Neuroscience Week 6: Cerebral Cortex Flashcards
Describe the cellular organization of the cerebral cortex
- The majority of cortex in mammals has 6 layers (neocortex)
- Distinguished by various staining techniques
by
- specific cell types
- density of cell types
- Pattern of myelination
How do cortical regions cytoarchitectonically?
The cortical surface can be divided into varying regions based upon differing features of cytoarchitectonics alone
Each hemisphere contains ________________ representations of the body and its surroundings (motor and sensory)`
Contralateral
Explain cerebral hemisphere dominance
higher functions such as analytical thinking, language, emotion, spatial orientation and musical abilities are centered in one hemisphere more than the other
The hemisphere that contains the centers for language production and comprehension is called
The dominant hemispheres
Explain hemisphere dominance
Area 4
Primary motor area
Primary Motor Cortex function
- Disproportionate representation of the body
- Large regions: hand, digits, lips and tongue
- Fine movements of the hand and fingers and speech
Lesions of the Primary motor cortex
Weakness of the body part contralateral to the specific area damaged
Identify blood supply
Area 6
Premotor cortex
Premotor and Supplementary motor function
Programming or organizing of the postural adjustments necessary to perform a skilled movement
Premotor and Supplementary motor stimulation
Damage to the Supplementary motor cortex often results in
Motor apraxia
Motor Apraxia description
Inability to perform purposive movement even though no paralysis exists
Damage to the _________________ often results in motor apraxia
Supplementary motor cortex
How do you test for motor apraxia?
by asking the patient to do complex tasks, using commands such as “Pretend to comb your hair” or “Pretend to strike a match and blow it out” and so on. Patients with apraxia perform awkward movements that only minimally resemble those requested, despite having intact comprehension and an otherwise normal motor exam. This kind of apraxia is sometimes called ideomotor apraxia. In some patients, rather than affecting the distal extremities, apraxia can involve primarily the mouth and face, or movements of the whole body, such as walking or turning around.
Areas 44/45
Broca’s Area
Broca’s Area Function
Motor or expressive speech center: motor programs for the production of words and projections to muscles used in articulation
Lesions of Broca’s area lead to
expressive or motor aphasia
Lesions of _____________ lead to expressive or motor aphasia
Broca’s area
Expressive or motor aphasia description
characterized as nonfluent because of the slow, prolonged output of words, poor articulation and short sentences containing only the necessary verbs, nouns and pronouns
Lesions limited to Broca’s area aphasia will be
mild and transient
lesions to Broca’s area that also includes the adjacent frontal cortex and white matter tracts will be
Severe: result in mutism and frequently agraphia
Agraphia
Agraphia is an acquired neurological disorder causing a loss in the ability to communicate through writing, either due to some form of motor dysfunction or an inability to spell.
Areas 1, 2 and 3
Somatosensory cortex
Somatosensory cortex function
Somatotopic representation of sensory input (sensory homunculus)
Somatosensory cortex stimulation results in
sharply localized contralateral sensation
Somatosensory cortex lesion
loss of tactile discrimination and proprioception on the contralateral side
________________ shows an incredible amount of plascticity as shown by remapping after a crush injury or amputation
Somatosensory cortex
Somatosensory cortex neuroplastic?
Yes the sensory cortex shows an incredible amount of plasticity as shown by remapping after a crush injury or amputation
Theory of phantom limb sensation
Areas 5, 7, 39 and 40
Parietal Association area
Parietal Association Area function
orderly or sequential performance of tasks (especially hands)
Parietal Association Area stimulation results in?
sharply localized contralateral sensation
Lesions of the parietal association area in the dominant hemisphere lead to
Astereognosis (tactile agnosia)
tactile agnosia
Tactile agnosia is characterized by the lack of ability to recognize objects through touch. The weight and texture of an object may be perceived, but the person can neither describe it by name nor comprehend its significance or meaning. Tactile agnosia is caused by lesions in the brain’s parietal association area
Astereognosis AKA
Tactile agnosia
Astereognosis description
(or tactile agnosia if only one hand is affected) is the inability to identify an object by active touch of the hands without other sensory input, such as visual or sensory information.
Lesions to the parietal association area on the non-dominant hemisphere lead to
neglect syndrome
Neglect syndrome is caused by?
lesions to the parietal association area on the non-dominant hemisphere
Neglect syndrome description
Such individuals with right-sided brain damage often fail to be aware of objects to their left, demonstrating neglect of leftward items.
