Interactions between perception and action programming: Evidence from visual extinction and optic ataxia

Abstract

We report a series of 7 experiments examining the interaction between visual perception and action programming, contrasting 2 neuropsychological cases: a case of visual extinction and a case with extinction and optic ataxia. The patients had to make pointing responses to left and right locations, whilst identifying briefly presented shapes. Different patterns of performance emerged with the two cases. The patient with “pure” extinction (i.e., extinction without optic ataxia) showed dramatic effects of action programming on perceptual report. Programming an action to the ipsilesional side increased extinction (on 2-item trials) and tended to induce neglect (on 1-item trials); this was ameliorated when the action was programmed to the contralesional side. Separable effects of using the contralesional hand and pointing to the contralesional side were apparent. In contrast, the optic ataxic patient showed few effects of congruency between the visual stimulus and the action, but extinction when an action was programmed. This effect was particularly marked when actions had to be made to peripheral locations, suggesting that it reflected reduced resources to stimuli. These effects all occurred using stimulus exposures that were completed well before actions were effected. The data demonstrate interactions between action programming and visual perception. Programming an action to the affected side with the contralesional limb reduces “pure” extinction because attention is coupled to the end point of the action. However, in a patient with deficient visuo-motor coupling (optic ataxia), programming an action can increase a spatial deficit by recruiting resources away from perceptual processing. The implications for models of perception and action are discussed.

Keywords:

• Perception and action
• Visual extinction
• Optic ataxia.

This work was supported by grants from the Medical Research Council and the Stroke Association, UK. We thank both M.H. and R.H. for their very kind participation.

Notes

¹ The exact characterization of optic ataxia is controversial (cf. Milner & Goodale, 1995; Rossetti & Pisella, 2002), but all accounts agree that motor programming to visual targets is problematic. Our aim here is not to characterize this visuo-motor deficit more accurately, but rather to examine its consequences on visual perception.

² Experiment 5 was conducted some time after the other experiments. However, throughout that time both patients continued to be tested, and both showed a stable pattern of performance (including continuing to manifest extinction and showing effects of pointing on visual identification). It is very unlikely that any differential effects of pointing versus lifting reflected the passage of time.

³ Note though that the cue on a trial was unrelated to where the target could appear, as each cue occurred equally often with each target condition.