Dylan Smith

Dylan Smith
  • PhD
  • PostDoc Position at University of Ottawa

About

46
Publications
7,777
Reads
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874
Citations
Current institution
University of Ottawa
Current position
  • PostDoc Position
Additional affiliations
May 2010 - August 2015
University of Ottawa
Position
  • PhD Student
January 2012 - present

Publications

Publications (46)
Article
Sleep consolidates procedural memory for motor skills, and this process is associated with strengthened functional connectivity in hippocampal–striatal–cortical areas. It is unknown whether similar processes occur for procedural memory that requires cognitive strategies needed for problem-solving. It is also unclear whether a full night of sleep is...
Article
Full-text available
Spindles are often temporally coupled to slow waves (SW). These SW-spindle complexes have been implicated in memory consolidation that involves transfer of information from the hippocampus to the neocortex. However, spindles and SW, which are characteristic of NREM sleep, can occur as part of this complex, or in isolation. It is not clear whether d...
Article
Full-text available
Objectives Chronotype impacts our state at a given time of day, however, chronotype is also heritable, trait-like, and varies systematically as a function of age and sex. However, only a handful of studies support a relationship between chronotype and trait-like cognitive abilities (i.e., intelligence), and the evidence is sparse and inconsistent b...
Article
Introduction Sleep consolidates memory, including newly acquired procedural skills. One putative systems-level mechanism for this function of sleep is via sleep-dependent strengthening of functional connectivity between the putamen and the cortico-hippocampal-striatal-cerebellar network, which supports procedural motor skills. For procedural motor...
Article
Introduction Older adults do not consolidate newly learned motor sequences with the same efficiency compared to younger adults, and there is evidence that enhanced consolidation by sleep is also impaired with age. It is known that brain activity in the hippocampal-cortical-striatal network is important for off-line consolidation of motor-sequences,...
Article
Full-text available
RationaleThe combination of CDP-choline, an α7 nicotinic acetylcholine receptor (α7 nAChR) agonist, with galantamine, a positive allosteric modulator of nAChRs, is believed to counter the fast desensitization rate of the α7 nAChRs and may be of interest for schizophrenia (SCZ) patients. Beyond the positive and negative clinical symptoms, deficits i...
Article
There is much evidence that sleep is important for maintaining optimal cognition in humans; however, the link between cognitive capabilities and specific brain activity during sleep is less clear. Recently, converging evidence suggests that brain activity during sleep is linked to interindividual differences in intellectual abilities. In particular...
Article
There is a growing need for optimizing treatment selection and response prediction in individuals with major depressive disorder (MDD). Prior investigations have shown that changes in electroencephalographic (EEG)-based measures precede symptom improvement and could serve as biomarkers of treatment outcome. One such method is cordance, a computatio...
Chapter
While the neuroscience of sleep has traditionally been studied using electroencephalography (EEG), newer technologies have allowed for an enriched understanding of the brain’s ongoing activity during transitions into sleep, as well as during the distinct stages of sleep observed in humans. Neuroimaging techniques such as magnetic resonance imaging...
Article
Full-text available
EEG studies have shown that interindividual differences in the electrophysiological properties of sleep spindles (e.g., density, amplitude, duration) are highly correlated with trait-like “reasoning” abilities (i.e., “fluid intelligence”; problem-solving skills; the ability to employ logic or identify complex patterns), but not interindividual diff...
Article
The high prevalence of concomitant cannabis and nicotine use has implications for sensory and cognitive processing. While nicotine tends to enhance function in these domains, cannabis use has been associated with both sensory and cognitive impairments, though the underlying mechanisms are unclear. Additionally, the interaction of the nicotinic (nAC...
Article
Background: Schizophrenia (SCZ) patients and relatives have deficits in early cortical sensory gating (SG) typically measured by suppression of electroencephalography-derived P50 event-related potentials (ERPs) in a conditioning-testing (S1-S2) paradigm. Associated with alpha 7 nicotinic acetylcholine receptor (α7 nAChR) dysfunction and shown to b...
Article
Neuralα7 nicotinic acetylcholine receptor (nAChR) expression and functioning deficits have been extensively associated with cognitive and early sensory gating (SG) impairments in schizophrenia (SCZ) patients and their relatives. SG, the suppression of irrelevant and redundant stimuli, is measured in a conditioning-testing (S1-S2) paradigm eliciting...
