Cognitive Neuroscience Approach and Neuroimaging Techniques

Identifying brain regions, and characterizing their functional role in cognitive and emotional processes, both in healthy, and mentally ill people, is one of the most relevant aspects of neuroscience. When studying the role of these regions, we benefit greatly from the usage of neuroimaging techniques, as they allow us to track on-line brain function, and study the temporal and spatial distribution of activity in distinct brain areas during the cognitive processes under study. Currently, we use two main techniques in the pursuit of our objective: electroencephalography (EEG) and magnetic resonance imaging (fMRI).

These techniques provide information about: a) event-related brain potentials (ERPs), b) time-frequency electroencephalography (wavelet analysis), c) functional magnetic resonance imaging (fMRI) and d) Diffusion Tensor Imaging (DTI). The former two techniques give information about the temporal evolution of different cognitive processes, while the latter two are sensitive to brain area activation during certain tasks, as well as their cerebral interconnectivity. The logic behind our 4 technique based approach can be clearly summarized using Figure 1. The electrical and metabolic activity of a group of neurons can be recorded using an EEG or fMRI. This information, which is represented on the left side of the figure, gives functional information, that is, the activity exhibited by neural groups when performing a certain cognitive task. The right side of the figure shows the structural information of the brain, revealed using MRI techniques. To get an even more detailed image of the brain, we use Voxel Based Morphometry (VBM) as it gives macrostructural information about brain tissues, which we then complement using information from a DTI, which gives us information about the microstructural organization of white matter.

Figure 1

Language Learning and Brain Plasticity

Speech segmentation and vocabulary learning

The aim of this project is to study language acquisition and vocabulary learning, and the neural mechanisms involved. More specifically, this project focuses on the challenges young children face when learning the meaning of words, as well as the similar challenges adults face when learning a foreign language. The ability to learn words is not trivial, and requires at least the ability to infer the intentions of others, the ability to acquire new concepts, an understanding of syntactic structure, and certain general learning and memory abilities (Bloom, 2000; Gomez & Gerken, 2000). Even at its simplest, the acquisition of word meaning involves mapping specific concepts to certain signs or sounds. This mapping is arbitrary, and the same pattern of sounds can correspond to different meanings in different languages.

One of the aims of this line of research is understanding how a new word encountered in a specific context is attached to the mental lexicon in accord with its meaning and syntactic function. In order to simulate how this learning machinery is involved in acquiring the meaning of new words, we will use the human simulation paradigm (Gillette et al., 1999). This paradigm exposes adults or children to different sources of information (linguistic and extralinguistic), which must then be used to create meaning for a new or hidden item. In a sense, the human simulation design provides a model for the problem that frequently occurs when learning a new language. There are at least six clear-cut objectives in this project: (i) how humans and infants are able to assign meaning to nonsense words (pseudowords), (ii) how this learning process changes depending on the class of word (nouns vs. verbs), (iii) differences arising from the concreteness of the word (abstract vs concrete words), (iv) comparing closed vs. open class words, (v) how syntactic information facilitates the process of meaning acquisition, and (vi) the influence of visual and linguistic information on mapping “concrete” vs. “abstract” word meanings. Interestingly, we have also been investigating the neurophysiological mechanisms involved in speech segmentation, which is one of the crucial challenges adult foreign language learners and children must face. A series of new paradigms and studies have been developed in order to investigate the event-related brain responses during the on-line process of speech segmentation.