Modelo tradicional de desarrollo CMMI

Brain imaging research on bistable perception up to date has significantly

contributed to locating the brain regions that underlie this phenomenon (Britz, Landis & Michel, 2008; Leopold & Logothetis, 1999; Rock & Mitchener, 1992). Brain-imaging studies indicated that both low-level (primary visual cortex) and high-level regions (higher frontal areas) influence the perceptual alternations in bistable perception (Qiu et al., 2009; Sterzer & Kleinschmidt, 2007; Weilnhammer, Ludwig, Hesselmann &

Sterzer, 2013). On the one hand, some studies found that activity in the primary sensory cortex (e.g. primary visual areas) contributed to multistable perception, which was suggested to be the underlying cause of the spontaneous alternations in perception (Andrews, Schluppeck, Homfray, Matthews & Blakemore, 2002). For instance,

neuroimaging studies using Rubin’s Face-Vase found increased activations in the fusiform face area (FFA) during periods when subjects perceived the faces as the foreground figure versus the vase (Andrews, Schluppeck, Homfray, Matthews, & Blakemore, 2002; Hasson, Hendler, Ben Bashat, & Malach, 2001). Other studies revealed that top-down modulation from high-level regions such as the frontal/parietal cortices determined those alternations (Brascamp, Blake & Knapen, 2015; de Graaf, de Jong, Goebel, van Ee & Sack, 2011). For instance, Lumer et al. (1998) presented results that suggest that frontoparietal regions are activated during binocular rivalry stimuli. Moreover, in a study using Rubin’s Face-Vase and Boring’s Old/Young Woman, Kleinschmidt et al. (1998) found responses in the extrastriate visual cortical areas, most prominently in bilateral ventral occipital cortex (middle fusiform gyrus) and posterior intraparietal as well as in other occipital and some frontal areas during perceptual reversals.

Kornmeier and Bach (2012) have linked several findings in the fMRI and multistable perception literature to the destabilization process. One of those findings is Lumer et al. (1998)’s study in which they found selective right-hemispheric BOLD (fMRI) activation during perceptual reversals of the ambiguous variants of binocular rivalry stimuli, but not for their unambiguous counterparts, whereby two different unambiguous stimuli are presented successively (e.g. presenting a left-facing Necker Cube followed by a right-facing one; see Figure 5 in Chapter 2).

In line with this, Sterzer and Kleinschmidt (2007) found increased fMRI response in the right inferior frontal cortex (IFC) with endogenous motion reversals of the Stroboscopic Alternative Motion (SAM; von Schiller, 1933) stimulus but not with

exogenous reversals. They found an earlier onset of the BOLD response in the right IFC associated with endogenous perceptual reversals, compared to the exogenous ones. Their results showed no onset difference in the occipital and parietal regions. This suggests that the right IFC plays a role in perceptual reorganizations (Leopold & Logothetis, 1999; i.e. destabilization, Kornmeier & Bach, 2012).

Similarly, Ilg et al. (2008), using the spinning wheel illusion (Wertheimer, 1912) found posterior right-hemispheric fMRI activity only with endogenous reversals.

Zaretskaya et al. (2010) found during perceptual reversals of a rivalrous face/house stimulus a stronger BOLD response in the right intraparietal sulcus for some participants and in the left intraparietal sulcus for others. The top-down role of the IFC on visual processing during perceptual reversals has been widely studied using a multitude of ambiguous stimuli. For instance, using the Lissajous figure, a type of Structure from Motion ambiguous figure (Weber, 1930), Weilnhammer et al. (2013) found greater activation in a right-lateralized frontoparietal network during reversals. To further these findings and our understanding of the functional role of the frontoparietal network, Brascamp et al. (2015) used a binocular rivalry procedure to investigate the activity in this network for unreportable switches in bistable perception. They developed this type of stimulus by presenting different inputs (different sequence of quasi-randomly moving dots – they differed in in position and motion direction but had the same dot density and overall motion content) to each eye of the participant simultaneously. The subjective switching between these two percepts is so inconspicuous as to become unreportable. They found that reversal related activity in this region was minimized by this procedure,

suggesting that the frontoparietal regions are involved in reversals that have been consciously registered.

Wang et al. (2013) conducted an experiment using Multivariate Pattern Analysis on fMRI data. Wang et al. (2013) used this type of analysis in order to decode patterns of activity associated with perceptual reversals in two ambiguous stimuli (Necker Cube and Face-Vase) with their unambiguous variants (see Figures 4&5 in Chapter 2). They found that activation patterns right before button press in medial and orbitofrontal cortices, precentral/central sulci, and ventral temporal and insular regions were able to decode upcoming perceptual reversals. This means that the pattern of activity linked to perceptual reversal trials in those regions is significantly distinguishable from the activation pattern linked to perceptual stability trials.

The results of this study showed that as time progressed following the button presses, activity related to the percept moved from frontal and anterior temporal regions to posterior visual cortices (Wang et al., 2013). Moreover, Wang et al. (2013) found that areas in frontoparietal, anterior, and ventral temporal cortices showed similar results for the unambiguous and ambiguous conditions. This suggests that there are similar patterns of activity between unambiguous stimuli and the corresponding perceptions of

ambiguous stimuli in these regions. However, this was not the case for the activity pattern observed in V1. This is because low-level features of the stimuli were different between ambiguous and unambiguous conditions. These findings were consistent across both types of stimuli.

Functional neuroimaging studies have outlined a plausible anatomy of perceptual multistability but the specific results vary as a function of the type of multistable

stimulus and probably also with the mechanisms underlying changes in perceptual interpretation. Functional neuroimaging studies show that transient event-related signal changes time-locked to changes in percept choice occur in those functionally specialized areas that are sensitive to the perceptual content (e.g. increased FFA when perceiving faces in Rubin’s Face-Vase) that is perceived to change (Lumer et al., 1998;

Kleinschmidt et al., 1998; Lumer & Rees, 1999; Sterzer et al., 2002). However, fMRI suffers from a temporal resolution problem, making the specific time-locking of events difficult.