Prof. Joseph Levine, M.D. is an emeritus associate professor in the Division of Psychiatry, Faculty of Health Sciences, Ben Gurion University in Israel. Prof. Levine is a certified psychiatrist with clinical experience in controlled trials of adult psychiatric disorders and in psychotherapy. He was awarded a NRSAD independent investigator grant for the study of Creatine Monohydrate in psychiatric disorders -- mainly Schizophrenia. He resides and treats patients in Tel Aviv and all of central Israel.
Conversation 68: The mechanisms of distinguishing between the outer world of reality and the inner mental world
Greetings to our readers,
The human ability to perceive is not a passive reception of stimuli nor is it purely "mental theater". This concept stems from complex interrelationships between the senses and the internal models of the brain. In order to survive and thrive, we must accurately analyze what arises externally from what is created in our soul internally. This distinction underlies everything from threat detection to social interaction.
However, delusions, hallucinations, and confusion can occur when the neural processes that maintain this boundary go awry.
Historical perspectives
From ancient philosophical debates to 19th century psychophysics, the question of the relationship and distinction of the processes in mind from the occurrences in the outer world has captured the hearts of thinkers. Interest in the mind's ability to distinguish between internal and external phenomena has deep philosophical roots – from Plato's allegory of the cave to Descartes' reflections on the nature of reality.
n modern psychology, Wundt and James recognized the importance of introspection, while Herman von Helmholtz introduced the idea of unconscious inference in perception. Early clinical observations of hallucinations (eg, Esquirol, Kraepelin) framed them as "perceptions without stimuli". In the 20th century, cognitive psychologists developed source-monitoring theories, concurrent with neuroscience research linking hallucinations to abnormal neural activity.
The meaning of the distinction between external and internal reality in neuroscience and psychology
Clinical Importance: Hallucinations and delusions in disorders such as schizophrenia can be perceived as a failure to label internal experiences as self-generated.
Cognitive development: Children learn to distinguish between fantasy and reality over time, a process that reveals the gradual development of source monitoring.
The study of consciousness: understanding how the brain "marks" internal versus external inputs is central to questions about self-awareness and the construction of subjective experience.
How can the human mind distinguish between external reality and internal reality.
The distinction between what comes from the outside world ("external reality") and what is created inside our minds ("internal reality" or imagination) is one of the most basic tasks of the brain. In general, this distinction depends on a series of interrelated mechanisms that integrate sensory processing, predictive models, and higher-order cognitive functions. Below is a simple overview of some of the main processes and brain structures thought to be involved.
Sensory pathways and processing from the bottom up [down to top]
Peripheral sensory organs:
External stimuli (light, sound, touch, etc.) activate special receptors (in the eyes, ears, skin, etc.). These signals reach the brain through nerves and dedicated sensory pathways.
The primary sensory cortex
Each sense is first processed in primary areas (eg, the primary visual cortex in the occipital lobe, the primary auditory cortex in the temporal lobe). These areas handle the most basic features of incoming stimuli (eg, object edges and their movement for vision, pitch and loudness for hearing).
Through these bottom-up pathways, the brain continuously registers and updates incoming external information. The signals are "labeled" as inputs originating outside the body, in part because there is a predictable relationship between environmental changes and these sensory signals (eg, an increase in brightness when you open your eyes).
Internal generators: Imagination and mental imagery
Processing from top to bottom [top to down]
While bottom-up processing originates from incoming sensory signals, top-down processes originate in higher-level brain regions and can "create" or shape perceptions in the absence of direct external stimulation.
Areas involved in imagination and mental imagery include the frontal cortex (for planning and executive functions), the parietal cortex (spatial representation), and the visual association cortex (for mental imagery).
"Reactivation" of the sensory cortex
When you visualize a scene or recall a memory, your brain partially reactivates many of the same sensory circuits used for actual perception.
This partial reactivation (in the absence of accompanying external stimulation) can resemble a real perception. However, the activation pattern and intensity often differ from a real sensory receiver.
Predictive processing framework
A growing body of research suggests that our brains continually use predictive models to interpret and anticipate sensory input:
Internal models
The brain maintains dynamic internal models or "predictions" of what it expects to perceive. These models are updated regularly based on experience and context.
Error signals
When actual sensory input (bottom-up) does not match the prediction (top-down), an "error prediction" occurs.
The brain uses these error signals to adjust the internal model or to adjust attention to relevant signals in the environment.
Distinguishing between self and external
If the brain's internal projections match the incoming signals, the sensation is perceived as real external input (eg, seeing a tree outside the window).
If there is a mismatch (or if the system recognizes that the sensory activation is self-generated), the perception can be labeled as an imagination or an internally generated event (eg, daydreaming about a tree).
Corollary Discharge and Reference Copy
A key neurobiological mechanism for distinguishing between externally generated and self-generated (internal) sensations is associative discharge (also known as referral copy). Although this has been studied mainly in relation to motor control, the same principle is thought to apply to many cognitive processes:
An example of motor control
When you decide to move your hand, your motor cortex sends an instruction ("efferent signal") to the muscles. At the same time, a copy of this instruction ("reference copy" or "colloraly discharge") is sent to sensory areas to predict the expected feedback.
