• Mayuri Vaish

Can brain 'organoids' ever be conscious?

Updated: Dec 18, 2018

To answer this question, let us first define the term ‘conscious’. Based on Oxford Dictionaries, think means “The state of being aware of and responsive to one's surroundings.”. In that case, there is a lack of evidence suggesting that organoids have any capability of forming thoughts or being aware, and thus my personal answer to this would be no, they are unable to be conscious. Although organoids structurally mimic the human brain, they lack the functions executable by it.


To understand why, let us clarify what a cerebral ‘organoid’ really is. Essentially, organoids are highly developed, 3-D tissue structures comprising of a variety of cell types (neurons, astrocytes, glial cells, etc.) and self-organized layers that model the human brain in-vitro.[1] These cultures are primarily used to study diseases in a more physiologically relevant setting while maintaining ethical standards, as well as to test therapeutic drugs for neural pathologies.


Fluorescent image of a cerebral organoid

Next, we need to understand where ‘consciousness’ really comes from. ‘Consciousness’, as it is defined today, is primarily a higher-order function, largely due to humans’ overly developed cerebral cortexes that allow for strong hierarchical cross-communication between neurons. Although what causes human consciousness still remains an unanswered question, general mechanisms of thinking involve retrieval of memories and their usage to evaluate future decisions. Being aware is also always in response to some form of sensory input that is received by specific cell receptors.


Now, putting the two together, a 3-D structure of cells grown in a nutrient medium lacks the means of obtaining sensory input via receptors, thus not allowing it to form memories if it has no sensory information at all. This phenomenon strips its capability to even remotely think or perform any higher-order functions. How can neurons transmit messages if nothing stimulates them to do so? (This does not include the spontaneous firing that occurs within neurons.).


To quote Christof Koch from the Allen Institute for Brain Science[2] :

“An animal deprived of visual inputs never learns to see, and organoids don’t have any inputs. They won’t see or hear or smell. They can’t recall anything because there’s nothing to recall. They can’t think in any way, shape, or form.”