Moving Beyond the Keypress: As Technology Advances, so Should Psychology Response Time Measurements.

Decades of research in cognitive psychology have largely relied on simple key or button presses to quantify human behavior. While many valuable discoveries have been made, a richer response modality may reveal more information regarding the different processes that underlie complex human behavior. This study provides a proof of concept for using a touch-and-swipe response method to separate response time into two components to extract more meaningful behavioral insights. Across several analyses, the two components were consistently shown to be separable, independent measurements of behavior. Furthermore, evaluating these isolated response time components improved inferential power and clarity of behavioral patterns. The touch-and-swipe response method is simple and easy-to-use, and it shows promise for more accurately targeting mechanisms of interest.

Baseline Differences in Anxiety Affect Attention and tDCS-Mediated Learning.

Variable responses to transcranial direct current stimulation (tDCS) protocols across individuals are widely reported, but the reasons behind this variation are unclear. This includes tDCS protocols meant to improve attention. Attentional control is impacted by top-down and bottom-up processes, and this relationship is affected by state characteristics such as anxiety. According to Attentional Control Theory, anxiety biases attention towards bottom-up and stimulus-driven processing. The goal of this study was to explore the extent to which differences in state anxiety and related measures affect visual attention and category learning, both with and without the influence of tDCS. Using discovery learning, participants were trained to classify pictures of European streets into two categories while receiving 30 min of 2.0 mA anodal, cathodal, or sham tDCS over the rVLPFC. The pictures were classifiable according to two separate rules, one stimulus and one hypothesis-driven. The Remote Associates Test (RAT), Profile of Mood States, and Attention Networks Task (ANT) were used to understand the effects of individual differences at baseline on subsequent tDCS-mediated learning. Multinomial logistic regression was fit to predict rule learning based on the baseline measures, with subjects classified according to whether they used the stimulus-driven or hypothesis-driven rule to classify the pictures. The overall model showed a classification accuracy of 74.1%. The type of tDCS stimulation applied, attentional orienting score, and self-reported mood were significant predictors of different categories of rule learning. These results indicate that anxiety can influence the quality of subjects' attention at the onset of the task and that these attentional differences can influence tDCS-mediated category learning during the rapid assessment of visual scenes. These findings have implications for understanding the complex interactions that give rise to the variability in response to tDCS.

Assessing the Impact of Ih Conductance on Cross-Frequency Coupling in Model Pyramidal Neurons.

Large cortical and hippocampal pyramidal neurons are elements of neuronal circuitry that have been implicated in cross-frequency coupling (CFC) during cognitive tasks. We investigate potential mechanisms for CFC within these neurons by examining the role that the hyperpolarization-activated mixed cation current (Ih) plays in modulating CFC characteristics in multicompartment neuronal models. We quantify CFC along the soma-apical dendrite axis and tuft of three models configured to have different spatial distributions of Ih conductance density: (1) exponential gradient along the soma-apical dendrite axis, (2) uniform distribution, and (3) no Ih conductance. We simulated two current injection scenarios: distal apical 4 Hz modulation and perisomatic 4 Hz modulation, each with perisomatic, mid-apical, and distal apical 40 Hz injections. We used two metrics to quantify CFC strength-modulation index and height ratio-and we analyzed CFC phase properties. For all models, CFC was strongest in distal apical regions when the 40 Hz injection occurred near the soma and the 4 Hz modulation occurred in distal apical dendrite. The strongest CFC values were observed in the model with uniformly distributed Ih conductance density, but when the exponential gradient in Ih conductance density was added, CFC strength decreased by almost 50%. When Ih was in the model, regions with much larger membrane potential fluctuations at 4 Hz than at 40 Hz had stronger CFC. Excluding the Ih conductance from the model resulted in CFC either reduced or comparable in strength relative to the model with the exponential gradient in Ih conductance. The Ih conductance also imposed order on the phase characteristics of CFC such that minimum (maximum) amplitude 40 Hz membrane potential oscillations occurred during Ih conductance deactivation (activation). On the other hand, when there was no Ih conductance, phase relationships between minimum and maximum 40 Hz oscillation often inverted and occurred much closer together. This analysis can help experimentalists discriminate between CFC that originates from different underlying physiological mechanisms and can help illuminate the reasons why there are differences between CFC strength observed in different regions of the brain and between different populations of neurons based on the configuration of the Ih conductance.

Transcranial direct current stimulation facilitates category learning.

