Cortex 3 Flashcards
what does M1 correspond to?
the primary motor area
Brodmann’s area 4
how does M1 influence the motor system?
directly through the corticospinal and corticobulbar tracts
indirectly through their projections to the red nucleus and the RF
how is M1 organized?
somatotopically arranged
organized into radially arranged columns of neurons extending vertically from the surface into the depths of the cortex
a single column is a functional unit responsible for directing small groups of muscles acting on a single joint
- encodes the amount of force (frequency)
- trajectories are encoded by populations of neurons
describe the motor homunculus:
similar to sensory homunculus
large area for hand and face
eyes are gone though- doesn’t control movement of eye but controls eyelids (eyelids are done by frontal eye field (area 8)
DOUBLE REPRESENTATION-
what is double representation?
- muscle groups are represented twice.
posterior- M1-4p- can be activated by attention w/out any sensory feedback and has been suggested to be important for initiation of movements – works with BG
anterior- M1-4a- dependent on sensory feedback
- complex sensory motor interactions
- also is activated by imaginary finger movements and listening to speech while making no actual movements
- important in executing movements involving complex sensorimotor interactions
what are results of a lesion to M1?
UMNL contralateral symptoms
- immediate contralateral paresis, hypotonia, hyporeflexia
- weeks–> spasticity, hyperreflexia, Babinskis sign
- MAINLY weakness
what are trajectories?
?
summation determines trajectory
what does the motor association cortex consist of?
Brodmann’s area 6 and parts of 8 and 44
includes the supplementary motor area (M2), the premotor area, the frontal eye fields and the posterior part of Broca’s area
what is the premotor area?
what Brodmann’s area?
what are its 2 divisions?
afferents? efferents?
function?
Brodmann’s area 6
divided into PMA lateral dorsal & lateral ventral
poorly understood
afferents primarily from posterior parietal cortex
efferents to BS (medial descending system- reticulospinal)
thought to control proximal muscles that project a movement to the target
areas change over time as response becomes more automatic
movements are triggered by external sensory events (how sensory stim will be used to direct movements )
what does the posterior parietal lobe play a role in?
providing visual info for targeted movements (5,7,39)
because of the cephalic flexure, what terms are now changed at this level?
dorsal= up ventral = down
what does the lateral dorsal premotor area do?
movement selection
- integration of sensory info into motor commands
- specific of movement parameters- amplitude, speed and direction
involved more with REACHING (afferents from parietal cortex; spatial relations and orientation; visual guided motion; sends strategy to BG)
involved with learning to associate a sensory event with a specific movement= ASSOCIATIVE LEARNING
what are results of a lesion to the lateral dorsal premotor area? (PMd)
have difficulty with associative learning
awkward movement
pick the wrong strategy
what does the lateral ventral premotor area do? (PMv)
densely interconnected with the hand area of M1 and the parietal lobe
related to grasping - conforming the hand to the shape of objects
also involved in the cognitive aspects of motor control
Mirror neurons:
- is active when an action is observed
- encode higher order, abstract representations for goal oriented actions
- form of motor learning?
what is the general result of a lesion to the premotor area?
impairs the ability to develop an appropriate strategy for movement
what is the supplementary motor area (M2) ?
what is it involved in? function?
SMA is involved in planning complex movements and in coordinating movements involving both hands
thought to function in the advanced planning of self initiated movements-especially bilateral ones
involved in learned sequences from memory in the absence of visual cues
more concerned with programming than executing
important in programming and coordinating complex sequences of movement
also play a role in coordinating posture and voluntary movement
NOT sensory drive; no visual/auditory/tactile guidance
what are results of a lesion to M2?
