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One-year into COVID-19 pandemic: Decision-making and mental-health outcomes and their risk factors
No full textBACKGROUND: The COVID-19 pandemic represents an unprecedented worldwide crisis with serious socioeconomic, physical and mental health consequences. However, its long-lasting effects on both mental health and decision-making difficulties remain unexplored. This study aimed to determine the prevalence and severity of psychological disorders in Italy's populace one-year after the outbreak; further, we investigated potential risks impacting mental health and decision-making. METHODS: In March 2021, 586 individuals (18–73 years) completed an online-survey plus a computerized delay discounting task for hypothetical money rewards. RESULTS: Psychological symptoms prevalence exceeded the Italy's lockdown rates, with about one-third reporting moderate-to-extremely severe depression, another third anxiety, and the rest stress; mirrored by an increase of symptoms at clinically significant severity levels. One year into the pandemic, half of our sample presented at least one psychological problem, and one-third was at risk of developing a more clinically severe psychological outcome. Fear of job loss, loneliness and intolerance of uncertainty were among the major risk factors to mental health. Plus, social-relationships and financial uncertainty were key determinants of depression, while fear of COVID-19 infection predicted anxiety symptoms. For decision-making tendencies, elevated delay discounting rates, implying less future-oriented behaviors, were mostly predicted by increased job loss fear and older age (>35 years). LIMITATIONS: This study provides cross-sectional evidence. CONCLUSIONS: Depression, anxiety and stress levels were still alarming one-year into COVID-19. Individuals experiencing financial insecurity, loneliness and intolerance of uncertainty perhaps benefit most from early interventions. Governments need to implement timely recovery plans to reduce financial insecurity, given its significant mental health impact and decision-making outcomes
Cognitive and electroencephalograohic markers of healthy and pathological aging
Full text linkThe present thesis is composed of two main parts. In the first part, the effect of aging was investigated on performance and on event-related potentials (ERPs) associated with several goal-directed cognitive tasks. In the second part, cognitive and ERP changes were explored in patients with minimal hepatic encephalopathy, a syndrome characterized by cognitive and neurophysiological abnormalities in patients with liver cirrhosis.
1° PART: COGNITIVE AND ELECTROPHYSIOLOGICAL ALTERATIONS ASSOCIATED WITH HEALTHY AGING.
It is a truism that as people grow older, performance on a large number of cognitive tasks declines. These age-sensitive tasks include simple and choice reaction times (RTs) tasks, tests of episodic memory, working-memory tasks, tasks involving executive functions, spatial and reasoning abilities, mental rotation (e.g., Kausler, 1991; Salthouse, 1991). Given that deficits are so widespread across the cognitive domains, it is reasonable to assume that a limited number of mechanisms might be responsible. Different theories tried to address this issue. Some of them suggested that cognitive deficits in aging are due to a reduction in the amount of attentional resources (Craik, 1986; Craik & Byrd, 1982), or a slowing down of processing speed (Salthouse, 1996), or a decline in the inhibitory control of working-memory contents (Hasher & Zacks, 1988).
One explanation that has recently gained some prominence is the increasing impairment of executive control with age, likely related to age-specific changes in prefrontal cortex (“theory of Cognitive Control”, also called “goal maintenance account”; Braver & West, 2008; Raz, 2000; West, 1996). Executive control is intended as the ability to represent, maintain and update goal information in order to exert control over behaviour and thoughts (Cohen et al., 1996). According to Miyake and collaborators (2000), executive control is not a single function, but is composed of several cognitive sub-processes, namely shifting, updating and inhibition.
