3. Feature-specific representation and semantic construction in BCI therapy

Yet, the generation of symbolical content is not the only consequence of acquiring temporal independence. The manner in which syntactical elements are assembled is also altered. As cyclical patterns it is only through their modular assemble into larger architectures that they can yield representational variation. Significantly, this change offers the immediacy of parallelbased representation. Hence, the role of syntax as representational sign, that is, as in a symbolical, Peircean coding, is itself transformed, linked instead to semantic elements that duplicate through self-organization feature-specific content of the external world [24]. For BCI, information extraction premised on symbolical articulation alone and not accounting for such modular assembly reduces structural content, diminishing the capacity for representation.

The complexity and magnitude of dynamical variation encountered in the state space of the brain, moreover, is a capacity amenable to environmental exigencies, in much the manner that field-situated robotic artifacts become amenable to local input by transferring responsivity from programmatic architectures to distributed processing. Here, sensorial input can elicit motor responsivity directly, structuring forms that directly respond to molding stimuli [25].

Some of the essence of this process of feature-specific duplication can be seen in the motor image, a covert action that is a representation of a non-executed action. The concept of the motor image itself evolved from several experimental legacies. Classical observations made by Lashley [26, 27] in a subject with a deafferented limb showed that humans, and animals, were able to generate actions without sensorial input, in contrast to the broadly assumed hypothesis prevalent in the nineteenth century. Later, experiments in monkeys showed that with deafferentation of spinal dorsal motor roots the animals nonetheless could execute pointing movements in all the phases of motion [28]. This indicated that the movement was predetermined centrally. How this was done and how executed became apparent in studies of ongoing motion. Held [29] observed that limb movements in such circumstances usually do not correspond to their expected trajectories, but entail a misreaching followed by progressive compensatory movements. To explain his finding he proposed Von Holst and Mittelstaedt [30] hypothesis that the command for the executed movement was stored as an efference copy, sent to the sensory cortex, where it was then compared with the actual movement undertaken so as to correct the misaligned motions. The experimental observation of misalignment and correction seen experimentally served as evidence of the memorized storage. A corollary of this hypothesis was that self-made motions could be contextualized to the individual who initiated the actions, a conclusion drawn by Frith in his comparator model [31, 32]. This is to say that the comprehension of the actions as those of one's own was a necessary feature of movement; while the actions could be initiated without afferences, they nonetheless required them for motor cognitions in order to be understood as self-executed functions.

In continuous motions the sensory cues are coupled to motor execution in a mutually reciprocal and sustained process [33]. This is necessary, since as the body undergoes motion, its spatiotemporal position is continually changing and so also the sensory cues that reference it. While these cues entail contributions from all the senses, those having the greatest influence are of somatotopic origin due to their capacity to delimit the three-dimensional topological perimeter of the body [34]; this is also to say that it is necessary to know where the body is situated in space and time in order to know where next to move it. Linda Smith has described this as a point of criticality, analogous to a phase transition in a material substance, where the body is framed as a stable reference that is transitioning to a fluid and behaviorally flexible state [35].

The validity of this observation, and also as a demonstration of the need to frame the whole body, is well documented in the Piaget A not B error where a young infant continues to perseverate toward an object goal despite having been informed of its prior displacement. This error is explained by the delay in development of maturational processes of the brain needed to formulate and execute goal-directed actions [36]. From these, and other experimental studies, it is intuitive to see why the observed events and processes hypothesized by Von Holst and Mittelstaedt and by Frith require a "predictive processing" to engage motion [37]. Predictions are needed if one is to engage in actions, that is, actions that are intended to be carried out by the self, and are not merely passive responses to external events. Since all external contingencies cannot be known beforehand, like the field-situated autonomous artifact, neither can all consequences of the intended actions. The expectation of the action, its prediction, affords a first approximation that is open to correction that can structure the sequence that follows and that is energetically efficient.

This interplay between predictive actions, goals, and a holistic bodily sense point, further, to the presence, indeed need of mechanisms that involve a simulation of intended actions. Covert actions are thus a motor planning stage needed for subsequent motor execution. In this, the motor image is the key element. The construction of the image, its contextualization to the whole, and its traversal of stability flexibility bifurcations are all basic elements that entail feature duplications of the projected events. That is, they constitute semantic representation of objective events directly and not coded symbols of what is intended.

Hence, at deeper levels, linguistic primitives function as determinants for assimilating semantic content. That is, the assembly of these elements creates the semantic content of what is communicated through the action. For BCI therapy, this expands the role of therapy from interpretive assessment to the construction of semantic form, like that occurring when coupling sensorial input to the elicitation of motor imagery [25]. Here, semantic content is added by combining the specific motions that are undertaken to their semantic representation in the whole form of the individual, a process likely to the precision of motor processing primitives of the cerebellum [38, 39].
