Episodic Memory Precision and Reality Monitoring Following Stimulation of Angular Gyrus

The qualities of remembered experiences are often used to inform “reality monitoring” judgments, our ability to distinguish real and imagined events [Johnson, M. K., & Raye, C. L. Reality monitoring. Psychological Review, 88, 67–85, 1981]. Previous experiments have tended to investigate only whether reality monitoring decisions are accurate or not, providing little insight into the extent to which reality monitoring may be affected by qualities of the underlying mnemonic representations. We used a continuous-response memory precision task to measure the quality of remembered experiences that underlie two different types of reality monitoring decisions: self/experimenter decisions that distinguish actions performed by participants and the experimenter and imagined/perceived decisions that distinguish imagined and perceived experiences. The data revealed memory precision to be associated with higher accuracy in both self/experimenter and imagined/perceived reality monitoring decisions, with lower precision linked with a tendency to misattribute self-generated experiences to external sources. We then sought to investigate the possible neurocognitive basis of these observed associations by applying brain stimulation to a region that has been implicated in precise recollection of personal events, the left angular gyrus. Stimulation of angular gyrus selectively reduced the association between memory precision and self-referential reality monitoring decisions, relative to control site stimulation. The angular gyrus may, therefore, be important for the mnemonic processes involved in representing remembered experiences that give rise to a sense of self-agency, a key component of “autonoetic consciousness” that characterizes episodic memory [Tulving, E. Elements of episodic memory. Oxford, United Kingdom: Oxford University Press, 1985].

Tecnologías aplicadas a la medición del Reality Monitoring (RM).

Este arTIculo teórico presenta un abordaje a las tendencias en técnicas de medición referente al constructo del Reality Monitoring (RM), siendo este un proceso cogniTIvo relevante a la función de diferenciación entre información de fuentes esTImulares internas o externas, dentro de la invesTIgación, esta función es relevante para explicar las alucinaciones y, por ende, crucial en el abordaje de patologías como la esquizofrenia. Se desarrollan tres componentes principales en la evaluación de RM, la neuroimagen por medio del fMRI, la relevancia de la medición psicométrica y el desarrollo de software para la evaluación de tareas. Todo esto, con el propósito de construir una perspectiva crítica sobre el avance del uso de la tecnología en este campo, rescatando adicionalmente, hallazgos en tanto procesos de intervención terapéuticos en rehabilitación cognitiva asociados a RM.

Episodic memory precision and reality monitoring following stimulation of angular gyrus

The qualities of remembered experiences are often used to inform ‘reality monitoring’ judgments, our ability to distinguish real and imagined events (Johnson & Raye, 1981). Previous experiments have tended to investigate only whether reality monitoring decisions are accurate or not, providing little insight into the extent to which reality monitoring may be affected by qualities of the underlying mnemonic representations. We used a continuous-response memory precision task to measure the quality of remembered experiences that underlie two different types of reality monitoring decisions: agency decisions that distinguish actions performed by participants and the experimenter, and perceptual decisions that distinguish perceived and imagined experiences. The data revealed memory precision to be associated with higher accuracy in both agency and perceptual reality monitoring decisions, with reduced precision linked with a tendency to misattribute self-generated experiences to external sources. We then sought to investigate the possible neurocognitive basis of these observed associations by applying brain stimulation to a region that has been implicated in precise recollection of personal events, left angular gyrus. Stimulation of angular gyrus selectively reduced the association between memory precision and self-referential reality monitoring decisions, relative to control site stimulation. Angular gyrus may, therefore, be important for the ability to imbue remembered experiences with a sense of self-agency, a key component of ‘autonoetic consciousness’ that characterises episodic memory (Tulving, 1985).

Transcranial direct current stimulation (tDCS) enhances internal source monitoring abilities in healthy participants

Source monitoring refers to the ability to identify the origin of a memory, for example, whether you remember saying something or thinking about it, and confusions of these sources have been associated with the experience of auditory verbal hallucinations (AVHs). Both AVHs and source confusions are reported to originate from dysfunctional brain activations in the prefrontal cortex (PFC) and the superior temporal gyrus (STG); specifically, it is assumed that a hypoactive PFC and a hyperactive STG gives rise to AVHs and source confusions. We set out to test this assumption by trying to mimic this hypertemporal/hypofrontal model in healthy individuals with transcranial direct current stimulation (tDCS): the inhibitory cathode was placed over the left PFC and the excitatory anode over the left dorsolateral STG. Participants completed a reality monitoring task (distinguishing between external and internal memory sources) and an internal source monitoring task (distinguishing between two or more internal memory sources) in two separate experiments (offline vs. online tDCS). In the offline experiment (n = 34), both source monitoring tasks were completed after tDCS stimulation, and in the online experiment (n = 27) source monitoring tasks were completed while simultaneously being stimulated with tDCS. We found that internal source monitoring abilities were significantly enhanced during active online tDCS, while reality monitoring abilities were unaffected by stimulation in both experiments. We speculate, based on combining the present findings with previous studies, that there might be different brain areas involved in reality and internal source monitoring. While internal source monitoring seems to involve speech production areas, specifically Broca’s area, as suggested in the present study, reality monitoring seems to rely more on the STG and DLPFC, as shown in other studies of the field.