As a result, when the hand touches the arm, the brain "knows" that it has started to act internally and at least partially ignores the sensory input, making the touch feel less surprising (or ticklish).
Inner speech and thought
Similarly, when we produce inner speech (think words in our head), the brain sends a predictive signal to auditory areas. It can help us recognize that the "voice" we hear in our minds is our imagination, and not an external source.
Dysfunction
In conditions such as schizophrenia, it is hypothesized that disruptions in the accompanying referential copying mechanisms cause internally generated "voices" to appear external because the expected "self-labeling" is not accurately registered.
Source Monitoring and Higher-Order Cognition
Monitoring sources
At the cognitive level, "source monitoring" is the process by which we decide whether a memory or mental image came from an external event ("Did I see it happen?") or an internal compartment ("Did I imagine it?").
The prefrontal cortex (especially the dorsolateral prefrontal cortex) is essential for these higher-order judgments and executive functions.
Memories of real events often come with richer sensory details and context (where, when, with whom).
Imaginations or phantasies are usually less anchored in the same kinds of spatiotemporal and contextual details, although they can still be relatively vivid.
The brain uses these contextual associations—mainly related to the hippocampus and surrounding middle temporal lobe structures—to judge authenticity.
The reality testing
Higher cognitive processes (eg, reasoning, introspection) also help us check whether something makes sense in the context of external reality (eg, "I can't really fly; I must be dreaming or imagining").
Now let's put it all together:
The distinction between external and internal reality rests on multiple overlapping circuits and not on a single "reality module".
Sensory input arrives via bottom-up pathways, carrying reliable and reliable signals about external events.
Top-down processes (imagination, recall, mental imagery) can partially activate the same sensory areas but usually with different activation patterns and less "weight" than real external input.
Predictive processing helps match or mismatch sensory input with internal expectations, creating a sense of an external cause or self-generated internal event.
Corollary discharge / efference copy mechanisms provide an internal "tag" indicating that certain activities (motor, verbal, or imagination-based) are self-initiated.
Monitoring sources in higher order cognitive areas (frontal cortex, hippocampus) allows us to further assess whether an experience or memory has internal or external sources.
When all these systems work together in harmony, we usually have a clear sense of which experiences come from the outside world and which arise from within our consciousness.
Disruption in any of these processes – especially corollary discharge or source monitoring – can lead to experiences in which the boundaries between reality and imagination are blurred (as can be seen in various psychiatric or neurological conditions).
Key points:
A multi-layered process: the brain's distinction between internal and external reality is not handled by just one area; It involves a network of areas responsible for sensory integration, predictive modeling, collateral discharge, and executive control.
Prediction and context: Predictive coding frameworks, combined with contextual cues and source monitoring, are central to distinguishing imagination from real feeling.
Clinical Relevance: Understanding these mechanisms sheds light on disorders in which internal thoughts or hallucinations are mistakenly attributed to external reality (eg, schizophrenia, certain delusional disorders).
Ultimately, the brain's ability to distinguish between external reality and internal imagination is a sophisticated dance of bottom-up and top-down processes, finely tuned by prediction, error correction, and contextual awareness.
Brain networks involved in the process of distinguishing between internal "reality" and external reality
Default Mode Network (DMN)
Central nodes: middle prefrontal cortex, posterior cingulate gyrus (PCC), parcuneus, lateral parietal cortex, parts of middle temporal lobe (including hippocampus).
Role: active when the brain is focused on internal tasks – such as daydreaming, imagining and retrieving autobiographical memory.
Relation to distinguishing between mental and external worlds: the default mode network generates and manipulates internal images and narratives. Its interaction with executive and sensory networks can help label whether a thought is "just in my head" or related to external stimuli.
Salience network (SN)
Central nodes: anterior insula, dorsal ACC.
Function: Monitors internal and external environments in search of relevant cues ("salient" information) and helps shift brain focus between internal (default mode network) and external (attention/control) demands.
Connection to distinguishing between the inner and outer worlds: when a salient external stimulus appears, the SN helps divert processing resources outward; If a stimulus is labeled as an internally generated stimulus, the SN may down-prioritize an extrinsic orientation.
Central Executive Network (CEN) or frontoparietal network
Central nodes: dorsolateral prefrontal cortex, posterior parietal cortex.
Function: executive functions, working memory, attention control and decision making.
Connection to the distinction between mental and external world: helps preserve and update "working models" of reality, while integrating new sensory data and top-down expectations. It also mediates source monitoring (deciding where the information came from).
The cerebral nucleus of the thalamus (sensory relay)
The thalamus acts as a primary relay for sensory information on its way to the cerebral cortex.
It selectively checks which signals are passed on for higher-level processing, and plays a role in "filtering" or "highlighting" external inputs versus internally generated signals (feedback).
Disturbances in thalamocortical loops have been linked to hallucinations in psychiatric conditions, highlighting its role in perception of reality.
Now if you put it all together:
Sensory Input and Integration: Incoming signals are processed in the primary sensory cortex, then relayed to association areas for integration and association.
