Odor identification accuracy declines following 24 h of sleep deprivation

Brain imaging studies demonstrate that sleep deprivation reduces glucose metabolism and blood flow in the prefrontal cortex, and such reductions are associated with impairments in cognitive functioning. Although some of the greatest metabolic declines occur within the orbitofrontal cortex, little is known about the effects of sleep loss on the types of processes mediated by this region, including emotion, motivation, feeding, and olfaction. The present study tested odor identification accuracy when individuals were well rested and again following 24 h of wakefulness. Relative to rested baseline performance, sleep-deprived individuals demonstrated a significant decline in the ability to identify specific odors on the Smell Identification Test. This decrement in olfactory functioning occurred concomitantly with slowed psychomotor speed and increased ratings of self-reported sleepiness. Performance on a task that required complex mental set shifting did not change significantly following sleep deprivation, suggesting that the decrements in odor identification could not be attributed to task difficulty. Finally, while there was no relationship between subjective sleepiness and odor identification at rested baseline, greater subjective sleepiness was associated with better odor identification ability following 24 h of sleep loss. Possible implications of these findings are discussed.

Differential time course and intensity of PFC activation for men and women in response to emotional stimuli: a functional near-infrared spectroscopy (fNIRS) study

Using functional near-infrared spectroscopy (fNIRS) we recorded prefrontal cortex (PFC) activation during positive, negative and neutral film clips, based on affective ratings according to their valence and arousal, to assess gender differences in cerebral activation in 15 male and 15 female volunteers. To record PFC activation, five movie clips were presented on a 17-in. TFT screen. The recordings included a pre-stimulus 5-s local baseline and "on" and "off" segments of data, referring to fNIRS Oxy-Hb levels while stimulation (movie clip) was present and during an inter-stimulus blank screen. Our data showed gender differences in the delay period to initial PFC activation and in the course and intensity of activation produced by affective visual stimuli. During the exposure or "on" period of the stimuli we observed more pronounced overshoot and undershoot in men versus women across the range of emotions elicited. This effect was even more pronounced following stimulus cessation ("off" period). The results indicate that gender and the duration of recordings may affect the results of emotional neuroimaging studies.

Changes of cerebral blood oxygenation and optical pathlength during activation and deactivation in the prefrontal cortex measured by time-resolved near infrared spectroscopy

To determine the alterations in optical characteristics and cerebral blood oxygenation (CBO) during activation and deactivation, we evaluated the changes in mean optical pathlength (MOP) and CBO induced by a verbal fluency task (VFT) and driving simulation in the right and left prefrontal cortex (PFC), employing a newly developed time-resolved near infrared spectroscopy, which allows quantitative measurements of the evoked-CBO changes by determining the MOP with a sampling time of 1 s. The results demonstrated differences in MOP in the foreheads with the subjects and wavelength; however, there was no significant difference between the right and left foreheads (p > 0.05). Also, both the VFT and driving simulation task did not affect the MOP significantly as compared to that before the tasks (p > 0.05). In the bilateral PFCs, the VFT caused increases of oxyhemoglobin and total hemoglobin associated with a decrease of deoxyhemoglobin, while the driving simulation task caused decreases of oxyhemoglobin and total hemoglobin associated with an increase of deoxyhemoglobin; there were no significant differences in evoked-CBO changes between the right and left PFC. The present results will be useful for quantitative measurement of hemodynamic changes during activation and deactivation in the adults by near infrared spectroscopy.

Cerebral blood flow changes during vagus nerve stimulation for depression

Positron emission tomography (PET oxygen-15 labeled water or PET [15O]H2O) was used to identify changes in regional cerebral blood flow (rCBF) in response to acute vagus nerve stimulation (VNS) in four subjects with treatment-resistant major depression (TRMD). Four 90-s PET [15O]H2O scans were performed on each subject in an off-on sequence (2 VNS de-activated; 2 VNS activated). PET images were aligned, normalized for global uptake, and resampled to standard atlas space. Statistical t-images were used to evaluate change. VNS-induced increases in rCBF were found in the bilateral orbitofrontal cortex, bilateral anterior cingulate cortex, and right superior and medial frontal cortex. Decreases were found in the bilateral temporal cortex and right parietal area. Regions of change were consistent with brain structures associated with depression and the afferent pathways of the vagus nerve.

