Anodal transcranial direct current stimulation temporarily reverses age-associated cognitive decline and functional brain activity changes

The rising proportion of elderly people worldwide will yield an increased incidence of age-associated cognitive impairments, imposing major burdens on societies. Consequently, growing interest emerged to evaluate new strategies to delay or counteract cognitive decline in aging. Here, we assessed immediate effects of anodal transcranial direct current stimulation (atDCS) on cognition and previously described detrimental changes in brain activity attributable to aging. Twenty healthy elderly adults were assessed in a crossover shamcontrolled design using functional magnetic resonance imaging (fMRI) and concurrent transcranial DCS administered to the left inferior frontal gyrus. Effects on performance and task-related brain activity were evaluated during overt semantic word generation, a task that is negatively affected by advanced age. Task-absent resting-state fMRI (RS-fMRI) assessed atDCS-induced changes at the network level independent of performance. Twenty matched younger adults served as controls. During sham stimulation, task-related fMRI demonstrated that enhanced bilateral prefrontal activity in older adults was associated with reduced performance. RS-fMRI revealed enhanced anterior and reduced posterior functional brain connectivity. atDCS significantly improved performance in older adults up to the level of younger controls; significantly reduced task-related hyperactivity in bilateral prefrontal cortices, the anterior cingulate gyrus, and the precuneus; and induced a more "youth-like" connectivity pattern during RS-fMRI. Our results provide converging evidence from behavioral analysis and two independent functional imaging paradigms that a single session of atDCS can temporarily reverse nonbeneficial effects of aging on cognition and brain activity and connectivity. These findings may translate into novel treatments to ameliorate cognitive decline in normal aging in the future

Cognitive control modulates preferential sensory processing of affective stimuli

Adaptive human behavior crucially relies on the ability of the brain to allocate resources automatically to emotionally significant stimuli. This ability has consistently been demonstrated by studies showing preferential processing of affective stimuli in sensory cortical areas. It is still unclear, however, whether this putatively automatic mechanism can be modulated by cognitive control processes. Here, we use functional magnetic resonance imaging (fMRI) to investigate whether preferential processing of an affective face distractor is suppressed when an affective distractor has previously elicited a response conflict in a word-face Stroop task. We analyzed this for three consecutive stages in the ventral stream of visual processing for which preferential processing of affective stimuli has previously been demonstrated: the striate area (BA 17), category-unspecific extrastriate areas (BA 18/19), and the fusiform face area (FFA). We found that response conflict led to a selective suppression of affective face processing in category-unspecific extrastriate areas and the FFA, and this effect was accompanied by changes in functional connectivity between these areas and the rostral anterior cingulate cortex. In contrast, preferential processing of affective face distractors was unaffected in the striate area. Our results indicate that cognitive control processes adaptively suppress preferential processing of affective stimuli under conditions where affective processing is detrimental because it elicits response conflict

Electrical Brain Stimulation Improves Cognitive Performance by Modulating Functional Connectivity and Task-Specific Activation

Excitatory anodal transcranial direct current stimulation (atDCS) can improve human cognitive functions, but neural underpinnings of its mode of action remain elusive. In a cross-over placebo ("sham") controlled study we used functional magnetic resonance imaging (fMRI) to investigate neurofunctional correlates of improved language functions induced by atDCS over a core language area, the left inferior frontal gyrus (IFG). Intrascanner transcranial direct current stimulation-induced changes in overt semantic word generation assessed behavioral modulation; task-related and task-independent (resting-state) fMRI characterized language network changes. Improved word-retrieval during atDCS was paralleled by selectively reduced task-related activation in the left ventral IFG, an area specifically implicated in semantic retrieval processes. Under atDCS, resting-state fMRI revealed increased connectivity of the left IFG and additional major hubs overlapping with the language network. In conclusion, atDCS modulates endogenous low-frequency oscillations in a distributed set of functionally connected brain areas, possibly inducing more efficient processing in critical task-relevant areas and improved behavioral performance

Neural Signatures of Semantic and Phonemic Fluency in Young and Old Adults

As we age, our ability to select and produce words changes, yet we know little about the underlying neural substrate of word-finding difficulties in old adults. The present study was designed to elucidate changes in specific frontally mediated retrieval processes involved in word-finding difficulties associated with advanced age. We implemented two overt verbal (semantic and phonemic) fluency tasks during functional magnetic resonance imaging and compared brain activity patterns of old and young adults. Performance during the phonemic task was comparable for both age-groups and mirrored by strongly left lateralized (frontal) activity patterns. On the other hand, a significant drop of performance during the semantic task in the older goup was accompanied by additional right (inferior and middle) frontal activity, which was negatively correlated with performance. Moreover, the younger group recruited different subportions of the left inferior frontal gyrus for both fluency tasks, while the older participants failed to show this distinction. Thus, functional integrity and efficient recruitment of left frontal language areas seems to be critical for successful word-retrieval in old age

