Module 10 Flashcards
What are the three principles of sensorimotor control mentioned in the text?
(1) The sensorimotor system is hierarchically organized. (2) Motor output is guided by sensory input. (3) Learning can change the nature and the locus of sensorimotor control.
How is the operation of the sensorimotor system compared to that of a large, efficient company?
Both are directed by commands that cascade down through hierarchical levels, with higher levels specifying general goals rather than specific plans of action.
What are the advantages of hierarchical organization in both the sensorimotor system and a large company?
Higher levels are left free to perform more complex functions, while lower levels execute more detailed tasks.
What characterizes the structure of both the sensorimotor system and a large company hierarchy?
They are parallel hierarchical systems, allowing control over lower levels through multiple paths.
What role does functional segregation play in the sensorimotor system and a large company hierarchy?
Each level is composed of different units (neural structures or departments), each performing a different function.
What is the main difference between sensory systems and the sensorimotor system in terms of information flow?
In sensory systems, information mainly flows up through the hierarchy, while in the sensorimotor system, information mainly flows down.
What role does sensory feedback play in directing responses in the sensorimotor system?
Sensory feedback plays an important role in directing responses, with most responses influenced by the sensory feedback they generate.
What are ballistic movements, and how are they influenced by sensory feedback?
Ballistic movements are brief, all-or-none, high-speed movements. They are not normally influenced by sensory feedback.
How are adjustments in motor output controlled during sensorimotor learning?
Many adjustments are controlled unconsciously by lower levels of the sensorimotor hierarchy without the involvement of higher levels.
What characterizes sensorimotor learning in terms of motor responses and conscious control?
During initial stages, individual responses are performed under conscious control; with practice, responses become organized into continuous sequences of action adjusted by sensory feedback without conscious regulation.
What are the two major areas of sensorimotor association cortex mentioned in the text?
The posterior parietal association cortex and the dorsolateral prefrontal association cortex.
What role does the posterior parietal association cortex play in sensorimotor control?
It integrates information about body position and external objects, directs behavior by providing spatial information, and directs attention.
What sensory systems does the posterior parietal cortex receive input from?
The visual system, the auditory system, and the somatosensory system.
Where does much of the output of the posterior parietal cortex go to?
It goes to areas of motor cortex located in the frontal cortex, including the dorsolateral prefrontal association cortex and various areas of secondary motor cortex.
What consequences can damage to the posterior parietal cortex produce?
Deficits in perception and memory of spatial relationships, accurate reaching and grasping, control of eye movement, attention, apraxia, and contralateral neglect.
Define apraxia.
Apraxia is a disorder of voluntary movement not attributable to paralysis or weakness, where patients have difficulty making specific movements, particularly out of context.
What is contralateral neglect?
Contralateral neglect is a disturbance of a patient’s ability to respond to stimuli on the side of the body opposite to the brain lesion, without simple sensory or motor deficits.
What is egocentric left?
Egocentric left is the deficit in responding to stimuli to the left of the patient’s own body, often observed in patients with contralateral neglect.
What is object-based contralateral neglect?
Object-based contralateral neglect is the failure to respond to the left side of objects, regardless of their position in the visual field.
How does unconscious perception manifest in patients with contralateral neglect?
Patients may exhibit unconscious perception by showing a tendency to look more in the direction of stimuli presented to their neglected side, or by demonstrating improved identification of fragmented drawings after exposure to complete versions they were not consciously aware of.
What are the two major areas of association cortex with important sensorimotor functions mentioned in the text?
The posterior parietal association cortex and the dorsolateral prefrontal association cortex.
What areas receive projections from the dorsolateral prefrontal association cortex?
Areas of secondary motor cortex, primary motor cortex, and the frontal eye field.
What types of activity do dorsolateral prefrontal neurons exhibit?
Some neurons show activity related to object characteristics or locations, while others show activity related to responses, firing before and during movement initiation.
What is the function of areas of secondary motor cortex?
They are involved in programming specific patterns of movements after receiving instructions from the dorsolateral prefrontal cortex.
