Tracing sequential waves of rapid visuomotor activation in lateralized readiness potentials

Processing of natural images is feedforward: A simple behavioral test

“…Indeed, the toy-animal-object and the ellipse-rectangle tasks clearly satisfy the rapid-chase criteria Vath & Schmidt, 2007): Initial responses are time-locked to prime onset and go in the direction specified by the primes (initiation criterion); responses are taken over in midflight by the target signals (takeover criterion); and most important, responses initiated by the prime signals are initially independent of the onset times of the targets (independence criterion). As is shown in Figure 4, spatial priming functions in each task are initially invariant when locked to prime onset, perfectly following exactly the same initial time course before individual priming functions branch off one after another in the order of increasing prime-target SOA.…”

“…Response priming may occur overtly, with noticeable detours of response trajectories in the direction of the prime, or covertly, visible only in the delayed onset of movements after response conflicts are solved. Primes inconsistent with the masks will occasionally provoke response errors, particularly if the prime-mask SOA is long, the prime signal is strong, and the motor response happens to start quickly after prime onset Vath & Schmidt, 2007;Vorberg et al, 2003). Transmission of prime signals is assumed to be fast enough to escape recurrent degradation of the prime signal by visual masking (DiLollo et al, 2000;Fahrenfort et al, 2007;Lamme, 2002;Lamme et al, 2002), so that priming effects remain unaffected even when the prime is heavily masked (Bacon-Macé et al, 2005;Schmidt & Vorberg, 2006;Vorberg et al, 2003).…”

“…The issue of feedforward versus recurrent processing is theoretically interesting because many authors have assumed that feedforward processing alone is insufficient to generate visual awareness and that a stimulus must be processed recurrently to become consciously accessible (DiLollo, Enns, & Rensink, 2000;Fahrenfort, Scholte, & Lamme, 2007;Lamme, 2002;Lamme, Rodriguez-Rodriguez, & Spekreijse, 1999;Lamme & Roelfsema, 2000;Lamme, Zipser, & Spekreijse, 2002;Pascual-Leone & Walsh, 2001;Ro, Breitmeyer, Burton, Singhal, & Lane, 2003;Roelfsema, Tolboom, & Khayat, 2007;Tong, 2003Tong, ). et al, 2006Schmidt & Seydell, 2008;Vath & Schmidt, 2007)-a variant of the response priming paradigm (Dehaene et al, 1998;Eimer & Schlaghecken, 1998;Neumann & Klotz, 1994;Schmidt, 2002;Verleger, Jaśkowski, Aydemir, van der Lubbe, & Groen, 2004;Vorberg, Mattler, Heinecke, Schmidt, & Schwarzbach, 2003)-and has also been confirmed in the time course of lateralized readiness potentials (Vath & Schmidt, 2007). The goal of the present study was to examine the speeded classification of natural images in a paradigm that allowed for evaluation of the rapid-chase criteria, providing a simple and stringent test of the feedforward account advocated in earlier studies.…”

“…Because the feedforward sweep is not directly observable, we have proposed a set of behavioral criteria for tasks in which two stimuli presented in rapid sequence ( prime and target) try to control the same speeded motor response-for example, a single pointing movement (Schmidt, Niehaus, & Nagel, 2006;Vath & Schmidt, 2007). In a simple feedforward system that is reasonably fast and has sufficient temporal resolution, prime and target signals would engage in what we call a rapid chase, with the prime signal maintaining a lead over the target signal all the way to motor control.…”

“…Stimulus-response systems conforming to these criteria are classified as rapid-chase systems Vath & Schmidt, 2007). Note that because of the visuomotor processing delays involved, the sequential response process can unfold after the prime and target stimuli have been presented (and possibly already disappeared).…”