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183 Cards in this Set
- Front
- Back
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Prefrontal region, aka:
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seat of judgement
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Therapeutic lesions in prefrontal regions
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mid 20th centruy
alleviate pathological anxiety, phias, disruptive emotional outbursts eliminate emotional awareness and prudential judgement |
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connections from amygdala to prefrontal cortex critical to what?
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role of emotions in behavioral organization
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2 types of amygdala - prefrontal cortex connections
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direct amydgalo-cortical fibers
connections from amygdala through dorsomedial nucleus of the thalamus |
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connections from prefrontal cortex to posterior association regions of cortex provide what?
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provide cognitive bases for making adequate judgements about behavioral choices
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Thalamic connections of PREFRONTAL cortex
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dorsomedial nucleus of the thalamus
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location of prefrontal cortex
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rostral most part of cerebrum
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Premotor regions
2 reasons why called "premotor" |
spatial - rostral to 1* motor cortex
temporal - activity in premotor cortex generally precedes activity in neighboring motor cortex |
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roles of cortex regions in courses of action
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course of action
selected in prefrontal cortex organized in premotor cortex executed in motor cortex (rostral to caudal) |
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Lesions of premotor cortex result in
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APRAXIA
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Apraxia
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impairment of learned performance in the absence of paralysis
(i.e.: motor units work fine, but they cannot be organized into meaningful, learned activity) |
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Agraphia
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Apraxia when the activity is writing
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Motor aphasia
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Apraxia when the activity is speaking
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Motor aphasia is produced the the destruction of...
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Broca's motor speech area
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In most individuals, Broca's area is located where?
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Left hemisphere only
(variations: right hemisphere or both hemispheres) |
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Frontal eye field
location function lesion |
Frontal eye field
location: border btw Premotor and Prefrontal regions stimulation causes deviation of both eyes to opposite side lesions cause conjugate deviation of eyes toward side of lesion |
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Thalamic connections of PREMOTOR cortex
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largely with VENTRAL ANTERIOR NUCLEUS
VA nucleus receives input from basal ganglia |
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Primary motor region
location |
Rostral to central sulcus
Caudal to premotor region |
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Primary motor region
low levels of electrical stimulation cause... |
contractions on CONTRALATERAL side of body
not of individual muscles, but of organized groups of muscles |
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Somatotopy of primary motor regions
lower body regions - upper body regions - |
Primary motor region
lower body - superior and medial portions of gyrus upper body - inferior and lateral portions of tyrus |
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Lesions of primary motor cortex
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severe effects on voluntary movements
soon after lesion - contralateral paresis of related body part some recovery usually occurs, but impairments of movements of more distal limb muscles remain |
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Extensive connections exist between 1* motor cortex and neighboring ____ and _____ cortices
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Extensive connections exist between 1* motor cortex and neighboring PREMOTOR and PRIMARY SOMATOSENSORY CORTICES
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Thalamic connections of PRIMARY MOTOR CORTEX
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VENTRAL LATERAL NUCLEUS
VL nucleus receives input from the cerebellum |
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Cerebellum exerts control on premotor cortex via what structure?
