Beta Oscillations in Working Memory, Executive Control of Movement and Thought, and Sensorimotor Function

Beta oscillations (~13 to 30Hz) have been observed during many perceptual, cognitive and motor processes in a plethora of brain recording studies. While the function of beta oscillations (hereafter ‘beta’ for short) is unlikely to be explained by any single monolithic description, we here discuss several convergent findings. In prefrontal cortex, increased beta appears at the end of a trial when working memory information needs to be erased. A similar clear-out function might apply during the stopping of action and the stopping of long-term memory retrieval (stopping thoughts), where increased prefrontal beta is also observed. A different apparent role for beta in prefrontal cortex occurs during the delay period of working memory tasks: it might serve to maintain the current contents and/or to prevent interference from distraction. We confront the challenge of relating these observations to the large literature on beta recorded from sensorimotor cortex. Potentially, the clear-out of working memory in prefrontal cortex has its counterpart in the post-movement clear-out of the motor plan in sensorimotor cortex. However, recent studies support alternative interpretations. In addition, we flag emerging research on different frequencies of beta and the relationship between beta and single neuron spiking. We also discuss where beta might be generated: basal ganglia, cortex, or both. We end by considering the clinical implications for adaptive deep brain stimulation

Single neuron computations of cognition in the human brain

Understanding how information is encoded, processed, and decoded to produce behavior is a fundamental goal of neuroscience. In this dissertation, we aim to expand our understanding of our human decision-making processes at the single-neuronal level. We describe three studies exploring the neural substrate of decision-making in three separate brain regions. First, we describe a method for recording the activity of individual neurons in human subjects. The unique combination of behavioral and neurophysiological data will allow us to better understand the neural substrate of cognitive functions in humans. Second, we explored how decisions are represented in the brain. We recorded single neuronal responses in the human nucleus accumbens while subjects engaged in a financial decision-making task. We found that neurons in the nucleus accumbens predicted upcoming decisions well before the behavior was manifested. In addition, these neurons encoded a positive and negative prediction error signal, signaling the difference between expected and realized outcome. Third, we explored how the brain represents decision conflict and how it adapts to prime future decisions allowing tradeoff between speed and accuracy. We found that individual neurons in the human dorsal anterior cingulate cortex encode the level of decision conflict in a dose-dependent manner. In addition, these neurons encode historical conflict information, priming the neural circuit to future trials of the same or varying conflict levels. Following selective ablation of the dorsal anterior cingulate cortex, we found this signal was selectively abolished. Lastly, we explored how the brain represents decisions under conflict and if these decisions are malleable to external intervention. We found that neurons in the human subthalamic nucleus are selectively activated and encode the upcoming decision during situations of high decision conflict. Based on the physiological findings, we then applied intermittent stimulation through the implanted deep brain stimulation electrode during the same task, to demonstrate a causal interaction between the physiology and behavior. In conclusion, we describe a set of experiments that systematically explore human decision-making processes at the single-neuronal level

Deep Brain Stimulation for Parkinson\u27s Disease: An Investigation of Post-Surgical Self-Regulation and Executive Functioning