Imagery adds stimulus-specific sensory evidence to perceptual detection

Internally generated imagery and externally triggered perception rely on overlapping sensory processes. This overlap poses a challenge for perceptual reality monitoring: determining whether sensory signals reflect reality or imagination. In this study, we used psychophysics to investigate how imagery and perception interact to determine visual experience. Participants were instructed to detect oriented gratings that gradually appeared in noise while simultaneously either imagining the same grating, a grating perpendicular to the to-be-detected grating, or nothing. We found that, compared to both incongruent imagery and no imagery, congruent imagery caused a leftward shift of the psychometric function relating stimulus contrast to perceptual threshold. We discuss how this effect can best be explained by a model in which imagery adds sensory signal to the perceptual input, thereby increasing the visibility of perceived stimuli. These results suggest that, in contrast to changes in sensory signals caused by self-generated movement, the brain does not discount the influence of self-generated sensory signals on perception.

Fundamental constraints on distinguishing reality from imagination

In order to function in complex environments, humans have evolved to move beyond stimulus-triggered responses to guide behaviour via offline simulations, such as imagination and planning. Contemporary generative models of brain function propose that imagination relies on similar neural machinery to that engaged by veridical perception, a hypothesis supported by neuroimaging data. While allowing for a vast increase in cognitive sophistication, the potential for rich offline simulation raises a new problem: how to distinguish reality from imagination. Here we capitalised on the ability to conduct large-scale, one-trial-per-participant psychophysics via online platforms combined with computational modelling to investigate the characteristics and extent of perceptual reality monitoring failures in the general population. We find striking evidence for a subjective intermixing of imagination and reality – congruent visual imagery increases the likelihood a stimulus is judged as real, and reality judgements increase the experienced vividness of imagery. Using neuroimaging, we go on to show that imagery vividness and perceptual visibility are similarly encoded in the brain. These findings are best explained by a simple theoretical model in which internal and external signals are combined and reality monitoring is implemented by evaluating the total strength of this combined signal against a “reality threshold”. A striking consequence of this account is that it predicts when virtual or imagined signals are strong enough, they become indistinguishable from reality.

Verbal content analysis for the study of Verisimilitude (V1) in the System for Analysis of Validity in Evaluation (SAVE)

In the SAVE Metaprotocol (López, et al, 2018), Verisimilitude (V1) refers to that which has the appearance of truth, possibility of being believed, and with "absence of subjective incredibility". Corresponding to this section is everything related to the analysis of the content of the verbal message and which gives internal coherence to the subject's statement. This phase is obtained directly through the interview with the subject, which we record in order to be able to carry out the content analysis later. It can be using a criterial, structural, or linguistic analysis, or simply employing a study of the communicative pattern. Some examples of content analysis are Statement Validity Analysis (SVA) with its Criteria-Based Content Analysis or CBCA and its validity list. The CBCA is composed of 19 criteria used to assess the content of the statements and which to date has been admitted as court evidence in cases of possible child sexual offense. It is administered together with a validity checklist and its value as evidence depends on the scope of application (Köhnken, Manzanero & Scott 2015). The instrument called Reality Monitoring (RM), like the previous one is a tool used to assess the credibility of the testimony and that focuses on the semantic aspects that differentiate a true statement from a false or not very credible one (Raye & Johnson, 1980). Although in this aspect, we should not make the mistake of confusing credibility with veracity, since when assessing a testimony the truth as such does not exist, and depends on the functioning of our memory, which is not like a tape recorder and is not static, but is constantly exposed to changes and distortions. According to this model, the origin of our memories comes from two basic sources: External Memories, generated from the perception of real situations; and Internal Memories, the product of our imagination. The unconscious reasoning process that our mind follows to decide which information comes from an external source and which forms an internal one is called Reality Monitoring. Four qualitative attributes allow us to differentiate between these two types of memories: