Publications by authors named "Brandie M Stewart"

6 Publications

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Neural correlates of the production effect: An fMRI study.

Brain Cogn 2021 Jun 12;152:105757. Epub 2021 Jun 12.

Memorial University of Newfoundland, Department of Psychology, St. John's, NL A1B 3X9, Canada. Electronic address:

Recognition memory is improved for items produced at study (e.g., by reading them aloud) relative to a non-produced control condition (e.g., silent reading). This production effect is typically attributed to the extra elements in the production task (e.g., motor activation, auditory perception) enhancing item distinctiveness. To evaluate this claim, the present study examined the neural mechanisms underlying the production effect. Prior to a recognition memory test, different words within a study list were read either aloud, silently, or while saying "check" (as a sensorimotor control condition). Production improved recognition, and aloud words yielded higher rates of both recollection and familiarity judgments than either silent or control words. During encoding, fMRI revealed stronger activation in regions associated with motor, somatosensory, and auditory processing for aloud items than for either silent or control items. These activations were predictive of recollective success for aloud items at test. Together, our findings are compatible with a distinctiveness-based account of the production effect, while also pointing to the possible role of other processing differences during the aloud trials as compared to silent and control.
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http://dx.doi.org/10.1016/j.bandc.2021.105757DOI Listing
June 2021

Do emotion-induced blindness and the attentional blink share underlying mechanisms? An event-related potential study of emotionally-arousing words.

Cogn Affect Behav Neurosci 2017 06;17(3):592-611

Department of Psychology, Brock University, 500 Glenridge Avenue, St. Catharines, ON, L2S 3A1, Canada.

When two targets are presented within approximately 500 ms of each other in the context of rapid serial visual presentation (RSVP), participants' ability to report the second target is reduced compared to when the targets are presented further apart in time. This phenomenon is known as the attentional blink (AB). The AB is increased in magnitude when the first target is emotionally arousing. Emotionally arousing stimuli can also capture attention and create an AB-like effect even when these stimuli are presented as to-be-ignored distractor items in a single-target RSVP task. This phenomenon is known as emotion-induced blindness (EIB). The phenomenological similarity in the behavioral results associated with the AB with an emotional T1 and EIB suggest that these effects may result from similar underlying mechanisms - a hypothesis that we tested using event-related electrical brain potentials (ERPs). Behavioral results replicated those reported previously, demonstrating an enhanced AB following an emotionally arousing target and a clear EIB effect. In both paradigms highly arousing taboo/sexual words resulted in an increased early posterior negativity (EPN) component that has been suggested to represent early semantic activation and selection for further processing in working memory. In both paradigms taboo/sexual words also produced an increased late positive potential (LPP) component that has been suggested to represent consolidation of a stimulus in working memory. Therefore, ERP results provide evidence that the EIB and emotion-enhanced AB effects share a common underlying mechanism.
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http://dx.doi.org/10.3758/s13415-017-0499-7DOI Listing
June 2017

Rapid Automatic Motor Encoding of Competing Reach Options.

Cell Rep 2017 02;18(7):1619-1626

Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada; Department of Psychology, Queen's University, Kingston, ON K7L 3N6, Canada. Electronic address:

Mounting neural evidence suggests that, in situations in which there are multiple potential targets for action, the brain prepares, in parallel, competing movements associated with these targets, prior to implementing one of them. Central to this interpretation is the idea that competing viewed targets, prior to selection, are rapidly and automatically transformed into corresponding motor representations. Here, by applying target-specific, gradual visuomotor rotations and dissociating, unbeknownst to participants, the visual direction of potential targets from the direction of the movements required to reach the same targets, we provide direct evidence for this provocative idea. Our results offer strong empirical support for theories suggesting that competing action options are automatically represented in terms of the movements required to attain them. The rapid motor encoding of potential targets may support the fast optimization of motor costs under conditions of target uncertainty and allow the motor system to inform decisions about target selection.
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http://dx.doi.org/10.1016/j.celrep.2017.01.049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6103432PMC
February 2017

Motor, not visual, encoding of potential reach targets.

Curr Biol 2014 Oct;24(19):R953-4

Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada K7L 3N6; Department of Psychology, Queen's University, Kingston, Ontario, Canada K7L 3N6. Electronic address:

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http://dx.doi.org/10.1016/j.cub.2014.08.046DOI Listing
October 2014

Simultaneous encoding of the direction and orientation of potential targets during reach planning: evidence of multiple competing reach plans.

J Neurophysiol 2013 Aug 22;110(4):807-16. Epub 2013 May 22.

Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.

Reaches performed in many natural situations involve selecting a specific target from a number of alternatives. Recent studies show that before reaching, multiple potential reach targets are encoded in brain regions involved in action control and that, when people are required to initiate the reach before the target is specified, initial hand direction is biased by the spatial distribution of potential targets. These findings have led to the suggestion that the brain, during planning, simultaneously prepares multiple reaches to potential targets. In addition to hand direction, reach planning often involves specifying other parameters such as wrist orientation. For example, when posting a letter in a mail slot, both the location and orientation of the slot must be encoded to control hand direction and orientation. Therefore, if the brain prepares multiple reaches to potential targets and if these targets require the specification of hand direction and orientation, then both of these variables should be biased by the spatial distribution of potential targets. To test this prediction, we examined a task in which participants moved a hand-held rectangular tool toward multiple rectangular targets of varying location and orientation, one of which was selected, with equal probability as the actual target after movement initiation. We found that initial hand direction and orientation were biased by the spatial distributions of potential target locations and orientations, respectively. This result is consistent with the idea that the brain, in cases of target uncertainty, simultaneously plans fully specified reaching movements to all potential targets.
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http://dx.doi.org/10.1152/jn.00131.2013DOI Listing
August 2013