By varying the onset time of stimulation, we show that the representation of space in IPSp is updated immediately after the first-saccade. In the current study, we stimulated the human IPS of the right hemisphere with TMS and measured effects on spatial updating using a variant of the “double-step saccade” task ().
In contrast, stimulation of an adjacent IPS site had no such effects on second-saccades. This behavioral paradigm (23–25) has been used extensively to study spatial updating in monkeys and humans and requires subjects to perform a sequence of two saccades to sequentially flashed targets (23–25).
In another single-cell recording experiment, neurons in parietal reach region exhibited responses consistent with either of two target locations in a sequence of planned reaching movements, suggesting that different parts of a planned sequence of locations can be represented in parallel in parietal reach region.
The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals.
Human subjects had to remember the location of a target, briefly flashed left or right of central fixation.
Next, they refixated and then, after a further memory delay, made a saccade to the memorized target location.
Saccadic eye movements cause sudden and global shifts in the retinal image. This “spatial updating” mechanism ensures that spatial codes for perception and action are not compromised by eye movements.
In turn, much of the output of the posterior parietal cortex goes to areas of frontal motor cortex: the dorsolateral prefrontal cortex, various areas of the secondary motor cortex, and the frontal eye field.
The parietal lobe is positioned above the occipital lobe and behind the frontal lobe and central sulcus.