[1][2] It is generally found to be largest over parietal scalp sites (relative to reference electrodes placed on the mastoid processes), beginning around 400–500 ms after the onset of a stimulus and lasting for a few hundred milliseconds.
The component that came to be called the LPC has been associated with episodic memory and was first described in ERP studies examining either repetition or recognition effects.
[9] Results showed that ERPs to old items were characterized by decreases in an negativity between 300 and 500 ms (N400) and increases in a subsequent, partially overlapping positivity (LPC/P300).
As reviewed by Friedman and Johnson,[1] the LPC is typically seen in the form of a broad positivity between 400 and 800 ms post-stimulus onset.
LPCs have been recorded to words, line drawings, sounds, and meaningless shapes, and it is seen in both long and short-term memory paradigms.
[15][16][17] Furthermore, LPC amplitude is also sensitive to levels of processing manipulation, being larger for more deeply encoded items.
[4][13] Thus, these data suggest that the LPC amplitude is closely allied with recollection and reflects successful retrieval.
Its amplitude was larger in ERPs evoked by words attracting correct versus incorrect recognition decisions.
When the information retrieved was about spatial location, the distribution was bilaterally symmetric over the occipital lobe of the brain.
[17] Alternatively, the effect might index attentional orienting to recollected information,[19][20] rather than processes supporting its representation or maintenance.
It has recently been argued[21] that findings indicating that the effect varies according to the amount of information recollected[21][22] are more consistent with the first of these two proposals.
[18] The difference in the response pattern of the LPC, in comparison with other components elicited in memory tasks, such as the N400, has played an important role in debates about dual-process theories of memory, which postulate qualitatively different mechanisms underlying familiarity and recollection.
Results from studies of patients with brain damage, described above, indicate that medial temporal lobe areas and the hippocampus contribute to the processes indexed by the LPC, although perhaps not directly to the recorded scalp activity.