What are mirror neurons?
Mirror neurons are neurons that fire both when an individual performs a specific action and when they observe the same action performed by another.
What is the significance of mirror neurons in social cognition?
They provide a possible mechanism for social understanding, cooperation, and imitation by mapping others’ actions onto one’s own action repertoire.
How do mirror neurons respond to the understanding of an action’s purpose?
They respond to the purpose of an action rather than superficial characteristics, firing even when the action is perceived indirectly or mentally represented.
Where have mirror neurons been found in macaque monkeys?
Mirror neurons have been found in several areas of the frontal and parietal cortex in macaque monkeys.
What is the main method used to study mirror neuron mechanisms in humans?
Functional MRI studies are the main method used to study mirror neuron mechanisms in humans.
What similarity exists between mirror mechanisms identified in humans and macaques?
The mirror mechanisms identified by functional MRI in humans tend to be in the same cortical areas as those identified by single-cell recording in macaques.
Where is the primary motor cortex located?
In the precentral gyrus of the frontal lobe.
What is the organization of the primary motor cortex known as?
Somatotopic organization, commonly referred to as the motor homunculus.
What is stereognosis?
Stereognosis is the process of identifying objects by touch.
What is the function of each primary motor cortex neuron traditionally thought to be?
Traditionally, each neuron was thought to encode the direction of movement.
What stimulation technique has been used to map the primary motor cortex in recent studies?
Longer bursts of current, which produce complex natural-looking response sequences.
What is the alternative to the idea that motor neurons are tuned to particular angles of movement?
The firing of many primary motor cortex neurons is related to the particular endpoint of a movement, not to the direction of the movement.
What does the firing of primary motor cortex neurons in freely moving monkeys suggest?
It suggests that many neurons are sensitive to the target location of movement, not just the direction.
What is the implication of primary motor cortex stimulation causing opposite movements depending on the starting position?
It implies that signals from every site in the primary motor cortex diverge greatly, allowing each site to get a body part to a target location regardless of the starting position.
What is a brain-computer interface (BCI)?
A brain-computer interface allows direct communication between a computer and the brain, usually via an array of electrodes placed in the brain.
What are some applications of brain-computer interfaces mentioned in the text?
Applications include controlling robotic arms and mitigating the effects of spinal cord damage.
What are the effects of extensive damage to the primary motor cortex?
It may disrupt fine motor control of specific body parts, produce deficits in stereognosis, and reduce the speed, accuracy, and force of movements. However, it does not eliminate voluntary movement completely.
What are the cerebellum and basal ganglia primarily responsible for?
They interact with different levels of the sensorimotor hierarchy and coordinate and modulate its activities.
What percentage of the brain’s neurons does the cerebellum contain?
More than half.
What types of information does the cerebellum receive?
Information from primary and secondary motor cortex, descending motor signals from brainstem motor nuclei, and feedback from motor responses via the somatosensory and vestibular systems.
What role is the cerebellum believed to play in motor learning?
It is believed to play a major role in motor learning, particularly in the learning of sequences of movements in which timing is a critical factor.
What are some effects of diffuse cerebellar damage on motor function?
Loss of accurate control of movement direction, force, velocity, and amplitude; difficulty adapting motor output to changing conditions; tremors; disturbances in balance, gait, speech, and eye movement.
What are some functions of the cerebellum beyond sensorimotor control?
Patients with cerebellar damage often display diverse sensory, cognitive, emotional, and memory deficits.
How do the cerebellum and basal ganglia differ structurally?
The cerebellum is organized systematically in lobes, columns, and layers, while the basal ganglia are a complex heterogeneous collection of interconnected nuclei.
What is the current understanding of the basal ganglia’s function?
In addition to their role in motor modulation, the basal ganglia are involved in cognitive functions, motivation, habit learning, and classical conditioning.
What is the theory regarding the basal ganglia’s role in movement vigor?
The basal ganglia are responsible for controlling the speed and amplitude of movement based on motivational factors.
