Publications by authors named "Daniel J Fehring"

Article Synopsis
  • Transcranial direct current stimulation (tDCS) shows promise for improving cognitive functions and treating cognitive disorders, but variable outcomes raise concerns about its safety and effectiveness due to unclear neural mechanisms.
  • The study investigates tDCS effects on macaque monkeys' cognitive abilities and neuron activity, revealing that tDCS reduced practice-related response slowdowns and altered neuron firing patterns compared to sham stimulation.
  • After tDCS, changes in behavior and neuron activity were observed to persist, indicating potential lasting effects, but tDCS did not significantly alter baseline neuron firing rates across multiple applications.
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Humans demonstrate significant behavioural advantages with particular perceptual dimensions (such as colour or shape) and when the relevant dimension is repeated in consecutive trials. These dimension-related behavioural modulations are significantly altered in neuropsychological and addiction disorders; however, their underlying mechanisms remain unclear. Here, we studied whether these behavioural modulations exist in other trichromatic primate species and whether repeated exposure to opioids influences them.

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Auditory stimuli, encompassing a continually expanding collection of musical genres and sonic hues, present a safe and easily administrable therapeutic option for alleviating cognitive deficits associated with neuropsychological disorders, but their effects on executive control are yet to be completely understood. To better understand how the processing of certain acoustic properties can influence conflict processing, we had a large of cohort of undergraduate students complete the Stroop colour and word test in three different background conditions: classical music, white noise, and silence. Because of pandemic guidelines and the necessity to run the experiment remotely, participants also completed the Wisconsin card sorting test (WCST), so that the reliability and consistency of acquired data could be assessed.

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Humans demonstrate behavioural advantages (biases) towards particular dimensions (colour or shape of visual objects), but such biases are significantly altered in neuropsychological disorders. Recent studies have shown that lesions in the prefrontal cortex do not abolish dimensional biases, and therefore suggest that such biases might not depend on top-down prefrontal-mediated attention and instead emerge as bottom-up processing advantages. We hypothesised that if dimensional biases merely emerge from an enhancement of object features, the presence of visual objects would be necessary for the manifestation of dimensional biases.

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Context-dependent execution or inhibition of a response is an important aspect of executive control, which is impaired in neuropsychological and addiction disorders. Transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC) has been considered a remedial approach to address deficits in response control; however, considerable variability has been observed in tDCS effects. These variabilities might be related to contextual differences such as background visual-auditory stimuli or subjects' sex.

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The number of studies investigating sex differences in executive functions, particularly those using human functional neuroimaging techniques, has risen dramatically in the past decade. However, the influences of sex on executive function are still underexplored and poorly characterized. To address this, we conducted a systematic literature review of functional neuroimaging studies investigating sex differences in three prominent executive control domains of cognitive set-shifting, performance monitoring, and response inhibition.

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Literature investigating whether an individuals' sex affects their executive control abilities and performance on cognitive tasks in a normative population has been contradictory and inconclusive. Using meta-analytic procedures (abiding by PRISMA guidelines), this study attempts to identify the magnitude of behavioural sex differences in three prominent executive control domains of cognitive set-shifting, performance monitoring, and response inhibition. PubMed, Web of Science, and Scopus were systematically searched.

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In our daily life, we frequently need to make decisions between competing behavioral options while we are exposed to various contextual factors containing emotional/social information. We examined how changes in emotional/arousal state influence resolving conflict between behavioral rules. Visual stimuli with emotional content (positive, negative and neutral) and music (High/Low tempo), which could potentially alter emotional/arousal states, were included in the task context while participants performed the Wisconsin Card Sorting Test (WCST).

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Article Synopsis
  • Imaging studies show the primate prefrontal cortex is activated when shifting attention between visual dimensions, raising questions about whether this process is driven by top-down (prefrontal) or bottom-up (visual cortex) mechanisms.
  • Research comparing humans and macaque monkeys reveals that while both species can shift attention between dimensions, they exhibit biases in opposite directions—humans favor color whereas monkeys favor shape.
  • Selective lesions in certain prefrontal areas hinder monkeys' ability to shift dimensions, suggesting that while top-down control from the prefrontal cortex is essential for goal-directed behavior, the representation of visual dimensions and bias can occur independently from it.
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The effects of transcranial direct-current stimulation (tDCS) on cognitive functions, such as response inhibition, might be mediated through plastic changes within the prefrontal cortex. Previous studies have also confirmed learning-related plasticity in prefrontal neurocircuitry. The susceptibility of prefrontal neurocircuitry for tDCS-induced plastic changes and consequent behavioural modulations might depend on the level of learning in a particular task.

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Influential hypotheses propose that alterations in emotional state influence decision processes and executive control of behavior. Both music and transcranial direct current stimulation (tDCS) of prefrontal cortex affect emotional state, however interactive effects of music and tDCS on executive functions remain unknown. Learning to inhibit inappropriate responses is an important aspect of executive control which is guided by assessing the decision outcomes such as errors.

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Commission of errors and conflict between choices might induce behavioral modulations through adjustments in the executive control of behavior and altered patterns of these modulations are detected in neuropsychiatric disorders. We examined the effects of transcranial Direct Current Stimulation (tDCS) applied over the dorsolateral prefrontal cortex (DLPFC) on error- and conflict-induced behavioral modulations. Two separate cohorts of participants performed two clinically relevant tests of executive control, respectively.

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Article Synopsis
  • - The study investigates how different approaches, like 'practice to inhibit' and 'music', affect cognitive control in stop-signal tasks, focusing on the differences between females and males regarding impulsive behavior and inhibition.
  • - Results showed that females improved significantly in task performance after practice, while males showed no improvement; additionally, music affected response times differently, with females speeding up and males slowing down.
  • - The findings suggest that sex differences in executive control functions may influence vulnerability to neuropsychological disorders, indicating a need for tailored rehabilitation strategies based on gender.
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