Neuroanatomy Flashcards
anatomico-clinical correlation
the process of integrating anatomic knowledge and understanding of behavioral and cognitive syndromes
divisions of the brain
human nervous system composed of the CNS (brain and spinal cord) and the peripheral nervous system
the brain is divided into the forebrain (hemispheres and diencephalon), midbrain, hindbrain (medulla, pons, cerebellum - together form connection bw brain and spinal cord)
forebrain
hemispheres and diencephalon (epithalamus, thalamus, subthalamus, and hypothalamus)
midbrain
the colliculi, the tegmentum, and the cerebral peduncles
hindbrain
medulla, pons, cerebellum - together form connection bw brain and spinal cord
diencephalon
epithalamus, thalamus, subthalamus, and hypothalamus
front-back direction
ventral and dorsal
up-down direction
rostral/superior and caudal/inferior
horizontal (axial) plane
parallel to the floor
coronal plane
perpendicular to floor and cuts across brain connecting the ears
sagittal plane
perpendicular, from forehead to occiput
gray matter
cell bodies/neurons
where basic synaptic communication takes place
white matter
myelinated axons
provides communication among cortical areas and between cortical and subcortical structures over longer distances
how do disconnection syndromes arise?
damage to white matter pathways when functional brain regions are deprived of inputs and outputs thru white matter damage
examples: Alexia without agraphia, optic aphasia, impaired naming of objects in left hemisphere due to callosal disconnection of right hemisphere from left-hemisphere language regions
unimodal cortex
processes info to a specific sensory modality
plays prominent role in perception
polymodal cortex
process info receiving from disparate modalities thru afferent connections
critically involved in higher-order conceptual processes that are less dependent on concrete sensory info than on abstract features extracted from multiple inputs
example: convergence zone of anterior temporal lobe and inferior parietal lobule
orbitofrontal/ventromedial region
emotional regulation, reward monitoring, personality
damage to orbitofrontal: disinhibition
damage to ventromedial: disordered reward/punishment processing and problems marking perceptual or learning experiences with reward value and emotional significance
dorsolateral region
broad range of cognitive-executive functions
damage produces dysexecutive syndromes, impairment in working memory, poor attentional control of behavior
dorsomedial region
intentional and behavioral activation
damage produces striking impairments in initiated behavior including akinetic mutism (awake and alert but unable to move or speak)
temporal polar cortical areas
polymodal convergence zone important for intersensory integration and semantic memory
ventral temporal areas
object recognition and discrimination
bilateral damage produces object or face agnosia
ventral temporal areas
object recognition and discrimination
bilateral damage produces object or face agnosia
ventral temporal areas
object recognition and discrimination
bilateral damage produces object or face agnosia
posterior temporal region
middle and superior temporal sulci, which contains primary auditory areas and Wernicke’s in language-dominant hemisphere
important for language comprehension, prosodic comprehension in homologous non-dominant hemisphere
superior parietal lobe
sensory-motor integration, body schema, spatial processing
temporal parietal junction
phonological and sound-based processing, language comprehension (left), music comprehension (right)
inferior parietal lobule
complex spatial attention, integration of tactile sensation, self awareness
primary visual cortex
surrounds the calcimine fissure
complete damage: cortical blindness or (rarely) Anton’s syndrome (denial of cortical blindness) or blindsight (detection of unconsciously perceived stimuli in blind field)
partial damage: visual field defects that reflect region of visual cortex damaged
ventral visual pathway
connects occipital and temporal lobe
object and face recognition, item-based memory, complex visual discrimination
impairment: perceptual disturbance, when severe, agnosia
dorsal visual pathway
connects occipital and parietal lobes via superior temporal sulcus
spatial vision and visuomotor integration
likely involved in visuomotor integration (reaching, manipulating objects)
impairment here: spatial perception, attention, visuomotor processing (hemispatial neglect, visual reaching)
frontal lobe subdivisions
orbitofrontal/ventromedial
dorsolateral
dorsomedial
temporal lobe subdivisions
temporal polar cortical
ventral temporal
posterior temporal
parietal lobe subdivisions
superior parietal
temporoparietal
inferior parietal
occipital lobe subdivisions
primary visual cortex
visual association cortex
the 2 main visual-cortical pathways: ventral and dorsal
geniculostriate pathway
critical to visual discrimination and form perception
retinal ganglion cells in each eye send their axons into the optic nerve, which project posteriorly and come together at optic chasm, where optic tract originate. Optic tracts fibers end in the lateral geniculate nucleus of the thalamus, which projects to primary visual cortex in striate cortex in occipital pole
tectopulvinar system
subserves pupillary light reflex, attention-directed eye movements, and general orientation to visual stimuli and is more sensitive to movement than form
what are the anatomically separate visual input channels?
