Functional Neuroanatomy Flashcards
What are the three main components of the brain
1) Forebrain: cerebral hemispheres and diencephalon
2) Midbrain
3) Hindbrain (brainstem): medulla, pons, and cerebellum
What does ventral/dorsal mean?
Inferior/Superior
What does rostral/caudal mean?
Anterior/Posterior
What is the horizontal Plane?
Parallel to the floor
What is the coronoal plane?
Perpendicular to the floor and cuts across the brain (wearing a crown)
What is the saggital plane?
Perpendicular to the ground from forehead to occiput (like an archer shooting arrow with a bow)
What is grey matter?
- Cell bodies of neurons
- Basic synaptic communication occurs here
What is white matter?
- Myelinated axons
- Tracts provide communication among cortical areas and between cortical and subcortical structures
- Disconnection syndromes arise from damage to WM pathways
What are the three main regions of the frontal lobe?
- Orbitofrontal/ventromedial region
- Dorsolateral region
- Dorsomedial region
What are the main functions of orbitofrontal and ventromedial regions?
- Emotion regulation, reward monitoring, and personality
- Damage to orbitofrontal= disinhibition
- Damage to ventromedial= disordered reward/punishment processing
What are the main functions of the dorsolateral region?
- Cognitive-executive functions including working mem
- Damage= dysexectuive syndromes, poor WM and inattention
What are the main functions of the dorsomedial region?
- Intentional and behavioral activation
- Damage= impairment in initiated behavior (e.g., akinetic mutism)
What are the three main areas in the temporal lobes?
- Temporal polar cortical areas
- Ventral temporal areas
- Posterior temporal region
What is the function of the temporal polar cortical areas?
Important for intersensory integration and semantic memory
What is the function of the ventral temporal areas?
Important for object recognition and discrimination. Bilateral damage produces object or face agnosia
What is the function of the posterior temporal areas?
- Middle and superior temporal sulci
- Primary auditory areas and Wernicke’s area in language dominant hemisphere
- Important for language comprehension
Name the three main components of the parietal lobe.
- Superior parietal lobe
- Tempoparietal junction
- Inferior parietal lobe
What is the function of the superior parietal lobe?
Important for sensory-motor integration, body schema, and spatial processing
What is the function of the tempoparietal junction?
- Important for phonological and sound based processing
- Language comprehension (left) and music comprehension (right)
What is the function of the inferior parietal lobe?
Important for complex spatial attention, integration of tactile sensation, and self-awareness
What are the two main pathways of the occipital lobe?
Origin of two main visual-cortical pathways: ventral and dorsal
What is the ventral visual pathway?
- Connects occipital and temporal lobe
- Object and face recognition, item-based memory, and complex visual discrimination
- Processes structural and feature based information
What is the dorsal visual pathway?
- Connects the occipital and parietal lobes via the superior temporal sulcus
- Spatial vision and visuomotor integration
- Processes spatial information
- Visuomotor interaction in the environment
How many layers does the neocrotex have?
- Has 6 layer laminar structure
- Each layer has distinct output connections
- Layer IV= inputs from the thalamus
- Layers II and III= cortico-cortico connections
Where do retinal ganglion cells project?
-Send axons into the optic nerve & projects posteriorly
Optic chiasm
- Optic nerve comes together to form the optic chiasm
- Optic tracts originate here
What is the geniculostriate pathway and it’s main function?
- Optic tract fibers –> LGN of the thalamus–>primary visual cortex (BA 17; striate cortex) in the occipital pole
- Visual discrimination and form perception
What is the tectopulvinar pathway and it’s main function?
- Optic tract fibers–>pretectal & superior colliculus–>parietal & frontal association cortex via the pulvinar nucleus of the thalamus
- Pupillary light reflex, attention-directed eye movements, orientation to visual stimuli
- Movement rather than form perception
How many layers does the archicortex have?
- 3 layers
- Limbic cortex
What substrates are in the hippocampus, and what is it’s main purpose?