Effect of catechol-O-methyltransferase val158met genotype on attentional control

The cingulate cortex is richly innervated by dopaminergic projections and plays a critical role in attentional control (AC). Evidence indicates that dopamine enhances the neurophysiological signal-to-noise ratio and that dopaminergic tone in the frontal cortex is critically dependent on catechol-O-methyltransferase (COMT). A functional polymorphism (val158met) in the COMT gene accounts for some of the individual variability in executive function mediated by the dorsolateral prefrontal cortex. We explored the effect of this genetic polymorphism on cingulate engagement during a novel AC task. We found that the COMT val158met polymorphism also affects the function of the cingulate during AC. Individuals homozygous for the high-activity valine ("val") allele show greater activity and poorer performance than val/methionine ("met") heterozygotes, who in turn show greater activity and poorer performance than individuals homozygous for the low-activity met allele, and these effects are most evident at the highest demand for AC. These results indicate that met allele load and presumably enhanced dopaminergic tone improve the "efficiency" of local circuit processing within the cingulate cortex and thereby its function during AC.

Decisions under uncertainty: probabilistic context influences activation of prefrontal and parietal cortices

Many decisions are made under uncertainty; that is, with limited information about their potential consequences. Previous neuroimaging studies of decision making have implicated regions of the medial frontal lobe in processes related to the resolution of uncertainty. However, a different set of regions in dorsal prefrontal and posterior parietal cortices has been reported to be critical for selection of actions to unexpected or unpredicted stimuli within a sequence. In the current study, we induced uncertainty using a novel task that required subjects to base their decisions on a binary sequence of eight stimuli so that uncertainty changed dynamically over time (from 20 to 50%), depending on which stimuli were presented. Activation within prefrontal, parietal, and insular cortices increased with increasing uncertainty. In contrast, within medial frontal regions, as well as motor and visual cortices, activation did not increase with increasing uncertainty. We conclude that the brain response to uncertainty depends on the demands of the experimental task. When uncertainty depends on learned associations between stimuli and responses, as in previous studies, it modulates activation in the medial frontal lobes. However, when uncertainty develops over short time scales as information is accumulated toward a decision, dorsal prefrontal and posterior parietal contributions are critical for its resolution. The distinction between neural mechanisms subserving different forms of uncertainty resolution provides an important constraint for neuroeconomic models of decision making.

Distributed neural representation of expected value

Anticipated reward magnitude and probability comprise dual components of expected value (EV), a cornerstone of economic and psychological theory. However, the neural mechanisms that compute EV have not been characterized. Using event-related functional magnetic resonance imaging, we examined neural activation as subjects anticipated monetary gains and losses that varied in magnitude and probability. Group analyses indicated that, although the subcortical nucleus accumbens (NAcc) activated proportional to anticipated gain magnitude, the cortical mesial prefrontal cortex (MPFC) additionally activated according to anticipated gain probability. Individual difference analyses indicated that, although NAcc activation correlated with self-reported positive arousal, MPFC activation correlated with probability estimates. These findings suggest that mesolimbic brain regions support the computation of EV in an ascending and distributed manner: whereas subcortical regions represent an affective component, cortical regions also represent a probabilistic component, and, furthermore, may integrate the two.

Delay-period activity in the prefrontal cortex: one function is sensory gating

The prefrontal cortex (PFC) contributes to working memory functions via executive control processes that do not entail the storage, per se, of mnemonic representations. One of these control processes may be a sensory gating mechanism that facilitates retention of representations in working memory by down-regulating the gain of the sensory processing of intervening irrelevant stimuli. This idea was tested by scanning healthy young adults with functional magnetic resonance imaging while they performed a delayed face-recognition task. The 2 x 2 factorial design varied the factors of Memory (present, absent) and Distraction (present, absent). During memory-present trials, target and probe stimuli were individual gray-scale male faces. Memory-absent trials were identical, except that they employed the same recurring female faces (denoting a "no memory" trial). Distraction-present trials featured rapid serial visual presentation of bespectacled male faces during the two middle seconds of the delay. The first step of the analyses identified dorsolateral PFC (dlPFC) and inferior occipitotemporal cortex (IOTC) voxels exhibiting delay-period activity in memory-present/distraction-absent trials, that is, the "unfilled" delay. Within these voxels, distraction-evoked activity in the dlPFC was markedly higher during trials that required the concurrent short-term retention of information than on those that did not, whereas the opposite effect was seen in the IOTC. These results are consistent with the view that processes related to sensory gating account for a portion of the delay-period activity that is routinely observed in the dlPFC.

