Risk-taking bias in human decision-making is encoded via a right-left brain push-pull system.

A person's decisions vary even when options stay the same, like when a gambler changes bets despite constant odds of winning. Internal bias (e.g., emotion) contributes to this variability and is shaped by past outcomes, yet its neurobiology during decision-making is not well understood. To map neural circuits encoding bias, we administered a gambling task to 10 participants implanted with intracerebral depth electrodes in cortical and subcortical structures. We predicted the variability in betting behavior within and across patients by individual bias, which is estimated through a dynamical model of choice. Our analysis further revealed that high-frequency activity increased in the right hemisphere when participants were biased toward risky bets, while it increased in the left hemisphere when participants were biased away from risky bets. Our findings provide electrophysiological evidence that risk-taking bias is a lateralized push-pull neural system governing counterintuitive and highly variable decision-making in humans.

The influences and neural correlates of past and present during gambling in humans.

During financial decision-making tasks, humans often make "rational" decisions, where they maximize expected reward. However, this rationality may compete with a bias that reflects past outcomes. That is, if one just lost money or won money, this may impact future decisions. It is unclear how past outcomes influence future decisions in humans, and how neural circuits encode present and past information. In this study, six human subjects performed a financial decision-making task while we recorded local field potentials from multiple brain structures. We constructed a model for each subject characterizing bets on each trial as a function of present and past information. The models suggest that some patients are more influenced by previous trial outcomes (i.e., previous return and risk) than others who stick to more fixed decision strategies. In addition, past return and present risk modulated with the activity in the cuneus; while present return and past risk modulated with the activity in the superior temporal gyrus and the angular gyrus, respectively. Our findings suggest that these structures play a role in decision-making beyond their classical functions by incorporating predictions and risks in humans' decision strategy, and provide new insight into how humans link their internal biases to decisions.

The Role of Associative Cortices and Hippocampus during Movement Perturbations.

Although motor control has been extensively studied, most research involving neural recordings has focused on primary motor cortex, pre-motor cortex, supplementary motor area, and cerebellum. These regions are involved during normal movements, however, associative cortices and hippocampus are also likely involved during perturbed movements as one must detect the unexpected disturbance, inhibit the previous motor plan, and create a new plan to compensate. Minimal data is available on these brain regions during such "robust" movements. Here, epileptic patients implanted with intracerebral electrodes performed reaching movements while experiencing occasional unexpected force perturbations allowing study of the fronto-parietal, limbic and hippocampal network at unprecedented high spatial, and temporal scales. Areas including orbitofrontal cortex (OFC) and hippocampus showed increased activation during perturbed trials. These results, coupled with a visual novelty control task, suggest the hippocampal MTL-P300 novelty response is modality independent, and that the OFC is involved in modifying motor plans during robust movement.

Lucky Rhythms in Orbitofrontal Cortex Bias Gambling Decisions in Humans.

It is well established that emotions influence our decisions, yet the neural basis of this biasing effect is not well understood. Here we directly recorded local field potentials from the OrbitoFrontal Cortex (OFC) in five human subjects performing a financial decision-making task. We observed a striking increase in gamma-band (36-50 Hz) oscillatory activity that reflected subjects' decisions to make riskier choices. Additionally, these gamma rhythms were linked back to mismatched expectations or "luck" occurring in past trials. Specifically, when a subject expected to win but lost, the trial was defined as "unlucky" and when the subject expected to lose but won, the trial was defined as "lucky". Finally, a fading memory model of luck correlated to an objective measure of emotion, heart rate variability. Our findings suggest OFC may play a pivotal role in processing a subject's internal (emotional) state during financial decision-making, a particularly interesting result in light of the more recent "cognitive map" theory of OFC function.

A systematic approach to selecting task relevant neurons.

BACKGROUND: Since task related neurons cannot be specifically targeted during surgery, a critical decision to make is to select which neurons are task-related when performing data analysis. Including neurons unrelated to the task degrade decoding accuracy and confound neurophysiological results. Traditionally, task-related neurons are selected as those with significant changes in firing rate when a stimulus is applied. However, this assumes that neurons' encoding of stimuli are dominated by their firing rate with little regard to temporal dynamics. NEW METHOD: This paper proposes a systematic approach for neuron selection, which uses a likelihood ratio test to capture the contribution of stimulus to spiking activity while taking into account task-irrelevant intrinsic dynamics that affect firing rates. This approach is denoted as the model deterioration excluding stimulus (MDES) test. RESULTS: MDES is compared to firing rate selection in four case studies: a simulation, a decoding example, and two neurophysiology examples. COMPARISON WITH EXISTING METHODS: The MDES rankings in the simulation match closely with ideal rankings, while firing rate rankings are skewed by task-irrelevant parameters. For decoding, 95% accuracy is achieved using the top 8 MDES-ranked neurons, while the top 12 firing-rate ranked neurons are needed. In the neurophysiological examples, MDES matches published results when firing rates do encode salient stimulus information, and uncovers oscillatory modulations in task-related neurons that are not captured when neurons are selected using firing rates. CONCLUSIONS: These case studies illustrate the importance of accounting for intrinsic dynamics when selecting task-related neurons and following the MDES approach accomplishes that. MDES selects neurons that encode task-related information irrespective of these intrinsic dynamics which can bias firing rate based selection.

