Low frequency oscillations in rat posterior parietal cortex are differentially activated by cues and distractors

Abstract

The posterior parietal cortex (PPC) is hypothesized to detect visual cues among competing distractors. Anatomical and neurophysiologic evidence indicates that the rat PPC is part of a network of brain areas involved in directed attention, specifically when new task parameters or conditions are introduced. Here, we test the hypothesis that changes in the local field potential (LFP) of the PPC of rats performing a sustained attention task reflect aspects of detection. Two event-related potentials were observed during detection: the P300 response and the contingent negative variation (CNV). Spectrogram analysis also indicated a detection-specific increase in alpha power in the retention interval of this task. This is consistent with observations from human studies, which indicate that tasks requiring a subject to withhold a response produced a pronounced synchronization of alpha rhythms during the delay, and desynchronization during retrieval. We also found cycles of alpha synchrony and desynchrony in response to a periodic distractor. These cycles were most pronounced in the initial trial block of the distractor when the false alarm rate was highest, and as task performance improved these cycles significantly diminished. This result suggests that alpha cycling in the PPC represent neural activity critical for learning to inhibit distractors. The occurrence of alpha synchronization and desynchronization to attention-demanding stimuli, in addition to the P300 and CNV responses observed during detection, is evidence that rat PPC is involved in sustained attention, particularly in the presence of distractors.