To explore the role of executive control in explaining the age-related cognitive decline, the effect of cognitive aging was measured on those tasks involving high recruitment of such ability. Specifically, the first study of the present thesis (Experiment 1) investigated the age-related changes on a time-based prospective memory (PM) task, and focused on exploring the effect of aging on ERPs. Time-based PM refers to the ability of remembering to perform an action at a specific point in the future, (for example, remembering to attend an appointment at 3 pm; Brandimonte et al., 1996; Einstein & McDaniel, 2000; Kliegel et al., 2009). A fundamental process required for successfully accomplishing PM tasks is the ability to maintain and update the PM intentions (i.e., goal information) active in memory. Such ability, being impaired based on the “theory of cognitive control”, might be the factor determining the age-related alterations observed in time-based PM tasks. The analysis of ERPs elicited in time-based PM tasks is useful to test this hypothesis, and to better clarify the mechanisms responsible for age-related alterations in these kinds of tasks.
The second study focused on the relationship between executive control and cognitive aging by comparing performance of older and younger adults on a task in which the executive control load was manipulated. The task, called Inhibitory Control task (ICT; Bajaj et al., 2008a), is indeed composed of three different conditions, which varies for the executive resources needed. I expected that, if the executive control is the key factor responsible for cognitive impairment in aging, thus the deleterious effect of age on performance would be greater as the executive load increases. Moreover, ICT provides an investigation of the age-related alterations on ERPs associated with the different processes composing executive control, such as updating, shifting, and response inhibition (Miyake et al., 2000).
The two studies will be described in details below.
Experiment 1: ERP mechanisms underlying age-related alterations in Time-Based Prospective Memory.
There is a general agreement, across studies on PM, towards a deleterious effect of age on time-based PM performance (Bastin & Meulemans, 2002; McDaniel & Einstein, 1992; Park et al., 1997; see Henry, MacLeod, Phillips, & Crawford, 2004, for a review).
According to Craik’s theory (Craik, 1986), since in PM tasks there are no explicit prompts from the environment that instigate the retrieval of intention, individuals need to engage self-initiated and attentional demanding processes to retrieve the PM intentions. Given that aging is associated with a reduction in the availability of these attentional resources, thus PM performance would be altered in older people.
On the other hand, according to the “theory of cognitive control” (or “goal maintenance account”; Braver & West, 2008), older adults have difficulties in the maintenance of goal representations over an extended period. In the case of time-based PM, failure to maintain active the goal (i.e., the intention) would lead to failure to correctly execute the intended action.
Although a large number of studies investigated the impairment of time-based PM with aging, nevertheless none study has ever focused on neural activity underpinning such alterations. Therefore, in order to shed light on such poorly investigated issue, the present study explored the age-related alterations in the electrophysiological correlates of time-based PM tasks.
To this end, ERPs associated with ongoing task (i.e., a task executed concurrently with the PM task) were examined in 18 older and 15 younger adults and compared between a baseline block, in which individuals were required to perform merely the ongoing task; and a PM block, in which individuals were required to perform simultaneously the ongoing and the PM tasks. The ongoing task consisted in evaluating in five-letter strings whether the letters in second and fourth positions (target positions) were equal or different by pressing one of two possible keys. In the PM task, participants were required to remember to press the “PM key” every five minutes from the beginning of the block. To help them to estimating the passing of time, they had the opportunity to check the digital clock in any moment of the task by pressing another key. The ERPs were locked to ongoing trials (i.e., the strings of letter). Reaction times, accuracy and ERPs relative to ongoing trials were compared between the baseline and the PM block, for both younger and older adults. Moreover, the percentage of accuracy in PM task and the number of clock checks were recorded.
Concerning the behavioural results, older adults showed a lower percentage of accuracy in PM task respect to younger adults. Moreover, the older adults displayed a slowing down of RTs in the ongoing task, both in the baseline and in PM block, as compared to younger adults.
Concerning the ERPs of younger adults, the addition of a time-based PM task to an ongoing activity led to a sustained positive modulation of the ERPs elicited by the ongoing trials, mainly expressed over prefrontal and frontal regions. This frontal activity seems to reflect the load of maintaining the intention active in memory, as recently suggested (Cona et al., in press; West et al., 2011). On the other hand, in older adults these ERP modulations were more expressed over posterior regions. Interesting, a difference in the ERP amplitude between baseline and PM block was observed over prefrontal sites in younger adults (with the ERPs being more positive in PM block), but not in older adults. At first glance, the absence of the prefrontal mofulation in older adults seems to reflect their difficulties in keeping the PM intention in mind, as suggested by the “theory of cognitive control” (Braver & West, 2008).