Interpersonal Arrogance and the Incentive Salience of Power <i>Versus</i> Affiliation Cues

The arrogance dimension of the circumplex contrasts people who seemingly value power over affiliation (high arrogance) versus those who do not (low arrogance). Following this line of thinking, and building on an incentive salience model of approach motivation, three studies (total N = 284) examined the differential processing of power versus affiliation stimuli in categorization, perception and approach–avoidance paradigms. All studies found interactions of the same type. In study 2, for example, people high in arrogance perceived power stimuli to be larger than affiliation stimuli, but this differential pattern was not evident at low arrogance levels. People high, but not low, in arrogance also approached power stimuli faster than affiliation stimuli in a motor movement task (study 3). The results contribute to a process–based understanding of how interpersonal arrogance functions while linking such differences to the manner in which power versus affiliation cues are perceived and reacted to. Copyright © 2014 European Association of Personality Psychology </jats:p

The representation of the verb's argument structure as disclosed by fMRI

<p>Abstract</p> <p>Background</p> <p>In the composition of an event the verb's argument structure defines the number of participants and their relationships. Previous studies indicated distinct brain responses depending on how many obligatory arguments a verb takes. The present functional magnetic resonance imaging (fMRI) study served to verify the neural structures involved in the processing of German verbs with one (e.g. "snore") or three (e.g. "gives") argument structure. Within a silent reading design, verbs were presented either in isolation or with a minimal syntactic context ("snore" vs. "Peter snores").</p> <p>Results</p> <p>Reading of isolated one-argument verbs ("snore") produced stronger BOLD responses than three-argument verbs ("gives") in the inferior temporal fusiform gyrus (BA 37) of the left hemisphere, validating previous magnetoencephalographic findings. When presented in context one-argument verbs ("Peter snores") induced more pronounced activity in the inferior frontal gyrus (IFG) of the left hemisphere than three-argument verbs ("Peter gives").</p> <p>Conclusion</p> <p>In line with previous studies our results corroborate the left temporal lobe as site of representation and the IFG as site of processing of verbs' argument structure.</p

Auditory attention enhances processing of positive and negative words in inferior and superior prefrontal cortex

Wegrzyn M, Herbert C, Ethofer T, Flaisch T, Kißler J. Auditory attention enhances processing of positive and negative words in inferior and superior prefrontal cortex. Cortex. 2017;96:31-45

Thirst and the state-dependent representation of incentive stimulus value in human motive circuitry

Abstract Depletion imposes both need and desire to drink, and potentiates the response to need-relevant cues in the environment. The present fMRI study aimed to determine which neural structures selectively increase the incentive value of needrelevant stimuli in a thirst state. Towards this end, participants were scanned twice-either in a thirst or no-thirst statewhile viewing pictures of beverages and chairs. As expected, thirst led to a selective increase in self-reported pleasantness and arousal by beverages. Increased responses to beverage when compared with chair stimuli were observed in the cingulate cortex, insular cortex and the amygdala in the thirst state, which were absent in the no-thirst condition. Enhancing the incentive value of need-relevant cues in a thirst state is a key mechanism for motivating drinking behavior. Overall, distributed regions of the motive circuitry, which are also implicated in salience processing, craving and interoception, provide a dynamic body-state dependent representation of stimulus value

First Impressions of HIV Risk: It Takes Only Milliseconds to Scan a Stranger

Research indicates that many people do not use condoms consistently but instead rely on intuition to identify sexual partners high at risk for HIV infection. The present studies examined neural correlates for first impressions of HIV risk and determined the association of perceived HIV risk with other trait characteristics. Participants were presented with 120 self-portraits retrieved from a popular online photo-sharing community (www.flickr.com). Factor analysis of various explicit ratings of trait characteristics yielded two orthogonal factors: (1) a ‘valence-approach’ factor encompassing perceived attractiveness, healthiness, valence, and approach tendencies, and (2) a ‘safeness’ factor, entailing judgments of HIV risk, trustworthiness, and responsibility. These findings suggest that HIV risk ratings systematically relate to cardinal features of a high-risk HIV stereotype. Furthermore, event-related brain potential recordings revealed neural correlates of first impressions about HIV risk. Target persons perceived as risky elicited a differential brain response in a time window from 220–340 ms and an increased late positive potential in a time window from 350–700 ms compared to those perceived as safe. These data suggest that impressions about HIV risk can be formed in a split second and despite a lack of information about the actual risk profile. Findings of neural correlates of risk impressions and their relationship to key features of the HIV risk stereotype are discussed in the context of the ‘risk as feelings’ theory