Memory as Prediction by Tomaso Vecchi & Daniele Gatti

Author:Tomaso Vecchi & Daniele Gatti [Vecchi, Tomaso & Gatti, Daniele]
Language: eng
Format: epub
Publisher: MIT Press

10 Cerebellar Functions

Several findings have shown a cerebellar involvement in motor, emotional, cognitive, and perceptual processes (for reviews, see Adamaszek et al., 2016; Baumann et al., 2015; D’Angelo & Casali, 2012; Koziol et al., 2014; Manto et al., 2012; Mariën et al., 2014; and for a general discussion, see D’Angelo, 2019). As discussed earlier, the cerebellar involvement would consist in the execution of one same basic function, and this is in line with the homogeneity of the cerebellar structure. In general, several basic functions have been linked to the cerebellum, such as sequencing, internal models, or timing (for review and experimental evidence, see Breska & Ivry, 2016; Ebner & Pasalar, 2008; Leggio & Molinari, 2015; Tedesco et al., 2011; Wolpert et al., 1998). These concepts can be seen as subunits that are part of a single higher-order process, such as the prediction of events. This function would be performed through a type of feedforward control, that is, the anticipation of the consequences of an operation and the subsequent comparison between what was predicted and what actually occurred, in order to improve the adaptation to the environment. As argued by D’Angelo and Casali (2012, pp. 8–9), “The cerebellum may take part in cognitive control by regulating executive functions, which it could do by manipulating different ‘objects.’ These can be considered parts of a set of virtual representations, given that they may be purely symbolic (e.g., thoughts) or applied to symbolic expression (e.g., speech) or voluntary movement (which, after all, is based on a virtual representation of its sensory consequences).” In one word, the principal function of the cerebellum appears to be the automation of a given function (e.g., Albus, 1971; Ito, 1990, 2011; Marr, 1969).

The terms forward and feedforward are used to refer to the same general concept, and the first is associated with the term model and the second with control. In the literature, the opposite of a forward model is called an inverse model: “A forward model transforms a motor command into a prediction of its outcome in terms of the sensory reafference the movement will generate, i.e., the sensory consequences of the movement. In contrast, an inverse model computes the motor command that is required to achieve the desired state change of the body. Thus, in terms of information flow, the inverse model is the inversion of the forward model” (Ishikawa, Tomatsu, Izawa, & Kakei, 2016, p. 72). The opposite of feedforward control, however, is feedback control: the former coordinates activity based on what is expected to happen, whereas the latter does this based on what has actually happened.

This can be further simplified with the example of an action, such as drinking from a cup. The inverse model dictates which actions are necessary to perform this action successfully (moving the arm, grasping the cup, bringing it to the mouth, etc.); the feedforward controller, through forward models that refer to this given movement, creates a prediction of what can be expected in each moment and coordinates action based on

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