Matthew J. Euler

Neurocognitive and neurophysiological correlates of motor planning during familiar and novel contexts.

OBJECTIVE Research suggests that behavioral indices of motor planning (i.e., latencies that precede motor output) (a) relate to processing speed (PS) and executive functioning (EF), but not working memory (WM), and (b) deteriorate in novel contexts. It is not clear whether an electrophysiological index of motor planning (i.e., movement-related cortical potentials; MRCPs) also relates to PS and EF, and whether it deteriorates in novel contexts. This study sought to clarify associations among these variables while manipulating contextual novelty. METHOD Forty healthy adults completed standardized measures of PS, EF, and WM. Participants performed highly familiar motor sequences in familiar versus novel contexts during EEG recording, while motor planning latencies and peak MRCPs were obtained. Hierarchical regressions assessed the relative contributions of PS, EF, and WM to motor planning latencies and MRCPs. RESULTS Novel contexts elicited longer planning latencies (gav = 1.96) and reduced MRCPs (gav = .24) compared to familiar contexts. PS predicted planning times in both familiar (R² = .12) and novel contexts (R² = .15), while EF contributed additional variance during novel contexts only (R² Change = .10). EF was the sole predictor of MRCPs in both familiar (R² = .12) and novel contexts (R² = .18). WM did not predict planning latencies or MRCPs. CONCLUSIONS Contextual novelty alone can decrease performance and neural activation during complex sequencing. The general link between preparatory activation and EF suggests that capacity limitations drive novelty effects, and implies a common substrate underlying motor planning and higher-order behavioral control.

The impact of developmental instability on Voxel-Based Morphometry analyses of neuroanatomical abnormalities in schizophrenia.

The etiologic factors underlying schizophrenia have been conceptualized as reflecting two largely genetic components - those unique to schizophrenia and those representing vulnerability to neurodevelopmental deviation in general. The Developmental Instability (DI) approach suggests that the latter can be indexed by minor physical anomalies (MPAs), which assess early prenatal growth abnormalities, and fluctuating anatomic asymmetries (FA), which reflects later deviations. Individuals with schizophrenia (N=19) had elevated scores on both measures as compared to healthy controls (N=23). Further, MPAs and FA were very highly correlated in the sample of individuals with schizophrenia but not in controls. In order to identify neuroanatomic variation linked with the unique factor, we conducted gray matter Voxel Based Morphometry analyses of group membership, with and without treating a composite measure of DI (based on FA, and MPAs) as a covariate. When DI was treated as a covariate, many more gray matter regions were found to statistically differ as a function of diagnosis. These results support the DI approach and suggest that the unique etiologic factors associated with schizophrenia lead to widespread gray matter volume reductions.

Working memory performance inversely predicts spontaneous delta and theta-band scaling relations

Electrophysiological studies have strongly implicated theta-band activity in human working memory processes. Concurrently, work on spontaneous, non-task-related oscillations has revealed the presence of long-range temporal correlations (LRTCs) within sub-bands of the ongoing EEG, and has begun to demonstrate their functional significance. However, few studies have yet assessed the relation of LRTCs (also called scaling relations) to individual differences in cognitive abilities. The present study addressed the intersection of these two literatures by investigating the relation of narrow-band EEG scaling relations to individual differences in working memory ability, with a particular focus on the theta band. Fifty-four healthy adults completed standardized assessments of working memory and separate recordings of their spontaneous, non-task-related EEG. Scaling relations were quantified in each of the five classical EEG frequency bands via the estimation of the Hurst exponent obtained from detrended fluctuation analysis. A multilevel modeling framework was used to characterize the relation of working memory performance to scaling relations as a function of general scalp location in Cartesian space. Overall, results indicated an inverse relationship between both delta and theta scaling relations and working memory ability, which was most prominent at posterior sensors, and was independent of either spatial or individual variability in band-specific power. These findings add to the growing literature demonstrating the relevance of neural LRTCs for understanding brain functioning, and support a construct- and state-dependent view of their functional implications.

Exaggerated reaction to novelty as a subclinical consequence of mild traumatic brain injury.

Abstract Objectives: To evaluate exaggerated reaction to novelty as a behavioural marker of sub-clinical cognitive dysfunction in individuals with a history of mild traumatic brain injury (mTBI). Background and hypothesis: A sub-set of individuals who sustain mTBIs report persistent cognitive difficulties despite normal performance on traditional neuropsychological measures. Evidence of subtle neuroimaging abnormalities following mTBI lends support to such subjective complaints. However, behavioural evidence is limited. This study examined whether behavioural response to task novelty (‘novelty effect’ or NE) is exaggerated in mTBI (NE has previously successfully identified pre-clinical cognitive decline among older adults). It was hypothesized that individuals with a history of mTBI would exhibit increased NE relative to controls, despite normal performance on traditional neuropsychological measures. Methods: Thirty-eight male criminal offenders completed semi-structured interviews of their mTBI and other history, conventional neuropsychological testing and a computerized motor planning task that quantified NE. Results: As expected, participants with a history of mTBI exhibited significantly greater NE, despite no group differences in traditional neuropsychological test performance. A greater number of injuries was positively related to NE magnitude and unrelated to traditional measures. Conclusions: Increased NE indexes sub-clinical sequelae of mTBI and may represent a general marker of mild neurological dysfunction.

