False memory for face in short-term memory and neural activity in human amygdala

Cognitive and neural mechanisms underlying false memories: misinformation, distortion or erroneous configuration?

Errors can affect our memory, yet even when there are gaps in our recollection of events, memory often serves us fairly well. Memory formation involves at least three different sub-processes, that are regulated by an underlying neural structure. From a cognitive neuropsychological perspective, a complex process of encoding, consolidating, and retrieval is involved in remembering an event, and it might be hindered by one's emotional state, physiological response to the event itself, and misinformation. As a result, it is very likely that one may struggle to remember specifics of what happened which can increase our susceptibility to the formation of false memories. This has major implications for everyday functioning, as in the case when you mistakenly remember you took your pills when you never did, or where errors have led to false accusations about trauma or abuse, and wrongful convictions of crimes. Memories sometimes contain biases and inaccuracies that prevent them from accurately recalling events. The review will provide an updated overview of current research advances on the cognitive and neural mechanisms underlying inaccurate, distorted, or false memories.

Abnormalities of the Amygdala in schizophrenia: a real world study

BACKGROUND

Amygdala plays an important role in schizophrenia (SC), but its mechanisms are still unclear. Therefore, we investigated the relationship between the resting-state magnetic resonance imaging (rsMRI) signals of the amygdala and cognitive functions, providing references for future research in this area.

METHODS

We collected 40 drug-naïve SC patients and 33 healthy controls (HC) from the Third People's Hospital of Foshan. We used rsMRI and the automatic segmentation tool to extract the structural volume and local neural activity values of the amygdala and conducted Pearson correlation analysis with the Positive and Negative Syndrome Scale (PANSS) and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) scores. Finally, we compared the clinical data, as well as the volume and functional changes of the amygdala in SC patients before and after treatment.

RESULTS

Compared with HC, SC had widespread cognitive impairments, significant abnormalities in left amygdala function, while the reduction in volume of SC was not significant. Further Pearson correlation analysis with Bonferroni correction showed that only Immediate memory (learning) was significantly negatively correlated with fractional amplitude of low-frequency fluctuation (FALFF, r = -0.343, p = 0.001, p' = 0.014 (Bonferroni correction)). When compared and analyzed the data difference of SC before and after treatment, we found that immediate memory and delayed memory of SC showed varying degrees of recovery after treatment (tlearning = -2.641, plearning = 0.011; tstory memory = -3.349, pstory memory = 0.001; tlist recall = -2.071, plist recall = 0.043; tstory recall = -2.424, pstory recall = 0.018). But the brain structure and function did not recover.

CONCLUSION

There was significant dysfunction in the amygdala in SC, and after conventional treatment, the function of the amygdala did not improve with the improvement of clinical symptoms and cognitive function.

Dynamics of working memory process revealed by independent component analysis in an fMRI study

Human memory is prone to errors in many everyday activities but also when cultivating hobbies such as traveling and/or learning a new language. For instance, while visiting foreign countries, people erroneously recall foreign language words that are meaningless to them. Our research simulated such errors in a modified Deese-Roediger-McDermott paradigm for short-term memory with phonologically related stimuli aimed at uncovering behavioral and neuronal indices of false memory formation with regard to time-of-day, a variable known to influence memory. Fifty-eight participants were tested in a magnetic resonance (MR) scanner twice. The results of an Independent Component Analysis revealed encoding-related activity of the medial visual network preceding correct recognition of positive probes and correct rejection of lure probes. The engagement of this network preceding false alarms was not observed. We also explored if diurnal rhythmicity influences working memory processes. Diurnal differences were seen in the default mode network and the medial visual network with lower deactivation in the evening hours. The GLM results showed greater activation of the right lingual gyrus, part of the visual cortex and the left cerebellum in the evening. The study offers new insight into the mechanisms associated with false memories, suggesting that deficient engagement of the medial visual network during the memorization phase of a task results in short-term memory distortions. The results shed new light on the dynamics of working memory processes by taking into account the effect of time-of-day on memory performance.

Time-of-day effects on objective and subjective short-term memory task performance

The time-of-day along with the synchrony effect (better performance at optimal times of the day according to the chronotype) on the cognitive performance has been well established in previous research. This influence is mediated by both circadian and homeostatic processes consistent with the Borbély two-process model. This experiment focused on the objective and subjective performance of the visual short-term memory task requiring holistic processing. Sixty-five young, healthy participants including 40 females were divided into morning and evening types and performed a given task in two sessions - in the morning and in the evening. Type division was made according to the chronotype questionnaire and polymorphism of the PER3 clock gene. The task was a modified version of Deese-Roediger-McDermott paradigm adjusted to study short-term memory, in which visual, abstract stimuli were used. The analysis was based on an exploratory approach investigating the influence of circadian and individual (sex) factors on execution of memory task. Evening types were more accurate in the task compared to morning types, regardless of the part of the day. The time-of-day effect was revealed on objective measures (reaction times for hits and false alarms) and subjective effort put into the performance. The reaction times were slower in the morning unlike the effort that was greater in the evening. The time-of-day × sex interaction was observed in the case of subjective effort: men described the task as more demanding in the evening. The results could be explained by differences in hemispheric dominance depending on the time-of-day. The report provides new patterns of behavioral data analysis, investigating sex aspects and use of self-assessment scales of performance.

