cerebral cortex Flashcards
- forms a complete covering of the cerebral hemisphere
- composed of gray matter and has been estimated to contain approximately 10 billion neurons
- thickness varies from 1.5 to 4.5 mm
cerebral cortex
The cortex is thickest over the crest of a ___
gyrus
thinnest in the depth of a ___
sulcus
types of nerve cells are present in the cerebral cortex
(1) pyramidal cells
(2) stellate cells
(3) fusiform cells
(4) horizontal cells of Cajal
(5) cells of Martinotti
10 to 50 um long
pyramidal cells
- giant pyramidal cells
- 120 um
- found in the motor precentral gyrus of the frontal lobe
Betz cells
- granule cells
- polygonal in shape
- 8 pm in diameter
- have multiple branching dendrites and a relatively short axon
stellate cells
have their long axis vertical to the surface and are concentrated mainly in the deepest cortical layers
fusiform cells
small, fusiform, horizontally oriented cells found in the most superficial layers of the cortex
horizontal cells of cajal
small, multipolar cells that are present throughout the levels of the cortex
cells of martinotti
- run at right angles to the cortical surface
- include the afferent entering projection, association, and commissural fibers
radial fibers
- run parallel to the cortical surface and are collateral and terminal branches of afferent fibers
- mostly concenrated in layers 4 and 5
tangenital fibers
well developed in the sensory areas due to the high concentration of the terminal parts of the thalamocortical fibers
bands of baillarger
In the visual cortex, the outer band of Baillarger, which is so thick that it can be seen with the naked eye, is known as the ___
stria of Gennari
Because of this obvious band, or stria, the visual cortex in the walls of the calcarine sulcus is sometimes called the ___
striate cortex
- plexiform layer
- most superficial layer
- consists mainly of a dense network of tangentially oriented nerve fibers
molecular layer
- contains large numbers of small pyramidal cells and stellate cells
external granular layer
composed of pyramidal cells, whose cell body size increases from the superficial to the deeper borders of the layer
external pyramidal layer
composed of closely packed stellate cells with a high concentration of horizontally arranged fibers known collectively as the external band of Baillarger
internal granular layer
- Ganglionic layer
- contains very large and medium-size pyramidal cells
internal pyramidal layer
a large number of horizontally arranged fibers form the ___
inner band of Baillarger
- layer of polymorphic cells
- modified pyramidal cells, whose cell bodies are triangular or ovoid
multiform layer
areas of the cortex in which the basic six layers cannot be recognized are referred to as ___
heterotypical
possess six layers
homotypical
- contain densely packed stellate cells
- these cells receive thalamocortical fibers
- found in the postcentral gyrus, in the superior temporal gyrus, and in parts of the hippocampal gyrus
granular type
- granular layers are poorly developed
- layers 2 and 4 are practically absent
- found in the precentral gyrus and other areas in the frontal lobe
agranular type
- situated in the precentral gyrus and includes the anterior wall of the central sulcus and the posterior parts of the superior, middle, and inferior frontal gyri
- almost complete absence of the granular layers and the prominence of the pyramidal nerve cells
precentral area
- The posterior region, which is referred to as the motor area, primary motor area, or Brodmann ___, occupies the precentral gyrus into the paracentral lobule
area 4
The anterior region is known as the premotor area, secondary motor area, or Brodmann ___ and parts of ___. It occupies the anterior part of the precentral gyrus
area 6; areas 8, 44, and 45
- if electrically stimulated, produces isolated movements on the opposite side of the body as well as contraction of muscle groups concerned with the performance of a specific movement.