Prefrontal hemodynamic activity predicts false memory--a near-infrared spectroscopy study

Evidence from lesion studies suggests an important role of the prefrontal cortex (PFC) in the reconstructive processes of episodic memory or memory distortion. Results from functional imaging studies imply PFC involvement during the illusionary recollection of non-experienced events. Here, we used a two-channel near-infrared spectroscopy (NIRS) system and conducted real-time monitoring of PFC hemodynamics, while subjects studied word lists and subsequently recognized unstudied items (false recognition). Bilateral increases in the oxygenated hemoglobin concentration ([oxy-Hb]) were observed during false recognition compared to true recognition, and a left PFC dominant increase of [oxy-Hb] was observed during encoding phases where subjects later claimed that they recognized unstudied words. Traces of semantic processing, reflected primarily in the left PFC activity, could eventually predict whether subjects falsely recognize non-experienced events.

COMT genotype influences prefrontal response to emotional distraction

Early studies of genetic effects on brain activity have been conducted to investigate primarily either the influence of polymorphisms in dopaminergic genes, especially the catechol-O-methyltransferase (COMT) gene, on prefrontal cognitive processes such as working memory, or that of polymorphisms in the serotonin transporter gene on the amygdala response to threatening stimuli. Here, we address genetic influences on the neural systems underlying cognitive-affective interactions. Specifically, we assess the effect of the CO MT val158met polymorphism onfrontal regulation of attentionunder emotional distraction. Healthy volunteers were scanned while performing a house-matching task with affectively negative versus neutral distractors. Effects of val allele load were examined on frontal regions associated with attentional control and emotion regulation, and on parahippocampal regions associated with perception of houses. As we predicted, val load correlated positively with activity in control- and task-related regions during performance under emotional distraction. These findings provide an initial step toward identifying genetic contributions to interindividual variability in recruitment of mechanisms that regulate affective processing.

Antisocial personality and stress-induced brain activation in cocaine-dependent patients

We explore the neural correlates underlying distress processing in antisocial personality in cocaine-dependent individuals. Twenty-seven abstinent cocaine-dependent individuals took part in script-guided stress imagery in a functional magnetic resonance imaging study. Regional brain activation during stress imagery was compared with a baseline period, for male and female participants separately. Their California Psychological Inventory socialization scores were then correlated in region of interest analysis with corticolimbic brain regions that showed significant activation during stress. The effect size of activity change in the medial prefrontal cortex is associated with lower socialization score (i.e. greater sociopathy) and with the change in heart rate, but only among female participants. These results highlight important sex differences in the association between antisocial personality and distress processing in cocaine-dependent individuals.

Using fMRI to investigate a component process of reflection: prefrontal correlates of refreshing a just-activated representation

Using fMRI, we investigated the functional organization of prefrontal cortex (PFC) as participants briefly thought of a single just-experienced item (i.e., refreshed an active representation). The results of six studies, and a meta-analysis including previous studies, identified regions in left dorsolateral, anterior, and ventrolateral PFC associated in varying degrees with refreshing different types of information (visual and auditory words, drawings, patterns, people, places, or locations). In addition, activity increased in anterior cingulate with selection demands and in orbitofrontal cortex when a nonselected item was emotionally salient, consistent with a role for these areas in cognitive control (e.g., overcoming "mental rubbernecking"). We also found evidence that presenting emotional information disrupted an anterior component of the refresh circuit. We suggest that refreshing accounts for some neural activity observed in more complex tasks, such as working memory, long-term memory, and problem solving, and that its disruption (e.g., from aging or emotion) could have a broad impact.

Three-dimensional stereotactic surface projection study of freezing of gait and brain perfusion image in Parkinson's disease

Gait disturbance is a cardinal symptom in patients with Parkinson's disease. Among the gait disturbances, freezing of gait is a unique and troublesome symptom, but its mechanism is unclear. We compared brain perfusion images using three-dimensional stereotactic surface projection analysis of N-isopropyl-p-123I iodoamphetamine single photon emission computed tomography between Parkinson's disease patients with freezing of gait and those without. Twenty-four cases (freezing of gait group) with Parkinson's disease with freezing of gait, and 31 Hoehn and Yahr stage-matched cases (no freezing of gait group) with Parkinson's disease without freezing of gait were studied. Bilateral Brodmann area 11 perfusion of the freezing of gait group decreased significantly compared to that of the no freezing of gait group. The Brodmann area 11 may play important roles in gait, and impairment in this region may have a close relationship with freezing of gait in Parkinson's disease.