Predictive coding and top-down control: frontal and parietal regions make predictions about incoming stimuli; Mismatches (prediction errors) update the prediction or the interpretation of the stimulus (internal vs. external).
Colorally Discharge: Self-initiated thoughts or movements carry a peripheral copy to sensory areas, "labeling" them as internally generated.
Source monitoring and executive function: The prefrontal cortex, in conjunction with the hippocampus and middle temporal lobe, evaluates contextual information to decide whether a perception or memory is anchored in external reality or internal fabrication.
Collaboration of networks: The default state network, the salience network, and the central executive network interact dynamically—shifting the focus between internally generated content and external environmental demands.
When these systems are functioning normally, we navigate reality with a clear boundary between what comes from the outside world and what is created by ourselves.
Disruptions in any of these processes – whether as a result of psychiatric conditions (eg, schizophrenia), neurological damage, or other disorders – can lead to difficulties in accurately distinguishing between internal and external experiences.
What are the different pathologies that may be associated with this process
The distinction between the outside world and our inner experiences is essential to navigating reality in a meaningful and adaptive way. When these processes are functioning well, we can trust our perceptions to guide us in decision making, social interaction, and daily functioning. When they go wrong, this can lead to serious distortions in the way we interpret ourselves and the environment.
Below are some key reasons why this is important and examples of pathologies that arise when this mechanism is disrupted:
Accurate perception and survival
We rely on our senses to detect immediate threats (eg, a speeding car) or opportunities (eg, food, social cues). If we cannot distinguish between real danger and imagined fear, or between real nourishment and fantasy, our survival may be compromised.
Social and emotional functioning
Correctly evaluating other people's actions, expressions and intentions is essential to healthy relationships. Mistaking our internal dialogues or our predictions about someone else's words or intentions leads to confusion and conflict.
Learning and adaptation
Effective learning requires accurate feedback from the environment. If we confuse internal expectations with actual external results, we may fail to adapt appropriately – which will impair problem solving and personal growth.
A sense of agency and responsibility
Recognizing which actions and thoughts are "mine" (versus actions influenced by external factors) underlies our sense of responsibility for our behavior. If self-generated experiences are misattributed to the outside world, then this can distort the way we see ourselves and our moral/ethical actions.
Mental health and well-being
A stable boundary between internal imaginations and external facts is critical to mental health. This limit helps us examine reality, manage pressures and maintain coherence in our worldview.
Pathologies associated with impaired differentiation
When the brain mechanisms responsible for distinguishing between internal and external experiences go awry, a variety of psychiatric or neurological conditions can appear. Here are some notable examples:
Schizophrenia and psychotic disorders
Hallucinations: Patients may hear voices (auditory hallucinations) that feel completely external, even though these "voices" are generated internally.
Delusions: False beliefs may persist because the person misattributes their internal experiences (e.g., intrusive thoughts) as coming from an external source (e.g., "The TV is sending me secret messages").
Bipolar disorder (with psychotic features)
In severe mania with psychotic episodes, reality testing may be impaired. People may have grandiose delusions, mistaking inner fantasies (eg, "I'm a famous celebrity") for factual reality.
Major depressive disorder with psychotic features
In some severe depressive states, patients may develop delusions of guilt or hopelessness that they experience as unquestionably true, losing the ability to recognize these beliefs as "internal distortions."
Post Traumatic Stress Disorder (PTSD)
Traumatic memories can intrude vividly into the present, causing flashbacks that feel as real as the initial event. The boundary between an internal memory of the past and the current external reality blurs, evoking intense fear reactions.
Dissociative disorders
Conditions such as dissociative identity disorder (DID) involve splitting the sense of self and reality. Internal experiences may be perceived as belonging to a separate "personality," and reality testing may be inconsistent.
Delirium
Acute states of confusion (due to infections, drunkenness, metabolic imbalance, etc.) may severely impair reality testing. Patients may have visual illusions or hallucinations, misinterpretations, and disorganized thinking.
Dementia
In Alzheimer's disease or other dementias, reality monitoring deteriorates. Patients may suffer from confabulations – filling memory gaps with fabricated stories that they believe to be true, mixing past memories with present confusion.
Neurological conditions (eg, temporal lobe epilepsy)
Seizures in certain areas of the brain (especially temporal lobes) can create intense internal sensations (auras, deja vu, hallucinations) that feel real to the outside. This can lead to confusion about what is "really" happening.
Phantom limb syndrome
Although not usually a "psychiatric" condition, the persistent perception of a missing limb illustrates how the mind can create compelling sensory experiences that do not match external reality.
Psychosis caused by substances
Psychedelic substances (eg, LSD, psilocybin) can blur the line between imagination and reality, leading to visual or auditory hallucinations and an altered sense of self.
Stimulants (eg, amphetamines) and other drugs can cause paranoid thoughts through similar mechanisms.
Clinical and research implications
Early detection and treatment
Identifying early signs of deficits in reality testing (eg, subtle hallucinations, mild hallucinations) can help prevent or manage severe psychotic episodes.
Therapeutic interventions
Cognitive Behavioral Therapy (CBT): helps patients in certain situations develop metacognitive skills, improving source monitoring and reality checking.
