Cortical mechanisms for trans-saccadic memory and integration of multiple object features

Abstract

Constructing an internal representation of the world from successive visual fixations, i.e. separated by saccadic eye movements, is known as trans-saccadic perception. Research on trans-saccadic perception (TSP) has been traditionally aimed at resolving the problems of memory capacity and visual integration across saccades. In this paper, we review this literature on TSP with a focus on research showing that egocentric measures of the saccadic eye movement can be used to integrate simple object features across saccades, and that the memory capacity for items retained across saccades, like visual working memory, is restricted to about three to four items. We also review recent transcranial magnetic stimulation experiments which suggest that the right parietal eye field and frontal eye fields play a key functional role in spatial updating of objects in TSP. We conclude by speculating on possible cortical mechanisms for governing egocentric spatial updating of multiple objects in TSP.

The role of head movements in the discrimination of 2-D shape by blind echolocation experts

“…These saccades allow a person to accumulate visual information from the boundaries of a large object and the features of a visual scene, which are then pieced together to create an overall perceptual representation. This process, termed transsaccadic integration, requires the brain to make quick computations of the incoming visual information in order to arrive at a rich and stable representation of an object or scene (Neimeier, Crawford, & Tweed, 2003;Prime, Vesia, & Crawford, 2011). In terms of echolocation in the current study, making head movements while producing mouth-clicks (or other signals) could have provided sound snapshots -or 'echo saccades' -that are then automatically pieced together by the brain to provide the individual with a perceptual representation of the object.…”

Visual stability

“…Reviews of studies with clinical patients [25] and with TMS [27] show how the use of well-designed behavioural tests can give insight into the mechanisms of visual stability. At the same time, the presence of redundant circuits [20] might mask the functional role of individual brain regions.…”

“…As reviewed by Hamker et al, different computational models of visual stability incorporate varying types of dynamic receptive fields. Remapping in the frontal eye fields (FEF), for example, has been linked to the development of a predictive map of the expected consequences of the saccade [21,26] while remapping in the posterior parietal cortex has been linked to post-saccadic updating of visual working memory [27]. Two of the articles in this special issue [20,21] review the recent attempts to directly link remapping circuits to behaviour by disrupting the flow of information within the primate brain.…”

“…Regions in posterior parietal cortex (LIP, in monkey), the frontal eye fields and the superior colliculus work together in guiding eye movements and, not surprisingly, these areas show remapping of oculocentric receptive fields [20,21]. In humans, evidence from TMS and clinical studies (reviewed in [25,27]) suggests that the right posterior parietal cortex may play a special role in maintaining spatial constancy (see also [73]). Lesions to the thalamus can also lead to failures of visual stability, in which self-movement and external, object movement are confounded [74].…”

“…One possibility is that the well-established connection from the FEF to visual areas such as V4 [75,76] plays a role in predictive remapping of visual neurons. Likewise, as Prime et al [27] point out, the link between visuo-spatial working memory areas would need to be maintained across saccades. There is growing evidence that visual processing areas play an important role in maintaining details in visual memory [77].…”