Nevertheless, the exploration of the ERP differences as observed between the two groups in the baseline block allowed to better clarify the mechanisms responsible of these age-related changes in PM. Indeed in baseline block, compared to younger adults, older adults showed a lower P300 over parietal regions, and a higher P300 over prefrontal regions. The anteriorisation of the P300 shown by older adults has been well documented in literature (Daffner et al., 2006; 2011), and it is supposed to reflect the greater recruitment of attentional resources to compensate for olders’ difficulties in the ongoing task.
Taken together, these results suggest that older adults had difficulties already in the baseline block, and cope with such difficulties by recruiting additional frontal resources (as reflected by the anteriorisation of P300). If too many resources were allocated to perform the ongoing task, then fewer resources would be available to adequately maintain the intentions in memory, leading to an impaired PM performance. Therefore, it seems more reasonable that the decline in executive control, required for intention maintenance, is not the primary cause of the age-related changes in PM tasks, but rather is itself the consequence of a reduced amount of available resources, as postulated by Craik’s theory (1986).
Experiment 2: Influence of aging on ERP correlates of
executive control processes.
According to the “theory of cognitive control” (Braver & West, 2008), an age-related impairment in executive control is hypothesized to determine specific decrements in those cognitive tasks that are more demanding for that function. In order to test this prediction, we adopted the Inhibitory Control task (ICT; Bajaj et al., 2008a). During the ICT, a continuous stream of letters is presented, very quickly, one after the other. In the first part of the task, it is required to respond by pressing a key only to the target letters (i.e., “X” and “Y,”). Trials containing a target letter are labelled as Detect trials. In the second part, it is required to respond whenever the target letters are alternated (Go trials), as when an “X” is preceded by a “Y”, or vice versa, regardless of the irrelevant letters presented between them. In contrast, it must withhold response if target letters are repeated (Nogo trials), as when an “X” precedes another “X”, or a “Y” precedes another “Y”. In light of this, ICT includes trials requiring different demands of executive control. Detect trials requires to merely pay selective attention and to respond to specific stimuli. These trials are relatively low demanding in terms of executive control. Go trials are more demanding, implying the process of working memory updating. Finally, Nogo trials are the highest demanding trials since imply not only an updating process but also inhibitory control of response. According to the theory of control, differences on ICT performance between younger and older adults should be lowest in detect trials, intermediate in go trials and greatest in nogo trials.
Furthermore, this study was aimed at investigating the effect of age on the different processes composing the executive control (Miyake et al., 2000). Therefore it was explored the influence of aging on peak latency and amplitude of P3b, nogo-P3 and RON (i.e., reorienting negativity) components, which reflect updating, inhibition, and shifting processes, respectively. In order to better dissociate the ERP components related to these different processes, a partial least square (PLS) analysis was run. Seventeen younger and sixteen older adults performed the ICT.
Against the formulated predictions, older adults exhibited a worse performance in all kinds of trial, as from detect trials to nogo trials. More importantly, the age effect did not interact with the type of trials, hence was independent from the degree of executive control required to perform them. This means that executive control, when formulated as a unitary construct responsible for the age-related deficits in cognition, does not seem to be the elective factor for explaining the deficits shown in ICT task. In line with behavioural results, older adults showed a delay in all the ERP components studied (P3b, N2, RON, nogo-P3), regardless of the type of trial. These age-related alterations in the latency of the ERPs seem to reflect a slowing of speed of cognitive processing in the elderly individuals. Such an idea gives support to Sathouse's theory (Salthouse, 1996), which assumed that age-related cognitive decline might be due to a general reduction in the speed of processing.