Medication: Antipsychotics, mood stabilizers, or antidepressants can reduce the intensity of hallucinations or delusions depending on the type of mental disorder.
Neurobiological insights
Investigating how corollary referrals, source monitoring, and predictive coding are disrupted in these pathologies could possibly guide directions for new treatments.
Brain imaging and neurophysiological research are helping to identify specific dysfunctional circuits, which could potentially lead to targeted interventions.
Key points:
Why is this important? Accurate sorting of internal versus external events is essential for survival, social formation, learning and maintaining a coherent sense of self.
Pathologies: Conditions ranging from schizophrenia and bipolar disorder to dementia and delirium can include marked disruptions of reality discrimination, which can lead to hallucinations, delusions, or confusion about self-generated experiences.
Clinical Relevance: Improving our understanding of these brain mechanisms can lead to better diagnostic tools, early interventions, and targeted therapies that restore or support the brain's ability to differentiate between the external world and the internal imagination.
By the way, our ability to distinguish between external reality and internal experience can be significantly affected by different states of consciousness or changes in sensory input. Sleep, sensory deprivation, sleep deprivation, and excessive daydreaming can each alter the balance between external sensory information (bottom-up signals) and internal processes (top-down expectations, memories, and imaginings). When this balance shifts, the clarity of "what is real vs. what is imagined" may become more blurred.
Reduced sensory input
When we fall asleep, the brain's interaction with external sensory signals (such as sight, hearing, touch) is greatly reduced.
During REM sleep, inner imagination (dreams) can be vivid and emotionally salient. Because the external sensory input is low, the internally generated dream content can feel "real" while it is happening.
Brain networks and dreams
In REM sleep, areas such as the default mode network (DMN) and the limbic system (regions associated with emotion) remain active or even hyperactive, while some of the prefrontal "reality check" circuits are less active.
This change in activation patterns can reduce the normal checks that separate external reality from internal imagination.
Hypnagogic and hypnapompic hallucinations
Hypnogogic hallucinations occur when falling asleep (in the transition to sleep).
Hypnopompic hallucinations occur upon awakening (in the transition from sleep to wakefulness).
In both cases, states of partial arousal mixed with dream imagery can create brief but convincing hallucinations that reflect a blurred line between inner and outer reality.
Sensory deprivation
Absence of external cues
Under conditions of sensory deprivation (eg, prolonged isolation in a quiet, dark environment), the brain receives minimal stimulation from the outside world.
In the absence of predictable external input, the brain's predictive processes can increase reliance on internal imagery, filling the void with self-generated sensations or visions.
An image of a state of sensory deprivation of stimuli from the outside world [created with the help of [AI: when darkness falls, the visual stimuli of the world outside the room decrease, and then internal reflections from the inside room rise.
Sensory deprivation hallucinations
Hallucinations or vivid daydream-like experiences often occur during prolonged sensory deprivation. The brain actually "increases the input" of internal signals to compensate for the lack of external signals.
With few external anchors, it is more difficult to distinguish imagination or memories from real external events. A person may experience illusions or hallucinations that are mistaken for real sensory experiences.
Sleep deprivation
Cognitive and perceptual impairment
Chronic or severe sleep deprivation impairs executive functions in the prefrontal cortex, and reduces the brain's ability to monitor sources (decide whether a thought/image is external versus internal).
Fatigue also impairs attention, which is critical for distinguishing between real sensory cues and internal mental chatter.
Microsleep and dream intrusions
An extreme lack of sleep can lead to microsleep – short, involuntary breaks in wakefulness. At these moments, dreamy or hallucinatory images can enter the waking hours.
In a sleep-deprived state, people may experience hallucinations or mild psychotic symptoms (eg, hearing faint voices, seeing flashes at the edge of vision).
Emotional dysregulation
Sleep loss disrupts normal emotional regulation (involving the amygdala and frontal regions), and sometimes increases anxiety or even paranoia. This heightened emotional state can color perceptions, making internal concerns feel "real" to the outside.
Default Mode Network (DMN) Dominance
Daydreaming involves DMN activation, which supports mind wandering, internal narratives, and self-referential thought.
In typical, mild daydreaming, we switch back and forth between external focus (task-positive networks) and internal focus (DMN). When daydreaming is excessive, inner focus can dominate.
Maladaptive daydreaming is a proposed condition in which people spend much of their time in complex and immersive fantasy worlds, at the expense of daily functioning.
In extreme cases, the boundaries between these imaginary scenarios and real events can become blurred, causing confusion and impairment of social or occupational functioning.
With excessive daydreaming, opportunities to validate experiences against real-world evidence are reduced. The boundary between imagination and external reality can weaken, especially if a person is prone to fantasy or lacks strong cognitive "checks".
If you put it all together:
Sleep (especially REM): suppresses external inputs while increasing internal images, and naturally blurs the boundaries between imagination and reality (dreams).
Sensory Deprivation: Lack of input pushes the brain to produce its own stimuli, increasing susceptibility to hallucinations or misinterpretation of internal sensations.
Sleep deprivation: damages prefrontal and attentional processes, and increases the likelihood of hallucinations, distortions and difficulty distinguishing between internal and external.
