Mind-brain dualism has very ancient and controversial origins: today there is agreement in representing, at least in conceptual terms, the mind as the set of psychic and cognitive functions (such as thinking, remembering, perceiving…) and the brain as the biological organ that makes these processes possible through neuronal activity. Some philosophers of the past thought that the seat of the mind was the heart; later, with the spiritualists the idea spread that it was the soul that directed all human cognitive functions. Only since the mid-nineteenth century has an agreement been reached in identifying the brain as unique responsible for our mental processes. Yet, despite this unanimous idea, the questions regarding how the brain generates the subjectivity of an experience, the “internal feeling” and consciousness, still remain open.
The difference between mind and brain from a scientific point of view: “the hard problem of consciousness” and will
Although the mind-brain relationship is still discussed in philosophical terms today, from the second half of the nineteenth century onwards psychologists and neuroscientists began to study it from a strictly experimental perspective, beyond abstract considerations. Initially, the data came frombehavioral observation and from the study ofbrain activity of healthy or injured subjects. Subsequently, the introduction of neuroimaging techniques – such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) – and non-invasive brain stimulation – such as magnetic and transcranial electrical stimulation – made it possible to design experiments that were previously unthinkable. Thanks to these innovations, neuroscientists have precisely mapped the main brain areas, linking them to specific mental functions: Broca’s and Wernicke’s areas to languagethe amygdala to fearthe hippocampus to memory and the limbic system to the regulation of emotions. It is also known that brain damage leads to the alteration or loss of the corresponding mental function, confirming the very close link between mind and brain.
However, what still remains without a satisfactory explanation is how a physical process – like an electrical impulse or a neuronal discharge – can turn into a subjective experiencesuch as feeling pain, feeling love, or having morals. In other words, we know how to describe what happens in the brain when we experience a sensation, but not because that sensation “feels” in a subjective and unique way. Two people can show the same neural activation when smelling the same flower, but the internal perception of the smell – whether pleasant or not, what emotions it arouses – is not scientifically measurable. The same happens with a bitter and hot cup of coffee: the brain areas involved are the same for everyone, but the quality of the experience varies from individual to individual. This subjective dimension of experience, called qualia by the philosopher David Chalmers, represents what he defines as “the hard problem of consciousness“, that is to say the difficult problem of consciousness.
Furthermore, electrophysiological and neuroimaging studies have shown another debated phenomenon: the conscious will to act emerges after the onset of brain activityTherefore before the person becomes aware of their intention. This raises questions about the nature of free will: if our decisions arise from brain processes that precede awareness, the freedom to choose may just be an illusion, as suggested by Benjamin Libet’s experiments.
The relationship between mind and brain: the main scientific theories
Without going into the merits of the numerous theories of the mind, we will focus on those that have attempted to resolve the problematic relationship between mind and brain:
- Neuronal group selection theory (TSGN) – Gerald Edelman: the brain functions as an internal evolutionary system; groups of neurons strengthen or weaken based on experience, creating neural maps that represent body, world and memory. It explains the integration of information, but not why the subjective sensation emerges.
- Mirror neuron theory / embodied mind – Rizzolatti, Sinigaglia: some neurons are activated both when we act and when we observe the actions of others, allowing us to “resonate” with others and promoting, for example, empathy. However, it does not explain why this activation generates internal subjective experience or self-awareness.Emergent theories: Consciousness emerges from the collective activity of neurons, just as the motion of molecules determines temperature. However, it remains unclear how and why this activity gives rise to lived experience.
Furthermore, some schools of thought maintain that any system capable of performing the same functions as the brain can be considered a “mind”, opening up the possibility that consciousness can also be experienced by machinessuch as AI, as well as by humans. In this context, it is worth reflecting on a thought experiment proposed by David Chalmers: imagine a thinking brain in which neurons are progressively replaced by silicon chips that exactly duplicate their functions. As neurons are replaced, would consciousness still be present?
Although the most recent theories describe with ever greater precision the brain mechanisms underlying cognitive and perceptive functions, there is still no exhaustive theoretical framework that explains why and how a brain process produces subjective experience, “feeling something”. Neuroscience describes correlations, but not yet ultimate causes. The phenomenological dimension, that is, the internal and qualitative experience, escapes objective measurements. In summary: the brain is matter that thinks, but how matter comes to think remains one of the greatest mysteries of science.
From the origins to modern science
Before getting to the most “current” cerebral physiologywhich recognizes the brain as responsible for all our cognitive functions, the thoughts of some early philosophers deserve to be briefly retraced. Initially, Plato identified in thesoul the seat of reason, emotions and desires of men; it was separate from the body and was thought of as immaterial and immortal substance. For the philosopher, rationality was also regulated by the soul: in short, the brain did not seem to have any important function. Aristotleinstead, he thought that the soul resided in the heart and he conceived it as a principle that gives life to bodily and mental functions; the brain, “cold and rich in water”, served only to cool the heart. Only at the beginning of the 1600s, with Descartesbegan to be considered a certain dualism between mind and bodyboth recognized as integral parts of man and capable of communicating with each other via the pineal gland. He was born at the end of the 1800s cerebral physiology: Each area of the brain turns out to regulate specific mental functions. Thus, what had always been a philosophical dilemma begins to be material of scientific interest.