BACKGROUND: After two decades of transcranial direct current stimulation (tDCS) research, it is still unclear which applications benefit most from which tDCS protocols. One prospect is the acceleration of learning, where previous work has demonstrated that anodal tDCS applied to the right ventrolateral prefrontal cortex (rVLPFC) is capable of doubling the rate of learning in a visual camouflaged threat detection and category learning task. GOALS: Questions remain as to the specific cognitive mechanisms underlying this learning enhancement, and whether it generalizes to other tasks. The goal of the current project was to expand previous findings by employing a novel category learning task. METHODS: Participants learned to classify pictures of European streets within a discovery learning paradigm. In a double-blind design, 54 participants were randomly assigned to 30 min of tDCS using either 2.0 mA anodal (n = 18), cathodal (n = 18), or 0.1 mA sham (n = 18) tDCS over the rVLPFC. RESULTS: A linear mixed-model revealed a significant effect of tDCS condition on classification accuracy across training (p = 0.001). Compared to a 4.2% increase in sham participants, anodal tDCS over F10 increased performance by 20.6% (d = 1.71) and cathodal tDCS by 14.4% (d = 1.16). CONCLUSIONS: These results provide further evidence for the capacity of tDCS applied to rVLPFC to enhance learning, showing a greater than quadrupling of test performance after training (491% of sham) in a difficult category learning task. Combined with our previous studies, these results suggest a generalized performance enhancement. Other tasks requiring sustained attention, insight and/or category learning may also benefit from this protocol.

Enabling Large-Scale Simulations With the GENESIS Neuronal Simulator.

In this paper, we evaluate the computational performance of the GEneral NEural SImulation System (GENESIS) for large scale simulations of neural networks. While many benchmark studies have been performed for large scale simulations with leaky integrate-and-fire neurons or neuronal models with only a few compartments, this work focuses on higher fidelity neuronal models represented by 50-74 compartments per neuron. After making some modifications to the source code for GENESIS and its parallel implementation, PGENESIS, particularly to improve memory usage, we find that PGENESIS is able to efficiently scale on supercomputing resources to network sizes as large as 9 × 106 neurons with 18 × 109 synapses and 2.2 × 106 neurons with 45 × 109 synapses. The modifications to GENESIS that enabled these large scale simulations have been incorporated into the May 2019 Official Release of PGENESIS 2.4 available for download from the GENESIS web site (genesis-sim.org).

Laboratory Administration of Transcutaneous Auricular Vagus Nerve Stimulation (taVNS): Technique, Targeting, and Considerations.

Non-invasive vagus nerve stimulation (VNS) may be administered via a novel, emerging neuromodulatory technique known as transcutaneous auricular vagus nerve stimulation (taVNS). Unlike cervically-implanted VNS, taVNS is an inexpensive and non-surgical method used to modulate the vagus system. taVNS is appealing as it allows for rapid translation of basic VNS research and serves as a safe, inexpensive, and portable neurostimulation system for the future treatment of central and peripheral disease. The background and rationale for taVNS is described, along with electrical and parametric considerations, proper ear targeting and attachment of stimulation electrodes, individual dosing via determination of perception threshold (PT), and safe administration of taVNS.

Increased Excitability Induced in the Primary Motor Cortex by Transcranial Ultrasound Stimulation.

Background: Transcranial Ultrasound Stimulation (tUS) is an emerging technique that uses ultrasonic waves to noninvasively modulate brain activity. As with other forms of non-invasive brain stimulation (NIBS), tUS may be useful for altering cortical excitability and neuroplasticity for a variety of research and clinical applications. The effects of tUS on cortical excitability are still unclear, and further complications arise from the wide parameter space offered by various types of devices, transducer arrangements, and stimulation protocols. Diagnostic ultrasound imaging devices are safe, commonly available systems that may be useful for tUS. However, the feasibility of modifying brain activity with diagnostic tUS is currently unknown. Objective: We aimed to examine the effects of a commercial diagnostic tUS device using an imaging protocol on cortical excitability. We hypothesized that imaging tUS applied to motor cortex could induce changes in cortical excitability as measured using a transcranial magnetic stimulation (TMS) motor evoked potential (MEP) paradigm. Methods: Forty-three subjects were assigned to receive either verum (n = 21) or sham (n = 22) diagnostic tUS in a single-blind design. Baseline motor cortex excitability was measured using MEPs elicited by TMS. Diagnostic tUS was subsequently administered to the same cortical area for 2 min, immediately followed by repeated post-stimulation MEPs recorded up to 16 min post-stimulation. Results: Verum tUS increased excitability in the motor cortex (from baseline) by 33.7% immediately following tUS (p = 0.009), and 32.4% (p = 0.047) 6 min later, with excitability no longer significantly different from baseline by 11 min post-stimulation. By contrast, subjects receiving sham tUS showed no significant changes in MEP amplitude. Conclusion: These findings demonstrate that tUS delivered via a commercially available diagnostic imaging ultrasound system transiently increases excitability in the motor cortex as measured by MEPs. Diagnostic tUS devices are currently used for internal imaging in many health care settings, and the present results suggest that these same devices may also offer a promising tool for noninvasively modulating activity in the central nervous system. Further studies exploring the use of diagnostic imaging devices for neuromodulation are warranted.