Corticolimbic blood flow during nontraumatic emotional processing in posttraumatic stress disorder

CONTEXT

Recent brain imaging studies implicate dysfunction of limbic and paralimbic circuitry, including the amygdala and medial prefrontal cortex (MPFC), in the pathogenesis of posttraumatic stress disorder (PTSD) during traumatic recollection and imagery. However, the relationship between activity in these regions and general emotional processing unrelated to traumatic experience has not been fully examined.

OBJECTIVE

To investigate activity in the limbic and paralimbic brain regions in PTSD in response to a challenge with emotionally salient generic visual images.

DESIGN

Cross-sectional, case-control study.

SETTING

Academic medical center.

PARTICIPANTS

Sixteen Vietnam veterans with combat-related PTSD (PTSD group), 15 combat-exposed Vietnam veterans without PTSD (combat control group), and 15 age- and sex-matched healthy controls (normal control group).

MAIN OUTCOME MEASURES

We used positron emission tomography to study regional cerebral blood flow while participants viewed complex visual pictures with negatively valenced/aversive, nonaversive ("neutral"), and blank pictures. Psychophysiologic and emotional self-report data were also recorded.

RESULTS

All 3 groups activated the dorsal MPFC to general salient content. Controls without PTSD activated the left amygdala in response to aversive stimuli. Normal controls activated the ventral MPFC and combat-exposed non-PTSD and PTSD participants exhibited either no response or deactivation in these regions, respectively, during negative emotional experience.

CONCLUSIONS

Consistent with current functional neuroanatomic models, patients with PTSD exhibited altered neural responses in the amygdala and ventral MPFC during the processing of emotionally salient but trauma-unrelated stimuli, potentially reflecting disorder-specific changes. Activation of the amygdala and lack of ventral MPFC deactivation to negatively valenced images in combat controls may reflect compensatory changes after trauma exposure that are not associated with PTSD.

Reduced cortical activity due to chronic low blood pressure: an EEG study

Alterations in cortical activation processes due to chronic low blood pressure were investigated. In 40 hypotensive subjects and 40 normotensive controls, the contingent negative variation (CNV), induced by a constant foreperiod reaction time task, was assessed at nine scalp sites (F3, Fz, F4, C3, Cz, C4, P3, Pz, P4). Additionally, spontaneous EEG was recorded at resting conditions. In hypotensives, a reduced amplitude of both the early and the late component of the CNV were found at Cz. At Fz the early CNV was reduced. Hypotensives exhibited longer reaction times, and the reaction time was negatively correlated with the CNV amplitude. Resting alpha power correlated negatively with blood pressure. The findings can be related to cognitive deficits due to hypotension found in earlier studies. The effects of hypotension on cortical activity are discussed to be mediated by afferents from the cardiovascular system to the prefrontal cortex as well as by reduced cerebral blood flow.

Ventromedial prefrontal activity correlates with depressed mood in adolescent children

In adults, the medial prefrontal cortex and anterior cingulate gyrus are preferentially activated during emotion-related processes, including normal sadness and pathological depression. It is not clear, however, whether similar regional activity is also characteristic of depressed mood during adolescence. We correlated whole brain activity during a fear face perception task with scores on the Beck Depression Inventory in 16 adolescents undergoing functional magnetic resonance imaging. After controlling for age, depressed mood scores correlated with increased activity within the ventromedial prefrontal cortex and rostral anterior cingulate gyrus, consistent with findings previously reported for sadness and depression in adults, suggesting that the neural substrates of depressed mood are established early in life and remain relatively consistent across development into adulthood.

Brain activation during craving for alcohol measured by positron emission tomography

OBJECTIVE

Craving for alcohol is probably involved in acquisition and maintenance of alcohol dependence to a substantial degree. However, the brain substrates and mechanisms that underlie alcohol craving await more detailed elucidation.

METHOD

Positron emission tomography was used to map regional cerebral blood flow (CBF) in 21 detoxified patients with alcohol dependence during exposure to alcoholic and non-alcoholic beverages.

