News from EBBS membership

 

Knighthood for Cambridge Neuroscientist Gabriel Horn

Recently we received a happy email message from our President, announcing that long-standing EBBS member Gabriel Horn had received a knighthood in the New Year's Honours. Wolfram Schultz listed Sir Gabriel Horn's many achievements, including appointment as Professor of Zoology, at  the  University   of Cambridge, in 1977, where he was Head of the Department of Zoology from 1979-1994; election as  Fellow of the Royal Society in 1986; Master of Sidney Sussex College, Cambridge, from 1992-1999; and recipient of the Royal Society Royal Medal in 2001.   

 

   The knighthood was awarded 'For services to neurobiology and to the advancement of scientific research', and therefore I will focus on his scientific achievements. 

 

They are many, and in a number or different scientific disciplines. Gabriel Horn has played a pioneering role in these part-centred visual receptive fields, multisensory integration, attention  and perceptual predispositions. Pioneering work is not immediately universally accepted, and Horn's studies are no exception. For instance, he was the first to demonstrate that neurons in the superior colliculus-the optic tectum- received inputs from the auditory and somatic sensory systems. This work was initially received with some scepticism, but it is gratifying to see that contemporary research has completely vindicated and extended Horn's original results (see, e.g.,  contributions in Bolhuis, 2000).  Horn also pioneered the study of neuronal habituation, the characteristics of which he compared to those of behavioural habituation. As long ago as 1970 he suggested that the failure of synaptic transmission during habituation involved changes in the movement of calcium ions on the presynaptic side of the synapse. Horn's pioneering work on habituation involved a wide range of species, including cephalopods, insects and mammals (Horn, 1985, 2000).

 

 

Sir Gabriel and his collaborators have also been pioneers in attempting to localize the neural substrate of memory (Horn 1985, 2000). The argument is that, in order to be able to analyse the neuronal correlates of learning and memory, you have to know where in the brain to look for these correlates. A well known attempt at localization of function was that of Karl Lashley  in the 1950's, who was 'in search of the engram', the engram being the 'mark' or 'trace' left in the brain by the learning experience. As we all know, Lashley became despondent with regard to neural localisation of the memory trace. Horn and his colleagues took up the challenge through an analysis of filial imprinting. They established that the neuronal changes underlying this form of learning are not widely distributed in the brain, but are subserved by at least three brain regions, including the left and right Intermediate Medial Hyperstriatum Ventrale (IMHV). Neuronal changes consequent upon training have been identified in the left and right IMHV, but are different in the two regions.  Horn has been able to show that the changes which bring about strengthening of connections between specific groups of neurons in learning and memory are diverse, involve anatomical and biochemical changes, and occur with differing time courses. Sir Gabriel's work on habituation and especially on imprinting have taken us further than any other paradigm towards unraveling the neural mechanisms of learning and memory, a key problem in modern cognitive neuroscience.  

Recently, a number of Gabriel's friends and colleagues honoured him with a collection of essays on the cognitive neuroscience of perception, learning and memory (Bolhuis, 2000). The list of contributors to the book includes many of the top scientists in their respective fields, and it is a great tribute to Sir Gabriel that they were all very keen to contribute  to a book in his honour. Typically, Gabriel was not just a passive recipient of this tribute, but contributed one of the finest chapters to the book (Horn, 2000). Indeed, Sir Gabriel's scientific output is unabated. Only last year he and his colleagues published a very important paper (Horn et al. 2001), challenging  the predominant view that the neural changes underlying memory reflect linear processes such as are implied in simple Hebbian models of memory-related neural plasticity. His carefully controlled, elegant experiments are an example of how this problem should be tackled, and his achievements put him at the forefront of the field. May he lead the way for a long time to come.

Johan Bolhuis Utrecht University