form, motion, and color
apperceptive agnosia
when disorder results from impairment in processing basic visual elements of objects (shape, contour, depth)
due to damage to visual association areas
associative agnosia
when disorder results from relating a well-perceived stimulus to stored representations based on prior experience with the stimulus
die to less extensive or disconnecting lesions in regions between association cortex and memory
amnestic syndrome
severe memory disorder
focal damage to medial temporal lobes, medial diencephalon, basal forebrain
two-system theory of amnesia
amnesia occurs when lateral and medial limbic circuit are damaged
lesions that interrupt both the fornix (disrupting papez’s circuit) and the ventral amygdalofugal (disrupting the lateral circuit) pathways cause severe amnesia; lesions to either alone cause less severe amnesia
conclusions about the temporal lobe and amnesia
- damage to cortical and subcortical subcortical structures within the temporal lobe, whether focal or extensive, can cause amnesia
- amnesia most likely results from damage to both hippocampically based medical limbic circuit and amygdala-based lateral limbic circuit
- damage to individual elements of these circuits can all result in amnesia, provided both circuits are damaged
- hippocampus critical for episodic memory, amygdala more involved in emotional aspects of cognition, including emotional memory and assigning emotional significance to stimuli
thalamus
sensory relay nucleus
higher cognitive functions such as alertness, behavioral activation, memory
areas associated with amnesia
medial temporal, thalamic, BF, parahippocampal gyrus
brain hemisphere language dominance
in the left for over 95% of right handers and more than 60-70% of left handers
initial perceptual steps of language processing that enable phonological sequences to be identified and comprehended as words
wernicke’s and adjacent brodmann areas (37, 39, 40)
damage here produces fluent aphasia
articulation of speech sounds and production of words and sentences
primary motor cortex, begins in Broca’s (plans and activates sequences of speech sounds)
damage here produces confluent aphasia with intact comprehension
repetition of language
phonological representation generated by processing in wernicke’s is converted to motor-articulatory sequences and utterances in broca’s
what connects wernicke’s and broca’s
arcuate fasciulus - larger in left hemisphere
damage here produces deficit in repetition, with sparing comprehension and fluency (conduction aphasia)
areas that connect with broca’s and are necessary for processing syntax and grammatical structure of language
frontal lobe regions - prefrontal, premotor, supplementary motor
areas that connect with wernicke’s important for writing and mapping sounds to meaning (lexical semantics)
supramarginal gyri and angular gyri in parietal lobe
prosody location and lesions
processed in the right hemisphere
focal lesions produce aprosodias
damage to inferior right frontal lobe produces deficit in expressing emotional prosody in speech analogous to broca’s
posterior temporal parietal lesions produce deficit in prosody comprehension with fluent production, akin to wernicke’s
cortico-striatal-pallidal-thalamic-loop
cortex to striatum (caudate, putamen) to globus pallidus to thalamus back to cortex
involved in selective engagement: the flexible selection and activation of cortical regions to perform cognitive work
top-down attention
requires interaction with frontal lobe regions involved in volitional deployment of attention and in establishing behavioral priorities in the face of conflicting demands
dorsal frontoparietal system
3 interconnected systems of attention:
orienting to stimuli, alerting, executive
orienting: tuning of perceptual systems to incoming stimuli so relevant sensory info can be selected for further processing; dependent on acetylcholine; involves superior colliculus, pulmonar thalamic nucleus, posterior temporoparietal cortex, frontal eye fields
alerting: state of sensitivity to incoming stimuli; norepinephrine; ascending sensory inputs from the thalamus
executive: monitoring and resolving conflicts among thoughts, feelings, behaviors; dopamine; anterior cingulate cortex and DLPFC
bottom-up information
information that ‘s biased toward salient environmental stimuli
sensory signals arrive at frontal and parietal cortices, having been processed by colliculi and pulvinar
ventral frontoparietal system
dorsal prefrontal cortex
spatial (where’s the door)
ventral prefrontal cortex
object (what)
two visual systems
Dorsal and ventral visual systems
implicated in visual agnosia, spatial neglect, attentional dysfunction