Parkinson’s Disease (PD) is a common neurodegenerative disorder that attacks the basal ganglia and contributes to a range of motor, cognitive, and behavioral impairments (e.g., tremor, rigidity, and executive dysfunction). This dysfunction may contribute to self-regulatory impairment across several domains, including cognitive skills, thought processes, and emotion. Deep Brain Stimulation (DBS) is a neurosurgical procedure that allows for direct and reversible manipulation of brain activity in patients with PD. The procedure is growing in popularity and is commonly used as an adjunct or in some instances an alternative to dopaminometic medications. Preliminary studies suggest mild executive dysfunction follows DBS but as the literature is in its early stages, there is a need to examine further the range of executive deficits and self-regulatory impairment observed in PD following DBS. In the present study, twenty-seven PD patients post-DBS completed a brief neuropsychological test battery and provided measures of heart rate variability (HRV). Patients also completed questionnaires regarding their ability to self-regulate emotions and thought patterns. Scores were compared to the patient’s pre-surgical performance as well as to a group of healthy older adults. Results suggest DBS leads to significant declines in executive function (EF) and self-regulation (SR). Patients had significantly worse scores on neuropsychological tests of EF (i.e., phonemic fluency, semantic fluency, and working memory) when compared to their preoperative performance. Similarly, DBS patients had significantly worse scores than controls on measures of EF (i.e., verbal fluency, attention, mental flexibility) and verbal memory. With regard to physiological functioning, lower baseline HRV was linked to worse EF but fewer impulsive-compulsive behaviors in DBS patients. Correlations among measures of theoretically similar constructs (i.e., EF and SR) modest and variable, challenging the idea that SR in different domains depends on a common resource. The results of the current study suggest that PD patients are prone to a variety of self-regulatory deficits, ranging from subtle to severe. They are likely to experience small declines in EF post-DBS that may contribute to these self-regulatory impairments. However, this research suggests that both the quantity and quality of impairment varies, and that the correlates of these deficits may be different between patients. Clinically, it is important for health care professionals working with PD to recognize the presence of self-regulatory deficits and to be aware of the potential obstacles that might arise from such impairments within a patient’s daily life

A subcortical network for implicit visuo-spatial attention:Implications for Parkinson's disease

Recent studies in humans and animal models suggest a primary role of the basal ganglia in the extraction of stimulus-value regularities, then exploited to orient attentional shift and build up sensorimotor memories. The tail of the caudate and the posterior putamen both receive early visual input from the superficial layers of the superior colliculus, thus forming a closed-loop. We portend that the functional value of this circuit is to manage the selection of visual stimuli in a rapid and automatic way, once sensory-motor associations are formed and stored in the posterior striatum. In Parkinson's Disease, the nigrostriatal dopamine depletion starts and tends to be more pronounced in the posterior putamen. Thus, at least some aspect of the visuospatial attention deficits observed since the early stages of the disease could be the behavioral consequences of a cognitive system that has lost the ability to translate high-level processing in stable sensorimotor memories. (C) 2021 The Authors. Published by Elsevier Ltd

Parkinson\u27s Disease and Occupational Therapy: Evidence Based Practice

The therapeutic benefit of occupational therapy with Parkinson\u27s disease has not been studied in great detail. The purpose of this Scholarly Project was to provide extensive and comprehensive evidence-based information about Parkinson\u27s disease as it applies to occupational therapists. This information was utilized to generate clinical guidelines in the form of a user-friendly manual meant for practicing OTs in treating Parkinson\u27s disease. An extensive literature review was performed using PubMed to determine current evidence-based practice that occupational therapists and other rehabilitation therapists were currently using. Following the review of literature, a needs assessment was completed per survey directed towards practicing OTs. The goal of the survey was to validate the need for these guidelines throughout the country. The user-friendly manual is based on the Ecological Model of Human Performance using establish/restore, adapt/modify and prevent as intervention strategies. The product is titled Guidelines for Occupational Therapists in Treating Parkinson\u27s disease. It consists of four portions, the first focuses on a brief introduction to the disease, the next explains the general neuroscience behind the disease, the third portion gives a brief overview of medical interventions including pharmacological and surgical. The fourth part of the product consists of the evidence-based guidelines for OTs to follow when treating persons with Parkinson\u27s disease. Occupational therapy offers many benefits to persons with Parkinson\u27s disease, including modification and/or adaptation of activities of daily living CADLs) with or without the use of adaptive equipment. Other intervention areas OTs may focus on are: therapeutic exercise routines, caregiver education, joint movement coordination, energy conservation and social skills · training. This user-friendly manual will provide occupational therapists with the necessary information to treat persons with Parkinson\u27s disease using evidence based guidelines

Motor Adaptation and Automaticity in People with Parkinson’s Disease and Freezing of Gait

