The most difficult brain riddles

The gut–brain axis is the biochemical signaling that takes place between the gastrointestinal tract and the central nervous system. Changes in the composition of the gut flora due to diet, drugs, or disease correlate with changes in levels of circulating cytokines, some of which can affect brain function. The gut flora also release molecules that can directly activate the vagus nerve. Around 70% of people with autism also have gastrointestinal problems, indicating that there may be a connection between autism and gut flora.

The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. In humans, the cerebellum plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language as well as in regulating fear and pleasure responses. Based on the surface appearance, three lobes can be distinguished within the cerebellum: the anterior lobe (above the primary fissure), the posterior lobe (below the primary fissure), and the flocculonodular lobe (below the posterior fissure).

Unconsciousness is a state which occurs when the ability to maintain an awareness of self and environment is lost. It involves a complete or near-complete lack of responsiveness to people and other environmental stimuli.

Tarsiers are small animals with enormous eyes; each eyeball is approximately 16 millimetres (0.63 in) in diameter and is as large as, or in some cases larger than, its entire brain. The unique cranial anatomy of the tarsier results from the need to balance their large eyes and heavy head so they are able to wait silently for nutritious prey.

The pons (Latin for "bridge") is part of the brainstem, and in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum.This region of the brainstem includes neural pathways and tracts that conduct signals from the brain down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus.

The term laterality refers to the preference most humans show for one side of their body over the other. Examples include left-handedness/right-handedness and left/right-footedness. It may also refer to the primary use of the left or right hemisphere of the brain.

Neanderthals had large cranial capacity (1,600 cm3), which was larger than that of modern humans. Compared to modern humans, neanderthals had shorter legs and bigger bodies - this was likely an adaptation to preserve heat in cold climates. Larger eye sockets suggest that their eyesight may have been better than that of modern humans.