Repetitive Transcranial Magnetic Stimulation of Dorsolateral Prefrontal Cortex Affects Performance of the Wisconsin Card Sorting Task during Provision of Feedback

Early functional neuroimaging studies of tasks evaluating executive processes, such as the Wisconsin card sorting task (WCST), only assessed trials in blocks that may contain a large amount of different cognitive processes. More recently, we showed using event-related fMRI that the dorsolateral prefrontal cortex (DL-PFC) significantly increased activity during feedback but not matching periods of the WCST, consistent with its proposed role in the monitoring of information in working memory. Repetitive transcranial magnetic stimulation (rTMS) is a method that allows to disrupt processing within a given cortical region and to affect task performance for which this region is significantly solicited. Here we applied rTMS to test the hypothesis that the DL-PFC stimulation influences monitoring of working memory without interfering with other executive functions. We applied rTMS to the right DL-PFC and the vertex (control site) in different time points of the WCST. When rTMS was applied to the DL-PFC specifically during the period when subjects were receiving feedback regarding their previous response, WCST performance deteriorated, while rTMS did not affect performance during matching either when maintaining set or during set-shifting. This selective impairment of the DL-PFC is consistent with its proposed role in monitoring of events in working memory

Effets de la stimulation magnétique transcrânienne dans la maladie de Parkinson avec déficits cognitifs légers

Beaucoup de patients atteints de la maladie de Parkinson (MP) peuvent souffrir de troubles cognitifs dès les étapes initiales de la maladie et jusqu’à 80% d’entre eux vont développer une démence. Des altérations fonctionnelles au niveau du cortex préfrontal dorsolatéral (CPFDL), possiblement en relation avec le noyau caudé, seraient à l’origine de certains de ces déficits cognitifs. Des résultats antérieurs de notre groupe ont montré une augmentation de l’activité et de la connectivité dans la boucle cortico-striatale cognitive suite à la stimulation magnétique transcrânienne (SMT) utilisant des paramètres « theta burst » intermittent (iTBS) sur le CPFDL gauche. Pour cette étude, 24 patients atteints de la MP avec des troubles cognitifs ont été séparées en 2 groupes : le groupe iTBS active (N=15) et le groupe sham (stimulation simulée, N=9). Une batterie neuropsychologique détaillée évaluant cinq domaines cognitifs (attention, fonctions exécutives, langage, mémoire et habiletés visuo-spatiales) a été administrée lors des jours 1, 8, 17 et 37. Le protocole iTBS a été appliqué sur le CPFDL gauche durant les jours 2, 4 et 7. Les scores z ont été calculés pour chaque domaine cognitif et pour la cognition globale. Les résultats ont montré une augmentation significative de la cognition globale jusqu’à 10 jours suivant l’iTBS active, particulièrement au niveau de l’attention, des fonctions exécutives et des habiletés visuo-spatiales. Cet effet sur la cognition globale n’est pas répliqué dans le groupe sham. Ces résultats suggèrent donc que l’iTBS peut moduler la performance cognitive chez les patients atteints de MP avec des déficits cognitifs.Cognitive impairment affects many patients with Parkinson’s disease (PD) in the early phase of the disease and up to 80% of them will eventually develop dementia. Many studies suggests that these cognitive deficits are mediated by functional alterations in the dorsolateral prefrontal cortex (DLPFC), possibly in relation with the caudate nucleus. Previous results from our group showed an increase in activity and connectivity within the cognitive cortico-striatal loop when applying transcranial magnetic stimulation (TMS) using intermittent « theta burst » (iTBS) parameters over left DLPFC. For this study, 24 idiopathic PD patients with cognitive impairment were recruited and divided into two groups : active iTBS group (N=15) and sham group (simulated stimulation, N=9). Detailed neuropsychological assessment of five cognitive domains (attention, executive functions, language, memory, visuospatial abilities) was performed on day 1, 8, 17 and 37. iTBS protocol over left DLPFC was performed on day 2, 4 and 7. Z scores were calculated for each domain and for the overall cognition performance. Our results showed a significant increase in overall cognition up to 10 days after receiving active iTBS, improving mainly attention, executive functions and visuospatial abilities. This effect was not replicated in the sham group. Therefore, our results suggest that iTBS can modulate cognitive performance in PD patients with cognitive deficits

