Do We Really Need Vision? How Blind People “See” the Actions of Others

Abstract

Observing and learning actions and behaviors from others, a mechanism crucial for survival and social interaction, engages the mirror neuron system. To determine whether vision is a necessary prerequisite for the human mirror system to develop and function, we used functional magnetic resonance imaging to compare brain activity in congenitally blind individuals during the auditory presentation of hand-executed actions or environmental sounds, and the motor pantomime of manipulation tasks, with that in sighted volunteers, who additionally performed a visual action recognition task. Congenitally blind individuals activated a premotor-temporoparietal cortical network in response to aurally presented actions that overlapped both with mirror system areas found in sighted subjects in response to visually and aurally presented stimuli, and with the brain response elicited by motor pantomime of the same actions. Furthermore, the mirror system cortex showed a significantly greater response to motor familiar than to unfamiliar action sounds in both sighted and blind individuals. Thus, the mirror system in humans can develop in the absence of sight. The results in blind individuals demonstrate that the sound of an action engages the mirror system for action schemas that have not been learned through the visual modality and that this activity is not mediated by visual imagery. These findings indicate that the mirror system is based on supramodal sensory representations of actions and, furthermore, that these abstract representations allow individuals with no visual experience to interact effectively with others.

Perspective-taking in blindness: electrophysiological evidence of altered action representations

“…Our results in CBS indicate that when it comes to a simple, intransitive movement with no sound-associated motor representations (Lahav et al 2007;Ricciardi et al 2009), the brain activity that associates with the mental representation of body movements performed by others departs from those evoked during the mental simulation of their own movements and points to a nonmotor strategy in the 3P mode. In sighted subjects, besides the existence of common (mostly sensorimotor) cortical areas activated in 1P and 3P modes, the 3P perspective further recruits the right inferior parietal, precuneus, posterior cingulate, and frontopolar cortex compared with 1P (Ruby and Decety 2001).…”

“…However, recent studies have revealed that the pattern of brain activation emerging from reasoning about mental states based on visual information is similar in congenitally blind and sighted individuals (Bedny et al 2009). Likewise, blind people were shown to determine the actions evoked by sounds by recruiting similar cerebral networks that are activated by action observation in sighted subjects (Ricciardi et al 2009). The authors further suggested that this system is based on supramodal sensory representations of actions that would allow individuals with no visual experience to interact effectively with others.…”

“…Taken together, these results would argue in favor of blindnessinduced, specific changes in sensorimotor representations of actions. Surprisingly, however, people with visual loss early in life were recently shown to code actions evoked by sounds by recruiting cerebral networks similar to those activated by action observation in sighted subjects [Ricciardi et al 2009, but see Alaerts et al (2011.…”

“…It was also proposed at that time that blind subjects might rely on other imagery modalities or use semantic representations to perform these imagery tasks (Zimler and Keenan 1983). However, the way congenitally blind subjects (CBS) represent to themselves another person's action is still controversial (Alaerts et al 2011;Bedny et al 2009;Ricciardi et al 2009). Testing their capacity of imagining an action in 1P vs. 3P mode is thus a probe for the important ability of interacting with someone else's actions and intentions (Jackson et al 2006;Ruby and Decety 2001).…”

Mapping the information flow from one brain to another during gestural communication

“…In the last decade, two parallel lines of research have investigated this question. On the one hand, the finding that some brain regions and neurons involved in performing an action are also active while viewing the actions of others [jointly referred to as the mirror neuron system; MNS (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)] has led to the idea that we understand the actions of others in part by transforming them into the motor vocabulary of our own actions. On the other hand, reflecting on other people's thoughts and beliefs is mediated by another part of the brain, the ventromedial prefrontal cortex (vmPFC; including the anterior cingulate and paracingulate gyrus).…”