- muscles of the upper part of the face, the tongue, and the mandible, and the larynx and the pharynx do occur.
primary motor area
Ventral posterior lateral and ventral posterior medial nuclei of thalamus
somatosensory
Lateral geniculate body
vision
Medial geniculate body
auditory
Nucleus solitarius
taste
Olfactory bulb
smell
Thalamus from cerebellum, basal ganglia; somatosensory area; premotor area
fine movements
Primary somesthetic area (B3, 1, and 2), posterior central gyrus
somatosensory
Primary visual area (B17)
vision
Primary auditory area (B41 and 42)
auditory
Posterior central gyrus (B43)
taste
Primary olfactory area; periamygdaloid and prepiriform areas
smell
Primary motor area (B4)
fine movements
Secondary somesthetic area; primary motor area
somatosensory
Secondary visual area (B18 and 19)
vision
Secondary auditory area (B22)
auditory
Secondary olfactory area (B28)
smell
Motor nuclei of brainstem and anterior horn cells of spinal cord; corpus striatum
fine movements
- the function of the ___ is to carry out the individual movements of different parts of the body
- receives numerous afferent fibers from the premotor area, the sensory cortex, the thalamus, the cerebellum, and the basal ganglia
primary motor area
- store programs of motor activity assembled as the result of past experience
- programs the activity of the primary motor area
- involved in controlling coarse postural movements through its connections with the basal ganglia
premotor area
- situated in the medial frontal gyrus to paracentral lobule
- movements of the contralateral limbs, but a stronger stimulus is necessary than when the primary motor area is stimulated
- Removal produces no permanent loss of movement
supplementary motor area
- frontal eye field
- precentral gyrus into the middle frontal gyrus
- Electrical stimulation of this region causes conjugate movements of the eyes, especially toward the opposite side
- control voluntary scanning movements of the eye and is independent of visual stimuli
areas 6, 8, and 9
- motor speech area of Broca
- inferior frontal gyrus and posterior rami of the lateral fissure
- formation of words by its connections with the adjacent primary motor areas
areas 44 and 45
this area is important on the left or dominant hemisphere, and ablation will result in paralysis of speech. In those individuals in whom the right hemisphere is dominant, the area on the right side is of importance. The ablation of this region in the nondominant hemisphere has no effect on speech
areas 44 and 45
- precentral area
- concerned with the makeup of the individual’s personality
- plays a role as a regulator of the person’s depth of feeling. It also exerts its influence in determining the initiative and judgment of an individual
prefrontal cortex
- primary somesthetic area
- postcentral gyrus and posterior part of the paracentral lobule
areas 3, 1, and 2
granular in type, and contains only scattered pyramidal cells
area 3
broad and very obvious
outer layer of baillarger
posterior part of the postcentral gyrus possesses fewer granular cells
areas 1 and 2
- superior lip of the posterior limb of the lateral fissure
- functional significance of this area is not understood
secondary somesthetic area
- somesthetic association area
- parietal lobule extending onto the medial surface of the hemisphere
- this area has many connections with other sensory areas of the cortex, and its main function is probably to receive and integrate different sensory modalities
- enables one to recognize objects placed in the hand with- out the help of vision
areas 5 and 7
- primary visual area
- calcarine sulcus
area 17
central area of the retina and the area for most perfect vision
macula lutea
- secondary visual area
- primary visual area on the medial and lateral surfaces of the hemisphere
- relate the visual information received by the primary visual area to past visual experiences, thus enabling the individual to recognize and appreciate what he or she is seeing
areas 18 and 19
function of this eye field is believed to be reflex and associated with movements of the eye when it is following an object
occipital eye field
- primary auditory area
- situated in the inferior wall of the lateral sulcus
areas 41 and 42
granular type of cortex
area 41
homotypical and is mainly an auditory association area
area 42
Projection fibers to the auditory area arise principally in the medial geniculate body and form the ___
auditory radiation of the internal capsule
of the primary auditory area is concerned with the reception of sounds of low frequency
anterior part
concerned with the sounds of high frequency
posterior part
- secondary auditory area
- superior temporal gyrus
- interpretation of sounds and for the association of the auditory input with other sensory information
area 22
- sensory speech area of ___ is localized in superior temporal gyrus
Wernicke
- Wernicke area is connected to the Broca area by a bundle of nerve fibers called the ___
- receives fibers from the visual cortex in the occipital lobe and the auditory cortex in the superior temporal gyrus
arcuate fasciculus
- permits understanding of written and spoken language and enables a person to read a sentence, understand it, and say it out loud
- represents the site on the cerebral cortex where somatic, visual, and auditory association areas all come together
- area of very great importance
wernickle area
- taste area
area 43
concerned with appreciation of the positions and movements of the head in space
vestibular area
- area of the cortex that is buried within the lateral sulcus and forms its floor
- important for planning or coordinating the articulatory movements necessary for speech
insula
Handedness, perception of language, and speech are functional areas of behavior that are controlled by the
dominant hemisphere
spatial perception, recognition of faces, and music are interpreted by
nondominant hemisphere
forms a complete covering of the cerebral hemisphere
cerebral cortex
found in the cortex and have axons that either terminates in the deeper cortical layers
pyramidal and fusiform cells
terminate on dendrites or axons of cells found within other layers of the cortex
Stellate, horizontal, and cells of Martinotti
From superficial to deep, the six cortical layers are
molecular
external granular
external pyramidal
internal granular
internal pyramidal
multiform layers.
