Structural and functional differences in medial prefrontal cortex underlie distractibility and suppression deficits in ageing.

Older adults experience deficits in working memory (WM) that are acutely exacerbated by the presence of distracting information. Human neurophysiological studies have revealed that these changes are accompanied by a diminished ability to suppress visual cortical activity associated with task-irrelevant information. Although this is often attributed to deficits in top-down control from a prefrontal cortical source, this has not yet been directly demonstrated. Here we evaluate the neural basis of distraction's negative impact on WM and the impairment in neural suppression in older adults by performing structural and functional MRIs while older participants engage in tasks that require remembering relevant visual stimuli in the context of overlapping irrelevant stimuli. Analysis supports both an age-related distraction effect and neural suppression deficit, and extends our understanding by revealing an alteration in functional connectivity between visual cortices and a region in the default network, the medial prefrontal cortex (mPFC). Moreover, within the older population, the magnitude of WM distractibility and neural suppression are both associated with individual differences in cortical volume and activity of the mPFC, as well as its associated white-matter tracts

Hippocampus dependent and independent theta-networks of working memory maintenance

Working memory is the ability to briefly maintain and manipulate information beyond its transient availability to our senses. This process of short-term stimulus retention has often been proposed to be anatomically distinct from long-term forms of memory. Although it’s been well established that the medial temporal lobe (MTL) is critical to long-term declarative memory, recent evidence has suggested that MTL regions, such as the hippocampus, may also be involved in the working memory maintenance of configural visual relationships. I investigate this possibility in a series of experiments using Magnetoencephalography to record the cortical oscillatory activity within the theta frequency band of patients with bilateral hippocampal sclerosis and normal controls. The results demonstrate that working memory maintenance of configural-relational information is supported by a theta synchronous network coupling frontal, temporal and occipital visual areas, and furthermore that this theta synchrony is critically dependent on the integrity of the hippocampus. Alternate forms of working memory maintenance, that do not require the relational binding of visual configurations, engage dissociable theta synchronous networks functioning independently of the hippocampus. In closing, I will explore the interactions between long-term and short-term forms of memory and demonstrate that through these interactions, memory performance can effectively be improved

The Impact of Anxiety-Inducing Distraction on Cognitive Performance: A Combined Brain Imaging and Personality Investigation

BACKGROUND: Previous investigations revealed that the impact of task-irrelevant emotional distraction on ongoing goal-oriented cognitive processing is linked to opposite patterns of activation in emotional and perceptual vs. cognitive control/executive brain regions. However, little is known about the role of individual variations in these responses. The present study investigated the effect of trait anxiety on the neural responses mediating the impact of transient anxiety-inducing task-irrelevant distraction on cognitive performance, and on the neural correlates of coping with such distraction. We investigated whether activity in the brain regions sensitive to emotional distraction would show dissociable patterns of co-variation with measures indexing individual variations in trait anxiety and cognitive performance. METHODOLOGY/PRINCIPAL FINDINGS: Event-related fMRI data, recorded while healthy female participants performed a delayed-response working memory (WM) task with distraction, were investigated in conjunction with behavioural measures that assessed individual variations in both trait anxiety and WM performance. Consistent with increased sensitivity to emotional cues in high anxiety, specific perceptual areas (fusiform gyrus--FG) exhibited increased activity that was positively correlated with trait anxiety and negatively correlated with WM performance, whereas specific executive regions (right lateral prefrontal cortex--PFC) exhibited decreased activity that was negatively correlated with trait anxiety. The study also identified a role of the medial and left lateral PFC in coping with distraction, as opposed to reflecting a detrimental impact of emotional distraction. CONCLUSIONS: These findings provide initial evidence concerning the neural mechanisms sensitive to individual variations in trait anxiety and WM performance, which dissociate the detrimental impact of emotion distraction and the engagement of mechanisms to cope with distracting emotions. Our study sheds light on the neural correlates of emotion-cognition interactions in normal behaviour, which has implications for understanding factors that may influence susceptibility to affective disorders, in general, and to anxiety disorders, in particular

