Exploration of a novel virtual environment improves memory consolidation in ADHD

The study investigates whether a post-encoding novel experience can enhance long-term memory consolidation in children and adolescents with ADHD, who commonly exhibit deficits in attention, working memory, and episodic memory, especially in free recall. Behavioral tagging theory posits a sensitive window after encoding during which salient events (e.g., novelty) can stabilize weak memory traces via synaptic tagging and capture of plasticity-related proteins, mediated by dopaminergic and noradrenergic systems. Animal work shows novelty enhances memory when presented within 30–60 minutes around learning. Human studies suggest novelty can aid memory, but often used elaborate real-world experiences or incidental learning. This study tests a translational approach using active exploration of a novel virtual environment, presented 45 minutes after intentional word-list learning, to target consolidation specifically. The hypothesis was that novelty would improve 24-hour free recall in both ADHD and typically developing (TD) youth, with additional exploration of individual differences in immersion, exploration behavior, and novelty seeking as potential moderators.

Background literature establishes: (1) ADHD involves impairments in working and episodic memory, affecting both encoding and consolidation; (2) Behavioral tagging and synaptic tagging-and-capture (STC) frameworks explain how weakly tagged synapses can capture plasticity-related proteins (PRPs) produced by a subsequent salient event, stabilizing long-term memory; (3) Animal studies show exploration of a novel environment enhances unrelated memory within a critical peri-encoding window and depends on dopaminergic/noradrenergic modulation; (4) Human school-based studies found that unrelated novel lessons can improve delayed recall when presented 1 hour before or after encoding, indicating a ~30–60 minute window. Prior human work with virtual environments suggests active exploration and immersion may modulate benefits, but methodologies varied (e.g., timing relative to encoding, intentional vs incidental learning, VR vs desktop), and stronger initial encoding may reduce novelty benefits. This study situates itself to test behavioral tagging in ADHD with controlled novelty via Minecraft-based environments and focuses on free recall, where ADHD deficits are pronounced.

Design: Three-day laboratory study. Day 1: Familiarization with one of two Minecraft-built virtual environments ("mansion" or "island"). Day 2: Intentional learning of 20 common disyllabic German words (two presentations, 5 s per word with 1.5 s fixation; read aloud), immediate free recall (STM). After a 45-minute break (no phones; toys allowed), participants explored either the already familiar environment (familiar condition) or the alternate, novel environment (novel condition), with free navigation (first-person, WASD only; other keys disabled; environmental sounds on; time set to 6 a.m. for consistency). Exploration targeted 10–20 minutes; player position logged every 100 ms via Raspberry Jam Mod to quantify exploration (unique 2×2 block tiles visited). Subjective measures: novelty seeking (JTCI exploratory excitability subscale) during the break and immersion (IPQ-based items) after exploration. Day 3: Delayed free recall (LTM) and a recognition memory test (reported in Supplement). All tasks ran on a Dell Inspiron 17 7779 laptop (17.3”, 60 Hz); learning/recognition via Presentation (v20.1). Participants: Initially 72 youth aged 9–15 years. Diagnostic assessment (K-SADS-PL) ensured 34 met DSM-5 ADHD criteria (24 combined, 9 inattentive, 1 hyperactive-impulsive); 7 had comorbid ODD. Exclusions: psychiatric comorbidities (beyond ODD/CD/enuresis) in ADHD group; any psychiatric history in TD; neurological disorders/substance abuse; IQ < 80. Additional measures: CBCL, YSR, DISYPS-III, IQ (CFT 20-R), attention (d2-R; TAP alertness), inhibitory control (TAP Go/No-Go), episodic memory (VLMT), handedness (Edinburgh). Stimulant medication withheld ≥24 h prior and through study; 4 participants excluded for technical or compliance issues, leaving N=68. Groups: TD-familiar (n=17), TD-novel (n=17), ADHD-familiar (n=17), ADHD-novel (n=17). Allocation to novelty vs familiar on Day 2 was pseudo-random and matched on STM performance to equate baseline encoding. Outcomes and measures: Primary outcome was memory consolidation measured as retention score = (LTM free recall hits / STM free recall hits) × 100 (percent retained over 24 h). Control variables: novelty seeking (JTCI exploratory excitability T-scores), immersion (IPQ-based raw scores), and exploration (count of unique tiles visited; computed per environment divided into 2×2-block tiles). Prior gaming/Minecraft familiarity collected. Statistical analysis: Bayesian linear modeling for retention with predictors diagnosis (ADHD vs TD), novelty (familiar vs novel), and interaction (diagnosis × novelty). Priors: intercept Student-t(df=3, μ=50, σ=30); sigma half-Student-t(df=3, μ=0, σ=10); flat uniform priors for coefficients. Posterior group contrasts computed and evaluated with 95% Highest Density Intervals (HDIs) and a Region of Practical Equivalence (ROPE) set to [-5, 5] retention percentage points (reflecting ≥1-word difference). Significance criterion: ≥95% of posterior mass outside ROPE. Control variable differences analyzed via two-way ANOVAs (diagnosis × novelty). Additional Bayesian models assessed effects of exploration, immersion, and novelty seeking (each z-scored) on retention with full interactions (e.g., retention ~ exploration × diagnosis × novelty), same priors and ROPE. MCMC: 4 chains × 2000 samples, 1000 warm-up; R̂=1. Analyses in R 3.6 with brms and bayestestR; code/data available on GitHub.

