Neural circuit

Also known as: brain circuit

In one sentenceA neural circuit is a group of neurons connected by synapses that work together to carry out a specific function such as sensory processing, movement or memory.

Overview

The human brain contains roughly 86 billion neurons, each exchanging signals with others through synapses. A set of neurons wired together to perform a function is called a neural circuit.

Building blocks

• Excitatory neurons send signals that activate their targets. In the cerebral cortex they mainly use glutamate.
• Inhibitory neurons mostly use GABA to suppress their targets and keep circuits from becoming overexcited.
• Wiring patterns such as feedforward, feedback and recurrent connections determine what computation a circuit performs.

Local and large-scale circuits

Local circuits form among neighboring cells within one cortical area. Large-scale circuits link distant regions such as the cortex, thalamus and basal ganglia; the cortico–basal ganglia–thalamic loop involved in motor control is a classic example.

How circuits are studied

Circuit research asks two questions together: which cells connect to which (structure), and when and how those connections operate (function). Key tools include optogenetics, which switches specific cells on and off, fMRI, which records whole-brain activity, and optogenetic fMRI, which combines the two.

The lab of Jin Hyung Lee at Stanford states its goal as understanding the connectivity and function of large-scale brain circuits in order to drive new therapies for neurological diseases.

Circuits and the mind

Many studies try to explain cognitive functions such as memory and attention through cooperating circuits. Working memory is a prominent example studied in terms of sustained circuit activity.