Excessive daydreaming: Sustained inward focus can reduce habitual reality checks, making inner fantasies feel more real.
All of these conditions have a common thread: they disrupt the normal balance of bottom-up (external) and top-down (internal) processing that underlies the perception of reality.
The brain receives insufficient external signals (sleep, sensory deprivation) or is too tired/distracted to process them properly (sleep deprivation), or it devotes so much energy to internal narratives (excessive daydreaming) that it neglects external reference points.
As a result, the usual markers that help us "label" experiences as either self-generated or external sources become less reliable, and we are more prone to confusion—or in some cases, hallucinations—about what is "out there" versus "in our head."
We will now move on and discuss whether executive memory and long-term memory are related to the distinction between the external reality and the internal world in the context of distinguishing between external reality (the outside world) and internally generated thoughts, imagination, or memories, both executive (working) memory and long-term memory play crucial but distinct roles.
While the terminology can vary (as some researchers use "working memory" and "short-term memory" interchangeably) "executive memory" may refer to a broader set of executive functions related to memory.
The basic idea is that these two memory systems [executive (working) memory and long-term memory] cooperate to help us keep track of current reality, remember past experiences accurately, and correctly label events as "internal" versus "external."
Here is an overview of how each system contributes to such a distinction:
Executive (working) memory
Executive memory or working memory generally refers to the ability to hold information and process it for short periods of time (seconds to minutes).
It is closely related to executive functions in the prefrontal cortex, especially the dorsolateral prefrontal cortex (DLPFC).
Working memory also involves the frontal network, which coordinates attention, goal-directed behavior, and cognitive control.
Its effect on distinguishing reality
Online contact tracking
Working memory helps maintain the context of what is happening in the present moment.
Tracking external cues, goals, and relevant sensory data, it provides an internal "snapshot" of reality that can be compared against new input.
Monitoring sources
Executive functions help in "source monitoring", that is, checking whether a piece of information or mental image came from direct sensory experience (the outside world) or from one's imagination/memory.
Working memory temporarily contains the details (time, place, sensory attributes) needed to decide whether the experience was truly external or self-generated.
Inhibitory control
Part of executive function is the ability to inhibit irrelevant internal thoughts or intrusive memories.
Good inhibitory control makes it less likely that internally generated images or ideas will be perceived as real, because the brain can suppress them or properly "label" them as internal before they cause confusion.
Identifying and correcting errors
The prefrontal cortex can detect discrepancies between expectations (top-down) and incoming sensory feedback (bottom-up).
The working memory holds the prediction and the incoming data side by side, allowing the system to update or reject incorrect interpretations.
Long term memory
Long-term memory (LTM) involves storing information for extended periods of time – from hours to a lifetime.
Key structures include the hippocampus (for creating and retrieving episodic memories), other structures of the middle temporal lobe, and distributed areas of the cerebral cortex where memories are consolidated.
How does this memory affect reality testing
Contextual details (episodic memory)
Episodic memories store where, when, and how events occurred.
When retrieving memories, the brain restores associations (location, people present, emotional tone). If these contextual details are rich and well organized, they are easier to identify as memories of real events. In the case of weak or confused contextual cues, the memory may feel more like an imagined event—or vice versa.
Such reality monitoring is a process of assessing whether a particular memory is based on actual perception or inner thought.
The hippocampus and frontal regions cooperate: the hippocampus provides detailed memories, while the prefrontal cortex evaluates plausibility, consistency, and sensory details.
Schemes and models for prediction
Long-term memory stores schemas – mental models of how the world usually works. These schemas help the brain predict what it might encounter and guide interpretation of ambiguous stimuli.
Accurate schemas can help distinguish real external events from unrealistic or implausible internal imaginings ("I can't really fly in real life, so it must have been a dream or a fantasy").
When long-term memory encoding or retrieval is impaired (for example, in amnesia, dementia or under considerable mental stress), it can lead to confabulations (fabricated memories that the person believes to be real).
These confabulations show how malfunctions in LTM processes can blur the line between actual external events and internally constructed "false" memories.
Integration: How working memory and long-term memory work together
feedback loops
When a person recalls a memory (from LTM), it becomes temporarily active in working memory. During this "reconsolidation" process, executive functions assess the memory's consistency and origin.
If the memory aligns with external data or personal context, it is reinforced; If it conflicts, it may be updated or deleted.
Moment-to-moment reality checking relies on working memory that holds current sensory cues and attentional focus.
Long-term memory provides a background of learned regularities, context, and past experiences to interpret and label current perceptions.
Error correction
If a person experiences an internal image (e.g., a strong mental image of a conversation) and working memory "matches" it with knowledge from long-term memory (e.g., "I've never had that conversation"), the discrepancy can help label the image as imagined rather than real.
Clinical relevance
Schizophrenia and psychotic disorders: Disorders in the prefrontal cortex may impair working memory and executive control, and contribute to hallucinations. Poor monitoring of sources means that internally generated voices or thoughts are misattributed to external reality.
Dementia and amnestic disorders: Damage to the hippocampus or other structures of the middle temporal lobe impairs the contextual labeling of long-term memory, leading to confusion between real versus imagined events.
