Figure 7. Frontal Lesion and Re-visiting Locations in the Scan Path.

a. When the frontal module is unilaterally lesioned, symptoms of neglect are present in the scan path (overt attention shown here). This shows that a lesion in an area representing stimuli in a scene(or body)–based frame of reference can produce symptoms of neglect. This figure may be compared to the frontal neglect patient behaviour shown in figure 1c. b. A comparison of the percentage of fixations in the left hemifield following unilateral parietal versus unilateral frontal lesion in this model. The plot shows the mean percentages from 10 separate simulations, each containing 50 shifts of covert attention (values were similar under overt attention). Although the left hemifield is typically neglected following frontal lesion, some fixations are placed in this hemifield. Hence, compared to that following parietal lesion, neglect is less severe with frontal lesion in this model. c. When the frontal module is completely lesioned the scan path has difficulty exploring the scene and perseverates in one area. An overt attention simulation is shown here but similar effects are produced under conditions of covert attention. This is due to the lack of novelty bias in the system. d. Shows the effect of lesion on re-visiting of locations under covert attention. Locations are more frequently re-visited under conditions of parietal lesion than in normal conditions. However, lesion of the frontal bias in our model causes the greatest increase in re-visiting/re-fixation. The plot shows the mean percentages of re-visited locations from 10 separate simulations, each containing 50 shifts of attention.