6.2 Adaptive systems, slow and fast.

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Concentric organisation is designed to maintain plasticity of the otherwise stable memory system: we need fast and slow systems that interact with each other. An attentional system keeps stable representations of familiar features of the environment. A (faster) orienting subsystem responds to novelty and resets the attentional system when a new and unfamiliar event occurs. The system's hierarchy is acting in opposite directions: bottom-up input patterns are compared with active top-down feature patterns. This is one of the claims of Grossberg's Adaptive Response Theory.

What happens in learning is that there is coupling of slow and fast responding parts of the central nervous system (CNS). The slower system drives the action of the faster system. The drive system transmits the genetic and other stable information from the core of the organism towards the more outer layers which receive their information from the environment. The drive system sets the parameters which the faster executive system is implementing. This is the neurophysiological base of the "two-factor" theory of learning.

Sometimes the immune system, acting as a physiological drive, initiates a behavioural sequence. Suppose you have been infected by a virus and run a fever: the body thermostat is set higher (factor 1, the autonomous system) and your motor system is instrumental in attaining the new temperature level, by shivering, by pulling up the blanket, by asking for an extra blanket: note that the use of language and speech will help to raise one's temperature and that language is instrumental (factor 2, the sensomotor system) in supplementing a regulatory function! The immune system responds more slowly than the vegetative regulatory system and is connected to the CNS via the autonomous/neuro-endocrine system (time-window to the right in Map 4.4.2). The immune system, a hidden factor in the learning hierarchy, watches over the individuals' physical health and integrity. Note the difference in the time constant of the response systems, as expressed in days, hours, minutes, seconds and fractions of seconds. The time constant, as defined earlier, is a measure of the time a system needs to resume it's stability when its equilibrium has been disturbed. Just as in the neural system, there are slow and fast responding subdivisions in the immune system: the cellular responses oscillating in a slower rhythm than the humoral responses. These responses are mutually dependent.

In living systems equilibria are maintained in a dynamic fashion: oscillating around a mean value. This makes them sensitive to stimuli from their immediate environment, and by responding they in turn exert influence on neighbouring systems. Living systems interact with each other and, by coupling into networks, gradually grow more complex (Pringle 1951, 1968). Such interactions are at the root of societal growth (language, organisations, institutions) , of development (interaction of cells and messenger molecules) and learning (oscillatory loops between neurons).

Another example of the continuity of systems: the immune system has a role in shaping the functions of the brain in a very early stage of development. The directing influence of the immune system has been explored especially with regard to cognitive functions and language. An intriguing finding is that in many dyslectic families and in about 20 % of our stuttering population, an (atopic) predisposition for hyper-reactivity to common allergens has been shown to exist and may have influenced the course of the disorders (Map 18).

6.3 Meaning is a learned cognitive attribute.