divided into posterior and anterior regions
precentral area
occupying the precentral gyrus, is referred to as the primary motor area because activation of the cells in this region results in isolated movements of muscles on the contralateral side of the body
posterior region
the movement areas in the ___ are organized with the lower limb structures represented on the medial aspect of the gyrus and ascending to trunk, upper limb, and face, laterally on the gyrus
motor cortex
both associated with the middle frontal gyrus. The latter is associated with conjugate movements of the eyes
supplementary motor area and frontal eye field
responsible for speech production and is located in the inferior frontal gyrus; paralysis of this area results in speech paralysis
broca area
occupies the postcentral gyrus of the parietal lobe. Sensations for parts of the body are organized in a somatotopic map beginning with feet on the medial most aspect of the gyrus and the head on the most lateral aspect of the gyrus
primary somesthetic area
- found within the cortex of the calcarine sulcus
- receives afferent information from the lateral geniculate body, which received information from the retina
primary visual area
- includes the gyrus of Heschl and is situated in the inferior wall of the lateral sulcus
primary auditory area
- localized in the left dominate hemisphere, in the superior temporal gyrus
- permits the understanding of written and spoken language
area of Wernicke
From a functional point of view, the ___ is organized into vertical units of activity
cerebral cortex
responsible for skilled movements on the opposite side of the body
primary motor area
In most individuals, this area is important on the left or dominant hemisphere
motor speech area of Broca
The opposite half of the body is represented inverted
primary somesthetic area
The superior retinal quadrants pass to the inferior portion of the
visual cortex
situated in the inferior wall of the lateral sulcus
primary auditory area
concerned with the makeup of the individual’s personality
prefrontal area
More than 90% of the adult population is right- handed and, therefore, is ___ dominant
left-hemisphere
acquisition of new information
learning
process by which information is retrieved or stored
memory
reflects a process by which information is lost
forgetting
recalling an event a few seconds after it occurs
immediate memory
retention of an event for several minutes after it has occurred
short-term memory
form of short-term memory and requires recall of a sequence of events for a few minutes to complete a task
working memory
- events that are remembered weeks, months, or years after they have occurred
- involves a change in synaptic organization or an increase in the efficiency of the synapse
long-term memory
- represents the memory for such facts as an address, directions to get to a specific place, or a string of numbers, such as a telephone number or a personal bank card personal identification number
- individual is conscious of the information that is remembered
declarative memory
- individual may not be consciously aware of the procedures involved in carrying out a task
procedural memory
Difficulty in retrieving old memories
retrograde amnesia
Difficulty in generating new memories
anterograde amnesia
Contralateral Paralysis – including facial palsy
Early- Muscle Flaccidity
Late- spasticity
area 4
Muscle Spasticity
Area 6
Also contains parts of areas 8, 44, 45
Ipsilateral tonic deviation of the eyes
Area 8
Loss of initiative (reduced spontaneous movements) and judgment
Emotional changes: tendency to euphoria
Poor executive functions, planning, problem solving, disinhibition
(+) Abulia
Poor speech output
area 9,10,11,12
Expressive aphasia/ Non-fluent Aphasia
area 44 and 45
contralateral sensory disturbance
Inability to judge degrees of warmth
Inability to localize tactile stimuli accurately
Deficits in sense of touch, vibration, joint position, stimulus localization
Area 3, 1, 2
(+) Astereognosis