Use of negative pressure wound therapy with automated, volumetric instillation for the treatment of extremity and trunk wounds: clinical outcomes and potential cost-effectiveness.

OBJECTIVE: A growing body of literature supports use of negative pressure wound therapy (NPWT) with instillation and dwell time (NPWTi-d) with positive clinical outcomes and potential cost savings. A retrospective analysis was performed to compare clinical outcomes of wounds treated with NPWTi-d versus NPWT and to estimate cost-differences between treatments based on clinical outcomes. METHODS: Data were extracted from records of patients with extremity or trunk wounds treated with NPWT (n = 34) or NPWTi-d using saline or polyhexanide (n = 48). On the basis of outcomes data, a hypothetical economic model using cost assumptions was created to calculate cost savings for NPWTi-d (related to) number of debridements and length of therapy. Operating room debridement cost was $3393 according to Granick et al. Daily therapy cost for each modality was $194.80 (NPWTi-d) and $106.08 (NPWT) based on internal company information. RESULTS: RESULTS showed significant differences (P < 0.0001) between NPWTi-d and NPWT patients, respectively, for the following: mean operating room debridements (2.0 vs 4.4), mean hospital stay (8.1 vs 27.4 days), mean length of therapy (4.1 vs 20.9 days), and mean time to wound closure (4.1 vs 20.9 days). Hypothetical economic model showed potential average reduction of $8143 for operating room debridements between NPWTi-d ($6786) and NPWT ($14,929) patients. There was a $1418 difference in average therapy costs between groups ($799/NPWTi-d vs $2217/NPWT). CONCLUSIONS: In this study, NPWTi-d appeared to assist in wound cleansing and exudate removal, which may have allowed for earlier wound closure compared to NPWT. Hypothetical economic model findings illustrate potential cost-effectiveness of NPWTi-d compared to NPWT.

Performing behavioral tasks in subjects with intracranial electrodes.

Patients having stereo-electroencephalography (SEEG) electrode, subdural grid or depth electrode implants have a multitude of electrodes implanted in different areas of their brain for the localization of their seizure focus and eloquent areas. After implantation, the patient must remain in the hospital until the pathological area of brain is found and possibly resected. During this time, these patients offer a unique opportunity to the research community because any number of behavioral paradigms can be performed to uncover the neural correlates that guide behavior. Here we present a method for recording brain activity from intracranial implants as subjects perform a behavioral task designed to assess decision-making and reward encoding. All electrophysiological data from the intracranial electrodes are recorded during the behavioral task, allowing for the examination of the many brain areas involved in a single function at time scales relevant to behavior. Moreover, and unlike animal studies, human patients can learn a wide variety of behavioral tasks quickly, allowing for the ability to perform more than one task in the same subject or for performing controls. Despite the many advantages of this technique for understanding human brain function, there are also methodological limitations that we discuss, including environmental factors, analgesic effects, time constraints and recordings from diseased tissue. This method may be easily implemented by any institution that performs intracranial assessments; providing the opportunity to directly examine human brain function during behavior.

New advances in instillation therapy in wounds at risk for compromised healing.

Combined use of adjunctive negative pressure wound therapy (NPWT) and instillation of topical wound solutions and suspensions (NPWTi) has proven to be an effective next-generation NPWT technique for wounds at risk for compromised healing. Fluid instillation has been shown to enhance exudate and debris removal, provide regular cleansing of the wound bed, and add moisture to the wound. Positive results have been demonstrated with NPWTi in assisting healing of stalled wounds and treating painful wounds as well as wounds at high risk for amputation. NPWTi has been used instead of conventional NPWT in wounds with thick exudate and slough content, acute traumatic wounds, wounds acutely debrided due to infected soft tissue, large areas of post-debrided exposed bone, and cases of critical bacterial colonization. Instilled solutions have included topical solutions such as saline, topical wound cleansers, and antiseptics. While various systems that combine instillation or irrigation with NPWT have been commercialized during the past decade, until very recently these have been relatively cumbersome to use and limited in their ability to regulate solution volume delivery. Recent advances in NPWTi technology (V.A.C. VeraFlo™ Therapy, KCI, San Antonio, TX) include automated volumetrically controlled delivery of fluids and upgraded foam dressing technology to provide better control and delivery of solutions to the wound bed. This article describes the latest NPWTi technology and provides recommendations for successful application of NPWTi in an effort to inform clinicians about product decision-making and practice.

