Cerebral cortex, behavior & dementia Flashcards
What is the general role of the cerebral cortex?
Analyzes, plans and initiates responses to sensory pathways
What adjusts the level of cortical responsiveness?
The reticular formation and diffuse modulatory system
Describe the morphology of pyramidal cells
Neurons with a long apical dendrite and a basal dendrite. Dendritic spines are formed/modified by learning.
What neurotransmitter is used by pyramidal cells? What about nonpyramidal cells?
Pyramidal: glutamate
Non-pyramidal: GABA
What are the nonpyramidal cells?
Inhibitory neurons with various morphologies, but do not leave the cortex
“Interneurons”
How many layers does the neocortex have?
Neocortex has 6 layers
Which cortical layers contain neurons that project out of the cortex?
Layers V and VI
What are the major connections between hemispheres?
Corpus callosum
Anterior commisure
What are association bundles?
AKA: fasciculi
Connections between regions of the brain on the same side. Not discrete point-to-point connections.
Where is the primary motor cortex?
Precentral gyrus (BA4)
Where is the primary somatosensory cortex?
Postcentral gyrus (BA312)
Where is the primary visual cortex?
Calcarine (BA17)
Where is the primary auditory cortex?
Transverse temporal gyrus (BA41)
What is the result of injury to unimodal association areas?
Agnosia: can see/describe an object but cannot name
What is the result of injury to multimodal association areas?
Apraxia (motor) or neglect (sensory)
What are the two major aphasic syndromes and how do they differ?
Broca (motor): poor verbal fluency with good comprehension
Wernicke (sensory): good verbal fluency with poor comprehension
Describe the location and connection between the broca and wernickes area
Wernicke’s (temporal lobe) is connected to Broca’s (frontal lobe) via the arcuate fasciculus
Which portion of the reticular formation is related to horizontal eye movements? vertical eye movements?
Horizontal: PPRF
Vertical: (riMLF)
What is the function of the serotonergic and adrenergic systems?
Sleep-arousal mechanisms
What neurotransmitter is associated with the Raphe nucleus?
Serotonin
What neurotransmitter is associated with the locus ceruleus?
Norepinephrine
What neurotransmitter is associated with the basal nucleus of Meynert?
Acetylcholine
What are the different types of memory?
Immediate
Recent: short term, recall after 5 minutes
Remote: long term, hours to years prior
What are the different types of amnesia?
Anterograde: inability to learn new material
Retrograde: inability to recall learned material
Location of lesions producing amnesia
Bilateral thalamus, mamillary bodies or hippocampus
What are the main causes of bilateral hippocampal lesions?
Herpes simplex encephalitis
Anoxia (following cardiac arrest, for example)
Early Alzheimer’s disease
What is apraxia?
Inability to conceptualize and perform a skilled, learned act on command
Prefrontal/frontal: gait apraxia
Parietal: constructional apraxia, dressing apraxia
What is agnosia?
Impaired recognition of perceived stimuli due to lesions in the sensory association cortex
Ex: Visual agnosia: cannot recognize object by sight, but readily identify with tactile or auditory clues
What are the frontal lobe release signs?
Reflexes normally found in infancy
Snout reflex: after stimulation of lips
Rooting reflex: mouth seeks stimulus at cheek or lips
Palmar grasp response: fingers latch onto palm stimulus
Plantar grasp: toes latch onto stimulus at sole
What is the effect of nondominant parietal lesions?
Impaired spatial relationships between the body and its surroundings
ex: anosognosia = denial of half the body
What is delirium?
Abrupt onset confusional state varying between agitation and obtundation
Assocaited with variable consciousness, motor activity, mood changes, hallucinations
What is dementia?
Diffuse impairment of acquired cortical function, progressing over months to years
Impedes daily activities
Treatable/Reversible causes of dementia
Chronic infection Hypothyroidism Thiamine or B12 deficiency Drug/alcohol abuse Chronic subdural hematomas Tumor/abscess Normal pressure hydrocephalus Depression
Incurable/irreversible causes of dementia
Vascular dementia Alzheimer's disease CJD Degenerative/hereditary AIDS
What is Alzheimer’s disease?
Progressive neurodegenerative disease that is the most common cause of dementia in elderly Americans
Initial problems with memory, intellect, aphagia, apraxia or agnosia
Later problems with judgment, personality changes, incontinence
Death 2-15 years from onset
Pathogenesis of Alzheimer’s disease?
Beta amyloid accumulation as extracellular senile plaques in the hippocampi
Intraneuronal neurofibrillary tangles containing tau protein
Grossly, increased sulci and ventricles with narrowed gyri due to widespread cortical atrophy
What disorder is associated with early Alzheimer’s disease?
Down’s syndrome (trisomy 21) because amyloid precursor protein is coded on chromosome 21
Treatment for Alzheimer’s disease
AChE inhibitors slow deterioration (donepezil)
Memantine (NMDA antagonist) is added later in course
