The thalamus and working memory

Basal ganglia lateralization in different types of reward

Reward processing is a fundamental human activity. The basal ganglia are recognized for their role in reward processes; however, specific roles of the different nuclei (e.g., nucleus accumbens, caudate, putamen and globus pallidus) remain unclear. Using quantitative meta-analyses we assessed whole-brain and basal ganglia specific contributions to money, erotic, and food reward processing. We analyzed data from 190 fMRI studies which reported stereotaxic coordinates of whole-brain, within-group results from healthy adult participants. Results showed concordance in overlapping and distinct cortical and sub-cortical brain regions as a function of reward type. Common to all reward types was concordance in basal ganglia nuclei, with distinct differences in hemispheric dominance and spatial extent in response to the different reward types. Food reward processing favored the right hemisphere; erotic rewards favored the right lateral globus pallidus and left caudate body. Money rewards engaged the basal ganglia bilaterally including its most anterior part, nucleus accumbens. We conclude by proposing a model of common reward processing in the basal ganglia and separate models for money, erotic, and food rewards.

[Formula: see text] Executive function following pediatric stroke. A systematic review

OBJECTIVE

Pediatric strokes are rare events that can lead to neuropsychological impairment or disability. While motor deficits are relatively easy to identify and investigate, cognitive outcomes after stroke are more complex to define. Many studies have focused on global cognitive outcomes, while only a few recent studies have focused on specific cognitive processes. The aims of the present review were to provide an overview of the effects of pediatric strokes on executive function and to investigate the relations between executive functioning and clinical factors.

METHOD

Studies concerning executive functioning after pediatric stroke were identified using PsycInfo, PsycArticles and PubMed. A total of 142 studies were identified, and 22 met the inclusion criteria.

RESULTS

The review of the 22 studies included clearly indicates that childhood and perinatal strokes can affect executive function, and in particular inhibition. In contrast, the results concerning clinical factors related to EF outcomes are inconsistent.

DISCUSSION

Our results highlight the importance to assess EF following pediatric stroke. Early identification of difficulties in EF is crucial to provide adequate training to the children and to prevent the development of other correlated difficulties, such as behavioral problems or learning difficulties. Methodological issues regarding the heterogeneity of samples and measurement difficulties limit the conclusions that can be made about the clinical predictors of the outcomes. Studies are needed to better understand this aspect and to develop adequate EF interventions for children following stroke.

Predictors of Cognitive and Academic Outcome following Childhood Subcortical Stroke

Childhood arterial ischemic stroke often involves basal ganglia and thalamus but little is known about neuropsychological outcomes in this group. We examined intellectual ability, academics, attention, executive function, and psychological diagnoses in children and adolescents (6-20 years of age) with childhood stroke involving the basal ganglia (n = 32) or thalamus (n = 12). Intellectual ability was age-appropriate but working memory was significantly lower than expected. Compared to the normative mean, the stroke group exhibited significantly weaker performance in reading comprehension, math fluency, attention, and greater challenges with executive function. Children with basal ganglia stroke had weaker working memory and were more likely to receive diagnoses of Attention Deficit Hyperactivity Disorder and Anxiety Disorder than those with thalamic stroke. Lesion size was most important in predicting working memory ability, whereas age at stroke and age at test were important in predicting academic ability.

EEG Spectral Generators Involved in Motor Imagery: A swLORETA Study

In order to characterize the neural generators of the brain oscillations related to motor imagery (MI), we investigated the cortical, subcortical, and cerebellar localizations of their respective electroencephalogram (EEG) spectral power and phase locking modulations. The MI task consisted in throwing a ball with the dominant upper limb while in a standing posture, within an ecological virtual reality (VR) environment (tennis court). The MI was triggered by the visual cues common to the control condition, during which the participant remained mentally passive. As previously developed, our paradigm considers the confounding problem that the reference condition allows two complementary analyses: one which uses the baseline before the occurrence of the visual cues in the MI and control resting conditions respectively; and the other which compares the analog periods between the MI and the control resting-state conditions. We demonstrate that MI activates specific, complex brain networks for the power and phase modulations of the EEG oscillations. An early (225 ms) delta phase-locking related to MI was generated in the thalamus and cerebellum and was followed (480 ms) by phase-locking in theta and alpha oscillations, generated in specific cortical areas and the cerebellum. Phase-locking preceded the power modulations (mainly alpha-beta ERD), whose cortical generators were situated in the frontal BA45, BA11, BA10, central BA6, lateral BA13, and posterior cortex BA2. Cerebellar-thalamic involvement through phase-locking is discussed as an underlying mechanism for recruiting at later stages the cortical areas involved in a cognitive role during MI.

Motor-Language Coupling in Huntington's Disease Families

Traditionally, Huntington’s disease (HD) has been known as a movement disorder, characterized by motor, psychiatric, and cognitive impairments. Recent studies have shown that motor and action–language processes are neurally associated. The cognitive mechanisms underlying this interaction have been investigated through the action compatibility effect (ACE) paradigm, which induces a contextual coupling of ongoing motor actions and verbal processing. The present study is the first to use the ACE paradigm to evaluate action–word processing in HD patients (HDP) and their families. Specifically, we tested three groups: HDP, healthy first-degree relatives (HDR), and non-relative healthy controls. The results showed that ACE was abolished in HDP as well as HDR, but not in controls. Furthermore, we found that the processing deficits were primarily linguistic, given that they did not correlate executive function measurements. Our overall results underscore the role of cortico-basal ganglia circuits in action–word processing and indicate that the ACE task is a sensitive and robust early biomarker of HD and familial vulnerability.

Cognitive control of movement via the cerebellar-recipient thalamus

The cognitive control of behavior was long considered to be centralized in cerebral cortex. More recently, subcortical structures such as cerebellum and basal ganglia have been implicated in cognitive functions as well. The fact that subcortico-cortical circuits for the control of movement involve the thalamus prompts the notion that activity in movement-related thalamus may also reflect elements of cognitive behavior. Yet this hypothesis has rarely been investigated. Using the pathways linking cerebellum to cerebral cortex via the thalamus as a template, we review evidence that the motor thalamus, together with movement-related central thalamus have the requisite connectivity and activity to mediate cognitive aspects of movement control.

A balancing act of the brain: activations and deactivations driven by cognitive load

The majority of neuroimaging studies focus on brain activity during performance of cognitive tasks; however, some studies focus on brain areas that activate in the absence of a task. Despite the surge of research comparing these contrasted areas of brain function, their interrelation is not well understood. We systematically manipulated cognitive load in a working memory task to examine concurrently the relation between activity elicited by the task versus activity during control conditions. We presented adults with six levels of task demand, and compared those with three conditions without a task. Using whole-brain analysis, we found positive linear relations between cortical activity and task difficulty in areas including middle frontal gyrus and dorsal cingulate; negative linear relations were found in medial frontal gyrus and posterior cingulate. These findings demonstrated balancing of activation patterns between two mental processes, which were both modulated by task difficulty. Frontal areas followed a graded pattern more closely than other regions. These data also showed that working memory has limited capacity in adults: an upper bound of seven items and a lower bound of four items. Overall, working memory and default-mode processes, when studied concurrently, reveal mutually competing activation patterns.