Chapter 2 Understanding Cognition Through Functional Connectivity

With every word that you read on this page, your brain orchestrates a symphony of electrical sounds – millions of neurons perform at the same time and billions of synapses coordinate their sounds. If you make yourself a break and start preparing a coffee, a new array of neural musicians will become active. While we know right now quite well how these functions that you perform are segregated in the brain – that is, which set of neurons activates to enable your reading and which to make you remember where you put the coffee jar – it still remains a challenge to understand how the brain integrates separated tasks into a coherent function. How does it happen that the letters form a word in your mind and the words form a meaningful sentence? How do you coordinate the movement of your hands when you reach for the cup with one and for the coffee pot with the other? New tools made available by complexity sciences – the modern network theory – give us a unique chance to describe and measure the integration of information in the brain that is crucial for any function it performs. It has been a century now since we learned that the brain is a network. In the beginning of the twentieth century Santiago Ramon y Cajal ended a long standing debate on whether the neural system is composed of separate cells or a continuous mass of tissue; with histological imaging y Cajal and Azoulay (1911) proved without doubt that it was the former. These cells communicate with each other at special junction points – the synapses. While a substantial amount of research has been devoted to tracking specific connections and pathways within this web of neurons, the network nature of the brain as such has only recently been subjected to investigation with network tools. Huge advances in brain imaging on the one hand and complex systems tools on the other finally enable us to quantitatively describe – with the precision of formal sciences – the structure and complexity of brain networks. This, in turn, might provide us with an unprecedented insight into the integrative function of the brain. A. Rychwalska Institute for Social Studies, University of Warsaw, Stawki 5/7, 00183 Warsaw, Poland e-mail: izziaczek@yahoo.com A. Nowak et al. (eds.), Complex Human Dynamics, Understanding Complex Systems, DOI 10.1007/978-3-642-31436-0_2, # Springer-Verlag Berlin Heidelberg 2013 21 Information Integration in the Brain The mechanisms of information integration in the brain are crucially important for our understanding of the biological basis of cognition and – more generally – the mind. Our phenomenological, subjective experience of cognitive function involves different levels of organization of processes. For example, the process of recognition starts with the combination of tiny perceptual inputs into meaningful shapes. These are then organized into bigger wholes – objects – that, in turn, may be mentally juxtaposed against stored memories about both episodic encounters with similar items as well as encoded semantic knowledge. A vital part in this process is the formation of functional units at different levels of description which, once assembled, can be operated upon without the need of analyzing their parts. That is, once a group of lines form a mental representation of a chair – a functional unit of a higher level – we do not need to operate any longer on single lines. Similarly, if the chair and all other furniture along with its placement become integrated into the mental dining room we can proceed to thinking about the family dinner without any need of disassembling the picture. Clearly, mental processing depends to a large degree on organizing items into functional units. Even more importantly, our stream of consciousness undergoes a similar process. Single thoughts are organized into opinions, emotions, attitudes, memories, etc. which then become plans, schemas, narrations that – at the highest level – form the self. If the brain is the source of cognition, consciousness and the mind, there needs to exist neural mechanisms that provide for an analogous process of functional integration of information processing. The anatomical structure of the brain is functionally segregated. That is, we can establish which regions – brain structures or areas – are selectively activated in the course of a specific function. In particular, the early perceptual regions are precisely mapped with regard to their function. For instance, in the primary visual cortex cortical columns are tuned to respond (by increasing the frequency of action potentials they produce) to very well defined stimuli in the visual field, e.g. gratings at specific angles (Hubel and Wiesel 1968). In areas that are further along the information processing pathway – secondary visual cortex or multimodal cortex – these preferences become more complex to combine information incoming from various other regions. Thus, the activation that spreads through the cortex from the external, perceptual input engages more and more functionally specific structures. Complex cognitive tasks activate a large set of brain regions to combine many functions to meet the demands of the task. While this segregation of function seems intricate enough to accommodate even composite cognitive processes, there still remains a question of how all this segregated information becomes integrated into coherent representation upon which we perform cognitive functions. The most prominent – almost implicit – approach to information integration in the brain assumes that the mere act of transferring impulses from functionally specific areas to other, more complex ones, constitutes integration. That is, if a color specific region together with a shape specific region send impulses to a color 22 A. Rychwalska