Article
Growing evidence supports the use of cognitive behavioural therapy (CBT) for psychosis, including CBT for voices (CBTv), which targets auditory verbal hallucinations (AVH). The present study observed the effects of CBTv on electrophysiological measures of facial expression processing in patients with schizophrenia with AVH. Twenty-five patients wit...
Article
Objective The effects of GABA modulating drugs and nicotine, the prototypical nicotinic cholinergic agonist, on attention have been investigated using subcomponents of the P300 event‐related potentials (ERP), which index involuntary (P3a) and voluntary attention (P3b). However, investigations into how such pharmacologic effects interact with geneti...
Article
Full-text available
Objective: Evidence relying on probe detection tasks suggests that anxious individuals exhibit an enhanced selective attentional bias toward emotional or threating stimuli, characterized by attentional vigilance or avoidance of threat. Method: Amplitude of P100 and P300 event-related potentials and behavioral measures of target detection were as...
Chapter
Sleep is composed of two main stages, Rapid Eye Movement (REM) sleep and non-REM sleep, each of them generated by specific cerebral networks. REM sleep is the behavioral state that produces the greatest recall and intensity of dreaming. Moreover, correlations between functional patterns of brain activity during REM sleep and specific properties of...
Data
Multiscale entropy (MSE) - Montgomery-Åsberg Depression Rating (MADRS) change score correlations with linear fits. MSE-MADRS change score scatterplots for responders (A) and non-responders (B) at electrode Pz at 30 ms (i.e., coarse temporal scale with highest bootstrap ratio). We identify participants in different antidepressant regimens by colour:...
Article
Full-text available
Background Previous work suggests that major depressive disorder (MDD) is associated with disturbances in global connectivity among brain regions, as well as local connectivity within regions. However, the relative importance of these global versus local changes for successful antidepressant treatment is unknown. We used multiscale entropy (MSE), a...
Conference Paper
Abstract Introduction: While the high prevalence of concomitant cannabis and nicotine use in schizophrenia (SZ) has been viewed as a form of self-medication for cognitive and stress/emotional processing, the interaction of these substances has received limited study in terms of sensory/cognitive processes. The objective of this study was to assess...
Article
Full-text available
Background: Quantitative electroencephalogram (EEG) is one neuroimaging technique that has been shown to differentiate patients with major depressive disorder (MDD) and non-depressed healthy volunteers (HV) at the group-level, but its diagnostic potential for detecting differences at the individual level has yet to be realized. Quantitative EEGs p...
Article
Full-text available
Background Alpha 7 nicotinic acetylcholine receptors (α7 nAChR) are prioritized molecular targets for the development of new pharmacological treatments for impaired cognition in schizophrenia. The use of schizophrenia-associated biomarkers both as endpoints and for segmentation of homogeneous populations for early detection of cognitive enhancing a...
Article
While nicotine is often associated with the neuropsychological effects of tobacco smoke, the robust monoamine oxidase (MAO) inhibition observed in chronic smokers is also likely to play a role. Electroencephalographically-indexed alterations in baseline neural oscillations by nicotine have previously been reported in both smokers and non-smokers, h...
Article
The Mismatch Negativity (MMN) auditory event-related potential (ERP) has been extensively studied as a potential biomarker for abnormal auditory processing in schizophrenia (SZ), a population which exhibits abnormally high smoking rates. The relationship between nicotinic activation and cognition in SZ may be related to underlying nicotinic and NMD...
Article
Performance improvements in cognitive tasks requiring executive functions are evident with nicotinic acetylcholine receptor (nAChR) agonists and activation of the underlying neural circuitry supporting these cognitive effects is thought to involve dopamine neurotransmission. As individual difference in response to nicotine may be related to a funct...
Article
CDP-choline (cytidine-5'-diphosphocholine) is a phospholipid used to treat cognitive disorders, presumably repairing and maintaining brain cell membranes. Additional mechanisms may include enhanced cholinergic neurotransmission as the α7 nicotinic receptor actions of choline and increased acetylcholine synthesis accompanying CDP-choline administrat...
Article
Novel pharmacological treatments targeting alpha 7 nicotinic acetylcholine receptor (α7 nAChR) hypofunction in schizophrenia have shown mixed success in ameliorating cognitive impairments associated with this disorder. Choline, a selective agonist at α7 receptors is increased with oral administration of cytidine 5'-diphosphocholine (CDP-choline), t...
