Do we need vision? The effects of visual impairment on the development of the cognitive system.
Sunday, October 02nd, 2011 [09:30 - 11:10]
SY_22. Do we need vision? The effects of visual impairment on the development of the cognitive system
Vecchi, T. 1 & Postma, A. 2, 3
1 Department of Psychology, University of Pavia, Italy
2 Experimental Psychology, Helmholtz Institute, Utrecht University, The Netherlands
3 Department of Neurology, University Medical Centre Utrecht, The Netherlands
We are used to thinking about vision strictly in terms of “seeing with the eyes.” In fact, “to see” does not only require functioning eyes and optic nerves, but also functioning brain structures: blind individuals lack the visual input, but their “central hardware” is spared. This symposium is about the effects that blindness and, more generally, different types of visual deficit exert on the development and functioning of the human cognitive system. There are a number of critical questions that can be addressed through the investigation of the nature of mental representations in visually impaired individuals. First of all, data can shed light on the relationship between visual perception, imagery and working memory, clarifying the extent to which mental imagery (and more generally, the development of the cognitive system) depends upon normally functioning vision. Studying intersensory mechanisms in the blind may also help disentangle the functional and neural relationships between vision and the other senses, and may clarify whether and how “supramodal” mechanisms are affected by the absence of one sensory modality. Furthermore, studying both the totally blind and severely visually impaired individuals helps to shed light on which specific aspects of visual experience (e.g., binocularity) are critical for a correct cognitive development. Finally, studying the blind offers the opportunity of knowing more about neural plasticity. In the absence of vision, the other senses work as functional substitutes and thus are often improved (i.e., sensory compensation). The investigation of the psychological characteristics of blind individuals highlights that human cognitive development is not only shaped by the nature and amount of sensory experience but also presents a number of innate mechanisms and cortical networks that are able to process information in a supramodal fashion. Blindness is not simply “less” vision, it is an other vision.
SY_22.1 - Conceptual combination in blind and sighted subjects: Evidence for perceptual simulation
Struiksma, M. E. 1, 2 , Noordzij, M. L. 3 , Barsalou, L. 4 & Postma, A. 1, 5
1 Experimental Psychology. Helmholtz Institute. Utrecht University. Utrecht, The Netherlands
2 Utrecht Institute of Linguistics OTS. Utrecht University. Utrecht, The Netherlands
3 Department of Cognitive Psychology and Ergonomics. University of Twente. Enschede, The Netherlands
4 Department of Psychology. Emory University. Atlanta, USA
5 Department of Neurology. University Medical Centre Utrecht. Utrecht, The Netherlands
Previous research has shown that occlusion effects occur in conceptual combination. For example, occluded properties such as 'roots' and 'soil' are not perceivable and less available for processing for the concept 'lawn'. However, for the complex concept 'rolled-up lawn' these hidden properties are perceivable and were mentioned in a property generation task. This suggests that subjects constructed perceptual simulations to solve the task. The main question of the current experiment is to what extent visual perception is dominant in perceptual simulations. To answer this question we tested occlusion effects in conceptual combination in both sighted and blind subjects. An occlusion effect was found for the generation of properties of noun phrases. Unoccluded properties were produced more often than occluded properties, but only when a revealing modifier was used (e.g. 'rolled-up lawn') and not when that same modifier was non-revealing (e.g. 'rolled-up snake'). Interestingly this effect was similar in blind and sighted subjects, which suggests an innate role for perceptual simulation. The results will be further discussed in terms of possible qualitative differences between the blind and sighted with respect to the nature of their simulations.
