Abstract
The ‘magnocellular advantage’ model of visual processing (Laycock, Crewther & Crewther, 2007) suggests that the faster magnocellular inputs to V1 allow a rapid dorsal stream activation of parietofrontal attentional processing. This exogenously driven attention system is argued to be activated prior to, and in order to facilitate, object recognition through the ventral stream. We therefore investigated stimuli with or without temporal salience to test whether dorsal stream functioning is differentially involved in such stimuli. This was achieved by measuring contrast sensitivity for two object recognition tasks. In the Abrupt onset task, peak contrast was abruptly presented for 50ms (temporal salience). In the Ramped onset task, contrast increased linearly over 163ms to a peak contrast and then ramped off over 163 ms (reduced temporal salience). Motion coherence detection thresholds were used to divide participants into groups of good and poor dorsal stream functioning groups. Although all participants had normal intelligence and visual acuity, the good motion coherence group showed superior performance on the Abrupt Onset task compared with the poor motion coherence group. Groups did not differ on the Ramped Onset task. We suggest that rapid dorsal stream activation is important for initiating attentional processes when a visual stimulus shows temporal salience. By comparison, when temporal salience is reduced, stimuli do not efficiently/effectively activate dorsal stream attention mechanisms prior to object processing in the ventral stream.
1 Laycock, Crewther, & Crewther (2007), Neurosci & Biobehav Rev, 31, 363-376
Australian Research Council Discovery Grant.