Toddlers Learn Better When Experiences are Predictable

What's the science?

There are many benefits to predictable learning. For example, when something is predictable there is time to build expectations and better understand when those expectations have been violated. In toddlers, there is mixed evidence for the benefits of both predictable and unpredictable learning. It is still unclear which method of learning is ideal for toddlers during development. Recently in Current Biology, Benitez and colleagues test whether toddlers learn words better in predictable versus unpredictable situations.

How did they do it?

Toddlers were presented with a series of boxes that would open in a sequence to reveal a series of objects. The timing and location of box opening was predictable (always clockwise), however, the object to be revealed was unknown. This sequence exposure experiment was repeated 5 times. Then, a second labelling experiment was performed, where boxes would open either in the predictable sequence or in an unpredictable (i.e. an unexpected box would open that was different from the previously learned sequence) pattern to reveal an image paired with a recorded voice announcing what the object was. The authors used an eye tracking system to track how the toddlers attended to the objects and to rule out potential confounding effects of visual attention. They then tested, in a learning phase, whether the toddlers retained object-label pairs better for predictable vs. unpredictable events. They tested this using a “looking-while-listening” method where the object-label pair was presented and they were to look to the correct object.

What did they find?

Reaction times were greater for unpredictable events than predictable events in both the object revealing and labelling experiments suggesting that toddlers were tracking the sequence of events. They also demonstrated anticipatory looks towards a box where an object was about to be revealed meaning the toddlers developed expectations about the sequence of events. Toddlers were found to look at the correct object-label pair for a greater proportion of time than the incorrect object for the predictable events compared to the unpredictable events. Toddlers were also more accurate at looking to the object-label pair during predictable events.

What's the impact?

This is the first study to show that predictable events support word learning in toddlers. We now know that toddlers may learn better when new information is presented in a predictable way. Understanding how children learn during development is important for understanding developmental outcomes.

Benitez et al., Predictable events enhance word learning in toddlers. Current Biology (2018). Access the original scientific publication here.

Oxytocin Affects Social Sharing and Brain Activity in Women

What's the science?

Social interaction and relationships are rewarding; however, attachment anxiety can reduce rewarding effects of social interaction. Oxytocin is a neuropeptide released from the hypothalamus, known to facilitate social bonding and reduce anxiety. It is unknown how oxytocin may affect the experience of social interaction and anxiety differently in men and women. Furthermore, it isn’t known how brain activity may be altered in the presence of oxytocin in men and women. This week in NeuroImage, Ma and colleagues test the sex-differential effects of oxytocin on social sharing and associated brain activity.

How did they do it?

128 pairs of same-sex friends were randomized into two groups and given a placebo (as a control) or a dose of intranasal oxytocin (as a treatment; group allocation was blinded). Before the experiment participants filled in a) a friendship scale to ensure a high quality of friendship and b) questionnaires that controlled for mood and personality differences between the test groups. Attachment style was assessed using the Adult Attachment Scale. After administration of the placebo or oxytocin, the friends participated in a social sharing experiment where they shared emotional experiences with either their good friend or a stranger (same sex). The pairs performed the same task, and one person was in the MRI scanner (task-based functional MRI scan) while the other person was in an experimental room close by.

They were instructed that they would view an image either alone, with their friend or with a stranger. Then participants were shown images of people, landscapes or animals that were either neutral, positive or negative. After each picture they were asked to rate how positive or negative the image made them feel and how strong their feeling was. They were also asked to report on thoughts related to sharing with their friends after the sharing experiment. The fMRI data was acquired to measure effects on brain activity and functional connectivity and differences between men and women.

What did they find?

Oxytocin increased the positive experience of sharing, particularly for positive emotional content, in female but not male participants. Effects were most pronounced when sharing with female friends but not with strangers. For males, there was no effect of oxytocin on sharing between friends, however, it did increase positive emotion in the stranger > alone condition (i.e. viewing an image with a stranger vs. viewing it alone). Oxytocin generally increased thoughts of sharing with friends when undergoing the sharing with a friend condition. On the neural level the effects of oxytocin in females were accompanied by reduced activity in the amygdala and insula as well as decreased interplay between them, whereas the opposite pattern was observed in males. Moreover, oxytocin reduced the strength of the correlation between attachment anxiety and amygdala activity in females during social sharing with a friend, indicating that the effects of oxytocin may vary with attachment style.

