Constraints on task-based control of behaviour following frontal lobe damage: A single-case study

Abstract

What factors determine stimulus-driven responses in patients with utilization behaviour? We examined this question by assessing the influence of an irrelevant cue on visual search in a patient showing evidence of utilization behaviour (F.K.), following bilateral damage to the medial frontal and temporal lobes. Despite being able to repeat the instructions, F.K. often responded to an item in the search display that matched the cue rather than the target. This effect was reduced under certain conditions: (a) when the cue–search interval increased, (b) when F.K. paid less attention to the cue, and (c) when the target discrimination task was made more difficult. On the other hand, the effect arose even when the cue was always invalid. We suggest that information from the cue competed with the top-down set to determine search. F.K.'s lesion makes it difficult for him to impose top-down knowledge rapidly, leading to responses automatically being based on attended, but irrelevant, cues under short cue–display intervals.

Keywords:

• Task-based control
• Frontal lobe
• Utilization behaviour
• Visual search
• Selective attention

Acknowledgments

This work was supported by grants from the Biotechnology and Biological Sciences Research Council (BBSRC) and the Medical Research Council (MRC; UK). We thank F.K. for his kind participation.

Notes

¹Having the experimenter respond to F.K.'s action may introduce some noise into the measurements. However, it was difficult to instruct F.K. to use the keyboard in order to make a button press response. Also given the length of F.K.'s response times, any measurement error was slight. Using a touch screen monitor also failed to address the issue.

² We also conducted two separate sessions of Experiment 2 in which, everything else unchanged, the RTs were recorded at different times: (a) at the time of pointing or (b) when F.K. has both pointed and reported the orientation of the target line. We observed no differences between RTs from sessions “a” and “b” and no differences between these RTs from these sessions and RTs in discrimination condition of Experiment 2 (all F < 1.0).

³ The accuracy of the orientation response was not a determining factor in the analysis of discrimination data. All responses were included in the analyses regardless of accuracy of orientation responses.