Topographic organization for delayed saccades in human posterior parietal cortex

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Human Brain Mapping

Background:

• The posterior parietal cortex (PPC) is implicated in crucial cognitive functions like decision-making, attention, and memory.
• Research in non-human primates has largely focused on the lateral intraparietal area (LIP) within the intraparietal sulcus (IPS).
• Establishing reliable methods to localize human PPC areas is vital for understanding its role in cognition.

Purpose of the Study:

• To identify and map topographically organized regions within the human PPC.
• To investigate potential human homologues of the primate lateral intraparietal area (LIP).
• To develop a routine method for localizing specific parietal areas in individual subjects.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to map the human PPC.
• A delayed saccade task with peripheral targets presented sequentially was employed.
• Retinotopic mapping was used to define visual areas, including V7, for reference.

Main Results:

• Two distinct, topographically organized areas were identified in each hemisphere of the human PPC.
• These areas contain topographic maps of the contralateral visual field.
• The newly identified areas are located rostral to V7 and are separated by visual field orientation reversals.

Conclusions:

• The human PPC contains at least two topographically organized regions that are candidates for the human homologue of LIP.
• These findings demonstrate a continuous tiling of topographic maps from V1 into the PPC.
• This study provides a foundation for further investigation into the functional roles of these human PPC areas.