Memory-guided saccade processing in visual form agnosia (patient DF)
- 396 Downloads
According to Milner and Goodale’s model (The visual brain in action, Oxford University Press, Oxford, 2006) areas in the ventral visual stream mediate visual perception and off-line actions, whilst regions in the dorsal visual stream mediate the on-line visual control of action. Strong evidence for this model comes from a patient (DF), who suffers from visual form agnosia after bilateral damage to the ventro-lateral occipital region, sparing V1. It has been reported that she is normal in immediate reaching and grasping, yet severely impaired when asked to perform delayed actions. Here we investigated whether this dissociation would extend to saccade execution. Neurophysiological studies and TMS work in humans have shown that the posterior parietal cortex (PPC), on the right in particular (supposedly spared in DF), is involved in the control of memory-guided saccades. Surprisingly though, we found that, just as reported for reaching and grasping, DF’s saccadic accuracy was much reduced in the memory compared to the stimulus-guided condition. These data support the idea of a tight coupling of eye and hand movements and further suggest that dorsal stream structures may not be sufficient to drive memory-guided saccadic performance.
KeywordsMemory-guided saccades Delay Eye movements Visual form agnosia Patient DF Dorsal and ventral stream Perception Action
We would like to thank all the participants, DF in particular, for their time and patience and the reviewers of their most constructive comments on an earlier version of this manuscript. SR was funded by a Portuguese Foundation for Science and Technology grant (number SFRH/BD/23230/2005) and LS is funded by a Glasgow FIMS faculty scholarship.
- Crawford JR, Howell DC (1998) Comparing an individual’s test score against norms derived from small samples. Clin Neuropsychol 12:482–486Google Scholar
- Dijkerman HC, Milner AD, Carey DP (1997) Impaired delayed and anti-saccades in a visual form agnosic. Exp Brain Res 117(suppl):S66Google Scholar
- Milner AD (1997) Neglect, extinction and the cortical streams of visual processing. In: Thier P, Karnath H-O (eds) Parietal lobe contributions to orientation in 3D space. Springer, Heidelberg, pp 3–22Google Scholar
- Milner AD, Goodale MA (1995) The visual brain in action. Oxford University Press, OxfordGoogle Scholar
- Milner AD, Goodale MA (2006) The visual brain in action, 2nd edn. Oxford University Press, OxfordGoogle Scholar
- Milner AD, Dijkerman HC, Carey DP (1999a) Visuospatial processing in a pure case of visual from agnosia. In: Burgess N, Jeffrey KJ, O’Keefe J (eds) The hippocampal and parietal functions of spatial cognition. Oxford University Press, Oxford, pp 443–466Google Scholar
- Mueri RM, Vermerschm AI, Rivaud S, Gaymard B, Pierrot-Deseilligny C (1996) Effects of single pulse transcranial magnetic stimulation over the prefrontal and posterior parietal cortices during memory-guided saccades in humans. J Neurophysiol 76:2102–2106Google Scholar