Occipital, Parietal, and Temporal Lobes Flashcards
What defines the separation of the occipital cortex from the temporal or parietal cortex on the lateral surface?
- there is no clear division
What is the medial surface of the occipital lobes?
- occipital- parietal surface
- calcarine sulcus: contains much of primary visual cortex (V1) and separates upper and lower visual fields
What does the ventral surface of the occipital lobes contain?
- lingual gyrus (V2)
- fusiform gyrus (V4)
From what view can you see the calcarine sulcus?
- mid-saggital
Where does the primary visual cortex (V1) get input from?
- lateral geniculate nucleus (LGN)
Where does the primary visual cortex (V1) send its output to?
- all other occipital levels
Where does secondary visual cortex (V2) send its output?
- all other occipital levels
What are the three distinct parallel pathways after V2?
- output to the parietal lobe - dorsal stream
- output to the inferior temporal lobe (ventral stream)
- multimodal output to the superior temporal sulcus (STS)
What is the dorsal stream?
- visual guidance of movements for grasping
- some neurons may take part in converting visual info into coordinates for action
What are the parts of the ventral stream and what are they responsible for?
- IT Inferior temporal cortex: object perception
- STS superior temporal sulcus: visuospatial functions
What is V1 responsible for and what happens if it is lesioned?
- sending output to all other visual areas (V2, V5, V3A)
- critical damage
- cortically blind
What is V2 responsible?
- sending output to all other visual areas (V3, V4, parietal visual areas)
What is V3 responsible for and what happens if it is lesioned?
- dynamic form (ventral) and form (V3A, dorsal)
- edges blur together
- in combination with larger lesion of V4 would result in form deficit
What is V4 responsible for and what would happen if it was lesioned?
- colour form
- would only see in black and white (loss of color cognition)
- cannot imagine or recall color
What is V5 responsible for and what would happen if it was lesioned?
- motion
- akinetopsia
- erases the ability to perceive objects in motion (can only see objects at rest)
What is opsin and retinal?
- opsin is a protein and can process one of the main colours
- retinal is a lipid
What are the three known alterations in the trichromatic coding?
- protanopia
- deuteranopia
- tritanopia
What is protanopia?
- visual acuity is normal
- “red” cones may be filled with “green” opsin
- confusion between red and green
What is deuteranopia?
- “green” cones may be filled with “red” opsin
What is tritanopia?
- difficulty with hues of short wavelengths
- see world in greens and reds
- retina lacking of “blue” cones
What is agnosia?
- failure of recognition
- not explained by sensory defects
- not attributable to other pathologies or cognitive deterioration
What is the disconnection model?
- visual perception connection to verbal processes is damaged
- results in agnosia
- unlikely because with agnosia usually certain categories of words are affected
What is the Stage Model (Lissauer, 1890) (model of recognition)?
- apperception: repeated sensory input forms a percept (red apple, green apple, apple juice, apple scent)
- association: relating stored information to the percept
What is the computational model (Marr, 1982) (model of recognition)?
- we have stored representations
- primal sketch: recognizing drawing of pumpkin
- viewer-centered: recognizing back of empress
- object-centered: recognizing back of obama’s head
What is the cognitive neuropsychology model (model of recognition)?
- see object
- initial representation
- viewer-centered representation and object-centered representation
- object recognition units
- semantic system (what is the object used for)
- name retrieval (lexicon)
What are the two types of object agnosia?
- apperceptive agnosia
- associative agnosia
What is apperceptive agnosia?
- failure in object recognition but basic visual functions (acuity, color, motion) preserved
- unable to match or copy (can’t put pairs of objects together or copy a drawing)
What is a common symptom of apperceptive agnosia?
- simultagnosia: unable to perceive more than one object at a time
- perceive picnic as one object: blanket or bread
What does apperceptive agnosia result from?
- gross bilateral damage to the lateral parts of the occipital lobes
- (commonly from carbon monoxide poisoning)
What is associative agnosia?
- inability to recognize an object despite its apparent perception
- can copy a drawing but not identify it
- loss of knowledge of the semantic meaning of objects
What does associative agnosia result from?
- lesions higher in the processing hierarchy (anterior temporal lobe)
What is hypothesis 1?
- that the semantic system is modality-specific
- meaning that there is a semantic system for visual, semantic system for auditory, etc.
- ex. can look at bell and not identify it, but can identify it when they hear it
What is hypothesis 2?
- that the semantic system is anatomically specific
What is cerebral achromatopsia and what is it caused by?
- cortical colourblindness
- lesion in inferior surface of temporo-occipital region in the lingual and fusiform gyri
What is colour agnosia and what is it caused by?
- cannot name colours
- unknown
What is cerebral akinetopsia and what is it caused by?
- unable to see objects that move
- lesion to posterior middle temporal gyrus
What is prosopagnosia?
- inability to recognize previously familiar faces
- inability to learn new faces
What is prosopagnosia caused by?
- bilateral or R messial occipitotemporal region
- visual-limbic disconnection syndrome
What are the subdivisions of the parietal cortex?
