Journal of Vision (2007) 7(8):1, 1-12
Schofield, Ledgeway, & Hutchinson
Movies 1-3. Sample stimuli: Movies 1-3 show motion sequences for the three cues used in this study. Left panel, Movie 1, LM; middle
panel, Movie 2, CM; right panel, Movie 3, OM. Such sequences were used in Experiments 1 and 2 (duration = 1 s) and as the adapters in
Experiment 3 (for duration see text). As static images, Movies 1 -3 demonstrate the appearance of a single frame in our motion
sequences. See text for details.
Green, & Georgeson, 1996). The final normalization stage
renders the unified model sensitive to CM signals (Benton,
2004). We note that the unified model splits the process-
ing of LM and CM signals. One part of the model
computes an unnormalized opponent motion energy signal
and is blind to moving CM, whereas the other part
provides the normalization signal and is sensitive to CM
motion. One could argue that the notion of separate first-
and second-order detection is preserved within the unified
gradient/energy model provided that the observer has
independent access to the two signals described above.
However, the second-order signal would most likely
require additional low-level processing prior to any higher
stage motion analysis.
Lu and Sperling (1995, 2001) not only present consid-
erable evidence in favor of separate first- and second-
order motion-detecting mechanisms but also propose an
additional (termed third-order) mechanism that processes
motion based on figure-ground salience. The third-order
system is characterized by (among other things) its poor
temporal acuity relative to either the first-order or second-
order motion-detecting systems (Lu & Sperling, 2001).
Most research on second-order vision has used CM
noise textures as the second-order cue, and there is a
tendency to assume that the second-order system can be
characterized by its response to CM. However, some
recent studies have considered other second-order cues
and have shown that the second-order class may itself be
heterogeneous. For example, spatiotemporal sensitivity for
moving modulations of the length of carrier elements is
very different from that for CM (Hutchinson & Ledgeway,
2006). Similarly, spatial-frequency sensitivity for static
CM peaks at a higher frequency than that for static OM
(compare Gray & Regan, 1998; Kingdom, Keeble, &
Moulden, 1995, with Schofield & Georgeson, 1999).
Further, there is no subthreshold facilitation between
static CM, OM, and frequency modulations (Kingdom,
Prins, & Hayes, 2003; Schofield & Yates, 2005). Finally,
Baker, Mortin, Prins, Kingdom, and Dumoulin (2006)
found similar patterns of fMRI activity in response to
static CM and frequency-modulated stimuli but a different
pattern of activation for static OM. This evidence supports
the notion that there is more than one second-order
detection mechanism.
Although the responses of the human visual system to
first- and second-order motion differ in many respects, we
focus on just one aspect of this comparison here: the
induction of motion aftereffects (MAE). Following pro-
longed viewing of a moving stimulus, a physically static
stimulus will appear to move in the opposite direction (the
static MAE [sMAE]; Wohlgemuth, 1911). A similar effect
can be induced in a flickering test stimulus (the dynamic
MAE [dMAE]; von Grunau, 1986), which can be regarded
as directionally ambiguous rather than strictly static
(Levinson & Sekuler, 1975). Moving first-order gratings
induce both types of MAE, whereas second-order gratings
induce only the dMAE (Nishida and Sato, 1995; see also
Derrington & Badcock, 1985; Ledgeway, 1994). Further,
a compound adapter with first- and second-order (CM)
components moving in opposite directions induces a
sMAE opposite to the first-order component and a dMAE
opposite to the second-order component (Nishida & Sato,
1995).
Here, we assess the ability of moving first-order (LM)
and second-order (CM and OM) gratings to induce a
dMAE in themselves (within-cue adaptation) and in each
other (between-cue adaptation). However, we first review
the limited literature pertinent to the transfer of the dMAE