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Background One of the main features of addictive behaviors is the inability to wait for an action, that is, the waiting impulsivity. It has been suggested that potential therapeutic tools for addiction, such as transcranial Direct Current Stimulation (tDCS), might focus on this inability. Nonetheless, whereas there is consensus about the role of prefrontal cortex on impulsivity behavior, the effects of tDCS in waiting impulsivity and underlying electrophysiological (EEG) markers are still not clear. Objective The study aimed the neuromodulation of right inferior frontal gyrus during a task designed to elicit premature responses, while EEG markers important in reward anticipation (i.e., cue and target-P3 and underlying delta/theta activity) were studied. Methods Forty healthy subjects participated in two experimental sessions, where they received active and sham tDCS while performing a premature responding task and the EEG was recorded. At next, participants performed two control tasks to evaluate transfer effects for delay discounting and motor inhibition abilities. Results Active tDCS decreased amplitude in cue-P3, target-P3, and delta activity during target-P3. On the other hand, active tDCS increased the discounting of future rewards in small values in comparison with sham, while no tDCS effects were found in motor inhibition. Conclusion These findings suggest tDCS-induced modulation of the P3 component and underlying oscillatory activity during waiting impulsivity. Moreover, these changes were associated with differences in the discounting of future rewards. Thus, the current study suggests the usefulness of tDCS in modulating impulsive processes and the relationship between P3, the inherent delta activity, and reward processing.

The ability to inhibit incorrect behaviors is crucial for survival. In real contexts, cues that require stopping usually appear intermixed with indications to continue the ongoing action. However, in the classical Stop-signal task (SST), the unpredictable stimuli are always signals that require inhibition. To understand the neural mechanisms activated by low-probability nonstop cues, we recorded the electroencephalography from 23 young volunteers while they performed a modified SST where the unpredictable stimuli could be either Stop or confirmatory Go signals (CGo). To isolate the influence of motor output, the SST was performed during overt and covert execution. We found that, paradoxically, CGo stimuli activated motor inhibition processes, and evoked patterns of brain activity similar to those obtained after Stop signals (N2/P3 event-related potentials and midfrontal theta power increase), though in lesser magnitude. These patterns were also observed during the imagined performance. Finally, applying machine learning procedures, we found that the brain activity evoked after CGo versus Stop signals can be classified above chance during both, overt and imagined execution. Our results provide evidence that unpredictable signals cause motor inhibition even when they require to continue an ongoing action This work was supported by funding from the Galician Government (Consellería de Cultura, Educación e Ordenación Universitaria; Axudas para a consolidación e Estruturación de unidades de investigación competitivas do Sistema universitario de Galicia; grant number Ref:: ED431C 2021/04.); and from Fundação para a Ciência e a Tecnologia––Scientific Employment Stimulus (CEECIND/02639/2017 to A.G.V.) SI

Cognitive Reserve (CR) is considered a protective factor during the aging process. However, although CR is a multifactorial construct, it has been operationalized in a unitary way (years of formal education or IQ). In the present study, a validated measure to categorize CR holistically (Cognitive Reserve Index Questionnaire) was used to evaluate the resting-state functional connectivity in 77 cognitively unimpaired participants aged 50 years and over with high and low CR, and matched brain global atrophy levels. The connectivity of networks linked to attentional (Dorsal Attention Network -DAN-) and executive (Frontal-Parietal Control Network -FPCN-) processes were evaluated by the combination of Independent Component Analysis and seed-based approaches, since these networks have been proposed as candidates to underlie the protective effect of CR in the aging context. Participants with high CR showed an increase of the connectivity in the FPCN and a decrease in the DAN with respect to the low CR group, correlating with neuropsychological scores and supporting that high CR is related to a better neurocognitive preservation during aging This study was supported by grants from the Spanish Government, Ministerio de Ciencia e Innovación (PSI2017-89389-C2-R; PID2020-114521RB-C21/C22); the Galician Government (Xunta de Galicia), Axudas para a Consolidación e Estruturación de Unidades de Investigación Competitivas do Sistema Universitario de Galicia: GRC (GI-1807-USC); Ref: ED431-2017/27; ED431C-2021/04; all with ERDF/FEDER fund SI

Introduction: This study aimed to evaluate, in adults with mild cognitive impairment (MCI), the brain atrophy that may distinguish between three AT(N) biomarker-based profiles, and to determine its clinical value. Methods: Structural MRI (sMRI) was employed to evaluate the volume and cortical thickness differences in MCI patients with different AT(N) profiles, namely, A−T−(N)−: normal AD biomarkers; A+T−(N)−: AD pathologic change; and A+T+(N)+: prodromal AD. Sensitivity and specificity of these changes were also estimated. Results: An initial atrophy in medial temporal lobe (MTL) areas was found in the A+T−(N)− and A+T+(N)+ groups, spreading toward the parietal and frontal regions in A+T+(N)+ patients. These structural changes allowed distinguishing AT(N) profiles within the AD continuum; however, the profiles and their pattern of neurodegeneration were unsuccessful to determine the current clinical status. Conclusion: sMRI is useful in the determination of the specific brain structural changes of AT(N) profiles along the AD continuum, allowing differentiation between MCI adults with or without pathological AD biomarkers This study was supported by grants from the Spanish Government, Ministerio de Ciencia e Innovación (PSI2017- 89389-C2-R and PID2020-114521RB-C21/C22); the Galician Government, Axudas para a Consolidación e Estruturación de Unidades de Investigación Competitivas do Sistema Universitario de Galicia: GRC (GI-1807- USC); Refs: ED431-2017/27 and ED431C-2021/04; all with ERDF/FEDER funds SI