Another relevant finding consists in the fact that the RON components were found particularly sensitive to aging. Specifically, these components, reflecting attentional shifting (Berti et al., 2008), were shown delayed and reduced in older adults. To my knowledge, only one study has investigated the age-related alterations in the RON components before, but utilizing an auditory distraction-paradigm (Horváth et al., 2009). Thus, the present study extended the results obtained in the work by Horváth, suggesting that the age-related impairment of attentional shifting occurred not only after distracter stimuli (as found by Horváth), but also after task-relevant ones. It suggests that in older adults shifting mechanism of attention take longer and is more effortful, probably because they are still engaged in processing the previous stimulus. Summarizing, electrophysiological and behavioural data converged in revealing that age-related cognitive impairment might be, at least partially, attributable to a general slowing of information processes. Indeed, coherently with the review by Verhaegen (2011), reduction on processing speed seems to explain cognitive deficits in elderly better than deterioration in executive control, when this is conceptualized as a unitary construct. On the other hand, a subprocess of executive control, attentional shifting, resulted particularly affected by age, and it could be another candidate to explain multiple age-related cognitive alterations.
1° Part: Conclusions
Although the present studies utilized different paradigms and tasks, they converged in revealing that executive control does not play a crucial role in determining the age-related deficits seen in these tasks. Rather, a decline in more basic, or lower-level, mechanisms seems to be the key factor to explain the multitude of age-related cognitive deficits. Specifically, the analysis of the ERPs allowed to highlight that age-related alterations were more likely due to a reduction: 1) in the amount of available resources and 2) in processing speed.
The age-related alterations concerned mainly ERPs over prefrontal regions and were they were mainly expressed as delay in the ERP latencies. Interestingly, compensatory mechanisms in older adults were also observed, and were reflected in the increase of amplitude of several components (respect to the younger adults). This led to the suggestion that aging does not simply mean cognitive and neural decline, but may also involve adaptive cognitive and neural responses.
2° PART: COGNITIVE AND ELECTROPHYSIOLOGICAL ALTERATIONS ASSOCIATED WITH MINIMAL HEPATIC ENCEPHALOPATHY.
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome occurring in acute or chronic liver failure. The detection of the first, sometimes apparently negligible, signs of hepatic encephalopathy is greatly important since this condition, called minimal hepatic encephalopathy (MHE; Ferenci et al., 1998), impinges on the health-related quality of life (Groeneweg et al., 1998; Zhou et al. 2009) and it is likely to affect driving ability (Wein et al., 2004). Furthermore, it has a negative prognostic value in relation to the occurrence of both bouts of overt hepatic encephalopathy and death (Amodio et al., 1999; Romero-Gomez et al., 2007). The profile of MHE is characterized by cognitive alterations that involve selective attention and executive functions, visuomotor ability, psychomotor speed, response inhibition, and response selection (Amodio et al., 2005). MHE also causes brain dysfunction detectable by slowing of the electroencephalogram (EEG) and prolonged ERPs, such as P300 (Amodio et al., 2005; Weissenborn et al., 2005). Therefore, where possible, the diagnosis of MHE is preferably based on a combination of psychometric and neurophysiological/psychophysiological tools.
The inhibitory control task (ICT) has been recently proposed as a simple diagnostic tool for MHE (Bajaj et al., 2007; 2008a). However, its applicability to different populations of patients with cirrhosis and its relation to other measures of MHE need to be confirmed. Therefore, Experiment 3 was designed to address this issue and was aimed at assessing the specificity and sensitivity of ICT for the diagnosis of MHE. The Experiment 4 focused on the effect of MHE on the ERPs elicited by ICT, in order to highlight cognitive and electrophysiological alterations characterizing MHE.
