Aversive learning strengthens episodic memory in both adolescents and adults

Reward-motivated memories influence new learning across development

Previously rewarding experiences can influence choices in new situations. Past work has demonstrated that existing reward associations can either help or hinder future behaviors and that there is substantial individual variability in the transfer of value across contexts. Developmental changes in reward sensitivity may also modulate the impact of prior reward associations on later goal-directed behavior. The current study aimed to characterize how reward associations formed in the past affected learning in the present from childhood to adulthood. Participants completed a reinforcement learning paradigm using high- and low-reward stimuli from a task completed 24 h earlier, as well as novel stimuli, as choice options. We found that prior high-reward associations impeded learning across all ages. We then assessed how individual differences in the prioritization of high- versus low-reward associations in memory impacted new learning. Greater high-reward memory prioritization was associated with worse learning performance for previously high-reward relative to low-reward stimuli across age. Adolescents also showed impeded early learning regardless of individual differences in high-reward memory prioritization. Detrimental effects of previous reward on choice behavior did not persist beyond learning. These findings indicate that prior reward associations proactively interfere with future learning from childhood to adulthood and that individual differences in reward-related memory prioritization influence new learning across age.

Developmental change in prefrontal cortex recruitment supports the emergence of value-guided memory

Prioritizing memory for valuable information can promote adaptive behavior across the lifespan, but it is unclear how the neurocognitive mechanisms that enable the selective acquisition of useful knowledge develop. Here, using a novel task coupled with functional magnetic resonance imaging, we examined how children, adolescents, and adults (N = 90) learn from experience what information is likely to be rewarding, and modulate encoding and retrieval processes accordingly. We found that the ability to use learned value signals to selectively enhance memory for useful information strengthened throughout childhood and into adolescence. Encoding and retrieval of high- vs. low-value information was associated with increased activation in striatal and prefrontal regions implicated in value processing and cognitive control. Age-related increases in value-based lateral prefrontal cortex modulation mediated the relation between age and memory selectivity. Our findings demonstrate that developmental increases in the strategic engagement of the prefrontal cortex support the emergence of adaptive memory.

Role of a Heat Shock Transcription Factor and the Major Heat Shock Protein Hsp70 in Memory Formation and Neuroprotection

Heat shock proteins (Hsps) represent the most evolutionarily ancient, conserved, and universal system for protecting cells and the whole body from various types of stress. Among Hsps, the group of proteins with a molecular weight of 70 kDa (Hsp70) plays a particularly important role. These proteins are molecular chaperones that restore the native conformation of partially denatured proteins after exposure to proteotoxic forms of stress and are critical for the folding and intracellular trafficking of de novo synthesized proteins under normal conditions. Hsp70s are expressed at high levels in the central nervous system (CNS) of various animals and protect neurons from various types of stress, including heat shock, hypoxia, and toxins. Numerous molecular and behavioral studies have indicated that Hsp70s expressed in the CNS are important for memory formation. These proteins contribute to the folding and transport of synaptic proteins, modulate signaling cascades associated with synaptic activation, and participate in mechanisms of neurotransmitter release. In addition, HSF1, a transcription factor that is activated under stress conditions and mediates Hsps transcription, is also involved in the transcription of genes encoding many synaptic proteins, whose levels are increased in neurons under stress and during memory formation. Thus, stress activates the molecular mechanisms of memory formation, thereby allowing animals to better remember and later avoid potentially dangerous stimuli. Finally, Hsp70 has significant protective potential in neurodegenerative diseases. Increasing the level of endogenous Hsp70 synthesis or injecting exogenous Hsp70 reduces neurodegeneration, stimulates neurogenesis, and restores memory in animal models of ischemia and Alzheimer’s disease. These findings allow us to consider recombinant Hsp70 and/or Hsp70 pharmacological inducers as potential drugs for use in the treatment of ischemic injury and neurodegenerative disorders.

Neutral Sphingomyelinase is an Affective Valence-Dependent Regulator of Learning and Memory

Sphingolipids and enzymes of the sphingolipid rheostat determine synaptic appearance and signaling in the brain, but sphingolipid contribution to normal behavioral plasticity is little understood. Here we asked how the sphingolipid rheostat contributes to learning and memory of various dimensions. We investigated the role of these lipids in the mechanisms of two different types of memory, such as appetitively and aversively motivated memory, which are considered to be mediated by different neural mechanisms. We found an association between superior performance in short- and long-term appetitively motivated learning and regionally enhanced neutral sphingomyelinase (NSM) activity. An opposite interaction was observed in an aversively motivated task. A valence-dissociating role of NSM in learning was confirmed in mice with genetically reduced NSM activity. This role may be mediated by the NSM control of N-methyl-d-aspartate receptor subunit expression. In a translational approach, we confirmed a positive association of serum NSM activity with long-term appetitively motivated memory in nonhuman primates and in healthy humans. Altogether, these data suggest a new sphingolipid mechanism of de-novo learning and memory, which is based on NSM activity.

Odor Canopy: A Method for Comfortable Odorant Delivery in MRI

Functional magnetic resonance imaging (fMRI) has become the leading method for measuring the human brain response to sensory stimuli. However, olfaction fMRI lags behind vision and audition fMRI for 2 primary reasons: First, the olfactory brain areas are particularly susceptible to imaging artifacts, and second, the olfactory stimulus is particularly difficult to control in the fMRI environment. A component of the latter is related to the odorant delivery human–machine interface, namely the point where odorants exit the dispensing apparatus to reach at the nose. Previous approaches relied on either nasal cannulas or nasal masks, each associated with particular drawbacks and discomforts. Here, we provide detailed descriptions and instructions for transforming the MRI head-coil into an olfactory microenvironment, or odor canopy, where odorants can be switched on and off in less than 150 ms without cannula or mask. In a proof-of-concept experiment, we demonstrate that odor canopy provides for clearly dissociable odorant presence and absence, with no nonolfactory cues. Moreover, we find that odor canopy is rated more comfortable than nasal mask, and we demonstrate that using odor canopy in the fMRI generates a typical olfactory brain response. We conclude in recommending this approach for minimized discomfort in fMRI of olfaction.