Retina horizontal cell

Gray's anatomy image 882

== Retina Horizontal Cell ==

Retina horizontal cells are a type of neuron found in the retina of the eye. These cells play a crucial role in the processing of visual information by integrating and regulating the input from multiple photoreceptor cells (rods and cones) before it is transmitted to bipolar cells and subsequently to ganglion cells.

Structure

Horizontal cells are located in the outer plexiform layer of the retina. They have extensive lateral connections with the synaptic terminals of photoreceptors and the dendrites of bipolar cells. These cells are characterized by their wide, horizontally oriented dendritic fields, which allow them to interact with a large number of photoreceptors.

Function

The primary function of horizontal cells is to mediate lateral inhibition in the retina. This process enhances the contrast and sharpness of visual images by inhibiting the activity of neighboring photoreceptors. Horizontal cells achieve this by releasing the neurotransmitter GABA (gamma-aminobutyric acid), which hyperpolarizes adjacent photoreceptor cells and reduces their output.

Types

There are generally two types of horizontal cells in the human retina:

• H1 cells: These cells primarily connect with cone cells and are involved in color vision.
• H2 cells: These cells also connect with cone cells but have a broader range of connections and are involved in both color and luminance processing.

Role in Visual Processing

Horizontal cells contribute to the center-surround receptive field organization of bipolar and ganglion cells. By providing inhibitory feedback to photoreceptors, they help to create the antagonistic center-surround structure that is essential for edge detection and contrast enhancement in visual perception.

Pathology

Dysfunction or degeneration of horizontal cells can lead to various visual impairments. For example, abnormalities in horizontal cell function are implicated in certain types of retinal degenerative diseases and may contribute to conditions such as retinitis pigmentosa and age-related macular degeneration.

See Also

• Retina
• Photoreceptor cell
• Bipolar cell
• Ganglion cell
• Lateral inhibition
• Outer plexiform layer
• GABA

Related Pages

• Retina
• Photoreceptor cell
• Bipolar cell
• Ganglion cell
• Lateral inhibition
• Outer plexiform layer
• GABA