The cognitive neuroscience of visual working memory

Visual working memory allows us to temporarily maintain and manipulate visual information in order to solve a task. The study of the brain mechanisms underlying this function began more than half a century ago, with Scoville and Milner’s (1957) seminal discoveries with amnesic patients. This timely collection of papers brings together diverse perspectives on the cognitive neuroscience of visual working memory from multiple fields that have traditionally been fairly disjointed: human neuroimaging, electrophysiological, behavioural and animal lesion studies, investigating both the developing and the adult brain

Serotonin transporter gene polymorphisms and brain function during emotional distraction from cognitive processing in posttraumatic stress disorder

BACKGROUND: Serotonergic system dysfunction has been implicated in posttraumatic stress disorder (PTSD). Genetic polymorphisms associated with serotonin signaling may predict differences in brain circuitry involved in emotion processing and deficits associated with PTSD. In healthy individuals, common functional polymorphisms in the serotonin transporter gene (SLC6A4) have been shown to modulate amygdala and prefrontal cortex (PFC) activity in response to salient emotional stimuli. Similar patterns of differential neural responses to emotional stimuli have been demonstrated in PTSD but genetic factors influencing these activations have yet to be examined. METHODS: We investigated whether SLC6A4 promoter polymorphisms (5-HTTLPR, rs25531) and several downstream single nucleotide polymorphisms (SNPs) modulated activity of brain regions involved in the cognitive control of emotion in post-9/11 veterans with PTSD. We used functional MRI to examine neural activity in a PTSD group (n = 22) and a trauma-exposed control group (n = 20) in response to trauma-related images presented as task-irrelevant distractors during the active maintenance period of a delayed-response working memory task. Regions of interest were derived by contrasting activation for the most distracting and least distracting conditions across participants. RESULTS: In patients with PTSD, when compared to trauma-exposed controls, rs16965628 (associated with serotonin transporter gene expression) modulated task-related ventrolateral PFC activation and 5-HTTLPR tended to modulate left amygdala activation. Subsequent to combat-related trauma, these SLC6A4 polymorphisms may bias serotonin signaling and the neural circuitry mediating cognitive control of emotion in patients with PTSD. CONCLUSIONS: The SLC6A4 SNP rs16965628 and 5-HTTLPR are associated with a bias in neural responses to traumatic reminders and cognitive control of emotions in patients with PTSD. Functional MRI may help identify intermediate phenotypes and dimensions of PTSD that clarify the functional link between genes and disease phenotype, and also highlight features of PTSD that show more proximal influence of susceptibility genes compared to current clinical categorizations

The role of prefrontal cortex in working-memory capacity, executive attention, and general fluid intelligence: An individual-differences perspective

We provide an "executive-attention" framework for organizing the cognitive neuroscience research on the constructs of working-memory capacity (WMC), general fluid intelligence, and prefrontal cortex (PFC) function. Rather than provide a novel theory of PFC function, we synthesize a wealth of single-cell, brain-imaging, and neuropsychological research through the lens of our theory of normal individual differences in WMC and attention control (Engle, Kane, & Tuholski, 1999; Engle, Tuholski, Laughlin, & Conway, 1999). Our critical review confirms the prevalent view that dorsolateral PFC circuitry is critical to executive-attention functions. Moreover, although the dorsolateral PFC is but one critical structure in a network of anterior and posterior "attention control" areas, it does have a unique executive-attention role in actively maintaining access to stimulus representations and goals in interference-rich contexts. Our review suggests the utility of an executive-attention framework for guiding future re-search on both PFC function and cognitive control

Synchronized brain activity during rehearsal and short-term memory disruption by irrelevant speech is affected by recall mode

