Retinotopic Maps, Cortical Magnification, and Visual Pathways

Vocabulary flashcards covering key concepts from retinotopic mapping, cortical magnification, receptive fields and cortical organization, imaging techniques, and the what/where visual pathways.

Retinotopic map

A neural map in the visual cortex where spatial locations on the retina correspond to specific locations in the cortex.

Primary visual cortex (V1)

The occipital lobe region for early visual processing that contains retinotopic organization, orientation and location maps, and elements like columns and hypercolumns.

Fovea

The central retina region with high cone density that yields high visual acuity and detail; it has a disproportionately large cortical representation (cortical magnification) in V1.

Cortical magnification

The phenomenon where a small, central retinal area (fovea) takes up a large area of the visual cortex to support high-acuity vision.

Receptive field

The region of the retina or visual space where stimulation affects the firing of a specific neuron.

Location column

A vertical group of neurons in V1 that respond to the same retinal location; runs perpendicular to the cortical surface.

Orientation column

Neurons within a location column that respond preferentially to a particular orientation of a visual edge; neighboring columns prefer different orientations.

Hypercolumn

A complete set of orientation columns for a single retinal location, encompassing all orientations represented in one cortical module.

Retinotopic mapping

The organization where retinal locations map to specific cortical locations, though not perfectly one-to-one due to magnification and tiling.

Tiling (in visual cortex)

The coverage of the visual field by overlapping receptive fields across V1, ensuring full visual coverage.

Subtraction technique (in fMRI)

A method to isolate task-related brain activity by subtracting control-state (baseline) activity from stimulation-state activity.

Control state

Baseline brain activity measured when no specific visual task is performed during imaging.

Stimulation state

Brain activity measured while a participant views or attends to a visual stimulus during imaging.

Functional magnetic resonance imaging (fMRI)

A neuroimaging method that detects brain activity via changes in blood oxygenation (BOLD signal) related to neural activity.

What pathway (ventral stream)

The ventral visual pathway from V1 through the temporal lobe, specialized for identifying and naming objects; also called the ventral stream.

Where pathway (dorsal stream)

The dorsal visual pathway from V1 toward the parietal cortex, specialized for determining where objects are in space and guiding actions.

Ungerleider and Mishkin

Researchers who proposed the two visual pathways (what/ventral and where/dorsal) based on monkey studies of object and landmark tasks.

Object discrimination task

A task in which subjects identify which of two objects was recently shown, used to study the what/ventral pathway.

Landmark discrimination task

A task in which subjects use a landmark to identify the location of reward, used to study the where/dorsal pathway.

BOLD signal

The blood-oxygenation-level-dependent signal detected by fMRI, reflecting neural activity through changes in blood flow and oxygenation.