Images of illusory motion in primary visual cortex
ABSTRACT Illusory motion can be generated by successively flashing a stationary visual stimulus in two spatial locations separated by several degrees of visual angle. In appropriate conditions, the apparent motion is indistinguishable from real motion: The observer experiences a luminous object traversing a continuous path from one stimulus location to the other through intervening positions where no physical stimuli exist. The phenomenon has been extensively investigated for nearly a century but little is known about its neurophysiological foundation. Here we present images of activations in the primary visual cortex in response to real and apparent motion. The images show that during apparent motion, a path connecting the cortical representations of the stimulus locations is filled in by activation. The activation along the path of apparent motion is similar to the activation found when a stimulus is presented in real motion between the two locations.
- SourceAvailable from: Petra Vetter
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- "Using brain imaging, we demonstrated that V1 neurons retinotopically responsive to the apparent motion trace are activated during apparent motion as if real motion was present, despite the absence of actual feed-forward stimulation (Muckli et al. 2005). This effect may be explained by visual motion area V5/ human motion complex, human medial temporal complex (hMT) communicating the prediction of a moving token to V1 via feedback connections (Goebel et al. 1998; Muckli et al. 2002; Silvanto et al. 2005; Larsen et al. 2006; Sterzer et al. 2006; Ahmed et al. 2008; Wibral et al. 2009; Frégnac et al. 2010). Furthermore , we showed that the creation of a predictive signal on the apparent motion trace is spatio-temporally specific: Targets flashed on the apparent motion trace in-time with the illusory motion token are detected better than that flashed out-of-time (Schwiedrzik et al. 2007; Vetter et al. 2012). "
ABSTRACT: Given the vast amount of sensory information the brain has to deal with, predicting some of this information based on the current context is a resource-efficient strategy. The framework of predictive coding states that higher-level brain areas generate a predictive model to be communicated via feedback connections to early sensory areas. Here, we directly tested the necessity of a higher-level visual area, V5, in this predictive processing in the context of an apparent motion paradigm. We flashed targets on the apparent motion trace in-time or out-of-time with the predicted illusory motion token. As in previous studies, we found that predictable in-time targets were better detected than unpredictable out-of-time targets. However, when we applied functional magnetic resonance imaging-guided, double-pulse transcranial magnetic stimulation (TMS) over left V5 at 13–53 ms before target onset, the detection advantage of in-time targets was eliminated; this was not the case when TMS was applied over the vertex. Our results are causal evidence that V5 is necessary for a prediction effect, which has been shown to modulate V1 activity (Alink et al. 2010). Thus, our findings suggest that information processing between V5 and V1 is crucial for visual motion prediction, providing experimental support for the predictive coding framework.Cerebral Cortex 04/2015; 25:1052-1059. DOI:10.1093/cercor/bht297 · 8.67 Impact Factor
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- "Apparent motion is an illusion of motion induced by two stationary stimuli that blink on and off alternately. It gives rise to an illusory object moving between the inducing stimuli along the shortest path, but avoiding obstacles (Kolers, 1963; Attneave and Block, 1974; Shepard and Zare, 1983; Goebel et al., 1998; Muckli et al., 2002, 2005; Liu et al., 2004; Larsen et al., 2006). Long distance apparent motion is a particularly suitable paradigm as higher visual areas have larger receptive fields which enable them to process the spatio-temporal dynamics of the illusion, thus creating a prediction with regard to where the illusory motion token is at a certain time (Alink et al., 2010). "
ABSTRACT: Predicting visual information facilitates efficient processing of visual signals. Higher visual areas can support the processing of incoming visual information by generating predictive models that are fed back to lower visual areas. Functional brain imaging has previously shown that predictions interact with visual input already at the level of the primary visual cortex (V1; Harrison et al., 2007; Alink et al., 2010). Given that fixation changes up to four times a second in natural viewing conditions, cortical predictions are effective in V1 only if they are fed back in time for the processing of the next stimulus and at the corresponding new retinotopic position. Here, we tested whether spatio-temporal predictions are updated before, during, or shortly after an inter-hemifield saccade is executed, and thus, whether the predictive signal is transferred swiftly across hemifields. Using an apparent motion illusion, we induced an internal motion model that is known to produce a spatio-temporal prediction signal along the apparent motion trace in V1 (Muckli et al., 2005; Alink et al., 2010). We presented participants with both visually predictable and unpredictable targets on the apparent motion trace. During the task, participants saccaded across the illusion whilst detecting the target. As found previously, predictable stimuli were detected more frequently than unpredictable stimuli. Furthermore, we found that the detection advantage of predictable targets is detectable as early as 50-100 ms after saccade offset. This result demonstrates the rapid nature of the transfer of a spatio-temporally precise predictive signal across hemifields, in a paradigm previously shown to modulate V1.Frontiers in Psychology 06/2012; 3:176. DOI:10.3389/fpsyg.2012.00176 · 2.80 Impact Factor
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- "Moreover, empirical evidence is mounting that the visual system may use such predictive coding at multiple levels (Murray et al. 2002; Bar et al. 2006; Summerfield et al. 2006, 2008; Schweidrzik et al. 2007; Summerfield and Koechlin 2008), beginning even in the retina (Hosoya et al. 2005). For low-level vision, primary visual cortex appears to extrapolate apparent motion trajectories, by ''filling-in'' trajectories through unseen stimulus positions (Muckli et al. 2005; Larsen et al. 2006; Sterzer et al. 2006). For higher level biological motion stimuli, some have proposed the STS predicts visual patterns (Giese and Poggio 2003; Kilner et al. 2007). "
ABSTRACT: People track facial expression dynamics with ease to accurately perceive distinct emotions. Although the superior temporal sulcus (STS) appears to possess mechanisms for perceiving changeable facial attributes such as expressions, the nature of the underlying neural computations is not known. Motivated by novel theoretical accounts, we hypothesized that visual and motor areas represent expressions as anticipated motion trajectories. Using magnetoencephalography, we show predictable transitions between fearful and neutral expressions (compared with scrambled and static presentations) heighten activity in visual cortex as quickly as 165 ms poststimulus onset and later (237 ms) engage fusiform gyrus, STS and premotor areas. Consistent with proposed models of biological motion representation, we suggest that visual areas predictively represent coherent facial trajectories. We show that such representations bias emotion perception of subsequent static faces, suggesting that facial movements elicit predictions that bias perception. Our findings reveal critical processes evoked in the perception of dynamic stimuli such as facial expressions, which can endow perception with temporal continuity.Cerebral Cortex 08/2009; 20(3):694-703. DOI:10.1093/cercor/bhp140 · 8.67 Impact Factor