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Author: Scott Mackey (23)


Nov
2017

Neuroimaging studies of attention-deficit/hyperactivity disorder (ADHD) have most commonly reported volumetric abnormalities in the basal ganglia, cerebellum, and prefrontal cortices. Few studies have examined the relationship between ADHD symptomatology and brain structure in population-based samples. We investigated the relationship between dimensional measures of ADHD symptomatology, brain structure, and reaction time variability-an index of lapses in attention.

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Aug
2017

Individual differences in impulsivity and early adversity are known to be strong predictors of adolescent antisocial behavior. However, the neurobiological bases of impulsivity and their relation to antisocial behavior and adversity are poorly understood.
Impulsivity was estimated with a temporal discounting task.

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Dec
1969

Since the sample size of a typical neuroimaging study lacks sufficient statistical power to explore unknown genomic associations with brain phenotypes, several international genetic imaging consortia have been organized in recent years to pool data across sites. The challenges and achievements of these consortia are considered here with the goal of leveraging these resources to study addiction. The authors of this review have joined together to form an Addiction working group within the framework of the ENIGMA project, a meta-analytic approach to multisite genetic imaging data.

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Apr
2016

[11C]-dihydrotetrabenazine (DTBZ) Positron Emission Tomography was used to evaluate the vesicular monoamine transporter type 2 as an index of dopaminergic function in the striatum of adult Sprague-Dawley rats obtained from two different animal sources (Charles River Laboratories [CR] or UBC's Animal Care Centre [ACC]) and later submitted to two different unilateral lesions of the nigro-striatal pathway. The results showed a significant difference in the striatal binding potential (BP(ND)) at baseline (before lesioning) between the CR and ACC groups providing evidence that the origin of the animals, possibly due to differences in early environmental factors or breeding conditions associated with different animal vendors plays a role in the development of the adult dopaminergic system. Further, in both animal models, an increase in DTBZ BP(ND) was observed, after unilateral intervention, in the striatum contralateral to the lesion, likely reflecting compensatory effects.

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Dec
1969

Understanding how humans weigh long-term and short-term goals is important for both basic cognitive science and clinical neuroscience, as substance users need to balance the appeal of an immediate high vs. the long-term goal of sobriety. We use a computational model to identify learning and decision-making abnormalities in methamphetamine-dependent individuals (MDI, n = 16) vs.

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Dec
2015

Cannabis use in adolescence may be characterized by differences in the neural basis of affective processing. In this study, we used an fMRI affective face processing task to compare a large group (n=70) of 14-year olds with a history of cannabis use to a group (n=70) of never-using controls matched on numerous characteristics including IQ, SES, alcohol and cigarette use. The task contained short movies displaying angry and neutral faces.

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Sep
2016

The significance of why a similar set of brain regions are associated with the default mode network and value-related neural processes remains to be clarified. Here, we examined i) whether brain regions exhibiting willingness-to-pay (WTP) task-related activity are intrinsically connected when the brain is at rest, ii) whether these regions overlap spatially with the default mode network, and iii) whether individual differences in choice behavior during the WTP task are reflected in functional brain connectivity at rest. Blood-oxygen-level dependent (BOLD) signal was measured by functional magnetic resonance imaging while subjects performed the WTP task and at rest with eyes open.

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Dec
1969

According to embodied cognition theories, concepts are contextually situated and grounded in neural systems that produce experiential states. This view predicts that processing mental state concepts recruits neural regions associated with different aspects of experience depending on the context in which people understand a concept. This neuroimaging study tested this prediction using a set of sentences that described emotional (e.

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Sep
2014

A previous report identified the location of comparable architectonic areas in the ventral frontal cortex of the human and macaque brains [S. Mackey & M. Petrides (2010) Eur.

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Sep
2014

The purpose of this study was to assess osseous parameters and stability of maxillary anterior teeth following crown lengthening surgery. Thirty-six patients requiring facial crown lengthening of 277 maxillary anterior and first premolar teeth were included. Presurgical and intraoperative clinical measurements were recorded at baseline and 1, 3, and 6 months postsurgery at midfacial, mesiofacial, and distofacial line angles.