RESULTS

During the alcohol condition compared with the control condition, significantly increased CBF was found in the ventral putamen. Additionally, activated areas included insula, dorsolateral prefrontal cortex and cerebellum. Cerebral blood flow increase in these regions was related to self-reports of craving assessed in the alcoholic patients.

CONCLUSIONS

In this investigation, cue-induced alcohol craving was associated with activation of brain regions particularly involved in brain reward mechanisms, memory and attentional processes. These results are consistent with studies on craving for other addictive substances and may offer strategies for more elaborate studies on the neurobiology of addiction.

Association of neural and physiological responses during voluntary emotion suppression

Recent neuroimaging studies have shown that several prefrontal regions play critical roles in inhibiting activation of limbic regions during voluntary emotion regulation. The present study aimed to confirm prior findings and to extend them by identifying the frontal neural circuitry associated with regulation of peripheral physiological responses during voluntary emotion suppression. Ten healthy female subjects were presented with affectively positive, neutral, and negative pictures in each of an Attending and Suppression task. Regional cerebral blood-flow changes were measured using 15O-water positron emission tomography, and autonomic (heart rate: HR, skin conductance response: SCR) and endocrine (adrenocorticotropic hormone: ACTH) indices were measured during both tasks. The left amygdala and the right anterior temporal pole were activated during the Attending task, whereas activation was observed in the left lateral prefrontal cortex (LPFC), including the adjacent medial prefrontal cortex (MPFC), and medial orbitofrontal cortex (MOFC) during the Suppression task. In the Attending task, activation in the amygdala and MOFC positively correlated with magnitudes of the SCR and ACTH responses. Emotion suppression elicited enhancement of SCR and the strength of the effect positively correlated with activation in the MOFC. These results suggest that the MOFC plays a pivotal role in top-down regulation of peripheral physiological responses accompanying emotional experiences.

Darwin and the Neural Bases of Emotion and Affective Style

This article presents an overview of ways to think about the brain and emotion and consider the role of evolution and expression in shaping the neural circuitry of affective processing. Issues pertaining to whether there are separate unique neural modules hard-wired for emotion processing or whether affective processing uses more generalized circuitry are considered. Relations between affect and cognition--specifically, memory--are examined from the perspective of overlapping neural systems. The role of individual differences in neural function in affective style are discussed, and the concepts of affective chronometry, or the time course of emotional responding and emotion regulation, are introduced. Finally, the extent to which certain emotional traits can be viewed as trainable skills is considered, and the relevance of work on neural plasticity to the skill framework is addressed. Data from a variety of sources using different types of measures is brought to bear on these questions, including neuroimaging and psychophysiological measures, studies of individuals of different ages ranging from early childhood to old age, studies of nonhuman primates, and observations of patients with localized brain damage. Emotions are viewed as varying in both type and dimension. Honoring brain circuitry in parsing the domain of affects will result in distinctions and differentiations that are not currently incorporated in traditional classification schemes.

Instructed smoking expectancy modulates cue-elicited neural activity: a preliminary study

In recent years, research applying functional neuroimaging to the study of cue-elicited drug craving has emerged. This research has begun to identify a distributed system of brain activity during drug craving. A review of this literature suggested that expectations regarding the opportunity to use a drug affected the pattern of neural responses elicited by drug cues. Using functional magnetic resonance imaging (fMRI), we examined the effects of smoking expectancy on the neural response to neutral (e.g., roll of tape) and smoking-related (a cigarette) stimuli in male cigarette smokers deprived of nicotine for 8 hr. As predicted, several brain regions (e.g., the anterior cingulate cortex) exhibited differential activation during cigarette versus neutral cue exposure. Moreover, we found that subregions of the prefrontal cortex (i.e., ventromedial, ventrolateral, and dorsolateral prefrontal cortices) showed cue-elicited activation that was modulated by smoking expectancy. These results highlight the importance of perceived drug use opportunity in the neurobiological response to drug cues.

An fMRI study of causal judgments

The capacity to evaluate causal relations is fundamental to human cognition, and yet little is known of its neurocognitive underpinnings. A functional magnetic resonance imaging study was performed to investigate an hypothesized dissociation between the use of semantic knowledge to evaluate specifically causal relations in contrast to general associative relations. Identical pairs of words were judged for causal or associative relations in different blocks of trials. Causal judgments, beyond associative judgments, generated distinct activation in left dorsolateral prefrontal cortex and right pre-cuneus. These findings indicate that the evaluation of causal relations in semantic memory involves additional neural mechanisms relative to those required to evaluate associative relations.