Resonance Analysis as a Tool for Characterizing Functional Division of Layer 5 Pyramidal Neurons.

Evidence suggests that layer 5 pyramidal neurons can be divided into functional zones with unique afferent connectivity and membrane characteristics that allow for post-synaptic integration of feedforward and feedback inputs. To assess the existence of these zones and their interaction, we characterized the resonance properties of a biophysically-realistic compartmental model of a neocortical layer 5 pyramidal neuron. Consistent with recently published theoretical and empirical findings, our model was configured to have a "hot zone" in distal apical dendrite and apical tuft where both high- and low-threshold Ca2+ ionic conductances had densities 1-2 orders of magnitude higher than anywhere else in the apical dendrite. We simulated injection of broad spectrum sinusoidal currents with linearly increasing frequency to calculate the input impedance of individual compartments, the transfer impedance between the soma and key compartments within the dendritic tree, and a dimensionless term we introduce called resonance quality. We show that input resonance analysis distinguished at least four distinct zones within the model based on properties of their frequency preferences: basal dendrite which displayed little resonance; soma/proximal apical dendrite which displayed resonance at 5-23 Hz, strongest at 5-10 Hz and hyperpolarized/resting membrane potentials; distal apical dendrite which displayed resonance at 8-19 Hz, strongest at 10 Hz and depolarized membrane potentials; and apical tuft which displayed a weak resonance largely between 8 and 10 Hz across a wide range of membrane potentials. Transfer resonance analysis revealed that changes in subthreshold electrical coupling were found to modulate the transfer resonant frequency of signals transmitted from distal apical dendrite and apical tuft to the soma, which would impact the frequencies that individual neurons are expected to respond to and reinforce. Furthermore, eliminating the hot zone was found to reduce amplification of resonance within the model, which contributes to reduced excitability when perisomatic and distal apical regions receive coincident stimulating current injections. These results indicate that the interactions between different functional zones should be considered in a more complete understanding of neuronal integration. Resonance analysis may therefore be a useful tool for assessing the integration of inputs across the entire neuronal membrane.

Impact of Neuronal Membrane Damage on the Local Field Potential in a Large-Scale Simulation of Cerebral Cortex.

Within multiscale brain dynamics, the structure-function relationship between cellular changes at a lower scale and coordinated oscillations at a higher scale is not well understood. This relationship may be particularly relevant for understanding functional impairments after a mild traumatic brain injury (mTBI) when current neuroimaging methods do not reveal morphological changes to the brain common in moderate to severe TBI such as diffuse axonal injury or gray matter lesions. Here, we created a physiology-based model of cerebral cortex using a publicly released modeling framework (GEneral NEural SImulation System) to explore the possibility that performance deficits characteristic of blast-induced mTBI may reflect dysfunctional, local network activity influenced by microscale neuronal damage at the cellular level. We operationalized microscale damage to neurons as the formation of pores on the neuronal membrane based on research using blast paradigms, and in our model, pores were simulated by a change in membrane conductance. We then tracked changes in simulated electrical activity. Our model contained 585 simulated neurons, comprised of 14 types of cortical and thalamic neurons each with its own compartmental morphology and electrophysiological properties. Comparing the functional activity of neurons before and after simulated damage, we found that simulated pores in the membrane reduced both action potential generation and local field potential (LFP) power in the 1-40 Hz range of the power spectrum. Furthermore, the location of damage modulated the strength of these effects: pore formation on simulated axons reduced LFP power more strongly than did pore formation on the soma and the dendrites. These results indicate that even small amounts of cellular damage can negatively impact functional activity of larger scale oscillations, and our findings suggest that multiscale modeling provides a promising avenue to elucidate these relationships.

