Publications

Abstract

People with grapheme-colour synaesthesia experience colour for letters of the alphabet or digits; A can be red and B can be green. How can it be, that people automatically see a colour where only black letters are printed on the paper? With brain scans (fMRI) I showed that (black) letters activate the colour area of the brain (V4) and also a brain area that is important for combining different types of information (SPL). We found that the location where synaesthetes subjectively experience their colours is related to the order in which these brain areas become active. Some synaesthetes see their colour ‘projected onto the letter’, similar to real colour experiences, and in this case colour area V4 becomes active first. If the colours appear like a strong association without a fixed location in space, SPL becomes active first, similar to what happens for normal memories. In a last experiment we showed that in synaesthetes, attention is captured by real colour very strongly, stronger than for control participants. Perhaps this attention effect of colour can explain how letters and colours become coupled in synaesthetes.

Abstract

Marieke van der Linden investigated the neural mechanisms underlying category formation in the human brain. The research in her thesis provides novel insights in how the brain learns, stores, and uses category knowledge, enabling humans to become skilled in categorization. The studies reveal the neural mechanisms through which perceptual as well as conceptual category knowledge is created and shaped by experience. The results clearly show that neuronal sensitivity to object features is affected by categorization training. These findings fill in a missing link between electrophysiological recordings from monkey cortex demonstrating learning-induced sharpening of neuronal selectivity and brain imaging data showing category-specific representations in the human brain. Moreover, she showed that it is specifically the features of an object that are relevant for its categorization that induce selectivity in neuronal populations. Category-learning requires collaboration between many different brain areas. Together these can be seen as the neural correlates of the key points of categorization: discrimination and generalization. The occipitotemporal cortex represents those characteristic features of objects that define its category. The narrowly shape-tuned properties of this area enable fine-grained discrimination of perceptually similar objects. In addition, the superior temporal sulcus forms associations between members or properties (i.e. sound and shape) of a category. This allows the generalization of perceptually different but conceptually similar objects. Last but not least is the prefrontal cortex which is involved in coding behaviourally-relevant category information and thus enables the explicit retrieval of category membership.

Abstract

This thesis investigates the processing of words written in Japanese kanji and Chinese hànzì, i.e. logographic scripts. Special attention is given to the fact that the majority of Japanese kanji have multiple pronunciations (generally depending on the combination a kanji forms with other characters). First, using masked priming, it is established that upon presentation of a Japanese kanji multiple pronunciations are activated. In subsequent experiments using word naming with context pictures it is concluded that both Chinese hànzì and Japanese kanji are read out loud via a direct route from orthography to phonology. However, only Japanese kanji become susceptible to semantic or phonological context effects as a result of a cost due to the processing of multiple pronunciations. Finally, zooming in on the size of the articulatory planning unit in Japanese it is concluded that the mora as a phonological unit best complies with the observed data pattern and not the phoneme or the syllable

Abstract

This study investigates the morphological and morphosyntactic characteristics of hand configurations in signs, particularly in Nederlandse Gebarentaal (NGT). The literature on sign languages in general acknowledges that hand configurations can function as morphemes, more specifically as classifiers , in a subset of signs: verbs expressing the motion, location, and existence of referents (VELMs). These verbs are considered the output of productive sign formation processes. In contrast, other signs in which similar hand configurations appear ( iconic or motivated signs) have been considered to be lexicalized signs, not involving productive processes. This research report shows that meaningful hand configurations have (at least) two very different functions in the grammar of NGT (and presumably in other sign languages, too). First, they are agreement markers on VELMs, and hence are functional elements. Second, they are roots in motivated signs, and thus lexical elements. The latter signs are analysed as root compounds and are formed from various roots by productive processes. The similarities in surface form and differences in morphosyntactic characteristics observed in comparison of VELMs and root compounds are attributed to their different structures and to the sign language interface between grammar and phonetic form