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ventral lateral nucleus of thalamus
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3 somatosensory regions
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primary somatosensory region
secondary somatosensory region somatosensory association region |
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Primary somatosensory region, aka:
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Primary Somesthetic region
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Sensory represenations of _____ body parts are arranged somatotopically in primary somatosensory region
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CONTRALATERALLY
(primary somatosensory cortex deals with sensory information from contralateral body) |
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pre- and post-central gyri
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parallel somatotopic representations of contralateral body parts
= SENSORIMOTOR STRIP |
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Primary somatosensory region
location |
lies immediately caudal to central sulcus/primary motor region
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Secondary somatosensory region
location |
lies between primary somatosensory and auditory regions
on dorsal wall of lateral sulcus at lateral end of postcentral grus (internal to lateral sulcus - not visible from surface view) |
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functional and clinical signficance of secondary somatosensory region
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unknown
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lesions of primary somatosensory region
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deleterious effect on TACTILE sensation and DISCRIMINATION ability (also hard to localize pain)
impair sensations of BODY POSITION and MOVEMENT CONTRALATERAL to lesion |
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Somatosensory association region
location |
immediately caudal to pirmary somatosensory region
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Somatosensory association region
function |
necessary to tactile identification
(as opposed to tactile awareness) |
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Lesions in somatosensory association region
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NEGLECT - of contrateral side of body
TACTILE AGNOSIA ASTEREOGNOSIS |
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NEGLECT
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seeming unawareness of part of body
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AGNOSIA
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inability to recognize objects
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ASTEREOGNOSIS
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inability to correlate texture, shape, size and weight of objects physically present
with previous experience of those objects |
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Paresis
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weakness in movement
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Thalamic connections of PRIMARY SOMATOSENSORY CORTEX
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VENTRAL POSTERIOR NUCLEUS
VPL/VPM receive major somatosensory pathways from spinal cord and brainstem, including medial lemniscus |
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Visual regions (2)
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Primary visual region
Visual association region |
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Primary visual region
location |
walls of calcarine sulcus
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Primary visual region contains...
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somatotopic representation of the retina
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visual cortex "sees" what?
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each visual cortex sees the CONTRALATERAL half of the VISUAL FIELD of BOTH EYES
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Lesions of the primary visual region result in..
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SCOTOMAS (blind spots) in CONTRALATERAL visual field
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SCOTOMA
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blind spot
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Visual association region
location contains... |
surrounds primary visual cortex
contains a second somatotopic representation of the retina |
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Lesions in visual association regions produce....
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VISUAL AGNOSIA
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VISUAL AGNOSIA
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awareness of object in visual field, but inability to identify it
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Thalamic connections of PRIMARY VISUAL CORTEX
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Lateral Geniculate Nucleus
LGN receives its major input from retinas |
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Thalamic connections of visual association regions
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lateral geniculate nucleus
& Pulvinar nucleus |
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Primary Auditory cortex
location |
lies in and around a pair of parallel sulci on lower bank of lateral sulcus
dorsal (upper) aspect of superior temporal gyrus |
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Heschl's convolution/gyrus
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area of primary auditory cortex
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Primary auditory cortex
contains... |
somatotopic representation of cochleas of the inner ears
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In the primary auditory cortex, both sides...
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In the primary auditory cortex,
BOTH SIDES GO TO BOTH SIDES |
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Effect of entire auditory system being represented in each hemisphere with respect to primary auditory region lesions
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lesions of the primary auditory cortex must be BILATERAL and SYMMETRICAL to result in deafness
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Auditory Association and Sensory Language regions
location |
cortex surrounding primary auditory area
contains additional somatotopic represenations of cochleas |
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Planum temporale
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immediately caudal to primary auditory region
flat gyral surface on dorsal (upper) aspect of superior temporal gyrus |
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preeminent example of morphological assymetry in the human brain
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in a slight majority of cases, planum temporale is noticeably larger in the left than in the right hemisphere
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Sensory Language Region, aka:
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Wernicke's area
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In most individuals, Wernicke's area lies exclusively in...
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the LEFT hemisphere
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Wernicke's area includes which 3 things?
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planum temporale
supramarginal gyrus angular gyrus |
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Lesions of Wernicke's area result in...
