Testing the dorsal stream attention hypothesis: Electrophysiological correlates and the effects of ventral stream damage

Abstract

The roles of dorsal and ventral processing streams in visual orienting and conscious perception were examined in two experiments. The first employed high density EEG with source localization. The second comprised a neuropsychological case study. Visual orienting was assessed with an attention procedure, where peripheral letters cued participants towards a target location. In the perception procedure participants responded to the same letters by performing an explicit conscious discrimination. In Experiment 1, the peripheral letters elicited rapid dorsal stream activation in the attention procedure, and this activation preceded top-down enhancement of target processing in occipital cortex. In the perception procedure early ventral stream activation was seen. In addition, peripheral letters elicited an “early directing attention negativity” (EDAN) over parietal recording sites in the attention procedure, but not in the perception procedure. In Experiment 2, a patient with a bilateral ventral stream lesion but preserved dorsal stream function showed clear disruption to performance in the perception procedure, whilst exhibiting a normal visual orienting effect in the attention procedure. Taken together these findings (1) highlight the distinct roles of the dorsal and ventral streams in attention and perception, and (2) suggest how these streams might interact, via reentrant effects of attention on perceptual processing.

Keywords:

• Attention
• Dorsal stream
• Ventral stream
• Visual orienting
• Visual perception

Acknowledgements

We thank Nick McNair, Jeff Hamm, Ian Kirk, and Vanessa Lim for technical assistance and valuable discussion. We thank Michael Posner and Johan Wagemans for helpful comments on an earlier draft. This work was supported by a Methusalem grant (METH/08/02) awarded to Johan Wagemans from the Flemish Government. N.E.M. and L.H. de-W. are joint first authors of this paper.

Notes

¹It is important to remember here that the cue stimuli themselves were always bilateral. Contracues and ipsicues were cues that indicated a contralateral and ipsilateral target, respectively.

²Although the activations illustrated in Figure 5a and Figure 6a confirm the prediction of the dorsal stream attention hypothesis, it is possible that activity in the tectopulvinar visual pathway could also have contributed to activation of these structures. With EEG techniques of the kind used here it is not possible to evaluate the relative contribution of the dorsal cortical visual pathway and the tectopulvinar pathway to the parietal activations illustrated in Figure 5a and Figure 6a. However, evidence from an fMRI study that is currently underway is likely to shed light on this issue.