Lecture 6- Cortex Flashcards
Purkinje cell sends output where
Cerebellar nuclei (including dentate nucleus)
Purkinje cell gets 2 inputs from where
Parallel fibers
– provide ongoing info about what the motor plan is (copy from cortex)
Mossy fibers
– Mossy fibers from spinal cord say that motor plan/sensory info is not what’s expected
What happens when climbing and parallel fibers fire at the same time
Parallel fiber gets kicked off –> purkinje cell fires –> deep nuclei are inhibited –> motor behavior is stopped
Where are climbing fires from
Inferior olive
Parallel fibers are what to the mossy fibers
Parallel fibers are axons of granule cells
Indirect vs direct circuits
Direct path GO – inhibit internal globus palladus (inhibitor) so thalamus can talk to cortex (inhibit the inhibitor to go)
Indirect path STOP – external globus palladus inhibits the internal globus palladus which then inhibits the thalamus so it will NOT talk to cortex
Motor cortex controls the muscles via what
Corticalspinal tract
Parkinson’s Disease pathway
No substantia nigra –> no dopamine input –> more STOP less go –> even more inhibition on thalamus and thalamus cannot talk to cortex –> less motor output (cannot initiate motor movements easily and motor activity that the person would not like to have…not enough control over indirect pathway and not enough activation of direct pathway)
How can Parkinson’s Disease be treated
By increasing dopamine with drugs or by electrically stimulating the basal ganglia
Symptoms of Parkinson’s Disease
Akinesia = lack of movement and difficulty initiating movement Resting tremor
Muscle rigidity
Huntington’s Disease Pathway
Protein causes cell death starting in striatum –> not enough input into indirect pathway (STOP) –> too much direct pathway activation –> not enough thalamus regulation –> too much motor output
Early signs of Huntington’s
Loss of cognitive and emotional control
Late signs of Huntington’s
Chorea (jerky, involuntary, brief movements)
White and gray matter in cortex
White inside
Gray outside
Neocortex has how many layers
6
Outputs from layer 2
Go to ipsilateral cortex
Outputs from layer 3
Go to contralateral cortex
Ipsilateral
Same side
Contralateral
Opposite side
Outputs from layer 5
Go to brainstem/spinal cord
Outputs from later 6
Go to thalamus
Inputs to layer 2-5
From cortex
Inputs to layer 4
From thalamus
Inputs to layer 2-6
From brainstem
Primary sensory cortex should have a big amount of what layer
Layer 4 (big input part of the brain so you need a big input layer)
Primary motor cortex should have a big amount of what layer
Layer 5 (big output where corticospinal tract starts)
Association cortex should have big amounts of what layers
2 and 3 (they just associate with other parts of cortex)
4 lobes of brain
Frontal
Parietal
Occipital
Temporal
(Free pizza on tuesdays)
Gyri
Hill
Sulci
Valley
Anterior to central sulcus (precentral gyrus)
Primary motor cortex
Posterior to central sulcus (postcentral gyrus)
Primary sensory cortex
3 divisions of frontal lobe
Superior frontal gyrus
Middle frontal gyrus
Inferior frontal gyrus
3 divisions of temporal lobe
Superior temporal gyrus
Middle temporal gyrus
Inferior temporal gyrus
2 divisions of parietal lobe
Superior parietal lobe
Inferior parietal lobe
Sylvian fissure
Break between frontal and temporal lobe
Output of corticospinal tract starts where
Primary motor cortex
Primary sensory cortex is where what occurs
Sensory info stops first (destination of dorsal columns)
Connectivity based parcellation
Cell structure is difficult to assess in humans
Cortex can be divided based on connectivity with other areas
Same color = active in the same task
Occipital lobe areas process what (purple)
Visual information
Inferior temporal lobe areas do what (purple)
Determine what an object is
Somatomotor network (blue)
Primary motor and primary sensory cortex work together
Dorsal attention network (green)
Areas determine whether an object is moving, where it is in space, and guide eye movements to the object
Ventral attention/salience network (light purple)
Areas important for monitoring the enviornment broadly and detecting unexpected stimuli, and for shifting attention
Limbic network (yellow)
Orbitofrontal cortex regulates emotion
Entorhinal cortex regulates memory
Control network (orange)
Areas important for complex cognition: making decisions, solving problems, holding information in mind, representing numbers
Default mode network (pink)
Areas are task negative (they are suppressed while doing anything)
How we are most of the time
Responsible for internally directed thought: thinking about things not in the current environment, the past, the future, the minds of other people
Where do association fibers communicate
Within a hemisphere
Short range association fibers
U-fibers
Long range association fibers (3) – superior longitudinal fasciculus
Connects all lobes
Long range association fibers (3) – arcuate fasciculus
Connects language areas
Long range association fibers (3) – uncinate
Connects limbic areas in temporal lobe to limbic areas in frontal lobe
Where do commissural fibers communicate
Between hemispheres
Example of commissural fiber
Corpus callosum
Anterior commissure
Olfaction
Posterior commissure
Pupillary light reflex
Where do projection fibers communicate
With brainstem and body (includes ascending, sensory fibers)
Why a decrease in gray matter volume over lifetime
Rapid growth in first 5 years of life then decrease as connections we don’t use are pruned away
Why a decrease in white matter volume over lifetime
Rapid growth throughout life until you start aging effects and brain loss
Connection between brain loss and growth in ventricles
As you see more brain loss you see more growth in ventricles
Where is gray matter loss faster
In the back of the brain
Idea behind development of cognitive vs sensory areas
Sensory areas (back of brain) develop first and cognitive areas develop last
Cortical thinning is a marker of what
Maturation
What drives white matter expansion and increased coherence
Myelination
Sensory areas thin ____ and association areas thin _____
Sensory first, association last
White matter consists of what fibers
Association fibers, commisural fibers, and projection fibers