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SENSORY APHASIA
AUDITORY AGNOSIA (lesions closer to primary auditory region) ALEXIA (lesions closer to visual cortex) |
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SENSORY APHASIA
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inability to understand language, written, spoken, or both
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AUDITORY AGNOSIA
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word deafness - word is head, but not understood
does NOT involve ability to read |
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ALEXIA
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inability to read
NOT involve comprehension of spoken language |
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Thalamic connections of PRIMARY AUDITORY CORTEX
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Medial geniculate nucleus
MGN receives input from brainstem auditory pathways through brachium of the inferior colliculus |
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Thalamic connections of Auditory Association and Sensory Language Regions
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Medial geniculate nucleus
& Pulvinar nucleus |
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Temporal association regions
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chain of connections
- begin in visual cortex - lead to amygdala in temporal pole similar chains leading to temporal pole |
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Grandmother cells
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near temporal pole
cells that repond exclusively to complicated stimuli represent features built up during experience of subject - recognize faces, for example, of someone remembered from childhood (e.g.: one's grandmother) |
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Experience tapes
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part of temporal association regions
when region stimulated, patients report detailed "flashbacks" like the playing of tapes of earlier experiences |
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Lesions in inferior part of boundary between temporal and occipital lobes
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at posterior edge of temporal association regions
AHCROMATOPSIA PROSOPAGNOSIA |
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ACHROMATOPSIA
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loss of color vision - grayscale vision
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PROSOPAGNOSIA
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faces can be perceived, but not identified as belonging to particular persons
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Isocortex
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aka: neocortex
comprises most of human cerebral cortex 6-layered structure most subcortical information comes through thalamic nuclei |
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Allocortex
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aka: limbic cortex
around peripheral rim of cerebral hemispheres where they meet at diencephalon includes hippocampal formation & primary olfactory and entrorhinal cortex |
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2 ways neurons in isocortex are classified
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connections
morphology |
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Neurons classified by connections
Output/Input |
Projection neurons - axons leave cortex
Association - axons travel between cortical regions in same hemisphere Commissural - axons travel between cortical aregions in opposite hemisphres |
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For both input and output, association, commissural and projection connections are roughly equal in number.
What is the significant conclusion? |
Most (~2/3) of cerebral cortical information is derived from, and sent to, the cerebral cortex.
ISOCORTEX TALKS MAINLY TO ITSELF |
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4 ways by which cerebral cortex converses with itself
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(1) corticocortical communication
(2) corticothalamic communication (3) corticostriatal communication with basal ganglia (4) corticocerebellar communication |
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Most of the neurons in the isocortex are classified as...
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pyramidal cells
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morphology of pyramidal cells
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single, many-branched APICAL dendrite
& radiating arrays of BASAL dendrites |
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all cortical output travels by means of...
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axons of pyramidal cells
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NT of pyramidal cells
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glutamate
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Which cells does alzheimer's affect?
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pyramidal neurons
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6 layers of isocortex
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molecular
external granular external pyramidal internal granular internal pyramidal multiform |
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in which layers of isocortex are the most association and commissural neurons found?
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external granular
external pyramidal |
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molecular layer of isocortex
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layer 1:
tangential axons, branches of apical dendrites, a few internerons |
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external granular layer of isocortex
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layer 2:
small pyramidal cells interneurons |
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external pyramidal layer of isocortex
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layer 3:
larger pyramidal cells |
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internal granular layer of isocortex
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layer 4:
dense interneurons many terminations of incoming fibers |
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internal pyramidal layer of isocortex
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layer 5:
largest pyramidal cells some interneurons |
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multiform layer of isocortex
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layer 6:
many differnt mophological cell types |
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which isocortex layer has the most projection neruons?
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layer 5: internal pyramidal layer
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in which isocortex layer do the corticospinal and corticobulbar tracts originate?
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layer 5: internal pyramidal layer
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in which isocortex layer do most corticothalamic cell originate?
