Submitted by Administrator on Wed, 04/12/2013 - 09:57
New research from the Centre for Speech, Language and the Brain at the University of Cambridge reveals key differences in how the meanings of words and objects are processed in the brain.
The study is published in this week’s issue of Journal of Neuroscience.
When people view an object in the world (such as a hammer, or a tiger) what they see is not merely a meaningless shape. Instead, we recognize the object and access semantic information about it (we know that a hammer is a kind of tool, a tiger is a dangerous wild animal, and so on). Similarly, when we read a word (such as the word “hammer”, or the word “tiger”) we understand the meaning of the word in order to make sense of what we are reading. Using functional magnetic resonance imaging (fMRI), this study addressed the fundamental question of whether we access meaning in the same way for words and objects.
In the study, researchers asked the participants to view a series of 60 words, followed by 60 pictures which showed the same objects referred to by the words. For both the words and the objects, the participants simply had to say the kind of thing that each word or object was (so, for both the word “tiger” and the picture of the tiger, they would say “animal”).
The researchers were interested in which regions of the brain would show similar patterns of activation for the words and pictures.
Critically, in this study the goal was not to simply identify regions of the brain that were involved in processing the meaning of both words and objects. Instead, the aim was to investigate whether the kinds of representations being processed in a given region were the same for words and pictures. In order to achieve this, the researchers used a technique called representational similarity analysis, which allowed them to directly compare the fMRI activation patterns for words and objects.
Dr Barry Devereux, of the Centre for Speech Language and the Brain and lead author on the study, said: “We know from previous studies that some regions are involved in semantic processing for both words and objects. What representational similarity analysis allows us to do is investigate whether this common activation is really evidence of invariant semantic processing. It is possible for a region to be involved in both word and object processing, but to perform different functional roles in the two modalities”.
Senior author and Principal Investigator Professor Lorraine K. Tyler added “This research is an important step forward in understanding the ways in which the meaning of objects and words – which form the basis of our ability to represent the world around us – is processed in the brain”
The results showed a complex pattern of similarities and differences in processing words and objects. Some regions are invariant: the activation patterns are similar for objects and words. However, other regions show very different activation patterns depending on whether words or objects are being viewed, even though these regions are activated for both words and objects.
These findings have important consequences for research into how people process meaning, by showing that merely identifying the regions involved in both word and picture processing is not sufficient evidence that they form part of a common semantic network. The actual patterns of activation within a region can vary as a function of whether the visual input is a word or an object.
Barry Devereux
Senior Research Associate at the CSLB