- 1-1 Introduction
- 1-2 Decomposition and Reconstruction
- 1-3 Neurons and Synapses
- 1-4 Neural Networks
- 1-5 Systems Control Mechanisms in the CNS
- 1-6 Reflexes and Voluntary Movements
- 1-7 Integration of reflexes
- 1-8 Motor Actions
- 1-9 Cognitive Functions
- 1-10 Beyond Movements
- 1-11 Scope of This Monograph
- 1-12 Summary
1-10 Beyond Movements
Figure 8, which shows model-based control system designs, may be referred to for considering a mental model as a controlled object. For the present, computer simulation cannot reproduce this model because it lacks a computational basis. This difficulty is like the one that arose in the field of artificial intelligence. More than 50 years ago, a group of computer scientists proposed a study that would "... proceed on the basis of the conjecture that every aspect of learning or any other feature of intelligence can in principle be so precisely described that a machine can be made to simulate it." These scientists were eager to make "... an attempt to find how to make computers that use language, form abstractions and concepts, solve kinds of problems now reserved for humans, and improve themselves" (McCarthy et al., 1955). This tempting approach in artificial intelligence, however, remains unsuccessful because it lacks the clarification provided by neural network mechanisms that can encode a concept or a specific piece of knowledge.
Another profound question is how the operation of a neuronal circuit can be undertaken with conscious awareness. Sigmund Freud (1856–1939) and many more recent researchers have emphasized that only a few of the activities of the CNS are executed consciously. For example, one cannot bring to conscious awareness the thought processes involved in improving motor skills (e.g., skiing) by training (non-declarative memory). In contrast, one can readily recall cognitive experiences (declarative memory) (Squire, 2009). In other words, the neuronal circuits implicated in non-declarative memory are remote from the mechanisms of conscious awareness, whereas those involved in declarative memory are closely connected to conscious awareness. On the other hand, it has been shown that electric or transcranial magnetic stimulation (TMS) of the neocortex usually evokes vivid sensations or perceptions (Penfield and Perot, 1963; Coway and Welsh 2001), whereas stimulation of the subcortical tissues of the cerebellum (Riklan et al., 1976; Koch et al., 2006) and basal ganglia (Chen et al., 2006) has no impact on conscious awareness. Conventionally, intelligence has been considered to require consciously activated cortical functions, but a substantial part of it is probably exerted subcortically and consequently unconsciously. In fact, intuitive thought is an important part of intelligence, but it is exerted unconsciously without obvious reasoning (Chapter 17).
Neuroscience has reached a level of sophistication that is on the verge of addressing neural mechanisms underlying intelligence and conscious awareness. It seems likely that research on the cerebellum will be on the forefront of this endeavor.