Exam 4 Part V Flashcards
cerebellum and excitatory inputs
2 excitatory inputs: They 1st cause excitation of deep Cbl nuclei by collaterals. Then cause excitation of Purkinje cells and inhibition on deep nuclei.
Planning function and the cerebellum
. In an area of the cerebellum, one can record activity of the next action to be performed, at the same time as the current action is going on. This area of the cerebellum is concerned with what will be happening next in a series of movements. Normally one has the ability to progress smoothly from one motion to the next. This ability is impaired in cerebellar damage, particularly in fast movements.
Timing functions
With cerebellar damage, complex movements such as running, talking and writing are disrupted and uncoordinated.
In general, Cbl important for using
In general, Cbl important for using spatiotemporal relationships in sensory info., for learned, unconscious, complicated movements
Cerebellar lesions cause
Cerebellar lesions cause abnormal movements ipsilateral to the lesion.
Removal of much of the cerebellar cortex doesn’t cause much detectable, lasting deficit. Must have removal of the
Must have removal of the deep nuclei additionally in order to see serious and permanent damage.
Dysmetria –
Dysmetria – can’t predict how far movement will go and so overshoot to mark. past–pointing, because normally dependent on that inhibitory damping.
Ataxia-
Ataxia- incoordination, e.g., wide gait
failure of progression
If one doesn’t know how long it takes for each movement & where the parts will be at a given time, one can lose parts of the body particularly during rapid motions
dysdiadochokinesia.
– jumbled – difficulty performing rapid alternating movements: dysdiadochokinesia.
Intention tremor –
Intention tremor – jerky during voluntary movement, failure to damp, e.g., Cbl nystagmus (attempts to fixate to the side)
Hypotonia –
loss of facilitation from tonic discharge of deep nuclei to increase muscles tone
Primary sensory areas: This map is determined by
electrical stimulation in awake epileptics who are having brain surgery to decrease the tendency for convulsions to spread.
l° somatosensory – parietal: .
l° somatosensory – parietal: uncomplicated sensations: tingling, numbness, mild electric feeling; localized; also some motor responses.
1° visual cortex – occipital:
1° visual cortex – occipital: flashes of light, bright lines, colors or other simple sights – localized to area of visual field
1° auditory – temporal:
1° auditory – temporal: simple sound (nothing complicated) as weak or loud high or low frequency, some other simple characteristics. Like squeak or undulation never speech. (Can one localize in space sound from l cortical cell? Yes! )
In general, without the primary sensory areas in the cortex,
the person’s ability to analyze sensory signals is greatly impaired. The primary sensory cortex is the first place in the cortex where sensory signals go.
Sensory association areas,
The general function of sensory association areas or secondary sensory areas is to provide a higher level of interpretation of sensory experiences. Damage results in an inability to do further analysis.
Damage in temporal lobe below and behind primary auditory area in dominant hemisphere. (L for most people hemisphere for language) –
loses ability to understand spoken words & other auditory experiences.
Destruction of visual association areas on the occipital lobe in the dominant hemisphere
. e.g. word blindness = inability to recognize meaning of written words one form of dyslexia.
Somatosensory association area in the parietal lobe: damage results in the person losing
Somatosensory association area in the parietal lobe: damage results in the person losing perception of the location of the parts of his/her body. The person may exhibit sensory neglect. Important part of body if it gets lost is the hand, e.g., hand skills impaired because of lack of sensory component)
All these sensory association areas meet one another in an area called
All these sensory association areas meet one another in an area called Wernicke’s area. It is particularly highly developed in the dominant side of the brain.
Wernicke’s is also called
It is also called general interpretation area, Gnostic area or 3rd degree association area.
Damage to Wernicke’s area:
The person might hear perfectly well & recognize words but might not be able to organize words into a coherent thought.
Can even read words on a page but may not recognize the thought that is conveyed =
sensory aphasia (Damage to Broca’s = motor aphasia).
In most people, one hemisphere is
physically larger than the other at birth. Speech & motor control areas tend to be much more highly developed on one side than another.
Often L
Often L
- -sequential-analytical –details
- -“makes all pieces fit into current world-view”
- -language, list-making etc.
Often R
Often R
–visual-spatial, includes face recogn. –global pattern
–“hypothesis testing & paradigm
shift”
–music, emotion etc.
What might the “other” (right) hemisphere be doing?
- -recognition of faces (representational)
- -emotional processing? If a certain area is destroyed, the person’s emotional tone may be all wrong
music
more controlled on the right, some separation between control for music & for speech and & motor patterns: Actress who had a stroke (Patricia Neal) had no speech but could sing words in a song.
–dyslexics more often
–dyslexics more often R-brain default
In front of the motor areas, the areas that are removed in “frontal lobotomy.”
In front of the motor areas, the areas that are removed in “frontal lobotomy.” In general the person can still perform IQ tests with prefrontal lobotomy (relatively preserved).
Prefrontal areas:
Prefrontal areas: “Elaboration of thought,” increase in depth & abstraction of thought. Rehearsing allows one to remember & plan.
B. Memory: One important area is the
B. Memory: One important area is the hippocampus, a medial part of the temporal lobe
bilateral lesions of the hippocampus or of some other parts of the temporal lobe, the person may be unable to
ilateral lesions of the hippocampus or of some other parts of the temporal lobe, the person may be unable to put new information from short– to long–term memory.
Stimulation of the temporal lobe including the hippocampus:
Stimulation of the temporal lobe including the hippocampus: one sometimes gets complicated sequential memories.
Stress can kill off cells needed for conversion to
Stress can kill off cells needed for conversion to long-term memory. Stress increases cortisol. These hippocampal cells have the highest concentration of cortisol receptors. These cells are particularly prevented from using glucose and they starve.
The presence of an RAS is inferred from the fact that
The presence of an RAS is inferred from the fact that diffuse electrical stimulation in the midbrain and pons RF causes immediate activation of the cerebral cortex. The animal goes instantly from being asleep to being awake.
Function of midbrain RAS:
Preventing the connection from the upper midbrain to the cerebrum causes the cerebrum to become inactive = coma.
Cutting the brainstem at the mid-pons → upwards, thus preventing upward connections from the pons, causes the cerebrum to become active. It remains active indefinitely as if continuously awake. An area below the mid-pons can inhibit the midbrain RAS.
Therefore, midbrain and upper pons
Therefore, midbrain and upper pons RF: activation. Brainstem below the midlevel pons: can inhibit the activating system and cause sleep.
Stimuli from the cerebrum down:
Stimuli from the cerebrum down: mainly into the mesencephalic RF from all over in the cerebrum, but particularly from the motor cortex: Importance of moving around to keep awake.