EEG coherence as a measure of synchronization of brain activity was used to investigate effects of irrelevant speech. In a delayed serial recall paradigm 21 healthy participants retained verbal items over a 10-s delay with and without interfering irrelevant speech. Recall after the delay was varied in two modes (spoken vs. written). Behavioral data showed the classic irrelevant speech effect and a superiority of written over spoken recall mode. Coherence, however, was more sensitive to processing characteristics and showed interactions between the irrelevant speech effect and recall mode during the rehearsal delay in theta (4–7.5 Hz), alpha (8–12 Hz), beta (13–20 Hz), and gamma (35–47 Hz) frequency bands. For gamma, a rehearsal-related decrease of the duration of high coherence due to presentation of irrelevant speech was found in a left-lateralized fronto-central and centro-temporal network only in spoken but not in written recall. In theta, coherence at predominantly fronto-parietal electrode combinations was indicative for memory demands and varied with individual working memory capacity assessed by digit span. Alpha coherence revealed similar results and patterns as theta coherence. In beta, a left-hemispheric network showed longer high synchronizations due to irrelevant speech only in written recall mode. EEG results suggest that mode of recall is critical for processing already during the retention period of a delayed serial recall task. Moreover, the finding that different networks are engaged with different recall modes shows that the disrupting effect of irrelevant speech is not a unitary mechanism

The Role of Temporal Distraction on Short-Term Memory and Delayed Recognition

Memory is a complex process that requires the translation of information from an external sensory experience into an internal representation. Once information has been translated into memory, there is little agreement regarding the cognitive structure of memory storage and maintenance. Baddeley (1966) developed a model based on a multi-storage structure which suggested that as information entered through the sensory system, it was relayed by a cognitive control center and placed into storage units based on information type (i.e. auditory, visual, etc.). Baddeley’s (1966) multi-store memory model hypothesized that content translated into memory by two phases: short-term and long-term memory. More recent research supports a unitary model that better accounts for the translation of information from short term memory (STM) to long term memory (LTM) (Jost et al., 2012; Jonides et al., 2008). However, there is still uncertainty of a unitary memory model due to disagreement of the role of distractions during memory translation. The impact of distraction on this process is largely unknown. Understanding the role of distraction during STM encoding and how it affects the formation of LTM can potentially inform treatment for impaired memory. We explored the impact of temporal distractions on short-term memory and delayed recognition for visual content within a modified behavioral task based on Sternberg’s recognition task. Results indicated a negative impact of distractors on memory translation. Implications for future research were discuss to include clinical populations

Function and dysfunction of the prefrontal cortex: effects of distraction on active maintenance in healthy controls and individuals with schizophrenia

The prefrontal cortex (PFC) is thought to be critical for the active maintenance of goal-related information in the face of distraction. Previous studies have demonstrated that schizophrenia is associated with changes in the function of the PFC, and is characterized by difficulties in the active maintenance of information in working memory and in the ability to resist distraction. Two functional neuroimaging experiments were conducted with healthy control participants that examined the effects of distracter demand on working memory by manipulating both voluntary attention to distracters ("executive") and involuntary capture of attention by emotional distracters. Two additional behavioral experiments were conducted to assess how processing of these types of distracters would be affected in individuals with schizophrenia. It was expected that specific prefrontal subregions would be differentially recruited under conditions of increased distracter demand, and that the group with schizophrenia would be disproportionately affected by executive, but not emotional distraction. The results largely supported the hypotheses, and indicated that the ventrolateral PFC was specifically recruited during both executive and emotional distraction. The dorsolateral PFC was activated during both active maintenance and executive distraction processes, but its activity was significantly disrupted during emotional distraction. The group with schizophrenia also showed specific impairments in the allocation of attention to executive distracters, but showed similar patterns to controls during emotional distraction. The findings suggest that prefrontal subregions may take on specific roles in resolving interference, and that dysfunction in these regions may underlie changes in distracter processing in schizophrenia