Neuromodulation of Spatial Associations: Evidence from Choice Reaction Tasks During Transcranial Direct Current Stimulation

Various portions of human behavior and cognition are influenced by covert implicit processes without being necessarily available to intentional planning. Implicit cognitive biases can be measured in behavioral tasks yielding SNARC effects for spatial associations of numerical and non-numerical sequences, or yielding the implicit association test effect for associations between insect-flower and negative-positive categories. By using concurrent neuromodulation with transcranial direct current stimulation (tDCS), subthreshold activity patterns in prefrontal cortical regions can be experimentally manipulated to reduce implicit processing. Thus, the application of tDCS can test neurocognitive hypotheses on a unique neurocognitive origin of implicit cognitive biases in different spatial-numerical and non-numerical domains. However, the effects of tDCS are not only determined by superimposed electric fields, but also by task characteristics. To outline the possibilities of task-specific targeting of tDCS, task characteristics and instructions can be varied systematically when combined with neuromodulation. In the present thesis, implicit cognitive processes are assessed in different paradigms concurrent to left-hemispheric prefrontal tDCS to investigate a verbal processing hypothesis for implicit associations in general. In psychological experiments, simple choice reaction tasks measure implicit SNARC and SNARC-like effects as relative left-hand vs. right-hand latency advantages for responding to smaller number or ordinal sequence targets. However, different combinations of polarity-dependent tDCS with stimuli and task procedures also reveal domain-specific involvements and dissociations. Discounting previous unified theories on the SNARC effect, polarity-specific neuromodulation effects dissociate numbers and weekday or month ordinal sequences. By considering also previous results and patient studies, I present a hybrid and augmented working memory account and elaborate the linguistic markedness correspondence principle as one critical verbal mechanism among competing covert coding mechanisms. Finally, a general stimulation rationale based on verbal working memory is tested in separate experiments extending also to non-spatial implicit association test effects. Regarding cognitive tDCS effects, the present studies show polarity asymmetry and task-induced activity dependence of state-dependent neuromodulation. At large, distinct combinations of the identical tDCS electrode configuration with different tasks influences behavioral outcomes tremendously, which will allow for improved task- and domain-specific targeting

Tes and its Effects on Cognitive FUnctions: Feasibility and Limitations for a Broader Clinical Application

Trascranial electrical stimulation (tES) is a neuromodulation technique which applies a mild current to modulate a wide variety of cognitive functions. It was shown that depending on the protocol applied, tES is effective in enhancing or interfering with cortical excitation, even if further research is needed in order to better understand its effects. In our studies, we focused on the online or offline effects of various tES protocols and on disparate tasks, in order to evaluate potential future application on clinical population. To date, few studies investigated offline, transfer effects of tES, both after single or multiple sessions administration. Similarly, evidence assessing tES offline and long-term effects on cortical excitability is still lacking. This doctoral thesis contributed to shed light on different aspects concerning tES. Firstly, we demonstrated that cathodal tDCS applied over right inferior frontal gyrus (rIFG) is effective in modulating selectively incongruent trials in a dots comparison task. Moreover, the effect was specific for offline measures, but not online, suggesting possible short-term after-effects of this protocol. Secondly, we showed that bilateral tRNS is more effective than anodal tDCS in inducing after-stimulation changes in attention both on behavioral performance and cortical excitation. Our studies confirmed that the two protocols are differentially effective, consistently with literature showing that different neural mechanisms underlie tDCS and tRNS neural after-effects. Finally, we demonstrated that despite the absence of online effects, coupling bilateral tRNS with cognitive training is effective to induce long-term changes, as assessed by behavioral measures and cortical plasticity investigations. Interestingly, the effects were still present a month after the end of the training. Taken together, our studies contributed to better understand the after-effects of tES and suggests that bilateral tRNS is best suited for clinical applications, even if further research is needed

The Neuroscience of Mathematical Cognition and Learning

The synergistic potential of cognitive neuroscience and education for efficient learning has attracted considerable interest from the general public, teachers, parents, academics and policymakers alike. This review is aimed at providing 1) an accessible and general overview of the research progress made in cognitive neuroscience research in understanding mathematical learning and cognition, and 2) understanding whether there is sufficient evidence to suggest that neuroscience can inform mathematics education at this point. We also highlight outstanding questions with implications for education that remain to be explored in cognitive neuroscience. The field of cognitive neuroscience is growing rapidly. The findings that we are describing in this review should be evaluated critically to guide research communities, governments and funding bodies to optimise resources and address questions that will provide practical directions for short- and long-term impact on the education of future generations