Anxiety and PTSD: Strong emotional memories stored in LTM can interfere with working memory (eg, flashbacks), creating vivid internal experiences that feel very real.
Normal aging: A slight decline in working memory and source monitoring can make older adults more prone to confusion about whether they "really did something" or just thought about doing it.
Key points:
Working (executive) memory
Maintains immediate connection, regulates attention and enables reality checks on the go.
Provides the cognitive control and inhibition mechanisms necessary to keep internal imaginings separate from real external receiver.
Stores the contextual details and conventions that help us label experiences as real or imagined (based on consistency with past events and learned knowledge).
When memory encoding or retrieval is impaired, perception of reality may be impaired, leading to confusion, false memories, or difficulty recognizing hallucinations as such.
Cooperation between these memory subtypes
These two systems work in parallel: working memory actively compares incoming (or recalled) information with knowledge established in long-term memory, and continuously labels experiences as "internal" or "external".
Effective reality discrimination depends on healthy functioning of both systems, functioning guided by the prefrontal cortex, hippocampus, and supporting brain networks.
By keeping accurate and up-to-date information in working memory and referring to well-organized long-term memory, the brain can better decide whether a particular feeling, thought, or memory stems from the external world or our internal imagination.
The data therefore indicate that proper discrimination in reality results from interrelationships of the sensory cortex, frontal-parietal executive networks, memory structures in the hippocampus, and special labeling processes (eg, associated discharge).
Disruptions in each of these areas contribute to a sequence of phenomena from delusions to psychosis in the full sense of the word.
Clinical interventions targeting these mechanisms show promise in early detection and rehabilitation, thereby increasing our ability to treat disorders characterized by deficits in reality monitoring.
Below are the articles of authors who dealt with the subject:
Helmholtz, H. (1867)
Pioneering work on visual perception and the concept of "unconscious inference", laying foundations for modern predictive coding theories.
Holst, A., von Mittelstadt, H. (1950)
A preliminary description of the rereference principle (also called corollary discharge or efference copy), which explains how the nervous system differentiates between self-stimulation and external stimuli.
A classic text establishing the foundations of experimental psychology; Includes early investigations of introspection, perception, and the distinction between external stimuli and mental processes.
Johnson, M. K. and Ray, K. to. (1981)
A groundbreaking paper introducing the source monitoring framework, which details how people distinguish between memories of real events and internally generated experiences.
An influencing paper on episodic memory ("mental time travel") and the phenomenological aspects of retrieving real versus imagined experiences.
Rao, R. P. N. and Ballard, D. H. (1999)
Fundamental study of the modeling of the visual cortex as a prediction system, which greatly influences contemporary theories of perception and discrimination in reality.
The paper suggests that the brain minimizes "free energy" by constantly updating internal models, the key to understanding how we predict and interpret external versus internal cues.
Ford, J. M., & Mathalon, D. H. (2005).
The article reviews evidence that defective discharge mechanisms may underlie auditory hallucinations, a prime example of the failure to differentiate between self-generated and external sounds.
Fletcher, P. about. and Ferit, c. d. (2009)
Integrates Bayesian/predictive coding models with schizophrenia research, and clarifies how delusions/hallucinations can result from maladaptive weighting of prior beliefs versus sensory evidence.
Powers, A. R., Mati, c. and Corlett, P. R. (2017)
Empirical research showing how manipulation of expectations (priorities) can induce hallucination-like experiences in healthy participants, supporting models of predictive processing.
Bentel, R. P. (1990)
A comprehensive review discussing the cognitive mechanisms underlying hallucinations, with an emphasis on monitoring sources and schema-based distortions.
Jardri, R., Duverne, S., Denève, S., & Frith, C. (2017)
The paper explores how abnormal prediction error signaling can cause hallucinations, and offers alternative views on whether it is over- or underestimation of errors that leads to "misperceptions".
Shadlen, M. N., & Newsome, W. T. (1998)
The article analyzes the variation in neural responses and the implications for understanding how the cerebral cortex processes and interprets incoming information, relevant to discrimination in reality.
Northoff, G., & Bermpohl, F. (2004)
The paper investigates how midline cortical regions (middle prefrontal cortex, anterior cingulate) are involved in self-referential processing, which is key to attributing internal versus external sources.
Reichel, M. A., McLeod, A. M., Snyder, A. Z., Powers, W.J., Gosnard, D. A. and Shulman, JL. (2001)
A seminal paper describing the default default network (DMN), which exhibits increased activity during internally focused thinking (daydreaming, mind wandering) and has critical implications for reality monitoring.
Below are the detailed citatations of the authors mentioned above:
1. Helmholtz, H. (1867): Handbuch der Physiologischen Optik (Vol. 9): L. Voss
2. Holst, E. von, & Mittelstaedt, H. (1950): Das Reafferenzprinzip: Naturwissenschaften, 37(20), 464–476.
3. Wundt, W. (1902): Principles of Physiological Psychology (2nd ed.): Macmillan.
4. Johnson, M. K., & Raye, C. L. (1981): Reality monitoring: Psychological Review, 88(1), 67–85.
5. Tulving, E. (1985): Memory and consciousnessl: Canadian Psychology, 26(1), 1–12.
6. Rao, R. P. N., & Ballard, D. H. (1999): Predictive coding in the visual cortex: A functional interpretation of some extra-classical receptive-field effects: Nature Neuroscience, 2(1), 79–87.