Article
The cognitive effects of nicotine in humans remain a topic of great interest, due to the continued prevalence of cigarette smoking in society as well as the hypothesis that cognitively impaired populations such as schizophrenia patients use nicotine as a means of self-medicating against deficits of sensory gating. However, chronic smoking can predi...
Article
Diminished auditory sensory gating and associated neurocognitive deficits in schizophrenia have been linked to altered expression and function of the alpha-7 nicotinic acetycholinergic receptor (α7 nAChR), the targeting of which may have treatment potential. Choline is a selective α7 nAChR agonist and the aim of this study was to determine whether...
Article
Objective Cognitive enhancement resulting from nicotinic acetylcholine receptor stimulation may be evidenced by increased efficiency of the auditory-frontal cortex network of auditory discrimination, which is impaired in schizophrenia, a cognitive disorder associated with excessive tobacco use. Investigating automatic (preattentive) detection of ac...
Article
Full-text available
Previous research has suggested that auditory hallucinations (AH) may alter basic auditory perceptual processes. The primary objective of this study was to examine measures of early auditory feature analysis, including the mismatch negativity (MMN) and novelty P300 (NP3) in hallucinating schizophrenia patients (SZ) during an acute psychotic episode...
Article
Cholinergic stimulation produces cognitive effects that vary across individuals, and stimulus/task conditions. As of yet, the role of individual differences in moderating the effects of the nicotinic acetylcholine receptor agonist nicotine on specific attentional functions and their neural and behavioural correlates is not fully understood. In this...
Article
Evidence from visual probe detection tasks suggests that anxious individuals exhibit biased (enhanced) selective attention to threat stimuli, such as angry and fearful faces. Attentional bias to threatening stimuli has been characterized by (1) facilitated attention to stimuli (vigilance), (2) difficulty disengaging attention away from stimuli, or...
Article
Reduced suppression of the P50 auditory event-related potential in schizophrenia patients relative to normal controls is indicative of a sensory gating deficit and is one of the most robust findings reported for functional brain abnormalities in this disorder. However, there is considerable gating variability in patients and controls and there is l...
Article
Event-related potentials (ERPs), derived from electroencephalographic (EEG) recordings, can index electrocortical activity related to cognitive operations. The fronto-central P3a ERP is involved in involuntary processing of novel auditory information, whereas the parietal P3b indexes controlled attention processing. The amplitude of the auditory P3...
Article
Elevated smoking rates seen in schizophrenia populations may be an attempt to correct neuropathologies associated with deficient nicotinic acetylcholine receptors and/or dopaminergic systems using exogenous nicotine. However, nicotine's effects on cognitive processing and sensory gating have been shown to be baseline-dependent. Evidence of a restor...
Article
Objective: While auditory verbal hallucinations (AVHs) are a common symptom of schizophrenia, the underlying mechanisms behind these perceptual anomalies and their effects on auditory processing are not fully understood. Patients suffering from schizophrenia have been shown to exhibit impaired sensory gating of acoustic stimuli, evidenced by a fai...
Article
Elevated smoking rates have been noted in schizophrenia, and it has been hypothetically attributed to nicotine's ameliorating abnormal brain processes in this illness. There is some preliminary evidence that nicotine may alter pre-attentive auditory change detection, as indexed by the EEG-derived mismatch negativity (MMN), but no previous study has...
Article
The recently developed Optimal-3 multi-feature MMN paradigm, a shortened version of the 'optimal' multi-feature MMN paradigm, allows for the focused recording of the most widely reported MMN deviants (frequency, duration, intensity) within an efficient and time-saving paradigm. The objective of this study was to examine MMN acoustic change detectio...
Article
The introduction of the multi-feature 'optimal' mismatch negativity (MMN) paradigm was a significant innovation that allows for the collection of MMNs from five different deviant types in a relatively short period of time. Given the very specific stimulus presentation structure of this paradigm, the deletion of deviants results in an increase in th...
Article
Although schizophrenia has been considered primarily a disease of dopaminergic neurotransmission, the role of dopamine in auditory sensory gating deficits in this disorder and their amelioration by smoking/nicotine is unclear. Hypothesizing that individual differences in striatal dopamine levels may moderate auditory gating and its modulation by ni...

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