Parameters Characterization and Cognitive-Behavioral Effects of Transcranial Pulsed Current Stimulation

Neuromodulation is being recognized as “technology impacting on the neural interface” And noninvasive brain stimulation (NIBS) is becoming an interesting alternative for this interface. Transcranial pulsed current stimulation (tPCS) is emerging as an option in the field of neuromodulation as a technique that employs weak, pulsed current at different frequency ranges, inducing electrical fields that reach cortical and subcortical structures; however, little is known about its properties and mechanistic effects on electrical brain activity and how it can modulate its oscillatory patterns. Moreover, there is not clear understanding in how tPCS can affect cognition and behavior or its neurophysiological correlates as indexed by autonomic responses. This research looked at the mechanisms behind tPCS in four randomized clinical trials; the main aim of each experiment was to evaluate the effects of tPCS in quantitative electroencephalography (qEEG) and cognitive-behavioral testing by exploring different parameters of stimulation. Based in the findings obtained per experiment, tPCS can be defined as a safe and tolerable technique that modulates the power spectrum of qEEG signals by means of applied randomized frequencies in a pre-defined range, tPCS also facilitates connectivity in the area of influence by the electrical field and this has an impact on optimization of performance by decreasing reaction times (RT) in attention switching task and by facilitating wide-ranging network processing as in the case of arithmetic functioning. This work also delivered an insight about the potential that tPCS has for future clinical applications.The Labuschagne-Foundation Spaulding Neurmodulation Cente

Social cognition and transcranial stimulation of the temporoparietal junction

This study examined behavioural and electrophysiological effects of transcranial stimulation on social cognitive abilities. Positive effects on aspects of emotion processing were observed, which were also related to neurophysiological markers. Stimulation also interacted with autism-relevant trait scores, underlining the relevance of this research to potential clinical applications.<br /

State-Dependent Cortical Network Dynamics

Neuropsychiatric illness represents a major health burden in the United States with a paucity of effective treatment. Many neuropsychiatric illnesses are network disorders, exhibiting aberrant organization of coordinated activity within and between brain areas. Cortical oscillations, arising from the synchronized activity of groups of neurons, are important in mediating both local and long-range communication in the brain and are particularly affected in neuropsychiatric diseases. A promising treatment approach for such network disorders entails ‘correcting’ abnormal oscillatory activity through non-invasive brain stimulation. However, we lack a clear understanding of the functional role of oscillatory activity in both health and disease. Thus, basic science and translational work is needed to elucidate the role of oscillatory activity and other network dynamics in neuronal processing and behavior. Organized activity in the brain occurs at many spatial and temporal scales, ranging from the millisecond duration of individual action potentials to the daily circadian rhythm. The studies comprising this dissertation focused on organization in cortex at the time scale of milliseconds, assessing local field potential and spiking activity, and contribute to understanding (1) the effects of non-invasive brain stimulation on behavioral responses, (2) network dynamics within and across cortical areas during different states, and (3) how oscillatory activity organizes spiking activity locally and long-range during sustained attention. Taken together, this work provides insight into the physiological organization of network dynamics and can provide the basis for future rational design of non-invasive brain stimulation treatments.Doctor of Philosoph