- postcentral gyrus (1 2 3)
- superior parietal lobule ( 5 7)
- parietal operculum (43)
- inferior parietal lobule: supramarginal gyrus (40) and angular gyrus (39)
What are the functional zones of the parietal lobes?
- anterior zone (1 2 3 43): somatosensory cortex
- posterior zone (remaining): posterior parietal cortex
What are von Economo’s maps?
- posterior parietal areas in both human and monkey
- parietal area E (PE)
- parietal area F (PF)
- parietal area G (PG): polymodal and asymmetrical (larger in right hemi of humans)
What are the visual processing areas of the parietal lobes?
- intraparietal sulcus: controls saccadic eye movements
- parietal reach regions: visually guided grasping movements
What are the connections of the parietal cortex?
- posterior parietal and the prefrontal cortex
- posterior parietal cortex and the dorsolateral prefrontal region
- prefrontal cortex and posterior parietal regions project to paralimbic and temporal cortices, hippocampus and subcortical regions
What do the connections of the parietal cortex play a role in?
- controlling spatially guided behaviour
What is the theory of parietal lobe function?
- anterior zones: process somatic sensations and perceptions
- posterior zones: integrate information from vision with somatosensory info for movement and spatial function
- significant role in mental imagery
What are three other symptoms related to parietal lobe damage that do not fit with the visuomotor view?
- acalculia: difficulties with arithmetic (inability of mental imaging)
- difficulties with certain aspects of language: quasi spatial (wife’s son vs son’s wife)
- difficulties with movement sequences: cannot copy movement
What does lesions to the postcentral gyrus produce?
- abnormally high sensory thresholds
- impaired position sense
- deficits in sterognosis or tactile perception
- afferent paresis: clumsy finger movements because lack of feedback about finger position
What are three somatoperceptual disorders?
- astereognosis
- simultaneous stimulation
- numb touch (blind touch)
What is atereognosis?
- disorder of tactile perception
- inability to recognize nature of an object by touch
What is simultaneous stimulation?
- two stimuli applied simultaneously to opposite sides of the body
- a failure to report stimulus on one side (extinction)
- associated with damage to ares PE and PF
What is numb touch (blind touch)?
- cannot feel stimuli and cannot feel touch, but can report location
- large lesions in areas PE and PF and some of PG
What is asomatognosia?
- loss of sense of one’s own body
What are some types of asomatognosia?
- anosognosia
- anosodiaphoria
- asymbolia for pain
- autopagnosia
What is anosognosia?
- unawareness or denial of illness
What is anosodiaphoria?
- indifference to illness
What is asymbolia for pain?
- absence of normal reactions to pain such as withdrawal
What is autopagnosia?
- usually results from left parietal cortex lesions
- finger agnosia
What is Balint’s syndrome?
- bilateral damage to posterior parietal lobe
- could not fixate on a visual stimulus
- simultagnosia
- optic ataxia: problems with reaching under visual guidance
What is the cause of contralateral neglect?
- lesion in right inferior parietal lesions
- damage to right intraparietal sulcus and the right angular gyrus
- occasionally after lesions to frontal lobe and cingulate cortex
What is contralateral neglect?
- neglect for visual, auditory and somesthetic stimulation on one side of the body
- constructional apraxia
- unaware of condition
- impairment in drawing and cutting
- topographic disability: cannot draw maps
What is theory 1 of contralateral neglect?
- neglect caused by defective sensation or perception
- lesion in area that receives input from all sensory regions
- specifically in right hemi because of role of integrating spatial information
What is theory 2 of contralateral neglect?
- neglect caused by defective attention or orientation
What is neglect paralexia?
- will only read one side of two sided words
- ex cowboy and desktop
What is neglect paragraphia?
- will ignore half the page when typing or writing
What is personal neglect?
- shaving half the face, dressing half the body, combing hair on one side
What is apraxia?
- cognitive motor disorder that entails the loss or impairment of the ability to program motor systems to perform purposeful skilled movements
- can brush teeth at home but not demonstrate it when asked to
What are the steps in motor control of action under a verbal instruction?
- auditory systems process instruction (Wernickes)
- prefrontal cortex activates goal-directed motor action
- posterior sensory regions specify movement goals in association with sensory info
- instructions are generated by PFC and sent to premotor and SMA for movement organization and programming and then to primary motor cortex for execution
What is buccofacial/oral apraxia?
- difficulties performing learned voluntary movements with the muscles of the face, lips, tongue, cheeks, and larynx on command
What is buccofacial/oral apraxia caused by?
- associated with frontotemporal lesions
- frontal and central opercula
- anterior part of insula
What is limb-kinetic apraxia?
- impaired fine/precise movements with contralateral limb
- most evident in rapid distal finger movement (tapping)
- mostly contralateral R hand but sometimes ipsilateral
What is ideomotor apraxia?
- perseveratie errors
- sequencing errors
- spatial errors
- timing errors
What is ideational apraxia?
- inability to carry out a series of acts and ideational plan
What is conceptual apraxia?
- content errors are commonly observed (using tool like another tool)
What is constructional apraxia?
- unable to draw or build with lego
What is dressing apraxia?
- unable to dress properly (head in arm hole, pants backwards)