The deficit may be so profound that patients are unaware of large objects, even people, towards their neglected or contralesional side - the side of space opposite brain damage. They may eat from only one side of a plate, write on one side of a page, shave or make-up only the non-neglected or ipsilesional side of their face (same side as brain damage). Their drawings may fail to include items towards the neglected side, for example when placing the numbers in a drawing of a clock (Fig.1). Many patients are often also unaware they have a deficit (anosognosia).
Area 41
Primary auditory cortex
Area 42
Secondary auditory cortex
Primary and secondary auditory cortex function
Auditory processing
Stimulation to the primary and secondary auditory cortices results in
primary - leads to humming, buzzing, clicking or ringing
secondary - leads to a whistle or bell sound
Stimulation of this area leads to a whistle of bell sound
Secondary auditory cortex (area 42)
Stimulation of this area leads to humming, buzzing, clicking or ringing
primary auditory cortex (area 41)
Unilateral lesion to the primary and secondary auditory cortices lead to?
no hearing loss. since. auditory pathways are bilateral but do cause difficulty recognizing direction and distance on the contralateral side
Areas 21, 22 and 37
temporal lobe: visual association area
Visual association cortex function
Strongly connected to the limbic system and associated with memory
Visual association cortex stimulation results in?
Illusions of past events including visual, sounds and emotional content
stimulation to this area causes illusions of past events including visual, sounds and emotional content
visual association cortex
Left posterior emporal visual association cortex lesion
impaired learning or remembering verbal information
Right posterior temporal visual association cortex lesion
impair learning and memory of visually based information
Bilateral lesions of the temporal visual association cortex result in
prosopagnosia (the ability to recognize the faces of others)
Area 22
Wernicke’s Area
Wernicke’s Area Function
Comprehension and formulation of language
Lesions of Wernicke’s Area will lead to?
- Receptive or sensory aphasia
- it is characterized as a fluent aphasia because production is normal but use of words is impaired
- They are fluent, but cannot comprehend language in any form (spoken, heard, or read)
Lesions to this area cause Receptive or sensory aphasia
Wernicke’s Aphasia
Patients with damage to Wernicke’s area
- substitute one word for another
- insert meaningless words
- string together phrases of great length but no meaning
- Also leads to Agraphia
Broca’s Aphasia Repetition
Impaired
Broca’s Aphasia Fluency
non-fluent
Broca’s Aphasia comprehension
Intact
Broca’s Aphasia area?
Inferior frontal gyrus
Wernicke’s Aphasia Fluency
Fluent
Wernicke’s Aphasia Comprehension
Impaired
Wernicke’s Aphasia Area
Superior temporal gyrus
Conduction Aphasia Fluency
fluent
Conduction Aphasia comprehension
intact
Conduction Aphasia area
Arcuate fasiculus
Global Aphasia fluency
nonfluent
Global Aphasia Comprehension
Imparied
Global Aphasia area
all areas affected
Global Aphasia Repetition
impaired
Conduction Aphasia repetition
impaired
Wernicke’s Aphasia repetition
Impaired
Transcortical motor aphasia Repetition
Intact
Transcortical motor aphasia fluency
nonfluent
Transcortical motor aphasia comprehension
intact
Transcortical motor aphasia Area
Frontal lobe surrounding Broca (which is spared)
Transcortical sensory aphasia Repetition
Intact
Transcortical sensory aphasia Fluency
fluent
Transcortical sensory aphasia comprehension
impaired
Transcortical sensory aphasia Area
Temporal lobe around Wernicke (which is spared)
Transcortical mixed aphasia Repetition
Intact
Transcortical mixed aphasia fluency
Nonfluent
Transcortical mixed aphasia comprehension
impaired
Transcortical mixed aphasia area
Watershed areas surrounding Broca, Wernicke and Arcuate fasciculus (all spared)
Identify
Identify
Identify areas and associated aphasias
7 listed
Identify
Identify
Areas 17, 18 and 19
Occipital lobe: Visual association
Occipital lobe visual association area function
Visual processing (17)
perception of color, movement, direction of objects (18&19)
Lesion to the Occipital lobe visual association area results in
Association areas (peristriate and parastriate) lead to visual agnosia (inability to recognize objects and their colors)
Unilateral lesions of the Primary Visual Cortex lead to (V-I or 17)
contralateral homonymous hemianopsia (loss of half the field of view on the same side of both eyes
Describe cerebral pathways
Identify functional deficits and areas
Identify
Identify structure and lobe
Identify Lesion effects
Granular layer contains what cells
inhibitory cells
Molecular layer cells
sparse pop of cells
external granular layer cell type
stellate granular inhibitory cells
1st 3 layers are primarily
cortico-cortico connections
layer 4 is
chief input layer
layer 5 is
chief output layer (striatum, brainstem, spinal cord)
Layer 6 is
output to thalamus