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layer 6: multiform
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types of fiber bundles and bands in isocortex
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radial bundles
tangiential bands |
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radial bundles in isocortex
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mainly axons entering and leaving cortex
apical dendrites |
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tangential bands of isocortex
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prominent in sensory regions, where there is a concentration of thalamic input
outer and inner lines of Baillarger - either side of layer 5 line of Gennari - outter line of Baillarger in striate area |
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granulous cortex
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aka: koniocortex
found in primary visual, auditory and somatosensory regions an enlarged layer 4 blends layers 2-5 |
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agranular cortex
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motor and premotor regions: layer 5 overshadows layer 4
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Structure of Brodmann's map of cytoarchitectural regions of the cerebral cortex
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sectioned in horizontal plane
assigned numbers to distinctive areas as encountered on the way down from dorsal (upper) surface (regions on top have small numbers; regions on bottom have big numbers) |
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Bodmann's areas for Primary somatosensory region
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3, 1, 2
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Bodmann's areas for primary motor area
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4
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Bodmann's areas for somatosensory association region
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5, 7
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Bodmann's number for premotor region
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6
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Bodmann's number that includes frontal eye field
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8
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Bodmann's number for primary visual region (aka: striate cortex)
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17
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Bodmann's number for visual association region
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18, 19
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Bodmann's number for Wernicke's area
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39, 40
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Bodmann's number for primary auditory region
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41, 42
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Bodmann's number for Broca's motor speech region
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44, 45
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Thalamic nuclei receive far _____ fibers from isocortex than they send to isocortex.
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Thalamic nuclei receive far MORE fibers from isocortex than they send to isocortex.
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Effect of corticothalamic send/receive imbalance.
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you don't think about all information your body's receiving.
i.e.: tuning out speaker during lecture or not feeling clothes on back while eating, etc. |
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Cortex has ____ influence on incoming information than do external events.
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Cortex has MORE influence on incoming information than do external events.
Cortex talks mainly to itself. It also controls and modifies any extraneous information getting into the conversation. |
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Dendrites of pyramidal cells receive local and specific information from which 3 major sources?
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ipsilateral cortex (association fibers)
contralateral cortex (commissural fibers) dorsal thalamus (thalamocortical projection fibers) |
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modulatory inputs to isocortex come from what type of regions?
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neurochemically specialized subcortical regions
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6 modulatory inputs to isocortex
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cholinergic projections from basal nucleus of meynert
noradrenergic projections from locus ceruleus sertonergic projections from dorsal raphe nuclei in midbrain dopamingergic projections histaminergic projections from posterior hypothalamus GABAnergic projections from caudal hypothalamus |
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What qualities muct cortical lesions have to have detectable effects?
Exceptions? |
to have detectable effects, cortical lesions must be:
EXTENSIVE & BILATERAL except for lesions of the 1* SENSORY REGIONS SENSORY & MOTOR LANGUAGE REGIONS |
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equipotentiality
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ability of any cortical region to take on any variety of functional roles
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why are cortical lesion effects often short in duration?
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because of plasticity and equipotentiality of cortex
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Major types of association fibers
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short fibers - connect adjacent gryi
long fibers - connect more distant areas of same hemisphere |
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Major bundles of association fibers
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cingulum
superior longitudinal fasciculcus (arcuate fasciculus) superior occipitofrontal fasciculus arcuate fibers |
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commissural fibers
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corpus collosum
-trunk and radiations -splenium and genu - rostrum anterior commissure |
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projection fibers
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internal capsule
external capsule |
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internal capsule
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axons from grey matter project into white matter
come to a point as in the end of a funnel point lies between telencephalon and diencephalon all fibers in/out of thalamus must pass through lesion is devastating |
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Anatomical parts of lateral ventricles
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central part
frontal, occipital and temporal horns interventricular foramen (foramen of Monro) choroid plexus attached to margins of choroid fissure |
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hydrocephaly
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enlargement of lateral ventrical
