Search PubMed⌕ Search

Biomedical subjects

Marcel Brass

Publications and source records attributed to Marcel Brass.

21 records · Page 2Linked to original sources

When the same response has different meanings: recoding the response meaning in the lateral prefrontal cortex.

The ability to adapt our behavioral repertoire to different situations and tasks is crucial for our behavioral control. Since the same motor behavior can have different meanings in different task situations, we often have to change the meaning of our responses when we get into a different task context. In a functional MRI experiment we manipulated this response recoding process. Subjects were required to execute two simple spatial tasks in a task switching paradigm. In one condition both tasks required the same set of responses, hence each response had two different meanings depending on the relevant task (bivalent condition). In the other condition subjects used a separate set of responses for each task (univalent condition). While subjects were required to recode the meaning when switching from one task to the next in the bivalent condition, response recoding was not required in the univalent condition. We demonstrate that the lateral prefrontal cortex is involved in recoding of response meaning. These results extend previous assumptions on the role of the prefrontal cortex in behavioral control.

Adult↗

Imitative response tendencies in patients with frontal brain lesions.

It is widely accepted that patients with frontal lesions have problems inhibiting automatic response tendencies. Whereas inhibition deficits of overlearned responses have been extensively investigated using interference tasks like the Stroop task (J. R. Stroop, 1935), it is controversial whether patients with frontal brain lesions also have problems inhibiting imitative responses. Using an interference paradigm, the present study investigated imitative response tendencies in patients with frontal lesions. In addition, it tested whether patients deficient in the inhibition of imitative responses correspondingly have problems inhibiting overlearned responses. It was found that the group with frontal lesions displayed significantly stronger imitative response tendencies than the group with nonfrontal lesions. Furthermore, it was shown that the inhibition of imitative responses is functionally unrelated to Stroop interference.

Adult↗

The role of the frontal cortex in task preparation.

The ability to prepare a task is crucial for the voluntary control of our actions. It enables us to react flexibly and rapidly to a changing environment. In the present event-related functional magnetic resonance imaging study we investigated task preparation with a task-cueing paradigm. In this paradigm we intermixed trials in which a task cue and a target were presented with trials in which only the task cue was presented. Analysis of these cue-only trials allowed us to isolate task-preparation related control from execution-related control processes. By means of this paradigm, we could demonstrate that a frontal network was related to task preparation. Further analysis revealed that the fronto-lateral cortex at the junction of precentral sulcus and inferior frontal sulcus and the presupplementary motor area are the crucial frontal components in task preparation.

Adult↗