Yael M. Cycowicz

The novelty P3: an event-related brain potential (ERP) sign of the brain's evaluation of novelty

A review of the literature that examines event-related brain potentials (ERPs) and novelty processing reveals that the orienting response engendered by deviant or unexpected events consists of a characteristic ERP pattern, comprised sequentially of the mismatch negativity (MMN) and the novelty P3 or P3a. A wide variety of evidence suggests that the MMN reflects the detection of deviant events, whereas the P3a is associated more with the evaluation of those events for subsequent behavioral action. On the scalp, the novelty P3a is comprised of at least two aspects, one frontal the other posterior, each with different cognitive (and presumably neurologic) correlates. Intracranial ERP investigations and studies of patients with localized brain lesions (and, to some extent, fMRI data) converge with the scalp-recorded data in suggesting a widespread neural network, the different aspects of which respond differentially to stimulus and task characteristics.

Recognition and source memory for pictures in children and adults

The present experiment investigated the developmental aspects of source compared to item memory. College students and 7-8-year-old children viewed pictures drawn in red or green during a study phase, and were asked either to remember the pictures for a subsequent recognition test, or to remember both the pictures and their associated colors for a subsequent source memory test. In the test phase, new and old pictures were presented in black. In the recognition task, participants were asked to make binary old/new recognition judgments, while in the source task, they were asked to make trinary old-green/old-red/new source judgements. Performance on all tasks improved with increasing age, but the age difference for source was much larger than that for item memory. It has been suggested that the frontal lobes play a critical role in the retrieval of source information, and that this brain region relative to the medial temporal lobes continues to develop into late adolescence. Thus, it is possible that immaturity of the frontal lobes may be causally related to the childrens lower performance on the source memory task.

Effects of aging on the novelty P3 during attend and ignore oddball tasks

The effects of attention were assessed on novelty P3 amplitude and scalp distribution elicited by environmental sounds in young and elderly volunteers who participated in either actively attended or ignored oddball conditions. For the young, novelty P3 amplitude decreased with time on task during both attend and ignore sequences. Amplitude decrements were greatest at frontal sites during the attend condition, but at all sites during the ignore condition. A reliable amplitude decrement was not observed for the elderly in either the attend or ignore oddball series. The data suggest that attention differentially activates multiple generators that contribute to scalp-recorded novelty P3 activity. The lack of novelty P3 habituation seen in the elderly is consistent with changes in frontal lobe function as age increases.

Development of and change in cognitive control: A comparison of children, young adults, and older adults

Cognitive control involves adjustments in behavior to conflicting information, develops throughout childhood, and declines in aging. Accordingly, developmental and age-related changes in cognitive control and response-conflict detection were assessed in a response-compatibility task. We recorded performance measures, pre-response time (pre-RT) activity and medial frontal negativity (MFN)—sequentially occurring, putative event-related potential (ERP) indexes, respectively, of cognitive control and response-conflict detection. When response conflict reached the highest levels by requiring incompatible responses on posterror trials, children and older adults showed the greatest performance decrements. ERPs indicated that young adults implemented control (pre-RT) and detected the increased conflict (MFN) only when that conflict was at the highest levels, whereas children and older adults did so at lower levels (e.g., posterror, compatible responses). Consequently, the developmental and age-related performance decrements observed here may be due to the undifferentiated and inefficient manner in which children and older adults recruited the processes associated with both cognitive control and response-conflict detection.

Pictures and Their Colors: What Do Children Remember?

Theories regarding childrens reliability as witnesses suggest that children are more likely to confuse memories from different sources especially when the sources are highly similar. To investigate the developmental aspects of source retrieval, we measured brain electrical activity from children and adults while they retrieved content and source information. Similar brain responses among the age groups were found when participants were asked to retrieve content information. However, retrieval of source information improved with age and was accompanied by different patterns of brain potentials. The results implicate immaturity of frontal lobe structures in childrens difficulty in retrieving source information.

