Dissociation between Private and Social Counterfactual Value Signals Following Ventromedial Prefrontal Cortex Damage

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Stuck in the here and now: Construction of fictitious and future experiences following ventromedial prefrontal damage

There is increasing interest in uncovering the cognitive and neural bases of episodic future thinking (EFT), the ability to imagine events relevant to one's own future. Recent functional neuroimaging evidence shows that the ventromedial prefrontal cortex (vmPFC) is engaged during EFT. However, vmPFC is also activated during imagination of fictitious, atemporal experiences. Therefore, its role in EFT is currently unclear. To test (1) whether vmPFC is critical for EFT, and (2) whether it supports EFT specifically, or, rather, construction of any complex experience, patients with focal lesions to vmPFC (vmPFC patients), control patients with lesions not involving vmPFC, and healthy controls were asked to imagine personal future experiences and fictitious experiences. Compared to the control groups, vmPFC patients were impaired at imagining both future and fictitious experiences, indicating a general deficit in constructing novel experiences. Unlike the control groups, however, vmPFC patients had more difficulties in imagining future compared to fictitious experiences. Exploratory correlation analyses showed that general construction deficits correlated with lesion volume in BA 11, whereas specific EFT deficits correlated with lesion volume in BA 32 and BA 10. Together, these findings indicate that vmPFC is crucial for EFT. We propose, however, that different vmPFC subregions may support different component processes of EFT: the most ventral part, BA 11, may underlie core constructive processes needed to imagine any complex experience (e.g., scene construction), whereas BA 10 and BA 32 may mediate simulation of those specific experiences that likely await us in the future

Facilitazioni paradossali in compiti di ricerca visiva in pazienti con lesione parietale destra.

Introduzione. In compiti di ricerca visiva i processi top-down coinvolti nel riconoscimento della forma dell’oggetto possono interferire nella elaborazione bottom-up degli attributi elementari che compongono l’oggetto. Precedenti studi r-TMS hanno documentato che la performance in tali compiti può essere facilitata dopo inibizione selettiva della corteccia parietale destra. L’ipotesi alla base del presente studio è che pazienti con lesione focale parietale destra potrebbero non risentire dell’effetto interferente esercitato dal riconoscimento della forma dell’oggetto in compiti di ricerca visiva di singole caratteristiche. Metodo. Hanno partecipato allo studio sette pazienti (2 femmine e 5 maschi) destrimani con lesione parietale destra (età media: 50 ± 14 anni; scolarità media: 12 ± 4 anni) e tredici soggetti sani (2 femmine e 11 maschi) appaiati ai pazienti per età e scolarità. Sono stati somministrati due compiti di ricerca visiva: un compito (A) caratterizzato dalla presenza di interferenza tra il livello dell’oggetto e degli attributi elementari e l’altro (B) privo di tale interferenza. I tempi di reazione sono stati analizzati calcolando un’indice di asimmetria tra i due compiti (TR(A)-TR(B)/TR(A)+TR(B)) e confrontando il gruppo dei pazienti e il gruppo di controllo mediante ttest a due code. Risultati. I pazienti presentavano un’indice di asimmetria tra i due compiti significativamente ridotto rispetto ai soggetti di controllo (p = 0.003) suggerendo pertanto che non risentono dell'effetto di interferenza che contraddistingue il compito A. Conclusioni. La corteccia parietale destra gioca un ruolo nel binding e nei processi di attenzione spaziale che sono alla base dei compiti di ricerca visiva

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Episodic future thinking and future-based decision-making in a case of retrograde amnesia