It IS a tumor -- current review of headache and brain tumor.

"Do I have a tumor?" This is a question in every person's mind when first confronted with a new-onset headache, a question that causes considerable anxiety among patients, leading them to seek medical evaluation. This publication reviews the current literature with respect to the epidemiology, pathophysiology presentation, and treatment of headaches in association with intracranial neoplasm.

High frequency activity correlates of robust movement in humans.

The neural circuitry underlying fast robust human motor control is not well understood. In this study we record neural activity from multiple stereotactic encephalograph (SEEG) depth electrodes in a human subject while he/she performs a center-out reaching task holding a robotic manipulandum that occasionally introduces an interfering force field. Collecting neural data from humans during motor tasks is rare, and SEEG provides an unusual opportunity to examine neural correlates of movement at a millisecond time scale in multiple brain regions. Time-frequency analysis shows that high frequency activity (50-150 Hz) increases significantly in the left precuneus and left hippocampus when the subject is compensating for a perturbation to their movement. These increases in activity occur with different durations indicating differing roles in the motor control process.

Oscillations in human orbitofrontal cortex during even chance gambling.

Evaluating value and risk as well as comparing expected and actual outcomes is the crux of decision making and reinforcement based learning. In this study, we record from stereotactic electroencephalograph depth electrodes in a human subject in numerous areas in the brain. We focus on the lateral and medial orbitofrontal cortex while they perform a gambling task involving betting on a high card. Preliminary time-frequency analysis shows modulations in the 5-15 Hz band that is well synced to the different events of the task. These oscillations increase in both high betting scenarios as well as in losing scenarios though their effects cannot be decoupled. However, the activity between lateral and medial orbitofrontal cortex is a lot more homogenous than previously seen. Additionally, the timing of some of these oscillations occurs before even a response in the visual cortex. This evidence hints that these areas encode priors that influence our decision in future statistically ambiguous scenarios.

Neuron selection for decoding dexterous finger movements.

Many brain machine interfaces (BMI) seek to use the activity from hundreds of simultaneously recorded neurons to reconstruct an individual's kinematics. However, many of these neurons are not task related since there is no way to surgically target those neurons. This causes model based decoding to suffer easily from over-fitting on noisy unrelated neurons. Previous methods, such as correlation analysis and sensitivity analysis, seek to select neurons based on which reduced order model best matches the ensemble model and thus does not worry about over fitting. To address this issue, this paper presents a new method, cross model validation, that ranks neuron importance on the neuron model's ability to generalize well to data from correct movements and poorly to data from incorrect movements. This method attempts to highlight the neurons that are able to distinguish between movements the best and decode accurately. Selecting neurons using cross model validation scores as opposed to randomly selecting them can increase decoding accuracy up to 2.5 times or by 44%. These results showcase the importance of neuron selection in decoding and the ability of cross model validation in discerning each neuron's utility in decoding.

Severe postvaccinia encephalitis with acute disseminated encephalomyelitis: recovery with early intravenous immunoglobulin, high-dose steroids, and vaccinia immunoglobulin.

We report the second case of severe postvaccinial encephalitis with acute disseminated encephalomyelitis since smallpox vaccination was reintroduced in 2002. Both affected patients responded dramatically with early intervention of intravenous immunoglobulin. Our patient, who also received concurrent vaccinia immunoglobulin and corticosteroids, demonstrated full recovery.

Predictors of disability in migraineurs referred to a tertiary clinic: neck pain, headache characteristics, and coping behaviors.

OBJECTIVE: The aim of this retrospective study was to determine if neck pain, select headache characteristics, and migraine-related coping response predicted disability in migraineurs referred to a tertiary headache clinic. METHODS: Patients seeking treatment at a neurology-based headache clinic were included if they met diagnostic criteria for migraine with or without aura according to the International Headache Society (1.1, 1.2). Subjects completed a self-report headache history form and a detailed headache and neurologic examination. The headache history form assessed: 1)weekly headache frequency; 2) number of weekly severe headaches; 3) presence of migraine-related neck pain; 4) photophobia; 5) phonophobia; 6) headache duration; 7) vomiting; 8) monthly headache-free days; and 9) behavioral coping style. Disability was assessed using a self-report inventory (HIT-6). RESULTS: Self-reported headache severity, frequency, and headache-free days were strongly associated with disability. The presence of neck pain during migraine and one's coping response to migraine significantly predicted disability independent of headache characteristics. CONCLUSIONS: These data suggest the need for prospective research exploring the causal mechanisms by which neck pain and coping response influence disability and underscores the importance of multidisciplinary approaches to headache management.

The prevalence and spectrum of sleep problems in women with transformed migraine.