SY_22.2 - The brain as a sensory-motor task machine: insights from the dark
Amedi, A. 1, 2
1 Dpt. of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC)
2 The Edmond and Lily Safra Center for Brain Sciences (ELSC), Hebrew University of Jerusalem, Israel
About one-quarter of our brain “real estate” is devoted to the processing of vision. So what happens to this vast “vision” part of the brain when no visual input is received? We are working with novel high-tech multisensory ‘glasses’ that convert visual information from a tiny video camera into sensory signals that the blind can interpret. In this talk I will mainly highlight work done using The-vOICe algorithm. We have devised a training program which teaches blind individuals to use such a device. Following approximately ~30 hours of training, congenitally blind individuals can use this device to recognize what and where various objects are, for instance within a room (like a chair, glass, and even people and their body posture). Additional training is given specifically for encouraging free “visual” orientation enabling blind individuals to walk in corridors while avoiding obstacles and applying hand-“eye” coordination (e.g. playing bowling). A main focus of the project is using this unique “set-up” to study brain organization and brain’s flexibility. We have demonstrated that visual training can create massive adult plasticity in the ‘visual’ cortex to process functions like recognizing objects and localizing where they are located, much like the original division of labor in the visual system in which the ventral stream recognize objects and the dorsal stream help to localize them in order to orient action. We also found that reading using a different sense (e.g. Braille) recruit the same structure as in sighted, namely the visual word form area. Such visual cortex recruitment for ‘visual’ processing of soundscapes may greatly promote sight restoration efforts both via such technologies and by training people undergoing clinical procedures to restore vision. This approach might also be relevant, in other cases in which massive adult brain plasticity / flexibility is needed, e.g. after a stroke
SY_22.3 - Space, language and touch in blind and sighted individuals
Postma, A. 1, 2 , Struiksma, M. E. 1, 3 & Noordzij, M. L. 4
1 Experimental Psychology, Helmholtz Institute, Utrecht University, The Netherlands
2 Department of Neurology, University Medical Centre Utrecht, The Netherlands
3 Utrecht Institute of Linguistics OTS, Utrecht University, The Netherlands
4 Department of Cognitive Psychology and Ergonomics, University of Twente, The Netherlands
When communicating about the spatial positions of objects in the outside world it is critically important to use the same reference frame. Blind individuals are thought to depend to a great extent on spatial language processing. It is not clear yet which reference frames they prefer under which conditions. In this presentation we will show work on matching spatial descriptions to haptic object configurations. In a recent experiment a large group of sighted, blind and visually impaired participants (> 200) gave ratings on the acceptability of a number of verbal statements (e.g. the ball is above the shoe) in relation to object relations which were haptically explored. Interestingly, the blind more often choose an object centered reference frame (i.e. the shoe) than the sighted and visually impaired, who were as likely to pick a relative reference frame (own body). We argue that this reflects a stronger reliance in the blind on the functional relationship between haptically explored objects. Employing a more complex haptic object display in a separate study (Postma et al., 2007), we observed blind to more often give object centered descriptions of the display, whereas sighted more frequently used board oriented descriptions. We will discuss these findings in terms of how blindness affects reference frame processing in language and perception
SY_22.4 - Cross-modal plasticity and functional specialization in the “visual” cortex of early blind humans
Renier, L. & De Volder, A. G.
Institute of Neuroscience, Neural Rehabilitation group, Université catholique de Louvain, Brussels, Belgium
It is now established that the elevated metabolism in the deafferented “visual” cortex of congenitally blind adults has a physiological significance. Despite numerous studies on cross-modal brain plasticity, still little is known about how their “visual” cortex is functionally organized. On the one hand, several occipital regions in blind subjects seem quite indifferently recruited in various experimental conditions (tasks and stimuli), which led some authors to propose that this activation is nonspecific and serves a general purpose. On the other hand, numerous studies brought evidences of the existence of functional specializations in the occipital cortex of blind subjects. Using functional brain imaging (PET and fMRI) we monitored the brain activity in early blind and sighted control subjects while they were involved in various tasks including spatial imagery, mental imagery of object shape, auditory motion processing, localization of auditory and vibrotactile stimuli as well as during the use of a visual-to-auditory sensory substitution device to perceive 2D geometrical figures, schematized faces and houses. In total we brought evidences in favour of a preserved functional specialization within the ventral and dorsal “visual” streams in early blind subjects. In addition we recently observed that the occipital cortex was involved in the processing of odours in early blind subjects and that olfactory and auditory-verbal processing was segregated in their reorganized cortex. This leads us to conclude that there is a functional specialization in the occipital cortex of early blind subjects: sensory modalities are to some extent segregated in this reorganized cortex and the “visual” streams seem to develop their designated functional role in processing spatial and nonspatial stimuli regardless of visual experience
SY_22.5 - The effects of visual impairments on the representation of peripersonal space: Spatial and numerical leftward biases in bisection tasks
Cattaneo, Z. 1 & Vecchi, T. 2
1 Department of Psychology, University of Milan-Bicocca, Italy
2 Department of Psychology, University of Pavia, Italy
Individuals typically show a leftward bias - known as pseudoneglect - in bisecting physical lines as well as numerical intervals. We found that congenitally blind individuals show such leftward bias in haptic as well as in numerical bisection (thus reflecting the spatial nature in which numbers are represented, the mental number line). These findings support the view that pseudoneglect operates at a mental representational level rather than being perceptually-based. Moreover, the consistent leftward bias shown by blind individuals in both line and numerical bisection suggests that the right hemisphere dominance in spatial processing, resulting in an overestimation of the left side of space, develops even in the absence of any visual input. Further, monocular and strabismic individuals were also tested and the pattern of performance was less consistent suggesting that an imbalance between the inputs from the two eyes may have a different impact compared to blindness on the development of attentional spatial mechanisms.