Representation of object continuity in the visual cortex

Abstract

An amazing feature of our visual system is the ability to detect and track objects in the stream of continually changing retinal images. Theories have proposed that the system creates temporary internal representations that persist across changing images, providing continuity. But how such representations are formed in the brain is not known. Here we examined the time course of the responses of border-ownership selective neurons in visual cortex to displays that portray object continuity. We found that the neurons signal border-ownership immediately when new objects appear, but when a border that has been assigned to one object is reassigned to another object while the first remains in the display, the initial responses persist. The neurons continue to signal the initial assignment despite the presence of contradicting figure-ground cues. We propose that border-ownership selectivity reflects mechanisms that create object continuity.

Remapping of Border Ownership in the Visual Cortex

“…The details of our general methods have been described (O’Herron and von der Heydt, 2009; O’Herron and von der Heydt, 2011). …”

“…For the saccade experiment, the responses were aligned to the saccade time t o and averaged. The average response histograms were fit with a two-phase function: a constant estimating the baseline activity, and a sum of two exponentials with independent amplitudes and time constants (O’Herron and von der Heydt, 2011). The transition point was taken as the latency of the response.…”

“…Indeed, a large proportion of these neurons are also sensitive to stereoscopic depth (Qiu and von der Heydt, 2005) in a way that is consistent with a role in detecting occluding contours and the direction of occlusion. The underlying processes are not fully understood, but recent experiments indicate that border ownership selectivity reflects the emergence of early object representations: The responses of border ownership selective neurons parallel the changes in perceived border assignment when the perceptual object interpretation of the visual stimulus changes (Qiu and von der Heydt, 2007; O’Herron and von der Heydt, 2011), and are influenced by object-based attention (Qiu et al, 2007). …”

Border-ownership coding

“…Even though a large part of our visual system is retinotopically organized, we maintain a stable visual perception. O'Herron and von der Heydt (2009,2011) discovered that the border ownership signals in V2 neurons often persist for over a second when the figure-ground assignment becomes ambiguous (see Figure 9). Even more interesting, this border ownership persistence can be remapped during saccades and moves with the ambiguous displays if they jump to a new location (O'Herron & von der Heydt, 2013).…”

Short-term depression and transient memory in sensory cortex

“…In the prefrontal and parietal lobes, persistent activity can last for tens of seconds during working memory tasks, for a review see Curtis and D’Esposito (2003). Shorter decaying memory traces have recently been found in early sensory areas including visual, auditory and somatosensory cortex, and the olfactory bulb (Super et al, 2001; Shuler and Bear, 2006; O’Herron and von der Heydt, 2009; Nikolić et al, 2009; O’Herron and von der Heydt, 2011; Petreanu et al, 2012; Patterson et al, 2013). These traces rise over tens of milliseconds and decay over seconds.…”