John O’Keefe
What the Rodent Hippocampus Can Tell Us About Spatial Language
Speaker: John O'Keefe, PhD, University College London
On the assumption that language did not appear de novo with humans, we can ask whether our current understanding of brain function in lower mammals provides us with clues about the biological underpinnings of some aspects of language. One fruitful approach is suggested by our understanding of the mechanisms of spatial memory and navigation instantiated in the rodent hippocampus. We know from work on patients with unilateral hippocampal lesions that the left hippocampus is involved in memory for narratives and other verbal material. In vector grammar theory, I explore how our current models of the rodent cognitive map suggest how processes there might underpin some aspects of grammar, in particular those carried by the prepositions, and the case structure of some languages. The hippocampal cognitive map provides the animal with a cognitive representation of its environment which supports three different aspects of spatial behavior: it identifies the animal’s current location in a familiar environment, the contents of places including rewards and punishments, and provides a mechanism for supporting flexible navigation from any place in the environment to any goal location. An important feature of these representations and capacities is the use of vector fields in their construction, retrieval, and manipulation and it is this feature I will use to think about human spatial language. I will argue that the meanings of most of the prepositions which are common features of most languages can be represented by aspects of vector fields. To take one example, the prepositional phrase “ from place x to place y” can be represented by the summation of two vector fields, the “ from” by a divergent vector field with all the vector tails originating in x, and the “to” by a convergent vector field with all its vector heads terminating in location y. Furthermore, the case structure of many languages lends itself to a similar analysis with different cases denoting different relationships to the vector field. To take an example, in Latin the ablative case identifies the object of the preposition “from”, and therefore would identify the name of the place or object at the origin of a divergent vector field while the accusative case represents the object of the preposition “to” and would similarly identify the name of the place or object at the head of a convergent vector field. Finally, I acknowledge that spatial language is only a small part of language and will say a few brief words about the extension of the basic spatial language to other non-spatial realms by the use of metaphors in the manner of George Lakoff.
About John O'Keefe
John O’Keefe FRS is Professor of Cognitive Neuroscience at the Sainsbury Wellcome Centre, a member of the Cell and Developmental Biology department at University College London, and a Principal Research Fellow of the Wellcome Trust. He was awarded the Nobel Prize in Physiology and Medicine in 2014.
He is interested in the role of the hippocampal formation of the temporal lobe in spatial and episodic memory, and navigation. He discovered that hippocampal pyramidal cells in the rat respond selectively to an animal’s spatial location and proposed that these ‘place cells’, and the hippocampal system more generally, functions as a cognitive map underpinning spatial localization and navigation. In 1993, he discovered phase precession, the coding of location by the timing of place cell spiking relative to the hippocampal theta rhythm, still the best evidence for neural coding by spike timing. With Neil Burgess and Eleanor Maguire, he showed how the cognitive map theory could be used to understand the role of the human hippocampus in navigation and episodic memory.
In current work, his group is studying how the cognitive map supports flexible navigation to a goal in a familiar environment using vector fields. He is also investigating how this vector field model can be used to underpin some aspects of spatial language with particular attention to prepositions and case endings.