Memory development and event-related brain potentials in children

This review examines the evidence for the maturation of memory function during childhood using event-related brain potentials (ERP), and behavioral measures. It has been shown that brain structures implicated in different forms of memory mature during the first and into the second decade of life. Whereas the maturation rates of implicit and explicit memory have not been directly assessed in the literature, studies of the maturation of the corresponding brain regions imply that there should be a progression in the maturation of the different forms of memory. This review also motivates the use of brain imaging techniques for investigation of memory systems during the developing years. Although, only a handful of such studies with children are currently available, they demonstrate that such techniques can provide information that may be unavailable otherwise. For example, when children fail to generate the ERP old/new effect, an index of episodic retrieval, it has been suggested that they may lack the necessary pre-existing representations in their long-term lexical or semantic memories. Similarly, age-related differences in ERP scalp topography during source memory paradigms suggest that children, who do not appear to show frontal scalp activity, lack inputs from frontal regions that are necessary for successful retrieval of source information. Future research with children will reveal more details about the nature of mnemonic processing during the developmental years.

A Developmental Trajectory in Implicit Memory is Revealed by Picture Fragment Completion

Dissociations between performance on implicit and explicit tasks have often been taken as evidence that different neural structures subserve the two types of memory. One such dissociation involves developmental differences that emerge in explicit tasks, but which appear to be absent in implicit tasks. Such findings are consistent with the idea that implicit memory is subserved by a more primitive system that evolves earlier at both phylogenetic and ontogenetic levels. The present paper reviews previous studies that claimed to find evidence that implicit memory is fully developed in very young children. Issues of measurement error, ceiling effects, and insufficient power brought up questions about those studies with respect to the developmental issue. The present study compares performance on implicit (picture fragment completion) and explicit (free recall and recognition) memory tasks with groups ranging in age from 5–28 years. We find a reliable developmental trend in both implicit and explicit performance in which the former cannot be attributed to the operation ofexplicit memory processes. Thus, we conclude that implicit memory, like explicit memory, develops with age.

Source memory for the color of pictures: Event‐related brain potentials (ERPs) reveal sensory‐specific retrieval‐related activity

Remembering the context (i.e., source) in which an event occurred reveals episodic memory effects (EM) in the event-related brain potentials (ERP). In some verbal source memory experiments, a late prefrontal EM effect has been observed. In a different, pictorial source memory paradigm, a late, parieto-occipital EM effect was recorded. To assess whether these two EM effects stemmed from differences in task paradigms or from source-attribute differences, ERPs were recorded during source memory retrieval for object colors in two tasks. In the sequential task, old/new judgments were followed by source judgments (i.e., color). In the exclusion task, source memory judgments coincided with recognition judgments. For both tasks, late, parietao-occipital EM effects were observed. These findings suggest that it is not the nature of the task, but rather the perceptual characteristics of the source that lead to the presence of the parieto-occipital EM effect. The data further imply that memories for perceptual attributes such as color are stored in and retrieved from sensory-specific cortical areas.

The effect of intention to learn novel, environmental sounds on the novelty P3 and old/new recognition memory

Brain electrical activity was recorded while 32 young adults listened to frequent tones, infrequent target tones, and infrequent novel environmental sounds (some of which repeated). Subjects in the incidental group were not informed about the novel sounds, while subjects in the intentional group were informed and, in addition, were asked to memorize them for a subsequent memory test. Following the novelty oddball task, all subjects were given an old/new sound recognition memory task. The novelty P3 showed a more anterior scalp distribution and an effect of repetition in the incidental compared to the intentional group, suggesting that pre-categorizing the novel sounds influenced how they were processed. For the intentional group only, a subsequent memory effect was elicited by novel sounds that were subsequently recognized compared to those that were not, although both groups showed robust old/new ERP effects during the recognition task. The robust subsequent memory effects in the intentional group were associated with greater recognition accuracy of familiar environmental sounds relative to the incidental group. These data suggest that the encoding activity reflected in the ERP subsequent memory effect may have engendered an advantage in subsequent recognition memory performance.

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.