Successful reading requires the brain to correctly recognize printed individual words. It has been proposed that single-word reading can be viewed as a special case of visual object recognition with its dual goals of achieving specificity and invariance. This hypothesis allows us to leverage theories of object recognition to provide hypotheses for the neural bases of single-word reading, in particular the nature of the representation of visual words, how this representation is shaped by expertise, and is modulated dynamically by attentional effects.
The specific aims of this proposal are to a) determine the impact of top-down attentional factors on single-word reading related activation, b) probe the selectivity of neurons in the VWFA and c) determine how word frequency affects the neural representation in the VWFA. To disentangle feed forward and top-down attentional components, we will use the masked priming technique, which has been widely utilized to examine single word reading. In this paradigm subjects are not consciously aware of the prime yet numerous behavioral studies show priming effects. We will combine this behavioral technique with functional MRI. Imaging studies of masked words show neuronal activation that is isolated mostly to visual areas indicating that subjects do perceive the stimuli. However, only so much can be gleaned from the BOLD response. Recently, a technique called repetition adaptation has been used to study neuronal tuning. Studies show that the repetition of a stimulus will result in reduced activation, which is thought to reflect a population of neurons specialized to process that stimulus. Recovery from adaptation corresponds to a change in the population of neurons processing the stimuli. Strong preliminary data suggest that this effect will not only allow us to probe neuronal tuning more directly, but also provide a better mechanistic model of how performance in reading tasks is based on neuronal tuning properties. The technique proposed in this project provides an innovative way to examine the neural correlates of single word reading in the occipitotemporal cortex. The relevance of this work for public health lies in its direct applicability to the study of reading disorders, whose underlying neural causes are still poorly understood. For instance, people with dyslexia often show altered reading-related activation in occipitotemporal cortex. The proposed project's aim to use advanced brain imaging and parameterized behavioral techniques to more directly probe the neuronal bases of activation in this area will provide a framework that in a next step can be applied to examine disordered reading, eventually leading to better detection, diagnosis, and treatment of reading disabilities. ? ? ?
| Glezer, Laurie S; Jiang, Xiong; Riesenhuber, Maximilian (2009) Evidence for highly selective neuronal tuning to whole words in the ""visual word form area"". Neuron 62:199-204 |
