The torus semicircularis is a region of the
vertebrate midbrain that contributes to
auditory perception
Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory ...
, studied most often in
fish and
amphibians
Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbore ...
. It corresponds to the
inferior colliculus.
Neurons
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...
from the medulla project to the nucleus centralis and the nucleus ventrolateralis in the torus semicircularis, providing afferent auditory and hydrodynamic information. Research suggests that these nuclei interact with each other, suggesting that this area of the brain is bimodally sensitive. In the Gymnotiform fish, which are weakly electric fish, the torus semicircularis was observed to exhibit laminar organization. It receives afferent input, specifically electrosensory, mechanical, and auditory stimuli. In frogs, researchers have studied how neurons in the torus semicircularis prefer certain characteristics of sound differentially. Single neurons fire selectively based on the auditory parameters of a stimulus. Functionally, this can allow members of a species to distinguish whether a call is of the same (conspecific) or a different species. This has been observed to play a role in mate selection. In the Tungara frog, which produces a species-specific mating call, scientists studied responses in the laminar nucleus of the torus semicircularis to various parts of the call. They came to the conclusion that this part of the brain acts as a feature detector (a neuron/neurons that respond to a certain feature of a stimulus) for the parts of the auditory stimulus that are conspecific. From an evolutionary standpoint, research has been conducted in
turtles to connect the distribution of
calcium-binding proteins in the torus semicircularis among birds and
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s to a common reptile predecessor.
References
Midbrain
Neuroscience
Vertebrate anatomy
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