Publications by authors named "Adrian B Safati"

5 Publications

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Examining the relationships among adolescent health behaviours, prefrontal function, and academic achievement using fNIRS.

Dev Cogn Neurosci 2021 08 1;50:100983. Epub 2021 Jul 1.

School of Public Health Sciences, University of Waterloo, Waterloo, ON, Canada; Department of Psychology, University of Waterloo, Waterloo, ON, Canada; Centre for Bioengineering and Biotechnology, University of Waterloo, Waterloo, Canada. Electronic address:

Several adolescent health behaviours have been hypothesized to improve academic performance via their beneficial impact on cognitive control and functional aspects of the prefrontal cortex (PFC). The primary objective of this study is to examine the association between lifestyle behaviours and academic performance in a sample of adolescents, and to examine the extent to which activity within the PFC and behavioural indices of inhibition may mediate this relationship. Sixty-seven adolescents underwent two study sessions five days apart. Sleep and physical activity were measured using wrist-mounted accelerometry; eating habits, substance use and academic achievement were measured by self-report. Prefrontal function was quantified by Multi-Source Interference Task (MSIT) performance, and task-related activity via functional near-infrared spectroscopy (fNIRS). Higher levels of physical activity predicted higher MSIT accuracy scores (β = .321, ρ = 0.019) as well as greater activation within the right dlPFC (b = .008, SE = .004, ρ = .0322). Frequency of fast-food consumption and substance use were negatively associated with MSIT accuracy scores (β = -0.307, ρ = .023) and Math grades (b = -3.702, SE = 1.563, ρ = .022), respectively. Overall, the results of this study highlight the importance of lifestyle behaviours as predictors of prefrontal function and academic achievement in youth.
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August 2021

Contextual cues as modifiers of cTBS effects on indulgent eating.

Brain Stimul 2019 Sep - Oct;12(5):1253-1260. Epub 2019 May 6.

Prevention Neuroscience Laboratory, School of Public Health & Health Systems, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada. Electronic address:

Background: Prior studies have found that continuous theta burst stimulation (cTBS) targeting the left dlPFC results in reliable increases in consumption of calorie-dense food items. However, it is not known to what extent such effects are modified by cues in the immediate eating environment. Tempting environments (i.e., those saturated with appetitive eating cues) may lead to more reliance on cognitive control networks involving the dlPFC, thereby enhancing cTBS effects on indulgent eating.

Objective/hypothesis: The objective was to examine the extent to which cTBS effects on indulgent eating would be modified by contextual cues. It was hypothesized that cTBS effects would be stronger in the presence of facilitating cues.

Methods: Using a single-blinded between-subjects factorial design, 107 TMS-naïve adults were randomly assigned to one of four conditions: 1) active cTBS + facilitating cues, 2) sham cTBS + facilitating cues, 3) active cTBS + inhibiting cues, 4) sham cTBS + inhibiting cues. Following stimulation participants completed a flanker paradigm and a taste test during which quantity consumed was assessed surreptitiously.

Results: Findings revealed a significant interaction between stimulation and cue type (F(1,102) = 6.235, p = .014), such that cTBS resulted in increased food consumption (compared to sham) in the presence of the facilitating cue but not in the presence of the inhibiting cue. Moderated mediational analyses showed selective mediation of cTBS effects on consumption through cTBS attenuation of flanker interference scores.

Conclusions: The effects of cTBS on indulgent eating are strengthened in the presence of facilitating cues. Methodologically speaking, facilitating cues may be a functional prerequisite for exploring cTBS effects on eating in the laboratory. Substantively, the findings also suggest that facilitating cues in the eating environment may amplify counter-intentional food indulgence in everyday life via cognitive control failure.
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January 2020

Effects of left dlPFC modulation on social cognitive processes following food sampling.

Appetite 2018 07 27;126:73-79. Epub 2018 Mar 27.

Western University and Parkwood Institute-Mental Health, Canada.