In order to further investigate the electrophysiological alterations of MHE, another study (Experiment 5) explored the intra-individual variability (IIV) of P300 parameters (i.e., latency and amplitude) in cirrhotic patients with MHE. There is an increasing interest in IIV of cognitive performance (e.g., of RTs) within the field of cognitive neuroscience (MacDonald et al., 2006), since IIV has been widely considered to be a behavioral indicator of compromised neural mechanisms (e.g., Hultsch, et al., 2000). Nevertheless, studies establishing links between intra-individual variability in behavioral and brain responses are sparse, with most evidence being indirect. MHE seems to be a suitable model of pathology for studying this relation, given that patients with MHE showed increased IIV of RTs (Elssas et al., 1985; Schiff et al., 2006).
Therefore, in Experiment 5, single-trial P300 parameters, obtained by means of a single-trial Bayesian estimation technique (D’Avanzo et al., 2011), were estimated to investigate the electrophysiological correlates of IIV of response speed and the relation between P300 parameters and RTs in normal individuals and in a population of patients with and without MHE.
Experiment 3 and 4:
The ICT as a suitable tool for detecting cognitive and ERP alterations in patients with liver cirrhosis.
In Experiment 3, seventy-five patients with cirrhosis and 55 healthy controls underwent the ICT in 2 reference centers for the study of hepatic encephalopathy. Patients were evaluated for MHE by psychometric hepatic encephalopathy score (PHES) and spectral electroencephalogram analyses. Performance on go and nogo trials was compared between the two groups. Patients with cirrhosis exhibited a higher number of errors in nogo trials (i.e., lures), and lower accuracy in go trials, as compared with controls. However, the number of lures was comparable among patients with and without MHE. Importantly, an inverse relation between accuracy in go trials and number of lures was shown when the go accuracy was particularly low. However this is not surprising: a low accuracy in go trials indicates that many trials had a missing response (in go trial an error is a missed response), but if a participant commits many missing responses, he/she is more likely to “perform” correctly on nogo trials (hence to not respond when actually it is required to not respond). In light of this, the low number of error in nogo trials is a spurious effect. Hence, a new variable (weighted lures) was codified, adjusting the number of lures based on go accuracy. This variable distinguished between patients with and without MHE. However, accuracy in go trials alone was as effective as a stand-alone variable. Therefore, testing inhibition (lures) does not seem to be superior to testing attention and working memory updating (go accuracy) for the detection of MHE.
In Experiment 4 the electrophysiological alterations related to cirrhosis were investigated in the ICT task by comparing ERPs in cirrhotic patients with MHE (N=13), without MHE (N=18) with ERPs in healthy controls (N=17). Specifically, the ERPs in detect, go and nogo trials were measured, reflecting processes of selective attention, working memory updating, and inhibition, respectively. Data were further analysed by means of a PLS analysis, was particularly suited to dissociate the ERP correlates of the different subprocesses. Findings from ANOVA and PLS analysis converged in showing selective alterations of the ERPs on detect trials in patients with MHE. Specifically these included a reduction in P3a amplitude over frontocentral sites and a delay in the P3b latency. Since detect trials involve principally attentional processes, alterations on these trials may indicate that MHE is associated with an impairment of low-level cognitive abilities, such as attention. This result corroborated the claim of Experiment 3, concerning the appropriateness to test for low-level abilities (i.e., attention) before, or together with, testing for high-level abilities (i.e., inhibition) for the diagnosis of MHE (Amodio et al., 2010). The second main, and unexpected, finding was the enhancement of several ERP components (namely, the N2 and nogo-P3) in cirrhotic patients without MHE. These electrophysiological changes might be a compensatory mechanism, reflecting the allocation of additional executive resources for overcoming the difficulties of the task (indeed, also patients without MHE had a reduction of P3a, which is an index of attentional processes).