Inhibitory Control Training

Inhibitory control is a critical neurocognitive skill for navigating cognitive, social, and emotional challenges. It rapidly increases during the preschool period and is important for early cognitive development, as it is a crucial component of executive functioning, self-regulation, and impulsivity. Inhibitory control training (ICT) is a novel intervention in which participants learn to associate appetitive cues with inhibition of behavior. It is being considered a promising approach in the treatment of psychopathology and appetitive behaviors. This book aims to bring together knowledge on the topic, considering research, clinic, and forensic field of intervention. Indeed, this book can be considered an excellent synopsis of perspectives, methods, empirical evidence, and international references

Premotor and prefrontal contributions to modulating upper limb somatosensory input into non-primary motor areas

Upper limb motor control requires the use and integration of afferent somatosensory input from peripheral receptors to help plan and prepare movements. Cortical surface electroencephalography can be used to measure the earliest relay and processing of mixed somatosensory input in primary (SI) and secondary somatosensory (SII) cortices using parietal somatosensory evoked potentials (SEPs) that occur 20 to 100 milliseconds (ms) after median nerve stimulation. Moreover, somatosensory input into non-primary motor areas, such as premotor cortex (PMC) and supplementary motor area (SMA), can be measured by frontal N30 and N60 SEPs. Therefore, frontal N30 and N60 SEPs may provide an important neurophysiological link between somatosensory processing and upper limb motor control. Both PMC and SMA have intracortical connections with primary motor cortex (M1) and prefrontal cortex (PFC) as well as intercortical connections with their contralateral representations. However, it is not fully understood how somatosensory input in non-primary motor areas, represented by frontal SEPs, are modulated in the cortex by contralateral PMC and ipsilateral PFC. A modulatory role of contralateral M1 but not contralateral premotor areas on somatosensory input into non-primary motor areas has been established through contralateral movement paradigms. Furthermore, a modulatory role of the ipsilateral PFC on somatosensory input into non-primary motor areas has been identified through prefrontal lesion patients but it is unclear how PFC functionally modulates this somatosensory input during movement. Thus, the current thesis aimed to evaluate the contributions of the ipsilateral PFC as well as contralateral PMC on somatosensory processing in non-primary motor areas as well as SI/SII. SEP modulations were examined using experimental manipulations of top-down attention and cued contralateral movements to evaluate PFC and PMC contributions, respectively. In addition, continuous theta burst stimulation, a specific type of inhibitory non-invasive transcranial magnetic stimulation technique, was applied over PMC and PFC to evaluate their specific contributions to modulating somatosensory input into non-primary motor areas and SI/SII during a cued movement task. Understanding frontal SEP modulations and their association with upper limb motor control will have important applications for understanding dysfunctional upper limb motor control in various neurological disorders such as Parkinson’s disease (PD) that are known to have irregular frontal SEPs. The main findings from Chapters 2 and 3 revealed that frontal N30 and N60 SEPs were decreased during early response selection and increased during the late stages of preparing finger sequences to attended somatosensory input. In contrast, SI/SII input represented by parietal P50 and P100 SEPs were increased with attention. The main results of Chapter 4 showed that N30 and N60 SEPs were decreased and increased after transiently decreasing excitability in left PMC and right PFC, respectively. Collectively, the results of this thesis revealed temporally-specific modulations of somatosensory input into non-primary motor areas during contralateral upper limb movements that are a result of changes in activity in a network that includes the right PFC and left PMC

Cognitive ageing and the prefrontal cortex

The prefrontal cortex (PFC) is a site which has been shown to be particularly susceptible to the ageing process. However, the PFC itself is a heterogeneous area, and recent studies have suggested that it can be split into anatomically and functionally distinct subregions. The present study investigated the differential effect of cognitive ageing on these subregions and their associated functions. Firstly, the present study investigated various psychological tasks for their regional specificity and suitability for use in ageing research. Tasks thought to preferentially recruit dorsolateral PFC regions included a Self-Ordered Pointing task and the Digit Span Backwards task. Tasks thought to preferentially recruit orbital PFC regions included a Reversal Learning task and the Faux Pas task. Tasks thought to preferentially recruit medial PFC regions included a Simon task and the AX-Continuous Performance task. The performance of younger and older individuals was then compared on the selected tasks. Age-related differences were found on both dorsolateral and orbital PFC tasks, but not on medial PFC tasks. Particular declines were observed in working memory and associative learning abilities, whilst no evidence of dysfunction was found on performance monitoring and social-emotional skills. The results support a region-specific theory of cognitive ageing whereby both dorsolateral and orbital PFC regions are most susceptible to decline, with the medial PFC relatively preserved