- Consists of dentate gyrus, sectors of Ammon’s horn (CA 1-4) and subiculum
- Archicortical and more closely related to the neocortex than the amygdala
- Critical for episodic memory
Describe the trisynaptic circuit.
- Internal connections of the hippocampus
- Entorhinal cortex–>dentate granule cells (synapse 1)–>CA3 mossy fibers (synapse 2)–>CA 1 (synapse 3)–>subiculum–>entorhinal cortex
- Unidirectional connections
What is the subiculum?
-Major source of hippocampal efferent projections
What is the parahippocampal region?
- Rhinal (entorhinal and perirhinal) cortex
- Pre- and parasubicular cortex
- Parahippocampal cortex
Describe the entorhinal cortex.
- The final and common pathway to the hippocampus
- Receives afferents from the perirhinal cortex and the parahippocampal gyrus, which gets projections from association cortex
- Provided with indirect access to information processed in the cortex
What is the ventral temporal lobe memory stream?
Unimodal (primary visual) cortical areas–>perhirhinal cortex–>lateral entorhinal cortex–> HC CA1 and CA3
What is the dorsal temporal lobe memory stream?
Parietal and frontal association areas–>parahippocampal cortex–>medial entorhinal cortex–> HC CA1 and CA3
What are the three main subcortical projections from the hippocampus?
1) CA1, CA3, & subiculum–>precommissural fornix–>lateral spetal nucleus
2) Subicual projections–>postcommissural fornix–>anterior nucleus of the thalamus or mammillary bodies
3) Hippocampus–>amygdala, nucleus accumbens, or other BF regions & ventromedial hypothalamus
What is Papez’s Circuit?
hippocampal–>postcommissural fornix–>mamillary body
-explains how the hypothalamus and cortex coordinate emotion-cognition interaction
What is the medial limbic circuit?
Hippocampus–>mamillary bodies (via fornix)–>anterior thalamus (via mamillothalamic tract)–>cingulate gyrus–>hippocampus
What is the lateral limbic circuit?
Amygdala–>dorsomedial nucleus of the thalamus (via the ventral amygdalofugal pathway )–>orbitofrontal cortex–>uncinate fasiculus–>amygdala
What are the two main parts of the amygdala?
- Anterior to the hippocampus
- Two main parts:
(1) large basolateral group of nuclei: connect to limbic systems, association cortex, and dorsomedial thalamus
(2) smaller corticomedial segment: extensive connections with BF, hypothalamaus, and brainstem - Derived from paleocortex
- Responsible for emotional aspects of cognition
Who was H.M.?
- Scoville and Milner (1957)
- Posterior resections involving the hippocampus and parahippocampal gyrus produced amnesia that was severe
What is the two-systems theory of amnesia?
-Amnesia occurs when both the lateral and medial limbic circuits are damaged
Lesions restricted to either pathway alone cause less severe memory disturbance
What occurs when there are anterior and posterior medial thalamic lesions?
Causes severe amnesia; if only one is affected there is little memory disturbance
What occurs with collateral damage to the perirhinal cortex?
- Responsible for memory deficits after amygdala lesions
- Damage to the perirhinal and parahippocampal cortices produces amnesia equivalent to that of the two systems theory of amnesia, even when the hippocampus and amygdala are spared
What is the thalamus?
-Important sensory relay nucleus
Critical functions in higher cognitive processes including alertness, activation, and memory
-Comprised of multiple nuclear groups
-Includes myelinated fiber tracks called the internal medullary lamina
What is the internal medullary lamina?
- Separates the nuclear groups of the thalamus into ventral-dorsal and anterior-posterior planes
- Includes memory relevant fibers of the mamilothalamic tracts (travles to the anterior thalamus) and ventral amygdofugal pathways (travels to the dorsomedial thalamus)
What is thalamic amnesia?
-Occurs due to disruption of both the IML and mamillothalamc tracks