Background: The dorsolateral prefrontal cortex (dlPFC) plays a central role in the inhibition of eating, but also the modulation of conscious thought processes that might precede, accompany or follow initial food tasting. The latter might be particularly important to the extent that post-tasting cognitions may drive prolonged eating beyond the satiety point. However, we know very little about the effect of the dlPFC on conation following initial food sampling. This investigation compared the effects of dlPFC attenuation using repetitive transcranial magnetic stimulation (rTMS) on social cognition following (Study 1) and prior to (Study 2) a food consumption opportunity.

Methods: In Study 1, participants (N = 21; M = 21 years) were randomized to active or sham continuous theta-burst stimulation (cTBS; an inhibitory variant of rTMS) targeting the left dlPFC followed by an interference task. Participants subsequently completed measures of attitudes, norms and perceived control following a mock taste test. In Study 2, a second sample of right handed participants (N = 37; M = 21 years) were assigned to active or sham cTBS, followed by an interference task and two measures of attitudes (implicit and explicit), both assessed prior to the same taste test paradigm.

Results: In Study 1, findings revealed a reliable effect of cTBS on post-tasting attitudes (t(1,19) = 3.055, p = .007; d = 1.34), such that attitudes towards calorie dense snack foods were significantly more positive following active stimulation than following sham stimulation. Similar effects were found for social norms (t(1,19) = 3.024, p = .007, d = 1.31) and perceived control (t(1,20) = 19.247, p < .001, d = 0.50). In Study 2, no effects of cTBS were observed on pre-consumption attitudes, despite reliable effects on interference scores and subsequent consumption.

Conclusions: The left dlPFC may selectively modulate facilitative social cognition following initial food sampling (but not pre-consumption).
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July 2018

The effects of theta burst stimulation (TBS) targeting the prefrontal cortex on executive functioning: A systematic review and meta-analysis.

Neuropsychologia 2018 03 10;111:344-359. Epub 2018 Feb 10.

Prevention Neuroscience Lab, School of Public Health and Health Systems, University of Waterloo, Waterloo, ON, Canada N2L 3G1. Electronic address:

Theta burst stimulation (TBS) is a highly efficient repetitive transcranial magnetic stimulation (rTMS) variant employed in experimental and clinical treatment paradigms. Despite widespread usage of TBS targeting the prefrontal cortex (PFC), there has been no systematic review of the evidence linking TBS protocols to changes in task performance on common measures of prefrontal function in general, and executive functions specifically. A systematic review of the literature was conducted using PsycINFO, PubMed, Web of Science and Scopus databases to identify articles examining the effects of TBS targeting the PFC on executive function task performance. Both the up-regulating (intermittent theta burst stimulation; iTBS) and down-regulating (continuous theta burst stimulation; cTBS) variants of TBS were considered. 32 (29 cTBS; 8 iTBS) studies met the inclusion criteria. Participants (n = 759; 51.41% female) were primarily young adults (M = 26), with one study examining the effects of cTBS and iTBS in older adults. Results from individual studies were converted to Hedge's g and random-effects models were used to estimate the overall effect size for each protocol. Age, biological sex, and control methodology were examined as potential moderators of the cTBS effect on executive function test performance. Findings indicated a- reliable attentuating effect of cTBS on executive function task performance (g = -.244, Z = -5.920, p < .001); this effect was relatively uniform across included studies (Q= 24.178, p = .838, I = 0). Although no significant moderators of the cTBS effect were identified, laterality sub analyses indicated that the magnitude of the effect was significantly higher (M = .213, Z = 2.546, p = .011) for left-sided (g = -.358, Z = -5.816, p < .001) relative to right-sided (g = -.145, Z = -2.552, p = .011) PFC stimulation. A systematic review of iTBS studies revealed variability in reliability of effects though most were in the theorized direction. TBS protocols appear to be effective in modulating prefrontal cortical excitability in previously theorized directions.
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March 2018