--> intracranial pressure |
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Largest diencephalic subdivision
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thalamus
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shape and location of thalamus
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right and left thalamus:
egg-shaped masses separated by third ventrical (except for masa intermedia) on each side, thalamus located between -posterior limb of internal capsule - third ventricle |
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Internal medullary lamina
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band of myelinated fibers
enters/leaves various thalamic nuclei divides thalamus into three gray masses (nuclear groups) |
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3 nuclear groups of thalamus
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lateral nuclear group
medial nuclear group anterior nuclear group |
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largest nucleus of medial nuclear group of thalamus
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dorsomedial nucleus
(aka: mediodorsal nucleus) |
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2 major subdivisions of lateral group of thalamic nuclei
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dorsal tier nuclei
- lateral dorsal nucleus - lateral posterior - pulvinar ventral tier nuclei -ventral anterior -ventral lateral -ventral posterior |
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caudal extension of ventral tier of thalamic nuclei
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meta-thalamus - consists of:
medial and lateral geniculate bodies |
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intralaminar nuclei
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lie within the internal medullary lamina
rostral and caudal groups |
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external medullary lamina
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contained within anterior and lateral surfaces of thalamus
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reticular thalamic nucleus
location |
extends along lateral aspect of thalamus
lies outside external medullary lamina sandwiched between -external medullary lamina -internal capsule |
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only type of sensory information that does not pass through the thalamus
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smell
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Gateway to cerebral cortex
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thalamus
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where does general anaesthesia function
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in the thalamus
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reticular nucleus of the thalamus
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thalamocortical and corticothalamic fibers give off collaterals to the reticular nucleus
reticular nucleus neurons project to other thalamic nuclei thalamic intercommunications |
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noncortical structures that receive thalamic input
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hypothalamus
dorsal striatum - caudate nucleus - putamen |
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are most thalamic nuclei interconnected?
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NO
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Synapses from the thalamic reticular nucleus and the interneurons of other thalamic nuclei are _____
all other synapses in the thalamus are _____ |
Synapses from the thalamic reticular nucleus and the interneurons are INHIBITORY
all other synapses in the thalamus are EXCITATORY |
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Reticular thalamic nucleus
afferents efferents |
Reticular thalamic nucleus
afferents - thalamocortical and corticothalamic collaterals efferents - thalamic nuclei that give rise to collaterals of thalamocortical fibers |
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Reticular thalamic nucleus
function |
modulates exchange of signals between thalamus and cerebral cortex
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Medial geniculate nucleus
structure/location receives... projects... |
Medial geniculate nucleus
swelling on posterior surface of thalamus, beneath the pulvinar nucleus receives info from auditory system prjects bilaterally to 1* & 2* auditory cortex |
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Medial geniculate nucleus
afferent connections efferent connections |
medial geniculate nucleus
afferent connections - inferior colliculus via inferior brachium (bilateral input, but primarily from contralateral ear) - input from auditory cortex efferent connections - auditory cortex (areas 41, 42) of temporal lobe |
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Lateral geniculate nucleus
structure/location |
beneath pulvinar nucleus
6 layers of neurons |
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Lateral geniculate nucleus
afferent connections efferent connections |
Lateral geniculate nucleus
afferent connections - retina of both eyes --- via optic tract & 1* visual cortex (17) efferent connections - 1* visual cortex |
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Ventral posterior nucleus
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nucleus of termination of genral sensory and gustatory pathways
relays information to cerebral cortex aka: ventrobasal complex |
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2 parts of ventral posterior nucleus of thalamus
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ventral posterolateral (VPL)
ventral posteromedial (VPM) |
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ventral posterolateral region of thalamus (VPL)
afferent connections efferent connections |
VPL
afferent connections - lateral spinothalamic tract - medial lemniscus - anterior spinothalamic tracct - somatosensory cortex efferent connections - point to point projections to 1* & 2* somatosensory cortex |
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somatotopic organization in VPL
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lower limb - posterolateral
trunk - intermediate upper limb - anteromedial |
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ventral posteromedial region of thalamus (VPM)
afferent connections efferent connections |
VPM
afferent connections - information about taste ---- from solitary nucleus, trigeminothalamic tract and somatosensory cortex efferent connections - same as VPL, but to area of postcentral gyrus for head/face |
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Topographical modality organization in VPM
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taste - medial
tactile - lateral temperature - intermediate |
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Posterior thalamic nucleus
afferent connections efferent connections |
Posterior thalamic nucleus
afferent connections - bilateral input - not modality specific -- spinothalamic tracts -- medial leminiscus -- somatosensory cortex Efferent connections - somatosensory cortex |
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Are posterior thalamic neurons modality specific?
