Biomedical subjects

Tracy L Luks

Publications and source records attributed to Tracy L Luks.

6 recordsLinked to original sources

PubMed2006

Rapid targeting followed by sustained deployment of visual spatial attention.

We investigated preparatory attention processes when a spatial discrimination was required at a cued location, by measuring electroencephalography following a central symbolic cue to deploy spatial attention. Electroencephalography activity in response to the cue revealed three cue-related activations: an early-onset positivity following the P1 at posterior scalp sites contralateral to the cued location, followed by cue-related frontal scalp activity and later-onset sustained activity at posterior scalp sites contralateral to the cued location. The early contralateral positivity may reflect rapid targeting of the cued location. Our results also extend the findings of cue-related frontal activity followed by posterior activity contralateral to the cued location, found with nonspatial feature discriminations, to a task requiring a spatial discrimination.

Adult↗

PubMed2006

Brain activation patterns during memory of cognitive agency.

Agency is the awareness that one's own self is the agent or author of an action, a thought, or a feeling. The implicit memory that one's self was the originator of a cognitive event - the sense of cognitive agency - has not yet been fully explored in terms of relevant neural systems. In this functional magnetic resonance imaging (fMRI) study, we examined brain activation patterns differentiating memory for the source of previously self-generated vs. experimenter-presented word items from a sentence completion paradigm designed to be emotionally neutral and semantically constrained in content. Accurate memory for the source of self-generated vs. externally-presented word items resulted in activation of dorsal medial prefrontal cortex (mPFC) bilaterally, supporting an emerging body of work that indicates a key role for this region in self-referential processing. Our data extend the function of mPFC into the domain of memory and the accurate retrieval of the sense of cognitive agency under conditions where agency was encoded implicitly.

Adult↗

PubMed2005

Parallel networks operating across attentional deployment and motion processing: a multi-seed partial least squares fMRI study.

Anticipatory deployment of attention may operate through networks of brain areas that modulate the representations of to-be-attended items in advance of their occurrence through top-down control. Luks and Simpson (2004) (Luks, T.L., Simpson, G.V., 2004. Preparatory deployment of attention to motion activates higher order motion-processing brain regions. NeuroImage 22, 1515-1522) found activations in both control areas and sensory areas during anticipatory deployment of attention to visual motion in the absence of stimuli. In the present follow-up analysis, we tested which network activity during anticipatory deployment of attention is functionally connected with task-related network activity during subsequent selective processing of motion stimuli. Following a cue (anticipatory phase), participants monitored a sequence of complex motion stimuli for a target motion pattern (task phase). We analyzed fMR signal using a partial least squares analysis with previously identified cue- and motion-related voxels as seed regions. The method identified two networks that covaried with the activity of seed regions during the cue and motion-stimulus-processing phases of the task. We suggest that the first network, involving ventral intraparietal sulcus, superior parietal lobule and motor areas, is related to anticipatory and sustained visuomotor attention. Operating in parallel to this visuomotor attention network, there is a second network, involving visual occipital areas, frontal areas as well as angular and supramarginal gyri, that may underlie anticipatory and sustained visual attention processes.

Adult↗

PubMed2004

Preparatory deployment of attention to motion activates higher-order motion-processing brain regions.

We used event-related fMRI to test the hypothesis that preparatory attention modulations occur in higher-order motion-processing regions when subjects deploy attention to internally driven representations in a complex motion-processing task. Using a cued attention-to-motion task, we found preparatory increases in fMRI activity in visual motion regions in the absence of visual motion stimulation. The cue, a brief enlargement of the fixation cross, directed subjects to prepare for a complex motion discrimination task. This preparation activated higher-order and lower-order motion regions. The motion regions activated included temporal regions consistent with V5/MT+, occipital regions consistent with V3+, parietal-occipital junction regions, ventral and dorsal intraparietal sulcus, superior temporal sulcus (STS), posterior insular cortex (PIC), and a region of BA 39/40 superior to V5/MT+ involving the angular gyrus and supramarginal gyrus (A-SM). Consistent with our hypothesis that these motion sensory activations are under top-down control, we also found activation of an extensive frontal network during the cue period, including anterior cingulate and multiple prefrontal regions. These results support the hypothesis that anticipatory deployment of attention to internally driven representations is achieved via top-down modulation of activity in task-relevant processing areas.

Adult↗

PubMed2003

Brain lesion volume and neuropsychological function predict efficacy of treatment for depression in multiple sclerosis.

This study examined the effects of brain lesions and neuropsychological impairment on the efficacy of treatment for depression in patients with comorbid diagnoses of multiple sclerosis (MS) and major depressive disorder (MDD). Thirty patients meeting criteria for MS and MDD received 1 of 3 16-week treatments for depression and were followed for 6 months following treatment cessation. T2-weighted magnetic resonance imaging and neuropsychological evaluations were also obtained. End-of-treatment Beck Depression Inventory (BDI; A. T. Beck, C. H. Ward, M. Mendelson, J. Mock, & J. Erbaugh, 1961) results residualized for baseline BDI were related to right temporal periventricular lesion volume (R2=.32, p=.002) and left temporal grey-white junction lesion volume (R2=.19, p=.02) but were not statistically related to lesion volume in any other brain region or to neuropsychological function. BDI results at 6-month follow-up, residualized for end-of-treatment BDI, were predicted by total lesion volume (R2=.22, p=.005), lesion volume in many discrete areas, and neuropsychological functioning (R2=.29, p=.0009). The effect of total lesion volume on 6-month follow-up BDI results was fully mediated by neuropsychological function.

Adult↗

PubMed2002

Evidence for anterior cingulate cortex involvement in monitoring preparatory attentional set.

An important cognitive function underlying unified, voluntary behavior is attentional control. Two frontal regions, anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (DLPFC), appear to be particularly involved in attentional control and monitoring. In this study, we investigated whether ACC is involved in monitoring the preparatory allocation of attention during task switching, or whether ACC is active only when subjects are processing target stimuli and selecting a response, via a cued-attention design. Event-related BOLD fMRI activity was examined using a cue-target paradigm in which subjects performed task switches that selectively required reallocation of attention when tasks changed. There were three cue conditions: informative switch, informative repeat, and neutral. There were four target conditions: informatively cued switch, informatively cued repeat, neutrally cued switch, and neutrally cued repeat. Significant ACC activity was observed following both informative switch and informative repeat cues, but not after neutral cues. No significant ACC activity was observed following any of the target conditions. Significant DLPFC activity was observed following all three cue conditions and following neutrally cued switch targets. Overall, our results suggest that ACC is involved in monitoring the preparatory allocation of attention for conflict at the level of activation of competing attentional sets. The results also support the role of DLPFC in holding cognitive goals in working memory and allocating attention to the appropriate processing systems to meet those goals.

Adult↗