Ecolocación humana: Revisión histórica de un fenómeno particular - Segunda parte / Human echolocation: Historical review of a particular phenomenon - Second part

La ecolocación es una habilidad que usaría inconscientemente la mayoría de las personas. Resulta crucial para la movilidad independiente de la persona ciega e implica utilizar sonidos autoproducidos y sus reflexiones para localizar y reconocer objetos que no se ven. Dos nuevos paradigmas han enriquecido el estudio de esta sorprendente habilidad: el del acoplamiento sensoriomotor y el de la sustitución sensorial. El primero sostiene que los sistemas perceptivo y motor constituyen procesos acoplados que requieren un insoslayable tratamiento unificado. El segundo considera que es posible ver con los oídos o con la piel en virtud de la plasticidad cerebral. En esta segunda parte se presenta la temática en el contexto teórico de la cognición corporizada y de recientes avances en neurociencias; se desarrollan además los estudios realizados en el tercer período. En esta revisión se reflejan cambios paradigmáticos en las ciencias del comportamiento y el valor científico acrecentado de la ecolocación humana.

Echolocation is an ability that can be used daily by human beings, even without being conscious of it. It turns out to be crucial to the efficient independent mobility of the blind person, an aspect that is severely affected by blindness. It implies using the information that emerges from self-produced sounds and their reflexions in order to locate and recognize unseen objects. According to the new cognitive and ecological paradigms in perception, it is believed that the primary function of the auditory system is to determinate, i.e., to localize and recognize, the characteristics of the sound source through the sounds emitted by it. Within this context, it has been very recently argued that echolocation (i.e., the ability to locate and recognize biologically relevant secondary sound sources through the information contained in the direct-reflected couple) is a variant of that general process of primary sound sources determination. Two recently established scientific paradigms have specially enriched the study of this amazing ability: the sensorimotor contingency theory and the sensory substitution perspective. The first approach claims that the perceptual and motor systems are coupling processes that demand a thoroughly unified treatment. The second approach considers that, for example, vision loss does not mean loss of the ability to see since it is possible to see with the ears or the skin. The central idea is that the information usually captured by vision may instead be captured by touch or audition, on account of brain plasticity. In this way, in echolocation (which represents a kind of 'seeing with the ears' natural sensory substitution system that is part of the human endowment) action consists of the exploratory activity that the subject carries out through self-generation of sounds and head and/or cane movements while sensation refers to certain tonal or spatial percepts related to the presence and characteristics of the objects that the subject (implicitly) learns to perceive probably as auditory Gestalts. In the first part of this article the main theoretical aspects and a revision of the studies throughout two of the three delimited periods were developed: FIRST APPROACHES (1700 - 1935) and SIENTIFIC STUDY OF HUMAN ECHOLOCATION (1940 -1980). The questions that researchers formulated during these periods were firstly concerned with discovering if blind persons actually possessed this ability, which of the sense organs was involved and which sensory stimulation was its necessary and sufficient condition. Secondly, they inquired into the scopes of echolocation and its possible underlying psychoacoustic mechanisms. The thorough investigations carried out allowed to unequivocally establishing that audition is the sensory basis of this ability and that changes in pitch are its necessary and sufficient condition. It was also demonstrated that not only blind subjects but also appropriately trained sighted subjects were able to precisely localize and recognize the characteristics of the experimental objects. In this second part, we present the object of study within the context of theories of embodied cognition and recent developments in the field of the neurosciences; we also elaborate upon studies carried out during the third period, named RECENT STUDIES, that extends from 1990 to present days. We show how the blind person with good echolocation ability becomes an excellent experimental model to study behavioral and neurophysiological aspects involved in implicit learning. The article illustrates the paradigm shifts that occurred in recent scientific history through the study of this particular human ability that, within the mentioned recent theoretical context, has acquired a renewed interest.

Future developments in brain-machine interface research

Neuroprosthetic devices based on brain-machine interface technology hold promise for the restoration of body mobility in patients suffering from devastating motor deficits caused by brain injury, neurologic diseases and limb loss. During the last decade, considerable progress has been achieved in this multidisciplinary research, mainly in the brain-machine interface that enacts upper-limb functionality. However, a considerable number of problems need to be resolved before fully functional limb neuroprostheses can be built. To move towards developing neuroprosthetic devices for humans, brain-machine interface research has to address a number of issues related to improving the quality of neuronal recordings, achieving stable, long-term performance, and extending the brain-machine interface approach to a broad range of motor and sensory functions. Here, we review the future steps that are part of the strategic plan of the Duke University Center for Neuroengineering, and its partners, the Brazilian National Institute of Brain-Machine Interfaces and the École Polytechnique Fédérale de Lausanne (EPFL) Center for Neuroprosthetics, to bring this new technology to clinical fruition.

O aprendizado da utilização da substituição sensorial visuo-tátil por pessoas com deficiência visual: primeiras experiências e estratégias metodológicas / The learning of the use of the tactile-vision sensory substitution by people with visual disability: first experiences and methodological strategies

O sistema de substituição tátil-visual (TVSS) é uma tecnologia assistiva criada para ajudar deficientes visuais a perceberem aspectos visuais de seu ambiente através do tato e contribuir para sua inclusão social. Para melhor entender o processo de aprendizagem dessa tecnologia, quatro participantes cegos foram treinados com o Brainport®, a última versão do TVSS, onde imagens visuais transformadas são exploradas pela língua. O artigo objetiva de investigar o estágio inicial desse processo de aprendizagem, em termos tanto do desempenho dos participantes quanto da qualidade de sua experiência. O treinamento, conduzido de acordo com um método clínico-pedagógico, produziu dados em terceira pessoa e em primeira pessoa. Os dados foram obtidos através de registros de desempenho e de entrevistas de explicitação. Os resultados mostram que as maiores dificuldades surgidas foram relativas ao acoplamento sensório-motor, aos movimentos do corpo e da cabeça e à dissonância entre as expectativas e a qualidade da experiência perceptiva.

The tactile-vision-substitution-system (TVSS) is an assistive technology designed to aid the visually impaired in perceiving visual aspects of their environment located beyond touch. In order to better understand the learning process of that assistive aid, we trained four blind participants with the Brainport®, the last version of the TVSS, where the transformed visual images are explored by the tongue. More specifically, this article aims to investigate the initial stage of this learning process, in terms both of participants' performance and their qualitative experience. The training, conducted according to the clinical-pedagogic method, produced data both from the first-person and the third-person point of view. Data were gathered through records of participants' performance and explanation interviews. Results show that the main difficulties arising during the process concerned sensory-motor coupling, body and head movement, and the gap between actual and expected quality of the perceptual experience.