Dendrite | How Do Your Brain Cells Receive Information?

Dendrites are the branched, tree-like extensions of a neuron that serve as the primary receivers of signals from other nerve cells. Their fundamental role is to collect and integrate incoming electrochemical information. This information is transmitted at specialized junctions called synapses, where signaling molecules known as neurotransmitters are released from an adjacent neuron. The intricate branching structure of the dendritic tree creates a vast surface area, allowing a single neuron to receive thousands of inputs simultaneously. When neurotransmitters bind to receptors on the dendritic membrane, they generate small electrical currents called postsynaptic potentials. These potentials, which can be either excitatory (increasing the likelihood of the neuron firing) or inhibitory (decreasing the likelihood), travel along the dendrite toward the neuron's cell body (soma). The dendrite's function is therefore not merely passive reception; it is the first stage of information processing in the neuron, where signals are collected and combined.

Dendritic spines are microscopic, thorn-like protrusions that cover the surface of many types of dendrites. They are the primary location of excitatory synapses in the brain and are fundamental to neural function. Each spine typically forms a synapse with a single axon terminal from another neuron. Their existence vastly increases the potential number of contacts a dendrite can make. Critically, dendritic spines are not static structures; they are highly dynamic and can change their size, shape, and number in response to neural activity. This phenomenon is a key component of synaptic plasticity, the cellular mechanism that underlies learning and memory. The strengthening or weakening of connections via changes in dendritic spines is how the brain adapts and stores information. Consequently, abnormalities in spine morphology and density are linked to numerous cognitive and developmental disorders, highlighting their essential role in maintaining healthy brain circuits.

No, dendrites are not simple, passive conduits. They are sophisticated computational devices that actively process synaptic information. A neuron's decision to fire an action potential—the all-or-nothing electrical signal that travels down the axon—depends on the complex integration of thousands of excitatory and inhibitory inputs received by its dendrites. This process, known as synaptic integration, involves summing signals both spatially (across different locations on the dendritic tree) and temporally (as they arrive over time). Furthermore, some dendrites can generate their own localized electrical spikes, which can amplify or modify incoming signals before they reach the cell body, adding another layer of computational complexity.

The structural integrity of dendrites is essential for normal brain function, and their deterioration is a hallmark of many neurological and psychiatric conditions. In neurodegenerative diseases such as Alzheimer's, a prominent feature is the widespread loss of dendritic spines and simplification of dendritic branches. This dendritic pathology severs synaptic connections, disrupting neural networks and contributing directly to the characteristic cognitive decline and memory loss. Similarly, in neurodevelopmental disorders like autism spectrum disorder and schizophrenia, evidence points to abnormal dendritic spine density, size, and shape, suggesting that impaired synaptic communication from early development is a core component of these conditions.

Dendrites are at the forefront of neuroplasticity, the brain's ability to reorganize itself by forming new neural connections. Learning and experience physically reshape dendritic structures. When a new memory is formed or a skill is acquired, the relevant neural circuits are strengthened. This occurs at the microscopic level through the formation of new dendritic spines and the enlargement of existing ones, making synaptic transmission more efficient. This process is called structural plasticity. For instance, mastering a new motor skill can lead to the growth and stabilization of new spines in the motor cortex. Conversely, synapses that are not used may weaken, and their corresponding spines may shrink or be eliminated entirely in a process known as synaptic pruning. This dynamic remodeling of dendritic architecture allows the brain to continuously adapt to new information and environments, effectively embedding experience into the physical structure of its neural circuits.