Unit 2C: Visual Disorders

Question 1

Sensation

Answer 1

the first stage in the functioning of the senses, starting with information at the peripheral sensory receptors

Question 2

Perception

Answer 2

the process of recognizing, organizing and interpreting sensory information

Question 3

Dorsal visual pathway

Answer 3

made up of multiple visual areas, it is one of two main visual processing streams after primary visual cortex. This pathway is involved in perception for action.

Question 4

Ventral visual pathway

Answer 4

made up of multiple visual areas, it is one of two main visual processing streams after primary visual cortex. This pathway is involved in perception for recognition.

Question 5

Cortical magnification

Answer 5

is a property of sensory and motor systems in which one part of a topographical representation is relatively larger than the rest, producing a region with higher acuity in the magnified region.

Question 6

Blindsight

Answer 6

a phenomenon where people who are perceptually blind demonstrate some response to visual stimuli.

Question 7

Visual agnosia

Answer 7

a disorder in which the patient suffers from the inability to recognize and identify objects, features of objects or scenes, faces or persons despite having knowledge of the characteristics of the objects, scenes, faces, or persons. This condition can be loosely divided into two types that differ by severity: apperceptive and associative.

Question 8

Apperceptive visual agnosia

Answer 8

a disorder characterized by the inability to name, copy or recognize visually presented objects. Shape perception and figure ground segregation is impaired, but basic visual functions, and object identification based on non-visual cues are preserved.

Question 9

Associative visual agnosia

Answer 9

A disorder in which visual object recognition is
impaired (e.g. naming of visually presented objects, categorization, matching by function), but elementary visual perception is more or less preserved. This is how object agnosia is typically described, as this is the more common type

Question 10

Visual object agnosia

Answer 10

A disorder in which visual object recognition is impaired (e.g. naming of visually presented objects, categorization, matching by function), but elementary visual perception is more or less preserved, e.g., matching and copying of
visually presented forms and objects, drawing objects from memory, and non-visual object recognition.

Question 11

Fusiform face area

Answer 11

A bilateral visual processing area that is thought to be specialized for face processing (with some controversy–some authors argue that it is specialized for detailed visuospatial processing, not necessarily just face processing). Damage to this region can cause face perception deficits.

Question 12

Prosopagnosia

Answer 12

A disorder in which faces cannot be recognized, but other forms of object recognition are unimpaired.

Question 13

Apperceptive type

Answer 13

problems with recognizing a face vs. other objects (can’t tell by vision alone whether something is a face or not)

Question 14

Associative (amnesic) type

Answer 14

problems with recognizing familiar faces (can tell it’s a face, but not whose face it is)

Question 15

Capgras syndrome

Answer 15

The delusional belief that an acquaintance has been replaced by an identical-looking imposter. It is one of the delusional misidentification syndromes more commonly seen in schizophrenia, dementia, and brain trauma. May arise from an abnormal emotional response to faces -> disconnect between temporal and limbic cortex; possible example of a really high-order face processing issue

Question 16

Fregoli syndrome

Answer 16

The delusional belief that different people are in fact a single person who changes appearance or is in disguise, generally viewed with paranoia (that the “shapeshifting” person is out to get them). This is another rare delusional misidentification syndrome. Appears to arise from damage to left frontal and right
temporoparietal regions, possibly due to a disconnection between hemispheres, that
affects high-order face processing. A person with the Fregoli delusion may also inaccurately recall places, objects, and events, leading to the theory that associations among stored memories may be messed up – with the image of one face (or place/object/event) ending up being improperly associated with another one.

Question 17

Simultagnosia

Answer 17

a deficit in scene perception, with a normal visual fields and normal lower-level (elementary) visual perception. Several theories have been proposed to account for simultagnosic symptoms: some focus on the disruption of a specific process, such as the speed of attentional processing, others focus on the disruption of a representational structure

Question 18

Dorsal simultagnosia

Answer 18

a deficit in scene perception where the patient can only perceive one stimulus at a time (more severe than ventral type)

Question 19

Ventral simultagnosia

Answer 19

a deficit in scene perception where the patient can see multiple objects, but cannot recognize them (can navigate and count, but cannot
read)

Question 20

Central/Cerebral achromatopsia

Answer 20

an impairment of color vision in the entire visual field that arises from cortical lesions on the ventral surface of the temporal-occipital lobes. Loss of color vision in the full visual field is rare, as lesions would need to affect color processing in both hemispheres.

Question 21

Hemiachromatopsia

Answer 21

Loss of color vision is restricted to one half of the visual field. The rest of the visual field has normal color vision. (Color vision can even
be lost for just one quarter of the visual field.

Question 22

Transient achromatopsia

Answer 22

temporary loss of color vision in any part of the visual field, usually from a TIA (transient ischemic attack)

Question 23

Akinetopsia

Answer 23

the inability to perceive motion that arises from damage to V5/MT – the area of cortex responsible for visual motion; patients experience a strobe-light effect of vision. It can be caused by damage such as stroke, trauma and rarely from some antidepressants