Reliable activation to novel stimuli predicts higher fluid intelligence

The ability to reliably respond to stimuli could be an important biological determinant of differences in fluid intelligence (Gf). However, most electrophysiological studies of Gf employ event-related potential (ERP) measures that average brain activity over trials, and hence have limited power to quantify neural variability. Time-frequency analyses can capture cross-trial variation in the phase of neural activity, and thus can help address the importance of neural reliability to differences in Gf. This study recruited a community sample of healthy adults and measured inter-trial phase clustering (ITPC), total spectral power, and ERP amplitudes elicited by Repeated and Novel non-target stimuli during two visual oddball tasks. Condition effects, relations among the EEG measures, and relations with Gf were assessed. Early visual responses to Repeated stimuli elicited higher ITPC, yet only ITPC elicited by Novel stimuli was associated with Gf. Analyses of spectral power further highlighted the contribution of phase consistency to the findings. The link between Gf and reliable responding to changing inputs suggests an important role for flexible resource allocation in fluid intellectual skills.

Developmental instability and markers of schizotypy in university students

Fluctuating asymmetries (FA) and minor physical anomalies (MPAs) are markers of developmental instability (DI), an index of the degree to which an organism was subject to genomic or environmental stress during development. Measures of DI are characteristic of schizophrenia and are thought to reflect an underlying genetic liability for schizophrenia spectrum disorders. Whereas MPAs reflect developmental stress relatively early in the first trimester in utero, skeletal FAs reflect developmental stress throughout the lifespan. Both measures were collected to provide some indication of the associated developmental time course. In addition to DI measures, several psychometric measures of schizotypy were administered in a sample of university students (n = 81). It was hypothesized that increased DI may relate to schizotypal symptoms in a group of healthy undergraduate students. Schizotypy scores were positively correlated with FA, but not MPAs. This finding suggests that DI, as indexed by FA, is important for normal range variation in schizotypal characteristics, just as it is important for normal range variation in intelligence. Second, considered in the context of studies demonstrating that schizophrenia is associated with elevated MPAs, these results suggest that developmental stress likely occurs earlier in development for schizophrenia than schizotypy.

Fluctuating Asymmetry and Individual Variation in Regional Gray and White Matter Volumes: A Voxel-Based Morphometry Study

Composite measures of fluctuating asymmetry (FA) of skeletal features are commonly used to estimate developmental instability (DI), the imprecise expression of developmental design due to perturbations during an individuals growth and maturation. Though many studies have detailed important behavioral correlates of FA, very little is known about its possible neuroanatomical correlates. In this study we obtained structural brain MRI scans from 20 adults and utilized voxel-based morphometry (VBM) to identify specific regions linked to FA. Greater FA predicted greater whole brain white matter volume, and a trend in the same direction was noted for whole brain gray matter volume. Greater FA was associated with significantly greater gray and white matter volumes in discrete brain regions, most prominently in the frontal lobes and in the right cerebral hemisphere. Developmental studies are needed to identify when FA-related brain differences emerge and to elucidate the specific neurobiological mechanisms leading to these differences.

Changes in dimensionality and fractal scaling suggest soft-assembled dynamics in human EEG

Humans are high-dimensional, complex systems consisting of many components that must coordinate in order to perform even the simplest of activities. Many behavioral studies, especially in the movement sciences, have advanced the notion of soft-assembly to describe how systems with many components coordinate to perform specific functions while also exhibiting the potential to re-structure and then perform other functions as task demands change. Consistent with this notion, within cognitive neuroscience it is increasingly accepted that the brain flexibly coordinates the networks needed to cope with changing task demands. However, evaluation of various indices of soft-assembly has so far been absent from neurophysiological research. To begin addressing this gap, we investigated task-related changes in two distinct indices of soft-assembly using the established phenomenon of EEG repetition suppression. In a repetition priming task, we assessed evidence for changes in the correlation dimension and fractal scaling exponents during stimulus-locked event-related potentials, as a function of stimulus onset and familiarity, and relative to spontaneous non-task-related activity. Consistent with predictions derived from soft-assembly, results indicated decreases in dimensionality and increases in fractal scaling exponents from resting to pre-stimulus states and following stimulus onset. However, contrary to predictions, familiarity tended to increase dimensionality estimates. Overall, the findings support the view from soft-assembly that neural dynamics should become increasingly ordered as external task demands increase, and support the broader application of soft-assembly logic in understanding human behavior and electrophysiology.

Intelligence and Uncertainty: Implications of Hierarchical Predictive Processing for the Neuroscience of Cognitive Ability

HighlightsPredictive processing (PP) is a new candidate paradigm for neurobehavioral research.PP has not been applied to the neuroscience of intelligence.PP accommodates key psychometric, neuroanatomical, and electrophysiological results.PP represents a plausible, integrative framework for the neuroscience of intelligence. Abstract Hierarchical predictive processing (PP) has recently emerged as a candidate theoretical paradigm for neurobehavioral research. To date, PP has found support through its success in offering compelling explanations for a number of perceptual, cognitive, and psychiatric phenomena, as well as from accumulating neurophysiological evidence. However, its implications for understanding intelligence and its neural basis have received relatively little attention. The present review outlines the key tenets and evidence for PP, and assesses its implications for intelligence research. It is argued that PP suggests indeterminacy as a unifying principle from which to investigate the cognitive hierarchy and brain‐ability correlations. The resulting framework not only accommodates prominent psychometric models of intelligence, but also incorporates key findings from neuroanatomical and functional activation research, and motivates new predictions via the mechanisms of prediction‐error minimization. Because PP also suggests unique neural signatures of experience‐dependent activity, it may also help clarify environmental contributions to intellectual development. It is concluded that PP represents a plausible, integrative framework that could enhance progress in the neuroscience of intelligence.

MEG in the Presurgical Epilepsy Evaluation

2003). Thus, it is a powerful tool to help understand various aspects of both healthy cognition and neuropathology in the context of presurgical evaluation for medically intractable epilepsy. Below, we review the critical conceptual and practical details of MEG data collection and analysis, and the emerging literature on its role in localization of language and memory functions in presurgical epilepsy evaluations.