7. Friston, K. (2010): The free-energy principle: A unified brain theory?: Nature Reviews Neuroscience, 11(2), 127–138.
8. Ford, J. M., & Mathalon, D. H. (2005): Corollary discharge dysfunction in schizophrenia: Can it explain auditory hallucinations?: International Journal of Psychophysiology, 58(2–3), 179–189.
9. Fletcher, P. C., & Frith, C. D. (2009): Perceiving is believing: A Bayesian approach to explaining the positive symptoms of schizophrenia: Nature Reviews Neuroscience, 10(1), 48–58.
10. Powers, A. R., Mathys, C., & Corlett, P. R. (2017): Pavlovian conditioning–induced hallucinations result from overweighting of perceptual priors: Science, 357(6351), 596–600.
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The distinction between the external and internal world in reference to the model we develop for the Self
The main question in this article is: How does the human mind (or "the self", in the language of the model) succeed in distinguishing between the inputs and contents that originate in the outside world ("outside reality") and those contents and inner feelings ("inner reality") that are actually imagination, memory, fantasy, or any other mental component that does not come from the senses?
Reference to the three core brain components (Emotional Salience Network;
Executive Network; Default Network Mode)
and to the groups of the Social Self (the internalized board of characters, the internalized group of enemies, and the group of self-representations), to demonstrate how the diagnosis between inside and outside is formed [see conversations about the model in the previous conversations of this blog]
Figure: The model for the self that we propose
Biological framework: the Primary Self (Biological Predetermined Core)
The primary self in the model includes innate biological systems – instincts, primary emotional abilities and basic cognitive abilities. This self constitutes the biological "playground" through which we perceive the world:
The human brain perceives reality through sensory systems (sight, hearing, touch, smell, taste, as well as proprioceptive "inner sense" of the body).
From this primary biological self, the building blocks begin to form in interaction with the environment for further information processing and organization.
Basic emotions:
The primary self includes innate emotional response systems (fear, disgust, pleasure, sadness, and more).
Apart of this, we postulate the existence of so called SENSITIVITY CHANNELS that are activated as soon as the brain detects a specific potentially significant stimulus (threat, routine disruption, etc.).
Basic cognitive abilities:
Already in infancy, nuclei for memory, generalization and coding of experiences begin to form, even if they are very primitive and emotional in the beginning.
The primary self, then, is probably the "ground" that first distinguishes between "external stimulation" that comes from the world, and "internal stimulation" that results from physical, emotional or mental reactions. But this is still a partial distinction, since babies – and even adults – sometimes have difficulty distinguishing between imagination and reality.
The secondary (social) self as an information organizer of internal characters in dialogue with the real characters.
The model presents three superstructures [directory of internalized characters, the internalized group of enemies, the group of self-representations] that develop from nuclei in the primary self and gradually create a kind of "mediation" between their internalized content [internalized characters] and their origins (real figures) in the external world:
Board of Internalized Characters:
A database of internalized representations of significant figures from the environment (parents, teachers, friends, literary/historical "heroes" and more).
It has a hierarchy: internal "leaders" versus secondary, less significant characters.
AI-assisted illustration : the board of the internalized figures
Internalized Enemy Group:
This is a collection of internal figures that threaten the person, differing from the figures on the board in that they are not "completely" assimilated as a source of identification or inspiration, but "fenced" in a separate area, to protect the self from them.
A collection of self-representations:
The way a person represents himself throughout his life (child, teenager, adult, "future me", etc.). These self-representations exist simultaneously and sometimes in competition (for example, a person who still carries a "childish" part within him).
These three structures conduct an "internal dialogue" between themselves [mainly between the directorate of the internalized figures and the ego representations] but also with the figures in the outside world whose representations are internalized in them. In addition, they are affected by an important set of networks that develops in the primary self in a model called:
The Experience Coordinating Agency that is actually a brain-psychic mechanism that observes what is happening in the inner world and at the same time perceives what is happening outside of it. This "triple array" model consists of three central brain circuits mentioned above:
A network responsible for identifying "what is important and what is urgent" in the external environment or the internal world and directs attention there.
Thus, when we encounter an "unclear" stimulus, the salience network is activated to check whether it is a real external thing or an internal emotion and directs the attention there.
2. Executive Network
The network of executive functions (attention, working with short-term memory, motor organization, suppression of unnecessary automatic reactions).
Allows the brain to check reality in a critical way ("Was what I just saw really light in the room, or was it just imagination?").
It uses tools of logic, thinking, searching for evidence in reality, etc.
3. Default Mode Network
Activated mainly in a state of internal thinking, daydreaming, mind wandering, self-referential processing.
Strongly related to the ability to imagine different scenarios, bring up memories, develop fantasies – that is, a rich inner world.
One of the prevailing theses in neuroscience today is that in order for a person to be able to separate "what comes from the world" from "what comes from within", there is a need for a balanced regulation between the three aforementioned networks.
