Potential (ERP) studies of recognition memory for faces

Speak My Language and I Will Remember Your Face Better: An ERP Study

Here we investigated how the language in which a person addresses us, native or foreign, influences subsequent face recognition. In an old/new paradigm, we explored the behavioral and electrophysiological activity associated with face recognition memory. Participants were first presented with faces accompanied by voices speaking either in their native (NL) or foreign language (FL). Faces were then presented in isolation and participants decided whether the face was presented before (old) or not (new). The results revealed that participants were more accurate at remembering faces previously paired with their native as opposed to their FL. At the event-related potential (ERP) level, we obtained evidence that faces in the NL were differently encoded from those in the FL condition, potentially due to differences in processing demands. During recognition, the frontal old/new effect was present (with a difference in latency) regardless of the language with which a face was associated, while the parietal old/new effect appeared only for faces associated with the native language. These results suggest that the language of our social interactions has an impact on the memory processes underlying the recognition of individuals.

Separating content-specific retrieval from post-retrieval processing

According to cortical reinstatement accounts, neural processes engaged at the time of encoding are re-engaged at the time of memory retrieval. The temporal precision of event-related potentials (ERPs) has been exploited to assess this possibility, and in this study ERPs were acquired while people made memory judgments to visually presented words encoded in two different ways. There were reliable differences between the scalp distributions of the signatures of successful retrieval of different contents from 300 to 1100 ms after stimulus presentation. Moreover, the scalp distributions of these content-sensitive effects changed during this period. These findings are, to our knowledge, the first demonstration in one study that ERPs reflect content-specific processing in two separable ways: first, via reinstatement, and second, via downstream processes that operate on recovered information in the service of memory judgments.

More than a feeling: Pervasive influences of memory without awareness of retrieval

The subjective experiences of recollection and familiarity have featured prominently in the search for neurocognitive mechanisms of memory. However, these two explicit expressions of memory, which involve conscious awareness of memory retrieval, are distinct from an entire category of implicit expressions of memory that do not entail such awareness. This review summarizes recent evidence showing that neurocognitive processing related to implicit memory can powerfully influence the behavioral and neural measures typically associated with explicit memory. Although there are striking distinctions between the neurocognitive processing responsible for implicit versus explicit memory, tests designed to measure only explicit memory nonetheless often capture implicit memory processing as well. In particular, the evidence described here suggests that investigations of familiarity memory are prone to the accidental capture of implicit memory processing. These findings have considerable implications for neurocognitive accounts of memory, as they suggest that many neural and behavioral measures often accepted as signals of explicit memory instead reflect the distinct operation of implicit memory mechanisms that are only sometimes related to explicit memory expressions. Proper identification of the explicit and implicit mechanisms for memory is vital to understanding the normal operation of memory, in addition to the disrupted memory capabilities associated with many neurological disorders and mental illnesses. We suggest that future progress requires utilizing neural, behavioral, and subjective evidence to dissociate implicit and explicit memory processing so as to better understand their distinct mechanisms as well as their potential relationships. When searching for the neurocognitive mechanisms of memory, it is important to keep in mind that memory involves more than a feeling.

FN400 potentials are functionally identical to N400 potentials and reflect semantic processing during recognition testing

The "F" in FN400 denotes a more frontal scalp distribution relative to the morphologically similar N400 component-a distinction consistent with the hypothesized distinct roles of FN400 in familiarity memory versus N400 in language. However, no direct comparisons have substantiated these assumed dissimilarities. To this end, we manipulated short-term semantic priming during a recognition test. Semantic priming effects on N400 were indistinguishable from memory effects at the same latency, and semantic priming strongly modulated the "FN400," despite having no influence on familiarity memory. Thus, no evidence suggested either electrophysiological or functional differences between the N400 and FN400, and findings were contrary to the linking of the "FN400" to familiarity. Instead, it appears that semantic/conceptual priming (reflected in the N400) occurs during recognition tests and is frequently (mis)labeled as FN400 and attributed to familiarity.

Current source density (CSD) old/new effects during recognition memory for words and faces in schizophrenia and in healthy adults

We previously reported a preserved 'old-new effect' (enhanced parietal positivity 300-800 ms following correctly-recognized repeated words) in schizophrenia over mid-parietal sites using 31-channel nose-referenced event-related potentials (ERP) and reference-free current source densities (CSD). However, patients showed poorer word recognition memory and reduced left lateral-parietal P3 sources. The present study investigated whether these abnormalities are specific to words. High-density ERPs (67 channels) were recorded from 57 schizophrenic (24 females) and 44 healthy (26 females) right-handed adults during parallel visual continuous recognition memory tasks using common words or unknown faces. To identify and measure neuronal generator patterns underlying ERPs, unrestricted Varimax-PCA was performed using CSD estimates (spherical spline surface Laplacian). Two late source factors peaking at 442 ms (lateral parietal maximum) and 723 ms (centroparietal maximum) accounted for most of the variance between 250 and 850 ms. Poorer (76.6+/-20.0% vs. 85.7+/-12.4% correct) and slower (824+/-170 vs. 755+/-147 ms) performance in patients was accompanied by reduced stimulus-locked parietal sources. However, both controls and patients showed mid-frontal (442 ms) and left parietal (723 ms) old/new effects in both tasks. Whereas mid-frontal old/new effects were comparable across groups and tasks, later left parietal old/new effects were markedly reduced in patients over lateral temporoparietal but not mid-parietal sites, particularly for words, implicating impaired phonological processing. In agreement with prior results, ERP correlates of recognition memory deficits in schizophrenia suggest functional impairments of lateral posterior cortex (stimulus representation) associated with conscious recollection. This deficit was more pronounced for common words despite a greater difficulty to recall unknown faces, indicating that it is not due to a generalized cognitive deficit in schizophrenia.

Effects of multiple study-test repetition on the neural correlates of recognition memory: ERPs dissociate remembering and knowing

Event-related potential (ERP) frontal (300-500 ms) and parietal (500-700 ms) episodic memory (EM) effects are thought to reflect, respectively, familiarity and recollection. However, as most ERP studies use preexperimentally familiar items, an alternative idea is that the frontal EM effect reflects conceptual priming. Repetition of unnameable symbols was used to assess modulations of the putative ERP indices of familiarity and recollection. The same symbols were viewed in each of 4 study/test blocks. Increases in familiarity and conceptual processing of symbols did not modulate the frontal EM effect, suggesting that it reflects neither familiarity nor conceptual priming. The magnitude of the parietal EM effect increased and its onset latency decreased across tests for items given remember (R) but not know (K) judgments. R and K old-new topographies differed. These findings support dual-process proposals that familiarity- and recollection-based processes are distinct.