Experiment 5: The IIV of P300 as an index for detecting neural dysfunctions in patients with liver cirrhosis
In patients with cirrhosis, an increased intra-individual variability of RTs has been described and qualified as a potential early sign of brain dysfunction (Schiff et a
Supplementary motor area as key structure for domain-general sequence processing: A unified account
No full textThe Supplementary Motor Area (SMA) is considered as an anatomically and functionally heterogeneous region and is implicated in several functions. We propose that SMA plays a crucial role in domain-general sequence processes, contributing to the integration of sequential elements into higher-order representations regardless of the nature of such elements (e.g., motor, temporal, spatial, numerical, linguistic, etc.). This review emphasizes the domain-general involvement of the SMA, as this region has been found to support sequence operations in a variety of cognitive domains that, albeit different, share an inherent sequence processing. These include action, time and spatial processing, numerical cognition, music and language processing, and working memory. In this light, we reviewed and synthesized recent neuroimaging, stimulation and electrophysiological studies in order to compare and reconcile the distinct sources of data by proposing a unifying account for the role of the SMA. We also discussed the differential contribution of the pre-SMA and SMA-proper in sequence operations, and possible neural mechanisms by which such operations are executed
Is cognitive control automatic? New insights from transcranial magnetic stimulation
No full textCognitive control has been classically considered as a flexible process engaged to pursue intentional behaviors, as distinct from automatic processes, which are unintentional, inflexible, and triggered by unconscious mechanisms. Our study challenged this view, showing that such a distinction may not be so clear-cut. We analyzed motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation to investigate the neurocognitive mechanisms occurring in a conflict task during trials that either required or did not require a response. We observed a Simon effect on MEPs and sequential modulations of such effects on both kinds of trials. Sequential modulations are usually explained as resulting from the engagement of intentional control mechanisms. Our findings rule against this idea, suggesting that these effects are the result of a mechanism that detects and resolves conflict even when there is no intention to select any response. Accordingly, cognitive control also seems to operate without intention, acting in an automatic fashion
TMS of supplementary motor area (SMA) facilitates mental rotation performance: Evidence for sequence processing in SMA
Full text linkIn the present study we applied online transcranial magnetic stimulation (TMS) bursts at 10Hz to the supplementary motor area (SMA) and primary motor cortex to test whether these regions are causally involved in mental rotation. Furthermore, in order to investigate what is the specific role played by SMA and primary motor cortex, two mental rotation tasks were used, which included pictures of hands and abstract objects, respectively. While primary motor cortex stimulation did not affect mental rotation performance, SMA stimulation improved the performance in the task with object stimuli, and only for the pairs of stimuli that had higher angular disparity between each other (i.e., 100° and 150°). The finding that the effect of SMA stimulation was modulated by the amount of spatial orientation information indicates that SMA is causally involved in the very act of mental rotation. More specifically, we propose that SMA mediates domain-general sequence processes, likely required to accumulate and integrate information that are, in this context, spatial. The possible physiological mechanisms underlying the facilitation of performance due to SMA stimulation are discussed
The Effects of Focal and Nonfocal Cues on the Neural Correlates of Prospective Memory: Insights From ERPs
No full textSuperior parietal cortex and the attention to delayed intention: An rTMS study.
Full text linkThis study aimed to investigate whether the superior parietal cortex is causally involved in PM and, if so, what is
its functional role. We applied repetitive transcranial magnetic stimulation (rTMS) to the left and right superior
parietal cortex, and we evaluated the TMS effects on two different PM tasks that required to direct the attention
towards either the external stimuli (‘Monitoring-load’ task) or the intention in memory (‘Retrospective-load’
task).
rTMS of left parietal cortex produced a facilitation of PM performance in both tasks. This was coupled by
slower responses to the ongoing activity, for left and right parietal stimulation, but selectively in the
‘Retrospective-load’ condition.
The present results suggest that superior parietal cortex is causally involved in biasing top-down attentional
resources between the external, ongoing stimuli and the internal, PM intentions. The possible physiological
mechanisms underlying the TMS-related improvement in PM performance are discussed
‘Mens sana in corpore sano’: Cognitive functioning predicts race performance in ultra-marathon runners.
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