Exam 2- week 7 ppt 3 Cerebrum functional organization Flashcards
Mapping the cortex has been made into ____ histologically different areas (______ areas)
52 area
Brodmann areas
Details on the mapping of Broadmann areas
~they are not sequentially numbered
~many Brodmann areas correspond to specific functional areas
~there are some important caveats to remember when looking at the maps of Brodmann areas
Are the Brodmann areas exactly the same in everyone?
NO
~there is structural variation between brains so the Brodmann maps for different individuals would be slightly different
Brodmann areas: Caveats
~Variation of distribution of areas between individual brains
~Boundaries between different cytoarchitectonic areas not as distinct as shown on maps
~Because of cerebral plasticity areas can change with time and with differing environmental influences
Brodmann area: Caveat
Details on Boundaries btw cytoarchitectonic areas
~there are gradations of patterns of cell types between one Brodmann area and the next
Brodmann area: Caveat
Details on Brain plastic
~for instance learning motor tasks that stress hand motions, there may be an expansion of the hand region in the cortex. Following amputation, areas of cortex serving the amputated region might disappear to be replaced by neighboring regions of the cortex.
The functional areas of the cortex are divided into (3)
~primary functional areas
~unimodal association areas
~multimodal association areas
location of the primary motor area
~along the precentral gyrus laterally and anterior portion of paracentral lobule medially
Primary motor area’s neurons produce
~specific muscle activation somatotopically arranged
Primary motor area’s muscle pattern of activation called
motor homunculus
Primary motor area:
LE and Trunk are located
medially and dorsal
Primary motor area: UE and face are located
laterally and ventral
Details about innervations and body parts
~size of the body part in this representation is related to innervation density
~innervation density of the muscles of facial expression and of the hand are very high
~these areas have small motor units (number of muscle cells activated by each motor neuron) and large numbers of upper motor neurons
~these areas have a high precision of movement
Location of Primary somatosensory area
along the postcentral gyrus and posterior portion of paracentral lobule medially
Primary somatosensory area’s neuron specifically respond to _ distinct modalities of the somatosensory input (and name them)
5 ~discriminative touch ~pain ~temperature ~pressure ~localized vibratory sense
Details on primary somatosensory area (functional analysis)
~inputs to the post-central gyrus include the integration of superficial & deep mechanoreceptive information for appreciation of position and movement – proprioception
~tactile discrimination for the precise localization of tactile stimuli can be accomplished
~the ability to recognize an object by touch alone (without vision) – stereognosis thought the convergence of different tactile input onto the same neurons and groups of neurons
Primary somatosensory area: differential functions
post central gyrus is not homogeneous in terms of it function but different areas within the post-central gyrus have different patterns of connections and patterns of response to sensory stimuli
Primary somatosensory area: differential functions (area 3)
~BA 3 is considered the primary somatosensory cortex bc it receives dense thalamic inputs and has neurons that are directly and highly responsive to somatosensory stimuli
~BA 3 considered primary somatosensory cortex also because lesions impair somatic sensation very specifically
~Electrical stimulation of BA 3 evokes specific somatic sensory experiences
~BA 3 receives both direct tactile and proprioceptive input
Primary somatosensory area: differential functions (area 1&2)
~BA 1 &2 receives dense inputs from area 3
~BA 1 receives texture info
~BA 2 function emphasizes determination of size and shape
~Lesions in BA 1 & 2 produce predictable dysfunction in texture sensation and size and shape discrimination
~this specificity is not clinically relevant bc you rarely have such discrete lesions of the post-central gyrus
Primary somatosensory area: columnar arrangement
~Areas represented on the cortex correspond to receptor and afferent fiber density with greatest representation of face & hand
~the receptor density is very high the size of receptor fields (area covered by a single receptor unit) is very small in the face and hands
~Like other areas of cortex, somatosensory cortex is arranged in columns
~Adjacent columns represent the same body areas but are alternating between slowly adapting or rapidly adapting neuronal responses reflecting the slow and fast adapting sensory receptors found in the same area of skin
location of the primary auditory cortex
along the most superior aspect of the superior temporal gyrus and into the insular portion of the temporal lobe
primary auditory cortex: tonotopic mappic of pitch
~low frequencies mapping more rostrally (anterior)
~high frequencies mapping ore posteriorly
Location of primary visual cortex
along the medial aspect of occipital lobe, just inferior to and within calcarine sulcus
Details on the primary visual cortex
~respinsice basicaaly only to points of light
~limited patterns of light and dark (such as bars of light)
~there is a retinotopic mapping of PVC with the fovea of the retina represented posterior and the peripheral retina represented more anterior (rostral)
location of primary vestibular area
not as well localized, but is associated with the insula of the parietal lobe
what does the primary vestibular area do?
gives sensation of head position and movement
Lesion in primary somatosensory
lead to loss of tactile localization and conscious proprioception
Lesion in primary auditory
lead to loss of localization of sounds
Lesion in primary visual
leads to loss of field of view called homonymous hemianopia
Lesion in primary vestibular
change in the awareness of head position and movement
Where are the unimodal sensory association cortices?
adjacent to their primary sensory areas
What are the inputs for the unimodal association cortices?
~thalamus
~primary cortex for that sense
What is the principal outputs for the unimodal association cortices?
principal outputs of each of these association cortices are to primary cortex for that sensation
somatosensory association cortex is located
just posterior to the primary somatosensory cortex w largest areas superior medial and inferior lateral
auditory association cortex is located
along superior temporal gyrus
visual association cortex is located
is surrounding the primary visual cortex
Agnosias
inabilities to recognize objects using that sense, even though the primary sense is intact
Agnosias is the results of
lesions to the secondary or association sensory cortices
Astereognosis
~inability to detect an object by touch alone
~damage to the somatosensory association cortex
Visual agnosia
~inability to recognize visual images
~damage to visual association cortex
auditory agnosia
~inability to recognize and identify sounds
~damage to the auditory association cortex
Motor association cortices are located
just rostral to primary motor cortex
what are the 3 parts of motor association cortices?
~premotor cortex
~supplementary motor cortex
~frontal eye fields
location of premotor cortex
rostral and inferior to primary motor cortex
location of supplementary cortex
rostral and superior to the primary motor cortex
location of frontal eye field
rostral to both primary motor cortex and to the supplementary and premotor cortices
Premotor cortex function
to associate group of muscles rather than the individual activation of muscles of the primary motor cortex
Supplementary motor cortex function
in the initiation of movement
Frontal eye field function
coordinates conjugate eye movement
