PubMed Health⌕ Search

Biomedical subjects

Eric H Schumacher

Publications and source records attributed to Eric H Schumacher.

7 recordsLinked to original sources
PubMed2007

Selection and maintenance of stimulus-response rules during preparation and performance of a spatial choice-reaction task.

The ability to select an appropriate response among competing alternatives is a fundamental requirement for successful performance of a variety of everyday tasks. Recent research suggests that a frontal-parietal network of brain regions (including dorsal prefrontal, dorsal premotor and superior parietal cortices) mediate response selection for spatial material. Most of this research has used blocked experimental designs. Thus, the frontal-parietal activity reported may be due either to tonic activity across a block or to processing occurring at the trial level. Our current event-related fMRI study investigated response selection at the level of the trial in order to identify possible response selection sub-processes. In the study, participants responded to a visually presented stimulus with either a spatially compatible or incompatible manual response. On some trials, several seconds prior to stimulus onset, a cue indicated which task was to be performed. In this way we could identify separate brain regions for task preparation and task performance, if they exist. Our results showed that the frontal-parietal network for spatial response selection activated both during task preparation as well as during task performance. We found no evidence for preparation specific brain mechanisms in this task. These data suggest that spatial response selection and response preparation processes rely on the same neurocognitive mechanisms.

Adult↗
PubMed2005

The neural effect of stimulus-response modality compatibility on dual-task performance: an fMRI study.

Recent fMRI studies suggest that the inferior frontal sulcus (IFS) is involved in the coordination of interfering processes in dual-task situations. The present study aims to further specify this assumption by investigating whether the compatibility between stimulus and response modalities modulates dual-task-related activity along the IFS. It has been shown behaviorally that the degree of interference, as measured by dual-task costs, increases in modality-incompatible conditions (e.g. visual-vocal tasks combined with auditory-manual tasks) as compared to modality-compatible conditions (e.g. visual-manual tasks combined with auditory-vocal tasks). Using fMRI, we measured IFS activity when participants performed modality-compatible and modality-incompatible single and dual tasks. Behaviorally, we replicated the finding of higher dual-task costs for modality-incompatible tasks compared to modality-compatible tasks. The fMRI data revealed higher activity along the IFS in modality-incompatible dual tasks compared with modality-compatible dual tasks when inter-individual variability in functional brain organization is taken into account. We argue that in addition to temporal order coordination (Szameitat et al., 2002), the IFS is involved in the coordination of cognitive processes associated with the concurrent mapping of sensory information onto corresponding motor responses in dual-task situations.

Association Learning↗
PubMed2005

Sustained involvement of a frontal-parietal network for spatial response selection with practice of a spatial choice-reaction task.

With practice, performance on a task typically becomes faster, more accurate, and less prone to interference from competing tasks. Some theories of this performance change suggest it reflects a qualitative reorganization of the cognitive processing required for successful task performance. Other theories suggest this change in performance reflects a more quantitative change in the amount of processing required to perform the task. Neuroimaging research results provide some support for both of these broad theories. This inconsistency may reflect the complex nature of the effect of practice on cognitive and neural processing. Our current experiment addresses this issue by investigating the effect of practice of a relatively easy perceptual-motor task on the frontal-parietal brain network for a specific cognitive process (viz. spatial response selection). Participants were scanned during three functional magnetic resonance imaging sessions on separate days within 4 days while they performed a relatively easy spatial perceptual-motor task. We found sustained activity with practice in right dorsal prefrontal cortex; and sustained but decreasing activity in bilateral dorsal premotor, left superior parietal, and precuneus cortices, supporting a quantitative decrease in difficulty of response selection with practice. Conversely, we found a qualitative change in activity with practice in left dorsal prefrontal cortex. This brain region is outside the response selection network for this task and showed activity only during novel task performance. These results suggest that practice produces both qualitative and quantitative changes in processing. The particular effect of practice depends on the cognitive process in question.

Adult↗
PubMed2004

A functional MRI study of the influence of practice on component processes of working memory.

Previous neuroimaging studies have shown that neural activity changes with task practice. The types of changes reported have been inconsistent, however, and the neural mechanisms involved remain unclear. In this study, we investigated the influence of practice on different component processes of working memory (WM) using a face WM task. Event-related functional magnetic resonance imaging (fMRI) methodology allowed us to examine signal changes from early to late in the scanning session within different task stages (i.e., encoding, delay, retrieval), as well as to determine the influence of different levels of WM load on neural activity. We found practice-related decreases in fMRI signal and effects of memory load occurring primarily during encoding. This suggests that practice improves encoding efficiency, especially at higher memory loads. The decreases in fMRI signal we observed were not accompanied by improved behavioral performance; in fact, error rate increased for high WM load trials, indicating that practice-related changes in activation may occur during a scanning session without behavioral evidence of learning. Our results suggest that practice influences particular component processes of WM differently, and that the efficiency of these processes may not be captured by performance measures alone.

Adult↗
PubMed2003

Neural evidence for representation-specific response selection.

Response selection is the mental process of choosing representations for appropriate motor behaviors given particular environmental stimuli and one's current task situation and goals. Many cognitive theories of response selection postulate a unitary process. That is, one central response-selection mechanism chooses appropriate responses in most, if not all, task situations. However, neuroscience research shows that neural processing is often localized based on the type of information processed. Our current experiments investigate whether response selection is unitary or stimulus specific by manipulating response-selection difficulty in two functional magnetic resonance imaging experiments using spatial and nonspatial stimuli. The same participants were used in both experiments. We found spatial response selection involves the right prefrontal cortex, the bilateral premotor cortex, and the dorsal parietal cortical regions (precuneus and superior parietal lobule). Nonspatial response selection, conversely, involves the left prefrontal cortex and the more ventral posterior cortical regions (left middle temporal gyrus, left inferior parietal lobule, and right extrastriate cortex). Our brain activation data suggest a cognitive model for response selection in which different brain networks mediate the choice of appropriate responses for different types of stimuli. This model is consistent with behavioral research suggesting that response-selection processing may be more flexible and adaptive than originally proposed.

Adult↗
PubMed2002

Neural implementation of response selection in humans as revealed by localized effects of stimulus-response compatibility on brain activation.

Response selection, which involves choosing representations for appropriate motor behaviors given one's current situation, is a fundamental mental process central to a wide variety of human performance, yet the neural mechanisms underlying this mental process remain unclear. Research using nonhuman primates implicates ventral prefrontal and lateral premotor cortices in this process. In contrast, human neuroimaging research also highlights the role of dorsal prefrontal, anterior cingulate, and superior parietal cortices in response selection. This inconsistency may stem from the difficulty of isolating response selection within the constraints of cognitive subtraction methodology utilized in neuroimaging. We overcome this limitation by using an experimental procedure designed to selectively influence discrete mental processing stages and analyses that are less reliant on the assumptions of cognitive subtraction. We varied stimulus contrast to affect stimulus encoding and stimulus-response compatibility to affect response selection. Brain activation data suggest processing specific to response selection in superior parietal and dorsal prefrontal cortices, and not ventral prefrontal cortex. Anterior cingulate and lateral premotor cortices may also be involved in response selection, or these regions may mediate other response processes.

Adolescent↗