of this attentional (or top-down) modulation remains uncertain.

Neural mechanisms underlying the impact of visual distraction on retrieval of long-term memory.

Filtering information on the basis of what is relevant to accomplish our goals is a critical process supporting optimal cognitive performance. However, it is not known whether exposure to irrelevant environmental stimuli impairs our ability to accurately retrieve long-term memories. We hypothesized that visual processing of irrelevant visual information would interfere with mental visualization engaged during recall of the details of a prior experience, despite goals to direct full attention to the retrieval task.

Mechanisms of working memory disruption by external interference.

The negative impact of external interference on working memory (WM) performance is well documented; yet, the mechanisms underlying this disruption are not sufficiently understood. In this study, electroencephalogram and functional magnetic resonance imaging (fMRI) data were recorded in separate experiments that each introduced different types of visual interference during a period of WM maintenance: distraction (irrelevant stimuli) and interruption (stimuli that required attention). The data converged to reveal that regardless of the type of interference, the magnitude of processing interfering stimuli in the visual cortex (as rapidly as 100 ms) predicted subsequent WM recognition accuracy for stored items.