We investigated episodic future thinking (EFT) and future-based cognition and decision-making in patient SG, who developed a dense retrograde amnesia following hypoxia due to a cardiac arrest. Despite intact general cognitive and executive functioning, SG was unable to remember events from his entire lifetime. He had, however, relatively spared anterograde memory and general semantic knowledge. Voxel-based morphometry detected a reduction of gray matter in the thalamus, cerebellum and fusiform gyrus bilaterally, and, at a reduced threshold, in several regions of the autobiographical memory network, including the hippocampi. We show that SG is unable to imagine personal future events, but can imagine fictitious events not self-relevant and not located in subjective time. Despite severely impaired EFT, SG shows normal attitudes towards the future time, and normal delay discounting rates. These findings suggest that retrieval of autobiographical information from long-term memory is necessary for EFT. However, relatively spared anterograde memory and general semantic knowledge may be sufficient to allow construction of fictitious experiences. As well, EFT is not necessary to drive future-oriented cognition and choice. These findings highlight the relation between autobiographical memory and EFT, and the fractionation of human temporal consciousness. Moreover, they contribute to our understanding of retrograde amnesia as an impairment of memory as well as future thinking

Education protects against cognitive changes associated with multiple sclerosis

Purpose: Although neuropsychological impairments are common in Multiple Sclerosis (MS), the manifestation of cognitive deficits may vary greatly across MS patients. Here, we explored the influence of cognitive reserve proxy indices (education and occupation) and perceived fatigue on cognitive performance. Methods: Fifty relapsing-remitting MS patients were evaluated. Cognitive performance was measured using the Paced Auditory Serial Addition Test (PASAT), in which information processing speed can be manipulated by varying the presentation speed of stimuli. Results: MS patients with low education performed worse than healthy controls at faster PASAT speeds. By contrast, no difference was observed between MS patients with high education and matched healthy controls, regardless of PASAT speed. Moreover, we found that neither occupational attainment nor perceived fatigue has an influence on MS patients' cognitive performance. Conclusion: These findings provide evidence that higher education could be protective against MS-associated cognitive deficits and that high speed PASAT versions are more suitable for identifying compensatory capacities compared to low speed PASAT versions. \ua9 2013 - IOS Press and the authors. All rights reserved

Education protects against cognitive changes associated with multiple sclerosis

Purpose: Although neuropsychological impairments are common in Multiple Sclerosis (MS), the manifestation of cognitive deficits may vary greatly across MS patients. Here, we explored the influence of cognitive reserve proxy indices (education and occupation) and perceived fatigue on cognitive performance. Methods: Fifty relapsing-remitting MS patients were evaluated. Cognitive performance was measured using the Paced Auditory Serial Addition Test (PASAT), in which information processing speed can be manipulated by varying the presentation speed of stimuli. Results: MS patients with low education performed worse than healthy controls at faster PASAT speeds. By contrast, no difference was observed between MS patients with high education and matched healthy controls, regardless of PASAT speed. Moreover, we found that neither occupational attainment nor perceived fatigue has an influence on MS patients' cognitive performance. Conclusion: These findings provide evidence that higher education could be protective against MS-associated cognitive deficits and that high speed PASAT versions are more suitable for identifying compensatory capacities compared to low speed PASAT versions

Dissociation between private and social counterfactual value signals following ventromedial prefrontal cortex damage

Individuals learn by comparing the outcome of chosen and unchosen actions. A negative counterfactual value signal is generated when this comparison is unfavorable. This can happen in private as well as in social settings—where the foregone outcome results from the choice of another person. We hypothesized that, despite sharing similar features such as supporting learning, these two counterfactual signals might implicate distinct brain networks. We conducted a neuropsychological study on the role of private and social counterfactual value signals in risky decision-making. Patients with lesions in the ventromedial prefrontal cortex (vmPFC), lesion controls, and healthy controls repeatedly chose between lotteries. In private trials, participants could observe the out-out-comes of their choices and the outcomes of the unselected lotteries. In social trials, participants could also see the other player’s choices and outcome. At the time of outcome, vmPFC patients were insensitive to private counterfactual value signals, whereas their responses to social comparison were similar to those of control participants.Atthetimeofchoice, intact vmPFC was necessary to integrate counterfactual signals in decisions, although amelioration was observed during the course of the task, possibly driven by social trials. We conclude that if the vmPFC is critical in processing private counterfactual signals and in integrating those signals in decision-making, then distinct brain areas might support the processing comes of social counterfactual signals