From Learning to Memory: A Comparison Between Verbal and Non-verbal Skills in 22q11.2 Deletion Syndrome

Verbal narrative ability and episodic autobiographical memory in adolescents and young adults with 22q11.2 deletion syndrome

BACKGROUND

Poor episodic autobiographical future thinking has recently been reported in 22q11.2 carriers. However, whether these impairments are due to poor language skills or indicate a true episodic autobiographical memory deficit remains unclear. Language impairments are the hallmark of the neuropsychological profile of young children with 22q11DS, but language outcomes in adolescence and young adulthood, especially high-level linguistic skills such as narrative, remain largely unexplored. The aims of this study are first to precisely characterize the narrative abilities of a group of adolescents and young adults with a 22q11DS and normal verbal intellectual functioning, in comparison to a control group. Second, to assess their (past) autobiographical episodic memory and their future episodic thinking abilities. Third, to examine the relationship between linguistic and autobiographical memory skills.

METHODS

Fifteen adolescents and young adults with 22q11DS were compared with 15 age- and sex-matched controls. Narrative ability was assessed with a storytelling task and included microstructural, macrostructural, and pragmatic linguistic measures. Episodic autobiographical memory was assessed using a paradigm involving recall of past personal memories and future thinking conditions.

RESULTS

Adolescents and young adults with 22q11DS still struggled with high-level language skills such as storytelling tasks, and all linguistic levels were impaired, i.e., the microstructural, macrostructural, and pragmatic components of narrative. Second, 22q11DS carriers showed poor episodic autobiographical recall of their personal memories and reduced access to sensory details (visual, auditory…) compared to controls. Their poor autobiographical episodic memory skills were independent of language impairment, and there were no effects of age or intellectual level on their autobiographical (past) memories recollection. On the other hand, age and verbal intellectual functioning significantly contributed to their ability to produce episodic narratives in the future thinking condition, suggesting that the future thinking task relies on more complex and intricate factors than pure episodic memory ability.

CONCLUSIONS

Verbal narrative impairments did not account for poor recall of personal memories, suggesting dysfunctional episodic memory networks between hippocampi and posterior cortical areas in 22q11DS, where neuroanatomical and neurofunctional alterations have indeed been reported.

Using transcranial alternating current stimulation to enhance working memory skills in youths with 22q11.2 deletion syndrome: A randomized double-blind sham-controlled study

Abnormal cognitive development, particularly working memory (WM) deficits, is among the first apparent manifestations of psychosis. Yet, cognitive impairment only shows limited response to current pharmacological treatment. Alternative interventions to target cognition are highly needed in individuals at high risk for psychosis, like carriers of 22q11.2 deletion syndrome (22q11.2DS). Here we applied theta-tuned transcranial alternating current stimulation (tACS) between frontal and temporal regions during a visual WM task in 34 deletion carriers. We conducted a double-blind sham-controlled study over three consecutive days. The stimulation parameters were derived from individual structural MRI scan and HD-EEG data acquired at baseline (Day 1) to model current intensity and individual preferential theta peak. Participants were randomized to either sham or tACS (Days 2 and 3) and then completed a visual WM task and a control task. Our findings reveal that tACS was safe and well-tolerated among participants. We found a significantly increased accuracy in the visual WM but not the control task following tACS. Moreover, this enhancement in WM accuracy was greater after tACS than during tACS, indicating stronger offline effects than online effects. Our study therefore supports the application of repeated sessions of brain stimulation in 22q11.2DS.

Thalamic contributions to psychosis susceptibility: Evidence from co-activation patterns accounting for intra-seed spatial variability (μCAPs)

The temporal variability of the thalamus in functional networks may provide valuable insights into the pathophysiology of schizophrenia. To address the complexity of the role of the thalamic nuclei in psychosis, we introduced micro-co-activation patterns (μCAPs) and employed this method on the human genetic model of schizophrenia 22q11.2 deletion syndrome (22q11.2DS). Participants underwent resting-state functional MRI and a data-driven iterative process resulting in the identification of six whole-brain μCAPs with specific activity patterns within the thalamus. Unlike conventional methods, μCAPs extract dynamic spatial patterns that reveal partially overlapping and non-mutually exclusive functional subparts. Thus, the μCAPs method detects finer foci of activity within the initial seed region, retaining valuable and clinically relevant temporal and spatial information. We found that a μCAP showing co-activation of the mediodorsal thalamus with brain-wide cortical regions was expressed significantly less frequently in patients with 22q11.2DS, and its occurrence negatively correlated with the severity of positive psychotic symptoms. Additionally, activity within the auditory-visual cortex and their respective geniculate nuclei was expressed in two different μCAPs. One of these auditory-visual μCAPs co-activated with salience areas, while the other co-activated with the default mode network (DMN). A significant shift of occurrence from the salience+visuo-auditory-thalamus to the DMN + visuo-auditory-thalamus μCAP was observed in patients with 22q11.2DS. Thus, our findings support existing research on the gatekeeping role of the thalamus for sensory information in the pathophysiology of psychosis and revisit the evidence of geniculate nuclei hyperconnectivity with the audio-visual cortex in 22q11.2DS in the context of dynamic functional connectivity, seen here as the specific hyper-occurrence of these circuits with the task-negative brain networks.

Altered developmental trajectories of verbal learning skills in 22q11.2DS: associations with hippocampal development and psychosis

BACKGROUND

The cognitive profile in 22q11.2 deletion syndrome (22q11.2DS) is often characterized by a discrepancy between nonverbal vs. verbal reasoning skills, in favor of the latter skills. This dissociation has also been observed in memory, with verbal learning skills described as a relative strength. Yet the development of these skills is still to be investigated. We thus aimed to explore verbal learning longitudinally. Furthermore, we explored verbal learning and its respective associations with hippocampal alterations and psychosis, which remain largely unknown despite their high prevalence in 22q11.2DS.

METHODS

In total, 332 individuals (173 with 22q11.2DS) aged 5-30 years completed a verbal-paired associates task. Mixed-models regression analyses were conducted to explore developmental trajectories with threefold objectives. First, verbal learning and retention trajectories were compared between 22q11.2DS vs. HC. Second, we examined hippocampal volume development in 22q11.2DS participants with lower vs. higher verbal learning performance. Third, we explored verbal learning trajectories in 22q11.2DS participants with vs. without positive psychotic symptoms and with vs. without a psychotic spectrum disorder (PSD).

RESULTS

Our findings first reveal lower verbal learning performance in 22q11.2DS, with a developmental plateau emerging from adolescence. Second, participants with lower verbal learning scores displayed a reduced left hippocampal tail volume. Third, participants with PSD showed a deterioration of verbal learning performance, independently of verbal reasoning skills.

CONCLUSION

Our study challenges the current view of preserved verbal learning skills in 22q11.2DS and highlights associations with specific hippocampal alterations. We further identify verbal learning as a novel cognitive marker for psychosis in 22q11.2DS.