OBJECTIVES: It is our clinical observation that patients with transformed migraine (TM) almost invariably report nonrestorative sleep. In this study we sought first to validate that clinical observation, then to describe the prevalence and spectrum of factors that might contribute to nonrestorative sleep in a TM population. BACKGROUND: Although headaches have been linked with sleep problems for over a century, there is little information about the spectrum or prevalence of specific sleep problems associated with TM in adults. METHODS: We conducted a detailed sleep interview on 147 consecutive women with TM. Subjective sleep quality was assessed by asking patients to describe their state upon awakening as "refreshed" or "tired." RESULTS: None of the 147 patients reported awakening "refreshed," and 83.7% stated that they awakened "tired." Sleep complaints were prevalent and varied in this population. CONCLUSIONS: Although the relationship between pain and sleep is complex and ill understood, we found a very high prevalence of nonrestorative sleep and a similarly high prevalence of modifiable poor sleep habits in patients with TM. Since behavioral approaches have been found effective in improving sleep quality in patients with poor sleep hygiene, we propose that studies be undertaken to assess the impact of such treatment on TM.

Psychometric properties of the HIT-6 among patients in a headache-specialty practice.

OBJECTIVE: To evaluate the performance and score interpretability of the Headache Impact Test (HIT-6) questionnaire in a headache patient population. BACKGROUND: The HIT-6 is a standardized questionnaire designed to assess headache-related disability. Norms have been established using randomly sampled respondents from the general population. This study evaluated the psychometric properties of the HIT-6 scale among new adult patients who presented for treatment at a university headache-specialty practice. METHODS: Participants were 309 new patients who presented for treatment at a headache-specialty clinic in an academic medical center. RESULTS: Respondents ranged in age from 18 to 91 years, with an average age of 41 years (SD = 13 years) and were predominantly female (77%). Over half (57%) experienced chronic daily headache. Scores ranged from 38 to 78, with an average of 65.6 (SD = 7.0) and the majority (87%) had "severe impact" (60 or higher). The scale showed high reliability (alpha= 0.87) and an exploratory factor analysis showed large loadings from |0.57| to |0.86| and suggested a single disability factor. Scores were moderately negatively correlated with Short Form Health Survey (SF-36) subscales, ranging from -0.22 for mental health to -0.57 for social functioning. Item response theory analyses showed that half of the items functioned well across the disability continuum, while the remaining items discriminated between low and high levels of headache impact. CONCLUSIONS: These findings suggest that the HIT-6 is useful for assessing headache-related disability among patients who seek headache-specialty care.

Hinged external fixation of the knee: intrinsic factors influencing passive joint motion.

OBJECTIVE: To measure changes in knee kinematics after the application of articulated external fixators along a previously described knee flexion/extension axis and 16 specific "off-axis" fixator hinge configurations. DESIGN: Cadaver, biomechanical study. SETTING: Biomechanics laboratory. PARTICIPANTS: Nine fresh cadaver knee specimens. INTERVENTION: Each specimen was mounted on a custom-built frame that constrained the knee to move about a fixed flexion/extension axis. Passive knee motion was induced, and the resulting flexion moment was measured. Data were collected for the on-axis fixator position and 16 distinct rotational and translational off-axis positions. In addition, effects of tibial translation and rotation were investigated. MAIN OUTCOME: Range of motion (ROM) attainable within a moment envelope of +/-1 N-m and average energy required to impart movement. RESULTS: The average ROM for unconstrained knees was 122 degree. Constraining the knee to rotation around an on-axis aligned hinge significantly reduced the ROM by 35% to 79 degree. The 5-mm posterior translated hinge was the only alignment to show on average a slightly larger ROM (86 degree) than the on-axis hinge. All other hinge alignments showed decreased average ROM compared with the on-axis position. Tibiofemoral alignments significantly affected the obtainable ROM for the on-axis aligned hinge. CONCLUSION: It was not possible to replicate precisely the complex kinematics of the knee using a single axis fixator over the entire ROM. Using the axis of rotation previously defined in the literature, however, it was possible to obtain a limited ROM of the knee without placing excessive forces on the periarticular structures.

Malrotation after locked intramedullary tibial nailing: three case reports and review of the literature.

BACKGROUND: Malrotation after interlocked tibial nailing is rarely documented. METHODS: We report the cases of three patients who incurred symptomatic rotational deformities after closed intramedullary nailing for low-energy spiral fractures of the distal third of the tibia. RESULTS: Two patients elected surgical correction, with excellent clinical results. CONCLUSION: Malrotation may cause functional deficits, but the long-term consequences of rotational deformities in the tibia have not been thoroughly studied. Malrotation after tibial nailing is probably more common than reported. Intraoperative comparison with the uninjured leg may be the best means available for avoiding this postoperative complication.