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Feb
2014

Although the interaction of brain volume with amphetamine-type stimulants (ATS) and cocaine has been investigated in chronically dependent individuals, little is known about structural differences that might exist in individuals who consume ATS and cocaine occasionally but are not dependent on these drugs.
Regional brain volumes in 165 college aged occasional users of ATS (namely: amphetamine, methamphetamine, methylphenidate, and 3,4-methylenedioxymethamphetamine; MDMA) and cocaine were compared by voxel-based morphometry with 48 ATS/cocaine-naive controls.
Grey matter volume was significantly higher in the left ventral anterior putamen of occasional users, and lower in the right dorsolateral cerebellum and right inferior parietal cortex.

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Apr
2014

In the human brain, areas 44 and 45 constitute Broca's region, the ventrolateral frontal region critical for language production. The homologues of these areas in the macaque monkey brain have been established by direct cytoarchitectonic comparison with the human brain. The cortical areas that project monosynaptically to areas 44 and 45B in the macaque monkey brain require clarification.

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Sep
2013

Substance use disorders (SUDs) can be conceptualized as a form of risk-taking behavior with the potential for highly aversive outcomes such as health or legal problems. Risky decision-making likely draws upon several related brain processes involved in estimations of value and risk, executive control, and emotional processing. SUDs may result from a dysfunction in one or more of these cognitive processes.

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Sep
2013

Several independent lines of research suggest that disruption of the ubiquitin proteasome system (UPS) may play a role in the pathophysiology of Parkinson's disease. Direct intracerebral injection of UPS inhibitors (e.g.

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Mar
2013

While a large number of studies have examined brain volume differences associated with cocaine use, much less is known about structural differences related to amphetamine-type stimulant (ATS) use. What is known about cocaine may help to interpret emerging information on the interaction of brain volume with ATS consumption. To date, volumetric studies on the two types of stimulant have focused almost exclusively on brain differences associated with chronic use.

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Dec
2010

The orbital and ventromedial frontal cortical regions of the human and the macaque monkey brains include several spatially discrete areas which are defined histologically by their distinctive laminar architecture. Although considerable information has been collected on the function and anatomical connections of specific architectonic areas within the orbital and ventromedial frontal cortex of the macaque monkey, the location of comparable areas in the human brain remains controversial. We re-examined the comparability of orbital and ventromedial frontal areas across these two species and provide the first quantitative demonstration of architectonically comparable cortical areas in the human and the macaque brains.

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Apr
2010

The botryoid odontogenic cyst (BOC) is a multicompartmentalized variant of the lateral periodontal cyst (LPC) that is typically found in the premolar-canine region of the mandible.
A 60-year old man was referred for evaluation of a radiolucent lesion discovered on a routine examination. Radiographs revealed a unilocular radiolucency between the roots of teeth #10 and #11.

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Jun
2009

Platelet-rich plasma (PRP) has been promoted as a surgical adjunct to enhance hard and soft tissue wound healing. Although anecdotally reported to be of value, the results of controlled studies examining the added effects of PRP on surgical procedures have been mixed. The purpose of this study was to test the effect of PRP on flap strength at various post-surgical time points in a minipig animal model.

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Jun
2005

In the ventrolateral frontal lobe of the human brain there is a distinct entity, cytoarchitectonic area 44 (Broca's area), which is crucial in speech production. There has been controversy over whether monkeys possess an area comparable to human area 44. We have addressed this question in the macaque monkey by combining quantitative architectonic analysis of the cortical areas within the ventrolateral frontal region with electrophysiological recording of neuron activity and electrical intracortical microstimulation.

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Nov
2004

With the advent of magnetic resonance imaging (MRI), it is possible to obtain high-resolution anatomical images of the monkey brain. Accuracy, however, is lost in the laboratory or surgical setting when the localization of brain structures depends on nonstereotaxic tracking methods. Here we present an image-guided stereotaxic system that is able to localize and access anatomical brain structures using the monkey's MRI.

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Dec
1969

The predictability and success of endosseous dental implants has secured their place as a standard treatment modality. Nevertheless, a small number of implants will fail regardless of operator experience or clinically recognizable cause. This article presents two cases of early failure of two-stage dental implants manifesting in a spontaneous and rapid exfoliation.

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