Transformations and representations supporting spatial perspective taking.

Spatial perspective taking is the ability to reason about spatial relations relative to another's viewpoint. Here, we propose a mechanistic hypothesis that relates mental representations of one's viewpoint to the transformations used for spatial perspective taking. We test this hypothesis using a novel behavioral paradigm that assays patterns of response time and variation in those patterns across people. The results support the hypothesis that people maintain a schematic representation of the space around their body, update that representation to take another's perspective, and thereby to reason about the space around their body. This is a powerful computational mechanism that can support imitation, coordination of behavior, and observational learning.

How are bodies special? Effects of body features on spatial reasoning.

Embodied views of cognition argue that cognitive processes are influenced by bodily experience. This implies that when people make spatial judgments about human bodies, they bring to bear embodied knowledge that affects spatial reasoning performance. Here, we examined the specific contribution to spatial reasoning of visual features associated with the human body. We used two different tasks to elicit distinct visuospatial transformations: object-based transformations, as elicited in typical mental rotation tasks, and perspective transformations, used in tasks in which people deliberately adopt the egocentric perspective of another person. Body features facilitated performance in both tasks. This result suggests that observers are particularly sensitive to the presence of a human head and body, and that these features allow observers to quickly recognize and encode the spatial configuration of a figure. Contrary to prior reports, this facilitation was not related to the transformation component of task performance. These results suggest that body features facilitate task components other than spatial transformation, including the encoding of stimulus orientation.

Controllability of structural brain networks.

Cognitive function is driven by dynamic interactions between large-scale neural circuits or networks, enabling behaviour. However, fundamental principles constraining these dynamic network processes have remained elusive. Here we use tools from control and network theories to offer a mechanistic explanation for how the brain moves between cognitive states drawn from the network organization of white matter microstructure. Our results suggest that densely connected areas, particularly in the default mode system, facilitate the movement of the brain to many easily reachable states. Weakly connected areas, particularly in cognitive control systems, facilitate the movement of the brain to difficult-to-reach states. Areas located on the boundary between network communities, particularly in attentional control systems, facilitate the integration or segregation of diverse cognitive systems. Our results suggest that structural network differences between cognitive circuits dictate their distinct roles in controlling trajectories of brain network function.

Limits on action priming by pictures of objects.

When does looking at an object prime actions associated with using it, and what aspects of those actions are primed? We examined whether viewing manmade objects with handles would selectively facilitate responses for the hand closest to the handle, attempting to replicate a study reported by Tucker and Ellis (1998). We also examined whether the hypothesized action priming effects depended upon the response hand's proximity to an object. In 7 experiments, participants made judgments about whether pictured objects were manmade or natural or whether the objects were upright or inverted. They responded by pressing buttons located either on the same or opposite side as the objects' handles, at variable distances. Action priming was observed only when participants were explicitly instructed to imagine picking up the pictured objects while making their judgments; the data provide no evidence for task-general automatic priming of lateralized responses by object handles. These data indicate that visually encoding an object activates spatially localized action representations only under special circumstances.

The role of animacy in spatial transformations.

We present evidence that different mental spatial transformations are used to reason about three different types of items representing a spectrum of animacy: human bodies, nonhuman animals, and inanimate objects. Participants made two different judgments about rotated figures: handedness judgments ("Is this the left or right side?") and matching judgments ("Are these figures the same?"). Perspective-taking strategies were most prevalent when participants made handedness judgments about human bodies and animals. In contrast, participants generally did not imagine changes in perspective to perform matching judgments. Such results suggest that high-level information about semantic categories, including information about a thing's animacy, can influence how spatial representations are transformed when performing online problem solving. Supplemental materials for this article may be downloaded from http://mc.psychonomic-journals.org/content/supplemental.

Prevalence, pattern, and spectrum of glenoid bone loss in anterior shoulder dislocation: CT analysis of 218 patients.

