Occipital Lobes, Visual Pathways, and Agnosias

Vocabulary practice flashcards covering occipital lobe anatomy, dorsal and ventral visual streams, field defects, computational and neuropsychological models, and visual agnosias including prosopagnosia.

Calcarine Sulcus

A major sulcus on the medial surface of the occipital lobe that contains much of the primary visual cortex (V1) and separates the upper and lower visual fields.

Lingual Gyrus

A cortical structure located on the ventral surface of the occipital lobe that corresponds to visual area V2.

Fusiform Gyrus

A gyrus on the ventral surface of the brain associated with visual area V4 (involved in color and form processing) and specialized facial processing regions.

Dorsal Stream

The visual processing pathway that projects from the visual cortex to the parietal lobe, responsible for the visual guidance of movements (such as grasping) and converting visual information into action coordinates.

Ventral Stream

The visual pathway projecting from the visual cortex to the inferior temporal lobe and superior temporal sulcus (STS), primarily mediating object perception.

Superior Temporal Sulcus (STS)

A multimodal processing area associated with the ventral stream that utilizes polysensory neurons to perceive biological motion, facial movement, mouth movement, and eye movement.

Visual Area V4

A visual cortical area dedicated to color processing, form, and shape; damage to this area causes loss of color cognition, rendering patients unable to see, imagine, or recall color.

Visual Area V5

A specialized cortical area for motion perception; damage results in akinetopsia, erasing the ability to perceive objects in motion while sparing vision for objects at rest.

Cortical Blindness

A loss of conscious vision resulting from bilateral lesions to the primary visual cortex (V1) where other sensory modalities remain intact, often coexisting with unconscious residual vision known as blindsight.

Bitemporal Hemianopia

A visual field defect causing blindness in the temporal half of both the left and right visual fields, typically caused by a midline lesion of the optic chiasm.

Homonymous Hemianopia

A visual deficit characterized by the loss of the same half of the visual field in both eyes, resulting from a post-chiasmal lesion to the contralateral optic tract, optic radiations, or occipital lobe.

Visual Agnosia

A deficit characterized by a failure of visual recognition that is not explained by elementary sensory defects or attributable to intellectual deterioration or generalized dementia.

Apperceptive Agnosia

A type of agnosia characterized by the inability to combine individual visual features to form a coherent percept, leaving patients unable to copy drawings or match objects; typically results from gross bilateral damage to the lateral occipital lobes, often due to carbon monoxide poisoning.

Associative Agnosia

An impairment in recognizing the semantic meaning of visually presented objects despite preserved ability to perceive, match, and accurately copy them, caused by lesions higher in the processing hierarchy such as the anterior temporal lobe.

Simultagnosia

A symptom commonly observed in apperceptive agnosia wherein a patient is unable to perceive more than one object or visual detail at a single time.

Prosopagnosia

An acquired or developmental condition characterized by the inability to recognize previously familiar faces or learn new faces, associated with lesions to the bilateral or right mesial occipitotemporal region.

Stage Model of Recognition (Lissauer, 1890)

A classical recognition framework proposing two sequential stages: apperception, which integrates sensory input into a percept, and association, which links that percept to stored information from past experiences.

Disconnection Model (Geschwind, 1965)

A model proposing that visual recognition deficits arise from an anatomical or functional disconnection between intact visual perceptual systems and verbal processing networks.

Primal Sketch

The earliest stage of representation in Marr's (1982) computational model, capturing the basic elementary visual features of an object from sensory input.

Object-Centered Representation

A higher-level internal representation in computational models that allows an object to be identified independently of viewing perspective or orientation.

Person Identity Node (PIN)

A structural component in the Ellis and Young (1988) cognitive model of face recognition that mediates between face recognition units and speech output lexicon for retrieving a person's spoken name.