A fascinating study from 2005 showed that single neurons can represent certain individual items in the world. What made this study even more interesting is that the researchers localized the individual human neurons that activated in response to seeing a picture of celebrities such as Halle Berry or Jennifer Aniston.
Patients with drug-resistant epilepsy underwent brain surgery to be implanted with electrodes. As part of this process, the researchers recorded responses from neurons when showing the patients pictures of celebrities. A neuron activated when showing a patient the picture of Jennifer Aniston, but not a picture of Jennifer Aniston together with Brad Pitt. A neuron activated when showing a patient a picture of Halle Berry and the same neuron activated when the patient was shown text saying “Halle Berry.”
Invariant visual representation by single neurons in the human brain. (Link)