PSY 3301 Lecture Notes - Lecture 20: Inferior Parietal Lobule, Primary Motor Cortex, Supplementary Motor Area

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Conscious Motor Intention Emerges in the Inferior Parietal Lobule
Abstract:
Willed actions are characterized by the subjective experience of ‘conscious intention’
Previous findings have suggested that conscious intention emerges in the mesial
precentral area (MPA) including the supplementary and pre-supplementary motor area.
o However, this assumption was later challenged by evidence indicating a key
contribution of the inferior parietal lobule (IPL) in this process. In this review, we
show that this second hypothesis is the most plausible.
IPL, rather than MPA, mediates the early subjective experience of ‘wanting to move’.
MPA generates a feeling of ‘motor urge’, near movement onset, when the inhibitory
control exerted on the low-level motor areas is released.
goal directed actions trigger two forms of motor intention:
o the first, ‘wanting to move’ intention is under the control of the inferior parietal
regions and specifies a general goal to be reached before movement planning; the
second, the ‘urge to move’ intention, is controlled by mesial precentral areas and
signals the time when the planned movement is about to start. The time locked
activation of these two forms of intention is at the basis of movement control.
Introduction
our voluntary actions are accompanied by the subjective experience of intentionality, the
feeling that we “act as we choose” or want.
Evidence suggested that conscious intention emerged in the mesial precentral area (MPA)
including the supplementary (SMA) and pre-supplementary motor area (pre-SMA)
New research advocated for the contribution of the inferior parietal lobule (IPL)
Although the evidence isn’t clear, current research favors IPL, not MPA, mediating the
emergence of movement conscious intention
o MPA does not generate intentional feelings per se, but affects consciousness
through a “go signal” emitted at movement onset, when the inhibitory action
exerted on the primary motor regions is released.
Urge to Move Vs. wanting to move
Since Penfield, electrical stimulation of the brain has proved to be a good tool for
investigating cognitive and sensorimotor functions in human patients
Using this tool, conscious motor intentions were rep in the IPL and the MPA
MPA
o Stimulating this region, patients report a compulsive desire to act, such as
“needing to do something” or “an urge to move”
o Not only a general urge…but a general urge to move specific places, like the
thumb
o Increasing the stimulation above threshold for urge made the movements occur
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Document Summary

Conscious motor intention emerges in the inferior parietal lobule. In this review, we show that this second hypothesis is the most plausible. The time locked activation of these two forms of intention is at the basis of movement control. Needing to do something or an urge to move : not only a general urge but a general urge to move specific places, like the thumb, increasing the stimulation above threshold for urge made the movements occur. 3: specificity of motor intentions show activation in mpa but are not find in the mpa, but the antecedents of mpa, such as the precuneus or posterior cingulate cortex. Ipl or just ipl: patterned/repetitive movements, but not goal directed, explanation: low level motor structures were disconnected from the intentional control of ipl, in an mri, only activation in the primary motor cortex. Ipl contributes to inhibit spontaneous neural activity within m1. Ipl and mpa lesions can cause alien hand syndrome: 1.

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