Barlow's 1972 Paper

Experiments E D Adrian and his colleagues succeeded in recording from single peripheral sensory nerve fibres in the 1920s, and by 1972 the activity of neurons in most sensory modalities had been studied at several levels up to and including the cerebral cortex. In the original paper this work was reviewed, and an attempt was made to bring out the main implications of the experimental findings. Re-reading this part more than 30 years later, I do not think there is much that is actually wrong or very misleading: there is an unfortunate misprint at the top of page 273 (`̀ explains'' instead of ` èxplores'') that may have concealed my intended meaning from a good many readers, and parts of the section on modifiability overemphasised the instructive as opposed to the selective role of visual experience in determining the properties of adult neurons in visual cortex. In addition, it has now become clear, from the use of awake, behaving animals, that the maintained discharge rates and peak impulse frequencies in cortical neurons are a good deal higher than those commonly found in anaesthetised preparations, and one of the implications of this new evidence will be considered below. There have been many other very important additions to our knowledge of the subject since then, notably in our understanding of extrastriate visual areas (eg Zeki 1978; Maunsell and Newsome 1987), and in correlating single-unit results from these areas with behavioural performance by recording from neurons in the brains of awake, behaving animals performing psychophysical tasks (eg Newsome et al 1989 and later papers in this series). Studies in audition, and especially olfaction, have caught up with those in vision, and shown interesting similarities and differences. But, whereas there really was a revolution in our understanding of the capacity of single neurons as information processors in the years before the article was written, I believe subsequent work has, so far, mainly substantiated these changes. On the other hand, the outlook for the future has changed radically; not only have old techniques for investigating neural activity in the brain been greatly improved and new methods developed, but advances in cell and molecular biology, genetics, and development, seem to guarantee further major revolutions.