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 prior to participants performing a selective-attention, delayed-recognition task. This resulted in diminished top-down modulation of activity in posterior cortex during early encoding stages, which predicted a subsequent decrement in working memory accuracy. Participants with stronger fronto-posterior functional connectivity displayed greater disruptive effects. Data further suggested that broad alpha band (7–14 Hz) phase coherence subserved this long distance top-down modulation. The results establish top-down modulation mediated by the prefrontal cortex as a causal link between early attentional processes and subsequent memory performance.

The study aimed to evaluate the effects of non-invasive brain stimulation on cognitive function in healthy older adults and patients with Alzheimer’s disease (AD). A comprehensive literature search was performed on non-invasive stimulation studies published from January 1990 to November 2014 in Pubmed and Web of Science. Fourteen articles with a total of 331 participants were identified as studies with healthy older adults and the mean effect size and 95% confidence interval were estimated. A significant effect size of 0.42 was found for the cognitive outcome. Further subgroup analyses demonstrated more prominent effects for studies delivering the stimulation before the execution of the task and studies applying multiple sessions of stimulation. To assess effects of stimulation on AD patients, eleven studies with a total of 200 patients were included in the analysis. A significant effect size of 1.35 was found for the cognitive outcomes. Subgroup analyses indicated more pronounced effects for studies applying the stimulation during the execution of the task compared to studies delivering the stimulation before the execution of the task. Non-invasive brain stimulation has a positive effect on cognitive function in physiological and pathological aging.

Our ability to focus attention on task-relevant information and ignore distractions is reflected by differential enhancement and suppression of neural activity in sensory cortex (i.e., top-down modulation). Such selective, goal-directed modulation of activity may be intimately related to memory, such that the focus of attention biases the likelihood of successfully maintaining relevant information by limiting interference from irrelevant stimuli. Despite recent studies elucidating the mechanistic overlap between attention and memory, the relationship between top-down modulation of visual processing during working memory (WM) encoding, and subsequent recognition performance has not yet been established. Here, we provide neurophysiological evidence in healthy, young adults that top-down modulation of early visual processing (Ͻ 200 ms from stimulus onset) is intimately related to subsequent WM performance, such that the likelihood of successfully remembering relevant information is associated with limiting interference from irrelevant stimuli. The consequences of a failure to ignore distractors on recognition performance was replicated for two types of feature-based memory, motion direction and color. Moreover, attention to irrelevant stimuli was reflected neurally during the WM maintenance period as an increased memory load. These results suggest that neural enhancement of relevant information is not the primary determinant of high-level performance, but rather optimal WM performance is dependent on effectively filtering irrelevant information through neural suppression to prevent overloading a limited memory capacity.

Normal aging is associated with a degradation of perceptual abilities and a decline in higher-level cognitive functions, notably working memory. To remediate age-related deficits, cognitive training programs are increasingly being developed. However, it is not yet definitively established if, and by what mechanisms, training ameliorates effects of cognitive aging. Furthermore, a major factor impeding the success of training programs is a frequent failure of training to transfer benefits to untrained abilities. Here, we offer the first evidence of direct transfer-of-benefits from perceptual discrimination training to working memory performance in older adults. Moreover, using electroencephalography to evaluate participants before and after training, we reveal neural evidence of functional plasticity in older adult brains, such that training-induced modifications in early visual processing during stimulus encoding predict working memory accuracy improvements. These findings demonstrate the strength of the perceptual discrimination training approach by offering clear psychophysical evidence of transfer-of-benefit and a neural mechanism underlying cognitive improvement.

A recent study shows that the fronto-parietal network (FPN), and subregions therein, alters its functional connectivity with nodes of other networks based on task goals. Moreover, FPN patterns of connectivity not only reflect engagement of specific tasks, but also serve as a code that can be transferred to facilitate learning novel tasks.

Hexanucleotide repeat expansions in C9ORF72 are the most common known genetic cause of familial and sporadic frontotemporal dementia and amyotrophic lateral sclerosis. Previous work has shown that patients with behavioral variant frontotemporal dementia due to C9ORF72 show salience and sensorimotor network disruptions comparable to those seen in sporadic behavioral variant frontotemporal dementia, but it remains unknown how early in the lifespan these and other changes in brain structure and function arise. To gain insights into this question, we compared 15 presymptomatic carriers (age 43.7 ± 10.2 years, nine females) to matched healthy controls. We used voxel-based morphometry to assess gray matter, diffusion tensor imaging to interrogate white matter tracts, and task-free functional MRI to probe the salience, sensorimotor, default mode, and medial pulvinar thalamus-seeded networks. We further used a retrospective chart review to ascertain psychiatric histories in carriers and their non-carrier family members. Carriers showed normal cognition and behavior despite gray matter volume and brain connectivity deficits that were apparent as early as the fourth decade of life. Gray matter volume deficits were topographically similar though less severe than those in patients with behavioral variant frontotemporal dementia due to C9ORF72, with major foci in cingulate, insula, thalamus, and striatum. Reduced white matter integrity was found in the corpus callosum, cingulum bundles, corticospinal tracts, uncinate fasciculi and inferior longitudinal fasciculi. Intrinsic connectivity deficits were detected in all four networks but most prominent in salience and medial pulvinar thalamus-seeded networks. Carrier and control groups showed comparable relationships between imaging metrics and age, suggesting that deficits emerge during early adulthood. Carriers and non-carrier family members had comparable lifetime histories of psychiatric symptoms. Taken together, the findings suggest that presymptomatic C9ORF72 expansion carriers exhibit functionally compensated brain volume and connectivity deficits that are similar, though less severe, to those reported during the symptomatic phase. The early adulthood emergence of these deficits suggests that they represent aberrant network patterning during development, an early neurodegeneration prodrome, or both.

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. A network of fronto-parietal cortical regions has been proposed as the prime candidate underlying this top-down modulation. Here, we evaluate whether there are distinct or overlapping top-down network regions for attention to different stimulus features. To this end, we explored functional magnetic resonance imaging (fMRI) functional connectivity data, electroencephalographic (EEG) source localization, and phase coherence that were obtained while participants attended or ignored motion and color stimuli. Functional connectivity analysis indicated that attention to color relies strongly on prefrontal regions, whereas attention to motion recruits both prefrontal and parietal areas. Although these networks are generally topologically segregated, both color and motion processes recruit right inferior frontal junction (IFJ). However, the IFJ may be more critical for color processing, as only connectivity with V4 predicted the degree of attentional modulation. Source localization at the time range of attentional modulation of the event related potential corroborated the role of the right IFJ and indicated that feature-based, top-down modulation occurs early during processing (< 200 ms post-stimulus onset). Furthermore, long-distance alpha (8-12 Hz) phase coherence between the IFJ and visual cortices may serve as a mechanism underlying anticipatory, top-down modulation of color feature processing.

Temporal cues guide attentional resources toward relevant points in time, resulting in optimized behavioral performance. Although deficits in aspects of attention have been documented in older adults, it remains unknown whether the critical ability to orient attention in time is affected by normal aging. To address this, younger and older adults participated in a temporally cued target-response experiment while electroencephalographic (EEG) data were recorded. Three conditions (one detection and two discrimination tasks) were used to manipulate task complexity. Response times show that younger adults, but not older adults, utilized temporal cues to enhance performance regardless of task complexity. Similarly, alpha band activity (8-12 Hz) and the contingent negative variation (CNV) preceding targets indicated that only younger adults engaged pre-stimulus, anticipatory neural mechanisms associated with temporal cues. Overall, these results provide novel evidence that older adults do not utilize temporal cues to orient attention in time and support an expectation deficit in normal aging.