#31 - Cortex Function Flashcards
1
Q
Primary Visual Cortex
(V1 / striate cortex)
A
- Occipital lobe
- Located medially on the banks of the calcarine fissure extending around the occipital pole
- Left visual field is represented in right visual cortex; vice versa
- Lower visual field is represented in dorsal bank; vice versa
- Central (macular) vision is located at the occipital pole
- Visual fields are represented as a retinotopic map
- Damage = CONTRA scotomas, quadrantopsia, or hemianopsia
2
Q
Secondary visual (extrastriate) cortex
A
- Occipital lobe
- Secondary visual areas form the extrastriate cortex surrounding V1, analyze specific attributes of visual stimuli
- V2: strongly interconnected with V1, responds to complex patterns
- V3: contains dorsal (V3a) and ventral (VP) divisions
- Dorsal V3a neurons receive input form V1 and V2, respond to large scale motion
- Ventral VP receives input mostly from V2, involved in object recognition
- Thus, two visual streams become separated at V3:
-
Dorsal stream:
- Object and relative body motion
- Placing of objects in external space (where?)
- Control of visually-guided eye movements
-
Ventral stream
- Pattern and object recognition (what?)
-
Dorsal stream:
3
Q
Area V4
A
- Occipital Lobe
- Visual association area: ventral stream and temporal lobe
- Area V4 is concerned in the assemblage of object representations
- Output directed to posterior inferior temporal lobe, “IT”
-
Left IT: processing feature information like color, texture, shape, symbols associated with language (e.g., writing)
- Damage: alexia with agraphia
-
Right IT: holistic, non-verbal perception, facial recognition
- Damage: prosopagnosia
-
Left IT: processing feature information like color, texture, shape, symbols associated with language (e.g., writing)
- General lesion to ventral stream: visual form agnosia = Inability to recognize objects, discriminate between simple geometric shapes and orientation
4
Q
Area V5
A
- Occipital lobe
- Visual Association Areas - Dorsal Stream & Parietal lobe
- Area V5 is located in the posterior end of the middle temporal gyrus
- Sends info to the posterior parietal cortex, including parietal eye fields
- PEF: Generate saccadic eye movements evoked by novel visual/auditory stimuli
- Involved in motion perception and assemblage of objects in visual space
- Lesion to dorsal stream (posterior parietal cortex) = Balint’s Syndrome
- Simultanagnosia
- Ocular apraxia: absence of purposeful eye movement
- Optic ataxia: lack of coordination btwn visual and motor
5
Q
Primary Auditory Cortex
A
- Temporal lobe
- Located in transverse temporal gyri (Heschl’s gyri)
- Is tonotopically organized
- Lesions: may lead to loss of awareness of sound, but reflexes involving sound remain intact
- Receives binaural input with contralateral dominance
- Receives thalamic input from medial geniculate nuclei
- Inferior colliculus > MGN > sublenticular projection from thalamus to roof of Heschl’s gyrus
6
Q
Auditory “belt” cortex
A
- Temporal lobe
- Ring of associatoin cortex surrounding the primary auditory cortex
-
LEFT: involved in decoding temporal aspects of sounds
- Ex: sequence, duration, intervals
-
RIGHT: involved in decoding spectral aspects of sounds
- Ex: frequency/pitch, harmonics
- Plays a general role in “auditory imagery”; fills gaps in speech (L) and in melodies (R)
- Hierarchical nature of auditory processing:
- Primary auditory cortex responds to simple stimuli (tones) and downstream regions are selectively responsive to more complex stimuli (band noise, speech) with neural codes progressively more abstract the farther away from Heschl’s gyri you get
7
Q
Wernicke’s Area
A
- Temporal lobe; left posterior superior temporal gyrus
- Decodes verbal info
- Activated by phonemic content (perceptually distinct units of sound in language) and gaps between speech sounds
-
Damage = sensory aphasia
- Inability to understand language in written or spoken form
- Speech is fluent, effortless, melodic, but jumbled and unintelligible, normal grammar, syntax, rate, and intonation but they can’t express themselves meaningfully using language.
- Similar area on the right/dominant side appears to be involved in prosody (various rhythms, intonations in normal speech)
- Lesions to R = sensory aprosodia, inability to detect prosodic elements (humor, sarcasm) in speech
8
Q
Auditory Association What, Where Streams
A
-
Ventral “what” stream: directed at temporal cortex
- Plays a general role in auditory object recognition, including perception of vocalizations and speech
-
Dorsal “where” stream: directed at parietal cortex
- Pertains to significance of the location, motion of the sound source
9
Q
Dorsal Stream
A
Where
Parietal cortex
10
Q
Ventral Stream
A
What
Temporal cortex
11
Q
Lateral, Inferior Temporal Lobe
A
- Areas key to interpretation and categorization of “what”
- Left
- Caudal parts are important for retrieval of the general names (common nouns) of objects (dogs, carrots)
- Anterior parts (temporal pole) are important for retrieval of proper nouns that denote unique entities (individuals, places)
- Lesions = anomia (naming defect) with severity increasing with lesions closer to the temporal pole
- Right
- Recognition of objects and retrieval on non-verbal info pertaining to these objects
12
Q
Medial/Mesial Temporal Lobe
A
- Includes parahippocampal gyrus, hippocampus, and amygdala
- Critical for memory formation, emotion, and sexual behavior
13
Q
Primary Somatosensory Cortex
A
- Parietal Lobe
- Rostral-caudal in postcentral gyrus, has a somatotopic map (sensory homunculus) of contra body
- Granular layer of cortex
- Brodmann’s areas:
-
Area 3: primary somatosensory cortex
- Receives most of output of VPL and VPM
- Area 3a: proprioception
- Area 3b: pressure and vibration sense
- Area 1: texture processing
- Area 2: estimating size and shape
-
Area 3: primary somatosensory cortex
- Postcentral gyrus lesions:
- Loss of 2-point discrimination
- Agraphesthesia: inability to recognize written letters or numbers traced on skin
- Astereognosis: inability to identify an object by active touch of the hands without other sensory input
14
Q
Somatosensory Association Areas
A
- Parietal lobe
- Integrates complex stimuli in the external and internal environment
- All have a crude sensory homunculus
-
Ventrolateral zone: parietal operculum, which has 4 association areas
- Lesion leads to tactile agnosia = patients cannot recognize or name objects by touch
-
Dorsomedial zone: supplementary somatosensory area, has 1 association area
- Lesion (especially on R) leads to constructional apraxia = difficulty with simple drawing, assembling blocks
15
Q
Inferior Parietal Lobule Components
A
- Supramarginal gyrus
- Angular gyrus
- Right, Left IPL
