A central component of our mental life is experience; that is, consciousness. You hear the sound and experience a certain quality, a what it is like as the philosopher Thomas Nagel described it. While reading these lines you may experience the feeling of boredom: while I as the author of these lines may see boredom in your face and its expression, I cannot experience your boredom. Hence experience is strongly subjective; that is, it is tied to you as the experiencing person. This distinguishes experience as subjective features from, for instance, the observation of the brain that can be shared by others and is therefore objective rather than subjective.
In contrast to the subjective nature of our experience, the brain and its neural activity are objective. They can be observed by everybody from the outside distinguishing it from experience that occurs only from the inside of a person. Moreover, it seems that experience presupposes a self, a subject of experience where that is not the case in observation of the brain for which no subject or self seems to be necessary. This marks experience and brain almost as opposites: the brain is objective, can be observed, is self-less and remains without consciousness whereas experience is subjective, experiential, self-based, and conscious.
Empirical evidence in neuroscience suggests that experience is somewhat in yet unclear ways related to and based on the brain. This is sometimes described as the neural correlates of consciousness (NCC) which refers to those neural features that must be initiated in order for experience or consciousness to occur. Given the seemingly opposite features of experience and brain, it remains rather puzzling though how the brain and its self-less, nonconscious, and objective neural activity can bring forth or be transformed into experience as self-based, conscious, and subjective. This remains a mystery until now.
In a recent paper, I, with an Italian colleague, Giovanni Stanghellini, address this issue, namely how the brain and its neural activity can be transformed into experience (Northoff and Stanghellini 2016). Specifically, we raise the question how symptoms in psychiatric disorders like schizophrenia that are intrinsically experiential can be linked to the brain and its neural activity. What is the bridge that allows transforming neural activity changes into experiential activity changes? In order for experience to be related to and based on the brain and its neural activity, there must be some kind of bridge or better “common currency” between brain and experience.
Let us describe the situation with a real bridge. The real bridge crosses the gap between two sides of a river which, in an extreme case, may belong to two different countries. By crossing the bridge, one can pass from one country to another.
Moreover, the two countries have different currencies. By entering the one country, one must thus exchange the money of the one country into the one of the respective other. How is that possible? For that, the currencies of both countries are related and compare to a third currency (like the US-dollar as anchor currency) as shared or “common currency."
What now is the bridge and the “common currency” between brain and experience? We suggest that that bridge consists in time and space. The brain and its spontaneous activity continuously construct (or synthesize) temporal and spatial features: temporal features are constructed by the fluctuations of its neural activity in different frequency ranges while spatial features are constructed in terms of the connections between different regions in terms of neural networks. The brain and its spontaneous activity thus exhibit a spatiotemporal structure. We now suppose that that very same spatiotemporal structure that envelops and embeds the processing of specific stimuli or contents allows for constituting experience. Though not observable at a particular point in time and space, experience is nevertheless spatial and temporal in that is based on a virtual temporal and spatial continuum like the “stream of consciousness."
We now suppose that such virtual time and space in experience is based on the virtual spatiotemporal structure of the brain’s spontaneous activity. Experience is thus based on the way the brain and its spontaneous activity construct time and space in a virtual way. If so, time and space provide the bridge and “common currency” between brain and experience.
Want to know more? Read my recent book Neurophilosophy and the Healthy Mind: Learning from the Unwell Brain (Northoff 2016) and my more academic book Unlocking the Brain (Northoff 2014a and b).
Northoff G, Stanghellini G (2016) "How to link brain and experience? Spatiotemporal Psychopathology of the lived body." Frontiers in Human Neuroscience, in press
Northoff G (2016) Neurophilosophy and the Healthy Mind: Learning from the Unwell Brain. Norton, New York
Northoff G (2014) Unlocking the Brain. Vol I Coding, Vol II Consciousness. Oxford University Press, Oxford, New York