- can’t orient hands and digits appropriately while reaching for something (hands assume awkward positions as it approaches object)
- subjects are severely impaired in their ability to use both hands to retrieve a morsel of food stuck in a hole
- subject’s have a difficult time making postural adjustments that are needed during a movement
what do frontal eye fields control?
what do they work with?
initiation of saccades
works with:
- supplementary eye fields
- parietal eye fields
- superior colliculus
stimulation of this area results in conjugate deviation of the eyes to the opposite side
contributes to all volitional and visually guided saccades as well as to pursuit and mergence movements of the eye
what is the prefrontal lobe responsible for?
formulating plans and strategies, alone with a person’s personality
what is the prefrontal cortex?
what is its function?
this brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior
the basic activity of this brain region is considered to be orchestration of thoughts and actions in accordance with internal goals
EXECUTIVE FUNCTION
- planning ahead- predicting future
- monitoring- evaluating a situation
- sustained attention- keeping eyes on target
- gorl directed behavior
- working memory- short term memory & rehearsal
- problem solving
what are the 3 areas of the pre frontal cortex?
what are the 2 divisions?
dorsal
ventral
orbital/frontal (sits on frontal bone)
Lateral dorsal and lateral ventral
what does the lateral dorsal prefrontal cortex do?
PFLD- 8,9,46
characterizes the spatial relationships b/w stimuli and ascertains which responses should be executed (“how/where” pathway)
-transforming perception into action
responsible for the monitoring of info in (spatial) working memory
-working memory is defined as “the info that is currently available in memory for working on a problem
does this by evaluating the situation from a sensory analysis, then develops a plan to deal with the problem
(ex: only answer your phone when appropriate)
also involved in planning ahead
what does the lateral ventral prefrontal cortex (PFLV) do?
ASSOCIATIVE LEARNING & DECISION MAKING
- necessary for normal learning of arbitrary visuomotor associations (no spatial or delay component)
- characterizes the features and attributes of stimuli in the environment- “what pathway”
- guiding the selection and retrieval of semantic/linguistic knowledge
- inhibition- resolve negative feelings; enables to direct attention to helpful solutions rather than ruminate over problems
Left side:
- control attention
- (maintain focus in distracting environments)
Right side:
-vigilance
*dopamine- activated
what is the orbitofrontal cortex (OFC)?
makes up an important part of who we are by regulating our emotions
inputs consist of internal environmental info
- subjective judgements we use in defining responses to stimuli: fear, hunger, thirst, sexual urge, love, envy, jealousy, ethics, morals
- the drive or value generated by limbic system
Output
-OFC-planning process that occurs- regulates one’s behavior and physiological response, by using the consequence of one’s action
THUS,
- the OFC takes care of many important functions by combining sensory observations and the reward system
- encodes the reward value (value of outcomes) as they are attained
afferent input for the OFC?
- from the dorsomedial thalamus and the temporal cortex (both linked to memory)
- the ventral tegmental area (associated with reward system)
- the olfactory system
- the amygdala
efferent output from the OFC?
sends signals to the limbic system (responsible for moods and emotions
- the cingulate cortex
- hippocampal formation
- temporal cortex
- lateral hpothalamus
- amygdala; along with other areas of the frontal lobe
what are results of a lesion to the OFC?
many behavioral abnormalities would arise:
- inappropriate behavior and emotional changes are imminent
- pateitns will become more impulsive
- they typically show greater unprovoked emotions of anger and less unwarranted happiness
- sense of time is impaired
- lack of initiative, unconcern or underestimation of the gravity of a situation are all side effects that hinder patients’ relationships and every day lives
- frontal lobe damage can cause patients to be unable to plan or correct certain behaviors, though they can verbally express the right course of action
face and voice recognition problems
what activates the OFC?
smells activate neurons in the OFC
-reward value of smell
ease activates neurons in another part of OFC
- ex: once full, the OFC neurons no longer respond
- whereas, the neurons in the primary taste cortex are regulated by the identity of taste, not the reward value
The inferior temporal cortex also sends visual inputs directly to OFC
individuals react differently to itms or images depending on their reward association
-ex: OFC repsonds to face expression by signifying behavior should change
somatosensory inputs (touch, pain, etc) are sent from the post central gyrus; the amygdala transmits signals to the OFC. the more please and pain there is, the more OFC activity occurs
patients with damage to the ventral part of the frontal lobe may feel pain, but report that it does not feel very bad
what is the cingulate gyrus? what does it do?
involved with emotion formation and processing, learning and memory
highly influential in linking behavioral outcomes to motivation (a certain action induced a positive emotional response, which results in learning)
coordinates sensory input with emotions
emotional responses to pian
regulates aggressive behavior
implicated in schizophrenia