Being language a paradigm of structural and functional asymmetry in cognitive processing, the left Inferior Frontal Gyrus has been consistently related to speech production. In fact, it has been considered a key node in cortical networks responsible for different components of naming. However, isolating these components (e.g., lexical, syntactic, and phonological retrieval) in neuroimaging studies is difficult due to the use of different baselines and tasks. In the present study, functional activation and connectivity of the left inferior frontal gyrus was explored using functional magnetic resonance imaging. Participants performed a covert naming task (pressing a button based on a phonological characteristic). Two conditions were compared: drawings of objects and single letters (baseline condition). Differences in activation and functional connectivity were obtained for objects and letters in different areas of the left Inferior Frontal Gyrus. The pars triangularis was involved in the retrieval of lexical-phonological information, showing a pattern of connectivity with temporal areas in the search for the name of objects and with perisylvanian areas for letters. Selection of phonological information seems to involve the pars opercularis both to letters and objects but recruiting supramarginal and superior temporal areas to letters, probably related to orthographicphonological conversion. The results support the notion of the left Inferior Frontal Gyrus as a buffer forwarding neural information across cortical networks responsible for different components of speech production This research was funded by the Spanish Ministerio de Economía y Competitividad (Grant number: PSI2013 43594-R), Consellería de Cultura, Educación e Ordenación Universitaria, Xunta de Galicia (Grant number: ED431C-2021/04, from the EDRF/FEDER) and by a post-doctoral fellowship from Consellería de Cultura, Educación e Ordenación Universitaria, Xunta de Galicia (Grant number: ED481B2016/078-0). The funding sources were not involved in any aspect of the research or the submission of this study SI

In the present study we used the event-related brain potentials (ERP) technique and eLORETA (exact low-resolution electromagnetic tomography) method in order to characterize and compare the performance and the spatiotemporal pattern of the brain electrical activity related to the immediate episodic retrieval of information (words) that is being learned relative to delayed episodic retrieval twenty-minutes later. For this purpose, 16 young participants carried out an old/new word recognition task with source memory (word colour). The task included an immediate memory phase (with three study-test blocks) followed (20 min later) by a delayed memory phase with one test block. The behavioural data showed progressive learning and consolidation of the information (old words) during the immediate memory phase. The ERP data to correctly identified old words for which the colour was subsequently recollected (H/H) compared to the correctly rejected new words (CR) showed: (1) a significant more positive-going potential in the 500–675 ms post-stimulus interval (parietal old/new effect, related to recollection), and (2) a more negative-going potential in the 950–1850 ms interval (LPN effect, related to retrieval and post-retrieval processes). The eLORETA data also revealed that the successful recognition of old words (and probably retrieval of their colour) was accompanied by activation of (1) left medial temporal (parahippocampal gyrus) and parietal regions involved in the recollection in both memory phases, and (2) prefrontal regions and the superior temporal gyrus (in the immediate and delayed memory phases respectively) involved in monitoring, evaluating and maintaining the retrieval products. These findings indicate that episodic memory retrieval depends on a network involving medial temporal lobe and frontal, parietal and temporal neocortical structures. That network was involved in immediate and delayed memory retrieval and during the course of memory consolidation, with greater activation of some nodes (mobilization of more processing resources) for the delayed respect to the immediate retrieval condition This study was supported by grants from the Spanish Government, Ministerio de Ciencia e Innovación (PSI2014-55316-C3-3-R; PSI2017-89389-C2-2-R), with FEDER Funds; the Galician Government, Consellería de Cultura, Educación e Ordenación Universitaria, Axudas para a Consolidación e Estruturación de Unidades de Investigación Competitivas do Sistema Universitario de Galicia: GRC (GI-1807-USC); Ref: ED431-2017/27, with FEDER funds SI

