The antennal lobe is the deutocerebral neuropil

Neuropil

In neuroanatomy, a neuropil, which is sometimes referred to as a neuropile, is a region between neuronal cell bodies in the gray matter of the brain and blood-brain barrier . It consists of a dense tangle of axon terminals, dendrites and glial cell processes...

 of insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

 which receives the input from the olfactory sensory neurons on the antenna

Antenna (biology)

Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....

. Functionally, it shares some similarities with the olfactory bulb

Olfactory bulb

The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors.-Anatomy:In most vertebrates, the olfactory bulb is the most rostral part of the brain. In humans, however, the olfactory bulb is on the inferior side of the brain...

 in vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s.

In insects, the olfactory pathway starts at the antennae (though in some insects like Drosophila

Drosophila

Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...

there are olfactory sensory neurons in other parts of the body) from where the sensory neurons carry the information about the odor

Odor

An odor or odour is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also commonly called scents, which can refer to both pleasant and unpleasant odors...

ant molecules impinging on the antenna to the antennal lobe. The antennal lobe is composed of densely packed neuropils, termed glomeruli

Glomerulus (olfaction)

The glomerulus is a spherical structure located in the olfactory bulb of the brain where synapses form between the terminals of the olfactory nerve and the dendrites of mitral, periglomerular and tufted cells...

, where the sensory neurons synapse

Synapse

In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...

 with the two other kinds of neurons, the projection neurons and the local neurons. There are 43 glomeruli in the Drosophila antennal lobe; in Aedes aegypti

Aedes aegypti

The yellow fever mosquito, Aedes aegypti is a mosquito that can spread the dengue fever, Chikungunya and yellow fever viruses, and other diseases. The mosquito can be recognized by white markings on legs and a marking in the form of a lyre on the thorax...

there are 32; locust

Locust

Locusts are the swarming phase of short-horned grasshoppers of the family Acrididae. These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory...

s and social wasps may have over 1000. The projection neurons project to higher brain centers such as the mushroom body and lateral horn

Lateral horn

In the thoracic region, the postero-lateral part of the anterior column projects lateralward as a triangular field, which is named the lateral column .-Nerve Cells in the Lateral Column:...

 of the protocerebrum. The local neurons, which are primarily inhibitory, have their neurites restricted to the antennal lobe. In Drosophila, each olfactory sensory neuron generally expresses a single olfactory receptor

Olfactory receptor

Olfactory receptors expressed in the cell membranes of olfactory receptor neurons are responsible for the detection of odor molecules. Activated olfactory receptors are the initial player in a signal transduction cascade which ultimately produces a nerve impulse which is transmitted to the brain...

gene, and the neurons expressing a given gene all transmit information to one or two spatially invariant glomeruli in the antennal lobe. Moreover, each projection neuron generally receives information from a single glomerulus. The interaction between the olfactory receptor neurons, local neurons and projection neurons reformats the information input from the sensory neurons into a spatio-temporal code before it is sent to higher brain centers.