Apraxia Models and Praxis

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Questions and Answers

What is primarily involved in the conversion of mental images of intended actions into motor execution?

Subthalamic nucleus

Cerebellum

Left parietal hub (correct)

Right occipital cortex

Which region of the brain has shown activity in response to recognizing actions associated with object use?

Lateral geniculate nucleus

Anterior cingulate cortex

Inferior parietal lobule (correct)

Entorhinal cortex

What term describes the learned skilled movements that are essential for effective praxis?

Cognitive action maps

Visuokinesthetic motor engrams (correct)

Motor schemas

Praxis patterns

Which function does action semantics primarily serve in the context of tool use?

Specifies knowledge of tool actions and associations Signup and view all the answers

Which area of the brain is involved in the translation of movement formulas into motor programs?

Supplementary motor area (SMA) Signup and view all the answers

In addition to movement formulas, what other elements are considered crucial in models of praxis?

Motor programs and action semantics Signup and view all the answers

What is the role of the left parietal sub-regions in the context of motor control?

Providing privileged connectivity to sensory and motor areas Signup and view all the answers

Which of the following modalities can activate spatiotemporal movement formulas?

Visual, verbal-auditory, and tactile modalities Signup and view all the answers

What is the primary function of the SMA in the context of movement?

To translate parietal movement formulas into specific motor programs Signup and view all the answers

Which brain area is primarily associated with the sequencing of multiple arm and hand movements?

Prefrontal Cortex Signup and view all the answers

What pathway does the brain use to convey motor programs for ipsilateral movements?

Across the corpus callosum to the opposite premotor cortex Signup and view all the answers

Which area of the brain shows more activity during action imagery compared to the right hemisphere?

Left Inferior Parietal Lobule Signup and view all the answers

Which of the following brain regions is associated with proximal limb control representations?

Bilateral Inferior Frontal Gyri Signup and view all the answers

Which factors contribute to the occurrence of apraxia according to this model?

Damage in various regions including the prefrontal cortex and thalamus Signup and view all the answers

What role do both parietal regions play in upper-extremity movements?

Coordinating the integration of visual information with movement Signup and view all the answers

When are the right parietal regions more active compared to the left during gestural tasks?

While imitating gestures involving finger postures Signup and view all the answers

Study Notes

Models of Apraxia

Most models of praxis include a left parietal hub with connections to anterior motor areas.
This hub plays a central role in learning and converting mental images of intended action into motor execution.
Spatiotemporal movement formulas, also known as praxicons or visuokinesthetic motor engrams, are necessary for learned skilled movements.

Spatiotemporal Movement Formulas

These formulas can be activated by multiple input modalities, including visual, verbal-auditory, and tactile.
Cells in the inferior parietal lobule fire selectively in response to hand movements, visually presented information about object size and shape, or the actual manipulation of objects.
Functional neuroimaging studies show activity in this region in response to recognition of actions associated with object or tool use (transitive actions).

Left Parietal Region

This region appears to contain action semantics and conceptual systems such as tool action, tool–object association information, and general principles of tool use.
Action semantics specify knowledge of tool action (e.g. turning, pounding) and the knowledge of which tool or object to use for a task.

Motor Programs

The premotor region, specifically the supplementary motor area (SMA), translates movement formulas into motor programs.
The SMA receives projections from parietal neurons and projects axons to motor neurons in the primary motor cortex.
Motor programs are then sent to activate the motor neurons, resulting in movement of the contralateral extremity in the prescribed spatial trajectory and timing.

Additional Regions Involved in Praxis

Prefrontal cortex: participates in sequencing multiple arm, hand, and finger movements.
Right hemisphere: involved in apraxia, especially in distal limb control areas.
Basal ganglia (putamen and globus pallidus), thalamus, and their white-matter connections: also play a role in apraxia.

Bilateral Control and Imitation

Bilateral inferior frontal gyri are associated with proximal limb control representations for both limbs.
Distal limb control areas are generally left-lateralized for both limbs.
Both parietal regions participate in the integration of visual information and upper-extremity movement, and in performing nonpurposeful movements.

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Description

This quiz covers the historical perspective of apraxia models, including the left parietal hub and its connections to anterior motor areas. It also explores the role of learning and converting mental images into motor execution.