- Memory consolidation deficits in ADHD under familiar conditions: ADHD-familiar retained on average b = -23.23 percentage points fewer words than TD-familiar; 95% HDI [-33.18, -13.70]; 99.97% of posterior outside ROPE, indicating a significant deficit. - Novelty benefits ADHD: Within ADHD, novelty improved retention by b = +15.67 points relative to familiar; 95% HDI [6.03, 25.77]; 98.27% outside ROPE, significant. - No significant novelty benefit in TD: TD-novel vs TD-familiar b = -4.16; 95% HDI [-13.69, 6.49]; 48.70% outside ROPE (not significant). - ADHD vs TD under novel conditions: ADHD-novel vs TD-novel b = -3.39; 95% HDI [-13.53, 6.94]; 43.57% outside ROPE (not significant), indicating novelty alleviated the ADHD consolidation deficit. - Group characteristics (Table 1): Groups were matched on age and sex; TD groups had higher IQ (CFT 20-R) than ADHD groups; VLMT showed typical ADHD weaknesses. Gaming experience and Minecraft familiarity were similar across groups. - Control variables (ANOVAs): • Novelty seeking (exploratory excitability) higher in ADHD (main effect of diagnosis), F(1)=6.42, p=0.014, η²=0.09; no novelty or interaction effects. • Immersion higher in ADHD (main effect of diagnosis), F(1)=5.53, p=0.022, η²=0.08; no novelty or interaction effects. • Exploration (tiles visited) greater in novel than familiar environments (main effect of novelty), F(1)=7.68, p=0.007, η²=0.11; no diagnosis or interaction effects. - Effects of immersion/exploration/novelty seeking on retention (Bayesian): • Novelty seeking: no significant effects in any group (HDIs overlapped ROPE). • Immersion: In TD-novel, higher immersion associated with worse retention, b ≈ -9.21; 95% HDI [-14.21, -3.22]; 93.57% outside ROPE (trend-level by stated criterion). No significant effects in ADHD-familiar, ADHD-novel, or TD-familiar. • Exploration: In TD-novel, higher exploration associated with worse retention, b = -14.35; 95% HDI [-22.09, -6.43]; 98.92% outside ROPE (significant). Effect differed from ADHD-novel (difference b₁ = -14.40; 95% HDI [-25.04, -3.10]; 95.47% probability different). No significant effects in other groups. - Visualization indicated more space explored in novel vs familiar environments; immersion/exploration did not harm ADHD groups but were detrimental in TD under novel conditions.

The findings support the hypothesis that a post-encoding novel experience can enhance long-term memory consolidation in children and adolescents with ADHD. Presenting a novel virtual environment 45 minutes after learning improved 24-hour free recall, consistent with behavioral tagging and STC mechanisms whereby novelty-induced neuromodulation supplies PRPs to stabilize weakly encoded traces. The lack of benefit in TD children suggests novelty primarily enhances weakly encoded memories; in familiar conditions, ADHD participants exhibited poorer retention than TD, implying weaker initial encoding likely due to attentional and dopaminergic differences. Novelty may increase tonic activity in VTA/SN, boosting hippocampal dopamine and PRP synthesis, preferentially aiding ADHD where baseline encoding is suboptimal. Contrary to some prior human studies, TD participants did not benefit, which may reflect methodological differences: intentional learning and an immediate recall test likely strengthened encoding (and induced a testing effect) in TD, reducing room for novelty-driven consolidation gains. Behavioral tagging effects may thus depend on initial encoding strength and task demands. Additionally, higher immersion and greater exploration were associated with poorer retention in TD under novel conditions, possibly due to interference from forming rich memories of the novel environment that compete with the word list. This effect did not appear in ADHD, suggesting either reduced susceptibility to interference in consolidation or differences in strategic encoding of the environment. Overall, novelty-based behavioral tagging appears particularly promising for populations with weaker initial encoding, such as ADHD, while in strongly encoded contexts or with high environmental engagement, novelty may not confer benefits and could even interfere in TD.

This study demonstrates that exploring a novel virtual environment 45 minutes after learning improves next-day free recall in children and adolescents with ADHD, effectively reducing their consolidation deficit relative to typically developing peers. No benefit was observed in TD participants, supporting the view that behavioral tagging preferentially strengthens weakly encoded information. Moreover, in TD under novel conditions, greater immersion and exploration related to poorer retention, suggesting potential interference between environmental and list memories. These results position virtual-environment-based behavioral tagging as a promising, scalable intervention to support memory in ADHD. Future research should: (1) delineate the boundaries of effectiveness with respect to encoding strength, task intentionality, and testing effects; (2) examine timing parameters around encoding; (3) assess memory for the environment to directly test interference; (4) test delivery modalities (e.g., VR vs desktop) and volitional vs guided exploration; and (5) explore neurobiological correlates (e.g., dopaminergic markers) and clinical translation in school settings.

- Sample size was modest (n=68 analyzed), though Bayesian methods with informative priors were used to mitigate small-sample limitations. - Group assignment to novelty vs familiar was pseudo-random and matched based on STM performance rather than fully randomized, potentially introducing allocation bias. - The intentional learning paradigm and inclusion of an immediate recall test may have strengthened encoding (and induced testing effects), particularly in TD participants, potentially masking novelty benefits in this group. - Virtual environments were presented on a laptop (not immersive VR), and immersion was self-reported; modality could influence effects and generalizability. - The study primarily focused on free recall retention; recognition results are in the Supplement. No direct measures of memory for the environments were collected, limiting tests of interference hypotheses. - No neurobiological measures were obtained to directly link dopaminergic/neuromodulatory mechanisms to behavioral effects.