Transcranial magnetic stimulation (TMS) can be used in two different ways to investigate the contributionof cortical areas involved in grasp/reach movements in humans. It can produce “virtual lesions” thatinterfere with activity in particular cortical areas at specific times during a task, or it can be used in a twincoil design to test the excitability of cortical projections to M1 at different times during a task. The formermethod has described how cortical structures such as the ventral premotor cortex (PMv), dorsal premotorcortex (PMd) and the anterior intraparietal sulcus (aIPS) are important for specific aspects of reaching,grasping and lifting objects. In the latter method, a conditioning stimulus (CS) is first used to activateputative pathways to the motor cortex from, for example, posterior parietal cortex (PPC) or PMd, whilea second, test stimulus (TS), delivered over the primary motor cortex a few ms later probes any changesin excitability that are produced by the input. Thus changes in the effectiveness of the conditioning pulsegive an indication of how the excitability of the connection changes over time and during a specifictask. Here we review studies describing the time course of operation of parallel intracortical circuits andcortico-cortical connections between the PMd, PMv, PPC and M1, thus demonstrating that functionalinterplay between these areas and the primary motor cortices is not fixed, but can change in a highlytask-, condition- and time-dependent manner
TMS investigations into the task-dependent functional interplay between human posterior parietal and motor cortex
Koch G
Primo
;
2009
Abstract
Transcranial magnetic stimulation (TMS) can be used in two different ways to investigate the contributionof cortical areas involved in grasp/reach movements in humans. It can produce “virtual lesions” thatinterfere with activity in particular cortical areas at specific times during a task, or it can be used in a twincoil design to test the excitability of cortical projections to M1 at different times during a task. The formermethod has described how cortical structures such as the ventral premotor cortex (PMv), dorsal premotorcortex (PMd) and the anterior intraparietal sulcus (aIPS) are important for specific aspects of reaching,grasping and lifting objects. In the latter method, a conditioning stimulus (CS) is first used to activateputative pathways to the motor cortex from, for example, posterior parietal cortex (PPC) or PMd, whilea second, test stimulus (TS), delivered over the primary motor cortex a few ms later probes any changesin excitability that are produced by the input. Thus changes in the effectiveness of the conditioning pulsegive an indication of how the excitability of the connection changes over time and during a specifictask. Here we review studies describing the time course of operation of parallel intracortical circuits andcortico-cortical connections between the PMd, PMv, PPC and M1, thus demonstrating that functionalinterplay between these areas and the primary motor cortices is not fixed, but can change in a highlytask-, condition- and time-dependent mannerI documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