The present fMRI study aimed to characterize the performance and the brain activity changes related to episodic memory retrieval in adults with single domain aMCI (sdaMCI), relative to cognitively unimpaired adults. Participants performed an old/new recognition memory task with words while BOLD signal was acquired. The sdaMCI group showed lower hits (correct recognition of old words), lower ability to discriminate old and new words, higher errors and longer reaction times for hits. This group also displayed brain hypoactivation in left precuneus and the left midcingulate cortex during the successful recognition of old words. These changes in brain activity suggest the presence of neural dysregulations in brain regions involved during successful episodic memory retrieval. Moreover, hypoactivation in these brain areas discriminated both groups with moderate sensitivity and specificity values, suggesting that it might constitute a potential neurocognitive biomarker of sdaMCI This study was supported by grants from the Spanish Government, Ministerio de Economía y Competitividad (PSI2014–55316-C3–3-R; PSI2017–89389-C2–2-R; PID2020–114521RB-C21/C22); and the Galician Government, Axudas para a Consolidación e Estruturación de Unidades de Investigación Competitivas do Sistema Universitario de Galicia: GRC (GI-1807-USC. Ref: ED431–2017/27; ED431C-2021/04. All with ERDF/FEDER funds SI

Several studies reported that healthy elderly with subjective memory complaints (SMC) evolve to Alzheimer’s disease (AD) more frequently than elderly without subjective memory decline. In the present study, we investigated event-related potentials (ERPs) associated to executive control processes taking place during the performance of a Simon task with two irrelevant dimensions (stimulus position and direction pointed by an arrow) in healthy elderly divided in low and high SMC (LSMC, HSMC) groups. P300 was studied as a correlate of working memory. Medial frontal negativity (MFN) was studied as a correlate of conflict monitoring. Whereas the LSMC group showed interference from the stimulus position, participants with HSMC showed interference from both irrelevant dimensions. P300 latency was longer and P300 amplitude was lower when the stimulus position was incompatible with the required response but differences between both groups were not observed. MFN was not modulated in the LSMC group; however, the HSMC group showed larger MFN when the stimulus position and/or the direction pointed by the arrow were incompatible with the required response. These results suggest that participants with HSMC deployed greater conflict monitoring activity to maintain the performance when the target stimulus contained conflictive spatial information This study was financially supported by funds from the Spanish Government: Ministerio de Economía y Competitividad (PSI2014-55316-C3-3-R; PSI2017-89389-C2-2-R), with FEDER Funds; the Galician Government: Consellería de Cultura, Educación e Ordenación Universitaria; Axudas para a Consolidación e Estruturación de Unidades de Investigación Competitivas do Sistema Universitario de Galicia: GRC (GI-1807-USC); Ref: ED431-2017/27, with FEDER funds; Juan de la Cierva-Incorporación postdoctoral grants SI

Early neuroimaging and electrophysiological studies suggested that motor imagery recruited a different network than motor execution. However, several studies have provided evidence for the involvement of the same circuits in motor imagery tasks, in the absence of overt responses. The present study aimed to test whether imagined performance of a stop-signal task produces a similar pattern of motor-related EEG activity than that observed during real performance. To this end, mu and beta event-related desynchronization (ERD) and the Lateralized Readiness Potential (LRP) were analyzed. The study also aimed to clarify the functional significance of the Stop-N2 and Stop-P3 event-related potential (ERPs) components, which were also obtained during both real and imagined performance. The results showed a common pattern of brain electrical activity, and with a similar time course, during covert performance and overt execution of the stop-signal task: presence of LRP and Stop-P3 in the imagined condition and identical LRP onset, and similar mu and beta ERD temporal windows for both conditions. These findings suggest that a similar inhibitory network may be activated during both overt and covert execution of the task. Therefore, motor imagery may be useful to improve inhibitory skills and to develop new communicating systems for Brain-Computer Interface (BCI) devices based on inhibitory signals This research was funded by Spanish Ministerio de Economía y Competitividad (Reference PSI2013-43594-R). AJG-V was supported by a research grant from the Fundación Ramón Dominguez. The authors would like to thank Fermín Pintos for his support developing a script for extracting the behavioral data SI

Event-related potentials (ERPs) were recorded from 84 adults (51 to 87 years old) with the aim of exploring the effects of aging (middle-aged and older groups) and cognitive status (healthy or with amnestic mild cognitive impairment, aMCI) on the neural functioning associated with stimulus and response processing in a Stroop color-word task. An interference (or Stroop) effect was observed in the Reaction Time (RT), and the RT and number of errors results were consistent with the age-related decline in performance. Cognitive status did not affect the behavioral performance of the task, but age and cognitive status affected several ERP parameters. Aging was associated with a) slowing of the neural processing of the stimuli (P150, N2, and P3b latencies were longer), b) greater activation of the motor cortex for response preparation (LRP-R amplitude was larger), and c) use of more neural resources for cognitive control of stimuli (N2 amplitude was larger to the congruent and incongruent stimuli than to the colored X-strings, in the older group). Independent of age, aMCI dedicated more neural resources to processing the irrelevant dimension of the stimulus (they showed a greater difference than the control participants between the P3b amplitude to the colored X-strings and to the congruent/incongruent stimuli) and showed a deficit in the selection and preparation of the motor response (with smaller LRP-S and LRP-R amplitudes). Furthermore, the middle-aged aMCI participants evaluated and classified both congruent and incongruent stimuli more slowly (they showed longer P3b latencies) relative to middle-aged controls.