What's the impact?

This is the first study to demonstrate effects of oxytocin on social sharing and which effects differ between men and women. We now know that oxytocin increases the positive experience of sharing with a friend in females but not in males and that brain activity during sharing is differentially affected in females vs. males. Furthermore, the effects of oxytocin on brain activity may differ depending on attachment anxiety. Future research should consider sex-differences when studying the behavioral and brain effects of oxytocin on anxiety, stress and social attachment. For the proposed therapeutic administration of oxytocin in disorders such as autism, sex-differences in responses may need particularly to be taken into account.

Ma et al., Sex- and context-dependent effects of oxytocin on social sharing. NeuroImage (2018). Access the original scientific publication here.

Treatment Response Is Associated with Altered Inflammation Pathways in Depression

What's the science?

Major depressive disorder (MDD) has previously been associated with various markers of inflammation in the body. For example, some studies have shown that cytokines (proteins secreted by the immune system that can be either pro- or anti-inflammatory) are elevated in the blood and cerebral spinal fluid of individuals with the disorder. Elevated levels of anti-inflammatory cytokines in MDD have also been found; the body may increase production of these cytokines to reduce inflammation. However, a reliable biomarker for MDD or associated inflammation has not been established. This may be due in part to the fact that most studies have focused on MDD patients who were not treatment naïve, therefore, a clear link between MDD, inflammation, and treatment could not be established. This week in Neuron, Syed and colleagues studied inflammation in individuals with MDD who were treatment-naïve.

How did they do it?

171 treatment-naïve patients diagnosed with MDD and 64 healthy individuals (as part of the PReDICT cohort) were included in the study. The patients and healthy controls were not matched on certain demographic criteria (age, sex, body max index and ethnicity), so some analyses included only a subset of matched patients and controls (62 patients and 62 healthy control participants referred to as ‘matched sub-groups’). However, results from the 62 patients were not statistically different from the results from the entire group of 171 patients in most analyses, so the larger group of patients was used (‘total sample’). 29 cytokines, chemokines, or growth factor measures (all inflammatory/immune markers) were collected from blood samples. Patients were randomized to receive 12 weeks of duloxetine or escitalopram treatment (antidepressants) or 16 sessions of cognitive behavioural therapy treatment. The authors examined the effects of time (pre- or post-treatment), group, and treatment response on inflammatory markers.

What did they find?

When the authors compared cytokine levels between healthy controls and the total sample of patients, they found that 6/7 pro-inflammatory cytokine levels and 5/7 anti-inflammatory cytokine levels were elevated in patients with MDD compared to healthy controls (2/7 were diminished). The results indicate abnormal inflammatory regulation in treatment-naïve patients with MDD. Some chemokine and growth factor levels were also elevated, however, some were not elevated when the smaller matched subgroups were compared, indicating the differences in these levels may be due to demographic factors. Inflammasomes (multiprotein complexes that can trigger inflammatory cascades/cytokines upstream) were also elevated in patients with MDD, further suggesting that inflammatory responses are altered in patients with MDD. The authors also applied plasma to peripheral blood mononuclear cells from healthy individuals and found that CD69+CD19+ cells, were reduced, suggesting a reduction in activated B cells (immune cells). The authors next tested whether cytokine levels changed in treatment responders versus non-responders (pooled across treatments). Several pro-inflammatory cytokine levels were reduced following treatment in responders (versus non-responders, in which levels tended to rise). Anti-inflammatory cytokine levels tended to rise over time regardless of treatment response. Memory T cells (immune cells) were also lower in responders versus non-responders, suggesting lower immune memory in responders.

What's the impact?

This is the first comprehensive study of inflammatory markers in treatment-naïve patients with MDD. The results suggest inflammatory dysregulation is common in MDD, and differs by response to treatment. The results have important implication for understanding the effect of MDD on inflammation and the role of treatment in altering the immune response in MDD.

Syed et al., Defective Inflammatory Pathways in Never-Treated Depressed Patients Are Associated with Poor Treatment Response. Neuron (2018). Access the original scientific publication here.