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by cell death in the substantia nigra pars compacta, resulting in motor symptoms of tremor, rigidity, bradykinesia and gait impairment. Freezing of gait (FOG) is one serious gait disturbance, characterized by a transient inability produce effective stepping during walking and turning, and affects roughly half of people with PD at some point during their disease. Despite the ongoing research on the behavioral, neurological, and cognitive characteristics of people with FOG (PD+FOG), the mechanisms underlying freezing are still poorly understood. The overall aim of this work was to further investigate motor behavior in PD+FOG to provide insight into its potential mechanisms. The first experiment investigated possible cerebellar dysfunction in PD+FOG by examining visuomotor adaptation, a well-known cerebellar-dependent process. We found that there were no differences in reaching or walking adaptation between freezers and non-freezers, however non-freezers exhibited smaller after-effects compared to freezers and healthy older adults. Furthermore, adults with PD, as well as older and younger adults adapt walking patterns slower than reaching patterns, indicating walking is a more complex task requiring greater sensorimotor processing to modify. Overall, this study showed that cerebellar function, in terms of its role in sensorimotor adaptation, is relatively preserved in PD and FOG. In the second experiment, we examined motor automaticity of saccadic eye movements and reaching. Reduced automaticity is a likely motor-cognitive mechanism that contributes to freezing behavior, however automaticity in other motor systems has yet to fully described. Using an anti-saccade task, we found that PD+FOG participants were slower to respond to both automatic and non-automatic eye movements, and had increased saccade velocity variability compared to PD-FOG and controls. These changes were not related to disease severity or general cognition. In contrast, both PD groups were slower to execute (greater latency) reaching movements during both pro- and anti-reaching, but no freezer non-freezer differences were noted. PD+FOG reached with lower peak velocity compared to older adults but were similar to PD-FOG during both automatic and non-automatic conditions. These data show that changes in automaticity and control exist outside locomotor centers, indicating freezing may be a global motor disturbance. Altogether, the work in this dissertation furthers our knowledge on motor control in PD+FOG and provides additional evidence that freezing affects non-gait motor function

2008 Progress Report on Brain Research

Highlights new research on various disorders, nervous system injuries, neuroethics, neuroimmunology, pain, sense and body function, stem cells and neurogenesis, and thought and memory. Includes essays on arts and cognition and on deep brain stimulation

Adaptive Neural Models of Queuing and Timing in Fluent Action

Temporal structure in skilled, fluent action exists at several nested levels. At the largest scale considered here, short sequences of actions that are planned collectively in prefrontal cortex appear to be queued for performance by a cyclic competitive process that operates in concert with a parallel analog representation that implicitly specifies the relative priority of elements of the sequence. At an intermediate scale, single acts, like reaching to grasp, depend on coordinated scaling of the rates at which many muscles shorten or lengthen in parallel. To ensure success of acts such as catching an approaching ball, such parallel rate scaling, which appears to be one function of the basal ganglia, must be coupled to perceptual variables, such as time-to-contact. At a fine scale, within each act, desired rate scaling can be realized only if precisely timed muscle activations first accelerate and then decelerate the limbs, to ensure that muscle length changes do not under- or over-shoot the amounts needed for the precise acts. Each context of action may require a much different timed muscle activation pattern than similar contexts. Because context differences that require different treatment cannot be known in advance, a formidable adaptive engine-the cerebellum-is needed to amplify differences within, and continuosly search, a vast parallel signal flow, in order to discover contextual "leading indicators" of when to generate distinctive parallel patterns of analog signals. From some parts of the cerebellum, such signals controls muscles. But a recent model shows how the lateral cerebellum, such signals control muscles. But a recent model shows how the lateral cerebellum may serve the competitive queuing system (in frontal cortex) as a repository of quickly accessed long-term sequence memories. Thus different parts of the cerebellum may use the same adaptive engine system design to serve the lowest and the highest of the three levels of temporal structure treated. If so, no one-to-one mapping exists between levels of temporal structure and major parts of the brain. Finally, recent data cast doubt on network-delay models of cerebellar adaptive timing.National Institute of Mental Health (R01 DC02852