False recognitions in short-term memory - Age-differences in neural activity

While the knowledge on age-related differences in susceptibility to episodic false memories is extensive, little is known about this phenomenon in visual short-term memory (STM). Our previous behavioural research indicated that older adults are more confident of their erroneous STM recognitions than young adults. However, unlike in episodic memory, we did not find support for older adults' higher rate of false alarms. To further understand this specific age-difference, here we investigated its neural correlates. First, the pattern of behavioural results replicated the one from our previous experiment. Second, younger adults, when compared to older adults, exhibited higher false recognition-related activity of the visual cortex, the anterior cingulate cortex, the frontal operculum/insular cortex as well as regions within the anterior and dorsolateral prefrontal cortex. No age-differences were observed in hippocampal activity. Third, younger but not older adults presented higher activity in the anterior cingulate cortex and the frontal operculum/insular cortex for false recognitions when compared to highly confident correct rejections. Finally, frontal activity was influenced by both the individuals' performance and their metacognitive abilities. The results suggest that age-related differences in confidence of STM false recognitions may arise from age-differences in performance monitoring and uncertainty processing rather than in hippocampal-mediated binding.

Brain Oscillatory Correlates of Visual Short-Term Memory Errors

Brain dynamics of memory formation were explored during encoding and retention intervals of a visual working memory task. EEG data were acquired while subjects were exposed to grayscale images of widely known object categories (e.g., "luggage," "chair," and "car"). Following a short delay, two probes were shown to test memory accuracy. Oscillatory portraits of successful and erroneous memories were contrasted. Where significant differences were identified, oscillatory traits of false memories (i.e., when a novel probe item of the same category is recognized as familiar) were compared with those of successful and erroneous memories. Spectral analysis revealed theta (6-8 Hz) power over occipital channels for encoding of successful and false memories that was smaller when compared to other types of memory errors. The reduced theta power indicates successful encoding and reflects the efficient activation of the underlying neural assemblies. Prominent alpha-beta (10-26 Hz) activity belonging to the right parieto-occipital channels was identified during the retention interval. It was found to be larger for false memories and errors than that of correctly answered trials. High levels of alpha-beta oscillatory activity for errors correspond to poor maintenance leading to inefficient allocation of WM resources. In case of false memories, this would imply necessary cognitive effort to manage the extra semantic and perceptual load induced by the encoded stimuli.

Neuroanatomical substrates involved in unrelated false facial recognition

Identifying faces is a process central for social interaction and a relevant factor in eyewitness theory. False recognition is a critical mistake during an eyewitness's identification scenario because it can lead to a wrongful conviction. Previous studies have described neural areas related to false facial recognition using the standard Deese/Roediger-McDermott (DRM) paradigm, triggering related false recognition. Nonetheless, misidentification of faces without trying to elicit false memories (unrelated false recognition) in a police lineup could involve different cognitive processes, and distinct neural areas. To delve into the neural circuitry of unrelated false recognition, we evaluated the memory and response confidence of participants while watching faces photographs in an fMRI task. Functional activations of unrelated false recognition were identified by contrasting the activation on this condition vs. the activations related to recognition (hits) and correct rejections. The results identified the right precentral and cingulate gyri as areas with distinctive activations during false recognition events suggesting a conflict resulting in a dysfunction during memory retrieval. High confidence suggested that about 50% of misidentifications may be related to an unconscious process. These findings add to our understanding of the construction of facial memories and its biological basis, and the fallibility of the eyewitness testimony.

Evoked Potentials and Memory/Cognition Tests Validate Brain Atrophy as Measured by 3T MRI (NeuroQuant) in Cognitively Impaired Patients

To our knowledge, this is the largest study evaluating relationships between 3T Magnetic Resonance Imaging (MRI) and P300 and memory/cognitive tests in the literature. The 3T MRI using NeuroQuant has an increased resolution 15 times that of 1.5T MRI. Utilizing NeuroQuant 3T MRI as a diagnostic tool in primary care, subjects (N=169; 19–90 years) displayed increased areas of anatomical atrophy: 34.62% hippocampal atrophy (N=54), 57.14% central atrophy (N=88), and 44.52% temporal atrophy (N=69). A majority of these patients exhibited overlap in measured areas of atrophy and were cognitively impaired. These results positively correlated with decreased P300 values and WMS-III (WMS-III) scores differentially across various brain loci. Delayed latency (p=0.0740) was marginally associated with temporal atrophy; reduced fractional anisotropy (FA) in frontal lobes correlated with aging, delayed P300 latency, and decreased visual and working memory (p=0.0115). Aging and delayed P300 latency correlated with lower FA. The correlation between working memory and reduced FA in frontal lobes is marginally significant (p=0.0787). In the centrum semiovale (CS), reduced FA correlated with visual memory (p=0.0622). Lower demyelination correlated with higher P300 amplitude (p=0.0002). Compared to males, females have higher demyelination (p=0.0064). Along these lines, the higher the P300 amplitude, the lower the bilateral atrophy (p=0.0165). Hippocampal atrophy correlated with increased auditory memory and gender, especially in males (p=0.0087). In considering temporal lobe atrophy correlations: delayed P300 latency and high temporal atrophy (p=0.0740); high auditory memory and low temporal atrophy (p=0.0417); and high working memory and low temporal atrophy (p=0.0166). Central atrophy correlated with aging and immediate memory (p=0.0294): the higher the immediate memory, the lower the central atrophy. Generally, the validation of brain atrophy by P300 and WMS-III could lead to cost-effective methods utilizable in primary care medicine following further confirmation.