How do we modulate our emotions? Parametric fMRI reveals cortical midline structures as regions specifically involved in the processing of emotional valences

One of the major problems in affective neuroscience of healthy subjects as well as of patients with emotional dysfunctions is to disentangle emotional core functions and non-emotional processes. Emotional valence is considered an emotional key process. The present study employed a parametric functional magnetic resonance imaging (fMRI) study to address this question. Thirteen healthy volunteers were scanned during emotional stimulus processing (International Affective Picture System). The presented pictures covered the entire range of emotional valences. The fMRI data were consecutively subjected to a preliminary categorical (valence-independent) and a detailed parametric analysis, the latter using individual valence ratings as regressor. The parametric analysis revealed a linear valence-dependent modulation of the BOLD signal in the orbito- and dorsomedial prefrontal cortex (OMPFC, DMPFC), medial parietal cortex (MPC), and insula. In addition, we observed that emotional valence exerts its effects predominantly via modulation of signal decreases. We conclude that the psychological concept of emotional valence may be related to neural processing in cortical midline regions.

Anterior prefrontal cortex and the recollection of contextual information

Recollective memory can involve the retrieval of many different kinds of contextual information, including where and when an event took place, as well as our thoughts and feelings at the time. The brain regions associated with this ability were examined in an event-related fMRI experiment, where participants made decisions about words or famous faces which were presented either on the left or right of a monitor screen. Subsequently, the studied words and faces were again presented and participants underwent fMRI brain scanning while recollecting either which of the decisions they had made on each item ("task memory"), or whether it had been presented on the left or right of the screen ("position memory"). A functional dissociation was observed within anterior prefrontal cortex (principally Brodmann's area 10), with activation in lateral regions associated with remembering either type of information (relative to baseline), and a medial anterior PFC region showing significantly greater activation during the "task memory" conditions. These results suggest different roles for lateral and medial anterior prefrontal cortex in recollection.

Being with virtual others: Neural correlates of social interaction

To characterize the neural correlates of being personally involved in social interaction as opposed to being a passive observer of social interaction between others we performed an fMRI study in which participants were gazed at by virtual characters (ME) or observed them looking at someone else (OTHER). In dynamic animations virtual characters then showed socially relevant facial expressions as they would appear in greeting and approach situations (SOC) or arbitrary facial movements (ARB). Differential neural activity associated with ME>OTHER was located in anterior medial prefrontal cortex in contrast to the precuneus for OTHER>ME. Perception of socially relevant facial expressions (SOC>ARB) led to differentially increased neural activity in ventral medial prefrontal cortex. Perception of arbitrary facial movements (ARB>SOC) differentially activated the middle temporal gyrus. The results, thus, show that activation of medial prefrontal cortex underlies both the perception of social communication indicated by facial expressions and the feeling of personal involvement indicated by eye gaze. Our data also demonstrate that distinct regions of medial prefrontal cortex contribute differentially to social cognition: whereas the ventral medial prefrontal cortex is recruited during the analysis of social content as accessible in interactionally relevant mimic gestures, differential activation of a more dorsal part of medial prefrontal cortex subserves the detection of self-relevance and may thus establish an intersubjective context in which communicative signals are evaluated.

Memory Impairment and Awareness of Memory Deficits inEarly-Stage Alzheimer's Disease

Recognition memory of auditory verbal learning tests and awareness of memory deficits were examined in 24 individuals with early-stage Alzheimer's disease (AD) using a performance prediction-postdiction paradigm. Individuals with AD displayed impaired recognition memory, and recognition performance correlated positively with regional cerebral blood flow at rest in bilateral prefrontal areas and the left medial temporal area. In addition, underawareness of memory deficits was also marked even at this early stage. Individuals with AD retrospectively overestimated memory performance after actual performance, but appeared to benefit from feedback, and displayed intact online awareness of memory dysfunction, leading to normal prediction of the second session. However, individuals with AD failed to retrospectively incorporate incidents of memory failure into generalized self-belief systems. Brain/ behavior correlational analyses suggest that the prefrontal cortex and posterior dorsomedial regions including the precuneus may be involved in self-awareness.