Cognitive Control: beyond priming, in aging and across domains

This research project aimed to address many issues related to cognitive control, such as its relationship with repetition priming, its modification in older adults and whether it can be considered a general supra-modality mechanism or rather a set of domain specific ones. The cognitive control mechanism is a top-down modulation involved in conflict resolution processes that is supposed to facilitate the discrimination between signal and noise, or targets and distractors. In the present project cognitive control was investigated through the analysis of congruency (Stroop) and sequential congruency effects with a modification of verbal and spatial Stroop paradigms that exclude the priming confound in two consecutive trials. Results revealed that both congruency and sequential congruency effects are strongly modulated by repetition priming in a verbal Stroop task, whereas a spatial Stroop is only marginally influenced. The comparison of conflict measures and conflict-related ERPs showed that the mechanisms involved in the verbal and spatial tasks are only partially comparable. Both tasks showed congruency effects consistent with previous findings, while sequential congruency effects are apparent in the spatial Stroop performance but are reduced in the verbal task with respect to what is reported in previous studies. In the verbal task we pointed out that cognitive control is likely to detect not the actual conflict level but rather the conflict level change in the present trial with respect to the preceding one and consequently adjust attentional resources, exerting a direct influence on performance. On the other hand, some previous studies suggested that whenever a task presents a high conflict level a proactive inhibition state is activated in order to prevent automatic responses. The results from the spatial Stroop task suggested that the attentional regulatory mechanism for spatial conflict is likely to modulate this proactive inhibition default state on the basis of the preceding trial congruency. In this domain the modulations due to preceding trial congruency and the one due to current trial congruency do not interact in determining ERP components, and this probably generates the strong conflict sequential effects seen in the behavioural performance. Many cognitive aging theories assume a progressive decline in frontal brain areas and many authors reported an age-related deficit in conflict resolution abilities in varied conflict-related tasks, which goes beyond the general slowing showed by older adults. We investigated the effects of normal aging on cognitive control in the verbal and spatial domains, highlighting the fact that the age-related general slowing can account for most of the difference found between younger and older adults, and that the verbal congruency effect is the only measure that suffers from a specific decline. Moreover intelligence and cognitive reserve (CR) seemed to partially account for the inter-individual variability in conflict resolution performance, especially in cognitive aging. Finally, the hypothesis of a general, supra-domain cognitive control mechanism is discussed, since evidence reported in the present project rather supports the existence of more domain specific sub-mechanisms of cognitive control

Conflict Resolution and Adaptation in Normal Aging: The Role of Verbal Intelligence and Cognitive Reserve.

The present study investigated effects of cognitive aging on conflict resolution (the ability to suppress prepotent and distracting, irrelevant information) and conflict adaptation (the adjustment of conflict resolution based on previously experienced conflict level). In addition, it aimed at investigating whether Cognitive Reserve (CR) and intelligence play a compensatory role against age-related deficits in both factors. A color-word Stroop task with no feature repetitions (i.e., neither the word nor the color was repeated in two subsequent trials) was administered to 23 older adults with no dimentia (65-79 years old) and 22 younger controls (18-34 years old), in addition to measures of intelligence and CR. Older adults' performance was characterized by general slowing. However, response slowing inversely correlated with intelligence, education, and a cognitive-reserve index. The Stroop effect (i.e., response-time (RT) difference between incongruent and congruent conditions) was larger in older adults than in younger controls, and in the older group only, it negatively correlated with verbal IQ. With this feature-repetitions-free Stroop task, we confirmed the presence of some conflict adaptation effects, which, however, were spared by aging. Altogether, these findings show that older adults can cope better with age-related impairment in verbal interference resolution, if they have enough intelligence resources in a related (verbal) domain, whereas CR plays a role in general performance speed only. We therefore suggest that general and specific accounts of cognitive aging may apply to different processing stages, which are influenced by partially different compensatory factors

Brain oscillations in cognitive control: a cross-sectional study with a spatial Stroop task

An important aspect of cognitive control is the ability to overcome interference, by boosting the processing of task-relevant information while suppressing the irrelevant information. This ability is affected by the progressive cognitive decline observed in aging. The aims of this study were to shed light on the neural spectral dynamics involved in interference control and to investigate age-dependent differences in these dynamics. For these reasons two samples of participants of different ages (23 younger and 20 older adults, age range = [18 35] and [66 82], respectively) were recruited and administered a spatial Stroop task while recording electroencephalographic activity. Scalp- and source-based time-frequency analyses revealed a main role of theta and beta frequencies in interference control. Specifically, for the theta band, we found age-dependent differences both for early event-related spectral perturbation (ERSP) Stroop effects at the source level – which involved dorsomedial and dorsolateral prefrontal cortices – and for related brain-behaviour correlations. This ERSP Stroop effect in theta was greatly reduced in magnitude in the older group and, differently from what observed in younger participants, it was not correlated with behavioural performance. These results suggest an age-dependent impairment of the theta-related mechanism signalling the need of cognitive control, in line with existing findings. We also found age-related differences in ERSP and source spectral activity involving beta frequencies. Indeed, younger participants showed a specific ERSP Stroop effect in beta – with the main involvement of left prefrontal cortex – whereas the pattern of older participants was delayed in time and spread bilaterally over the scalp. This study shows clear age-related differences in the neural spectral correlates of cognitive control. These findings open new questions about the causal involvement of specific oscillations in different cognitive processes and may inspire future interventions against age-related cognitive decline

Anterior corpus callosotomy in patients with drug-resistant epilepsy: Invasive EEG findings and seizure outcomes

Corpus callosotomy (CC) is used in patients with drug-resistant seizures who are not candidates for excisional surgery and failed neurostimulation. We examined ictal scalp and intracranial electroencephalogram (iEEG) recordings in 16 patients being evaluated for anterior CC alone or CC in combination with focal resection, to determine the role of the iEEG in predicting postoperative seizure outcomes. In our cohort, CC improved generalized atonic seizures and focal seizures with impaired awareness but did not alter outcomes for generalized tonic–clonic or tonic seizures. Invasive EEG prior to CC did not refine the prediction of postsurgical seizure outcomes in patients with inconclusive scalp EEG. Keywords: Epilepsy surgery, Refractory seizures, Intracranial EEG, Corpus callosotom

Alirocumab and cardiovascular outcomes after acute coronary syndrome

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