Cortical Sensory Deficits: Two point discrimination, agraphesthesia
area 5 and 6
Angular Gyrus Syndrome:
Anomia, aLexia, Constructional difficulties, Acalculia, Dysgraphia, Finger anomia, right left disorientation
GERSTMANNS SYNDROME
area 39
Apraxia
area 40
Loss of sense of taste
area 43
homonymous hemianopsia
area 17
upper and lower visual quadrantanopia
area 17 and 18
loss of ability to interpret patterns of sounds
areas 41 to 42
Processing of visual stimuli
area 17
to relate the visual information received by the primary visual area to past visual experiences
area 18 and 19
Processing of auditory stimuli
area 41 and 42
Language comprehension
area 22
Familiar face recognition
area 37
- area 44 & 45
- lesion: expressive aphasia
- common etiology: infarct of superior division of the left MCA
broca’s area
lesion: conduction aphasia
arcuate fasciculus
- area 22
- lesion: receptive aphasia
- common etiology: infarct of the inferior division of the left MCA
wernicke’s area
Language Logic
Planning and Rational Symbolic thought
Analytical thought
Detail oriented perception
Cautious
Wernickes area
Broca’s area
Recognition of words, letters and numbers
Right Field vision Right side motor skills
left hemisphere
Intuitive thought Emotional thought Random sequencing Creative writing/Art Imagination Impulse
understanding of connotations in verbal speeches, perception of voice intonation
Identification of other’s emotions and mood
Left Field vision
Left side motor skills
right hemisphere
The largest giant pyramidal cells are found in the
precentral gyrus
In the visual cortex, the ___ is so thick that it can be seen with the naked eye
outer band of Baillarger
most superficial layer of the cerebral cortex and is composed mainly of a dense network of tangentially oriented nerve fibers
molecular layer
known as the primary motor area
posterior region
store programs of motor activity, which are conveyed to the primary motor area for the execution of movements
premotor area
The area of cerebral cortex controlling a particular movement is ___ to the skill of the movement
proportional
brings about the formation of words by its connections with the primary motor area
broca speech area
connected to the sensory speech area of Wernicke
broca speech area
is in the inferior frontal gyrus between the anterior and ascending rami and the ascending and posterior rami of the lateral fissure
speech area of broca
represent the motor speech area
areas 44 & 45
occupies the post- central gyrus
primary somesthetic area
Histologically, the ___ contains large numbers of granular cells and few pyramidal cells.
primary somesthetic area
extends onto the posterior part of the paracentral lobule
primary somesthetic area
located in the walls of the posterior part of the calcarine sulcus
primary visual cortex
receives afferent fibers from the lateral geniculate body.
visual cortex
represented in the visual cortex of the left cerebral hemisphere
right half of the visual field
secondary visual area ___ surrounds the primary visual area on the medial and lateral surfaces of the hemisphere
areas 18 and 19
The main projection fibers to the primary auditory area arise from the ___
medial geniculate body
The sensory speech area of ___ is localized in the superior temporal gyrus in the dominant hemisphere
Wernicke
A ___ lesion of the auditory area produces partial deafness in both ears
unilateral
primary auditory area is sometimes referred to as Brodmann areas ___
41 and 42
form a large area of the cortical surface
association areas
concerned with the interpretations of sensory experiences
association areas
Appreciation of the body image is assembled in the ___
posterior parietal cortex
he right side of the body is represented in the ___
left hemisphere
The association areas have all six cellular layers and are referred to as ___
homotypical cortex
of the adult population is left-hemisphere dominant for speech
96%
interprets spatial perception, recognition of faces, and music
nondominant hemisphere
