How does the LGN work?

How does the LGN work?

The LGN brings retinotopic maps from both eyes into register to make it easy for cortex to combine inputs from the two eyes. Only 10% of inputs to LGN come from the retina. 90% are modulatory inputs from cortex and the brainstem.

Where is the LGN in the brain?

thalamus
They wrap around the midbrain and cross the medial surface of the temporal lobe, and 80% of them then terminate in a synaptic relay called the lateral geniculate nucleus (LGN), located in the dorsal part of the thalamus. The LGN is thus the major target for each optic tract.

What is the function of V1?

The main task of V1 is to process visual inputs from the LGN and send the results of this processing to higher visual areas and subcortical structures. In primates, these include areas V2, V3, MT, MST, and FEF (Van Essen and Felleman, 1991).

What is the role of the lateral geniculate nucleus?

The lateral geniculate nucleus (LGN) belongs to the category of sensory projection nuclei of the thalamus and plays an essential role in normal visual processing.

What is Retinotopic mapping?

Retinotopy (from Greek τόπος, place) is the mapping of visual input from the retina to neurons, particularly those neurons within the visual stream. In general, these complex maps are referred to as second-order representations of the visual field, as opposed to first-order (continuous) representations such as V1.

What happens if the LGN is damaged?

In humans and other primates, visual information is transmitted from the retina to a part of the brain called the lateral geniculate nucleus (LGN), before reaching the primary visual cortex (V1). If the V1 is damaged, conscious vision is lost in the area of the visual field that corresponds to the damage.

Why is the LGN important?

In addition to retinal afferents, the LGN receives input from multiple sources including striate cortex, the thalamic reticular nucleus (TRN), and the brainstem. The LGN therefore represents the first stage in the visual pathway at which cortical top-down feedback signals could affect information processing.

What does LGN stand for?

LGN

Acronym	Definition
LGN	Look Good Naked
LGN	Logical Group Node (Sprint-ATM)
LGN	Logical Group Number
LGN	Linear Graph Notation

Why the Retinotopic map in V1 is distorted?

Visual Perception, Neural Basis of For instance, if the input to visual cortex has an anomalous distribution across the retina (e.g., as a result of a congenital absence of cones in the central fovea) the usual retinotopic map in V1 is distorted to match this distribution.

What makes up the cells of the LGN?

All cells in the LGN have concentric receptive fields, just like the ganglion cells whose fibres terminate in the LGN. Layers 1 and 2 are made up of cells with large bodies (“magnocellular”) that have monochromatic responses (ie.

How many neurons are in the lateral geniculate nucleus ( LGN )?

Bilateral structure with six layers 1 million neurons in total Each layer receives signal from one eye Layer 2,3,5 receives from ipsilateral eye Layer 1,4,6 receives from contralateral eye Each eye send half information to each side LGN Slide 5 Aditi Majumder, UCI Retinotopic Map Each location in LGN maps to a location on retina

How are the m and P layers of the LGN related?

These layers were named this way because cells in the M layers of the LGN are larger than cells in the P layers. M cells in the LGN receive input from parasol ganglion cells (which some neuroscientists call M cells), and P cells receive input from midget retinal ganglion cells (which some neuroscientists call P cells).

Where is the LGN located in the brain?

Although the retina sends axons to many subcortical nuclei, only the pathway from the retina to LGN to cortex is critical to visual awareness. The LGN is a distinctively layered structure and is located at the posterior lateral margin of the dorsal thalamus ( Fig. 29.1 ).