OBJECTIVE: The purpose of our study was to determine the prevalence, pattern, and spectrum of glenoid bone loss in anterior shoulder dislocation, to relate this to the frequency of dislocation, and to test the appropriateness of the measurement method. SUBJECTS AND METHODS: Two hundred eighteen patients with single or recurrent anterior shoulder dislocation underwent shoulder CT examination. Fifteen patients had bilateral dislocation. Prevalence and severity of glenoid bone loss and glenoid fracture were assessed. CT examinations of 56 control subjects without shoulder dislocation were evaluated for glenoid contour and side-to-side variation in glenoid width. RESULTS: Glenoid bone loss was present in 27 (41%) of 66 patients with first-time unilateral dislocation and 118 (86%) of 137 patients with recurrent unilateral dislocation. Glenoid bone loss ranged from -0.3% to -33% (mean, -10.8% +/- 7.9%). Seventy-four (51%) of 145 patients had < or = 10% glenoid bone loss, 54 (37%) had between 10% and 20%, eight (6%) had between 20% and 25% glenoid bone loss, and nine (6%) had > or = 25% glenoid bone loss. Glenoid rim fractures were present in 49 (21%) of 233 dislocated shoulders. The number of dislocations correlated moderately with the severity of glenoid bone loss (r = 0.56). The normal side-to-side glenoid width variation was small (0.46 +/- 0.81 mm). CONCLUSION: Glenoid bone loss is common in anterior shoulder dislocation. It is probably multifactorial in origin, is usually mild in degree, and has a maximum observed severity of -33%. Dislocation frequency cannot accurately predict the degree of bone loss.

First-time shoulder dislocation: High prevalence of labral injury and age-related differences revealed by MR arthrography.

PURPOSE: To evaluate abnormalities and age-related differences after first-time shoulder dislocation. MATERIALS AND METHODS: MRA images of first-time dislocators were assessed for labral-ligamentous-capsular / rotator cuff abnormalities and analyzed the age-related differences (< and >/=30 years old). RESULTS: Sixty-six patients (34 <30 years old vs. 32 >/=30 years; 51 males; all anterior dislocations) were imaged. Forty-eight patients (73%) showed anteroinferior labral avulsion, consisting of: 6% (4/34 vs. 0/32) Perthes; 23% (8/34 vs. 7/32) free ALPSA (anterior labrum periosteal sleeve avulsion) lesion); 6% (1/34 vs. 3/32) adherent ALPSA; 23% (9/34 vs. 6/32) Bankart; 14% (5/34 vs. 4/32) inferiorly displaced avulsed labrum; 2% (1/34 vs. 0/32) GLAD. Extensive labral detachment (extended above 3 o'clock position) was present in 31% (11/28 vs. 4/20). There were 14% (6/34 vs. 3/32) superior labrum anterior-posterior (SLAP) lesion; 27% (1/34 vs. 17/34) rotator cuff tendon tear; 71% (25/34 vs. 22/32) Hill-Sachs defect. Young patients were more likely to have extensive labral avulsions (P = 0.054), but less likely to have rotator cuff tears (P < 0.001). CONCLUSION: A high prevalence and wide variety of labral avulsions after first-time shoulder dislocation, especially adherent ALPSA, inferiorly displaced avulsed labrum, or GLAD lesion, may influence treatment choice and outcome, suggesting a role for early MRA to assist in treatment triage.

Rapid improvement in rheumatoid arthritis patients on combination of methotrexate and infliximab: clinical and magnetic resonance imaging evaluation.

The objectives of this study was to assess, using clinical and magnetic resonance imaging (MRI) criteria, the efficacy of combination infliximab therapy in patients with active rheumatoid arthritis (RA) refractory to methotrexate (MTX) treatment and to ascertain whether the changes in MRI parameters correlate with the clinical response. Four infusions of infliximab (3 mg/kg) at weeks 0, 2, 6, and 14 were added to a stable background dose of MTX in 19 patients with active disease. Clinical parameters were assessed before each infusion and at week 14. Dynamic contrast-enhanced MRI examination of the most severely affected wrist was performed at baseline and week 14. Synovitis severity, volume of synovitis, and synovial perfusion indices were evaluated. Significant improvement in all clinical disease activity parameters was seen at week 14 with reduction in C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and DAS28. Sixty-eight percent of patients achieved ACR20. MRI disease activity parameters also significantly decreased after treatment with reduction in grading of synovitis, volume of active synovitis, and perfusion enhancement slope. Significant positive correlations were seen between the baseline volume of synovitis and the pain score (r=0.65), patient global score (r=0.68), and health assessment questionnaire (HAQ) score (r=0.46). In conclusion, addition of infliximab to methotrexate rapidly reduces inflammation in longstanding patients with RA. Assessment of enhancing synovial volume and perfusion indices on serial MRI examination was helpful in documenting the effect of treatment over this short period.