"Theorizing about brain functions is often considered slightly
disreputable and anyhow a waste of time -perhaps even 'philoso- ical'" 1
P. S. CHURCHLAND At present there are no unanimously accepted general
con- cepts of brain operation and function. This is especially the case
with regard to so-called "higher" functions such as per- ception, memory
or the coupling between sensory input and motor output. There are a
number of different reasons for this. Some may be related to
experimental limitations allowing the simultaneous recording of the
activities of only a restricted number of neurones. But there are also
conceptual difficulties hindering the transition from "single-neurone"
schemes, in which neurones are assigned relatively specific tasks (such
as feature detection), to more complex schemes of nerve cell as-
semblies (for a discussion of some of the difficulties see Abeles 1982;
von der Malsburg 1981; Kriiger 1983). Whilst much is known about the
basic properties and functions of single neu- rones, whose operations we
hope to understand in the foresee- able future, this does not hold true
in the same way for the working of large assemblies of neurones.