When the Emotion Salience is too sensitive, the person may interpret any external or internal feeling as something powerful and even as something "external and threatening" (for example, in schizophrenia it is sometimes difficult to distinguish between an internal voice and a voice that really comes from the outside).
When the Default Mode Network is very active without good control of the Executive Network, the person may "immerse" in imagination or hallucinations and fail to draw realistic conclusions.
When the Executive Network is weak, it is difficult to perform a consistent "reality check", and internal illusions or fears may be accepted as facts about the world.
The coordination mechanism (Experience Coordinating Agency) is built as mentioned above from these three networks, checks again and again whether the given stimulus stems from an external or internal factor, and sometimes is also helped (or in some cases hindered) by the groups of "internalized characters" and their positions and/or information that accumulates about "how the real world works".
How does this brain model actually distinguish between reality and imagination?
A. Signs from the world received from the senses versus internal signs
Adjusting the sensory data:
The brain "crosses" information from several sensory channels (sight, hearing, touch). If several of them indicate the same phenomenon, the likelihood that it is an external stimulus increases.
For example, hearing a voice and also seeing its source increases confidence that it is an external reality (and not an internal voice).
Difference in the feeling of control:
A feeling of "Am I in control of what's happening?" Sometimes it helps to differentiate between an external event (out of my control) and an internal thought (“my product”).
B. A reality check based on comparison to "past memories" and internalized characters.
For example, using the "directorate of internalized figures" and other representations:
A person learns throughout his life "what is logical behavior" and "what is realistic" through the internalization of characters, their attitudes and characteristics.
When a stimulus appears that does not match the knowledge base (for example, a miraculous figure that the person has never seen and the environment does not know), the Executive Network marks this stimulus as suspicious.
It is possible that the Experience Coordinating Agency is trying to consult the "inner knowledge" of the internalized characters. This is how an internal dialogue was created: "Have we ever seen anything like this? Did the parents/teachers/friends say such a thing existed? Does this correspond to the 'laws of nature' that we internalized from the environment?"
If there is no match between the experience and the internalized knowledge, the person tends to classify it as "imaginary" or "unrealistic".
C. Metacognitive control ("view of ourselves")
1. Executive Network operates "reality testing" control processes like asking: "Is this stimulus rational that can be measured/tested?", "Does anyone else notice it?"
If so, they tend to see it as a real external stimulus. If not, it is defined as an internal stimulus, dream, imagination, waking memory, etc.
C. Internalized Leader and reality testing.
In our model the internalized leader plays a crucial role in forming the person’s view towards others and the world as a whole. If the attitudes of the internalized leader are maladaptive, the reality testing might be compromised. For example, a leader self of the “emotional dictator” type will be often influenced by the prevailing emotion and not by the facts.
Emotion as a measure
A strong emotion may convince a person that the thing is external ("I'm so scared, it must be real!").
But when the Executive Network works well, he checks and notices: "The fear is indeed strong, but there is no evidence of this in reality, it may just be an internal trigger."
Pathology and the loss of the ability to distinguish between inside and outside
In various pathological conditions, the balance between the networks is disturbed:
Very high sensitivity in the Salience Network: may cause internal stimuli (thoughts, anxieties) to be interpreted as if they come from the outside (voices, illusions).
• Executive Network is not developed or weak: logic and the ability to perform Reality Testing are compromised, and thus more imaginary content "enters" the definition of "reality".
• Default Mode Network is overactive: the person may immerse himself in fantasies, intense memories or flashbacks, and interpret them as present.
Summary of the main ideas:
The distinction between "outside" and "inside" requires integration between:
Sensory data and their mutual compatibility (what is really absorbed by the senses?)
An internal system of knowledge, memories and social representations (what do I know from the past? What do I expect?)
Cognitive control ability (Executive Network) that activates a reality check mechanism.
Balanced emotional complexity (Emotion Salience Network) that is not overly overwhelming.
Introspection is well managed (Default Mode Network) so that the imaginary content remains "marked" as such.
In addition, the more the person is able to integrate these brain networks and conduct an internal dialogue between them and the "directorate of internalized characters", the "internalized group of enemies" and the "representations of the self", the clearer a distinction will be made between what really comes from the external senses and what comes from memory, emotion or imagination internal.
When these control processes (mainly the Experience Coordinating Agency) are compromised – due to trauma, mental disorders, or extreme hypersensitivity in sensitivity channels such as the threat channel – a blurring of boundaries between internal and external may appear. Then we see states of hallucinations (hearing internal voices as "external"), misinterpretation of reality, or alternatively acute indifference to real stimuli.
In the psychological-neurological reality, the distinction between "inside" and "outside" is a complex and multidimensional product. The model we have presented here offers an "architectural" framework in which the board of internalized characters, the internalized group of enemies, and the self-representations develop from the initial biological wiring (primary self) where the dialogue between "inside" and "outside" is supervised by three key networks in the brain.
Thus, the way we "know" that something comes from the outside world and not from the imagination, lies in the brain's integrative ability to connect objective sensory data with cognitive reality checking mechanisms while maintaining a balanced emotional regulation.
That's it for now,
yours,
Dr. Igor Salganik and Prof. Joseph Levine
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