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NO
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Ventral Lateral nucleus and Ventral Anterior nucleus form integral parts of which 2 feedback circuits
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VL:
1* motor cortex --> cerebellum --> thalamus --> 1* motor cortex VA: premotor cortex --> basal ganglia --> thalamus --> premotor cortex |
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afferent connections of ventral lateral nucleus
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deep cerebellar nuclei of contralateral cerebellum (dentatothalamic tract)
ipsilateral globus pallidus (thalamic fasciculus) premotor and motor cortex |
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efferent connections of ventral lateral nucleus
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premotor cortex
motor cortex |
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role of VL nucleus
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main subcortical gateway from motor cortex
prime mover of motor pathways |
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role of ventral anterior nucleus (VA)
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recruiting responses in widespread cortical areas
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afferent connections of VA nucleus
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globus pallidus
substantia nigra brainstem reticular formation intralaminar nuclei cerebral cortex (areas 6 & 8) |
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efferent connections of VA nucleus
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premotor cortex
areas of frontal cortex intralaminar nuclei orbitofrontal cortex |
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Lateral group nuclei - dorsal tier
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lateral dorsal nucleus (LD)
lateral posterior nucleus (LP) Pulvinar nucleus |
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Lateral dorsal nucleus is functionally part of which group?
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anterior group
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Pulvinar nucleus is involved in which pathways?
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extrageniculate visual pathway
pain perception |
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Pulvinar nucleus
afferent connections efferent connections |
Pulvinar nucleus
afferent connections - superior colliculus - occipital cortex (areas 18, 19) striate cortex (area 17) - parietal and temporal cortex efferent connections - occipital cortex (17, 18, 19) - parietal and temporal cortex |
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Anterior nuclear group
connections |
connected with allocortex and mesocortex
afferents - mamillary bodies, hippocampus, cingulate gyrus efferents - cingulate gyrus |
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Medial nuclear group
function |
concerned with integration of somatic and visceral activities
and aspects of affective behavior and feelings |
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Part of thalamus responsible for specific sensory relay
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ventral tier of lateral nuclear group
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does the ventral tier of the lateral nuclear group modify and integrate sensory inputs before passing them to cortex?
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YES
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Thalamic syndrome
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In certain thalamic lesions, after a brief inititial stage of complete contralateral anestheisa, some sensations return
these sensations are now poorly localized & accompanied by unpleasant feeling |
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Cerebral cortex allows _____ of sensation
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Cerebral cortex allows LOCALIZATION of sensation
therefore, if thalamus is intact, but lesion in cortex, the patient can feel pain, but cannot localize it |
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Internal capsule
definition |
one portion of a continuous sheet of fibers profecting to and from the cerebral cotex
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Fibers of internal capsule convey...
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almost all the neural input to and output from the neocortex
driect lines of communication with subcortical nuceli, esp. thalamus, brainstem & spinal cord |
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continuous sheet of which internal capsule is a part
extends in 3 directions |
superiorly: corona radiata of cerebral white matter to cerebral cortex
middle: internal capsule of the diencephalon inferiorly: cerebral peduncle or crus cerebri of the midbrain |
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Internal capsule is subdivided into (5 things)
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anterior limb
genu posterior limb retrolentiform portion sublentiform portion |
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significance of posterior limb of internal capsule
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contains all communication between cortex and thalamus:
sensory, visual and auditory info |
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where is the anterior limb of the internal capsule located?
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between
- head of caudate nucleus - lenticular nucleus |
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where is the posterior limb of the internal capsule located
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between
- thalamus - lenticular nucleus |
