Visual Working Memory Contents Bias Ambiguous Structure from Motion Perception
Triesch J (2013) Visual Working Memory Contents Bias Ambiguous Structure from Motion Perception. PLoS
ONE 8(3): e59217. doi:10.1371/journal.pone.0059217
Visual Working Memory Contents Bias Ambiguous Structure from Motion Perception
Lisa Scocchia 0
Matteo Valsecchi 0
Karl R. Gegenfurtner 0
Jochen Triesch 0
Joy J. Geng, University of California, Davis, United States of America
0 1 Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe University , Frankfurt am Main, Germany , 2 Giessen University, Department of Psychology , Giessen, Germany , 3 University of Milano-Bicocca, Department of Psychology , Milano , Italy
The way we perceive the visual world depends crucially on the state of the observer. In the present study we show that what we are holding in working memory (WM) can bias the way we perceive ambiguous structure from motion stimuli. Holding in memory the percept of an unambiguously rotating sphere influenced the perceived direction of motion of an ambiguously rotating sphere presented shortly thereafter. In particular, we found a systematic difference between congruent dominance periods where the perceived direction of the ambiguous stimulus corresponded to the direction of the unambiguous one and incongruent dominance periods. Congruent dominance periods were more frequent when participants memorized the speed of the unambiguous sphere for delayed discrimination than when they performed an immediate judgment on a change in its speed. The analysis of dominance time-course showed that a sustained tendency to perceive the same direction of motion as the prior stimulus emerged only in the WM condition, whereas in the attention condition perceptual dominance dropped to chance levels at the end of the trial. The results are explained in terms of a direct involvement of early visual areas in the active representation of visual motion in WM.
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When we interact with our environment, we are often faced
with noisy or ambiguous sensory information. Under those
conditions, what we perceive can be largely determined by the
state of our cognitive system, including our beliefs and
expectations. This might be adaptive given that our expectations are
broadly consistent with the laws and statistics of the environment.
However, our visual perception might also be prone to the
influence of more volatile cognitive factors. One prominent and
ever-changing aspect of our mental state are the contents of
working memory. Visual working memory is the system that
underpins our ability to briefly store and actively operate on visual
representations. As such, it is fundamental for most activities
requiring vision: from learning a new way to the bus station to
jotting down the bus schedule in the diary. Indeed, numerous
studies have investigated the effects of retaining an item in visual
WM on the attentional processing of subsequently presented items
[15]. Recent evidence further showed that a visual search target
is not only processed faster, but also more accurately when it is
embedded in an object that looks like a memorized object [6], and
that coherent motion pulses are more easily identified within
a stream of incoherent motion when their direction matches the
one of a memorized stimulus [7].
In the present study we ask whether holding a visual object in
WM may have a direct impact on the way subsequently presented
objects are perceived, particularly when our visual system has to
deal with information ambiguous to the point of generating
bistable perception.
When viewing a bistable stimulus, the observer perceives it
switching spontaneously and unpredictably between two (or more)
alternative interpretations. It is well established that bistable
perception is prominently influenced by low-level factors, such as
neural satiation, neural noise and competition between
representations at different levels of the visual pathway. Several models
have been proposed to account for spontaneous perceptual
alternations solely on the ground of low-level mechanisms [8
12]. However, even current low-level accounts of binocular rivalry
[13], where ambiguity is induced by displaying incompatible
monocular images to the two eyes, leave open the possibility of
top-down influences on rivalry dynamics. In other words,
contemporary models that posit neural adaptation and noise as
necessary factors leading to perceptual alternations, typically
consider these factors as susceptible to cognitive modulations.
Other models regard bistable perception as the outcome of
continuous interaction between lower-level and higher-level brain
areas [1416].
The question whether bistable perception is amenable to
cognitive influence has a long history [17]. A role of subjective
intention, or task instructions, in the perception of ambiguous
stimuli is now well established [1820]. Although there is
general agreement on the observers capability to voluntarily
control the alternation rate between two percepts across a wide
range of bistable stimul (...truncated)