Cognitive Assessment and Rehabilitation of subjects with Traumatic Brain Injury

This thesis regards the study and the development of new cognitive assessment and rehabilitation techniques of subjects with traumatic brain injury (TBI). In particular, this thesis i) provides an overview about the state of art of this new assessment and rehabilitation technologies, ii) suggests new methods for the assessment and rehabilitation and iii) contributes to the explanation of the neurophysiological mechanism that is involved in a rehabilitation treatment. Some chapters provide useful information to contextualize TBI and its outcome; they describe the methods used for its assessment/rehabilitation. The other chapters illustrate a series of experimental studies conducted in healthy subjects and TBI patients that suggest new approaches to assessment and rehabilitation. The new proposed approaches have in common the use of electroencefalografy (EEG). EEG was used in all the experimental studies with a different purpose, such as diagnostic tool, signal to command a BCI-system, outcome measure to evaluate the effects of a treatment, etc. The main achieved results are about: i) the study and the development of a system for the communication with patients with disorders of consciousness. It was possible to identify a paradigm of reliable activation during two imagery task using EEG signal or EEG and NIRS signal; ii) the study of the effects of a neuromodulation technique (tDCS) on EEG pattern. This topic is of great importance and interest. The emerged founding showed that the tDCS can manipulate the cortical network activity and through the research of optimal stimulation parameters, it is possible move the working point of a neural network and bring it in a condition of maximum learning. In this way could be possible improved the performance of a BCI system or to improve the efficacy of a rehabilitation treatment, like neurofeedback

Good and bad at numbers: typical and atypical development of number processing and arithmetic

This thesis elucidates the heterogeneous nature of mathematical skills by examining numerical and arithmetical abilities in typical, atypical and exceptional populations. Moreover, it looks at the benefits of intervention for remediating and improving mathematical skills. First, we establish the nature of the ‘number sense’ and assess its contribution to typical and atypical arithmetical development. We confirmed that representing and manipulating numerosities approximately is fundamentally different from the ability to manipulate them exactly. Yet only the exact manipulation of numbers seems to be crucial for the development of arithmetic. These results lead to a better characterization of mathematical disabilities such as Developmental Dyscalculia and Low Numeracy. In the latter population we also investigated more general cognitive functions demonstrating how inhibition processes of working memory and stimulusmaterial interacted with arithmetical attainment. Furthermore, we examined areas of mathematics that are often difficult to grasp: the representation and processing of rational numbers. Using explicit mapping tasks we demonstrated that well-educated adults, but also typically developing 10 year olds and children with low numeracy have a comprehensive understanding of these types of numbers. We also investigated exceptional maths abilities in a population of children with Autism Spectrum Disorder (ASD) demonstrating that this condition is characterized by outstanding arithmetical skills and sophisticated calculation strategies, which are reflected in a fundamentally different pattern of brain activation. Ultimately we looked at remediation and learning. Targeted behavioural intervention was beneficial for children with low numeracy but not in Developmental Dyscalculia. Finally, we demonstrated that adults’ numerical performance can be enhanced by neural stimulation (tDCS) to dedicated areas of the brain. This work sheds light on the entire spectrum of mathematical skills from atypical to exceptional development and it is extremely relevant for the advancing of the field of mathematical cognition and the prospects of diagnosis, education and intervention

Optimising perceptuo-motor performance and learning with EEG neurofeedback

The neurobiological functions of an organism serve to assist its adaptation to behaviourally challenging environments, which commonly involves the learning and refinement of perceptuo-motor skills. The intensity and time scale at which this occurs is critical towards survival. Previous work has observed that the neurochemical and neuroelectric (EEG) operation of specific functional systems is upregulated during so-called ‘activated’ states of behaviour. Thus it has recently been shown that artificial (i.e. exogenous) stimulation of such systems via pharmacological or electrical means can successfully modulate as well as enhance learning and associated behavioural performance. We hypothesized that neurofeedback, which is implemented through non-invasive volitional control of electrocortical rhythms (EEG), offers an alternate and natural (i.e. endogenous) way to modulate and thereby stimulate analogous systems. Study 1 shows that neurofeedback is a viable and beneficial method for improving the acquisition and performance of perceptuo-motor skills in trainee microsurgeons, when compared to a wait-list control group. With the aid of transcranial magnetic stimulation (TMS), Study 2 demonstrates for the first time that 30 minutes of a single neurofeedback session directly leads to a robust and correlated change in corticomotor plasticity which is usually associated with learning or observed after exogenous stimulation. Lastly, Study 3 investigates the short-term modulation of one session of‘excitatory’ neurofeedback on the subsequent performance of a serial reaction-time task (SRTT), an experimental paradigm widely used as a model for procedural perceptuo-motor learning. In conclusion, this thesis contributes original evidence of direct as well as long-term functional enhancements following EEG neurofeedback, and supports its use as a safe, non-invasive and natural method for improving human perceptuo-motor performance and learning.EThOS - Electronic Theses Online ServiceGBUnited Kingdo